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January 13

Is there something like a reactivity series for melting points of organic compound types?

So at least the more important kinds are ranked like organic acids, normal 2-ketones, n-alkanes, n-alkenes, n-alkynes, n-alcohols, n-aldehydes, n-perfluoroalkanes, maybe n-cycloalkanes and so on? Then pick whatever number you want like butyl or dodeca- and all the melting points will be ordered? And one for boiling points if it's different?

If this isn't possible then is there a graph with dots or lines for the n-alkanes, n-alkynes and so on? Sagittarian Milky Way (talk) 00:14, 13 January 2017 (UTC)

What you want is a specialized application of the Unified Physicochemical Property Estimation Relationships (UPPER) model developed at the University of Arizona College of Pharmacy. It's described in detail by its developers Bo Lian and Samuel Yalkowsky in the document Unified Physicochemical Property Estimation Relationships (UPPER) (which, uncharacteristically for an Elsevier title, is available outside a pay wall). Figure 4 on Page 2714 is the graph "Calculated versus experimental total entropy of melting ( ): Walden’s rule; ( ): line of identity; N = 352."

Akash Jain, also of the University of Arizona College of Pharmacy, created a more detailed document "ESTIMATION OF MELTING POINTS OF ORGANIC COMPOUNDS" as his PhD dissertation. Luckily for you, that's free, too, courtesy of the University of Arizona College of Pharmacy. Most of the information you're looking for is tabular, not graphic, in Jain. The graphs in the document are almost all the observed vs. predicted melting points for organics.

I hope this helps. It's probably not the cut-and-dry thing you were asking for, you'll have to scan or key the tabular values in to get any graphs not provided by the authors. Increasing knowledge is increasingly expensive. loupgarous (talk) 02:10, 13 January 2017 (UTC)

(edit conflict) Comme ci? --Jayron32 02:12, 13 January 2017 (UTC)

Comme ça. Sagittarian Milky Way (talk) 18:12, 13 January 2017 (UTC)

What are the borders of the cerebral circulation?

When talking about the pulmonary circulation then its borders are very clear, since that it starts in the heart (to be accurate in the beginning of pulmonary artery in the heart) and ends in the beginning of pulmonary vein in the heart. But when talking about cerebral circulation it's not clear to me what are the borders of the vascular. I found on Google that it's "starts from the muscular carotid and vertebral arteries, which bring oxygenated blood the brain, and ends with jugular veins", but I don't know if it's reliable or not. In addition according the article here (cerebral circulation) there are two circulations, that actually makes it "cerebral circulations", anterior and posterior. 93.126.88.30 (talk) 03:48, 13 January 2017 (UTC)

There's also the Circle of Willis which consists of communicating arteries which can shunt blood flow between the posterior and anterior circulation and the blood vessels supplying each side of the brain. This tends to prevent ischemia of an area of the brain to which direct flow of blood is blocked; blood can flow through the communicating arteries of the Circle of Willis from patent arteries in some cases to perfuse areas of the brain to which direct arterial blood flow's been interrupted. This doesn't happen in all cases. loupgarous (talk) 21:44, 13 January 2017 (UTC)

The border of any vascular territory, including those in the brain, are the boundaries of the watershed area. So, each of the arteries (such as the middle cerebral artery) will have a moderately-well-defined area that it usually supplies. Knowing this is relevant for physicians when assessing patients with strokes. For example, by identifying the area on a CT scan in which the brain is affected by a stroke, the location of the vascular problem (usually an embolus) can be identified. Klbrain (talk) 01:18, 17 January 2017 (UTC)

How could air embolism in the artery (by syringe) cause heart attack or stroke?

1) I've been reading very well the article here on "air embolism" , and it's not clear to me how can a bubble that inserted by syringe to the artery of the arm, reach to the heart or the brain and damage them. the blood flow is just in opposite direction (from the heart to the tissue in case of artery). 2) In addition, why the bubble (air) is not dissolved in the blood? 3) Those bubble that we are talking about in the context of air embolism they are with the composition of the air outside? (78.09% nitrogen, 20.95% oxygen, 0.93% argon, 0.04% carbon dioxide, and small amounts of other gases) 4) The article here states: "Gas embolism into an artery is a more serious matter than in a vein, because a gas bubble in an artery may directly stop blood flow to an area fed by the artery.", I don't understand the statement that support in the claim that the Artery gas embolism is more serious than in vein, because we can say that the same thing can happen with bubble in veins that the bubble can stop the blood floe to an area that drown by the vein, such in case of DVT. 5) It's written also that in case of vein embolise in the most of the cases it's stopped in the lung. what does it mean "stopped"? does it mean that it goes out by diffusion or it's stuck there? 93.126.88.30 (talk) 05:15, 13 January 2017 (UTC)

Same way that an air lock in a fluid line happens -- the bubble reaches a local high point and gets stuck there (because air is lighter than blood), and interrupts the blood flow. 2601:646:8E01:7E0B:F88D:DE34:7772:8E5B (talk) 06:26, 13 January 2017 (UTC)

From the hand to the heart or brain? In addition, unlike a fluid line, the artery has a pressured flow toward the opposite direction, as noted. 93.126.88.30 (talk) 06:59, 13 January 2017 (UTC)

Your car's gasoline line is also pressurized, but that doesn't mean an air bubble can't cut off the fuel flow to the engine if the conditions are right! 2601:646:8E01:7E0B:F88D:DE34:7772:8E5B (talk) 07:13, 13 January 2017 (UTC)

The article on that is air lock, and it explains that "circulating pumps usually do not generate enough pressure to overcome air locks". Now normal systolic blood pressure is about 120 mm Hg, which means it's enough to raise a column of mercury 120 mm. Now compared to blood, mercury is about 12.8 times as dense, so that pressure would lift blood by more than 1.5 meters—which makes sense in view of where the blood has to go to circulate. That sounds to me as though it should overcome an air lock all right—but of course that pressure won't apply everywhere in the body. There must be places where the pressure is lower and which are therefore more vulnerable. --69.159.60.210 (talk) 09:31, 13 January 2017 (UTC)

The reason why air bubles in the fuel line of a car can stop fuel flow is NOT because the pump cannot develop enough pressure to overcome it. The pressure is what it is. It is because when the air bubble reaches the pump, the pump is sucking against air and not fluid. Fluid is not compressible or expandable, but air is. As most car fuel pumps are reciprocating, the inlet valve closes at the end of each pump stroke before the expanding bubble clears the valve. I too have noticed nurses getting air bubbles out of syringes, and thought I knew why. But then my wife had a lot of chemo delivered by IV into a vein, and the nurses pretty much ignore air bubbles, unless they stop the IV pump pumping, in the same way as air can stop a car fuel pump pumping! The quick-connect plumbing they use for chemo pretty much guarantees a few air bubles each time. 121.221.103.89 (talk) —Preceding undated comment added 09:59, 13 January 2017 (UTC)

• Then the air lock article needs to talk about air bubbles reaching pumps. It doesn't now. --69.159.60.210 (talk) 00:06, 14 January 2017 (UTC)

And since the heart is also a reciprocating pump, if you get a big enough air bubble inside it, you'll stop the heart as well by the same mechanism! 2601:646:8E01:7E0B:F88D:DE34:7772:8E5B (talk) 13:26, 13 January 2017 (UTC)

True, but the size of the air bubble big enough to stop heart pumping would have to be the ENTIRE volume of a LARGE syringe, even allowing for expansion at the heart intake pressure. The millimeter size bubles you get in syringes and IV tubing is at least 2 orders of magnitude below that. Also the heart is a 2-stage pump. It is inconceivable that one air bubble could stop pumping in both sides. 121.221.103.89 (talk) 15:51, 13 January 2017 (UTC)

I lost it through the reach discussion. I still don't understand how it can arrive from the arm artery to the heart or brain against the flow. What did I missed? (In addition the articles that were mentioned here are talking about insertion of bubble very close to the ares of the heart or the brain) 93.126.88.30 (talk) 18:37, 13 January 2017 (UTC)

Neither can I. If air is injected into an arm artery, it would have to travel the round trip, into arm tissue capaillaries, then to veins, back to the heart, and from there to the lungs, back to the heart, and then to the brain. I googled <arterial gas embolism> and <arterial air embolism> All articles returned nominate rapid ascent diving or certain types of major surgery as causing the problem. In teh case of diving, gas bubbles form throughout the body and can amalgamate into larger bubbles. None of the articles I scanned mentioned syringe injections as a possible cause - though that might be because all syringe users are taught to exclude air and generally do so. 121.221.103.89 (talk) 05:41, 14 January 2017 (UTC)

Sleep-wake in DSM

The DSM is a "Diagnostic and Statistical Manual of Mental Disorders" (my emphasis).

It includes a great deal on sleep-wake disorders. Why? I assume that it's because of much overlap, but I can't find anywhere that it actually explains why they are included. Certainly (I hope!) they aren't claiming that all sleep disorders are psychiatric disorders? Yet I know that some people insist that since they are in a manual with that name, that means that all sleep disorders are mental illnesses. I note that the ICD prefaces each sleep condition with "non-organic"; DSM doesn't.

I've looked for a good, reliable explanation. Can you find one?

Thanks, --Hordaland (talk) 05:16, 13 January 2017 (UTC)

The purpose of the DSM is to provide a clearly-defined technical language for professionals (especially psychiatric medical doctors). This enables consistent diagnosis and description.

The DSM, by itself, doesn't provide an explanation or causal link for the various conditions.

Nor does it preclude a causal link to some other condition; nor does it preclude comorbidity with other medical conditions.

So - to answer your question - the DSM contains a large chapter on sleep disorders because providing a consistent nomenclature and a formal technical language to describe such disorders is useful to the audience of professionals and researchers who normally use the DSM. The inclusion of the section on sleep disorders does not imply that every sleep disorder is a mental health issue. It simply provides a clear and consistent technical language, commonly used by mental health professionals, that can describe certain sleep disorders.

There is probably no better reference to cite than the DSM itself: in the introduction to the section on sleep/wake disorders, it says: "this chapter is designed to facilitate differential diagnosis of sleep-wake complaints and to clarify when referral to a sleep specialist is appropriate for further assessment and treatment planning." A sleep complaint certainly need not be a mental illness, even if a person seeks medical help for it!

Nimur (talk) 05:59, 13 January 2017 (UTC)

Thank you, @Nimur:. Interesting and very sensible. Do you consider all the sleep-wake conditions described in the DSM as "mental" disorders or illnesses? I don't have access to the DSM; I wonder if it specifically states why sleep is included and points out that the conditions described aren't (necessarily) psychological, though they may have psychological consequences for some people. I've read several dictionary definitions of the word "mental" -- no help there.

(I do have a sleep-wake disorder. It's disturbing to be told that it's a mental disorder.) --Hordaland (talk) 06:38, 13 January 2017 (UTC)

I think there is a false assumption here, that DSM is only supposed to cover "mental" or "psychological" disorders. The reality is that the main function of the DSM is to provide a consistent set of labels for all the conditions that psychiatrists may be called on to treat. Even though sleep disorders are not considered psychological disorders per se, they are often co-morbid with psychological disorders. In particular the majority of people with serious depression also suffer from sleep disorders. Looie496 (talk) 13:53, 13 January 2017 (UTC)

I think two or three points ought to be made. Most importantly - we don't and won't try to tell the OP what their condition is - that would be providing a diagnosis, and we just don't do that on Wikipedia's science reference desk. We don't know what your condition is; we aren't going to try to diagnose it; we're just here to help readers find good, high-quality scientific references.

The OP has also expressed concern that some might call a sleep problem a "mental disorder." Would it help if we called it a "wakalixes disorder"? The name of the condition has no impact on how severe the condition is, nor on whether the OP needs professional help to solve it. The more important word in this case is "disorder" - which specifically means that something is not right. You can have any kind of sleep condition, but if you have a sleep disorder, it means that the condition is causing some kind of trouble. A professional can help you to find a probable cause and a suitable fix - and depending on your specific case, the cause might be something totally unrelated to your mental state.

Finally: whether or not anybody is formally diagnosed with a mental health disorder: there is no good reason to stigmatize "mental" health. Mental health issues are commonplace and many professionals and other support services are available to help people become well. Scientific research, like this 2007 study by the CDC, shows that we have a great need to help educate the public "about how to support persons with mental illness and the need to reduce barriers for those seeking or receiving treatment for mental illness." So: whatever comes of your investigations into your own sleep condition, maybe you can step away with a slightly enlightened view of mental health!

Nimur (talk) 15:14, 13 January 2017 (UTC)

Men ought to know that from nothing else but the brain come joys, delights, laughter and sports, and sorrows, griefs, despondency, and lamentations. ... And by the same organ we become mad and delirious, and fears and terrors assail us, some by night, and some by day, and dreams and untimely wanderings, and cares that are not suitable, and ignorance of present circumstances, desuetude, and unskillfulness. All these things we endure from the brain, when it is not healthy...

Hippocrates, On the Sacred Disease

References

Sleep is pretty emphatically a "brain thing", so it seems fairly logical to me. I can see why you might not consider something like encephalitis a mental disorder, as it's usually from an exogenous cause, but sleep is a behavior that arises from the brain. And from a purely practical angle, sleep disorders have a high rate of comorbidity with things like depression, so it makes sense to integrate them into the DSM. (I have Asperger's syndrome, major depressive disorder, and sleep apnea! Isn't life fun sometimes?) --47.138.163.230 (talk) 07:22, 13 January 2017 (UTC)

I agree with these comments. Excessive sleep, or lack of sleep, is associated as a symptom of many mental/mind/brain disorders. The reliable sources refer to hypersomnia and hypersomnolence disorder, as a mind, or mental disorder, not just the DSM-5! Hordaland, just because you said "I do have a sleep-wake disorder. It's disturbing to be told that it's a mental disorder" in your earlier comments, seems to be your personal opinion, and you not wanting the reliable sources to be calling it a mental disorder.Charlotte135 (talk) 14:28, 13 January 2017 (UTC)

It appears that the consensus is that mental disorder should be the term used, instead of condition.Charlotte135 (talk) 05:19, 15 January 2017 (UTC)

Away a couple of days, and comments pile in! Thanks. I especially appreciate Looie496's sensible one; well put, "Looie"! That the DSM is only supposed to cover "mental" or "psychological" disorders is indeed a false assumption, and sleep disorders are not considered psychological disorders per se.

While Charlotte135 correctly states that some sleep issues are symptoms of mental disorders, it does not follow that all sleep disorders are symptoms of mental disorders. I believe that even the DSM is clear on that. Referring to "the reliable sources" is meaningless without citing them. No disorders are mental disorders unless reliable sources say they are.

Since I mentioned it, my own sleep disorder was correctly diagnosed years ago. While it did lead me to getting active as a wikipedian in the first place, let me clarify that it was not the background for my question here.

--Hordaland (talk) 18:55, 16 January 2017 (UTC)

I think that most comments here have concluded that the term mental disorder is most appropriate Hordaland. Disorder or condition is not specific enough, and not helpful.Charlotte135 (talk)

I disagree. Anyone wanting to continue the discussion is welcome to do so at the Talk page at Hypersomnia. There is IMO no point in using up more space here. --Hordaland (talk) 00:59, 17 January 2017 (UTC)

life expectancy of guns in terms of EFC?

hi. can anyone help me know how to aseratin the life ascertation of guns in terms of EFC? — Preceding unsigned comment added by Dexterkhan (talk • contribs) 10:39, 13 January 2017 (UTC) — Preceding unsigned

Moved to new section - comment added by Wymspen (talk • contribs)

Maybe this will be obvious to someone more familiar with guns but what do you mean by EFC? Effective full charge? Expected Family Contribution (although I don't get how this relates to your question)? Something else? Nil Einne (talk) 12:48, 13 January 2017 (UTC)

It is noted at the link Nil Eine provided that the actual decision to retire any specific gun barrel would be made on examination and measurement of actual wear rather than that predicted by the EFC count. Blooteuth (talk) 13:45, 13 January 2017 (UTC)

What's a life ascertation? —Tamfang (talk) 09:10, 15 January 2017 (UTC)

Stopping power

How does the stopping power of a bullet (at equal distance, like say 25 yards) correlate with its (1) diameter, (2) muzzle velocity, (3) muzzle energy, (4) momentum, (5) propellant charge, and (6) ballistic coefficient? Which of these parameters correlates most closely with stopping power? Also, how do the following cartridges rank in stopping power (highest to lowest or lowest to highest, your choice): 5.56X45 NATO, 223 Remington, 22 Long Rifle, 7.62X39 Soviet, 7.62X51 NATO, 308 Winchester, 7.65X21 Parabellum, 9X19 Parabellum, 38 Special, 357 Magnum, 44 Magnum, 45 ACP and 45 Colt? 2601:646:8E01:7E0B:F88D:DE34:7772:8E5B (talk) 13:49, 13 January 2017 (UTC)

Please do your own homework.

Welcome to the Wikipedia Reference Desk. Your question appears to be a homework question. I apologize if this is a misinterpretation, but it is our aim here not to do people's homework for them, but to merely aid them in doing it themselves. Letting someone else do your homework does not help you learn nearly as much as doing it yourself. Please attempt to solve the problem or answer the question yourself first. If you need help with a specific part of your homework, feel free to tell us where you are stuck and ask for help. If you need help grasping the concept of a problem, by all means let us know.. --Jayron32 14:03, 13 January 2017 (UTC)

There's controversy on this point. Until the 1960s, the Hatcher Relative Stopping Power formula was considered to be definitive in estimating the stopping power of ammunition (your question refers to the "stopping power of a bullet", when properly you should have referred to the "stopping power of a cartridge", because the bullet has no stopping power without a charge of propellant behind it and a barrel around it to spin the bullet and contain the expanding gases of the propellant - cartridge cases usually also figure into this, and the history of caseless ammunition indicates that cartridge cases are necessary for the best performance of a given combination of bullet, propellant charge and barrel).

From the 1940s to the 1970s various writers in the firearms press and consultants to the Federal government began examining the Hatcher Relative Stopping Power formula critically. The December 28th, 2012 post to the blog "Firearms History, Technology & Development" describes the history and specifics of estimating relative stopping power since Hatcher's RSP formula. loupgarous (talk) 20:58, 13 January 2017 (UTC)

The article Stopping power cited by the OP explains how many other factors than the bullet alone affect stopping power. Blooteuth (talk) 21:42, 13 January 2017 (UTC)

But the OP didn't appear to have internalized that knowledge. Now the OP can read the materials I pointed out as well as our article Stopping power and answer the original question knowledgeably. loupgarous (talk) 21:48, 13 January 2017 (UTC)

Yeah, I forgot to specify bullet shape and material -- in this case, assume the bullet is a non-expanding, full metal jacket ball type as used by the military. 2601:646:8E01:7E0B:F88D:DE34:7772:8E5B (talk) 01:29, 14 January 2017 (UTC)

I've just read the post about Hatcher's formula -- it says that the most important parameters are momentum and bullet cross-section (i.e. diameter), plus the type of bullet (full-metal jacket, hollow-point, etc.) Thanks! 2601:646:8E01:7E0B:F88D:DE34:7772:8E5B (talk) 02:42, 14 January 2017 (UTC)

I'd like to know what type of course the original question might be a homework question in. I know I can't think of one. --69.159.60.210 (talk) 00:08, 14 January 2017 (UTC)

Military schools offer coursework in the study of ordnance. West Point has had such coursework for most of its existence. loupgarous (talk) 22:34, 16 January 2017 (UTC)

Well, I'm not in a military school (and, in fact, I think West Point might not yet have resumed classes after the Christmas break) -- so it's not homework, but a pet project of mine (which, however, is not likely to be done in the near future). Specifically, if you want to know more, I've recently come up with an idea for a spy-themed FPS game, and I want this info so I can figure out how much damage the various weapons in the game should deal to enemies. (And this means that had Hatcher's formula been correct, it would have been a great way to calculate this -- the number it gives is claimed to have a 1-to-1 correlation with the probability of stopping the enemy with 1 shot, so I could just replace "probability of stopping an enemy with 1 shot" with "damage dealt to an enemy without body armor with 1 hit to the torso area" and it wouldn't be too far off the mark. But unfortunately, if what you said is correct, Hathcher's formula is off by a factor of 30-40 and cannot be used even as a first approximation.) 2601:646:8E01:7E0B:F88D:DE34:7772:8E5B (talk) 03:43, 17 January 2017 (UTC)

Honey bee behavior and oatmeal?

I noticed something strange today when I went to toss some scraps onto the compost pile. There was a huge congregation of bees rolling about in a mound of quick oats (which I had mistakenly bought, thinking they were the old-fashioned style that I happen to like). I couldn't find any references to this sort of behaviour and would like to know if this has been observed before. Also, any theories as to why they do that sort of thing? I did take a video of them, but haven't yet figured out how to upload it. If and when I do I will post a link here. Thanks! Earl of Arundel (talk) 22:14, 13 January 2017 (UTC)

It is possible you saw a mass of drones around a queen when she was on a mating flight, or whilst she was trying to start up a new colony. See here[1] DrChrissy ^(talk) 23:25, 13 January 2017 (UTC)

Perhaps, but it almost seemed like they were eating the stuff. But also sort of wallowing around and such. Very peculiar. I'm going to check the pile periodically over the next few days to see if they keep at it. Earl of Arundel (talk) 00:01, 14 January 2017 (UTC)

To bee or not to bee, that is the question here. There are a lot of flying insects that look like bees, especially in the southern states. So would like to see the video or some stills first for identification. Problem is that even quick-oats (that have been steam treated) are mostly starch which is toxic to bees as far as I know. So would be surprised if they are indeed honey bees ... unless Monsanto have genetically created some sort of kamikaze breed. Use a still digital camera. Images from them are easier to upload and upload them to Wikimedia Commons. If you do not own a macro-lens see if you can borrow one as you will get a better photo. --Aspro (talk) 23:44, 13 January 2017 (UTC)

No, these were most certainly bees, now whether or not they were the honey-producing sort I can't say for sure. But yes, I will post a link to a photo or video here later (if I ever manage to get that bit worked out, that is!).Earl of Arundel (talk) 00:01, 14 January 2017 (UTC)

It is actually quite easy to upload files to the Commons[[2]]. Keeping an eye on the area for the next few days will be interesting. When drones have mated, they usually die. So, you might find a few bodies of those that have not flown away. However, if the oats are toxic, as suggested above, any bodies you find may be due to this. DrChrissy ^(talk) 00:38, 14 January 2017 (UTC)

Interesting, well I'll keep that in mind then. And yes, I agree, monitoring them over a longer period may be the key to solving this puzzle. Thanks for the tips! Earl of Arundel (talk) 02:54, 14 January 2017 (UTC)

Maybe something beneath the oatmeal in the compost pile was attracting them, or maybe something else in the compost pile was interacting with the oatmeal, creating some new substance that was of interest to the bees. Bus stop (talk) 00:51, 14 January 2017 (UTC)

I was wondering that too, at first. But on closer inspection, neither of those scenarios seems very likely. For one thing, if there is something underneath attracting them then they are definitely confused because they are clearly focusing on the oat granules. Second, the oats were tossed out just yesterday so not really enough time (especially considering the cool weather) for much chance of a reaction to take place to create some sort of hybrid substance. That said, I wouldn't rule it out completely. I think I'm going to try an experiment with the oats by themselves in a mound on top of the grass some meters away to determine if they are without doubt attracted to the oatmeal. Earl of Arundel (talk) 02:50, 14 January 2017 (UTC)

I have a theory: I believe bees infested with mites, and in particular Varroa destructor, will roll around in any powdery substance they can find, as it apparently irritates the mites and drives them to leave. The quick oats must qualify. StuRat (talk) 00:58, 14 January 2017 (UTC)

You might be on to something there. Reviewing all of the footage now there is definitely an unusual degree of franticity in the nature of their movements. I'm no expert, but I have done quite a bit of "arm-chair" bee observation over the years and never have seen anything quite like this. It doesn't appear that they're frolicking in the stuff so much as, well, sort of rubbing themselves against it and whatnot in a visibly agitated fashion. So yes I think your theory sounds quite plausible, actually. Earl of Arundel (talk) 02:35, 14 January 2017 (UTC)

Just a quick question: were the quick oats plain? I've seen various flavoured or sweetened versions (not unlike instant oatmeal). If there was sugar on the oats, the bees might be after that. Matt Deres (talk) 14:40, 14 January 2017 (UTC)

For consideration:  bees are particularly attracted to grasses (e.g. oats) [3] --or at least the pollen, but who knows ... oatmeal itself is quite odorous . --2606:A000:4C0C:E200:C03A:9D20:31EF:82F7 (talk) 23:43, 14 January 2017 (UTC)

Before we head off to speculation land, let's remember not to anthropomorphise here. Just because humans find oatmeal odiferous does not mean that bees do. DrChrissy ^(talk) 00:18, 15 January 2017 (UTC)

I intentionally chose odorous (having a distinctive odor) instead of odiferous (smelly).  ;) --2606:A000:4C0C:E200:C03A:9D20:31EF:82F7 (talk) 00:58, 15 January 2017 (UTC)

There's two issues there. The first does not depend on species, and that's how volatile the components are. No species, for example, will find that glass has a strong odor. The second issue, which is species-dependent, is whether that species has scent receptors for the volatile compounds in question. StuRat (talk) 01:00, 15 January 2017 (UTC)

That's the point: bees that are attracted to grasses are likely "receptive" to oat VOCs. And since oatmeal is perceptively odorous, the information was proffered "for consideration". --2606:A000:4C0C:E200:C03A:9D20:31EF:82F7 (talk) 01:17, 15 January 2017 (UTC)

@StuRat. "No species, for example, will find that glass has a strong odor." That is a very strong statement to make on a science reference desk. What is your evidence for this? DrChrissy ^(talk) 22:49, 16 January 2017 (UTC)

Do you dispute that a substance must be volatile to be smelled, or that glass is not volatile at STP ? StuRat (talk) 02:07, 17 January 2017 (UTC)

@Earl of Arundel: - please bee careful if you decide to get that video! There are a lot of incidents with "killer bees" expanding widely into the U.S.; don't assume the swarm won't turn hostile. The suggestion you get it might just be the most dangerous suggestion ever posted on the Refdesk. That said, by all means, of course we'd love to have that video! ;) Wnt (talk) 18:24, 16 January 2017 (UTC)

January 14

Liver damage

Request for medical advice
The following discussion has been closed. Please do not modify it.
My mother has liver damage. She claims that the doctor told her to eat food as warm as possible (i.e. hot food, as temperature, not as taste). Is this sound science of quackery? Just to be sure: I am not asking for medical advice, I am asking if it is quackery. Tgeorgescu (talk) 01:43, 14 January 2017 (UTC) Responses deleted. This question is asking for medical advice and we cannot answer it here. --69.159.60.210 (talk) 05:34, 14 January 2017 (UTC) She is addicted to chain letters about miracle cures, that would explain why she has bizarre ideas about medicine. She could believe that such ideas would be objectively true and present them as the advice of her own doctor. Tgeorgescu (talk) 05:36, 14 January 2017 (UTC) You asked editors here, most of whom have no medical training whatsoever, to pass judgement on the advice given by the physician of another individual, and indeed, by extension, on whether that physician is a quack. If you are not happy with your relative's choice of physician, convince her to seek a second opinion. Akld guy (talk) 05:38, 14 January 2017 (UTC) It's an idea which seems bizarre and for which I found zero scientific validation while searching Google and PubMed. So, it was natural to think of quackery. As I stated, it is what she claimed, not what I would know that the physician stated. Tgeorgescu (talk) 05:44, 14 January 2017 (UTC) It's quackery. ←Baseball Bugs What's up, Doc? carrots→ 07:09, 14 January 2017 (UTC) But we don't know in what context the doctor said what he said to the patient with liver damage, who is likely to have some number of physical complaints that may not all be due to the liver problem. Count Iblis (talk) 08:14, 14 January 2017 (UTC) Sorry, but we can't make recommendations regarding the treatment of individual persons. Please seek out a medical professional. Dragons flight (talk) 08:25, 14 January 2017 (UTC)

Stopping power, part 2

OK, I'm now calculating the stopping power of the different cartridges listed using Hatcher's formula (which, BTW, wasn't in the article) and the diameter and momentum values from the table of handgun and rifle cartridges, but I'm getting ridiculously low values -- for example, just over 1 for 9X19 Parabellum hollowpoint, when the BlogSpot article says it should be between 30 and 40. WTF? Is the formula wrong as given in the blog, or are all the momentum values in the table wrong, or am I doing something wrong? 2601:646:8E01:7E0B:F88D:DE34:7772:8E5B (talk) 04:11, 14 January 2017 (UTC)

Actually the 9x19mm Parabellum cartridge's battle record and similar anomalies between the actual performance of various hunting cartridges and the calculated performance according to Hatcher's Relative Stopping Power formula caused firearms writers and US Federal government researchers to take a second look at Hatcher's RSP formula. I would not rely on Hatcher's RSP formula to predict relative stopping power.

I gave you a link to the Blogspot article specifically because the author discusses the work of Martin Fackler and other researchers since Hatcher in estimating relative stopping power. You yourself spotted the same thing Fackler and others did, that highly energetic rounds like 9x19mm Parabellum have an RSP not predicted by the Hatcher formula. Go over that Blogspot article again and our article Stopping Power carefully, and the sources they cite (looking over our article Stopping Power I see several minor defisiencies but it also cites several good sources of information for you in its list of references). Look them up.

This project of yours is not going to be easy, nor should it be. Relative stopping power is even now a contentious issue in the police and military communities - the 5.56x45mm NATO cartridge, long thought when loaded with a boat-tail FMJ bullet to be adequately lethal for military use, has disappointed US ground forces in the Iraq and Afghanistan conflicts, to the extent that the M-14 infantry rifle chambered in 7.62x51mm NATO has been re-issued to Marine and other US forces in the field. Likewise, 10mm Norma, while it tended to destroy service firearms earlier than other commonly used rounds, is enjoying a resurgence of popularity because more durable pistols are now available to fire it, and its increased muzzle velocity gives it a decided advantage in terminal ballistic performance compared to (for example) the .40 Smith & Wesson cartridge (a 10mm cartridge with a shorter case, lower recoil, lower chamber pressure and lower terminal ballistic performance than the 10mm Norma). These are just two instances of ongoing controversy regarding actual relative stopping power versus predicted relative stopping power.

See if you can find tables based on Fackler's work (start by looking up the references cited in our article on Martin Fackler. They may not be absolutely definitive in predicting relative stopping power, but they're bound to be more plausible predictors than Hatcher's RSP formula for modern handgun rounds. I'm not allowed (or inclined) to do this for you, but you seem able to do this yourself. loupgarous (talk) 23:13, 16 January 2017 (UTC)

So are you saying that Hatcher's formula is off by a factor of 30-40? Because I'm getting these ridiculously low values for all of the calibers listed, not just some of them. 2601:646:8E01:7E0B:F88D:DE34:7772:8E5B (talk) 03:32, 17 January 2017 (UTC)

What is string?

Hi, I'm working on the article string (cord).

I'm having a hard time finding sources about string on the Web, and was hoping to avoid a trip to the library. To make the best article possible, I'm interested in everything about string. Including its definition, what classes of things it belongs to, its history (especially its origin), the various types of string, what it is made out of, how it is made or manufactured, uses of string, and so on.

Concerning classes and types, the thread article says that thread is a type of yarn, and some dictionary definitions say that string is made of threads twisted together. So, is string a type of yarn? Or are yarn and thread types of string?

Are string and yarn two different things? If so, what common type of thing are they?

What class of things do thread, yarn, twine, string, cord, and rope belong to?

What are the parent-subtopic relationships here? Which ones are parent topics of what, and which ones should be featured as subheadings of another?

String art, which uses thread, refers to the material used as string.

I'm pretty sure string predates both yarn and thread. See Oldest string found at French Neanderthal site and 30,000 Years Old Wild Flax Fibers - Testimony for FabricatingPrehistoric Linen.

I look forward to anything you can find on the topic of string.

Please provide references.

Thank you. The Transhumanist 10:19, 14 January 2017 (UTC)

This might help = http://wikidiff.com/string/cord Wymspen (talk) 10:51, 14 January 2017 (UTC)

• Cordage might be a useful term, as Big String's blanket term for both strings and ropes.

Conceptually, string goes back to the mesolithic. Fibres, of either plant or more probably animal sinew, were used to attach stone tools to wooden handles. This is supported by grooves in such stones (the string itself is long gone) which, along with better shaping of the stones, can be used to date them from the earlier and simpler hand-held stone tools.

Clothing also involved fibres to connect animal skins for clothing and luggage. We have evidence of this from Europe in the iron age peat bog bodies, or those from glaciers. Egypt is also worth looking at, for a very ancient civilisation with a highly developed textile industry and also good preservation of surviving relics.

In the dark ages(sic) period, much "string" was made by plaiting rather than the twisting we use today. String (today) is made by the twisting together of spun yarns, of long fibres. This needs both the invention of the ropewalk and also a long-fibre yarn with good tensile strength. Weaker yarns are more easily plaited together than twisted. Many fibres were used from the beginning and it was known that the better fibres could be used for stronger tasks, although they were harder to obtain. Wool makes a plentiful fibre that's useful for clothing, but this is too short, thus too weak, for string. It was often knitted, rather than woven, as this involves lower tensions and less demand on the fibre. Breeding of better sheep eventually produced a longer fleece which could be spun to a worsted yarn, strong enough for weaving or even string (worsted string still has a specialist use as oil wicks in the lubricators of steam engines). Plant fibres were bast fibres from beneath tree bark (especially in Eastern Europe) or thinner stem fibres from flax (making linen) or nettles. The Norse peoples in particular developed skilled plaiting and tablet weaving and much of their "string" for luggage or fastening straps was made from flat-woven braids, rather than round cordage. The Celts, particularly in Ireland, made great use of horses and needed strong cordage for harness and chariot fittings. Horses supplied this too, as either leather strips or as horsehair, the longest and strongest fibre available in the period, which was spun and used for cordage rather than weaving. Andy Dingley (talk) 11:34, 14 January 2017 (UTC)

You've provided some good ideas on what to look for. Thank you. The Transhumanist 09:03, 15 January 2017 (UTC)

(edit conflict):The word itself goes back thousands of years and was originally used for any thickness, but the OED says: "In modern use: a thin cord or stout thread.". For etymology, the OED has: "Old English stręng (masculine) = Middle Low German strenk, strenge, Middle Dutch strenghe, stringhe (modern Dutch streng, feminine), Old Norse streng-r (masculine) (Danish streng, Swedish sträng) < Germanic type *straŋgi-z; another declensional form is found in Middle Low German strank, strange (masculine), Old High German stranc (masculine) (Middle High German stranc, strange (masculine), feminine, modern German strang, masculine) < Germanic type *straŋgo-z, < *straŋg- < pre-Germanic *stroŋk-: *streŋk-. The pre-Germanic root *streŋk- appears not to be known in this form, but a parallel form *streŋg- is represented by Irish (and Scottish Gaelic) sreang cord, string, Middle Irish srincne navel-string, Greek στραγγάλη halter, Latin stringĕre to bind, draw tight. Connection with strong adj. is doubtful." (but you've probably seen this).
Just in case you don't have access to the OED, yarn is also a very old word. The OED has the etymology: "Old English gearn strong n. = West Frisian jern , North Frisian jaarn , juarn , Middle Dutch gaern , gar(e)n (Dutch garen ), Old High German, Middle High German, German garn yarn, †net, Old Norse (Swedish, Danish) garn (whence garn n.); apparently < the root represented also by *garnô in Old Norse gǫrn , plural garnar guts, and *garnjo- in Old English micgern , Old Saxon midgarni , Old High German mittigarni midgen n. (= entrail-fat, suet), and related (outside Germanic) to Lithuanian žárna intestine, Latin hariolus soothsayer, haruspex one who divined the future from an inspection of the entrails of victims, Greek χορδή intestine (chord n.1). (Compare, moreover, Sanskrit hirā vein, Latin hīra empty gut, hillae < *hirl- smaller intestines.)" and says: "Originally, spun fibre, as of cotton, silk, wool, flax; now, usually, fibre spun and prepared for use in weaving, knitting, the manufacture of sewing-thread, etc." and "In Rope-making, one of the threads of which a strand of rope is composed".
Thread is also very old with the OED definition: " A fine cord composed of the fibres or filaments of flax, cotton, wool, silk, etc. spun to a considerable length; spec. such a cord composed of two or more yarns, esp. of flax, twisted together; applied also to a similar product from glass, asbestos, a ductile metal, etc." and etymology: "Old English þrǽd = Old Low German *þrâd (Middle Dutch draet , Dutch draad ), Old High German, Middle High German drât (German draht ), Old Norse þráðr (Danish traad , Swedish tråd ) < Old Germanic *þræ̂-ðuz , pre-Germanic *trētús ; < *þræ̂- to twist". Sorry I can't find any useful references other than the dictionary. Dbfirs 11:44, 14 January 2017 (UTC)

This will definitely help build an etymology section for the article. Thanks. The Transhumanist 09:03, 15 January 2017 (UTC)

You many also want to include as section on how long a piece of string is. Hayttom (talk) 18:31, 14 January 2017 (UTC)

Usually about an inch shorter than you need it to be. Wymspen (talk) 21:53, 14 January 2017 (UTC)

"String is a / Very important thing / Rope is thicker / But string is quicker". (Spike Milligan) [4] Alansplodge (talk) 19:46, 14 January 2017 (UTC)

String is clearly almost certainly possibly made out of string (physics), nyuk nyuk. (Wish I had something more insightful to say...) Wnt (talk) 22:51, 14 January 2017 (UTC)

Is yarn a type of string?

Or is it the other way around? The Transhumanist 20:36, 15 January 2017 (UTC)

Is string a type of cord?

The article was renamed to string (cord), so we need to know the relationship between string and cord.

Is string a type of cord?

Or...

Can cord be made from string?

Or are string and cord siblings?

Is string a type of cordage, along with cord and rope?

The fate of the title hangs in the balance. :) The Transhumanist 22:51, 15 January 2017 (UTC)

What is cordage?

Cordage obviously includes cord and rope. But does it also include string?

(Need references). The Transhumanist 20:36, 15 January 2017 (UTC)

Cordage is usually taken to be the most general term for strings and ropes etc. Wire rope is cordage, twine and yarn are cordage. If it's made with a fiber or a wire, and much longer in one dimension than any other, we can call it cordage. See. e.g here [5] SemanticMantis (talk) 15:57, 16 January 2017 (UTC)

EU power cable mod

I ordered an induction stove from Germany to my country - Vietnam. In order to make it work, I had to mod the power connector from 3 pin to 2 pin (with 1 pin discarded) because the power socket in my country contains only 2 (see image here). Then we continued to order another one (namely Siemens HMI40PC). But this time, I am confused because it comes with a 4 pin power connector (see image here). Could somebody show me how to get it work? By the way, there is a small 2 pin connector of unknown purpose (see image here). I lost the English version of the manual, and it is hard for me to guess what that thing does. Livy (talk) 12:27, 14 January 2017 (UTC)

Maybe you could google the manual. I found this and this. I'm not sure it is what you want. Good luck. Anna Frodesiak (talk) 12:44, 14 January 2017 (UTC)

Okay, I was way off with those links, but think I am finding the right ones now. I am looking but someone may beat me to it and give a link first. Anna Frodesiak (talk) 12:46, 14 January 2017 (UTC)

How is this? Am I getting closer? Anna Frodesiak (talk) 12:49, 14 January 2017 (UTC)

Cutting off pins on a power cord is a great way to kill yourself from electrocution. The pin is probably a ground connector, so that if there's an electrical fault in the device the current shorts out and trips a fuse/breaker instead of going through you when you touch it. If you are not an electrician, do not attempt to modify electrical devices to "make them work". Consult a licensed electrician. (Maybe it's time we expand the Ref Desk prohibition on medical diagnoses and legal advice to include other "licensed" professions like electrician and plumber.) --47.138.163.230 (talk) 13:36, 14 January 2017 (UTC)

Agree. The three connectors are phase, neutral, and (protective) earth. The last one keeps all parts of the system that are not supposed to carry electricity at ground potential, so there is no difference of potential between the ground and the device. This protects you from becoming the grounding connector (i.e. electrocuting yourself). The four-connector stove is designed for the German market, where in addition to the normal 230V two-phase power supply, all dwellings are also supplied with 400V three-phase electric power that is in particular used to connect electrical stoves. The 4 connectors are two of the phases, neutral, and earth. It is possible that the device can be connected to 2-phase 230V systems (in particular if it's design also covers the rest of the EU), but you really need to get an expert to determine that and make it work. You won't be able to use full power of the stove with a two-phase connection. And you should certainly make sure that your devices are grounded properly. --Stephan Schulz (talk) 14:11, 14 January 2017 (UTC)

@Stephan Schulz: I was pretty sure that three-phase power had ... three phases. And that's what the article says. It also says there's one "neutral wire" in some of these distributions, which can form a single phase power supply with any of the three, so I take it that's about the equivalent of the white non-live but non-ground wire in an American two-prong outlet (give or take voltage). I certainly can't rule out you're right though from first principles ... if homes can receive one of the three phases only I suppose they could receive two plus neutral and ground. Wnt (talk) 22:59, 14 January 2017 (UTC)

Perhaps S.S. had imbibe too much schnapps when he posted that and was phased by all the phases ;¬) --Aspro (talk) 23:43, 14 January 2017 (UTC)

Hicks. But seriously, in Germany the normal 3-phase connector has 5 wires - L1, L2, L3 (the three phases), N (neutral) and PE (Protective Earth). For reasons best known to electricians, for a stove you use two of the phases (normally L1 and L3) and N to draw power. You use PE to not get killed. If you also connect an oven to the same socket, you use L2 and N (and PE). --Stephan Schulz (talk) 01:22, 15 January 2017 (UTC)

(ec) Yes, there is a safety issue when you discard the power wire because it almost certainly serves to ground the exposed metal parts of the stove. One appreciates that in Vietnam two-pin mains sockets that roughly conform to Type C "Europlug" are widespread but according to our information sockets like this that has a 3rd ground connection are available. I strongly advise you to have one installed by an electrician competent to make the Ground connection secure, for the future safety of all users of the oven.

The Siemens HMI40PC may require a 3-phase mains supply that you would need specially installed. The supplier, not Wikipedia, should answer this question which you can send to Siemens-info-line@bshg.com. Once again, consult a competent electrician. (S)he will also be able to confirm the purpose of the small 2-pin connector which is likely to supply power to a separate device such as a lamp or extractor fan. Blooteuth (talk) 14:14, 14 January 2017 (UTC)

• I don't believe that is a simple power plug. I think it is designed to plug into a special power supply or power converter device, not into any sort of wall socket. You really need to ask the manufacturer about this. Looie496 (talk) 17:49, 14 January 2017 (UTC)

• @Livy: Forget most of the advise above. The first power cord with 3 wires is the one you need. Remember that blue is neutral, brown is phase and the yellow/green is ground. If you don't connect the ground you'll be not safe if there is a short so you should find a way to connect it somehow. Find someone who knows what they're doing for that part. The 4-prong wire is to connect to an optional oven (see the label in your picture). So if you don't have an oven you won't need it. And it's NOT a 3-phase connection as was mentioned above. Why I know all this? Because I looked at the manual in the link you've provided. Cheers. 195.78.229.37 (talk) 01:33, 15 January 2017 (UTC)

The first image belongs to the old stovetop. And while I could be mistaken, the label in the second image tells you where to connect PE to the stovetop and optional oven. The yellow (and green, though it's hard to see) cable is PE (and if so should be connected to earth). The other 4 connected to the 4-pin plug (which I have never seen before) are most likely the 3 phases (grey, brown, black) and neutral (blue, connected to the slightly longer pin of the plug). At least that would be the correct colour coding, which I would expect from Siemens. And that would mean that this is indeed a 3-phase connector. --Stephan Schulz (talk) 08:17, 15 January 2017 (UTC)

Damn you, Schulz, you're right. Here is an image for the connections. They'll need to combine wires as shown in the third option labeled 220-240V 1N.--TMCk (talk) 14:37, 15 January 2017 (UTC)

Nay good Sir, if there be cause for damnation I beg you spare the innocent Stephan Schulz and do plead Mea culpa to the Original sin of triphasic correctitude. Blooteuth (talk) 15:11, 15 January 2017 (UTC)

I'd note that the specs seem to suggest the hob uses 7200W. I don't know whether this is different if you connect it in the one phase fashion, but there's still a fair chance it'll use more than whatever power sockets and possibly the cables connecting to them are able to support. In other words, emphasising what others have said above, you really need to get a qualified electrician to do the installation. Nil Einne (talk) 16:03, 15 January 2017 (UTC)

Agree that the OP must have this hob installed by a qualified sparky. Say the hob does indeed draw 7200 on full load. That is some 33 amps at 220 volts on single phase. In Germany and other mainland countries that instal 3 phase to modern homes, they like to keep each phase current to no more than 16 amps (hence the preference for 3 phase hobs). So a cable that can carry that amperage (33 amps), on single phase, needs to be a 'new' cable run from the distribution board. Also the sparky may discover that the board is already linked up to an earth spike to anchor the neutral line to earth as it enters the property. So the job of providing the PE (protective earth) to the hob becomes a very simple and inexpensive matter. Modern safety devices no longer need an earth to cut-out when there is an imbalance between lines but the reason that there are so few deaths to day is because of the belt and braces approach which include every good practice being adopted. On the up side however: You (or one of your family members) can only suffer death through electrocution once in a lifetime.--Aspro (talk) 16:05, 16 January 2017 (UTC)

Aside: Regarding the power plug in the image. My thoughts are: As these hob roll off the production line they need to be quality checked. It saves time (and avoids operator errors) if all conductors are not free but bonded together so the cable can just be plugged into the tester by the operator. Can not tell by the image provided but I guess that that the pin pitch corresponds also the the terminal block pitch in the kitchen junction box. After all, this is most likely the only 3 phase appliance one owns and one doesn't move them around from room to room. So there is little point in having a more expensive 3 phase plug and socket. So they are just permanently hard wired in to the electrics via a junction box. Once screwed into the terminal block, the electrician can add the links and so forth on the other side and thus avoid invalidating warranty. It is also simpler as he only has to remember the power side and is thus less likely to make a mistake. What we really need is an input from a sparky that does this for a living and is still alive to tell the tale. --Aspro (talk) 17:08, 16 January 2017 (UTC)

Why are the leaves still red? The sequel

Referring to this question, I thought I saw the plant yesterday but it was a different one. Although the red leaves are starting to curl up, everything is still red.— Vchimpanzee • talk • contributions • 16:10, 14 January 2017 (UTC)

Chlorophyll is a metabollically expensive pigment; it is sequestered by the plant while the leaves are alive, so it is not degraded by winter conditions, but is absorbed. Any pigments left in a dead leaf once it is dead (and has lost its vascular connection to the stem) is simply dead. It will decay according to ambient conditions, but not according to any purposeful action of the plant or set schedule. μηδείς (talk) 22:10, 14 January 2017 (UTC)

Are there units that take spacetime into account?

Like kilogram-seconds (mass times how long it's existed (now or all time including the future)), liter-seconds, meter-seconds, mile-years (Appian Way > Trans-Siberian Railroad) Sagittarian Milky Way (talk) 20:54, 14 January 2017 (UTC)

Might be difficult, since space-time is warped around massive objects, and subject to change as those masses change. So defining the space-time of a region would be a bit like defining the surface area of a balloon that's continuously expanding and contracting. StuRat (talk) 21:52, 14 January 2017 (UTC)

Mass-energy isn't really known for being created or destroyed, just moved around, so I don't get your definition. But Planck units might provide some ideas for making weird, creative conversions. (See nondimensionalization, though to this non-physicist this seems like it should be a tooth-clenching exercise in stripping meaning and dimensional analysis from any situation) Wnt (talk) 23:01, 14 January 2017 (UTC)

I mean a (probably useless) unit where an uncut diamond can be more time-massive (timassive?) than a billion tonne iceberg that has just broken off. The iceberg has to exist for about 1.6 minutes to accumulate enough gram-years to beat a 1 gram 3 billion year old diamond. Likewise in relative terms the Egyptian economy still clobbers the EU's in spacetime (The EU has had a quarter the world GDP for 23.1 years. Egypt only needs to average 1/800th the world GDP for the last 5,000 years to have more gross world product fraction-years. It has 1/200th world GDP even now) Sagittarian Milky Way (talk) 01:30, 15 January 2017 (UTC)

I don't think you're talking about space-time; you're just talking about time. You want to multiply some quantity by the length of time it exists. That has nothing (or not much) to do with the concept of spacetime. CodeTalker (talk) 01:59, 15 January 2017 (UTC)

Very well. See four-dimensionalism though. Sagittarian Milky Way (talk) 02:36, 15 January 2017 (UTC)

See Spacetime interval--213.205.192.126 (talk) 01:26, 15 January 2017 (UTC)

If this were the humanities desk I might direct you to Perdurantism and worm theory, but, from a Science viewpoint, you might also be interested in World line. Dbfirs 12:00, 15 January 2017 (UTC)

Accumulated loan Interest of the Simple kind in economics is $rBm$ where

r is the simple annual interest rate

B is the initial balance

m is the number of years elapsed. Blooteuth (talk) 14:51, 15 January 2017 (UTC)

Along those lines, future value may also be thought of as a quantification from economics that includes a time component. SemanticMantis (talk) 15:53, 16 January 2017 (UTC)

Nasal breathing and tonsils

I saw the next question on facebook group "Hypertrophy of one of the following can be a reson for difficulty nasal breathing. A. Tonsilla pharyngea B. Tonsilla palatina C. Tonsilla lingualis D. Tonsilla tubaria E. All above mentioned tonsils". The answer there is option a. no explanation and I suspect that's not the answer since it doesn't make sense to me according to the link to an article which I saw here on the article "tonsil" ("Obese children with SDB had larger palatine tonsils than did normal-weight children with SDB. This finding suggests that larger palatine tonsils may have a greater effect on upper airway obstruction in obese than in normal-weight children with SDB.). Then I suspect the answer is not Tonsilla pharyngea as it's written there. Is it right? 93.126.88.30 (talk) 21:50, 14 January 2017 (UTC)

I added a title. StuRat (talk) 21:52, 14 January 2017 (UTC)

I saw almost the same question also here (no.83) with same answer. 93.126.88.30 (talk) 02:57, 15 January 2017 (UTC)

January 15

Physical interest/meaning of a certain Bernstein function

A quick question: consider the Bernstein function f(x):=-ln(1-exp(-x)), for x>0. Is this function any interest, or has it any meaning in Mathematical Physics, or more generally in some area of Physics? --151.29.234.2 (talk) 11:17, 15 January 2017 (UTC)

As a Mathworld link notes, completely monotonic functions occur in elasticity where Hooke's law F = kX applies to the special case of small deformations that exhibit Linear elasticity, and in larger deformations that are non-linear functions of applied strain, but not after non-reversible yield occurs. Blooteuth (talk) 14:37, 15 January 2017 (UTC)

Feynman Lectures. Lecture 44. Ch.44-4 The efficiency of an ideal engine [6]

...

Now we shall see how this universal law could also be obtained by logical argument, without knowing the properties of any specific substances, as follows. Suppose that we have three engines and three temperatures, let us say T1, T2, and T3. Let one engine absorb heat Q1 from the temperature T1 and do a certain amount of work W13, and let it deliver heat Q3 to the temperature T3 (Fig. 44–8). Let another engine run backwards between T2 and T3. Suppose that we let the second engine be of such a size that it will absorb the same heat Q3, and deliver the heat Q2. We will have to put a certain amount of work, W32, into it—negative because the engine is running backwards. When the first machine goes through a cycle, it absorbs heat Q1 and delivers Q3 at the temperature T3; then the second machine takes the same heat Q3 out of the reservoir at the temperature T3 and delivers it into the reservoir at temperature T2. Therefore the net result of the two machines in tandem is to take the heat Q1 from T1, and deliver Q2 at T2. The two machines are thus equivalent to a third one, which absorbs Q1 at T1, does work W12, and delivers heat Q2 at T2, because W12#W13-W32, as one can immediately show from the first law, as follows:
W13−W32#(Q1−Q3)−(Q2−Q3)#Q1−Q2#W12.(44.8)
We can now obtain the laws which relate the efficiencies of the engines, because there clearly must be some kind of relationship between the efficiencies of engines running between the temperatures T1 and T3, and between T2 and T3, and between T1 and T2.

— Feynman • Leighton • Sands, The Feynman Lectures on Physics, Volume I

First, I don't understand why W₃₂ is negative and why is calculated as Q₂−Q₃ and not Q₃−Q₂.
Mathematics must be correct in all cases, even if we don't know is the work done on or by the machine 2.

Second. How to calculate efficiencies? I try next:
$\eta _{\text{machine 1}}={\tfrac {W_{13}}{Q_{1}}}$

$\eta _{\text{machine 2}}={\tfrac {W_{32}}{Q_{2}}}$

$\eta _{\text{machine 3}}={\tfrac {W_{12}}{Q_{1}}}$
$W_{12}=Q_{1}-Q_{2}$
$W_{13}=Q_{1}-Q_{3}$
$W_{32}=Q_{2}-Q_{3}$
$(W_{13}-W_{32}=W_{12})$
So we have 6 equations and 9 unknowns. The system is unsolvable. Username160611000000 (talk) 12:55, 15 January 2017 (UTC)

• we have 6 equations and 9 unknowns. The system is unsolvable. - I will just "answer" that part, because I think you can genuinely profit from it.

The ideal gas law states that $P=\rho R_{\text{specific}}T$. That is a "system" of one equation and three unknowns (pressure, density and temperature), hence unsolvable. So what? Tigraan^{Click here to contact me} 18:32, 16 January 2017 (UTC)

Tritium tube concentration and pressure for brightness

When tritium is put into one of those glowing glass tubes is it put in at 100% concentration or could it be concentrated to make them brighter? If the tube was made from a thicker or different material could it be put in at higher pressure in order to make the tube brighter? --78.148.97.148 (talk) 14:27, 15 January 2017 (UTC)

It's 100% concentration of hydrogen at a couple of atmospheres pressure. It's generally easier to make and fill vials at above atmospheric pressure than below. The brightness is controlled by the phosphor coating, the lifetime of the tube by the tritium fill. It's easy to make a new vial maximally drive the phosphor, but this gets harder as the tritium decays. Tritium's half life is 12 and a third years, Betalights are usually specified for a fifteen year lifetime and are usefully visible for maybe two halflives (thus a quarter of the original activity, possibly with degradation of the phosphor too). The brightness of the tube depends on the surface area, the activation power and the lifetime from the tube's volume. So the ratio between volume and area (i.e. tube radius or disc thickness) is important - a narrow tube may need a "powerful" fill. The "tritium" fill is never pure tritium as that's hard to arrange and of no real use - some will just be protium (vanilla hydrogen). If a tube is quite large but doesn't need to be especially powerful, then the gas pressure is usually kept the same, but there's a mixture with less tritium in it.

The radioactivity of the complete vial is usually limited by paperwork: most are kept to 1GBq, larger ones up to 10GBq are also used. Over 10GBq does need paperwork per device - so they're used, but discouraged, especially for civilian purposes. Andy Dingley (talk) 15:48, 15 January 2017 (UTC)

Agree with AD. The phosphor coating can only release a fixed amount of photon energy after being excited. So when the tritium concentration is higher enough to re-excite the phosphor atoms the moment they return to their rest state, no extra luminance is going to be forth coming. Therefore, the only option is to increase the surface area. Best way to do that is to use lots of very thin tubes as the ratio of surface area is greater for any given volume. Of course, if it were possible to get the pressure high enough and the gas hot enough it would get suddenly very bright indeed – at the same time as lowering the local real-estate values around where you live (or that should be in the past tense -lived). Aspro (talk) 18:52, 15 January 2017 (UTC)

The article Tritium illumination describes the construction of "beta lights" that consist of a glass tube with its inner surface coated with a phosphor and filled with Tritium a radioactive isotope of hydrogen. Having with a half-life of 12.32 years, tritium lights lose half their brightness in that period. The more tritium that is initially placed in the tube, the brighter it is to begin with, and the longer its useful life. Installing tritium at higher than atmospheric pressure can increase brightness and useful lifetime but at higher cost, require a thicker tube for strength, and possibly raise safety concerns since escaped tritium is a radioactive hazard. Blooteuth (talk) 19:50, 15 January 2017 (UTC)

"tritium lights lose half their brightness in that period."

But they don't. Nor are "lots of very thin tubes" a good or economical idea.

Tritium lighting is mostly used for self illumination. But a decade or two ago, before useful LED torches, when tritium was still sometimes used to make torches usable for map-reading, these were discs rather than tubes. The diameter of the disc controlled the brightness, the thickness controlled the life. Andy Dingley (talk) 23:45, 15 January 2017 (UTC)

Our article tritium illumination says that there are "several thousand" times more tritium in a nuclear weapon than in a keychain. I assume this is a slight underestimate... :) Some folks above sound like they are familiar with the topic - can someone put an actual sourced number for that difference in the article? Wnt (talk) 17:54, 16 January 2017 (UTC)

• Article should be renamed as Tritium luminance. As anybody whom did the 101 knows 'illuminance' is the light falling upon an object etcetera., not the light emitted by the source (which is the luminance). Heard it said, that the amount of hydrogen needed to boost a nuclear device is no more than that which would fill a child's party balloon ( at standard temperature and pressure) which if one considers, that volume is well over a thousand time more than a keyring light. The Hydrogen then gets confined in a 'small' titanium bulb within the core. Extra tritium can be provided by the transmutation of lithium, once fusion has started. Would love to build one but don't know of anyone with a big enough back-yard to test it in. Mind you... Kim Jong-un appears to have a similar amateurish interest and has a very large range of unpopulated land. Does anybody have his email address? Lastly. A disc is very inefficient as approx half the energy is lost on the obverse face.--Aspro (talk) 21:34, 16 January 2017 (UTC)

Tritium radioluminescence might be justified as a redirect, but as many tritium illuminators are used for illumination of signage as are used for luminescence. They were originally developed as dial illuminators and the name stuck. Also we're under COMMONNAME, not just waving around personal erudition.

As to nuclear weapons, tritium and lithium, then you're confusing the two (boosting vs. secondaries).

If discs aren't used for Betalights, then you might like to inform Betalight themselves [7]. When used one sided, they're usually painted white on the back face. Andy Dingley (talk) 21:54, 16 January 2017 (UTC)

Where did I say they were not used. Talked about efficiency. Tritium radioluminescence seem very acceptable though. As for COMMONNAME, there are some nomenclatures that as an encyclopedia we should get right.  ! Otherwise 'we' would be contributing to positive feed-back (think audio howl). Said that "Extra tritium can be provided by the transmutation of lithium" so of course it is secondary so don't see why you think I'm confused by any of what I said.--Aspro (talk) 23:34, 16 January 2017 (UTC)

I looked up hydrogen bomb and was amazed to read that the fusion fuel is actually lithium deuteride, not tritium at all! It didn't give a quantity - a non-reliable source [8] estimates up to 10,000 kg in the largest fusion bomb but I doubt they had their math right. I don't think it's a party balloon but honestly I should admit I don't know. It seems like every time I look up nukes they seem to operate a completely different way... I get the feeling that there's been a lot of misinformation spread around. Wnt (talk) 21:58, 16 January 2017 (UTC)

Having said that. Beta touches are almost exclusively used by the US military and as the US tax payer picks up the bill there is really no need to consider efficiency nor cost. If Walmart started selling them however, the design and construction may very well change. --Aspro (talk) 21:48, 16 January 2017 (UTC)

They're hardly used by the US military. The UK have always been bigger users. Also I can't speak for Walmart, but plenty of outdoor dealers carry small ones, and used to carry the larger torches (obsoleted by LEDs). [9] Saunders-Roe sell them mail-order too - the shipping boxes are great for terrifying the postman. Andy Dingley (talk) 21:56, 16 January 2017 (UTC)

That link appears to go to a Swiss company (you know, those folks that invented the cuckoo clock) and they don't seem to declare their NATO reg. May say MOD Patt. But that can just be sales and marketing puffery. Other companies proudly show their NATO. As far as I'm aware the British Army still relies on a good old box of Swan Vesta. Failing that, they just rub two boy scouts together [10] ;¬) .--Aspro (talk) 22:55, 16 January 2017 (UTC)

NSN 6260-99-965-3582 Andy Dingley (talk) 23:26, 16 January 2017 (UTC)

Helicopters and drones on Everest

There are apparently a lot of touching movies about lunatics who follow the siren song of Everest and K2, and the hardships they suffer because everything has to be carried up with great effort and no medical rescue is possible. Looking around on the Web, it seems like this is still the case, even in 2016. For example, I see that helicopters can barely make the second base camp at 20,000 feet (i.e. 50% shy of the summit) and supplies are still being carried over a dangerous ice fall by teams of Sherpas, though at this lower altitude helicopters might compete.^[11] Now, I can't knock them for making a living, especially if that's what they have to do to do so, but still, well, if Everest is a mountain of dreams, then it makes me dream that if I were a big shot at a company like Starbuck's I'd want to arrange drones to fly over and drop off and ideally assemble all the components and supplies for a large made-to-order hot cappuccino machine at the summit. Or at least try to hit the occasional downed climber with a falling oxygen bottle. And the funny thing is, I look them up and I see that drones are flying over, mapping glaciers,^[12] making lovely photos.^[13] At lower altitudes in the Himalayas they drop supplies now.^[14] So I gotta ask:

a) Why haven't drone supply operations more or less totally taken over all the big Himalaya climbing routes?

b) Is it possible to make a helicopter that reliably carries a full load to the summit of Everest? With modern technology, could you put in computer stabilization so that even an inexperienced pilot can tell it to resist the wind and keep it flat and level under adverse weather conditions? For that matter, if you were willing to blow enough money on construction and fuel consumption (and what do Himalayan climbers do but blow money) could you make a helicopter that can fly against the wind in a class 5 hurricane, hover right amid the flames of a burning World Trade Center tower, and safely board people on and off over a gangplank in the process losing no more than a bit of scorched hair? Or is there some theoretical limit as to what can possibly be stabilized against, no matter how good the electronics? Wnt (talk) 20:03, 15 January 2017 (UTC)

Well if a vulture can fly at 37,000 feet I'm sure it must be possible to build a helicopter to get to 29,000 feet - just it hasn't been in anybody's interest to do so. It is easier to get things that fly rapidly to fly higher - but vultures don't tend to go very fast. Making a drone that goes that high might be a bit easier than convincing anyone to make a helicopter. Dmcq (talk) 23:55, 15 January 2017 (UTC)

Not only is it possible, it's already been designed and built, and almost 40 years ago, too: Aérospatiale_SA_315B_Lama 89.120.104.138 (talk) 13:37, 16 January 2017 (UTC)

Nope, about 12,000 feet short. 2601:646:8E01:7E0B:F88D:DE34:7772:8E5B (talk) 09:42, 17 January 2017 (UTC)

Odd, I'd think it would be worth it to the Chinese just to hear some Nepalis say "thank you for maintaining an airbase in the Tibet Autonomous Region"... Wnt (talk) 00:25, 16 January 2017 (UTC)

Didier Delsalle. --Hillbillyholiday ^talk 00:29, 16 January 2017 (UTC)

Well, a drone with just a mini-camera is one thing, but a full-size chopper for carrying supplies is another thing entirely -- a bigger payload requires more lift, which requires a bigger machine, which means still more lift -- and that means that the gross weight increases faster than the payload, until you reach a practical limit. And in the case of Everest, the high altitude compounds the problem -- thinner air means (1) less engine power, and (2) less rotor efficiency (these things compounding each other once again, meaning that the service ceiling decreases disproportionately as the gross weight increases). Now, you could try to overcome this in 4 ways -- you can try making the rotor bigger, but then you make it heavier, and above a certain size you'll run into problems with resonance; you can add more blades, but this also adds weight, and when you have more than 7 blades you start getting diminishing returns from each additional blade; you can use 2 rotors, but that also adds weight (not just the rotors, but the additional transmission shafts and gearboxes, and also additional structure for carrying the rotors) and mechanical complication; or you could spin the rotor(s) faster, but above a certain rotor RPM you'll run into advancing blade stall (which also occurs sooner at 29,000 feet than at sea level, because of the lower speed of sound). So, carrying a payload to the top of Mount Everest is in fact a very hard engineering problem -- not that it won't be solved someday, just not any time soon. 2601:646:8E01:7E0B:115A:F5FE:40F5:A40A (talk) 02:34, 16 January 2017 (UTC)

Another problem with manned helicopters is that to fly to that height they need to be pressurized, and this means the crew can't just jump out when they land and load in a patient to be evacuated, they would need people on the ground to load the patient into a sealed nacelle pod, and that pod would need to slowly increase the pressure from the starting pressure to that of the landing level pressure, so it can be opened when they arrive. Even an evacuation drone would still need that second part. StuRat (talk) 07:35, 16 January 2017 (UTC)

• A helicopter has landed on the peak of Everest - see Didier Delsalle. This needed the helicopter to be stripped back to the bare minimum (no extra seats, for instance) and very careful thermal riding to get to the summit. A helicopter has never been usefully to the summit, but Sudarshan Gautam was rescued pretty close to it at 7,800 m (25,590 ft) (see Eurocopter AS350 Écureuil#Operational history). So it is possible - so why isn't it common? This article is a pretty good summary: The problem is that it's only barely safe at the best of times - in good weather, the engine can just grab enough oxygen to keep you airborne, but good weather isn't exactly common on Everest, and Nepal doesn't exactly have a good track record for air safety - without good regulation, when there are multiple companies all competing to be the cheapest and highest-flying, safety goes out of the window. Smurrayinchester 08:23, 16 January 2017 (UTC)

The Delsalle case is interesting - it says that the weight was trimmed to increase the one-hour fuel range of the helicopter. So there actually is some kind of a physical limit here, though it also involves the breadth of the mountain and not just its height. But I don't know whether that limit can be evaded by making a much larger or a much smaller helicopter with proportionally much more fuel storage; I suppose in concept a more energy rich fuel might be used, or an in-flight automated refueling system, etc. The prospect of trying to steal a great pilot's skill and implement it standard in the helicopter computers, including some more effective imaging of winds, also seems interesting. Wnt (talk) 12:24, 16 January 2017 (UTC)

Re a): Something not so far addressed – doing it as much as possible (including the preliminaries) without machine assistance is kind of the point of the whole exercise. I mean, I've crossed the English Channel/La Manche a number of times by ferry (and gone under it several via the Chunnel), but some people still want to do it the hard way. {The poster formerly known as 81.81.230.195} 2.122.62.241 (talk) 12:15, 16 January 2017 (UTC)

The problem with that idea is that I'd expect those following it not to use fixed ropes on the ascent, for example, but to not care whether the supplies they find at Base Camp N were taken up by Sherpas two weeks before or by a bunch of little drones. Wnt (talk) 12:24, 16 January 2017 (UTC)

Probably not. But why would they want to use drones? In the short term, it's not likely to be cheaper, considering pretty much no one is doing anything remotely like that (see Delivery drones, there are a few minor trials but mostly it's just talk). And while there are perhaps some minor advantages in doing it somewhere like Everest (a lot less crowded than some other proposals and possibly the world media is less likely to care if you injure or kill a Sherpa then if you do so to some rural Japanese person), there are as mentioned above and should be obvious a lot more challenges. And you'd piss the hell out of the Sherpas who you still need as guides, to set up the ropes etc. Heck it seems doubtful that either they or the Nepalese government would allow it. (Well for the later, perhaps if you bribe the right people but you aren't exactly helping the business case with that.) It's not like there aren't already serious disputes [15] [16] [17] and ironically IIRC one of the people attacked was actually a helicopter pilot sometimes or often involved in rescue flights. All in all, this seems a lose lose proposition for everyone involved. To put if a different way, if Starbucks really think a coffee machine (which they'd also have to design, probably with pressurisation etc) on Everest is a good marketing stunt, they could just hire a bunch of Sherpas and find someone involved in the company to accompany it. At least then it's only going to backfire because people comment on more junk on Everest rather also because of the drone stuff. Nil Einne (talk) 16:13, 16 January 2017 (UTC)

• Helicopters (drone or not) must hover, and this is hard at high altitude. You need to hover to retrieve people or stuff, but not to deliver it. You can deliver using controllable parachutes from a fixed-wing aircraft. Of course, if this were done routinely, the mountain would soon be festooned with parachutes. You could probably work out a system that delivers heavy loads by a parachute that has some sort of balloon/drone combination to bring unloaded system back down to base. -Arch dude (talk) 04:32, 17 January 2017 (UTC)

Personally I wonder why a person would want to use a drone. What is the point of climbing Everest if it is not a challenge and there is no danger? One might as well have a pressurized funicular railway and a cafe selling cappucinos and Mount Everest souvenirs at the top. Dmcq (talk) 09:47, 17 January 2017 (UTC)

January 16

Why is the lymphatic system not symmetric in the body?

Why the lymphatic system is not symmetric in the body? I mean that the right side responsible for the right limb only while the left side responsible for the entire body.(Btw, is it the only system in the body that it is not symmetric or there are additional systems like that?) 93.126.88.30 (talk) 00:41, 16 January 2017 (UTC)

There are many, many systems that are not symmetrical. Try putting a mirror to your face so that you are looking at the left (or right) side of your face replicated - you will hardly recognise yourself. Have a look at the fluctuating asymmetry article. DrChrissy ^(talk) 00:46, 16 January 2017 (UTC)

thank you, but I believe that the lymphatic system is asymmetric prominently as you look at the anatomy of the body. 93.126.88.30 (talk) 01:13, 16 January 2017 (UTC)

the heart isn't symmetric. the lungs aren't symmetric (shape, # of lobes). The spleen, the pancreas, the liver, the stomach, the intestines. The kidneys are only very roughly symmetrical (position, blood supply). The aortic arch. The left and right laryngeal nerves. I see no reason to emphasize the assymetry of the lymphatics more than any one of these. - Nunh-huh 02:09, 16 January 2017 (UTC)

I would guess that the relationship of the right lymphatic duct and left lymphatic duct should be evaluated in a broader context in terms of the asymmetry of great arteries and great veins, but I haven't thought this through. Wnt (talk) 12:36, 16 January 2017 (UTC)

The lymphatic system is initially symmetrical but becomes asymmetrical during the later stages of ontogenesis. Ruslik_Zero 13:19, 16 January 2017 (UTC)

Thanks - figure 33 in that source is especially useful. To quote another source, "The thoracic duct develops during the seventh and eighth week of gestational life from two vessels anterior to the aorta, which become the left and right embryonic thoracic ducts. The left one gives rise to the upper third of the adult thoracic duct while the lower two-thirds of the adult duct arise from the right embryonic thoracic duct."[18] The right thoracic duct retains its outlet, though, and continues to pass lymph from the parts that didn't degenerate or fuse, i.e. bronchomediastinal trunk, subclavian trunk, and jugular trunk ... and in some individuals, the lower lobe of the left lung. Perhaps a closer look at that variation would shed some light into the process. It is striking that all the lymphatic and circulatory structures tend to be variable and to develop such asymmetries, as faithful servants of every variation of the developing body. There's also something of a comic resemblance of these duct outlets to an aspiration vacuum on a laboratory sink - I wonder to what degree the venous flow tends to suck the lymph out... funny thing is, central venous pressure is ~ 3 mm Hg, though jugular venous pressure is presumably often lower from being higher, and also has a relaxation phase. I wonder how congestive heart failure or even some poor sap just being hung upside down at a black site affects the lymphatic system... Wnt (talk) 17:21, 16 January 2017 (UTC)

Nobody has yet mentioned physical and functional asymmetry in the brain - see Brain asymmetry. DrChrissy ^(talk) 22:07, 16 January 2017 (UTC)

More extensive and in-depth discussions of functional brain assymetry may be found in our article Lateralization of brain function. One of many examples of functional and structural assymetry of the brain in that article is the placement of Broca's Area and Wernicke's Area - both of these are often found only in the left hemisphere. Many functional and structural brain assymetries are discussed in the article. loupgarous (talk) 00:57, 17 January 2017 (UTC)

What is the reason that chewing gum causes to appetite?

I'm looking for the physiological reason why chewing gum is a trigger for hunger? 93.126.88.30 (talk) 01:07, 16 January 2017 (UTC)

Googling "chewing gum is a trigger for hunger" returns several sites that claim that the production of saliva triggers the digestive system into thinking that there is food to be digested, making you hungrier. Rojomoke (talk) 03:26, 16 January 2017 (UTC)

I'll vouch for that. ←Baseball Bugs ^{What's up, Doc?} carrots→ 03:36, 16 January 2017 (UTC)

Also, the taste of sweetness, whether sugar or a substitute, may cause the body to anticipate digestion and release insulin, leading to lower blood sugar and hence hunger. A good test to distinguish this from the other reason would be to chew a type of gum with no sweetener. StuRat (talk) 07:37, 16 January 2017 (UTC)

According to early advertisements for Doublemint gum, ("double-strength" peppermint) stimulates salivation, aiding digestion -- not to mention soothing throats and mouths, quenching thirst, promote weight loss, slow tooth decay, make the day go by faster, soothe the tired and the nervous, have more fun, make you more attractive to the opposite sex, ... [19] 107.15.152.93 (talk) 12:16, 16 January 2017 (UTC)

...And who can forget this immortal quote: "I'm the Court Jester, and Wrigley's is the Court 'Digester'"[20] 107.15.152.93 (talk) 12:16, 16 January 2017 (UTC)

Lower sex drive during the daytime,higher sex drive at night

Do people have a lower sex drive during the daytime, and a higher sex drive during the night?Uncle dan is home (talk) 18:53, 16 January 2017 (UTC)

Nocturnal penile tumescence ("morning wood") and nocturnal clitoral tumescence seem to support that idea. From an evolutionary POV, before artificial lighting, there wasn't much else one could do to ensure the survival of one's genes at night, in the dark, other than sleep, so this was a good time for mating, while daylight hours were precious, and every minute needed to be spent hunting, gathering, making tools, scouting, etc. (After the discovery of fire, it was possible to do some things by firelight, but there's also a cost to that, such as the time taken to gather, break up, and dry the wood and the effort to light it, so it might be better to save the dry wood for emergencies, like cold or animal attacks, than keep the fire going all night long, every night.) StuRat (talk) 19:12, 16 January 2017 (UTC)

The overlapping articles Libido and Sexual desire list many contributory factors but do not claim a causative correlation with a person's Circadian rhythm. One's particular social demands and opportunities, which are very different for modern or prehistoric man, shape opportunities to act on or think about hormonal drives. Blooteuth (talk) 21:52, 16 January 2017 (UTC)

NPT and NCT are known to be signs of REM sleep: if you have any references to support their correlation with "higher sex drive during the night", StuRat, please provide them.

Likewise, your remarks about an evolutionary connection to prehistoric life activities sound superficially plausible – not surprising, since you're evidently reasonably intelligent and broadly knowledgable – but without references to or citations of any scholarly investigation into the subject, or obvious pointers to subjects that others can follow up, they are no more than your personal musings. Scientific references on the Science Refdesk, please. {The poster formerly known as 87.81.230.195} 2.122.62.241 (talk) 10:55, 17 January 2017 (UTC)

January 17

Three objects rearranged

We stack three ceramic pieces in the washroom and put a bar of soap on top. They are constantly being rearranged. Each piece can be upside down or not, and in any position (top, middle, bottom). How many different configurations are there? Many thanks to anyone who can help. :) Anna Frodesiak (talk) 00:29, 17 January 2017 (UTC) Can't you just tell your family to leave things alone so you don't have to come here and give me a headache before going to bed - hee hee. DrChrissy ^(talk) 00:55, 17 January 2017 (UTC)

DrChrissy, you can't tell them anything. They talk back. :) Anna Frodesiak (talk) 08:43, 17 January 2017 (UTC)

Anna, if the bar of soap is also considered in this calculation and considered to be placeable upside-down or right side-up, then there are 2x2x2x2 or 16 possible combinations. If you're considering only the ceramic pieces depicted in the graphic, those can be organised in 2x2x2 or 8 possible combinations. loupgarous (talk) 00:36, 17 January 2017 (UTC)

Hi loupgarous. No soap in the problem. Eight? That doesn't seem possible. Again, each can be upside down, and each can be in any position (top, middle, bottom). Are you absolutely sure? Best, Anna Frodesiak (talk) 00:45, 17 January 2017 (UTC)

48. Six orders (3×2), multiplied by 8 (2³) inversions. Andy Dingley (talk) 00:47, 17 January 2017 (UTC)

E/C :I'm not considering the soap. Each object can be in 2 orientations (upsidedown or right side up) and there are three pieces so there are 2³ orientations = 8. The pieces can be in 3 places so the number of places combinations is 3² =9. 8x9 = 72 total combinations. DrChrissy ^(talk) 00:49, 17 January 2017 (UTC)

Looks like Andy and I agree about the inversions, but disagree about the orders. DrChrissy ^(talk) 00:51, 17 January 2017 (UTC)

Pick a piece. One of three. Put it in a pile.

Pick another piece. One of two remaining. Put it on the pile.

Put the remaining piece on the pile.

Six. Andy Dingley (talk) 00:58, 17 January 2017 (UTC)

Good catch on places, Andy, Chrissy and Anna. There are 6 possible orders and 2x2x2=8 possible upside down/right side-up orientations in the array, giving a total of 6x8=72 different permutations of order x spatial orientation. loupgarous (talk) 01:14, 17 January 2017 (UTC)

6×8 = 48, not 72. StuRat (talk) 02:01, 17 January 2017 (UTC)

So, 72? That's the final number? No wonder it never looks the same. I must say, 72 really surprised me for only 3 objects stacked up. Thank you all! Anna Frodesiak (talk) 01:21, 17 January 2017 (UTC)

E/C I think I see why Andy and I might differ. Andy appears to be adding pieces to the pile. I have assumed that all 3 pieces are always in the pile, but only their places differ. DrChrissy ^(talk) 01:23, 17 January 2017 (UTC)

Yes, all three are always there. No more, no less. So, still 72? Anna Frodesiak (talk) 01:26, 17 January 2017 (UTC)

Nope, 48. See above. StuRat (talk) 02:01, 17 January 2017 (UTC)

Thank you, Stu, and thank you all, especially Andy who got it right first. Anna Frodesiak (talk) 02:18, 17 January 2017 (UTC)

You're welcome. (StuRat distributes multiplication tables to all concerned.) :-) StuRat (talk) 02:33, 17 January 2017 (UTC)

BTW, the number of arrangments of the 3 objects (ignoring the upside down options) can be calculated using factorial, hence $3!=3\times 2\times 1=6$. Nil Einne (talk) 04:39, 17 January 2017 (UTC)

• Or...

Position	Items (removed)	Orientations	Permutations
Top	1 (two)	2	2
Middle	2 (one)	2	4
Bottom	3 (none)	2	6

Combined permutations: 2 × 4 × 6 = 48   2606:A000:4C0C:E200:8097:8662:1582:8D5D (talk) 06:12, 17 January 2017 (UTC)

Thank you all again. Anna Frodesiak (talk) 08:43, 17 January 2017 (UTC)

• The number of permutations (the ordering) for 2-out-of-3 is (perhaps surprisingly) the same as for 3-out-of-3.

Build a pile of three. 6 permutations. Build a pile of two and "put the last one in an opaque box" - still 6, because putting the last one "on the top of the pile" or "back in the cupboard" is topologically the same thing. Andy Dingley (talk) 10:34, 17 January 2017 (UTC)

Inverse of pressure

I know that the inverse of speed is "pace" and the inverse of density is "specific volume". I was searching on Google for inverse of pressure but I can't find a term for that. I'm curious for what the term could be called; I can figure it out but it could take a bit of time and effort. Then I just found that the inverse of pressure is "specific surface area" which has units in m²/kg, while inversely kg/m² is the unit of pressure. I figured that out based from density differ in pressure only in power in the denominator part of the unit (kg/m² for pressure and kg/m³ in density) and 'volume' in specific volume downgrading to 'area' to make "specific area" and then I googled that and found the answer on myself. PlanetStar 05:35, 17 January 2017 (UTC)

So first of all I'm not sure that "pace" is really standard for "reciprocal speed". It's true that runners might say they're running at a "six-minute pace" (meaning six minutes per mile, i.e. 10 mph) but generalizing that into "pace = 1/speed" has the ring of WP:OR to me.

More important, pressure is not (properly) measured in kg/m^2. Pressure is force divided by area, not mass divided by area. You can measure pressure as kgf/m^2, where kgf is a rather nonstandard unit, "kilograms force", meaning the force needed to accelerate a one-kilogram mass at 1g.

The specific surface area article does not, unless I missed it, talk about 1/pressure. --Trovatore (talk) 06:04, 17 January 2017 (UTC)

I seen it on Google that pace can be the reciprocal of a speed in the context of running such as seen in the top result in that page. As kg and lbs are units of weight, the units of weight can be used in units of pressure, like pounds per square inch or psi, therefore they can be flipped to make square inch per pound or sip which is an imperial unit of specific area. And I don't see that it said that it is inverse of pressure in that article either, though in my opinion specific area is the inverse of pressure. PlanetStar 06:23, 17 January 2017 (UTC)

So the shibboleth I've been trying to avoid here is that you're confusing weight and mass. The reason I've been trying to avoid it is that people are a little too insistent on it, in a linguistic sense — in fact one of the meanings of "weight" in English is actually "mass", and there's nothing wrong with that.

But in any case kilograms, according to standard usage, are a measure of weight-in-the-sense-of-mass, not weight-in-the-sense-of-force, and kg/m^2 is not a unit of pressure, although kgf/m^2 is. --Trovatore (talk) 06:31, 17 January 2017 (UTC)

Do small children have more nerve endings per unit skin area than grown ups?

Small children seem to feel more pain during injections than grown ups, is that because they have more nerve endings per unit skin area? Count Iblis (talk) 08:33, 17 January 2017 (UTC)

That could be the case, but the more likely explanation is that grown-ups have simply built up more pain tolerance from all those small injuries in childhood and adolescence. 2601:646:8E01:7E0B:F88D:DE34:7772:8E5B (talk) 09:40, 17 January 2017 (UTC)