Wikipedia:Reference desk/Archives/Science/2011 June 12

= June 12 =

What biotech company is doing the study that replicates ccr4 immunity for people with hiv?
A few months ago I read a news article that a biotech company in South San Francisco or San Bruno is in the middle of human trials for a therapy where people with HIV are infused with t-cells that are adapted to not allow hiv to enter them similar to the ones that people with natural immunity have and that it was promising research because these t cells were replicating themselves in most people in the trial on their own. I want to find this article as some people I told don't believe me or want to know more and I want to look into the company, I also want to expand the article on the HIV timeline and Hiv treatment articles.Thisbites (talk) 00:32, 12 June 2011 (UTC)


 * I think this is Irvin S. Y. Chen, head of the UCLA AIDS Institute.  "He is currently engaged in a start-up company for HIV-1 genetic therapy involving collaborations with UCLA, Salk Institute, and Cal-Tech."  Also, .   says he formed the company with David Baltimore, former president of Caltech.  There are various bits of flotsam  floating around that link Chen and Baltimore with Calimmune, a California company headquartered in Tucson, Arizona? - it isn't clear to me that this is the company. Wnt (talk) 02:40, 12 June 2011 (UTC)


 * I distinctly remember that the trials were going on in San Bruno/South San Francisco.Thisbites (talk) 05:05, 12 June 2011 (UTC)
 * Well, ($20 million) makes it sound like Calimmune is doing just the right kind of study to match your criteria: "methods to transduce autologous hematopoietic progenitor stem cells (HPSC) with a viral vector delivering a specific interfering short hairpin RNA (shRNA) designed to block production of CCR5. In addition, since combination treatment strategies are often more effective than monotherapy, the applicant proposes to add a second inhibitory component to the vector, a gene encoding an inhibitor of virus-cell fusion."  I should note however that there are considerable obstacles that come to mind right off.  First, all sorts of gene therapy have been under the cloud of potential cancers when DNA goes into the wrong spot in the genome, and these immune cells will be undergoing rapid turnover in people prone to AIDS lymphoma already.  Next, RNA interference isn't 100%.  They say the cells may be protected anyway since the virus is less likely to bind, but is there really an excess of virus?  If not, then the virus can just drift past a hundred missing receptors and bind the one that is there, without any delay.  Finally, there's the matter of whether the gene therapy can be "rejected".  Every once in a blue moon I've read the strangest claims about DNA being rejected by the immune system, or antibodies somehow getting into the cytosol of the cell.  More recent publications include  and, a less radical claim that viruses bring antibodies into the cell with them that trigger special interfering factors inside the cell.  But the point is this: we don't know how the body will respond to long term gene therapy.  I can picture for example that the hairpin RNAs found together with the antibody-tagged HIV virus will be tagged somehow as foreign RNA, diced up, and the inserted genes end up being tagged as "spam" by methylation or chromatin changes. Wnt (talk) 18:23, 12 June 2011 (UTC)


 * Also that those links are for bone marrow/stem cell style treatments. What I read was not a bone marrow transplant. It was modified blood of the patients themselves to alter their t-cells so that they do not have ccr4 receptors. Furthermore there was mention that it was believed to cost 90-120 thousand dollars for the one-time treatment and that that was considered good since hiv medicines can cost upwards of 18k a month.Thisbites (talk) 05:09, 12 June 2011 (UTC)


 * I think you mean CCR5-Δ32. I heard some stories about a "healing" (remission below detectable levels) taking place after a bone-marrow transplantation of a donor with the CCR5-Δ32 mutation. Which makes sense as it replaces the T-cells with cells having some receptors missing. I also know of companies which offer genetic testing for the CCR5-Δ32 mutation. There is evidence that people with CCR5-Δ32 mutation are less likely to develop aids, and respond better to treatment. It may also be possible that people with CCR5-Δ32 are less likely to get infected, but this has not been researched properly at the moment and might be wrong. Introducing a CCR5-Δ32 mutation into someone's blood might be possible, but I guess a bone-marrow transplantation is a much easier, and already feasible way (even though much more risky). I don't know about recent research though --helohe (talk)  08:22, 12 June 2011 (UTC)


 * Also note that this treatment, even if successful, would make the person more susceptible to the West Nile virus. On the other hand, it would also give him/her better immunity against smallpox (and possibly black plague as well). -- An American ultranationalist 67.169.177.176 (talk) 02:21, 13 June 2011 (UTC)

Vulcan hearing
It is well known in the Trek universe that Vulcan's have superior hearing. For the most part, it seems people associate this with the shape of their ears. I know that animals can physically move their ears to hone in on a sound (e.g. deer listening for predetors). Since Vulcans cannot move their ears (like an animal, anyway), what affect (if any) does the shape of their ears have on their ability to hear? 99.250.117.26 (talk) 01:54, 12 June 2011 (UTC)


 * I'm not a Star Trek fan, so I can't tell you for sure, but generally larger ears (such as those of the elephant or the fennec fox) are better at capturing and focussing sound waves, which translates to better hearing. 67.169.177.176 (talk) 02:09, 12 June 2011 (UTC)


 * There are stores that sell "Vulcan ear" costumes to those Trekkies... they don't work as hearing aids. I think external ears in animals that enhance acuity are distinguished more by a concave shape, which allows them to concentrate sound to a single point. Wnt (talk) 02:14, 12 June 2011 (UTC)


 * I can't see the shape of their ears making any difference. I don't think it's ever been said on the show that they do (that they have superior hearing is stated, but not the cause). Vulcan's also have superior strength and longevity. I think they are made to be so superior physically so that it's all the more impressive when the emotional humans always better them. --Tango (talk) 13:13, 12 June 2011 (UTC)


 * This is, of course, what is called fiction, but do keep in mind that the Vulcan (Star Trek planet) atmosphere is less dense, and hence carries less sound energy. Presumably Vulcans have to have more sensitive hearing to have hearing as good as other species which live in thicker atmospheres. μηδείς (talk)


 * Interesting... Do they also have bigger lungs and better hemoglobin to prevent hypoxia in such a thin atmosphere? 67.169.177.176 (talk) 02:06, 13 June 2011 (UTC)


 * The "Vulcan equivalent of hemoglobin" is diagrammed here. Clarityfiend (talk) 02:27, 13 June 2011 (UTC)


 * All I can say to that is, they must be a really crabby bunch... 67.169.177.176 (talk) 06:40, 13 June 2011 (UTC)

The shape of the ear does have an effect on hearing. Sound pressure levels at the human eardrum are typically 7-18dB higher in the 1 kHz to 6 kHz frequency range (essential for good speech reception) than they would be without the pinna. Table 1 on this page gives a breakdown of this. Si1965 (talk) 12:11, 13 June 2011 (UTC)

Probability Of Destruction In "Super 8"
I asked this question in the "Entertainment" section of the Reference Desk as well, but I feel that it pertains to both categories. Hey everybody. I've been wondering something about some of the special effects in the newly-released movie Super 8, which came out in theaters on June 10th, 2011. In it, there is a horrible train crash that involves a mid-sized pickup truck (think mid-90's F-150) driving head-on at full speed into a diesel freight train travelling at well over 50 mph. The collision immediately results in an explosion and the locomotive grinds to a halt. But the filled freight cars behind it continue to shoot forward under their own momentum an end up flying everywhere. This continues to occur as the rear of the train continues moving forward. What makes me think that this is unlikely is the immense speed at which the rear of the train continues to move. I mean, of course the effects of inertia would cause the cars to continue moving, but would they really move at such speed? If you have not already seen the movie, here is a link to that particular scene on the Internet Movie Database: Clip 1, and here is another that is longer, but shows a more complete view of the crash: Clip 2. If anybody could help explain or describe this better to me, it would be much appreciated. Basically, all I want to know is, is this scene probable, or is it simply "movie magic" that looks realistic, but defies the laws of physics. Thanks! Stripey the crab (talk) 02:49, 12 June 2011 (UTC)
 * Those missing links to IMDB are Clip 1 and Clip 2. Red Act (talk) 02:54, 12 June 2011 (UTC)
 * Perhaps you should have responded to and thought about my response on Reference desk/Entertainment before posting here. The film is science fiction, not science. Putting the same question on two ref desks means that responses are dispersed. Not a good move. HiLo48 (talk) 03:00, 12 June 2011 (UTC)
 * Red Act, thanks, I forgot about that. :P And User:HiLo48, sorry about that.  I posted it here, then went back to check at the Entertainment section.  And despite the responses being dispersed, it's not that hard to navigate back and forth between two web pages, or easier still, two tabs.  As for being a bad move, on the contrary - you expose the question to more people.  I usually spend my time strictly on the Science section.  I hadn't even visited the Entertainment section before today, and I'm sure I'm not the only one out there who behaves similarly.  But thank you for your response, and for your time.  It is much appreciated!  :)  Stripey the crab (talk) 03:12, 12 June 2011 (UTC)
 * It's clearly a CGI train, so of course it's not going to precisely do what a real train would do. However, I don't see anything in either clip that super obviously defies the laws of physics.  Train crashes can indeed be immensely destructive, as a Google image search readily shows.  Red Act (talk) 04:05, 12 June 2011 (UTC)
 * What was less credible to me was that the truck's driver was still alive, the kids weren't harmed, and their camera and car survived. But it was sill a great movie. HiLo48 (talk) 04:47, 12 June 2011 (UTC)
 * IIRC, one of the wagons of the train was labeled "explosives". so I guess "theoretically" is is possible. but its unlikely, I have seen a few traincrashes/de-railings and usually I guess it just turns the wagons over squeezes them together etc (similar to what would happen if you do the same in a model-train at high speed)...
 * Also I don't think a pick up truck would be enough to do much to a train. There have been accidents where some car was in the middle of a crossing, when the train struck, and I guess it just "catapults" the car away, with minor damage to the train. --helohe (talk)  08:13, 12 June 2011 (UTC)


 * If a pickup truck crashes headon into a locomotive pulling a long freight train, the locomotive itself is so more massive than the pickup that the collision could not possibly bring the locomotive to a halt. The loco and the freight cars would continue at about the initial speed until the application of the train brakes brought the train to a halt. Train brakes are air operated and designed to bring the locomotive and cars to a smooth and safe stop, without the freight cars running over the magically stopped locomotive. The whole scenario sounds bogus. Standard Hollywood garbage, its physics about on a par with Roadrunner cartoons. If the lead locomotive somehow derailed, or it it hit a massive gravel truck or truck load of rolls of steel, the scene would be more plausible. It is still a great scene, cinematically, and I will make it a point to see the movie. Edison (talk) 00:50, 13 June 2011 (UTC)


 * Edison is exactly correct, the locomotive would not come to a dead stop given it outmassed the truck but the cars behind would have continued at the same speed they were being pulled by the locomotive. What really effs up a movie is when a falling object falls faster than gravity because Catwoman (film) jumped downward. μηδείς (talk) 01:20, 13 June 2011 (UTC)


 * The truck wouldn't need to itself bring the locomotive to a stop. If the locomotive is derailed by hitting the truck (which is conceivable) it's going to slow down pretty fast which could cause the subsequent cars to pile up.  If the train happens to be packed full of explosives (which I have to assume it is by the way everything starts exploding) I guess it could be pretty catastrophic. Rckrone (talk) 04:35, 13 June 2011 (UTC)


 * I still don't buy it -- even if the engine is derailed and the other cars pile up behind it (pretty unlikely given the small size of the truck), modern high explosives are very stable and will not detonate simply from being jostled in this manner. In order to explode in this manner, the train would have to be carrying either some kind of high explosives with extremely high sensitivity to impact, such as nitroglycerin (implausible, since these types of explosives are no longer used as such, nor transported), or else live munitions with detonators fitted (TOTALLY implausible -- munitions are ALWAYS transported with detonators removed, precisely to avoid a disaster of this type).  Or else the train would first have to catch on fire and the flames spread to the explosives (which is possible, but would take a while).  But then again, most people don't know what REALLY happens when a train hits a pickup truck, much less what happens when a train derails.  And all those peddlers of cheap thrills capitalize on this scientific ignorance to make big bucks... 67.169.177.176 (talk) 07:05, 13 June 2011 (UTC)
 * Modern explosives tend not to explode even if they catch fire -- it typically takes a combination of pressure and heat to get them to produce anything but an intense flame. --Carnildo (talk) 01:36, 16 June 2011 (UTC)
 * See what I mean? The train won't explode in this scenario, even if it jumps the tracks -- period! 67.169.177.176 (talk) 08:34, 16 June 2011 (UTC)

Cold fusion applicability
Reading cold fusion confuses me — I understand somewhat of what the proponents claim is happening, but I fail to see the applicability. Let's say that tomorrow someone shocks the scientific community and conclusively proves to everybody's satisfaction that cold fusion really is possible. What possible applications are there for it, aside from reducing the prices for manufacturers of helium balloons? As far as I know, all our uses for fusion rely on the significant amounts of energy that result, whether using the explosion as a powerful weapon, or (if we can figure it out) using a slower process to generate electricity with the very non-cold temperatures that result. Nyttend (talk) 12:17, 12 June 2011 (UTC)


 * The most common idea that I've seen is that you scale it up to the level of "personal reactors" that would power your household, heat your water, power your car, whatever. It's meant to be small-scale, personal, clean power. (This is part of the alleged conspiracy theory — it would destroy the need for centralized utility companies, oil companies, and so forth. So they've rallied against it, blah blah blah.) Obviously the prototypes don't really intend to do that, any more than Hahn and Meitner's experiments weren't a fission reactor (or bomb). If we could use hot fusion on that scale, we would, but hot fusion requires starting temperatures on the order of millions of degrees Fahrenheit, so getting back what you put into it requires liberating a huge amount of energy. --Mr.98 (talk) 12:49, 12 June 2011 (UTC)


 * Yes, you are right. Cold fusion would be useful as a source of energy. That's it. That is a extremely important applicability which makes me wonder why you say you fail to see the applicability. Dauto (talk) 18:42, 12 June 2011 (UTC)
 * I think the question is: if it is cold, then it doesn't generate energy that we can transform into electricity. So is the word cold in cold fusion misused? Or can we generate elecricity without heat or explosions? --Lgriot (talk) 10:25, 13 June 2011 (UTC)
 * Cold here is a relative term. Cold fusion still leads to temperatures high enough to produce electricity. Dauto (talk) 16:39, 13 June 2011 (UTC)
 * To put it in perspective, the temperature inside of a conventional coal based electric power plant is of the order of 1000 K while the temperature required for hot fusion is of the order of 100 000 000 K. There is plenty of space in between that would be hot enough to produce electric power but too cold to generate conventional fusion. If fusion is achieved in that range it would be considered cold fusion. Dauto (talk) 16:48, 13 June 2011 (UTC)
 * Just to clarify (perhaps): the "cold" and "hot" here refer to the temperatures necessary for ignition of the fusion reaction, not to the heat of the reactions themselves. --Mr.98 (talk) 14:10, 14 June 2011 (UTC)


 * You might be interested in Fusor. 5BYv8cUJ (talk) 18:35, 13 June 2011 (UTC)
 * Which, to clarify, is hot fusion. --Mr.98 (talk) 14:10, 14 June 2011 (UTC)

Diet by cold/hot air
Would it be an effective diet just to be outside our thermal comfort zone? This way our body would have to burn calories to keep us cool or warm. Which way would be more effective - hotter or colder? Quest09 (talk) 12:32, 12 June 2011 (UTC)
 * Cold. You don't really use energy to cool down, that would be counter-productive since using energy almost always converts it into heat (energy is never created or destroyed, remember). You cool down by sweating and redirecting blood to the skin. That doesn't really take energy. When you're cold, though, you need to use energy to generate heat (for example, by shivering). I don't think it would be a particularly good way to burn calories, though - you would need to be dangerously cold for it to have a significant effect. You would be better off going for a nice jog. --Tango (talk) 13:22, 12 June 2011 (UTC)
 * But, if you need 1Cal to heat one Kg of yourself 1 °C, and you put the A/C 3 °C below the comfort zone, you'll end up spending a lot of Calories each day (provided you don't get hungry in the cold), won't you? Quest09 (talk) 13:40, 12 June 2011 (UTC)
 * No, because food calories are a thousand times larger than the calories for heating water. (I'm not making this up, see calorie.)  &#x2013; b_jonas 08:50, 13 June 2011 (UTC)


 * He got it right. One food Calorie is one kg (1000 grams) of water for 1 °C.  Thermodynamic calories are one gram of water for 1 °C.  Hence by saying kilogram he already included the factor of 1000.  Dragons flight (talk) 18:56, 13 June 2011 (UTC)


 * Hmm, okay. Sorry.  &#x2013; b_jonas 09:46, 15 June 2011 (UTC)


 * You might be interested in Brown adipose tissue. 5BYv8cUJ (talk) 14:03, 12 June 2011 (UTC)


 * You'll gain weight when you attempt to change the energy balance like this, without drastically cutting back on your energy intake. This is because the body attempts to maintain a stable body weight on the long term. So, unless you go outside the range where the feedback mechanisms the body uses break down, you won't lose weight. Instead, the feedback mechanisms will lead to the opposite result, a modest weight gain, because it will take measures against a perceived threat to its long term energy reserves.


 * Incidentally, the article Mike Stroud (physician) says that Antarctic explorers can use over 10,000 calories a day (which I've seen described by a simple calorie count of the food consumed from some much earlier expedition). Wnt (talk) 17:59, 12 June 2011 (UTC)
 * Recent research has pointed to something else you can do to lose weight without dieting: Sleeping for longer. This is because during sleep the metabolic rate is slower. Naively, you may think that you'll gain weight if you sleeep better and longer. But what really happens is that the metabolic rate during sleep is regulated as part of all the feedback mechanisms to maintain a stable weight. Then, because the body will regulate the amount of energy reserves such that it can do without food for some given amount of time, a longer sleeping period means that you need less fat. You could say that the time you sleep counts as virtual fat, and the more virtual fat you have, the less real fat you'll have. The body apparently keeps track of how much you sleep on you get on the long term and uses that to regulate to what degree the fat cells are filled. Count Iblis (talk) 15:12, 12 June 2011 (UTC)
 * I personally find that it is much easier to lose weight when it is hot. Not because the heat is burning calories, but the heat makes me not feel like eating.  Googlemeister (talk) 17:31, 13 June 2011 (UTC)

Electronic compass
I've just bought a GPS unit that includes an electronic compass, i.e. it supposedly doesn't rely on GPS data and functions when stationary, unlike cheaper GPS units which can only determine direction when moving. I was curious to know how the electronic compass worked, but there isn't a Wikipedia article, and the compass article refers readers to fibre optic gyrocompass, so I created a redirect to that article from electronic compass. However, reading the article on fibre optic gyroscope (to which fibre optic gyrocompass refers me) I am not sure I have done the right thing. Does my Oregon 450 GPS unit really contain a laser and lots of fibre optic cable? If not, how does the "electronic compass" work?--Shantavira|feed me 13:27, 12 June 2011 (UTC)


 * It probably does it with a magnetoresistance sensor like the Honeywell HMC6352 module described at www.cypress.com/?id=1128 -- Finlay McWalter ☻ Talk 13:43, 12 June 2011 (UTC)


 * A better link is this Philips note (the Philips parts are just the sensor, the Honeywell above implements much of what the Philips note discusses). -- Finlay McWalter ☻ Talk 13:46, 12 June 2011 (UTC)


 * There is a WK article about that: magnetometer (aka as digital compass). Quest09 (talk) 13:50, 12 June 2011 (UTC)


 * Thanks. Maybe someone more knowledgeable than me could tweak the various compass articles.--Shantavira|feed me 15:34, 12 June 2011 (UTC)

first magnet
Reading the question above, I wondered how the first magnet / compas needle was created. The only way I can think of to create a magnet is using an electromagnetic field applied to some iron or similar which would require electricity. then again to create electricity (besides using a chemical process like a battery) one needs a magnet to induce an changing electric field in a coil. --helohe (talk)  16:47, 12 June 2011 (UTC)


 * A lodestone is a natural magnet. You can take a non-magnetic piece of iron (like a needle) and magnetise it by rubbing it in one direction with a lodestone. -- Finlay McWalter ☻ Talk 16:50, 12 June 2011 (UTC)
 * The English scientist William Gilberd (1544 – 1603) was the first person to study magnetism in any scientific way. He found out how to manufacture magnets as Finlay describes - only natural lodestones were used previously. He also disproved the widely held belief that compasses could be demagnetised by contact with garlic! He was the first to suggest that the earth had magnetic poles - it had previously been thought that there was a big magnetic island in the Arctic that all compasses pointed to. He is credited with coining the word "electricity". He deserves to be better known, but few have heard of him outside of his home town of Colchester. Alansplodge (talk) 17:37, 12 June 2011 (UTC)
 * Whether by rubbing amber or by using an electrochemical reaction such as the Baghdad Battery, it is possible to make electricity without using magnets. Wnt (talk) 17:54, 12 June 2011 (UTC)
 * The Baghdad Battery is a likely hoax. Lodestones may have been created by lightning strikes in soil containing iron ore. Edison (talk) 00:43, 13 June 2011 (UTC)
 * wow, thanks. I haven't heard of lodestones before, very nice :) --helohe (talk)  19:26, 12 June 2011 (UTC)

Interchangeability of USB wall chargers
I have a Sandisk Sansa Clip+ which is charged over USB (mini-B) and doesn't come with a wall charger, and I have a Motorola mini-USB cell phone wall charger, model FMP5185B, input 100–240V, 50/60Hz, output 5.0V, 550mA. Can I safely charge the one with the other? This thread is full of people saying it's okay, but this thread makes me worry. If there's any doubt, I'd rather not do it. -- BenRG (talk) 19:02, 12 June 2011 (UTC)
 * I'm not an expert but those wall chargers just emulate a normal usb cable from a computer so they should be using the same specification. The USB article lists normal usb power as "500–900 mA @ 5 V" which is the same as yours AvrillirvA (talk) 22:41, 12 June 2011 (UTC)
 * As I remarked recently on the RDC, all wall AC/DC adapters for mobile phones or heck nearly everything I've seen in the past 4+ years or so have been SMPSs. There may be some traditional linear transformer only wall AC/DC adapters with fullsize/mini/micro USB sockets or plugs but I doubt they we were ever common. Definitely all image search results for the motorola razr v3 adapter I find seem to be SMPSs. Of course since you actually have the adapter you can probably tell by the size and weight. However since the specs for your device say it supports 100–240V, it obviously has some regulation and is almost definitely a SMPS.
 * Also if you overcharge li-ion batteries they may explode fairly violently. Since manufacturers find this undesirable, they tend to design devices to avoid this. If you supply too high a voltage you may kill the device or charging circuitry. You're far less likely to overcharge the batteries. (Li-ion batteries also should generally be charged with a CC-CV charging profile. And the CV stage should generally be 4.2V regulated to with +/- 0.05V or better, there are specialised chips for this which may be what most manufacturers use but in any case this isn't something you handle by simply dropping the voltage of a 5V USB supply where +/- 5% is within regulation.)
 * Finally if you're drawing a higher current then the AC adapter can supply and there's no safety or fuse, you risk damaging the adapter, perhaps even causing a fire. Alternatively the voltage may drop too low (as the poster sugggested) and the device and charging circuitry won't be able to function correctly. There's a slight chance this may result in an incomplete charge, more likely you're just get random problems or the device/charging won't work at all.
 * In other words, nearly all the claims of the person in the second link are questionable.
 * BTW the EU has defined a Common External Power Supply. The Open Mobile Terminal Platform agreed to something similar. While your devices appear to predate that (since microUSB not miniUSB is the agreed standard) the idea is that you can use any charger.
 * Nil Einne (talk) 01:42, 13 June 2011 (UTC)
 * The power supply is small and light, not one of the big-and-heavy wall warts that were all the rage a decade ago, and I assume the Clip+ won't try to draw more than 500mA since that's all that USB guarantees, so I guess it's safe. I may still be too scared to try it, though. Thanks for the replies -- BenRG (talk) 06:36, 15 June 2011 (UTC)

Identifying small trilobites in Ordovician-age rock
Hi. I have some samples of Ordovician fossiliferous limestone. Some of those samples may contain fragments of trilobites, and I would like to identify them using specific features if possible. How do I identify the body fragments and distinguish them from other fossils, a partial list being bryozoans, gastropods, porifera, crinoids, brachiopods, and possibly others such as cephalopods and ostracods? Thanks. ~ AH1 (discuss!) 20:17, 12 June 2011 (UTC)


 * Take a course in invertebrate zoology. Look for a continuos closed chitinous exoskeleton.  Contact Robert Loveland of Rutgers University.  Look for a segmented body and jointed limbs.  Publish any pictures yo have and ask for comments if you are not sure.  μηδείς (talk) 22:35, 12 June 2011 (UTC)

Pain & C-Fibers
I'm having a hard time tracking down an answer for what I was assuming was a straightforward empirical question: People argue that pain is possible even without c-fiber stimulation. But are there cases on record of normal, psychologically healthy adults who complain of pains that cannot be correlated with any kind of c-fiber activity? I.e., cases where an otherwise normal (I say that to sort of weakly rule "hypochondriacs" or, generally, people we have reason to doubt make veracious claims about their physiological states) adults sought medical help for pains which subsequently could not be grounded to any neurological goings-on.

Thanks! — Preceding unsigned comment added by 99.32.190.71 (talk) 20:20, 12 June 2011 (UTC)


 * I think phantom pain, and neuropathic pain of the "central" type, are pretty clear examples. C-fibers contribute to phantom pain in some instances, but some of the worst pain comes in people for whom all the relevant C-fibers appear to have degenerated. Looie496 (talk) 00:31, 13 June 2011 (UTC)


 * I would say it's true, since a person is able to experience pain in a dream. Plasmic Physics (talk) 03:51, 13 June 2011 (UTC)


 * Really? In all my life I never have.  Heck, when I had the gout I would sometimes avoid moving my legs for up to an hour after waking, simply to keep the sleep paralysis going so I wouldn't feel the pain. Wnt (talk) 05:14, 13 June 2011 (UTC)


 * It is actually a quite remarkable fact that people are not able to experience pain in dreams. You can dream that your legs are blown off by an explosion, but you will not feel any pain when it happens.  Other forms of distress are common, such as a feeling of suffocation or overheating, or a need to urinate. Looie496 (talk) 06:38, 13 June 2011 (UTC)
 * That is wrong. I've felt pain in dreams, and I can't find any sources stating it's impossible to feel pain a dream. I understand that sometimes something which would cause pain in real life doesn't in a dream or the perception of pain is different in dreams, but that is very different from never being able to experience pain in dreams 82.43.90.27 (talk) 21:04, 13 June 2011 (UTC)


 * I speak from personal experience, I had my hand chewed on and I can tell you: it wasn't as painful as you'd think, but still very much (like a painfully firm handshake). Coincidentally, I realised that I was infact dreaming. As soon as I did, I managed to rationalise the pain away. You know what, dreaming is so much more fun when you know you are dreaming. The annoying thing is that as soon as you know that you are dreaming, one of two things can happen: either, your brain sabotages you and you wake up, or your state of mind lets you forget very easily that you are dreaming. Plasmic Physics (talk) 08:02, 13 June 2011 (UTC)


 * Rarely, I am able to maintain a rational state of mind to allow me to create my own dream. Plasmic Physics (talk) 08:08, 13 June 2011 (UTC)


 * I have to say that pain in a dream rarely matches the type, or severity of the injury, it hasn't so far for me. Plasmic Physics (talk) 08:43, 13 June 2011 (UTC)
 * I don't know about others but I can occassionally feel pain in dreams. I once went to sleep with a headache, and was aware of the headache in my dream.  I then took some asprin in my dream and the headache went away.  And it stayed away until I woke up whereupone the headache returned.  This has also convinced me personally that the placebo effect is a real thing.  Googlemeister (talk) 17:27, 13 June 2011 (UTC)


 * Here is another example: I dreamt I was on fire, you'd think it was agonising, but it wasn't, it felt like a bad sun burn. This makes me think that pain in dreams are sourced from personal experience, you can't feel a pain in a dream that you havn't experienced before in the real world. i.e. if you've never had a broken arm, you can't experience the pain of a broken arm, your brain just gives you the next closest pain that you have experienced.


 * Memory plays a central role in pain synthesis in dreams. I would really like to have a citation for 82.43.90.27's refutal. Plasmic Physics (talk) 23:23, 13 June 2011 (UTC)


 * I based my statement on an assertion in one of Alan Hobson's books, together with the fact that I myself don't recall ever experiencing pain in a dream. However, a check of the literature shows that the consensus view on this question has changed:  more recent studies such as  and this paper report that although pain in dreams is rare, it does occur. Looie496 (talk) 23:39, 13 June 2011 (UTC)


 * I can possible explain why I have the ability, I have Asperger's - I am not an ideal test subject. My brain opperates differently to those that do not have Asperger's. Plasmic Physics (talk) 00:18, 14 June 2011 (UTC)


 * Oh, it actually was scientific consensus at some point that people didn't feel pain in dreams? I remember reading it in a pop-sci book as a young child, and discussing it with my older sister because we had both felt pain in our dreams: not awful pain, but pain. We briefly considered that maybe we simply dreamt that we had felt pain, without actually feeling pain, but (given that on one occasion she had been awoken by the shock of the pain) this seemed unlikely, and we decided that once we started defining pain as something other than 'a painful sensation', we were headed for trouble. So we assumed the book was simply wrong, as so many children's factbooks are. I'm not sure if I'm reassured or disturbed that this was actually an accepted theory quite recently: did nobody carry out even a broad survey? It's like the 'tongue maps' all over again. 86.164.30.215 (talk) 21:48, 14 June 2011 (UTC)

Fat
Why can body make fat easy from cabohyrat but you can eat lot of fat but no get fat? — Preceding unsigned comment added by 92.25.100.10 (talk) 20:49, 12 June 2011 (UTC)
 * That's not true. You get fat if you eat more calories than you burn in exercise, whether those calories come from carbohydrates or from fat. The moral is: eat, but don't eat too much. Simple, but not always simple to follow.Itsmejudith (talk) 21:26, 12 June 2011 (UTC)


 * (ec) Because the body also uses fat as a source of energy. (See Citric acid cycle for extensive details. Well, it's a bit complicated on the biochemistry level.) Fat is only synthesized from carbohydrates because fat has a higher energy density and thus can be stored more easily. 5BYv8cUJ (talk) 21:36, 12 June 2011 (UTC)