Not seeking medical advice, and already looked up the wikipedia article on scars but it seems outdated. I was captivated by this story on the Extra-Cellular Matrix and how it helped regrow a man's finger with-out scar tissue.
Not seeking medical advice, and already looked up the wikipedia article on scars but it seems outdated. I was captivated by this story on the Extra-Cellular Matrix and how it helped regrow a man's finger with-out scar tissue.
I have three scars-one from a dog bite, one from a burn, and one from a knife slash.
I was wondering if they will ever be removable...
Thanks. <span style="font-size: smaller;" class="autosigned">—Preceding [[Wikipedia:Signatures|unsigned]] comment added by [[Special:Contributions/98.85.15.164|98.85.15.164]] ([[User talk:98.85.15.164|talk]]) 01:05, 14 August 2010 (UTC)</span><!-- Template:UnsignedIP --> <!--Autosigned by SineBot-->
Thanks. <span style="font-size: smaller;" class="autosigned">—Preceding [[Wikipedia:Signatures|unsigned]] comment added by [[Special:Contributions/98.85.15.164|98.85.15.164]] ([[User talk:98.85.15.164|talk]]) 01:05, 14 August 2010 (UTC)</span><!-- Template:UnsignedIP --> <!--Autosigned by SineBot-->
Revision as of 04:39, 14 August 2010
Welcome to the science section of the Wikipedia reference desk.
The best answers address the question directly, and back up facts with wikilinks and links to sources. Do not edit others' comments and do not give any medical or legal advice.
How come there is no volcanoes in the North Pole? When was the last time that a continent sat on the north pole?--68.116.113.157 (talk) 00:41, 8 August 2010 (UTC)[reply]
There are lots of places with no volcanoes. There is nothing special about the North Pole in that respect, so I don't see why there needs to be a reason. This map from the late Jurassic period (so about 150 million years ago) shows land very close to, if not actually at, the pole (it's hard to tell from the image). That seems to be the most recent time there was any land near the pole. You can see the recent (last half a billion years or so) changes in the placements of continents in this animation: File:TectonicReconstructionGlobal.gif. --Tango (talk) 00:59, 8 August 2010 (UTC)[reply]
Are you sure? I was going to say the same but then I came across File:Plates tect2 en.svg...a line goes off the top of the map and comes down the other side. Which suggests to me it passes pretty close to the North Pole. I realise flat maps can't properly illustrate a spherical(ish) globe, but... Vimescarrot (talk) 16:18, 8 August 2010 (UTC)[reply]
That map doesn't actually show the north pole. The north pole on that projection is a horizontal line infinitely far above the map, if I'm recognising the projection correctly. There is no way to know what that plate does north of the boundary of the map just by looking at that map. There is a whole chunk of the plate missing. --Tango (talk) 16:55, 8 August 2010 (UTC)[reply]
The source page says "Mollewide projections show the entire globe in one view, but are distorted significantly along the margins of the globe". Looie496 (talk) 17:50, 8 August 2010 (UTC)[reply]
You misunderstand. The map Vimes links to doesn't show the North Pole. The map I embedded certainly does, otherwise my answer wouldn't have made any sense. --Tango (talk) 17:54, 8 August 2010 (UTC)[reply]
On the other hand, there are plenty of Arctic volcanoes, especially in Iceland. ~AH1(TCU) 18:31, 8 August 2010 (UTC)[reply]
Do we have any images of the major plates superimposed on a more modern projection, or something that preserves the curve a little better? (I'm also surprised by how weird it is to see a map like this centred over the Americas, but I don't think it would be reasonable to ask for one that matches my own expectations) Is Vimes's link a Mercator projection? The British Isles looks huge on it, and Africa very small. 82.24.248.137 (talk) 19:32, 8 August 2010 (UTC)[reply]
The boundary between the North American and Eurasian plates actually passes very close to the north pole, but it's difficult to find a picture that shows this properly. However I haven't seen anything that indicates volcanic activity at that part of the junction. Looie496 (talk) 20:03, 8 August 2010 (UTC)[reply]
You want the Gakkel Ridge, which passes pretty close to the pole and is an active (if extremely slow) spreading center - that article also has a useful image. Mikenorton (talk) 07:19, 10 August 2010 (UTC)[reply]
The Neurons or the synapses
Does it improve a person's memory or intelligence to have many neurons or is it in the synapses or the way that the neurons send the signals that is responsible for why some people have better memories than others? I believe Kim Peek (Rain man inspiration) was said to not have the corpus callosum, and it is in theory that some believe because of this his brain found a way of connecting around that at a superfast speed and that is what is responsible for his memory. Also, can the neurons or the way signals are sent be changed, I ask because I watched this documentary that had a guy from Enland who after an epilectic seizure when he was three he started to get this incredible memory and brilliance for numbers and on the same documentary there was a kid who got hit in the head with a baseball as a kid and ever since that he too had an afinnity to memorize dates and so on? —Preceding unsigned comment added by 70.136.158.173 (talk) 01:12, 8 August 2010 (UTC)[reply]
Also, could the size or shape of the brain have anything to do with it? (In the MRI taken of a woman who has memorized every day of her life from 1980 on and others like her there bains were slightly different shape and they were all left-handed.)
Most neuroscientists believe that memory is stored by changing the strength of synapses, so the total number of synapses sets a limit on the amount of memory the brain can store. But this is only one factor: an effective memory depends on a whole range of systems for formatting, storing, and recalling memories. It's like in a computer memory is stored in little magnetic things, but if you just throw a pile of magnetic things on the floor, you don't get a usable memory system -- it all has to be organized properly.
It is very common for autistic savants to have extraordinary memory for details. Most don't have a missing corpus callosum, so I doubt that that has anything important to do with it. The stuff about signals connecting around at superfast speed is just nonsense. Basically we don't know where those extraordinary memories come from -- it clearly involves a higher level of brain organization than we yet understand. Changes in brain shape might be relevant, or they might not -- we just don't know yet. Looie496 (talk) 02:26, 8 August 2010 (UTC)[reply]
The hippocampus definitely does something uncertain to do with memory. Experienced taxi drivers (who can remember complicated maps) have enlarged ones, as the article mentions. 81.131.58.136 (talk) 02:56, 8 August 2010 (UTC)[reply]
Are the parts and even the strength of the synapses continually growing? Like for example our bones even though we stop growing and reach our full height our bones are still constantly rebuilding themselves and continue to go through a process? —Preceding unsigned comment added by 71.156.2.13 (talk) 03:52, 8 August 2010 (UTC)[reply]
There is quite a bit of evidence that synapses change continuously. A synapse is only a single signal channel, so they don't get more complicated over time, but they do get stronger or weaker. Among other things, Giulio Tononi's theory of sleep proposes that synapses steadily strengthen over the course of each day, and then weaken when we are asleep -- there is substantial evidence to support this. Looie496 (talk) 04:52, 8 August 2010 (UTC)[reply]
Does chemical/hormones have anything to do with the strength or weakness of the synapse and or the neurons for that matter? —Preceding unsigned comment added by 71.137.245.165 (talk) 12:48, 8 August 2010 (UTC)[reply]
Absolutely. In fact, nearly every psychoactive drug exerts its effects by making some group of synapses either more or less effective. There are a small number, such as caffeine, that act on neurons by non-synaptic mechanisms, but the great majority act on synapses. There are also internal chemicals, such as norepinephrine, that act at least partly by modifying the strength of synapses in specific brain pathways. Looie496 (talk) 17:42, 8 August 2010 (UTC)[reply]
The thing is that our brains definitely have a finite capacity - it's probably comparable to the size of the hard drive in your computer. But memories aren't (usually) stored with perfect fidelity. I can recall my wedding day from 25 years ago - but I have almost zero memory of anything that anyone said to me on that day - other than a few snatches of the speech my father gave at the reception. Because the brain has finite capacity - and we didn't evolve to live to be 100 years old - we must eventually be forgetting things at about the same rate that we learn them.
But we don't do that by totally forgetting one entire year of our lives for every year we live. Our more distant memories become fuzzier - and less important things get erased in order to keep a choice few of the most important. It's as if we're continually summarizing less important (typically, older) information in order to make room for new, sharper memories. I think it's clear that the more amazing the savant's abilities are, the more mentally crippled they seem in other regards. Those who are able to memorize (by rote) unbelievable amounts of raw data - may well have damaged the part of the brain that is responsible for summarizing and discarding trivia. The brain has a spectacular storage capacity - it's not at all surprising that one could memorize a million digits of PI or a thousand books - but perhaps these people are losing information that the rest of us would find essential to daily life? It's hard to know because if such a person is incapable of (for example) managing interpersonal relationships or (maybe) holding down a job - we can't easily tell if that's because they are unable to remember some important class of data that relates to those more normal activities. SteveBaker (talk) 01:21, 10 August 2010 (UTC)[reply]
What tends to happen is that people with extraordinary event memory have difficulty generalizing -- they know all the facts but can't spot the patterns in them, can't see the forest for the trees if you will. Thus for most tasks they actually do less well than people with poorer memory. One of the nicest descriptions of the phenomenon is in Alexander Luria's classic The Mind of a Mnemonist. Looie496 (talk) 23:02, 10 August 2010 (UTC)[reply]
When is a heat sink necessary for a 7805 voltage regulator?
Hello! I'm a (newbie) hobby electrician. I'm planning on using an AC adapter that outputs 9V 210mA connected to a 7805 voltage regulator for my project. How do I know if a significant amount of energy will be wasted as heat? The circuit will be in operation mostly 24/7. When is a heatsink connected to the regulator required? The circuit will be working at room temperature. I think part of the difficulty I'm having understanding how the voltage regulator will work is because I've only worked with DC from batteries, and learned that when 9V is connected with a 1KΩ resistor in series to an ammeter, the reading will be 9mA, but I don't know why the AC adapter's specs show 9V at 210 mA. I would think (probably wrongly) that 9V would output 9A because of the ammeter example I gave. I'd also appreciate any help on understanding this now that I'm moving on from working with AA batteries. Thank you!--el Aprel (facta-facienda) 02:21, 8 August 2010 (UTC)[reply]
The regulator will reduce the voltage by varying its resistance. The current flowing through times the voltage drop will turn into heat. The AC adapter rating is just the maximum, so you have to know how much current your circuit will consume, If it only takes 10mA then no heat sink will be needed, but the full 200mA dropped by several volts, will need one. Graeme Bartlett (talk) 03:15, 8 August 2010 (UTC)[reply]
At risk of straying into wikibooks/wikiversity territory, you need the output voltage of the bridge rectifier. This will be the RMS of the step-down transformer you are using. Then take (Vin - Vout) / Iout. This will give the power drop across the voltage regulator. The voltage regulator's datasheet will give a maximum operating temperature. Say it is 70°C, this is fairly typical. Given a room temperature of around 30°C (a bit on the high side), the voltage regulator can not be more than 40°C above ambient. Say the transformer is at 12V AC. RMS is 17V DC. The drop across a 9V regulator is 8V (check the maximum input voltage, but they are normally around 50V). 8V * 210mA is 1.68W. That is 0.04W/°C or 25°C/W, assuming the heatsink is in free air. In enclosed cases you need a bigger heatsink (higher value for W/°C, smaller for °C/W), if you are using fan-cooling then a smaller heat sink is needed. CS Miller (talk) 11:04, 8 August 2010 (UTC)[reply]
You haven't mentioned the current draw of the load for the 7805. Once you know the load current, the rest is quite straightforward. As Csmiller hinted above, small unregulated wall-wart power supplies have very poor load regulation, that is, their output voltage at no-load can be more than twice their rated output voltage (i.e., example, 20V at 0 mA, 15V at 20 mA, but 9V at 210 mA). In this example, if the load draws 20mA, the 7805 will sink (15V - 5V)*20mA = 200mW, (9V-5V)*210mA = 840mW, etc. Alternatively, you can just use an off-the-shelf regulated wall-wart. If it's output is not clean enough, add passive RC filters.East of Borschov 18:12, 9 August 2010 (UTC)[reply]
I think you mean "If its output has too much ripple,...", and adding a passive RC filter will reduce the voltage to below the nominal regulated value i.e. Vout = Vreg - R Iout. Cuddlyable3 (talk) 19:48, 12 August 2010 (UTC)[reply]
Omniscience is impossible. For instance, the uncertainty principle states that we can not simultaneously know an elementary particle's position and momentum. So what is the maximum level of knowledge that can be attained, and is there any realistic measure of attaining it?--220.253.219.83 (talk) 04:24, 8 August 2010 (UTC)[reply]
The maximum knowledge that can be obtained is the amount of knowledge that our brains are capable of holding. That's an infinitesimal fraction of the information in the universe, so it doesn't really make sense to talk about obtaining it. The information in a teaspoon of water is vastly beyond our ability to comprehend. Looie496 (talk) 05:04, 8 August 2010 (UTC)[reply]
I think you may be misunderstanding the uncertainty principle. We often say things like "we can not simultaneously know", but that is misleading. The correct understanding is that particles do not ever have both a fixed position and momentum. It's not a statement about our lack of knowledge. It is an expression that trying to assign momentum and position to everything is inherently futile because those properties do not exist. A hypothetical omniscient deity could know everything there is to know, and still wouldn't know both position and momentum, because the universe simply doesn't allow particles to ever have well-defined values for both. Personally, I don't see any objections in quantum mechanics to a deity having omniscient knowledge of the present and past. However, the principle of wavefunction collapse (as presently understood within our limited knowledge) would seem to imply that even a deity would never be able to uniquely predict what would happen in the future, since quantum mechanics inherently involves randomness. Dragons flight (talk) 05:26, 8 August 2010 (UTC)[reply]
Unless the deity is the source of the randomness. You are assuming a deity that lives in the universe, but the deity could be the universe. i.e. the deity is to the universe as you are to a thought in your mind. Meaning each and every particle and interaction in the universe is specifically "animated" by the thoughts of the deity. Ariel. (talk) 07:59, 8 August 2010 (UTC)[reply]
No. All of those are the same as saying quantum mechanics is wrong, because the events would no longer be truly random. You can either say the universe isn't random (because the deity guides it, etc), or you can say the universe is random and future outcomes aren't known till they occur, but you can't have it both ways. Of course, a deity could certainly make a predestined universe appear random to beyond our ability to ever tell the difference, but that's not the same as saying the universe actually is random. Dragons flight (talk) 08:19, 8 August 2010 (UTC)[reply]
What's the difference? From a physics point of view I mean, not a philosophical one. If it's random beyond our ability to tell the difference, if there is no physical test or ability to tell otherwise, then it is random. The Equivalence principle works exactly the same way: Since there is no way to tell the two forces apart, they are the same. Ariel. (talk) 08:30, 8 August 2010 (UTC)[reply]
Information (not exactly the same as knowledge, but close enough) is strongly tied to energy. It takes energy to manipulate and store information. See Limits to computation and google for "Ultimate physical limits to computation" for more exact numbers. Another limitation is the speed of light - you can not know about anything not within your light cone. Additionally as you store more information the size of your "brain" gets larger - eventually it gets large enough that it takes a long time (because of the speed of light) to retrieve information from the other "side" of it. This greatly limits the speed at which you can think. (So you can know a lot, but not be able to think fast, or know less and think faster.) There is no direct answer to your question since you did not specify what is doing the "knowing", but maybe what I wrote was interesting anyway. Ariel. (talk) 07:59, 8 August 2010 (UTC)[reply]
Infinite knowledge may or may not be impossible, as infinite knowledge of information would be impossible, but knowledge is distinct from information. There are also ways that ordinary people use to increase knowledge to much higher levels (ie. mysticalself-hypnoticmind-expandingintrospectivespiritual experience), but not in a way that true omniscience could be achieved at any given point in time. The electron conundrum is likely connected to the quantum zeno effect. Knowledge cannot be quantified, and therefore may have little to do with the possible interconnections between neurons and synapses (~∞). As for the deity as universe argument, this is called pantheism. Also, it would be possible for an omnipotent being to create a door he cannot open. All the being has to do is make the door so that it is impossible to open at a specific time, but make it able to be opened when he decides it can. ~AH1(TCU) 18:14, 8 August 2010 (UTC)[reply]
Even forgetting quantum theory and uncertainty and things like the speed of light limitations on information transfer - this is a tricky problem. Ultimately, you need N bits of storage to store N bits of information. If the smallest imaginable item of information (let's say the spin on a particular fundamental particle) could be stored in the most compact way imaginable (which would probably be using the spin of a remarkably similar fundamental particle!) then the very best you could possibly do would be to store all of the information about half of the universe using the other half of the universe to store it!
That is a crazy upper-limit - gathering and maintaining the information would require machinery comprising some very large fraction of the universe! Also, history is a part of knowledge. If you used 90% of the stuff of the universe to store information about the other 10% then you'd only be able to store that information for 9 instants in time...which is a pretty crappy kind of history! It is a little tricky though - you might argue that you could store half of the information about the universe onto the other half - then you'd now know everything about 100% of the universe because the two halves are now identical. You might also argue (classically) that if you know everything possible about some chunk of universe at some particular instant in time - then you could extrapolate forwards and backwards in time to know the state at some arbitary time in the past or future. Aside from the quantum and chaos theory issues with that - there is now another problem. The half of the universe that you're storing the information on is affecting the half that it's trying to store...that means that the progress of your extrapolation calculations will affect the future in such a manner as to make your extrapolations incorrect.
We could also get into annoying philosophical arguments about what it actually means to "know" something. For example, we know the equation for calculating PI to an arbitary number of digits. Does that mean that we "know" what all the digits of PI are? Well, maybe...I don't know the 30th digit of PI - but I could probably find it out soon enough to be useful - so it's not much of a stretch to say that I "know" it. But suppose I wanted the googol'th digit? That might take my computer a billion years to calculate it...I don't think anyone would claim that they know what that digit is. If (as in the hypothetical case of using one half of the universe to store the information about the other half) my computer cannot retrieve the information faster than I can go out and measure it again - is there even any point in storing it. If I want to know the albedo of the 3rd moon of the 4th planet orbiting alpha centauri - but that information happens to be stored in a part of my computer that's 100 light years away - then it's easier to send out a probe a few light years and measure the albedo than it is to ask the computer to fetch the information for me. Do we "know" something if the cost to retrieve that knowledge takes longer than collecting the knowledge itself?
This is an interesting question to think about - but you're definitely not going to get a single good answer!
Do the fins of a tetra fish grow back? My wife and I have a 150 gallon aquarium filled with all kinds of tetra fish,and the other day we noticed that one of the smaller fishes front fins were nibbled on and the fish is flapping constantly.We seperated the fish from the pack and we were wondering if the fishes fins will ever grow back? If so how long? —Preceding unsigned comment added by 173.105.146.216 (talk) 10:04, 8 August 2010 (UTC)[reply]
Added new section header Rojomoke (talk) 10:27, 8 August 2010 (UTC)[reply]
Generally the consensus seems to be yes they will grow back. [1]87.102.23.179 (talk) 11:48, 8 August 2010 (UTC)[reply]
Yes, they grow back; they could not reach the same size as the original fins. 82.59.69.48 (talk) 13:13, 8 August 2010 (UTC)[reply]
SOx cooling atmosphere
This recent article at Ars Technica mentions [2] (from a report it covered) : ..result of a stronger cooling effect from sulfate aerosols.. (I'm not particularily interested in the article or conclusions/methodology)
I was wondering if any figures were available on the cooling effect of 'sulphate aerosols' - ie what magnitude of effect has/will have Flue-gas desulfurization had/will have on the worlds temperature, particularily the isolated effect of not adding sulphur to the atmosphere - not the overall balance taking into account burning coal. Thanks.87.102.23.179 (talk) 11:46, 8 August 2010 (UTC)[reply]
Are you wondering if it might be better to leave in the sulfur in order to cause global cooling? It's not worth it. The acid rain is far worse, To get rid of CO2 we need those plants, and acid rain kills them. Ariel. (talk) 05:18, 9 August 2010 (UTC)[reply]
A few weeks ago the paper-edition New Scientist had an article claiming that the last few decades' efforts to reduce the UK's sulphate emissions to lessen the acid rain impact on Scandinavia had (i) had little impact on the acidity, because most of it (82%?) comes from Scandinavia itself, the North Sea or other parts of continental Europe, and (ii) had resulted in a measurable increase (0.8C?) in the UK's average temperature due to the lessening of the aerosols' cooling effect. Unfortunately the article seems not to be on the NS website. (87.81 posting from . . .) 87.82.229.195 (talk) 14:06, 9 August 2010 (UTC)[reply]
I did see an article (can find it now) that said that desulphurisation caused local warming. I was wondering if this was an reasonably established fact or not. I've not seen or heard this side effect mentioned in the news etc..
As to Ariel's comment - I'd be interested in a enviromental cost benefit analysis - but a proper referenced one I could read for myself.87.102.35.46 (talk) 15:31, 9 August 2010 (UTC)[reply]
You would have to inject the sulfur into the stratosphere to cause cooling and prevent acid rain. ~AH1(TCU) 22:42, 9 August 2010 (UTC)[reply]
St. Bernard dog
Why the St. Bernard dog is not recognised by the italian ENCI (Italian National Kennel Club)? 82.59.69.48 (talk) 13:10, 8 August 2010 (UTC)[reply]
That's a tough one for us to help you with since all the info is in Italian. Try asking on the Italian wikipedia. Also I'm not sure this question belongs in the science desk. Ariel. (talk) 05:23, 9 August 2010 (UTC)[reply]
Thanks. Ok, I will try to ask in the italian Oracolo too. I know, the question is border line here (is about a bureaucratic issue regarding applied biology), if you want to move it please feel free to do that, though the major experts in this matter should be here. Ok, so undirectly the ENCI recognises the St. Bernard; but why doesn't the breed appear in ENCI list? —Preceding unsigned comment added by 87.11.129.247 (talk) 16:57, 9 August 2010 (UTC)[reply]
wave analyzers
which analyzers we will use to check the frequency of the wave having frequency above 20GHZ? Is it spectrum analyzer or not —Preceding unsigned comment added by Balachandramovva (talk • contribs) 17:12, 8 August 2010 (UTC)[reply]
You can buy oscilloscopes that reach that frequency. Is that what you are asking? Ariel. (talk) 05:28, 9 August 2010 (UTC)[reply]
Here and here are manufacturers of frequency counters that cover the 0 to 40 GHz frequency range. Here is a 20 GHz spectrum analyzer. Cuddlyable3 (talk) 12:35, 9 August 2010 (UTC)[reply]
Yoplait has a fat-free Greek yogurt.
I thought a big part of Greek yogurt was its high fat content. What's the point otherwise? 67.243.7.245 (talk) 18:45, 8 August 2010 (UTC)[reply]
Our Strained yoghurt says that what's called 'Greek yoghurt' typically just means some form of strained yoghurt. So I would guess taste as Cyclonenim mention and texture would be a big reason why some may want 'Greek yoghurt'. Our article also notes "strained yoghurt is a traditional food in the Middle East and South Asia, where it is often used in cooking, as it is high enough in fat not to curdle at higher temperatures" which may be what you're referring to and it indeed seems likely that advantage would be lost but I guess quite a number of people aren't choosing it so it doesn't curdle at higher temperatures as you have presumed Nil Einne (talk) 19:51, 8 August 2010 (UTC)[reply]
For the record, several companies offer fat-free frozen yogurts, in vanilla and other flavors (I prefer vanilla). They do not lack in taste, but I suppose Greek yogurts might. 2Ð ℳǣ$₮ℝʘtalk, sign 23:06, 8 August 2010 (UTC)[reply]
We have fat-free greek yogurts in our freebie kitchen at work - the actual yogurt doesn't taste of much - but they come with actual fruit at the bottom - so step #1 is stirring them up! SteveBaker (talk) 00:21, 10 August 2010 (UTC)[reply]
How does a car's wheels get out of alignment?
How does a car's wheels get out of alignment? My understanding is that driving over potholes and hitting the curb hard when parking can both cause alignment problems. What are some other causes? Also, what exactly happens when something causes your car's wheels to be misaligned? Is something in your car deformed? --173.49.16.4 (talk) 18:53, 8 August 2010 (UTC)[reply]
Joining the front steering wheels of a car there is a significant length of mechanism consisting of push-rods, threaded adjustors, gears, bearings and dampers. This mechanism is relatively light in weight. Impacts to the steering wheels, such as impacts with potholes and the curb, can cause movement in the threaded adjustors. However, much of the drift in the alignment is caused by wear of the tires. Even a change in tire pressure from the pressure that existed during the last alignment can necessitate re-alignment. Wear in the gears, bearings and dampers in the steering system also contribute to drift in the overall alignment. Deformation of the body of the car is not a contributor to misalignment, except if the car has been involved in an accident. There is a little information at Wheel alignment. Dolphin(t) 23:31, 8 August 2010 (UTC)[reply]
fridges
What is the reason some people say you shouldn't close a fridge door when it's turned off? Do modern fridges overcome this? 82.43.88.151 (talk) 19:53, 8 August 2010 (UTC)[reply]
No, this applies to all fridges and freezers of every vintage. It is almost impossible to avoid the growth of moulds and bacteria at room temperature, but normal circulation of the air with an open door helps to prevent excessive growth. Cleaning out the fridge with bicarbonate of soda will also help. Dbfirs 20:52, 8 August 2010 (UTC)[reply]
If you leave it open for a long while, and let it dry out it's OK to close it later. Ariel. (talk) 21:49, 8 August 2010 (UTC)[reply]
Yes, I agree that the damp conditions encourage the growth of nasties, but I'd still prefer to clean the inside before closing the door. Dbfirs 21:54, 8 August 2010 (UTC)[reply]
So to clarify, because I'm still confused, the reason people say the door shouldn't be closed is... to stop mold growing? 82.43.88.151 (talk) 22:16, 8 August 2010 (UTC)[reply]
Yes, and bacteria. If you open a fridge door after it has been closed for a long time at room temperature and without drying out as Ariel suggests, you will notice a horrid stink of decay (the bacteria) and a musty smell from (usually black) patches of mould (mold in the USA) which can also attack the plastic and rubber seals of the fridge. Dbfirs 23:03, 8 August 2010 (UTC)[reply]
Additionally, if a refrigerator is being removed for disposal, the door is normally removed for safety reasons, so that playing (hiding) children won't get trapped and suffocate. Kingsfold(Quack quack!) 16:40, 9 August 2010 (UTC)[reply]
I agree, it seems as though no matter how carefully you clean/disinfect the inside of an empty refrigerator - if you unplug it and close the door then it will stink horribly within just a couple of days - and pretty soon you'll see black mold spots. If you clean it and leave the door open, it'll be fine.
Moisture trapped inside the fridge seems to be the problem - even the smallest amount of nutrient - plus darkness and moisture produces the perfect place for mold to thrive. Remember, the refrigerator doesn't just chill the air - it also dehumidifies it. The inside of a (running) refrigerator is a spectacularly dry place - and mold can't survive without moisture.
If capillary action raises the center of mass of the water in the tube, where does the energy come from? 76.68.247.183 (talk) 19:55, 8 August 2010 (UTC)[reply]
I think it might come from the Gibbs free energy, but perhaps you should wait for an expert to confirm or refute this. The article doesn't make easy reading! Dbfirs 20:53, 8 August 2010 (UTC)[reply]
It comes from potential energy. It takes energy to "unstick" the water from the surface of the tubes. Water, by it's nature, is at a slightly higher energy. When it sticks to something it goes to a lower energy. Note that tall trees do not use capillary action to raise the water. Instead they evaporate some water from the leaves on the top, and the lower pressure "pulls" water up from the roots. Ariel. (talk) 21:41, 8 August 2010 (UTC)[reply]
We do, of course, have an article on the subject: Transpirational pull. If I'm interpreting it correctly, it is basically a combination of transpiration and capillary action (or something closely related to it) that makes it work. --Tango (talk) 22:37, 8 August 2010 (UTC)[reply]
(ec)Yes, I meant to say don't just use capillary action. There is a third mechanism they use as well, but I don't remember what it is. I'll try to look it up later. Ariel. (talk) 22:54, 8 August 2010 (UTC)[reply]
Yes, it is impossible for "lower pressure" to "pull" water more than 34 feet high, so the main effect must be capillary, as stated in the article. There may also be some osmotic pressure. I am still awaiting an expert to check on my Gibbs claim, though Ariel referred to "water energy" which might be the same thing. The OP was asking where the potential energy comes from as the water rises through capillary action. Dbfirs 22:52, 8 August 2010 (UTC)[reply]
It's not something I know a great deal about, but our article says Gibbs free energy is the ability to do non-mechanical work. Lifting something against gravity is mechanical, isn't it? The osmotic pressure you refer to is root pressure, which is a factor in some circumstances. --Tango (talk) 23:19, 8 August 2010 (UTC)[reply]
Root pressure is feeble - it is only able to move water ~30cm upwards. The differences in water potential between the roots + shoots is a driver for water flow however. Smartse (talk) 22:31, 9 August 2010 (UTC)[reply]
As Dbfirs above suggests the energy comes from the interaction between the water and glass - which is favourable in terms of energetics - ie it can do work.87.102.23.179 (talk) 01:07, 9 August 2010 (UTC)[reply]
No, no, no! NO free energy! Let's not even contemplate the possibility for a nanosecond! You can't make perpetual motion machines using surface tension - although plenty of very stupid people have tried!
This is no different from taking a stretched elastic band - releasing it and asking where the energy came from to contract it. The energy was put into the elastic band when you stretched it - it contracted in order to get into a lower energy state by releasing that energy. It happened because the rubber molecules like being coiled up - it takes energy to uncoil them - and they give up energy when you let them coil back up again. Same deal here. Water molecules like being stuck to glass more than they like being stuck to other water molecules. Not all molecules are like that...Mercury, for example prefers the company of other mercury atoms than it does glass and has an upside-down meniscus and tends to sink down a capilliary tube rather than rushing up it. It's all to do with hydrogen bonding and Van der Waals forces.
The water (when it's at the bottom of the tube) is in a higher energy state than when it's at the top of the tube - because (like a stretched rubber band) it is in a configuration it doesn't want to be in. It actually loses energy in moving up the capilliary tube...even though it's moved upwards against gravity (and therefore has more gravitational potential energy). It gave up more energy than that by clinging to the glass than it lost in the upward motion - just like the rubber band un-stretching.
Once the water is stuck to the glass, you have to add energy to get the water to go back down to the bottom of the tube again. That's why cars need windshield wipers. The raindrops like being stuck to the glass - you have to put energy into wiper blades to get persuade it to fall off.
You can't extract energy from the height of water in the capilliary tube because you have to use energy to unstick it from the glass. Kinda like pulling a magnet off of your refrigerator.
Of course it's free as in speech, not free as in beer. --Trovatore (talk) 00:36, 10 August 2010 (UTC)[reply]
It was "free" as in "available" (like a stretched band), not "free" as in "perpetual motion", but I agree with Steve's analysis. There is an official recommendation to remove the word "free". Perhaps our article should just be "Gibbs energy". It's probably not a very helpful concept here because it is more usually applied to chemical reactions rather than to physical attractions between molecules, but it does emphasise the fact that all substances have internal energy in their atoms and molecules. Smartse's water potential link is better, but I suspect that matrix potential alone is not sufficient. Does the tree also input energy to create osmotic differentials to implement capillary action in stages? There is a limit to the height attainable in any capillary tube (otherwise we run into Steve's objection of perpetual motion). Dbfirs 02:08, 10 August 2010 (UTC)[reply]
No, I think the article should stay where it is. IUPAC and similar organizations can recommend all they want; we should change when common practice actually changes, not because some body made something "official". --Trovatore (talk) 02:24, 10 August 2010 (UTC)[reply]
OK. I understood the meaning of "free", and I don't suppose many non-specialists read the article anyway. I agree that we should reflect general usage. Dbfirs 02:41, 10 August 2010 (UTC)[reply]
Yes, it is "free energy" in the technical sense (not in the perpetual-motion machine sense). Understandably, this nomenclature is confusing (and reeks of violation of the second law of thermodynamics) - but that is a matter of language-use. No actual physicist or chemist thinks "Gibbs free energy" comes from nowhere. It's "free" in the sense that it is not inherently bound to the internal process that is moving energy from a source to a sink; but energy still has to come from the source.Nimur (talk) 18:07, 10 August 2010 (UTC)[reply]
No one said it came from nowhere. I was just needling Steve on the no free energy comment. --Trovatore (talk) 18:31, 10 August 2010 (UTC)[reply]
Jumbo Jet vs. Mortal
Is it possible for a human being to move a Jumbo Jet by pulling it ? -- Jon Ascton (talk) 21:03, 8 August 2010 (UTC)[reply]
Never mind a jumbo jet (by which I guess you mean a 747) which is old (1997) news, the record appears to be for a 416,299 pounds (188,830 kg) CC-177[3][4]. Nil Einne (talk) 21:19, 8 August 2010 (UTC)[reply]
It depends only on the friction and nothing else. It does not depend on how heavy the jet is. I think jets have reasonably low friction on the wheels but I'm not sure. Ariel. (talk) 21:39, 8 August 2010 (UTC)[reply]
(ec) For an object on wheels, you just need enough force to overcome the friction in the bearings, etc., which isn't necessarily that great. Once it is moving, it will accelerate very slowly, so you need to be very strong if you want it to move a significant distance in a reasonable amount of time, but moving it isn't actually that hard. The difficult bit is probably getting enough grip with the ground so you don't just slip backwards rather than pulling forwards - if you apply too much force, your shoes will just slip against the ground, regardless of how strong you are. --Tango (talk) 21:41, 8 August 2010 (UTC)[reply]
The difficulty in moving a rubber-wheeled vehicle, such as a jumbo jet, comes not from friction in the bearings which is very minor. The difficulty is deforming the rubber in the tires. Rubber is not perfectly elastic so it displays elastic hysteresis. Much more energy is absorbed by the tires as they reshape during rolling than is absorbed by friction in roller bearings.
It is useful to contemplate moving a locomotive on steel wheels, or better still moving a ship through water. In the era prior to power-driven tugboats, ships had to be moved up and down rivers, and maneuvered to and from the dock, by rowing boats powered by nothing more than half a dozen men with oars. So large vehicles can be moved by manpower, but it doesn't help to be impatient! Dolphin(t) 22:56, 8 August 2010 (UTC)[reply]
If a human were in a space suit in orbit holding onto the International Space Station and a space shuttle, he/she could move them quite easily by pushing or pulling, since there is no friction. The speed would start out ever so slight and increase to a meter per second in under 4 minutes, if the person pushed with 500 Newtons (112 pounds force). A jumbo jet standing on the runway would require considerable force to start it moving on a perfectly level surface, probably more than anyone with normal strength could exert. Exerting that same force for a considerably longer time would likely leave the jumbo jet right where it started. Edison (talk) 03:37, 9 August 2010 (UTC)[reply]
How do you expect your astronaut to produce a force of 500N without separating from the space station? It's like the point I made above about your shoes slipping against the ground, but taken to the extreme. --Tango (talk) 03:50, 9 August 2010 (UTC)[reply]
Easy, the SS and Shuttle would be, say, 5ft apart and the astronaut would crouch between them and push orthagonally to move them apart: obviously the scenario of moving them "horizontally" relative to one another could not work using only surface friction, though foot and handholds on which to engage might enable a horizontal component. (87.81 posting from . . .) 87.82.229.195 (talk) 13:57, 9 August 2010 (UTC)[reply]
But you can only do that for a second or two. You can't do it for 4 minutes to get them up to 1 m/s (assuming constant acceleration, they would be 120 metres apart by the end of the 4 minutes). --Tango (talk) 16:43, 9 August 2010 (UTC)[reply]
Many adult humans of normal strength could exert a 112 pound force for 3 or 4 minutes. Lots of adults who should weigh 130 pounds actually weigh 240 and engage in all sorts of activities. People sometimes carry heavy burdens long distances, or push or pull heavy things. Edison (talk) 19:20, 9 August 2010 (UTC)[reply]
You can only do it for a second or two because after that the spacecraft will be out of reach. --Tango (talk) 22:17, 9 August 2010 (UTC)[reply]
I have some ambivalence about calculations versus perceived reality. I would not think that an angry astronaut could attack the space shuttle or space station and destroy it with his bare hands. But it seems that if he had his feet hooked around a stanchion on the ISS, and held a rope attached to the shuttle, he could in a few minutes generate enough relative velocity to crash them together disastrously. And if he started to push or pull with 500 Nt force, would folks on the 100000kg space shuttle feel the "jerk?" Edison (talk) 02:07, 10 August 2010 (UTC)[reply]
It's obviously possible - there are lots of videos of it being done ([5] for example). The problem of moving a plane is basically four-fold:
Overcoming static friction. Most surfaces produce more friction when they are stationary than when they are moving. Once you get them moving (even very slowly), static friction goes away.
Overcoming regular dynamic friction. Traditionally, weight plays a big part in the amount of friction there is - but we're not talking about one surface rubbing against each other - this is rolling friction which is mostly due to tyre deformation and such like. There is a certain amount of traditional friction in the bearings of the wheels - but that's really very small.
Overcoming aerodynamic drag. This is a non-problem at the super-low speeds we're taking about - planes are also really well streamlined!
Producing an acceleration. Acceleration equals Force divided by Mass - so mass is really important here. But acceleration is another non-problem. No matter how small the acceleration you are able to produce, the speed will gradually build up until all of the force you're able to supply is overcoming friction and drag. At the low speeds that a person could reasonably pull at, drag is negligable - so once you've got it moving, friction is 100% of the problem - and it doesn't change much with speed...so once the plane is moving, you can gradually speed up until you're pulling the plane pretty quickly.
Since the sticktion is bigger than the friction - this becomes only a matter of whether you can get the thing initially rolling. Once it's moving the distance and speed are largely irrelevant.
I used to know someone who did a charity jumbo-jet pull with about 20 co-workers (they got sponsorship from the airline for the distance they could pull it...which was kinda silly given the physics of it all...once they got it moving, they could have pulled it around all day!) The biggest concern of the company that runs these events was mostly concerned over people being run over by the plane once it was moving! The other little 'gotcha' is that you always assume they are doing this on level ground - but my friend said she could see that they'd picked a very gentle slope to do it on...so gentle it was hard to spot - but she spilled the bottle of drink she was carrying and could see the water rolling away ahead of her efforts to pull the plane. It only takes a very gentle slope to overcome friction on something like a plane. So this is very easy to fake - and since everyone is doing this for publicity and for a good cause, they all have incentive to cheat if they can get away with it. So we have to be super-careful about what we do and don't believe.
An additional help is that the tires on aircraft are inflated to a much higher pressure then on a car. Something like 150-200 psi if I recall, so tire deformation should be lower. Googlemeister (talk) 13:33, 10 August 2010 (UTC)[reply]
No, the weight is higher, so the deformation is about the same. Pounds of plane / PSI of tire = Square inches of contact patch (not including what the sidewall strength of the tire holds). In theory a tire is a circle with a contact area of zero. So the contact patch represents deformation of the tire. This is true in a car as well. Ariel. (talk) 17:08, 10 August 2010 (UTC)[reply]
I wouldn't be surprised if they overinflate before one of these stunts. APL (talk) 00:33, 13 August 2010 (UTC)[reply]
Food poisoning, even after cooking?
Can dead bacteria and viruses or other related compounds cause food poisoning, even after the food has been thoroughly cooked?
To put it differently, can food that's extremely old always be made safe for human consumption by merely cooking it? ☯Zenwhat (talk) 21:43, 8 August 2010 (UTC)[reply]
I think our article on Bacterial toxin answers your questions. I don't advise trying it out on yourself. Dbfirs 21:50, 8 August 2010 (UTC)[reply]
Putting it simply, it's not just the biological agents that cause food-borne illness, but also the toxic chemicals they leave behind. These chemicals can remain after cooking, so no, cooking old food doesn't make it safe.--el Aprel (facta-facienda) 00:15, 9 August 2010 (UTC)[reply]
I don't know why you felt the need to repeat what had already been said...Anyway, there are also bacteria/viruses that can survive normal cooking. The longer the food has been left, the more of these bacteria there will be...obviously. 90.195.179.60 (talk) 01:46, 9 August 2010 (UTC)[reply]
Your snotty tone is uncalled for, and a reference is always helpful. Edison (talk) 03:18, 9 August 2010 (UTC)[reply]
It hadn't already been said... A link had been provided to a page that included the information, but it can help to provide a summary here. --Tango (talk) 03:52, 9 August 2010 (UTC)[reply]
Another relevant article is Danger zone (food safety).. Some food can be far from "spoilt" but no amount of cooking will make it safe to eat if it has been in the "danger zone" for a few hours. Vespine (talk) 04:43, 9 August 2010 (UTC)[reply]
It's not food poisoning, and has nothing to do with how old the food is, but there's no way known to destroy prions and leave the food intact. Paul (Stansifer) 05:09, 9 August 2010 (UTC)[reply]
A good example is ciguatera. From the article: "Ciguatoxin is very heat-resistant, so ciguatoxin-laden fish cannot be detoxified by conventional cooking." Viriditas (talk) 05:17, 9 August 2010 (UTC)[reply]
Thanks for the help and the example! ☯Zenwhat (talk) 21:49, 9 August 2010 (UTC)[reply]
I saw this turtle about a quarter mile away from the Olentangy River in Columbus, Ohio, on a rainy afternoon in June. What kind of turtle is it? Thanks. —Preceding unsigned comment added by 98.28.19.62 (talk) 00:36, 9 August 2010 (UTC)[reply]
Conservation of matter argument for Climate Change and Alternative energy?
Before the Great Oxygenation Event (GOE) about 2.4 BYA there was no, or very little, free oxygen in the atmosphere. Now there is 78% nitrogen, 21% oxygen and 0.0387% carbon dioxide. A portion of the carbon that used to be in the atmosphere is locked up in fossil fuels. Do we have any idea how much carbon is locked up as fossil fuel? I used to think that burning fossil fuels is effectivley undong the GOE, this seemed to me a good argument for alternative energy which didn't really rely on whether or not you "believe" in global warming. However, the articles about fossil fuels indicate that our FF reserves are mostly 300-600 million years old. Does this mean there is a whole lot of GOE Carbon locked up somewhere other then fossil fuel? Obviously "current" life (forests etc) has some carbon locked up, but as a percentage is that a big protion or a small portion? Or a tiny portion? How much fossil fuel IS there available to burn? And if we burn it all, or a good portion, can't we predict how much more co2 there will be in the atmosphere? Or are things like the ocean carbon sink too hard to predict? Even if we don't "undo the entire GOE" isn't increasing the CO2 level by 100 or 200 parts per million considered quite bad? So what would happen if we got to 0.1% or 0.5% atmospheric carbon dioxide? Is that really so "unlikely" at our current pace of emission? Sorry i know this is a bit all over the place.. Vespine (talk) 05:17, 9 August 2010 (UTC)[reply]
Well, the GOE was an oxygen event, not a carbon event. But more relevantly, the account above leaves out major parts of the carbon cycle. Most of the Earth's carbon is in the mantle, and this source gets into the atmosphere via volcanic activity. Also, atmospheric CO2, because it is acidic, reacts with rock via a process called weathering to give rise to carbonates. These carbonates end up on the sea floor eventually, and sooner or later the sea floor gets subducted and takes the carbon back into the mantle. All this is very slow, but it's fast enough to have recycled the entire sea floor several times since the GOE. The bottom line is that the carbon cycle can't be understood by looking only at atmospheric carbon, fossil fuels, and the biosphere, it's also necessary to take into account mantle carbon and carbonate rocks.
Regarding how much fossil fuel there is, the amount of oil is limited, but the amount of coal is huge, hundreds of years of supply even if we burn it as fast as we can. Looie496 (talk) 05:50, 9 August 2010 (UTC)[reply]
The burning of fossil fuels does lead to a measurable decrease in atmospheric oxygen. This is one of several pieces of evidence that let us know that the increase in atmospheric CO2 is, without any reasonable doubt, anthropogenic. However, if you look at the stoichiometry, it takes one molecule of O2 to produce one molecule of CO2. We have burned fossil fuels worth very roughly about 200 ppm of CO2 (about half of which is in the atmosphere, the other half has gone into other sinks). 200 ppm is 0.02%, so the effect on oxygen levels is relatively small. --Stephan Schulz (talk) 07:06, 9 August 2010 (UTC)[reply]
Are you saying that this 200 ppm ATM reduction of O2 has been measured? -- 119.31.121.66 (talk) 12:36, 9 August 2010 (UTC)[reply]
No. As far as I know, we have reliable records for atmospheric O2 only since the mid 1980s or so. But since then, decrease in oxygen has been largely in inverse lock-step with anthropogenic CO2 emissions (there are some subtleties because CO2 is much more soluble in sea water than oxygen is). --Stephan Schulz (talk) 12:57, 9 August 2010 (UTC)[reply]
Most of the GOE carbon ended up as sedimentary carbonates and kerogens. The amount of carbon that can be burned as fossil fuels is large compared to either the atmosphere or the biosphere, but infinitesimal compared to the amount of carbon that has been incorporated into sedimentary rocks in forms that are not useful for combustion. Burning all of the fossil fuels would be bad, but it would only barely make a dent in the amount of oxygen that exists in the atmosphere. Dragons flight (talk) 07:54, 9 August 2010 (UTC)[reply]
That's some really great answers, precisely the kind of information I was looking for. Thanks everyone. Vespine (talk) 03:30, 10 August 2010 (UTC)[reply]
Present day radiation levels at Hiroshima and Nagasaki
I was wondering if anyone knew the present day radiation levels above normal at ground level, if any, in Hiroshima and Nagasaki? Thanks. 150.49.180.199 (talk) 05:48, 9 August 2010 (UTC)Mark[reply]
I don't have a source for this but I was under the impression that Hiroshima now has the same levels of radiation as the global average. This is because the bomb exploded in the air rather than on the ground, and irradiated air moves on eventually. If it had exploded on the ground, I would expect the perseverance of the radiation to be much worse. Someone feel free to shut me up :) Regards, --—Cyclonenim | Chat 09:47, 9 August 2010 (UTC)[reply]
No need to shut you up, you're right. From the little boy article, "Because Little Boy was an air burst 1,900 feet (580 m) above the ground, there was no bomb crater and no local radioactive fallout." The statement has this reference. I would dangerously assume that the conditions were the same for the fat man explosion. Ks0stm(T•C•G) 09:50, 9 August 2010 (UTC)[reply]
The very first Google search result for 'radiation level hiroshima' [6]. Bing isn't so good (IMHO) finding a bunch of Yahoo answers and other things but does find [7] as the 9th result (6th on Google). Google also finds RERF as the 4th and [8] (see q12) as the 9th result. RERF which I highlighted is perhaps the best of those resources. Nil Einne (talk) 09:59, 9 August 2010 (UTC)[reply]
An article "Residual radiation in Hiroshima and Nagasaki"[9] is available for payment from The Lancet. Yahoo Answers says that radiation from the bombs is long gone[10]. Cuddlyable3 (talk) 15:16, 9 August 2010 (UTC)[reply]
Is there a reason you continue to cite sources like Yahoo! Answers even though they are clearly not reliable? Do you even read the responses before you cite such things? The Lancet is at least a reliable source but the abstract makes it pretty clear (which I then verified with the actual article) that the article in question is only talking about residual radiation in 1946, not the present day. It is entirely inapplicable to the current discussion. --Mr.98 (talk) 15:52, 9 August 2010 (UTC)[reply]
Yeah - Yahoo! Answers is just another "asking random people on the Internet" site - just like this one - except that their reliability has been shown to be vastly worse than ours. We shouldn't reference them because the probability of improving our answer is worse than chance! SteveBaker (talk) 22:40, 9 August 2010 (UTC)[reply]
The Marangoni Effect in a wineglass
I recently posted a question concerning the toroidal motion of sediment in the base of a near-empty wineglass (the content was that which had gathered in the bottom over a roughly fifteen minute period). I noted that even though the glass had not been touched for this period and that there were no obvious sources of vibration energy etc. the sediment continued to move in its toroidal pattern seemingly without further input. The Marangoni effect was suggested and I think, having researched this penomenon's various manifestations, that I agree that this is what was going on. My question now concerns the 'actors' in this instance. The Marangoni effect has been presented by various sites as transfer caused an inequilibrium of some sort, be it density, alcohol concentration or whatever, with tantalising hints that surface tension differences point to a more correct interpretation. In my wineglass example, what are the sources of this imbalance? I am assuming that water and ethanol are the major parties and that the sediment simply makes the effect more readily visible, but what is the nature of the inequilibrium and how are the two liquids interacting to resolve it? Also, why does this only happen with a near-empty glass and not a full one (assuming that this observation is true, naturally). I am researching this for a book (fiction) and want to get my facts straight as the explanation is to be given by a (again fictional) professor of fluid dynamics and to an individual who is scientifically literate albeit in a different field.
I would speculate that the reason this only happens with a near-empty wine glass is because of the amount of energy required to make this start (and continue). The less liquid, the less energy you need. If surface tension or evaporation is implicated, it is also the case that the less liquid there is, the larger the surface-area-to-mass ratio (assuming a roughly hemispherical bottom to the glass). I kinda wonder (without any particular evidence/math to back it up) whether there is some kind of conservation of rotational inertia going on here. Is it possible that a slow motion rotation of the bulk liquid is somehow 'concentrated' into the bottom of the glass as you consume the wine?
We get quite a few questions about the weird behavior of liquids in cups and glasses - they are interesting science - but really tough to answer well! SteveBaker (talk) 22:37, 9 August 2010 (UTC)[reply]
The way a slow rotation of the bulk liquid is concentrated into an anomalous activity near the center of the bottom of the glass (and other weird behaviour of liquids in cups and glasses) may be the secondary flow of the boundary layer on the floor of the glass. See Secondary flow#Circular flow in a bowl or cup. Dolphin(t) 05:44, 10 August 2010 (UTC)[reply]
Thank you both for your answers, I appreciate the time it takes. One thing I would really like to know though is the nature of the disequilibrium in the wine. Does it concern water and alcohol? If so, what is it about them which makes the disequilibrium appear and how does the motion resolve it? I take the point made about the smaller amount of energy required to move a small amount of liquid making this effect more likely to occur in a near-empty glass, but I wonder if it occurs all the time, near the surface, and is only visible in a near empty glass is that when the glass is near empty, the sediment is naturally involved where it hopefully would not be in a full glass.
My theory concerning this effect is that the alcohol water are simply well mixed - the alcohol is not dissolved in the water, or vice-versa, so at the surface there will be a mixture of water molecules and alcohol molecules in contact with the air. The alcohol is less dense than the water and so, given sufficient time will tend to rise, but I suspect that inter-molecular forces will reduce this to a near negligible effect; otherwise alcohol would separate out in stored wine etc. The alcohol is also more volatile and so, will evaporate more readily. I suspect that this is a sufficiently strong effect to cause a gradient in alcohol concentration which drives the motion until the alcohol runs out. Actually, in explaining my thoughts, I realise that I understand this even less well than I thought. Help someone! :)
I'm looking for a specie of crickets. It is brown with a little orange tail, and can be found here in The Netherlands, I fond alot of them in the dunes. Aeno•talk to me 13:07, 9 August 2010 (UTC)[reply]
Chorthippus brunneus
Chorthippus brunneus[11] is called the Common Field Grasshopper in English. "The mature male becomes reddish orange at the tip of the abdomen"[12]. I don't speak Dutch but this page[13] is entitled Bruinesprinkhaan Tandradje (Chorthippus brunneus). Alansplodge (talk) 18:35, 9 August 2010 (UTC)[reply]
Thanks! That's the one I was looking for. Aeno•talk to me 15:10, 10 August 2010 (UTC)[reply]
pollution
what are the effect of mine blasting on global warming? —Preceding unsigned comment added by Yashodeep1996 (talk • contribs) 14:10, 9 August 2010 (UTC)[reply]
Do you mean the use of explosives as part of the mining industry? In that case, there is basically no direct effect. Explosives probably release some greenhouse gases (aiding global warming). Explosions also produce dust (inhibiting global warming). Regardless, the scale is far below the industrial level needed to make a significant impact. One could also discuss the impact of explosives vs combustion-driven equipment vs raw human labor, but I expect that we're still well below meaningful amounts. As a secondary effect, mining can potentially have wide-ranging impacts, but then we've moved away from "blasting" to instead discuss the methods and/or products of mining. Finally, a note on why clarification is important: searching for "mine blasting" on WP predominantly returns results for land mines. — Lomn 15:00, 9 August 2010 (UTC)[reply]
According to http://cryptome.info/explosives.htm US explosives production was 2.53 Million tons p.a. in 2004 - assuming that could be the energy equivalent of TNT (TNT equivalent says 1 MT of TNT = 4.183PJ) that's ~10 PetaJoules of energy from explosives. Compare with energy use in the USA for electricity (List of countries by electricity consumption) of 3.9 petawatthours = 14040 PetaJoules - so the fraction is less than 0.1% (of energy from electricity not total energy)
Assuming all that explosion creates 3x as much mass of CO2 then that's ~7.5Million ton of CO2. The USA produced ~6500 million tonnes of CO2 in 2007 List of countries by carbon dioxide emissions so that is clearly about 0.1% of the total emmissions.
It does indeed seem to be a small amount relatively. (Hope my figures are mistake free).87.102.35.46 (talk) 15:43, 9 August 2010 (UTC)[reply]
Cement
Is this likely to be portland cement or could it be another type? The article on portland cement suggests that it's the most common type. ----SeansPotato Business 14:13, 9 August 2010 (UTC)
I added the missing title. Cuddlyable3 (talk) 14:45, 9 August 2010 (UTC)[reply]
If you click on the "Health & Safety Information" box under "Features" on that page, the product heading is "Blue Circle Portland Cements", so I'd say that it's indeed Portland cement. Deor (talk) 14:55, 9 August 2010 (UTC)[reply]
Just an up front notice that this isn't a request for medical advice, but general, practical advice.
I seem to have a serious problem waking up to alarms. Alarms, especially when I'm sleeping at home, seem to have a tendency to not wake me up. When I'm sleeping away from home, the effect of me sleeping lighter can occasionally overcome the inability of alarms to wake me up, but normally (and especially at home) I just sleep right through the alarm without even hearing it go off. When/if I hear it go off (wake up), I get out of bed with relative ease, it's just the fact that I don't wake up until after they've been going off for (at times) over an hour. The alarms that seem to do the best at waking me up are my cell phone alarm at full volume and this alarm called the "Screaming Meanie" that produces a noise so loud that it makes my ears ring for hours afterwords (It's never failed, I stopped using this one because I began to think it might be damaging to my hearing). What can I do to increase my ability to get up to alarms considering that I only have one year to acquire the ability before going off to college? In what ways can I maximize my chances of hearing the alarm on any given day? In short, how do you wake up to an alarm when you don't even hear it go off in the first place? Ks0stm(T•C•G) 19:12, 9 August 2010 (UTC)[reply]
Forgot to add that I do take medication to help me sleep (thus the "I'm not requesting medical advice" disclaimer"), and it does negatively affect my abilities to wake up in the morning. Ks0stm(T•C•G) 19:27, 9 August 2010 (UTC)[reply]
Phone alarms that I've heard tend to be quite...nice. Find a sound that's really really annoying (you may even be able to download such a sound for your phone alarm). 90.195.179.60 (talk) 19:40, 9 August 2010 (UTC)[reply]
If your difficulty waking up is as a result of taking sleeping pills, then its a side-effect of the pills and not something we can help with, since that would be medical advice. You need to talk to whoever prescribed the pills. --Tango (talk) 20:01, 9 August 2010 (UTC)[reply]
Option 1: Get a random alarm. Don't increase the volume. Your subconscious listens to the sound and decides if it's important enough to alert you to it. After a while you will get used to an alarm sound, and it will no longer be considered important. But if you give it a new sound it won't know what to do with it. Option 2: You can also train it. During the day play the alarm and as soon as you hear it jump up and be very active - get to the point that it's automatic - you hear the sound, you jump, without even thinking about it. Additional Note: If you are medicated you may be physically unable to wake up, and no alarm will work. Talk to your doctor about the dose. Ariel. (talk) 20:04, 9 August 2010 (UTC)[reply]
Sounds like you've got caffeine addiction, or at least you are not getting enough sleep. Give up tea and coffee, go to bed earlier. 92.15.27.40 (talk) 20:20, 9 August 2010 (UTC)[reply]
You have a wall of text, so I didn't read it, but have you tried doing nothing more than putting the alarm across the room and seeing if you get up and turn it off then? Secondly, before you go to sleep, reflect on the number of hours you will sleep (count): picture that many hours, then picture yourself getting up afterward. Finally, if you are not going to get at least 6 hours, set the exact time to be an increment of 90 minutes (or 45) from when you will fall asleep (7 to 15 minutes after you set the alarm.). If it's 2:20 AM and I have to get up at 4:15, no way would I be able to do that, I would totally sleep through any alarm. So, I've showever and brushed my teeth, then count 2:20 AM plus 90 minutes is 3:50, and until 415 that's exactly 25 minutes or smack-dab in the middle of a cycle. I will set it for 3:50 instead, reflect on the 90 minutes of sleep I'm about to get, and fall asleep. I get up on time, and won't be particlularly tired until 4-6pm the next day, when the hour and a half of sleep will cath up with me. My point is, if instead of an hour and a half it had been an hour and fifty-fie minutes, no way would I have been able to get up.
of course, the best policy is to go to sleep on time: no caffeine after 6 pm!! 85.181.49.221 (talk) 21:01, 9 August 2010 (UTC)[reply]
Ironically, you were unable to read the OP's "wall of text" (253 words), and yet you responded with your own "wall of text" (256 words), which was even more pointless given that you had not bothered to read the question. If that's the best you can do, you're better off not answering. --Mr.98 (talk) 01:16, 10 August 2010 (UTC)[reply]
It's not that long a question and had you read if you would have learned that the OP has no difficulty getting up once awake, the problem is waking up. --Tango (talk) 22:25, 9 August 2010 (UTC)[reply]
I found that waking up to a talk-radio station - or using a talking alarm clock ("The time is six forty-five A.M."...updating every 5 minutes) - works much better than music or beeps/bells/squawks, etc. Evidently the sound of voices does the trick for me. I don't think volume is the answer.
I'm with Steve. Try something other than an alarm noise. I found that when my clock made loud alarms, I would instinctively mash the snooze button and go back to bed without even remembering doing so. I only realized it had happened when I eventually woke up (much) later than intended. After switching it to play music instead, sometimes a really good song will happen to be on the radio and I'll stay awake a few minutes to listen to it. By the end, I'm about ready to get up. Worth a shot. 75.157.57.12 (talk) 08:38, 10 August 2010 (UTC)[reply]
If the sound of an alarm doesn't wake you, how about buying a vibrating alarm clock? There appear to be a lot on the market, aimed at those who are deaf or hard of hearing. Smartse (talk) 22:40, 9 August 2010 (UTC)[reply]
There are various ingenious alarm clocks which will start Rube Goldberg devices to pull off the covers, vibrate the bed, dump you out of bed on the floor, make louder and louder noises, etc. My deaf niece has an alarm which shakes the bed, so such things are readily available. A silent movie by Thomas Edison from the early years of the 20th century had a man who couldn't wake up tie a rope to his ankle and leave it dangling out side the window, for his friend to tug on it in the morning and wake him up. Naturally hilarity ensued with a drunk yanking on it, etc, and eventually a wagon getting tied to it , with the horse setting off and dragging the sleeper out the window and through the town. Therefore I do not recommend the ankle rope through the window routine. "Inability to wake up" sounds like a medical issue, although I have known young adults in whom it seemed to be a form of rejection of responsibility and passive aggression where sleep medication was not involved. "Alarms don't wake me up" might be a form of rejection of responsibility, like "It's Mommy's job to get me to high school on time." No, it's your job, no one else's. If the alarm clock gets louder and louder, eventually it will annoy the dorm neighbors, who will pick the room lock and dump icewater on the sleeper or shoot him with pepper spray until he learns to get up and be a productive member of society. Or he will flunk out of school due to missed exams, or get fired from his job. Edison (talk) 01:47, 10 August 2010 (UTC)[reply]
Oddly, I find visualisation really helps me wake up at the right time. While lying in bed before going to sleep, I picture the current time, and picture the time I need to wake up, and think about those and the time difference between them. I think to myself that I must get up at that time, or I won't have time to get ready and leave the house. I picture myself getting up quickly and immediately at that time, and do a quick imaginary run-through of the first few minutes of my morning routine. I've had real problems waking up to alarms for a while, but when I do this I manage much better. The only problem is that it can lead to anxiety, if not done carefully, which then makes it harder to get to sleep in the first place! 82.24.248.137 (talk) 22:01, 10 August 2010 (UTC)[reply]
What's in the yellow mounds on the green (top right) ? East of Borschov 21:04, 9 August 2010 (UTC)[reply]
It's hard to tell at this distance, but it may be gorse or heather, flowering yellow. -- Finlay McWalter • Talk 21:12, 9 August 2010 (UTC)[reply]
My guess would be gorse - while it's hard to get the scale on a picture like that the plants look rather too tall for most heathers. But yes, it could certainly be either. ~ mazcatalk 21:55, 9 August 2010 (UTC)[reply]
There are lots of types of common yellow flowers in that part of England - it could be buttercups or any of half a dozen other things. What's odd about the picture is that the yellow patches are only visible on top of clumps of dirt - not on the flat grassy bits. I suppose the exposed dirt might get re-inhabited by flowers before the grass can take over and choke it out or something. It's hard to tell without a closer inspection. SteveBaker (talk) 22:24, 9 August 2010 (UTC)[reply]
Steve, if you go to full resolution (the picture is huge) it's very obvious that the plants are flowering low bushes, not small ground flowers on 'clumps of dirt.' 87.82.229.195 (talk) 10:01, 10 August 2010 (UTC)[reply]
The harsh environment of a hilltop precludes most meadow and forest wildflowers, and the proximity to the sea make it worse. You do find flowering plants in a seaside Machair environment, but this is the wrong location, altitude, and geology. That leaves very hardy low-lying shrubs - if it's not heather or gorse, it's something of a similarly tough, and mostly inedible, disposition. The "clumps of dirt" are just the non-flowering bits of the shrub. -- Finlay McWalter • Talk 22:36, 9 August 2010 (UTC)[reply]
I'm certain it's gorse; *When gorse is out of blossom, kissing's out of fashion"[14] (old English saying). Alansplodge (talk) 02:30, 10 August 2010 (UTC)[reply]
I agree, it is almost certainly gorse on the grounds that I cannot identify an alternative. Yellow heather is possible but very unlikely given the alkali nature of the soil. It might be dwarf gorse, but again it is out of its normal habitat. Richard Avery (talk) 07:52, 10 August 2010 (UTC)[reply]
Only a guess but Signal crayfish seems to fit. The one in the picture I wouldn't describe as "rather large" however. If not that it could be one of the other Pacifastacus but there isn't really enough info on most of the others to make a guess.. Vespine (talk) 03:42, 10 August 2010 (UTC)[reply]
It is the less common crayfish. The more common ones are lighter brown 2 cm (1 inch) long crayfishes. They are found in all other streams. These range from 2 cm to about 8 cm. --Chemicalinterest (talk) 11:01, 10 August 2010 (UTC)[reply]
Having a look at google images, maybe I was a bit too ambitious thinking I could have a reasonable guess, lol.. The subject looks a lot more complicated then I initially thought, looks like I even got the family wrong! I'd say your guess looks better then mine. Vespine (talk) 23:01, 10 August 2010 (UTC)[reply]
I dunno..I've learned more about sea gulls on these desks than I ever expected. Pfly (talk) 10:13, 14 August 2010 (UTC)[reply]
Looking for reference for an experiment about expectations and performance
I remember seeing on TV something about an experiment relating expectations and academic performance. In the experiment, students were divided into two groups and given identical math problems. One group was told that the problems were difficult. The other group was told something different, I think something to the effect that they should try hard, or something similar. In the end, the group that expected the problems to be difficult (and beyond the students' abilities?) did worse than the other group. I'm writing this from memory so I might have got some of the details wrong. Does anyone know what experiment that was? --71.185.169.212 (talk) 23:12, 9 August 2010 (UTC)[reply]
I've been thinking: A lot of people who are obese start out overeating by eating past satiation thinking they need to "stave off" hunger until the next meal, and misjudge how much they need. If people always only ate just enough to feel satisfied and did this again everytime they felt hungry rather than eating the standard 3 meals a day, would they keep gaining weight? And how much would this differ based on the quality of the diet? 68.76.158.13 (talk) 23:14, 9 August 2010 (UTC)[reply]
There are those that claim people should eat small meals regularly throughout the day. They claim this raises the basal metabolic rate and regulates insulin levels. This article discusses one such diet, and its critics - it seems there isn't enough evidence to know for sure. Similar advice (with similarly scientific sounding reasons) is often given to bodybuilders (e.g. bodybuilding.com, wikihow). All of these are more to do with claims about metabolism and insulin levels, and not so much about your "eat when you're hungry" theory (although hunger and insulin are related). -- Finlay McWalter • Talk 00:13, 10 August 2010 (UTC)[reply]
For many fat people, hunger is more psychological than physiological. If they see someone eat something good, they suddenly become unbearably hungry regardless of stomach fullness or blood sugar. If they smell fresh baked doughnuts, they are suddenly hungry. Hunger may attack 30 minutes after a big meal if something tasty is seen. Edison (talk) 01:33, 10 August 2010 (UTC)[reply]
For some people the "I'm hungry" meter is set wrong, and causes them to desire more calories than they need. So even if they obey hunger perfectly they may still become fat (i.e. they need 100, they want 110, so over time they get fatter and fatter). In other people the "perfect weight" setpoint is simply set high. So if they go lower then get extra hungry, but if they reach it then calories desired matches calories needed and they simply stay at that weight. So to answer your question: No. That would not solve the problem in many people. (But it would in some.) Ariel. (talk) 06:06, 10 August 2010 (UTC)[reply]
There is also the issue of people responding to "I'm thirsty" by eating instead of drinking water. That is the reason that liquid diets tend to be slightly successful in some people. It suppresses the "I'm thirsty" trigger. It does absolutely nothing for people who overeat for other reasons. -- kainaw™ 06:16, 10 August 2010 (UTC)[reply]
To go back to the original post one cannot disagree with the idea that if most people ate less they would be thinner. This is similar to the idea that if everyone drove a little slower there would be less accidents and deaths on the roads. The development of obesity is multifaceted and varies with individuals. The basic problem is overeating, but the causes of overeating are more complex than just feeling hungry at the sight of attractive comestibles. We have to consider self esteem, the inability of the individual to notice changes in body shape, the denial of a person to accept their obesity, the social acceptability of obesity, the insistent advertising by commerce, the increased availability of food, the increasing use of inappropriate ingredients in foodstuffs . . . and so on. Obesity is here to stay, and probably will worsen in the future.steps off soap-box. Richard Avery (talk) 07:34, 10 August 2010 (UTC)[reply]
Completely disagree. People eat too much for different reasons, and lack of access to healthy and nutritious food, large portions, lack of exercise, and a sedentary lifestyle supported by automobile transportation, television habits, gaming and internet, and desk-related work are all big contributors to obesity. Once you address all of these factors, you are well on the way to controlling your weight. Losing weight requires changing your entire lifestyle, and most people will not take that first step. Viriditas (talk) 03:37, 11 August 2010 (UTC)[reply]
Modern food has many calories in relation to its bulk from fat and processed carbohydrates (eg bread, pasta). It has also been designed to be very tasty and nice to eat. Bulk weight and fibre satiates hunger, not calories. Thus we overeat. I think eating a lot of vegetables and fruit while avoiding processed foods is the way to avoid weight gain without hunger. But evolution did not design us to cope with food always being available. See http://nutritiondata.self.com/topics/fullness-factor92.29.121.47 (talk) 10:40, 10 August 2010 (UTC)[reply]
How are bread and pasta "modern"? Bread has been around for millennia and pasta for at least a few centuries (its exact origins are disputed, it could easily be a couple of millennia old as well). Also, wouldn't something that satiates hunger without providing calories tend to make us undereat, not overeat? --Tango (talk) 11:04, 10 August 2010 (UTC)[reply]
You may be surprised, but bread and pasta are certainly not archaic foods and are currently available in many shops thoughout the world. I think I saw them for sale as recently as yesterday. Indeed, I consumed some myself a few days ago. I don't understand your comment about undereating, not something that most people (at least in the West if you want to pick pedantic hairs) will be in any danger from. 92.15.3.61 (talk) 16:06, 10 August 2010 (UTC)[reply]
From what you've said so far, how are bread and pasta any more 'modern foods' then vegetables and fruit?
Also I think Tango misread, as did I, your earlier comment. You said "Modern food has many calories in relation to its bulk from fat and processed carbohydrates (eg bread, pasta). It has also been designed to be very tasty and nice to eat. Bulk weight and fibre satiates hunger, not calories. Thus we overeat"
Reading carefully, it seems what you're saying is "Bulk weight and fibre, not calories, is what's needed to satiate hunger. But modern food has many calories compared to bulk. Therefore we overeat."
However if don't read carefully, it sounds like you're saying "Modern food has bulk weight and fibre which satiates hunger but doesn't satiate calories, therefore we tend to overeat", which doesn't make much sense (if that were the case, people would tend to undereat not overeat).
BTW, the acknowledgement it's only in certain areas that most people aren't at risk of undereating is an important want, since there are indeed a very large number of people who are at risk and they shouldn't be ignored. They don't relate to this question, but you should still specify what you're talking about instead of making broad-brushed claims.
"How are bread and pasta any more 'modern foods' then vegetables and fruit?" Do not take this the wrong way, but the above posting and other even lengthier postings in the same vein by the same author matches as far as I can see as a layperson to the description in the section Aspergers#Speech_and_language. 92.15.14.45 (talk) 21:18, 11 August 2010 (UTC)[reply]
Wait, so now you're saying you have Aspergers? How is that relevant to your strange claim that bread and pasta are 'modern foods', as opposed to foods which have been around for centuries (and are still eaten)? Notice you are the only one who treated 'archaic' as the opposite of 'modern'. 82.24.248.137 (talk) 16:52, 12 August 2010 (UTC)[reply]
Skipping breakfast will simply make you more fat. ~AH1(TCU) 23:52, 10 August 2010 (UTC)[reply]
Very interesting thread, the original poster is right, there are several study trials which have been conducted and have unanimously opined that smaller frequent meals DO INDEED reduce obesity. A quick search of national library of medicine ( www.nlm.nih.gov) will give you details of several trials which have come to the same conlusion. Smaller quantity, frequent meals definitely trigger insulin release and help in carbohydrate breakdown, it helps prevent distention of abdomen and also helps increase the basal metabolic rate.
So the original poster is spot on and as a medical practitioner I have to agree with him/her.
However, the subsequent posters have also presented valid facts, fighting obesity isnt a unidimensional battle. You just cant control diet alone and hope to win the battle against the bulge. Lifestyle modifications, fitness exercises and mental discipline are very important factors too. --Fragrantforever 07:16, 11 August 2010 (UTC) —Preceding unsigned comment added by Fragrantforever (talk • contribs)
August 10
What's the prospect of scientists creating enzymes that can treat prion diseases?
Based on what we know about prion diseases, what's the prospect that someday scientists will discover or engineer enzymes that can be used to safely break down amyloid plaques? --71.185.169.212 (talk) 01:50, 10 August 2010 (UTC)[reply]
I can't see any reason why it couldn't be done. They're just proteins and there are plenty of enzymes that break down proteins. I don't know enough about the subject to say how difficult it would, though. If scientists can find people with a genetic immunity that works by them producing a particular enzyme, then they might be able to track down the relevant gene, transplant it into a bacteria and then extract large amounts of the enzyme and administer it to patients, but no part of that process would be particularly easy. --Tango (talk) 03:10, 10 August 2010 (UTC)[reply]
Amyloid plaques consist of fragments of a larger protein, that build up outside of neurons. The key problems are those of drug delivery, as getting large molecules into the brain is extremely difficult, and selectivity: how to find a protein that digests amyloid plaques while leaving healthy proteins unaffected. I don't know for sure, but the amyloid plaques may be as much a symptom as a cause of the disease -- the breakdown of their parent protein may be the actual cause. Alzheimer's is also characterized by aggregation of an intracellular protein involved in maintaining the neuronal cytoskeleton, which would be even harder to target as it's intracellular. --Atemperman (talk) 05:25, 10 August 2010 (UTC)[reply]
Some care should be taken here with nomenclature. The prion proteinPrP forms the amyloid plaques that appear in the transmissible spongiform encephalopathies ('mad cow disease' in cattle, or Creutzfeldt-Jakob disease in humans) — but not all amyloid plaques are formed from prions. Indeed, when neurologists discuss amyloid plaques, the first thing that comes to mind is usually the amyloid beta peptide associated with Alzheimer's disease. (It is in this sense of the term that Atemperman's response above answers the question.) Amyloid beta does form amyloid plaques, but it is not believed to be a prion — amyloid just describes protein accumulations with a cross-beta structure and which exhibit certain histopathological features (like apple-green birefringence when stained with Congo red). It's also worth bearing in mind that PrP is not the only prion protein (several others have been identified in yeast, though PrP is so far the only known mammalian protein which can form a prion).
I'm going to assume that you're interested in the breakdown of PrP amyloid for the remainder of my response here. Developing a suitable protease requires meeting three major challenges. The first is that the protease even be able to digest PrP amyloid. This is a steep challenge all by itself; one of the hallmarks of PrP amyloid (and indeed, of most amyloids) is their resistance to protease digestion. PrP amyloid is resistant to detergent solubilization and even to exposure to proteinase K, which is able to digest normally-very-durable proteins like keratin (in hair). Nevertheless, there has been some work in this area; this paper describes some very aggressive enzymes secreted by thermophilic bacteria that might be able to do the job. (I'm not familiar with the literature in this area; that was just one of the first Google hits with the relevant keywords.)
The second challenge is one of specificity. Letting large amounts of an aggressive protease loose in human tissue is a recipe for disaster, unless it can be specifically targeted to PrP (ideally, just to misfolded PrP). The third challenge is delivery — Atemperman's response above describes the problem. TenOfAllTrades(talk) 18:51, 10 August 2010 (UTC)[reply]
Why did they change the iphone's antenna?
I don't recall any problems with the old one. What was the purpose of the change? 148.168.127.10 (talk) 13:24, 10 August 2010 (UTC)[reply]
They probably keep mum about this. But essentially, they wanted a new design (and may have needed more space or a different layout to realize the enhanced functionality). And from a technical point of view, reusing the structural elements of the frame as an antenna is exactly one of those very elegant ideas you fall in love with that unexpectedly turn around and bite you... --Stephan Schulz (talk) 13:37, 10 August 2010 (UTC)[reply]
Apple claims, and several independent tests have supported, [15] that the change improves reception in low-coverage areas -- provided that you don't hold the phone a certain way. My personal guess is that Apple's internal testing just didn't uncover the flaw: they've got an AT&T tower on their campus, so local testing isn't bothered. The phone that leaked in the field was enclosed in a case (which fixes the problem) -- so if that's typical, remote testing also wouldn't be bothered by the antenna placement issue. But that part is just guesswork. — Lomn 13:41, 10 August 2010 (UTC)[reply]
Ironically, the new antenna was designed to improve the connection. My own personal experience has been that the iPhone 4 is indeed better than previous models as long as you don't hold it with the Death Grip. A Quest For Knowledge (talk) 13:47, 10 August 2010 (UTC)[reply]
In addition to the suggestions above, relocating the antenna to the outside of the case frees up room inside. This allows more internal space for additional hardware or a larger battery.--Zerozal (talk) 14:08, 10 August 2010 (UTC)[reply]
watch what they do after September 30th. I bet by then they'll have sold all the ones produced with revision 1, and be selling the revision 2: what is that change? Perhaps nothing more than a resinous coating... 92.230.233.247 (talk) 14:45, 10 August 2010 (UTC)[reply]
Sounds like a person to me, and his voice seems totally normal to me. Ariel. (talk) 16:50, 10 August 2010 (UTC)[reply]
Agreed. He enunciates a little funny, and doesn't modulate much, but it's probably because he's trying to be easy to understand (he's not speaking conversationally). He's no voice actor but he does fine by academic standards. --Mr.98 (talk) 00:03, 11 August 2010 (UTC)[reply]
Cool research. Definitely a real person. A text-to-speech program wouldn't have gotten the rhythm of spoken language correct. For a particularly striking example, consider the phrase around 4:47: "The resulting mat # is consistent with the occlusions in the scene." The speaker puts a big pause at the "#" to let the listener focus in preparation for the coming big concept. There's no punctuation there; it takes intelligence to decide to put it in. Paul (Stansifer) 03:55, 11 August 2010 (UTC)[reply]
I think the speaker is using speed-up voice processing to limit the length of the video. Cuddlyable3 (talk) 10:13, 11 August 2010 (UTC)[reply]
yes! that must be it. thank you. the actual audio does sound computationally produced (as opposed to spoken as we hear it), because it is, but is a real person, because it is. 92.230.232.58 (talk) 11:29, 11 August 2010 (UTC)[reply]
Eh, I don't buy it. Sounds like a regular voice to me. Perhaps not one that you yourself hear around often, but around universities and science departments, it is not uncommon. --Mr.98 (talk) 13:02, 11 August 2010 (UTC)[reply]
The striping would lead me to think it is a leopard frog as I don't think pickerel frogs have such stripes. Googlemeister (talk) 14:13, 10 August 2010 (UTC)[reply]
According to the pickerel frog article, a pickerel frog is a type of leopard frog. (It doesn't say so explicitly, but it has a sentence that reads "All other leopard frogs ...".) Looie496 (talk) 22:43, 10 August 2010 (UTC)[reply]
Cycle helmets - do they reduce vision and impair hearing?
Hi all, thanks for reading.
A the title asks really, do cycle helmets impair peripheral vision and hearing, leading to greater likelihood of being involved in an accident?
I've been ot the CTC site ( http://www.ctc.org.uk/ ), and looked up some reports on helmet safety through google scholar, but they all seem to focus on injury patterns for helmet wearers and non wearers involved in accidents. I'm trying to find out if wearing a helmet actually does increase the likelihood of being involved in an accident.
Some facts/figures/reports would be great to back this up if you guys could.
This isn't homework, I'm having a robust conversation with a number of people on some forums, and its something I've been curious about for a while, but could never find the research to back-up my assertion that helmets do impair sensory perception, and in doing so, increase the likelihood of being involved in an accident.
These guys seem to manage OK. They're just the best in the world. The peloton of the Tour de France
Sorry, I know that's not an answer, but yours does seem to be a question based on rebellion and an unwillingness to change. HiLo48 (talk) 14:25, 10 August 2010 (UTC)[reply]
Look at this helmeted fellow. He would have to strain to see the helmet, and it's hard to believe it has any significant effect on his hearing. This is a bit like arguing that seatbelts are bad because they might trap you in a burning car. Perhaps true in a tiny minority of cases, but statistically marginal compared to the times they prevent serious injury. --Sean 14:28, 10 August 2010 (UTC)[reply]
I bicycle a lot. Helmets are uncomfortable when it is 38C (100F) outside, but they do not seem to impair my hearing because they do not normally cover the ears. Normally they do not cover any of the sight range either (at least for my Schwinn helmet). --Chemicalinterest (talk) 14:32, 10 August 2010 (UTC)[reply]
There would be many factors to control for in any study. For example, maybe cyclist who where helmets are simply more careful (in general) than cyclists that don't, and so would be expected to have a lower rate of accidents. You would want to start by asking yourself how many cycle accidents are caused by ignorance of peripheral vision or hearing on the part of the cyclist (whether wearing a helmet or not). As a personal opinion, I don't buy the peripheral vision argument: a cyclist should always look over the shoulder to avoid the blind spot, and the blind spot is not affected in the slightest by wearing a helmet or not (it's way to the front of any helmet design). Physchim62(talk) 14:42, 10 August 2010 (UTC)[reply]
Cheers all
@HiLo48 - You may have a point, and LOL at the Tour pic.
@Physchim62 - That was the main issue with the studies I did come across - the variables, particularly the ones that you mention, as well as issues of variable cycling competency, and the localities covered in various studies (obviously, road conditions, but also, localities with higher number of cyclists might record lower a lower than expected ratio of accidents because motorists the frequent that area are more familiar with sharing the road with cyclists etc).
I accept that my boldly proclaimed opinions on the subject elsewhere may have been entirely factually incorrect. Darn.
On the hearing front, I'd suggest that cyclists have more to be concerned about with the increasing numbers of virtually silent electric cars, than with helmets. HiLo48 (talk) 21:37, 10 August 2010 (UTC)[reply]
I would caution readers that the source linked above (a BBC story) doesn't quite jump to the same conclusions that the poster does in his text. The story only describes a study which noted that vehicles tend to pass closer (8.5 cm or about 3.3 inches; roughly 10% less total space) to cyclists wearing helmets than they do to cyclists without. The authors of the study speculate that drivers may assume a greater level of cycling competence, experience, and/or predictability on the part of the helmeted cyclists, and therefore those drivers may pass the cyclists more closely. The article does not indicate that helmeted cyclists are at greater overall risk, nor does it describe any research into this effect.
Incidentally, our article on bicycle helmets seems to be written in a very non-standard essay-like format, and probably should be reviewed. TenOfAllTrades(talk) 22:15, 10 August 2010 (UTC)[reply]
I just tried on my helmet, which I think is a pretty ordinary one, and noted that I can't see any part of it whatsoever while I am wearing it, even with my peripheral vision. Nor does it cover my ears. Looie496 (talk) 22:48, 10 August 2010 (UTC)[reply]
Some helmets come with sun visors, which normally can be snapped off. I think it's a good idea to snap them off — they do make it a bit hard to see forward when you're bent over for a descent, unless you hold your head in a tiring and unnatural position. The downside is that you lose the sun protection, but there's sunscreen and UV-protecting glasses for that. --Trovatore (talk) 22:51, 10 August 2010 (UTC)[reply]
There's some information about research into the benefits and drawbacks of helmets here. The evidence taken as a whole is certainly not clearly in favour of helmet-wearing and may be against. As a regular commuter cyclist I do not own and never wear one. AndrewWTaylor (talk) 18:07, 11 August 2010 (UTC)[reply]
I don't wear one when commuting either, but a person who rides at high speed or down steep hills without wearing a helmet is a suicidal maniac, in my humble opinion. If there is a significant chance of a Close Encounter of the Automotive Kind, I would also very much want to be wearing a helmet. Looie496 (talk) 00:24, 12 August 2010 (UTC)[reply]
In a collision with a car a helmet would be no use at all; they are designed to protect against low-velocity impact. AndrewWTaylor (talk) 20:23, 12 August 2010 (UTC)[reply]
If the car hits you in the head at a high relative speed, maybe the helmet doesn't help. I'm having trouble visualizing how that would happen, though. The more relevant scenario is: Car knocks you down, head hits the blacktop. --Trovatore (talk) 20:27, 12 August 2010 (UTC)[reply]
It's not going to make any difference at a reasonable speed, if a cager hits you there are other things to worry about. When downhill riding a full face and goggles is prudent and reasonable protection.
On the other hand I do wear mine while commuting. I had one incident a while ago where I sideswiped a wall at about 15 mph and given the damage to the helmet I'm glad I had it on, I did break my shoulder though. Also in London it's useful, it's all pretty slow speed but most cages don't leave room and it offers some protection from glancing blows.
Swings and roundabouts, an ex was knocked off by a van and if she'd had a helmet on may well have lost an eye...
The point about visibility or hearing restriction is pretty specious though, if one is riding defensively one should be looking round pretty frequently anyway.
Not going to make a difference because there are other things to worry about? That doesn't make any sense. Sure, the car could run over your chest and put a piece of rib through your heart, and in that case it won't make a difference whether your skull is broken. But in lots of other scenarios it might. --Trovatore (talk) 22:03, 12 August 2010 (UTC)[reply]
If I come off at 20-25mph because a car has hit me from behind I'm more likely to break my neck than get any value from a helmet. Similarly if a car clips me on the way past I'm going to fall into the vehicle rather than away from it, again it's more likely to break my back. Alternatively if I end up on the road in the wake of a car that's hit me, then the one immediately behind will hit me. That's on roads where the cars are doing between 50 and 70 mph.
At any kind of reasonable speed in traffic a helmet isn't going to make a significant amount of difference.
If I compare that to inside London, where the best I'm doing is about 15mph the cars generally aren't passing me so the threat is quite different, so a helmet can help.
Context and threat awareness are pretty significant. I'd say for about 60% of my commute I don't get any value from my helmet.
Do either of you have any studies to reference, or are we working on anecdote and speculation alone here? Algebraist 22:28, 12 August 2010 (UTC)[reply]
The reference above highlights that the evidence is inconclusive, some of the other discussion in CTC material highlights that the value is context dependent. Speed of cyclist and surrounding cages, both relative and absolute, varies the impact of the helmet, with little effect at high speeds.
The majority of work done in the UK focuses on urban accidents, so slow speed and the deaths are usually chest, pelvis or femur related.
I would add that yes, I am informing the interpretation by experience. In 35ish years of regular cycling; commuting, road racing and mountain biking, I don't recall anyone in a high speed hit by motor vehicle incident that hasn't had significant chest, back and arm injuries.
So first, I have to apologize that I hadn't really read your remarks completely before commenting. I do agree that if you get rear-ended by a car doing 70, you're quite likely dead regardless of helmet. But if you get sideswiped by a car doing 70, in my opinion you have a lot better chance with the helmet on. Yes, I agree you're likely to have significant injuries, but that's not the same thing as dead.
As for "the reference above", to be honest that looked like an advocacy site to me. --Trovatore (talk) 21:09, 13 August 2010 (UTC)[reply]
Well, here's from a recent Cochrane Review, PMID 10796827: BACKGROUND: ... Head injury is by far the greatest risk posed to bicyclists, comprising one-third of emergency department visits, two-thirds of hospital admissions, and three-fourths of deaths. ... MAIN RESULTS: ... Helmets provide a 63%-88% reduction in the risk of head, brain and severe brain injury for all ages of bicyclists. ... REVIEWER'S CONCLUSIONS: Helmets reduce bicycle-related head and facial injuries for bicyclists of all ages involved in all types of crashes including those involving motor vehicles.Looie496 (talk) 22:47, 12 August 2010 (UTC)[reply]
Original research - when I used to commute by bike into London, a car overtook me, pulled in and braked sharply. I was coasting downhill at the time, 10-15mph. My front wheel hit his rear bumper, I head-butted his hatchback resulting in a hemispherical dent in the car but no damage to head or helmet. Conclusion - I'm glad I was wearing one! Alansplodge (talk) 17:06, 13 August 2010 (UTC)[reply]
paint stirrers
what are those free paint stirrers made from? are they real wood? —Preceding unsigned comment added by Tomjohnson357 (talk • contribs) 14:06, 10 August 2010 (UTC)[reply]
No, they are just leftovers from cutting real wood. 92.230.233.247 (talk) 14:07, 10 August 2010 (UTC)[reply]
Aren't "leftovers from cuttings [of] real wood" real wood? Regards, --—Cyclonenim | Chat 17:06, 10 August 2010 (UTC)[reply]
No the real wood has been sold as boards, two by fours, what have you. Like sawdust, these stirrers are just what falls to the ground during the cutting. 92.230.233.247 (talk) 17:59, 10 August 2010 (UTC)[reply]
I get where you're coming from, but those cuttings come from the original 'real' wood. So aren't the stirrers, by composition, exactly the same? Perhaps with a few impurities. Maybe I'm just not understanding you properly, I'm pretty slow today. Regards, --—Cyclonenim | Chat 18:08, 10 August 2010 (UTC)[reply]
But then by using that logic, particle board (basically a sawdust-glue mixture pressed flat) could be called real wood. Googlemeister (talk) 18:43, 10 August 2010 (UTC)[reply]
I actually have to agree with Cyclonenim here. If the stirrers are made from a solid piece of scrap wood, they're still 'real' wood by any meaningful usage of the term. Particle board isn't comparable because that's a composite of particles of wood (sometimes not even that but other fibre) held together by a binder. In a similar way, someone may say a meat patty of some sort (burger, meatball, nugget etc) isn't 'real' meat but small pieces of meat which may be scrap and used for a stir fry or whatever is still 'real' meat. Note we have an article on Engineered wood, I'm pretty sure scrap wood of the form described by 92 doesn't fit in to it. In fact, very often people may use scrap wood from a building site or whatever to make things, no one is going to say that isn't 'real' wood. Nil Einne (talk) 19:14, 10 August 2010 (UTC)[reply]
I call [citation needed] on 92.230's claim that paint stirrers are scrap wood. Looking at sites like this, it's clear that they're sawed and shaped in bulk, which does not scream "scrap wood" to me. Comet Tuttle (talk) 18:44, 10 August 2010 (UTC)[reply]
Have to agree with CT here. See also [16][17][18] these Chinese sellers. Don't exactly scream 'scrap wood' to me either Nil Einne (talk) 19:30, 10 August 2010 (UTC)[reply]
Paint stirrers are solid wood, made by splitting a billet of pine or other soft wood parallel to the grain, since sawing them would waste about half the wood. High quality billets of wood are used, not pieces full of knots, since those would break. The wood needs to be of high quality, but the pieces could be short lengths, I suppose. I have never seen or heard of a paint stirrer made of any sort of composition of sawdust and glue. As for "free," their retail value in the US would be about 10 cents each, if you wanted to buy a bunch (like for a craft project, or for labels for garden plants, or whatever) and weren't buying any paint. Edison (talk) 14:57, 11 August 2010 (UTC)[reply]
Transforming a principal stress tensor to maximum shear stress tensor?
The author re-posted the question to the Mathematics Reference Desk, which was the more appropriate Desk. See HERE. Dolphin(t) 22:50, 10 August 2010 (UTC)[reply]
Chemistry/Software question
This is kinda science related and also software-related, but I reckon the people who are best to answer it are at this desk rather than the computing one. Are there any open source/freeware programs that do the same job as the FULL ChemSketch? Personally I can't afford to buy the program and I don't want to resort to illegality in getting it. Regards, --—Cyclonenim | Chat 17:09, 10 August 2010 (UTC)[reply]
List of software for molecular mechanics modeling has a list; you might want to make a list of specific features you need (many on that list are computational molecular dynamics tools, with "sketching" or 3D image rendering as just a side-benefit). The article molecule editor has a less-well-organized list, but may be more what you're looking for. List of molecular graphics systems, too. I think we might need to consolidate (or just organize) these articles. Nimur (talk) 18:24, 10 August 2010 (UTC)[reply]
What is a tensor?
I read the article on it, but I'm still not sure what it even is. In layman's terms? 148.168.127.10 (talk) 18:32, 10 August 2010 (UTC)[reply]
I struggled with these at university and only got them the third time round. If you understand vectors, then that's a start as they are 1st order tensors (I'm going back a few decades here so others will I'm sure correct me if I'm wrong). Some physical things such as stress and strain need 9 'components' to fully describe them and for elasticity, which relates stress to strain, you need 81 components and that's a 4th order tensor. As the tensor article says, the stress tensor (2nd order) describes the relationship between two vectors (1st order tensors). I doubt that helps, as it's very difficult to describe this in laymen's terms, but good luck anyway. Mikenorton (talk)
Not the OPHow would that make them not vectors? Can't vectors have an arbitrary number of components? 82.24.248.137 (talk) 21:35, 10 August 2010 (UTC)[reply]
Well, they are vectors in some sufficiently abstract sense. But that doesn't really say much — it just says you can add them and multiply them by scalars, and the normal obvious things happen.
The general question "what is a tensor?" is probably not going to have a really satisfying answer right now. You could say that it's a linear transformation from some power of a vector space to some power of a vector space, but I don't think that really gives the sort of intuition you're asking about.
Instead, I'd recommend studying some particular simple tensors, preferably of rank 2. The stress tensor is a good one — think of it as a rule that takes a little flat piece inside the object (which you can think of as a vector, with magnitude equal to the area of the piece and direction perpendicular to the piece), and returns a vector representing the force through that piece. Figure out why that's a linear transformation (hardly obvious!) and you've got a start.
A tensor, in the simplest possible terms, is a multidimensional matrix attached to a point in a multidimensional space, with the numerical entries in the matrix changing in specified ways when the coordinate system for the multidimensional space is altered. Looie496 (talk) 22:33, 10 August 2010 (UTC)[reply]
Those might be the simplest terms in some sense, but they're not the most illuminating ones. Better to emphasize coordinate-free formulations. --Trovatore (talk) 22:38, 10 August 2010 (UTC)[reply]
The tensors that show up in physics are usually either symmetric or antisymmetric. I don't know if "layman's terms" includes calculus, but both of these special classes of tensors are probably best thought of in calculus terms.
A symmetric rank-n tensor is what you get when you generalize nth derivatives to functions of more than one variable. The first derivative of a real-valued function of real variables is a vector (rank-1 tensor), called the gradient, whose components are (∂f/∂x, ∂f/∂y, ...). The second derivative is a matrix (rank-2 tensor) called the Hessian. It's a symmetric matrix because the order in which you take partial derivatives doesn't matter. In the case of a function of one variable, you get a one-component vector and a 1×1 matrix whose sole component is the usual first or second derivative. The most useful thing to know about symmetric real matrices is the spectral theorem, which says that you can always make the matrix diagonal by some orthonormal change of basis variables. Thus you can think of a symmetric rank-2 tensor as a set of perpendicular coordinate axes (the diagonalizing basis) with a number (the corresponding element on the diagonal) attached to each axis. These axes are sometimes called "principal axes". In terms of the original scalar function, what this means is that every smooth surface can be approximated locally to second order by an ellipsoid (just as it can be approximated locally to first order by a plane).
An antisymmetric rank-n tensor is a differential form, which is the thing that you write after an n-dimensional integral sign. For example, f(x,y) dx dy is a differential 2-form. In matrix form it would look like , assuming three dimensions with x and y the first two. It's antisymmetric because dx dy represents a little parallelogram in space (the "area element"); if you swap dx and dy the area element flips over, changing its sign, and if you make dx and dy the same vector it collapses to zero size. dx dy is more properly written , where is the wedge product, which is this case is the same as the 3D cross product. The number of independent components of an antisymmetric tensor is given by entries of Pascal's triangle. In three dimensions antisymmetric tensors of rank 0, 1, 2, 3 have 1, 3, 3, 1 components respectively, and they are scalars, vectors, pseudovectors, and pseudoscalars respectively. In four dimensions the tensors of ranks 0...4 have 1, 4, 6, 4, 1 components. The first two are scalar and vector and the last two are pseudovector and pseudoscalar. The middle one, in 3+1 spacetime dimensions, can be decomposed into a 3D vector and a 3D pseudovector. This is how the electromagnetic field tensor decomposes into electric and magnetic field vectors. There's more that could be said about antisymmetric tensors, but I'll leave it at that. -- BenRG (talk) 06:00, 11 August 2010 (UTC)[reply]
Higher order tensors simply seem like "vectors of vectors" to me. Have you taken multivariable calculus yet? John Riemann Soong (talk) 18:28, 11 August 2010 (UTC)[reply]
satellites.
Have we (humans) placed any satellites that are in retrograde orbit around anything besides earth? Googlemeister (talk) 19:04, 10 August 2010 (UTC)[reply]
Yeah I looked at that article and thought the same thing, especially since it would require a massive energy expenditure around any extraterrestrial body I can think of except perhaps Venus. Googlemeister (talk) 19:18, 10 August 2010 (UTC)[reply]
No, I don't think so. For Earth, where you get the rotation speed for free (or have to compensate for it), the difference is major. But for any other body, the rotation of the body is irrelevant - you're dropping in from outside the system, anyways, and, as long as the rotation is not relativistic, the other body simply behaves as a point mass. You can essentially chose any orbit you like. I would suspect that probes often chose a polar orbit, since that allows them to map the whole body over time. --Stephan Schulz (talk) 21:25, 10 August 2010 (UTC)[reply]
Plus, craft that we put in orbit about other bodies are either doing scientific/photographic missions or dropping off landers - and the lower the relative speed between surface and orbiter, the sharper the photos can be and the lower the re-entry speed of any lander. Using a retrograde orbit would pretty much guarantee worse results. SteveBaker (talk) 02:48, 11 August 2010 (UTC)[reply]
Most intelligent bird
Can you tell me which bird species is generally considered to be the most intelligent in the world? --95.148.105.77 (talk) 21:01, 10 August 2010 (UTC)[reply]
Corvidae are generally considered the most intelligent bird species family, for the reasons (and sourced ones at that) presenting in the introduction to the article. You may also enjoy reading bird intelligence. Regards, --—Cyclonenim | Chat 21:09, 10 August 2010 (UTC)[reply]
Corrected, it's a family of birds rather than an exact species. It'd be hard to pinpoint between the species within the family for they are specialised at different things. Regards, --—Cyclonenim | Chat 21:11, 10 August 2010 (UTC)[reply]
Grey Parrots are recognized for their cognitive language skills, though ravens are very good at solving problems and can count to 6 or 7. Googlemeister (talk) 21:25, 10 August 2010 (UTC)[reply]
I would like our questioner to tell us what he or she thinks intelligence means, especially in birds. We have enough trouble agreeing on what it means for humans. When we try to apply the concept to totally different creatures it becomes very difficult to agree on what it means. HiLo48 (talk) 21:32, 10 August 2010 (UTC)[reply]
The smartest corvid would make for a dumb human. But at the same time, the smartest human would make for a dumb corvid. HiLo48 is right. Perhaps all you can say is that, amongst the various kinds of birds, the corvid's intelligence is most similar to human intelligence.91.104.151.200 (talk) 00:12, 11 August 2010 (UTC)[reply]
I remember a story from a few years ago in which a bird was able to form a hook out of a piece of wire then use it to retrieve some food at the bottom of a container, a behavior previously unobserved. I don't know what the species was, though. Hemoroid Agastordoff (talk) 17:00, 11 August 2010 (UTC)[reply]
Our article on this effect includes a short bit of discussion about individuals who previously recognised this effect. Would it be reasonable to say that Socrates observed this effect, since according to legend he was told that he was the wisest of all men because he knew that he wasn't wise? Nyttend (talk) 02:13, 11 August 2010 (UTC)[reply]
I don't think we could say that with confidence about someone who lived 2500 years ago. SteveBaker (talk) 02:44, 11 August 2010 (UTC)[reply]
Why not? I don't see the difference, especially since the article includes those who remarked about the phenomenon before Dunning or Kruger were born. Nyttend (talk) 04:57, 11 August 2010 (UTC)[reply]
"according to legend" - nuff said. Note that if you are trying to add it to the article, you should be discussing it in the article talk page not here. Presuming other sources have made the connection you may be able mention that, it doesn't mean we can say with confidence Socrates observed the effect which is a quite different thing.
I would also note your statement doesn't really support the claim at all since you say "he was told that he was the wisest of all men because he knew that he wasn't wise" which would suggest someone else recognised this effect not Socrates. Whether Socrates even recognised the effect once told about it or whether he thought the person who said he was the wisest of all men because he knew that he wasn't wise was an idiot is not even clear from what you've described.
Notice the banding? Does anyone have any idea what might be causing that banding? It's not just a photographic artifact (though it may be not faithfully recreated by the camera); I took the picture because I noticed the banding with my eyes. At the bottom is obviously a cloud in front of the sun, but on the other half of the sun, there's nothing obvious to cause the interesting coloring. It was taken August 5th in southern Minnesota, if that makes a difference. Buddy431 (talk) 02:38, 11 August 2010 (UTC)[reply]
My guess is that the photograph was taken on a day when there were numerous layers of diffuse cloud and strata of humidity, perhaps enhanced by strata of pollutants. The photograph was taken when the sun was in such a position that it was observed through a number of these strata. As a result, the color of the sun was affected by the various strata in the atmosphere and so the sun shows distinct bands. It would be useful to take a few more photographs with the sun at the same elevation, both in the morning and in the evening. I wouldn't be surprised if the bands are only a rare observation. Dolphin(t) 03:15, 11 August 2010 (UTC)[reply]
I don't think this is rare. I'm seeing lots of air pollution in that image, possibly smog or smoke from a wildfire of some kind. The temperature also appears to be above 30 C based on news reports in that region. Although there was a small fire in that area in the morning the photograph was taken, smog is a known problem during the summer, with local reports blaming gas-powered lawn mowers, in addition to wood fires, ATV's and cars. Viriditas (talk) 04:00, 11 August 2010 (UTC)[reply]
It's probably due to different layers of atmospheric thickness and relative humidity, as the lower layers may have more particulate matter that turns the Sun red. It might be related to the green flash. ~AH1(TCU) 15:49, 11 August 2010 (UTC)[reply]
More finds
Salamander in question
These small salamanders are found under slabs of rock within several feet of a stream. What are they? They are very common. Most of them have the stripes down the back. --Chemicalinterest (talk) 13:03, 11 August 2010 (UTC)[reply]
According to this document [20] from the New Jersey (I assume the NJ on your image is that) Department of Environmental Protection, etc. etc., there are 14 or 15 different species of salamander and several of them have stripes. There is a gallery of photos at the bottom of the document. Richard Avery (talk) 15:40, 11 August 2010 (UTC)[reply]
Thanks for the document. The specs seem to indicate this species. --Chemicalinterest (talk) 17:02, 11 August 2010 (UTC)[reply]
Reverberation
Lets say I'm voice chatting on my computer using skype or something. And I while we are chatting, I can hear my voice on the other person's computer. Would this "echo" be described as reverb? 148.168.127.10 (talk) 13:24, 11 August 2010 (UTC)[reply]
I don't think so. It's audio feedback, isn't it? The reverberation article seems to indicate it applies to echoes only. That is, I think feedback would be disqualified because it uses new sources of sound (the speakers) rather than a reflection of the original sound. Vimescarrot (talk) 13:59, 11 August 2010 (UTC)[reply]
I concur that "reverb" isn't really applicable, and that "audio feedback" is probably accurate. If you want a reverby sort of word, though, it's a retrans. 199.209.144.218 (talk) 14:14, 11 August 2010 (UTC)[reply]
There are two forms of echo in Telephony: Near-end echo has no delay and is desirable in a small amount as a Sidetone so the telephone does not seem "dead" to the user. Far-end echo is echo of one's own voice delayed; it is undesireable and may be caused electrically by a poorly balanced Telephone hybrid or by acoustic link between the far telephone speaker and microphone. The OP is hearing far-end echo. Cuddlyable3 (talk) 16:31, 11 August 2010 (UTC)[reply]
In my experience "reverb" is used to describe a reverb-y sound regardless of source. So, if the end result is a reverb type sound, then yes, I suspect people would call it reverb. Friday(talk) 16:38, 11 August 2010 (UTC)[reply]
why do mockingbirds open their wings repeatedly while searching for bugs in the grass?--Horseluv10 13:27, 11 August 2010 (UTC) —Preceding unsigned comment added by Horseluv10 (talk • contribs)
I'm not sure that anyone knows the answer to that yet and I don't think it's really covered in Wikipedia which is a pity. There seem to be all sorts of theories e.g. it enhances their foraging by surprising the insects..somehow, anti-predator defense, territorial defense etc or maybe all of the above and more. Other mimids do it too. Sean.hoyland - talk 14:01, 11 August 2010 (UTC)[reply]
It may be because they are shading the ground for better visibility. 92.28.244.237 (talk) 09:51, 12 August 2010 (UTC)[reply]
Actually the opposite of shading has also been proposed as another explanation i.e. the exposure of bright white patchs during wing flashing illuminates prey. That theory is slightly ruined by several mockingbird species without white patchs flashing their wings while foraging... Sean.hoyland - talk 10:06, 12 August 2010 (UTC)[reply]
Phage therapy
After reading phage therapy, including the obstacles section, I don't see a reason for why phage therapy is not licensed for medicinal use in Western countries like the U.S. and the U.K., especially given the ever-rising resistance against traditional antibiotics. Safety is a slight concern, though it's generally considered safe under supervision to look out for toxic shock. I'm guessing it has something to do with the practicality of having to develop very specific strains of phages. Is this uneconomical at present? Regards, --—Cyclonenim | Chat 15:03, 11 August 2010 (UTC)[reply]
Did you read the article you linked to? Phage therapy is not as well structured as it could be, but there are several points in it that explain why the therapy is not in wide use: The patient mounts an immune response against the phage, so you probably can use every phage only once. You have to know very specifically what kind of bacteria (or even mix of bacteria) has infected the patient, which is impractical as of now (that could change if sequencing costs keep dropping). Another point, which is not raised in the article I think, is that antibiotics are very cheap, and phages are not, at the moment. With multiresistance on the rise, the picture could change, but at the moment, phage therapy does not seem to have an advantage over antibiotics. --TheMaster17 (talk) 11:52, 12 August 2010 (UTC)[reply]
Thanks, I did read it but I only skimmed through it really. Even if you can only use each phage once in each patient, that doesn't seem like a massive reason not to use phage therapy. For example, certain rarer infections that people are only likely to get once could be treated by phage if not by antibiotics. Fair point regarding costs, I suspected it'd have something to do with that too. Regards, --—Cyclonenim | Chat 12:12, 12 August 2010 (UTC)[reply]
Mnemonic for functional groups in IUPAC nomenclature
Is there any mnemonic by which i can memorize the priority order for functional groups used while naming carbon compounds in IUPAC nomenclature?? harish (talk) 16:57, 11 August 2010 (UTC)[reply]
I don't know of one, but perhaps other people have come up with an idea for the more common ones at least! The full list is very long, and includes functional groups that most chemists will never have to deal with: on a practical, professional level, it's something you look up if you need it rather than keep in your head at all times. Physchim62(talk) 17:13, 11 August 2010 (UTC)[reply]
Could you start us with a list of the ones you need to know? DMacks (talk) 17:57, 11 August 2010 (UTC)[reply]
If your professor is making you do this for an exam, he/she is horrible. This sort of thing is something that's best left to experience, not study. John Riemann Soong (talk) 18:24, 11 August 2010 (UTC)[reply]
carboxylic acids, sulphonic acids, acid anhydrides, esters , acid chlorides, amides, nitriles & isocyanides, aldehyde, ketone, alcohol, amino, C to C double bond, C to C triple bond, halogens=nitro=alkoxy=alkyl. I am just now in eleventh grade, so these few important groups will do. If there's some error in my order, please correct it too. thanks harish (talk) 12:21, 12 August 2010 (UTC)[reply]
Sexual Behavior in the Human female
where can i read the full version of Sexual Behavior in the Human female by kinsey. preferable online. —Preceding unsigned comment added by Tomjohnson357 (talk • contribs) 17:09, 11 August 2010 (UTC)[reply]
This seems like a fairly complete version: the book is under copyright, so I doubt you'll do better (apart from asking for it at your local library). Physchim62(talk) 17:18, 11 August 2010 (UTC)[reply]
Fixed a typo, hope you don't mind. Regards, --—Cyclonenim | Chat 17:22, 11 August 2010 (UTC)[reply]
Page 14 says that abstinence education turns youths into homosexuals! Comet Tuttle (talk) 19:46, 11 August 2010 (UTC)[reply]
(EC). There is a version on Google Books which I guess you've already found since it's the first Google result for 'Sexual Behavior in the Human female'. It isn't complete as the book appears to still be in copyright in the US where you live and likely other countries. Therefore the only place you're likely to find a complete non copyright violating copy online is on somewhere that sells ebooks (where you'll have to pay) but a quick search suggests it isn't available in such form. It should go without saying you won't receive any help here to violate copyrights. If you aren't desperate for an online copy, you could try a library Nil Einne (talk) 17:23, 11 August 2010 (UTC)[reply]
are there any ebook sites where i could pay to get the full version? --Tomjohnson357 (talk) 17:48, 11 August 2010 (UTC)[reply]
Well as I said above, I can't find evidence of any. Unfortunately there are still quite a lot of books which for a variety of reasons aren't available in legitimate ebook form Nil Einne (talk) 18:46, 11 August 2010 (UTC)[reply]
Buoyancy
I'm trying to calibrate my intuition about how buoyancy should work with a small amount of a fluid.
For example, consider the case of a large boat in a small lock (water transport). Archimedes' principle is that the boat needs to displace an amount of water equivalent to its weight in order to float. The boat can do that, but the lock is small enough that the amount of water remaining in it is going to weigh significantly less than the boat. Shouldn't the boat sink to the bottom, like a heavy weight overwhelming a light one on a balance beam? But then it seems like it would matter whether the lock is connected to a larger body of water, which would imply that when the door was closed off, the boat could suddenly sink - and that seems crazy.
So is there an intuitive explanation of why the amount of water surrounding the ship doesn't matter (if that's the case) which could be added to the article? This seems counter-intuitive given the pulley analogy used there. -- Beland (talk) 17:26, 11 August 2010 (UTC)[reply]
The quick-and-dirty thought experiment is easy: imagine the boat sailing up the canal and into the lock. While the lock's gates are open, the boat is floating in the entire volume of the river, so no problems. When the gates close, sealing the lock off from the rest of the river, it doesn't make any sort of intuitive sense for the boat to immediately sink, right?
The slightly longer explanation involves looking at the situation from an energy standpoint. Imagine a container that surrounds both boat and water, with the boat afloat. Now, think about what happens if you move the boat down into the water by a little bit. The layer of water that was sitting happily under the boat's hull gets pushed aside, and an equal volume of water (ignoring the very slight compressibility of water) gets pushed up to sit on the old 'surface'. Effectively, that layer of water has been lifted from under the boat up to the water's surface; doing that work takes energy. Now where would that energy come from? If the boat spontaneously sank when you closed the lock's gates, you'd be getting energy for free if the boat immediately sank and lifted up that water into the air. TenOfAllTrades(talk) 17:40, 11 August 2010 (UTC)[reply]
Taking a slightly different tack, the flaw in your scenario is that you're assuming a constant volume of water in the lock, and that's not correct. There may be a particular volume of water in the lock when it's closed and has no boat, but you don't put the boat in the lock in that state. Instead, the boat enters when the lock is open and part of the larger system. As Ten notes above, this is the boat floating in the whole river -- that works just fine. When the lock closes, though, the volume of water inside has already changed due to the boat, river, and everything else.
Of course, the problem I'm having with this is that the scenario of "too little water" seems unlikely. If there's not enough water in the closed lock to float the boat (and assuming that water level matches that of the river), then the boat is also too big for the river. Adding the boat's displacement to the lock makes the water level rise, not fall, and so the initial water amount isn't the limiting factor. Instead, it's merely whether or not the boat (a) floats at all and (b) floats in the depth of water available. — Lomn 18:46, 11 August 2010 (UTC)[reply]
Assume that pressure is constant throughout the water. The pressure of water against the boat, and hence the nett upward force of buoyancy (see article), is the same whether the water volume is unbounded, i.e. in open sea, or bounded by lock walls that almost touch the boat. Cuddlyable3 (talk) 18:59, 11 August 2010 (UTC)[reply]
I think the OP's intuition is correct, it's just that the quantity of water that counts as "small" is not well-defined. Consider the extreme cases on both ends:
Lots of water (entire river) - boat floats. No problem, intuitively.
Extremely tiny quantity of water - say, a "puddle" that's only an inch deep. The boat will displace all that water under it, and raise the water level, but will hit the bottom before it has displaced enough water to counterbalance its weight. There is no way one inch of water will be able to float the boat (unless we consider an extremely tight fit between a boat and a canal with tall walls - then a tiny fluid-layer bearing would exist between the boat and the very closely-spaced walls of the canal).
In the intermediate cases, the boat must displace a volume of water such that the water-mass is equal to the boat-mass. But displacing water means moving water from under the boat to the sides of the boat. This can only work if the geometry of the water container (lock, river, etc.) is sufficient so that necessary water-volume can be moved to the side before the boat hits the bottom of the container (lock/river/lake/etc.) If the amount of water is very small, the boat does hit the bottom. The draft of a boat is the geometric parameter that defines this. Boats can not sail in (locks, rivers, canals) that are shallower than their own draft. Nimur (talk) 20:37, 11 August 2010 (UTC)[reply]
The scenario isn't clearly described. What do you mean by the amount of water remaining in the lock? Are you assuming that the water goes out of the lock after it has been displaced, perhaps by pouring over the gate? If so, then the boat will indeed sink to the bottom. If not, please clarify what you meant. Looie496 (talk) 00:16, 12 August 2010 (UTC)[reply]
The amount of water remaining in the lock is irrelevant, as is any open or closed connection between the lock and a larger body of water. All that matters is the notional weight of an amount of water that has the same volume as the submerged volume of the boat. As long as this is equal to the weight of the boat then the boat will float, even if it takes up more than half of the volume of the lock. If the boat floats in the river then it will float in the any lock that is long, wide and deep enough to accommodate it. Gandalf61 (talk) 14:41, 12 August 2010 (UTC)[reply]
I was thinking more in the opposite direction -- if the lock is closed, the boat can float in less depth than it would normally take, because the water it displaces, having nowhere to go, may raise the water level. I'm not certain this is relevant to the question, but then I didn't really understand the question very well. Looie496 (talk) 21:35, 12 August 2010 (UTC)[reply]
Yes, Looie496's intuition is correct. In a lock or other "container" that has a "boat-shaped" profile, the boat can still float even though it has "displaced" less water than its own weight. The critical weight is that of the "submerged volume" of the boat, not the actual amount of water physically displaced (i.e. moved). The normal statement of Archimedes Principle is not quite correct in this respect. The upthrust is actually equal to a weight of water equivalent to the submerged volume, regardless of the amount of water physically displaced. Archimedes was right, but he was measuring overflow when he thought of water "displaced". See the first note in the Buoyancy article. Dbfirs 08:48, 13 August 2010 (UTC)[reply]
I'll just throw one more link to fluid bearing. It is possible to completely support the weight of an object using a very tiny quantity of fluid - but the parts must be almost perfectly identical in geometry. Nimur (talk) 16:43, 13 August 2010 (UTC)[reply]
Mercury bowl and float. (Split Rock Lighthouse)One example is the use of mercury bowl and float type bearings for the heavy Fresnel lenses of lighthouses which use much less mercury than they "displace". -- 1.46.122.77 (talk) 00:27, 14 August 2010 (UTC)[reply]
Toxins
Can people have a gene that creates a toxin in our body? In other words is there genes that can make a toxin in our bodies? —Preceding unsigned comment added by 71.154.146.52 (talk) 17:41, 11 August 2010 (UTC)[reply]
I'd imagine that any gene creating a toxin with a significant effect on our bodies would have been eliminated from the gene pool. If it's a lethal toxin, everyone with it dies, and assuming this happens before they reach reproductive age (which it would, in all likelihood) then there would be no way to pass this gene on. Regards, --—Cyclonenim | Chat 17:50, 11 August 2010 (UTC)[reply]
Many toxins are produced within the body. Ammonia, for example. But a healthy human body has mechanisms for properly filtering them out again before they reach dangerous levels. APL (talk) 18:30, 11 August 2010 (UTC)[reply]
You're not talking about NDM-1, a recently-discovered gene-crossing enzyme that can cause bateria including those that infect humans to become antibiotic-resistant, by any chance? ~AH1(TCU) 18:54, 11 August 2010 (UTC)[reply]
A gene that coded for a toxin directly wouldn't last long, since it would kill the host before they could pass it on. We have genes that produce enzymes that can produce toxins, though. For example, alcohol dehydrogenase will produce formaldehyde (which is very toxic) out of methanol. That is why methanol is dangerous. Methanol itself doesn't do much (it would get you drunk if you drank enough of it, but that's it), but it gets converted into something that does a lot of harm. (Alcohol dehydrogenase does a helpful job dealing with ethanol (drinking alcohol) and just tries to do the same thing with methanol, which turns out to be a bad idea.) --Tango (talk) 19:45, 11 August 2010 (UTC)[reply]
Several waste metabolic substances are poisonous if re-digested, such as undiluted urea. Does the immune system, in response to an pathogen, produce poisons at a sufficient level to subdue the pathogen, but not to seriously affect our own health. If so, can this process over-react and kill us? CS Miller (talk) 22:22, 11 August 2010 (UTC)[reply]
The immune system doesn't produce anything that is harmful to us. It produces antibodies but these are harmless to us, they merely seek out the pathogen. So no, it can't. Regards, --—Cyclonenim | Chat 22:29, 11 August 2010 (UTC)[reply]
I'd say "shouldn't" instead of "can't" and I'd cite Auto-immune disorder as my argument. The question is "can people have a gene", if there is such a thing as a gene that codes for toxin, I'd say it is possible, even if it is a disorder or mutation. If the question was "is it normal for a healthy person to have such a gene?" that's a different question. I think it's a little too simplistic to say "it would get selected out", why aren't ALL genetic disorders already "selected out" a long time ago? The subject is obviously a lot more complicated then some of the answers here suggest. Vespine (talk) 23:56, 11 August 2010 (UTC)[reply]
But auto-immune disorders are where your body attacks itself, it doesn't relate to pathogens. Your body can't ever poison itself when it tries to kill a pathogen. As for why all genetic disorders don't get selected out, that's very simple. The diseases which don't kill you or significantly prevent you mating can still be passed down. If a gene codes for a toxin (by definition something that causes harm and can eventually kill you) then the chances are that it will kill you before you reach reproductive age. Regards, --—Cyclonenim | Chat 00:04, 12 August 2010 (UTC)[reply]
I'm not sure I understand your 1st argument, how does your body "attack itself" if not almost precisely the same way it attacks a pathogen? I also don't believe your 2nd statement. Down syndrome is one of the most common genetic disorders, before modern medicine very few people with down syndrome would have lived long enough, or had the opportunity to procreate. Even today there would be very few people with down syndrome who become parents. I don't think toxin means it has to kill you, how about organisms that actually produce toxins? They have a gene that codes for it in their body right? What if you co-evolve a resistance to the toxin, isn't that what snakes do? Vespine (talk) 05:18, 12 August 2010 (UTC)[reply]
Well, your immune system can sort of kill you in response to an infection. See toxic shock syndrome. I say "sort of" because in TSS the infection is using its own toxin to trick your immune system into triggering global vasodilation so it can permeate all of your tissues. As for the original question, I don't think there's really much possibility of a meaningful answer. Too much of anything is bad for you. Tay sachs, phenylketonuria, while described as your body lacking something good, actually kill you through a buildup of compounds the body produces itself. Heck, too much water will kill you. Someguy1221 (talk) 05:34, 12 August 2010 (UTC)[reply]
@Vespine, when I say the body attacks itself, I mean it does so independently of any infection. Yes, sometimes, it attacks itself via the same mechanism it would a normal pathogen, but it is independant of such a pathogen's presence. The statement above my post is referring to 'when a pathogen is in our body, can we kill it off and have a detrimental effect on our bodies'. Strictly, the answer is no. There is no direct poisoning of our bodies through our own natural defenses. However, as Someguy just noted above me, toxic shock syndrome can occur, but that isn't directly a result of our own bodies. That's limited to where bacteria have toxins to trigger vasodilation. In response to your Down syndrome comment, I contest that anyone with Down syndrome would not have been able to live long enough to procreate. Down syndrome sufferers do not take any medication to prolong their lives. In fact, they have an average lifespan of around 50 years - which is more than long enough to procreate if they could. But they can't usually, and if they do it makes things more severe for the children. You assume that all diseases are simply passed down like other hereditary traits - it isn't true. Downs syndrome caused by a nondisjunction event where chromosomes fail to separate, so in that sense it's pretty much a random and rather unfortunate occurrence. Oh, did I also mention that pretty much all Downs syndrome males are infertile, and that women are often much less fertile than those without the disease? This is proof that it isn't a hereditary condition, because there wouldn't be anyone with it if it was! To address your last point, I don't really understand but I'll have a go, clearly if you develop a resistance to a toxin then that's great. You may have noticed though that we haven't. Snakes can still kill us, toxin-producing bacteria can kill us, deadly insects can... well, you get the point. We haven't "co-evole[d] a resistance" to any particular toxins other than the ones we have enzymes to digest. Seriously. Toxin infers that it's deadly or at least seriously harmful to chances of survival. Regards, --—Cyclonenim | Chat 08:09, 12 August 2010 (UTC)[reply]
Sorry, as an immunologist I have to completely disagree with Cyclonenim. First point: Where are the references for you bold claim that pathogens have nothing to do with autoimmunity? The true reasons for autoimmunity are not known, but one of the hypotheses that are discussed, at least for some forms of autoimmunity, is exactly the triggering by foreign antigens. These could just be "normal" allergens in the environment, but there's no reason why the defense against pathogens shouldn't be able to have the same effect (because pathogens bring a large pack of antigens with them). Next point: We are talking here about complex concepts. "Poisoning" and "Toxin" are not well defined. As someone else has pointed out, the dosis and entrance point of a substance are critical: Two molecules of a highly "toxic" bacterial protein won't kill me in my food, but if I drink some liters of pure water quickly, I will die. And what do you mean with "antibodies are harmless"? They are one of the deadliest mechanisms that our body has in its arsenal, because the adaptive immune system is constantly "evolving" to make them more and more effective. And only because we have intricate checks build into our immune system, this "weapon" does not harm most healthy humans. But in every person's blood, there are small amounts of autoreactive antibodies, because the control systems are leaky. So the exact same mechanism that destroys pathogens is constantly producing "toxic" substances. Another thing that goes into the same direction: Our macrophages use very toxic compounds, which they even store for later use, to kill other cells that they engulfed (for example reactive oxygen species and proteins that are capable to cut other proteins). In some cases, when the macrophage is unable to kill the intruder, the reaction gets "out of control" and even kills the macrophage and/or bystander cells (because both are not immune against reactive oxygen, for example).
And in addition, coming to the snake example, there are certainly snakes that are not immune to their own poison. They are only unaffected by their poison because the snake normally only produces and stores it in special organs, so it doesn't get a chance to get into the blood.
Coming back to the original question, I'd say that there's nothing in principle that could stop a gene producing a poison from working (look at all the poisonous pests around us). But as you specifically asked for people, it is unlikely that such a gene would "just show up" in a person. Humans have no use for poison, so there's no selection pressure in this direction. And complex traits as "poisonous" do not just spring into existence, they have to evolve step by step, and every step has to have a slight advantage over the previous one (or at least be neutral). --TheMaster17 (talk) 10:09, 12 August 2010 (UTC)[reply]
To summarize: "Can people have a gene that creates a toxin in our body? In other words is there genes that can make a toxin in our bodies?" Yes, we can and we do. Our immune system generates powerful weapons against microbes. One example is reactive oxygen species that are generated in neutrophils and macrophages. The gene encoding NADPH oxidase is responsible for the production of these molecules. --- Medical geneticist (talk) 12:24, 12 August 2010 (UTC)[reply]
Bacon crisps state 65g protein/100g
Dear Wikipedians, I was just at the store. There I browsed for some crisps/potatoe chips, and came upon a curious find: A Norwegian crisps company called Maarud sells "Bacongull" (Bacongold), and states 65g of proteins per 100g serve; 26.5g fat. Those 65g are normally carbohydrates, at least between 40-60 of them.
Am I eating some clever form of proteinized carbohydrates? Thank you in advance. 88.90.16.109 (talk) 17:42, 11 August 2010 (UTC)[reply]
You are entirely in the right. These aren't crisps at all. Excuse me... 88.90.16.109 (talk) 18:42, 11 August 2010 (UTC)[reply]
Cold bottles freezing
Is it true there are cases when getting cold water in a closed bottle out of a fridge would cause it to freeze suddenly when opening? If yes, then how can we explain this phenomenon?--Email4mobile (talk) 18:34, 11 August 2010 (UTC)[reply]
The phenomenon is supercooling, and it (as well as related phenomena like superheating) results from a lack of nucleation sites on the container. — Lomn 18:36, 11 August 2010 (UTC)[reply]
The trick here is that the fridge is too cold and is cooling the water to just below freezing, but the pressure in the bottle is stopping it from actually freezing. Release the pressure and ... bang, it freezes like magic about two seconds after you open the bottle. APL (talk) 18:59, 11 August 2010 (UTC)[reply]
(ec) Water freezes at a temperature below 0 °C under a pressure higher than 1 atm (0.10 MPa). Therefore liquid water in a bottle under pressure could freeze when the bottle is opened. Cuddlyable3 (talk) 19:08, 11 August 2010 (UTC)[reply]
I can find the pressurized bottle effect makes sense in some pressurized liquids, but not sure if water bottles are pressurized too since we expect vapor pressure to get lower as well by decreasing temperatures inside the fridge. --Email4mobile (talk) 19:30, 11 August 2010 (UTC)[reply]
A few years ago I had a habit of putting a 1 liter bottle of water in the freezer before going on my lunch break (1 hour). Upon returning, I retrieved the bottle and was able to observe the effects of supercooling by tapping the bottle with my fingertip. Hemoroid Agastordoff (talk) 16:43, 13 August 2010 (UTC)[reply]
My lab group just called this process whenever it occurred apoptosis but they're chemists (though they are branching out into the biology side), not cell biologists. Is autophagy a more accurate description? I don't see a description of these very visible bubbles in the apoptosis article.
This occurs whenever the cell culture is about to die on the microscope slide after having been on the slide for too many hours, at room temperature, without the 5% carbon dioxide atmosphere. John Riemann Soong (talk) 19:45, 11 August 2010 (UTC)[reply]
(I notice that the images in each of these articles are either cartoony or not very vivid, so I want to include this photo in one of the articles, but I don't know which one is appropriate.) John Riemann Soong (talk) 20:45, 11 August 2010 (UTC)[reply]
Pardon me, but you seem to have been putting these types of photos up and asking extremely detailed questions regarding cell structure and function, the likes of which can probably only be answered by individuals with such highly specific training that you are unlikely to receive a good response on the ref desk. Good luck, though! DRosenbach(Talk | Contribs) 20:47, 11 August 2010 (UTC)[reply]
Can you even tell which it would be from this photo? I was under the impression that either footage or a series of pictures over time is/are needed to determine which type of PCD is happening. Can't you tell which type is happening by observing what features degrade first? In autophagy, the nucleus should go towards the end. I also agree with DRosenbach above. These questions are pretty complicated and I'd take a guess that people at your University (in the biological and medical departments) may be better off answering your questions. Regards, --—Cyclonenim | Chat 21:29, 11 August 2010 (UTC)[reply]
Well I'm very familiar with the bubbling process. I've watched it happen like a million times. People identify very peculiar and specific insects I've never heard of all the time, so why not something as basic as a fundamental cellular process? Anyway, the nucleus takes a while to degrade -- the bubbles appear first -- before the cell blebs. Over time these bubbles can "take over" the cell. I'm not sure if apoptosis is triggering the hypothesised autophagy or vice versa. I think it this process is a consequence of nutrient or oxygen starvation.
Should I be bold and just put this photo in the autophagy article? John Riemann Soong (talk) 21:35, 11 August 2010 (UTC)[reply]
Perhaps have a go at posting it at one of the WikiProjects first and see if someone can help you there. There's no rush :) I'd agree that it looks more like an autophagical process but it's hard to tell, as you mentioned, if it's being performed under the 'supervision' of a larger process. Regards, --—Cyclonenim | Chat 22:20, 11 August 2010 (UTC)[reply]
The best way to be sure would be to fix and immunostain the cells to look for specific markers for autophagosomes; microtubule-associated light chain 3 (LC3) associated with vesicle membranes is one of the popular markers in mammalian cells ([22]). Meanwhile, you can look for the activation of apoptosis machinery in the cells by staining for cleavedcaspase-3. It is apparent that there are some sort of perinuclear vesicles in those cells, but I would be hesitant to jump to conclusions about their identity. TenOfAllTrades(talk) 22:36, 11 August 2010 (UTC)[reply]
Burping in zero gravity
A while ago I needed to burp while lying down. I could not do it, I imagine because the bubble of burp-gas must be in contact with the upper sphincter of the stomach. In gravity this is no problem. But what do astronauts do in space? Google searching has not come up with any serious answer. Thanks. 92.15.14.45 (talk) 21:36, 11 August 2010 (UTC)[reply]
This article (towards the bottom) suggests that astronauts can burp in space, but since the gas isn't necessarily at the top of the stomach, it comes out as an unpleasant wet burp. anonymous6494 02:45, 13 August 2010 (UTC)[reply]
In other words it would be like a mini-vomit. No wonder NASA have kept quiet about it. 92.29.127.240 (talk) 15:11, 13 August 2010 (UTC)[reply]
Impact of piping on water quality
I asked a similar question here, but I figure this is more of a science question. The question is - if the water is pure when it is pumped into water supply system, can it get contaminated while it travels through piping (i.e. by something in the pipes, not foul play) ? ~~Xil (talk) 22:15, 11 August 2010 (UTC)[reply]
City water supplies are continually scoured by the flow of water so there is no opportunity for bacteria to establish a stationary colony in the pipe and contaminate the water flowing through. Where water lies stagnant in a pipe for a long period of time, such as in unoccupied houses, there is a risk of colonies of bacteria becoming established and contaminating the initial throughput of water when flow resumes.
The major risk of contamination of a city's water supply is contamination at the point of collection (such as a dam) or prior to collection if there are contaminants in the catchment area (such as a dead animal.) Dolphin(t) 22:40, 11 August 2010 (UTC)[reply]
Older homes and some older municipal water systems may use lead solder and even segments of lead pipe. Water that is left standing for an extended period (several hours or overnight) may pick up a toxic level of lead.
Biological contamination is rare unless the pipes are damaged close to the end user and external organisms are able to contaminated the drinking water. (This is rare and rather difficult to do, as the water in the pipe is generally being forced out under pressure.) As well, in many municipal water systems water is treated with chlorine or chloramine; the latter compound in particular tends to persist for several days in the water, providing a residual disinfectant activity all the way out to the consumer's tap. TenOfAllTrades(talk) 22:56, 11 August 2010 (UTC)[reply]
Your note about lead reminded me - I read somewhere that piping for drinking water used to be made from copper to improve its quality, is any particular metal used or other material used for same purpose today ? Also asumtion here is that piping is old (not leaking old, but I figure pipes could be rusty, there could be some sediments or stuff growing on wals of pipes or something). Aside from being curious about water supply systems in general I am also concerned about water I am drinking, I found out that my city has two water sources. One is river water which is treated with aluminium sulphate, ozone and light dose of chlorine before it is pumped to consumers. However I live in another part of city which uses ground water taken from soils rich with iron and manganese. My issue here is that despite very good taste, I feel a light, but foul smell when drinking ~~Xil (talk) 08:37, 12 August 2010 (UTC)[reply]
Most of the piping in my own house (UK, about a century old, but repiped some time since the initial build) is copper, which was the default material in the UK at least until quite recently and is certainly still used for repairs. Plastics of some sort might be used in new buildings now, but primarily for cost rather than health reasons, copper being increasingly in demand for other purposes, and therefore increasingly expensive.
In the UK and, I think, most First-World countries, water supply companies are legally obliged to deliver drinkable water to customers, and are responsible for the pipework right up to the latter's property line - they would be heavily penalised if they failed to do so whether due to pipework contamination or for any other reason. Certainly water from different sources can differ in its trace elements as well as the treatments it has undergone to ensure it is potable, and this will be detectable in the taste and smell, which is partly why, for example, many breweries in the UK "Burtonise" their brewing water (or "liquor"), adding trace elements to make it more like the natural supply in Burton-on-Trent*. Different people find these different tastes and smells variably noticeable, innocuous or sometimes unpleasant, but unless something has gone wrong, they do not usually signify any health hazard. However, such factors are so variable from country to country that it is impossible to safely generalise for an unspecified locality.
(*As well as effecting the immediate taste to humans of the water component of the beer, the trace elements also influence the metabolism of the fermenting yeasts - but I digress.) 87.81.230.195 (talk) 12:14, 12 August 2010 (UTC)[reply]
In terms of sediment and stuff settling in the pipes, I don't think this is likely to be a significant problem due to the constant water flow. In Malaysia, when you get a water cut, you will find the water is dirty when it first starts flowing again. I'm not sure if this is from the pipes or the supply but I think it is the former as the water flowing again dislodges stuff that has settled and/or any oxides or whatever from the pipes Nil Einne (talk) 14:18, 12 August 2010 (UTC)[reply]
Antibiotic-resistant "super bug"
I just saw a story on the news about a "super bug" that's resistant to all known antibiotics and can spread this immunity to other bacteria. What research has been started to combat this before it causes the extinction of humanity? --70.134.48.188 (talk) 22:17, 11 August 2010 (UTC)[reply]
Firstly, don't listen to everything the news tells you. Yes, it's a fairly big blow for antibiotics but not absolutely condemning for all of humanity. Not just yet. What happens is that it prevents any antibiotic with β-lactam rings from working, but this protein that's causing all the havoc is only present in certain, limited Gram-negative bacteria (such as E. coli and others) so far. It could spread and become more common, but it hasn't yet. Other Gram-positive bacteria can still be treated, so contrary to popular opinion, it's not the end of antibiotics completely. There are currently no drugs in the pipeline (or at least pre-clinical stage pipelines) that are able to combat this obstacle, but that doesn't mean we're completely hopeless at finding another. One option, as I posted a question about above, could be to develop phages that actively hunt and kill off bacteria, but they are currently not approved for human, medicinal use. It is not the end of the world... yet. Regards, --—Cyclonenim | Chat 22:24, 11 August 2010 (UTC)[reply]
What about it? It's a B-lactam antibiotic, so it wouldn't work on any bacteria with this new gene. Regards, --—Cyclonenim | Chat 18:35, 13 August 2010 (UTC)[reply]
What "super bug" in particular ? In any case the bacteria evolve so they eventualy are resistant to older drugs, therefore new drugs need to be invented. This happens all the time, "super bug" is just media hype. One such "super bug" case was the recent swine flu pandemic. ~~Xil (talk) 22:34, 11 August 2010 (UTC)[reply]
They said it's a bacterium that's completely immune to all known antibiotics. --70.134.48.188 (talk) 22:36, 11 August 2010 (UTC)[reply]
What I meant was it does it have a name other than "super bug" ? If not it may very well have been a speculation that such "super bug" may emerge, not that it is currently infecting people (if it was and it wasn't contained we would see broader media coverage) ~~Xil (talk) 22:52, 11 August 2010 (UTC)[reply]
Let me clarify: it is not a super bug. It's a super plasmid. It accounts for resistance to any antibiotic that replies on beta-lactam rings (which is a lot of them) and is currently spreading around through various mechanisms I won't bother to go into. However, it's only relevant to specific bacteria called Gram-negative bacteria. Antibiotics that currently work on Gram-positive bacteria will still work (for now). We may even develop new ones for Gram-negative bacteria. The media is lying when it says it's the end of all known antibiotics. Regards, --—Cyclonenim | Chat 23:38, 11 August 2010 (UTC)[reply]
Another thing to bear in mind before writing off the human race is that the vast majority of bacteria (including those bearing exotic plasmids) are completely harmless to us. Bacteria that are either fatal or seriously harmful tend to evolve to be less nasty because if the host dies or becomes so sick that they go to bed and stay there, the bacteria have a much harder time spreading. From an evolutionary perspective, the optimum thing for the bacteria to do is to be massively infectious - yet produce as few symptoms as possible. Sure, when a new disease pops up, a good percentage of the population might die before that happens - but it's hard to imagine a scenario where that would take out more than a few percent of the worlds population. When you look at some of the worst pandemics in history - the 1918 flu pandemic, for example. Over the course of two years, one third of all people in the world were infected and 3% of the world's population died. There were absolutely no drugs that could to a thing to prevent it. The disease never was 'cured'. The pathogen simply evolved to be less obnoxious all by itself. Certainly a 3% death rate would be a monumental disaster - but (as you can tell from the 1918 event) the long term effects on humanity are minimal and the worst disease epidemic in history is barely even talked about, 90 years later. SteveBaker (talk) 03:34, 12 August 2010 (UTC)[reply]
Is that true? I'm unsure. I know it definitely applies to viruses, because they are, in a literal sense, parasites which invade our cells. If the cell dies (without it bursting), then they can't replicate and spread. Bacteria, however, aren't parasites. They invade our blood and tissues but they don't strictly interact with the cells, do they? Might be wrong. Regards, --—Cyclonenim | Chat 07:52, 12 August 2010 (UTC)[reply]
I don't think notion that disease cannot have long term effect on civilization is entirely true - the plague apparently did, though the death toll was higher than 3% ofcourse (still if people survived plague pandemic in age when health care was less developed, why wouldn't people survive now ?) ~~Xil (talk) 08:49, 12 August 2010 (UTC)[reply]
We do have examples, though, of basically entire civilizations being killed off by pandemics, e.g. the Native Americans, who under some estimates had 95% of their population killed by Old World viruses to which they lacked immunity. That's a pretty extreme scenario, but it's pretty hard to contemplate. Even 33% is a ridiculously high number, and would have massive effects on human civilization and society (as did the Black Plague on Europe). If you're willing to say that's OK because life will be different/better/go on, you might as well say that nuclear war is fine too, because those are the kinds of numbers we are talking about. --Mr.98 (talk) 12:51, 12 August 2010 (UTC)[reply]
Well, it's obviously not "fine" - but the point is that it's also not "the extinction of humanity" - which is what our OP is asking about. SteveBaker (talk) 14:10, 12 August 2010 (UTC)[reply]
Keep in mind, the bacteria still needs to be able to gain entry into the body to be harmful. We have many layers of innate resistance to microbes (see innate immune system), none of which are affected by bacterial acquisition of antibiotic resistance. According to BenRG's helpful reference above, many of the people who have been infected by these super-organisms were "infected by NDM-1 carrying bacteria while undergoing surgery under non fully-aseptic conditions." This means that the "super-bug" is largely responsible for nosocomial infections, certainly nothing like a "pandemic" that can somehow spread from person to person. It is another in a long example of antibiotic resistances that bacteria have evolved over the millenia. Where did we first get antibiotics from? mold. How long have bacteria and molds been fighting with each other? This is evolution in action and we are only recent players.
I'm not trying to downplay the devastating effect of antibiotic resistance on the way that medicine is practiced today, but you have to realize that the media is going to hype up this kind of thing to sell their product. This latest version of the "super-bug" is not going to cause the end of our species. --- Medical geneticist (talk) 12:40, 12 August 2010 (UTC)[reply]
An antibiotic-resistant "superbacteria" can cause a major pandemic with many casualties, but it will not drive humanity to extinction. Remember that we only have antibiotics since not much more than a hundred years ago: so people before it had to deal with illnesses having no antibiotics at all. A lot of people might die, but it's very far from extinction. --131.188.3.21 (talk) 23:49, 12 August 2010 (UTC)[reply]
NDM-1 isn't really "super", nor is it a "bug". It's an enzyme that gets into different types of bacteria and makes them immune to antibiotics, similarly to how disinfectants that kill 99.99% of bacteria and viruses leave the remaining 0.01% mutating into superbugs that over several cycles become completely resistant to antibiotics and disinfectants. It's not that the bacteria infected by this "superbug" become extra deadly, they just become much harder to kill. So if it found itself preferring a bacterium that has a high mortality rate in humans and quickly spreads in those bacteria, then we might have a problem. The real pandemics like the Black Death and the more recent 1918 flu pandemic were devastating, but the recent pandemics have been not that severe, although the melting of glaciers and permafrost in Arctic regions could release ancient viruses in the future. ~AH1(TCU) 00:21, 13 August 2010 (UTC)[reply]
Bacteria have been living on Earth for about 4 billion years in all sorts of environments. Complex life forms have been around for a much shorter time and the environments they can live in is far more limited. Surely, then the massive use of anti-biotics is a stupid, self-defeating strategy as eventually you'll end up with superbugs that are only sensitive to drugs that are lethal to humans? Count Iblis (talk) 15:14, 13 August 2010 (UTC)[reply]
Probably, but it's good for saving lives in the meantime. There's no guarantee that bacteria will develop resistance because, like natural selection, you have to have the mutation occur first. If it doesn't happen, obviously you'll get no resistance. The reason resistance is currently so common is because a lot of our antibiotics only vary slightly. There are different classes, but within those classes the variation is limited, so there isn't much work needed to accidentally develop a resistance to a new antibiotic. Regards, --—Cyclonenim | Chat 21:15, 13 August 2010 (UTC)[reply]
August 12
Famous scientific hypothesis
I need to prepare for my science test a description of two famous hypothesis. Thus, I need your help to give me two science hypothesis (from any field), that is easy to understand and explain. Thanks! --Tyw7 (☎ Contact me! • Contributions) Changing the world one edit at a time! 02:43, 12 August 2010 (UTC)[reply]
It would help if you'd explain what grade level you're dealing with. The theory of evolution can be made pretty simple or pretty complex depending on how deep you want to go with your explanation. Dismas|(talk) 03:00, 12 August 2010 (UTC)[reply]
Grade 11. Easy means easy to remember and type in a closed exam. IE can be explained in a few simple words. --Tyw7 (☎ Contact me! • Contributions) Changing the world one edit at a time! 03:02, 12 August 2010 (UTC)[reply]
DO they need to be correlated (i.e., one versus the other, opposing theories)? If not, I suggest the quantum field theory and effective field theory (disclaimer: I'm an engineering graduate student ;). If so, how about the accepted Darwinian model of evolution versus the Lamarck model? You'll have to come up with the descriptions yourself ofcourse; if we did that it would be equivalent to doing your homework for you. 76.228.193.68 (talk) 03:04, 12 August 2010 (UTC)[reply]
I'd go with Darwinian evolution and Lamarckian evolution, myself. Both famous, both related, both easy to summarize in a couple of sentences, and taken together, a good example of how hypothesizes can be tested, with ones that don't match reality being discarded. -- 174.24.200.206 (talk) 03:09, 12 August 2010 (UTC)[reply]
But I think it's fairly well established that Mendel forged a significant amount of his data to fit with his hypothesis. It might have been true in the end, but that's not real research. DRosenbach(Talk | Contribs) 15:02, 13 August 2010 (UTC)[reply]
The phlogiston hypothesis would be another good one that also proved to be wrong. --Anonymous, 03:20 UTC, August 12, 2010.
How about one that was proven right? --Tyw7 (☎ Contact me! • Contributions) Changing the world one edit at a time! 03:23, 12 August 2010 (UTC)[reply]
One rarely proves a hypothesis right. One only looks for disproof. The theory of natural selection, as noted above, is accepted as scientific fact, due to its lack of falsification and explanatory power. The Rhymesmith (talk) 03:27, 12 August 2010 (UTC)[reply]
Well, one very famous hypothesis which was tested and shown to be accurate was the experiment which proved the Gravitational lens prediction proposed by Einsteins' General Relativity. Arthur Stanley Eddington famously showed that the mass of the sun bent light so that objects behind the sun could be viewed during the Solar eclipse of May 29, 1919. It was a simple observation which confirmed an unusual hypothesis, that large objects could bend space-time, and thus cause light to appear to bend around them. --Jayron32 05:44, 12 August 2010 (UTC)[reply]
Prout's hypothesis is a nice example, easy to explain, easy to show how it was proved wrong (the atomic weight of chlorine), and nice because it's almost correct in modern terms. Physchim62(talk) 11:59, 12 August 2010 (UTC)[reply]
Quark
Does the atomic theory deals with quarks? Is atoms made of quarks? What is the smallest unit of matter as of today? --Tyw7 (☎ Contact me! • Contributions) Changing the world one edit at a time! 03:25, 12 August 2010 (UTC)[reply]
Reading... The article does not mention quarks, so I presume its covered by another theory (not atomic theory)? --Tyw7 (☎ Contact me! • Contributions) Changing the world one edit at a time! 03:27, 12 August 2010 (UTC)[reply]
In case the previous sentence was ambiguous, protons and neutrons are made of quarks, while electrons are not. The phrase "Atomic Theory" generally only refers to looking down to the level of atoms, and sometimes of the particles that make up atoms (protons, neutrons, and electrons). The "Standard Model" would be the "theory" that includes quarks. "Particle physics" would be a general term used to describe the physics of Elementary particles, including quarks. Obviously, these fields are not strictly defined, and there is a considerable amount of overlap. Buddy431 (talk) 03:58, 12 August 2010 (UTC)[reply]
Our articles don't seem to mention size. I assume that this is because the effective diameter depends on where the particles are, and what they are doing, and how we try to measure size. For most practical purposes, quarks and all of the particles mentioned by Astro above have zero size (i.e. they are all singularities in a general sense), so the comparison cannot be made. One could claim that they all have zero size. Perhaps, sometime in the future, when we find a way to measure distances less than a tenth of a millionth of a millionth of a millimetre, we might compare their effective sizes in some way, but, at present, we regard them all as point masses, charges, colours etc.
How about the core of a neutron star ? Probably not what you meant... Sean.hoyland - talk 06:01, 12 August 2010 (UTC)[reply]
No. It's speculated that hydrogen might do that at extremely high pressures and extremely low temperatures, but it has never been observed. I believe all known superconductors are solids. Dragons flight (talk) 07:01, 12 August 2010 (UTC)[reply]
Is it possible to build a gun like this ? The drop is tightly fit in the breech. When the firing pin hits and drop is exploded the ball rushes out and do the usual gun thing ? Jon Ascton (talk) 05:07, 12 August 2010 (UTC)[reply]
I'm not sure that Prince Ruperts Drops explode with all that much force. Its a rather spectacular splash of glass, but the "explosion" is many orders of magnitude smaller than any combustable material or high explosive. It doesn't really explode as much as crack very fast. It may generate enough force to make the ball dribble out of the barrel of your gun, but little more. --Jayron32 05:35, 12 August 2010 (UTC)[reply]
Build - yes. Use - no. These things, by definition, cannot be stabilized for safe handling in the field. East of Borschov 05:47, 12 August 2010 (UTC)[reply]
Glass contracts as it solidifies so the inside of the Prince Rupert's Drop is under tensile stress. I conclude that the drop implodes rather than explodes, and would not expel the ball. Cuddlyable3 (talk) 14:56, 12 August 2010 (UTC)[reply]
When something implodes, fragments can still fly outwards -- the ones that happen to pass through the center without hitting other fragments, or as a result of fragments colliding elastically. But it is true that they'll tend to lose kinetic energy as they come together, of course. --Anonymous, 17:52 UTC, August 12, 2010.
Gunpowder would be a better option! Alansplodge (talk) 23:13, 12 August 2010 (UTC)[reply]
Colloids
Do viscous substances have more Surface tension than non viscous substances?? How does Lyophilic colloids have less surface tension than the solvent??Rohitbastian (talk) 06:03, 12 August 2010 (UTC)[reply]
Viscosity and surface tension are unrelated to each other. Water has a relatively high surface tension, and a relatively low viscosity, for example. And lots of mixtures have lower surface tension than the pure solvents they are based on. See Surfactant for more. --Jayron32 06:33, 12 August 2010 (UTC)[reply]
Erectile dysfunction drugs
Did the makers of Cialis and Levitra copy and modify the chemical structure of Viagra or did espionage occur? It seems like they came out right after Viagra did. It would be understandable if they came out years later, but I believe they came out within a short period of time after Viagra (but I may be wrong). Would it be really possible to find or make a similar medication within such a period of time if they didn't copy it? —Preceding unsigned comment added by 76.169.33.234 (talk) 06:09, 12 August 2010 (UTC)[reply]
While Sildenafil (Viagra) and Vardenafil (Levitra) share some similar chemical structure, Tadalafil (Cialis) appears to be quite different. The first of these, Viagra, was not originally marketed for use in fixing erectile dysfunction, rather as a hypertension medication. The erection was basically a side effect which ended up becoming the actual intended use. Both Cialis and Levitra were developed, at least in part, by GSK, so that explains some of their connection. The general class of drugs is discussed at PDE5 inhibitor. --Jayron32 06:30, 12 August 2010 (UTC)[reply]
I actually worked at an Eli Lilly site when Cialis appeared, and hadn't known the GSK connection until now. (Checking Jayron32's answer, I found that it was discovered by an SK/ICOS joint venture, but developed & marketed by an ICOS/Lilly one.) Apparent coincidences like this are partly explained by the very long times it takes to develop newly discovered "candidate molecules" all the way to market (assuming they make it - only around 1 in 10 do): up to 10 years (and a cost of around half a billion US$) is typical. A Company might be able to speed up the process a little by devoting more resources to a given candidate, and might be inclined to do that if a competitor is known to be in the works, so as not to concede more market advantage that they have to by allowing more of a head start: thus the release dates can converge. 87.81.230.195 (talk) 11:46, 12 August 2010 (UTC)[reply]
BTW if you read the obvious articles, which Jayron32 has helpfully linked above, you'll find Sildenafil i.e. Viagra received FDA approval in March 1998 and the other two in August and November 2003 or over 5 years later. I'm not sure whether you consider that 'short period of time' or 'years later' but I would say it isn't an unresonable length of time just for fairly normal development, particularly since the drugs were already in development even if not for the specific purpose and as 87 has mentioned a company may devote more resources if they see it as important or likely to be a success. Nil Einne (talk)
PROGESTERONE
Progesterone:-
would the use of progestrone, used in the form of an transdermal cream, have an effect on a person who has high colesterole? —Preceding unsigned comment added by Gilpill (talk • contribs) 08:56, 12 August 2010 (UTC)[reply]
Could you clarify the question? Are you asking whether progesterone has its normal effects even if the person has high cholesterol? Or if progesterone affects cholesterol levels? Or if the specific transdermal application has specifically different effects related to cholesterol? As a starting point, Bioidentical hormone replacement therapy#Lack of evidence for claims suggests that--at least in the cases considered there--route/form of administration of progesterone does not have an effect consistent with altered cholesterol levels. DMacks (talk) 13:12, 12 August 2010 (UTC)[reply]
"Smotl."
Hi all,
One of my pet peeves is binomial authorities without articles or at the very least a full name. So far only Boletus rhodopurpureus cites one "Smotl." as binomial authority. Google results would suggest that he or she is apparently eminent in Mycology... but not even a trace of ""Smotl."'s family name, let alone his or her full name. So, who was that masked mycologist? --Shirt58 (talk) 11:22, 12 August 2010 (UTC)[reply]
And why did s/he leave name this silver fir-associated boletus? 87.81.230.195 (talk) 11:25, 12 August 2010 (UTC)[reply]
Or was it Miroslav Smotlacha who is a famed Czech mycologist who died at age 86 back in 2007? According to his obituary, his entire family are mushroom experts - so it could have been any of half a dozen people with the same surname. SteveBaker (talk) 14:05, 12 August 2010 (UTC)[reply]
Ummm... it appears I might have made an oopsy here --Shirt58 (talk) 12:56, 13 August 2010 (UTC)[reply]
Or not, it's hard to tell. :) Maybe you could expand it to cover the family ? Sean.hoyland - talk 13:02, 13 August 2010 (UTC)[reply]
It would appear that Miroslav Smotlacha is František Smotlacha's son.[1]
how can that possibly be true???
It says 1.5 million facebook users die every year!! How can that possibly be true??? That can't be just a coincidence, but what could possibly explain this, it just doesn't make sense! Is it just a lie?! Or how is it true!!! 84.153.200.162 (talk) 14:54, 12 August 2010 (UTC)[reply]
The world death rate is something like 8 deaths per thousand people per year. Facebook has something like half a billion active users. Thus if Facebook users are as likely to die as anyone else, we would expect about four million to die every year. So if your figure is accurate, then Facebook users are in fact much less likely to die than people on average – as we would expect, given its target demographic. Algebraist 15:01, 12 August 2010 (UTC)[reply]
Cool! Use facebook - live 2.7 times longer! SteveBaker (talk) 15:36, 12 August 2010 (UTC)[reply]
This discussion reminds me of how some people were surprised ~350 people die in Moscow every day Nil Einne (talk) 15:54, 12 August 2010 (UTC)[reply]
Given that average life-expectancy is around 70 years, then 500million / 70 year = 7 million/year. This of course assumes that facebook's user demographics is about the same as the average person, which probably is not accurate. CS Miller (talk) 16:48, 12 August 2010 (UTC)[reply]
Except, as I'm sure we're all aware, it's not that simple. I'd suggest that Facebook has a lot more users in the 16-40 years old range than elderly 70 year olds. If 1.5 million Facebook users die every year, I'm sure a lot of those will be unfortunate accidents. Regards, --—Cyclonenim | Chat 21:05, 12 August 2010 (UTC)[reply]
Oops, just noticed I basically reiterated CS Miller above. My bad :) Regards, --—Cyclonenim | Chat 21:32, 12 August 2010 (UTC)[reply]
When Facebook first started, the largest group of users was likely young adults in post-secondary education such as college or university. Currently the fastest-growing demographic group on Facebook is women over 55. ~AH1(TCU) 00:09, 13 August 2010 (UTC)[reply]
How much does an aluminium soda can tab weigh?
(This is an offshoot of a question on the misc ref desk - but I'm hoping someone with an accurate laboratory scale can get me a better answer).
How much does the ring-pull 'tab' on a typical soda can weigh?
Just so we know, what degree of accuracy are you expecting? Vimescarrot (talk) 15:19, 12 August 2010 (UTC)[reply]
For clarification... are you referring to the old style that completely comes off the can or the new style that stays on the can, but you can remove if you bend it back and forth a lot? If it is the old style, that will be hard to answer. If I can locate a can, I can do the new type. Everyone around here appears to use bottles now. -- kainaw™ 15:20, 12 August 2010 (UTC)[reply]
The newer kind that you have to bend back and forth to remove...to a very rough precision (I guess tabs from different manufacturers are a bit different)...+/-20% should be fine. Thanks! SteveBaker (talk) 15:29, 12 August 2010 (UTC)[reply]
I thought this would be trivial to do, but there are no cans here. Our vending machines only have bottles and the convenience store across the street only has bottles. If nobody answers, I will do my best to remember to bring in a few tabs tomorrow and weigh them on one of the drug scales which go to 1/1000th gram. -- kainaw™ 16:49, 12 August 2010 (UTC)[reply]
As a completely random aside primarily arising because it's something I've been looking at recently. You can get cheap high precision scales from China/HK eBay sellers, something like US$6.00 shipped for a 100g/0.01g or US$8.50 shipped for a 300g/0.01g scale isn't uncommon. I wouldn't use these for serious work but from what I've read the precision is usually fairly good, i.e. they will give about the same value for the same weight and neither where you put the mass nor the temperature (within reason) have a significant effect. However the accuracy on these scales is likely to be far more questionable and there is a possibility they may drift over time (I read one person saying their one did). They can usually be calibrated and you can buy cheap calibration weights but of course the accuracy of cheap calibration weights is also questionable. However if you do have access to a accurate high precision scale, you could test them or for that matter make your own calibration weight to hopefully give you a resonably accurate high precision scale (you can also test it with various masses after calibration). I've seen some people use coins but I'm dubious that will give you an accurate enough calibration or test weight. Of course the precision is useful if that's all you need, I think some people use them for balancing RC helicopter rotors blades. There are also 0.001g ones but they're a fair bit more, like US$15.00, and while I haven't looked in to them much, I do wonder whether that precision is worthwhile on something so cheap. Nil Einne (talk) 18:34, 12 August 2010 (UTC)[reply]
I get 0.300 grams. I wouldn't be surprised if that can swing at least a few milligrams up or down depending on precisely where the tab tears when it is removed from the can. (I don't know what the distribution is; I only conducted one measurement.) TenOfAllTrades(talk) 18:22, 12 August 2010 (UTC)[reply]
That's plenty good enough! Many thanks. SteveBaker (talk) 19:17, 12 August 2010 (UTC)[reply]
It is usually stated in his biographies and obitiaries as "unspecified". When someone dies peacefully in their bed at age 95, there isn't generally any cause of death listed. "Natural causes" or "Old age" is the best you're going to get. Of course, something very specific did kill him - heart failure or something - but nobody is gonna being doing an autopsy to find out. SteveBaker (talk) 19:21, 12 August 2010 (UTC)[reply]
If you really want to know, it looks like you can go here and get his death certificate. --Sean 21:29, 12 August 2010 (UTC)[reply]
He had suffered a stroke on September 7, 2003, and died two days later. (Goodchild, Edward Teller, The Real Dr. Stranglove, 394.) At age 95 he suffered from a whole host of old-age related maladies. I think "old age" or "natural causes" is probably whatever his certificate said; they probably did not bother doing an autopsy. I've added the basic info to the article.--Mr.98 (talk) 00:00, 13 August 2010 (UTC)[reply]
Magic
Does magic really exist? I heard that in about 16th century in Europe, there are many witches got burned to dead.75.73.152.238 (talk) 19:30, 12 August 2010 (UTC)[reply]
What caused the witch-hunt. Are they really witch? If not, why did we kill them?75.73.152.238 (talk) 19:52, 12 August 2010 (UTC)[reply]
Panic, mass hysteria, paranoia. Plus the ordinary run of the mill mistakes in the justice system that allows innocent people to be executed to this very day.
This is all explained pretty well in the Witch hunt article. APL (talk) 19:57, 12 August 2010 (UTC)[reply]
It seems likely to me that there were at least a few people around who thought they were witches and could cast spells. After all, there are people today who think that, in this far more rational age. But of course the great majority who were burnt were completely innocent. Looie496 (talk) 21:25, 12 August 2010 (UTC)[reply]
And, let's be clear, unless those people who thought they were witches were actually poisoning people or animals, they were also completely innocent. You can't be guilty of actually casting evil magic spells that cause your neighbour's cows to dry up. 82.24.248.137 (talk) 00:09, 13 August 2010 (UTC)[reply]
Magic is usually defined as "Powers outside of nature", but as soon as someone discovers how to do something, it's automatically part of nature. So by that definition magic can never exist - because as soon as it's discovered, it's no longer magic. But, if we change the definition to "Unexplained phenomena" then magic did (and does) exist, because there were (and are) lots of unexplained things. In the search for explanations for the unexplained (especially the tragically unexplained) people accused those that were different. Ariel. (talk) 21:24, 12 August 2010 (UTC)[reply]
I take issue with your comparisons, Dr Dima. From a Jewish perspective, while technology is reproducible and morally neutral, magic is not. You mustn't pray, "Oh Awesome Computer, please send my email!!" Rather, you click on the button, and whether you're an old lady who executes cats in her basement after torturing them or an upstanding member of the community, the computer will send your email. But cauldrons of potion require incantations and the like, beseeching the (non-existent) power of magic. If one is worthy, one's virgin in the volcano is accepted and the magical request may be granted. Thus, magic and technology are examples of two distinct and non-overlapping magisteria. DRosenbach(Talk | Contribs) 15:14, 13 August 2010 (UTC)[reply]
That's just a fancy term for the god of the gaps. 67.243.7.245 (talk) 03:52, 14 August 2010 (UTC)[reply]
Speaking of witches, wicca may be relavent. ~AH1(TCU) 00:06, 13 August 2010 (UTC)[reply]
In the Old Testament there is an explicit instruction that women who are witches or sorceresses are to be put to death. It is found in Exodus 22:18. Different versions of the Bible translate this instruction in different ways, but the central message is the same – a woman is to be put to death if she might be a person who practices magic.
Thou shalt not suffer a witch to live (King James Version)
Put to death any woman who practices magic (Good News Version – makes one wonder what the Bad News Version would say!)
You shall not permit a sorceress to live (Revised Standard Version)
There is no similar instruction regarding the execution of men - only women! And there is no opportunity for tolerance or a lesser punishment such as counselling or even a curfew – death is the only acceptable outcome!
In past centuries, prior to the broadcast of science and education, people relied heavily on ancient scriptures to guide them in their daily lives. As a result, all manner of injustice and foolishness pervaded human communities that practised loyalty to these ancient scriptures. The murder of women, and particularly old women, out of fear of witchcraft and sorcery is merely one of the injustices that persisted for thousands of years as a result of the unquestioning loyalty to ancient scriptures. Dolphin(t) 03:46, 13 August 2010 (UTC)[reply]
It's 22:17 not 18. And your rant about women is wrong because you forgot about Deuteronomy 18:10 which uses the male version of the female word used in Exodus. The rest of your rant has nothing to do with scriptures and everything to do with people who simply wanted to, due to fear of "other", or "strange", scriptures were just an excuse. Just look at Africa today where such executions are still carried out and have nothing to do with scripture. Ariel. (talk) 06:09, 13 August 2010 (UTC)[reply]
I did not forget about Deuteronomy 18:10 because I know nothing about it. However, the nineteen persons (or groups of persons) responsible for the nineteen translations listed at Ex 22:18 might have forgotten about it, but I doubt it because to translate the Bible, and have it published, one must be an expert. In those nineteen translations no masculine word, or male version of a female word is used. The female word sorceress is used many times, but the male equivalent sorcerer is not used in any of the nineteen translations (except in the expression female sorcerer.) I concede that the gender-neutral word witch is used in two of the translations, and the word witchcraft once, but no unambiguously male word appears. I agree that many executions of alleged-witches would have been because people just didn't like the person and were motivated to murder that person, but the existence of Exodus 22:18 provided many of the murderers with re-assurance and justification that what they were doing was not only legitimate but an explicit commandment from holy scripture. Dolphin(t) 07:39, 13 August 2010 (UTC)[reply]
Considering they got the verse number wrong I don't think they are a reliable source. Ariel. (talk) 19:55, 13 August 2010 (UTC)[reply]
where do i get pizza condiments like they have in pizza hut in the glass shakers —Preceding unsigned comment added by Tomjohnson357 (talk • contribs) 20:28, 12 August 2010 (UTC)[reply]
You mean parmesean cheese and crushed red pepper? Most grocery stores carry those. Googlemeister (talk) 20:35, 12 August 2010 (UTC)[reply]
You might have to buy the glass shakers separately (supermarkets usually sell in plastic, but I've seen pretty good ones at a 'restaurant supply store' that is open to the public.) RJFJR (talk) 21:12, 12 August 2010 (UTC)[reply]
Here you can get the shakers for about a buck. The green stuff is usually stale oregano, and there's parmesan and red pepper flakes, as mentioned. --Sean 21:31, 12 August 2010 (UTC)[reply]
I was watching this episode of House, and they did an experiment where they where able to see what a person was thinking by reading brain waves while look at pictures so the computer knows what triggers what in the brain. Is this actually possible? 99.114.94.169 (talk) 20:31, 12 August 2010 (UTC)[reply]
To a very limited extent, yes. You can see what areas of the brain are being used at any given time with various forms of functional neuroimaging (read that article and the articles it links to for details). While that isn't enough to work out what someone is thinking from scratch, you can compare it to previous scans of the same person and find a match and know that they are probably having the same kind of thoughts (eg. you show them a bunch of pictures and see what parts of their brain are active when they consider the picture and then show them one of the pictures again at random and you can work out which one it is by comparing the brain scans). While there are general areas of the brain that do the same thing is everyone, there is enough variation that you do generally need to establish a "baseline" using scans of that particular person's brain before you can use new scans to determine anything substantial about their thoughts. Also, the best you can do is work out what kind of thinking they are doing (for example, thinking about something they enjoy, thinking about moving their body, thinking about hearing something, etc.). You can't work out specific thoughts. --Tango (talk) 21:07, 12 August 2010 (UTC)[reply]
If our article's description of the episode is correct, the things they do (mapping the thoughts of an unconscious person) go vastly beyond anything that is currently possible. Current technology is at the level of things like trying to read brain waves well enough to let a person to use them to move a lever back and forth. Looie496 (talk) 22:35, 12 August 2010 (UTC)[reply]
If I recall the episode correctly, they show the patient a huge number of reference images, and have the computer create a sort of database of what this patient's brain looked like when they were looking at each of the images. Only after hours of that did they start trying to reverse the process. They don't dwell on it, but I got the impression they were relying on the computer running some sort of algorithm, possibly like facial recognition software, making up the new image out of combinations of basic features from the huge database of images. Do I mean eigenfaces? It was the sort of thing that seemed probably not possible with current technology, but plausible in the not-distant future. (In fact, the characters in the episode are all a bit surprised it works) But I'm no expert. 82.24.248.137 (talk) 00:04, 13 August 2010 (UTC)[reply]
I'm going to call [citation needed] on your claim it's plausible at all. The episode was the worst House episode in memory when it comes to plausibility. Comet Tuttle (talk) 15:12, 13 August 2010 (UTC)[reply]
Worst. Episode. Ever. I'm afraid my criteria for 'seems plausible in the not-distant future' is that I can imagine the mechanism by which it would work, using merely more-advanced versions of technology we currently possess. It seems probably not possible with current imaging, although with enough care and a large enough database of examples for that individual, I wouldn't be wildly surprised by a much vaguer result being achievable. The sort of result that might let you tell whether they were thinking of a round thing or a tall thing, a dark thing or a light thing, a single shape or many shapes. 86.164.66.83 (talk) 22:23, 13 August 2010 (UTC)[reply]
It's definitely quite impossible right now. I'm skeptical that the approach suggested in House would actually work - it presumes a lot of things about the brain that we simply do not know to be true. SteveBaker (talk) 02:23, 13 August 2010 (UTC)[reply]
I think it might work in principle, but current functional imaging techniques don't come close to the spatial resolution or signal-to-noise ratio that would be needed. Correlation-based reconstruction is pretty robust -- it can work well even if you don't have any idea what the activity patterns actually mean. Looie496 (talk) 03:07, 13 August 2010 (UTC)[reply]
Thanks for the responses, it seems it would make an interesting field of science. 99.114.94.169 (talk) 04:33, 13 August 2010 (UTC)[reply]
I don't know the episode of House in particular (don't watch it) but from what's been discussed so far some may be interested to know various companies are developing fMRI lie detector tests. These have even been (controversially) used in Indian court cases www.policyinnovations .org/ideas/briefings/data/000172 (black listed site) Nil Einne (talk) 17:35, 13 August 2010 (UTC)[reply]
Ca2+ It coordinates well with lewis bases such as crown ethers. In a similar way, it can bind to various sorts of structures during a reaction to allow one part of a molecule to serve as a template for another. For example, residual calcium ions from one step were critical in stabilizing a structure by two hydroxyls and an ether cause a subsequent reaction to proceed a certain way. (doi:10.1002/1521-3773(20010105)40:1<191::AID-ANIE191>3.0.CO;2-C) DMacks (talk) 23:41, 12 August 2010 (UTC)[reply]
Pulse deficit
Why in atrial fibrilation there is pulse deficit while in very rapid supraventricular tachycardia there is not? Moh1988has (talk) 22:33, 12 August 2010 (UTC)[reply]
Where did you get that information, please? Looie496 (talk) 01:01, 13 August 2010 (UTC)[reply]
Who's good with chemical nomenclature?
Going to start proof reading and cleaning up the Glimepiride article, and have noticed two different sources stating the following IUPAC names. I can't distinguish between the two, so could someone who's good with naming large molecules have a look? Here are the two options:
I'm not quite in a mental state to confidently name a molecule quite that nightmarish, but do bear in mind that with molecules of that level of complexity you can very easily have more than one completely equivalent, and hence completely correct, name. If the sources are decent they may both be correct. ~ mazcatalk 23:09, 12 August 2010 (UTC)[reply]
Second one is at best incomplete, as it's missing stereochemical information about the cyclohexane ring. DMacks (talk) 23:21, 12 August 2010 (UTC)[reply]
The second name is missing a whole chunk in the middle, as you can see from the three opening brackets without closing brackets. The first name agrees with the name on ChemSpider (apart from the minor point of "phenethyl" vs. "phenylethyl"). Physchim62(talk) 07:30, 13 August 2010 (UTC)[reply]
August 13
Why expend effort finding pulsars?
According to this article, there are 262 000 computers running a program to locate pulsars in space. Is it worth the additional energy expenditure to know that there's a spinning star somewhere far away? We can't benefit from the information. We can't harness it in any way. If you're going to use energy in this way, wouldn't it be better to use it on something that can actually be used in the 21st century, like folding@home? ----SeansPotato Business 01:15, 13 August 2010 (UTC)[reply]
Probably the best answer would be a justification of theoretical astrophysics by some prestigious scientist. On the Method of Theoretical Physics. Are astrophysics, or high-energy physics, or other branches of theoretical physics useless? Probably, at this point in the development of our species and civilization, we are well past the regime where we can say that there is a practical engineering application to many of the remaining unsolved questions in physics. But we don't know for sure. And even if there is no practical purpose, there is still interest in finding answers to difficult questions; so there are still scientists working out on the far fringes of physics. Nimur (talk) 01:30, 13 August 2010 (UTC)[reply]
Pulsars can be used to measure the motion of distant systems because their super-regular 'pulses' slowly change frequency due to relativity. Also, pulsars are known to be neutron stars - and those can be used as 'standard candles' (see Cosmic distance ladder for details) which allows you to measure their distances. I'm sure there are a bunch of other clever things that can be figured out from their properties. SteveBaker (talk) 01:55, 13 August 2010 (UTC)[reply]
As for the power consumption: The thing is that this program is running on the computers of private individuals when they aren't being used for something else...they run this program instead of running a screen-saver. There is a small amount of extra power consumed when they are running the program versus idling - perhaps 50 Watts. But that number of 262,000 computers is not the number that are running 24 hours a day - that's the number of people who've logged onto the site and signed up their computers to use the site. It's perfectly possible that only a small fraction of those are running the program at any given moment. This makes it really hard to estimate the amount of power they are consuming. But if (let's say) a quarter of them are running the program at any given time - and each one is consuming 50 Watts extra because of that - that's about 3 MegaWatts - about the same amount of power that a railroad locomotive produces. It's not all that outrageous if the result is useful. To put it in context, the power consumption of the entire world is about 15 TWatts - so this expenditure represents about one five millionth of humankind's power consumption. If we're looking to save energy, there are much better places to cut. SteveBaker (talk) 02:15, 13 August 2010 (UTC)[reply]
aspartic acid page
severl paragraphs down they state that aspartic acid contributes a nitrogen to inositol. Don't they mean inosine? —Preceding unsigned comment added by 71.136.2.238 (talk) 02:30, 13 August 2010 (UTC)[reply]
Good catch. You know you fix this stuff yourself, right? 99.183.166.165 (talk) 03:12, 13 August 2010 (UTC)[reply]
Bloodletting
Would bloodletting be an effective treatment for hypertension? Don't worry--Im not looking for medical advice ( and I certainly wouldn't try to exsanguinate myself, since I don't even have hypertension), it just occurred to me. —Preceding unsigned comment added by 99.183.166.165 (talk) 03:00, 13 August 2010 (UTC)[reply]
There are two major problems with this approach. The first is that the body is actually rather good at compensating for a loss of blood. Our article on hypovolemia discusses some of the physiological responses which occur in response to blood loss; blood pressure tends to be maintained through constriction of blood vessels and the migration of water from tissues into blood plasma. Remarkably, the body can handle the acute loss of up to about 15% of its blood (roughly 750 mL) before it starts losing the ability to regulate blood pressure. After that, the combination of constricted blood vessels with elevated heart rate actually leads to an increased diastolic blood pressure. It takes the loss of about a third of one's blood (about 1500 mL) before you start seeing consistent declines in blood pressure — and then you're in a really bad way otherwise.
The second major issue is the chronic anemia that would result from the regular removal of so much blood. While the body can make up lost liquid (plasma) volume rather quickly, generating new red blood cells takes a bit more time. TenOfAllTrades(talk) 03:21, 13 August 2010 (UTC)[reply]
Bloodletting, however, has some positive effects on the renal system of a diabetic -- I asked about it in a lecture at Columbia University last October and the professor agreed with my assessment. That being said, there is this one benefit overpowered by many, many disadvantages unrelated to the way in which bloodletting can be beneficial, and since we can't isolate the benefit from the harm, bloodletting is not done in civilized medicine. DRosenbach(Talk | Contribs) 15:18, 13 August 2010 (UTC)[reply]
Interesting! What's the mechanism or specific beneficial effect here? DMacks (talk) 15:37, 13 August 2010 (UTC)[reply]
I have to call a [citation needed] on that one, DRosenbach. Can you at least provide a hint of the mechanism for your claim? "The professor agreed with my assessment" isn't quite enough. --- Medical geneticist (talk) 00:02, 14 August 2010 (UTC)[reply]
Counteracting Diseases
Just out of curiosity, what would happen if you had AIDS and Lupus at the same time, or maybe even AIDS and Leukemia. 99.114.94.169 (talk) 04:40, 13 August 2010 (UTC)[reply]
What you describe appears to be the opposite of comorbidity, although I'm not sure whether it would apply to those diseases specifically. ~AH1(TCU) 14:50, 13 August 2010 (UTC)[reply]
But what happen if you had both of these diseases? 99.114.94.169 (talk) 15:06, 13 August 2010 (UTC)[reply]
So if gravity is a pseudo force...
Then why is it considered one of the four fundamental forces? ScienceApe (talk) 04:47, 13 August 2010 (UTC)[reply]
I wouldn't describe gravity as a pseudo force because this description is normally used for fictitious forces in Euclidean space, and gravity is certainly a real force in Newtonian terms. In General relativity, gravity is not a force at all, of course, just a consequence of the curvature of space, but this is a non-Euclidean space (in fact a Pseudo-Riemannian manifold combining space and time). Dbfirs 07:33, 13 August 2010 (UTC)[reply]
Fictitious forces depend on the chosen frame of reference and in some reference frames they disappear altogether. First-order (local) gravitational effects disappear in a free-falling frame of reference. However, second-order (tidal) effects cannot be eliminated, so gravity does not fit the definition of a fictitious force. Gandalf61 (talk) 10:22, 13 August 2010 (UTC)[reply]
I am certainly happy to be corrected on this, but isn't the whole point of GR that what Newton called the gravitational force (e.g. the G) is actually just the path of least resistance in spacetime, because mass warps spacetime? That is, there is no "force of gravity," there is just a warping of spacetime by mass, and following the subsequent curves. Yes? No? This is, I am fairly sure, what I was taught, though I am sure it is an abstraction. It seems like we are perhaps getting hung up on the "force" terminology in strange ways. --Mr.98 (talk) 14:24, 13 August 2010 (UTC)[reply]
This is exactly the impression I was under. ScienceApe (talk) 02:24, 14 August 2010 (UTC)[reply]
Let's be clear: the idea that there are "four fundamental interactions" is one effort to explain the universe in the most simplified terms possible. The grand unified theory (which does not yet exist) will hypothetically unite all forces into one fundamental force interaction (or something). At present, we have "four" (or "three", because of the electroweak unification at high energy). So we basically can say that there are four (or three) fundamental ways that the universe "behaves". Gravity (with its mind-bending and space-bending behavior) is one of those ways. The other forces behaviors (strong nuclear, weak-nuclear, & electromagnetic interactions) do not behave in the same way - they do not warp the geometry of space-time to actuate their matter/energy interactions. Note that most descriptions call these four properties of the universe "fundamental interactions" and not "fundamental forces" - they are not really "forces." They are abstract generalizations of the ways that matter and energy come together to change their distributions. For normal, reasonable, human-sized scales of size, time, energy, and so on, these interactions look like forces - that is, they follow a Newtonian relation between position, velocity, acceleration, and the gradient of a potential energy field. Nimur (talk) 17:02, 13 August 2010 (UTC)[reply]
Sieve Map
I was reading up on urban planning and the services (such as water, medical etc) requirements involved and I came across the term "sieve maps" listed as a tool to enable analysis of services requirement, without any further explaination of what they are. I have carried out wikipedia and google searches for this term but nothing jumps out. Any ideas? Thanks 150.49.180.199 (talk) 05:09, 13 August 2010 (UTC) Mark[reply]
Perhaps a map that cross references with sieve analysis for each area? I'm not certain either, but that seems like a possibility. Killiondude (talk) 06:54, 13 August 2010 (UTC)[reply]
Spectrum
What is the difference between bandwidth and spectrum? —Preceding unsigned comment added by Kiranpatel1038 (talk • contribs) 08:12, 13 August 2010 (UTC)[reply]
In what context? Both are words that have a wide variety of related meanings - when you're talking about a range of frequencies available for transmitting data, the two can be roughly equivalent - but in other circumstances they can mean very different things indeed. Could you clarify? ~ mazcatalk 14:07, 13 August 2010 (UTC)[reply]
"Bandwidth" specifically refers to a measurement of the amount of spectrum that a signal occupies. Most commonly (i.e., for simple signals), "bandwidth" refers to the "3-dB bandwidth", i.e. the span of frequencies that the signal falls to to 50% of its peak power. In more specialized contexts, "bandwidth" can refer to other numerical measures of a signal. (This is especially true of complicated signals that do not have nice, peak-like spectra). "Spectrum" usually refers to the frequency spectrum, which is the representation of a signal in the Fourier domain (or frequency domain). These terms can often be used loosely and interchangeably, so if there is not much clarification provided, you should assume that these terms are referring to the vague concept of the frequency-representation of a signal. Nimur (talk) 16:56, 13 August 2010 (UTC)[reply]
Quantum mechanics and predicting the future.
Let's suppose you knew everything about the current state of the universe. Would the stochastic nature of quantum mechanics still render you unable to predict the future? Or is the future state of the wavefunctions deterministically dependent on its current state in this sense?--Alphador (talk) 09:17, 13 August 2010 (UTC)[reply]
Well one huge problem is you cannot "know everything about the current state of the universe" – there is a fundamental principle called the uncertainty principle that limits the detail to which you can "know" the state of the system. Physchim62(talk) 09:48, 13 August 2010 (UTC)[reply]
"Knowing everything" in this case means knowing the wave function. And yes, if you know the full wave function of the world at the present time you can predict (via Schrödinger's equation or the like) the wave function at any future time. The results of any particular measurement will of course be stochastic, with probabilities dependent on the wave function and subject to the uncertainty principle for non-commuting observables. --Wrongfilter (talk) —Preceding undated comment added 10:07, 13 August 2010 (UTC).[reply]
I've heard about the schrödinger equation, but I only have a rudimentary understanding of it. Could you give me an example of how you could use the schrödinger equation to predict the future state of the wavefunction?--Alphador (talk) 11:05, 13 August 2010 (UTC)[reply]
Well, it is a differential equation like so many others in physics. The equation itself tells you the rules of the game, i.e. in what state will the system be in a moment when it is in such and such a state right now. Schroedinger's equation contains the Hamiltonian operator which defines the system that you're looking at, how it interacts with the outside world and so forth. To solve any differential equation you need to specify initial conditions, that would be the state (the wave function!) now (or at any given point in time). The solution will then tell you what state the system will be in at any other time in the future (or in the past). --Wrongfilter (talk) 13:41, 13 August 2010 (UTC)[reply]
(ec)This is one of the Big Questions, isn't it, that people come to rather different positions on.
My understanding is that the wavefunction is presumed to evolve in a deterministic way (otherwise, where would the new information come from?), so if like some updated Laplace's demon you could have a complete knowledge of the wavefunction now, and could somehow iterate that forward, then you would have a complete knowledge of the wavefunction at a particular time in the future.
However, you would then have the question of interpreting what that wavefunction meant. Specifically, according to decoherence, it is suggested that that evolved wavefunction is likely to evolve into an almost perfect product of factor wavefunctions for a number of essentially disjoint non-interacting separate distinct "histories" -- the multiple universes in many worlds interpretation language.
You would therefore be able to predict these different, effectively disjoint, outcomes; and even assign them probability-like weights; but not say which one your own future consciousness will associate with.
That at any rate seems to be a thumbnail sketch of one answer that some people seem to find acceptable.
But I suspect it depends on quite another set of cans of worms -- for example, with reference to what is your wavefunction of the universe defined? What absolute scales or place or time? They surely don't exist. How can such a wavefunction have any information content? Information implies the reality of counter-factual states from which the current state can be distinguished. But how can states that are by definition counter-factual have any reality? etc, etc.
To do physics, we essentially have to make approximations -- separating the "system of interest" from the "background", and then assuming the background is homogenous, uninteresting, unimportant -- an external scale through which we can define place, time, or any other variable of the system of interest. And of course most of the time this works brilliantly. But I suspect that it becomes a serious problem, if we want to start talking about a "wavefunction of the universe", which properly would have to absorb all of that background into itself - leaving what to define the wavefunction against? Such questions may even become significant, even if we do not go to such lengths. For example, I suspect we regularly make a change in the system/background approximation when we introduce a "measuring apparatus", and that is why that appears to produce a distinct break in determinism.
So: decoherence gives one answer to your question, but the terms in which you ask it perhaps in themselves open up deeper questions.
I'm interested to see what comments other answerers give. Jheald (talk) 10:12, 13 August 2010 (UTC)[reply]
The uncertainty principle come from my opinion from movement back and forth to the past and the future . thanks —Preceding unsigned comment added by 84.228.231.7 (talk) 13:39, 13 August 2010 (UTC)[reply]
Science is not interested in your opinion. It is interested in clearly defined theories that explain empirical results. --Tango (talk) 00:12, 14 August 2010 (UTC)[reply]
If you know the future , you can explain results in any way you like . thanks —Preceding unsigned comment added by 212.199.175.93 (talk) 04:18, 14 August 2010 (UTC)[reply]
Even if you did know everything about the curent state, determinism is not proven so it would be near-impossible to predict anything with 100% certainty and accuracy. ~AH1(TCU) 14:47, 13 August 2010 (UTC)[reply]
Indeed. Also, this recent article has a very interesting perspective on quantum mechanics in an infinite universe. Count Iblis (talk) 14:55, 13 August 2010 (UTC)[reply]
Frog with yellowish stripes
I occasionally find frogs with two yellowish stripes running down their backs. It mentions them in the grass frog article, but does not give any specific species. All I have to give for pictures is these twoblurry pictures to give. Can anyone identify them? I do not see anything in Frogs in New Jersey or in the NJ.gov index of frogs and toads in New Jersey. Thank you. --Chemicalinterest (talk) 12:36, 13 August 2010 (UTC)[reply]
It seems to be a Pickerel Frog, where maybe its a morph that does not have dominant spots or maybe its a young frog where the spots have yet to completely fill in. 99.114.94.169 (talk) 15:28, 13 August 2010 (UTC)[reply]
Pickerel frogs are common (this picture is a clear example). That's how they normally look. --Chemicalinterest (talk) 15:50, 13 August 2010 (UTC)[reply]
What primates other than humans are good swimmers?
If you want to talk about 'capacity' that's a rather difficult question IMHO. I wonder whether you could teach a chimpanzee or orang utan or gorilla to be good swimmers with enough effort. This [23] claims orang utans and gorillas can't because of their centre of gravity is in their necks and sternums, but as with the person writing, I'm sceptical whether that's the whole story. These two refs have various discussions of swimming chimpanzees, the general conclusion I draw from that is it's likely to be possible [24][25] and a chimp may even be able to outswim an olympic swimmer. Note that if you can't teach an animal to swim, it may as much as anything be because the animal lacks the learning capacity or intelligence necessary for you to be able to teach it. It's also likely to be difficult to prove whether or not you can teach whatever animal how to swim without significant effort, which would likely have to start at learning to teach the animal effectively. In other words, the best answer may be most primates may have it, but we'll probably never really know. Nil Einne (talk) 17:17, 13 August 2010 (UTC)[reply]
Long-distance swimming says that a few humans are capable of swimming 100km without a break - over 800 people have completed 30+km swims across open ocean and there are many Marathon swimming competitions in which hundreds of people are able cover 5 to 10km distances in open water. Ironman Triathalon events involve 3 to 4km swims (along with biking and running) and are fairly commonplace events that most moderately fit humans could train to complete. Almost all of us can comfortably swim a hundred meters. Can anyone name one other primate that can come even close to doing that? No? Me either. I conclude that we are likely to be by far the best adapted primate for this kind of thing. We have long limbs - we are mostly hairless (we don't get water-logged) - we have our center of gravity in the right place and we have vast amounts of stamina for covering long distances. SteveBaker (talk) 00:28, 14 August 2010 (UTC)[reply]
How large a factor is behaviour, though? Humans can only swim several kilometres following extensive and specialised training and only do so with the motivation of challenging themselves and proving their abilities. I can't see a wild primate attempting such a thing. They might well be capable of it if they did train for it and actually attempted it. --Tango (talk) 00:38, 14 August 2010 (UTC)[reply]
Test on toes
What is the name of the test or sign whereby the doctor holds one toe and pushes it up or down while the patient's eyes are closed. The patient then advises whether it was moved up or down. Kittybrewster ☎ 15:55, 13 August 2010 (UTC)[reply]
Never heard of that test, but the concept of what it's testing for sounds like proprioception.20.137.18.50 (talk) 16:04, 13 August 2010 (UTC)[reply]
I believe that's called the "this little piggie" test. sorry... Vespine (talk) 23:56, 13 August 2010 (UTC)[reply]
Cheap vehicles
what is the cheapest best quality used car saying all are taken care the same? Ford,chevy,mustang,honda,etc.? —Preceding unsigned comment added by 98.221.179.18 (talk) 15:56, 13 August 2010 (UTC)[reply]
You need to think what the purpose of the car is. Reliability wise Honda are very reliable, well made cars (at least the ones we get in the Uk). It really depends on the use though - there will be a number of bests - small-car, the best 4x4, the best people carrier, the best pick-up and so on. That said any 'best' is really just a matter of opinion, but I would recommend using something like Parkers Guide (or whatever the US equivalent is - assuming US based on Chevvy/mustang). ny156uk (talk) 16:39, 13 August 2010 (UTC)[reply]
This question has been removed, per the medical advice guidelines.
We cannot offer medical advice. Please see the medical disclaimer. Contact an appropriate medical professional. We have articles about the various drugs so you can learn about them and maybe find links to more information about them. DMacks (talk) 16:27, 13 August 2010 (UTC)[reply]
This is about as clear a violation of our medical-advice guidelines as ever. You need to consult with your doctor to discuss any effects of any medication the doctor has prescribed to you. Your doctor can help you decide the right course of action. Nimur (talk) 16:49, 13 August 2010 (UTC)[reply]
Floating islands
Are there any inhabited islands that float around the sea? I don't mean like plate tectonics where everything is moving because of lava 82.43.88.151 (talk) 18:00, 13 August 2010 (UTC)[reply]
Sure enough we have an article on Floating islands. Some of those are inhabited, see the second part of the article. --Dr Dima (talk) 18:17, 13 August 2010 (UTC)[reply]
How do people find the wavefunction of an elementary particle? Often in quantum mechanics problems you are simply told what it is, I would like to know how people determine the wavefunction.--Alphador (talk) 22:03, 13 August 2010 (UTC)[reply]
Wavefunctions are linear combinations of the eigenfunctions that solve Schrodinger's equation. Solving the latter in any particular case requires specifying the Hamiltonian operator, which includes a generic part related to kinetic energy and specific part related to how the particle(s) potential energy can be expected to change as a function of position and/or time. In most cases, the potential part is specified by the solver in terms of the fundamental forces involved (e.g. electromagnetism) and the details of the larger environment within which the particle is being studied. Once the potential field is specified, finding the eigenfunctions is an exercise in solving partial differential equations (i.e. pure math). Exact solutions generally only exist for fairly simple systems, so often the eigenfunctions are found either via numerical approximation or by approximating complex systems in terms of simpler systems that are analytically solvable. Finding a precise wavefunction to match the system's state is then a problem of finding the precise linear combination of eigenfunctions that match some specified initial conditions, i.e. a boundary value problem. Dragons flight (talk) 22:33, 13 August 2010 (UTC)[reply]
Will scars ever be possible to remove/are they possible to remove?
Not seeking medical advice, and already looked up the wikipedia article on scars but it seems outdated. I was captivated by this story on the Extra-Cellular Matrix and how it helped regrow a man's finger with-out scar tissue.
Per our article on scars, the American Association of Dermatology notes that no scar can be completely removed, though many can be considerably reduced. We cannot say whether or not perfect removal will someday be possible. — Lomn 02:02, 14 August 2010 (UTC)[reply]
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![[19]](https://en.wikipedia.org/wiki/File:Flag_of_East_Germany_with_cut_out_emblem.svg){kind=link}
We cannot offer medical advice. Please see the medical disclaimer. Contact an appropriate medical professional. We have articles about the various drugs so you can learn about them and maybe find links to more information about them. DMacks (talk) 16:27, 13 August 2010 (UTC)