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March 14

Polyethylene Glycol

After hearing different answers, I wish to ask: Does Polyethylene Glycol contains calories when consumed by humans? thanks. 79.179.193.243 (talk) 03:03, 14 March 2014 (UTC)[reply]

No. See [1] and [2] for a few examples. No sites I can find note any nutritive value for it at all. It should also be noted that food does not contain calories. It provides them. Calories are a measure of food energy. Most substances don't provide any food energy; roughly speaking only a few classes of compounds can be broken down by your body to provide you with net energy, the article food energy notes what those are. Part of the problem is the use of the word polyol which really refers to two (essentially) unrelated classes of compounds. Polyol can refer to sugar alcohols, which do provide food energy, but it can also refer to polymers made from alcohol monomer units. Polyethylene glycol is this kind of polyol, which is unrelated to sugar alcohols. --Jayron32 03:15, 14 March 2014 (UTC)[reply]

It sounds like some unsung heroes of science (I mean, studying diarrhea...) believe that PEG is not metabolized by the human or bacterial components of the digestive system. [3] I would be suspicious that if someone made a long-term habit of eating large amounts of it that eventually the bacteria would find a way, but that's not discussed here, hopefully due to lack of experimental data! Wnt (talk) 03:20, 14 March 2014 (UTC)[reply]

There are certainly bacteria that can metabolize it [4], though not in bacteria you would want to find in your own body (specifically flavobacterium and pseudomonas). Someguy1221 (talk) 03:27, 14 March 2014 (UTC)[reply]

(edit conflict) Regarding that, Wnt, PEG has medicinal use for the purpose of whole bowel irrigation, often in preparation for a colonoscopy. In basic terms, it cleans you out entirely so that they can send cameras up to take a peak. Diarrhea is basically what it is intended to do to you, "whole bowel irrigation" is a polite term for "medically induced diarrhea". --Jayron32 03:30, 14 March 2014 (UTC)[reply]

I think that last bit is a little misleading: diarrhea implies watery feces only barely controlled (if you're lucky); PEG is routinely recommended as a simple stool softener. No... explosions or other unpleasantness. Matt Deres (talk) 12:31, 16 March 2014 (UTC)[reply]

Jayron, sorry, Provides. wrong word usage. Anyways, I understand from you in short that it does not provide calories to humans at all. 79.179.193.243 (talk) 03:23, 14 March 2014 (UTC)[reply]

(edit conflict)My understanding is that polyethylene glycol is not metabolized by the human body, and thus cannot be stored or provide calories. There is research on actually injecting animals with PEG directly into the blood stream or spine, which mention that it "dissolves away". Not sure how that actually happens though [5]. But theory goes it should not enter your circulation from the gastrointestinal tract. So yeah, if your body can't absorb it, and it can't break it down, no calories. Someguy1221 (talk) 03:24, 14 March 2014 (UTC)[reply]

So far as I can tell, the known means of degrading PEG are very slow, not likely to be too relevant for digestion. The problem is that they are essentially an "exopegylase" rather than an "endopegylase", trimming the molecule with a laborious sequence of reactions at the far end.[6][7][ I still bet that if you feed it to an experimental animal or human long enough, eventually something will figure it out - the stuff seems to just beg to be hydrolyzed into ethanol and used for food - maybe this is such an enzyme. It would only take a little to break up the chains into manageable pieces and then the end-to-end degradation could finish it off. Wnt (talk) 20:34, 14 March 2014 (UTC)[reply]

Hi Wnt. sorry, but I don't have enough knowledge on the subject to generally understand what you wrote. can you please simplify it? thanks. 79.179.193.243 (talk) 01:33, 15 March 2014 (UTC)[reply]

There's no known way that humans could get nutrition out of polyethylene glycol - all it does is cause diarrhea and pass out of the body. But it isn't absolutely clear to me that if a person ate some amount of it every day for years, that their intestinal bacteria wouldn't eventually be able to process it into a possible food source (such as ethyl alcohol). Basically, I am just thinking very hypothetically about how much the intestinal flora (which might spread) can help a population adapt to a new food source. Wnt (talk) 02:07, 15 March 2014 (UTC)[reply]

Yeah, no. It's basically liquid plastic. You'd get as much nutrition eating the bottle it comes in. --Jayron32 02:24, 15 March 2014 (UTC)[reply]

Which one of these possibilities did you mean, Jayron? -- Jack of Oz ^{[pleasantries]} 03:14, 15 March 2014 (UTC)[reply]

Definition #1 here. --Jayron32 03:19, 15 March 2014 (UTC)[reply]

If it were polyethylene, I'd say that, but this is an ether that, in principle, should be possible to hydrolyze, whether directly (doubtful) or following oxidation of an internal carbon in a manner somewhat analogous to the degradation at the end. But admittedly, ethylene glycol poisoning is more likely than nutritional benefit, come to think of it. Wnt (talk) 03:57, 15 March 2014 (UTC)[reply]

Freezing water

Lets say I have a normal bucket of water and it's lukewarm. I also have an icecube that has been cooled all the way to -100 celsius. Would the bucket freeze if I dropped that icecube into it? What if the icecube is like 200 or 500 degrees negative celsius? — Preceding unsigned comment added by 2001:708:110:1004:CACB:B8FF:FE24:8A97 (talk) 09:45, 14 March 2014 (UTC)[reply]

The lowest possible temperature is about -273 degrees Celcius. The freezing of water requires the removal of a lot of heat. One icecube is never going to be enough to freeze a bucket of water, no matter how cold the cube is (unless of course the cube is so large that it fills a large portion of the bucket).

To put it in more quantitative terms: to freeze 1 kg of water you need to remove about 334 kJ of heat. The heat capacity of ice between - 100 and 0 degrees is roughly 1.7 kJ/kgK on average, so that means that 2 kg of ice of - 100 degrees can freeze about 1 kg of cold water, in other words the icecube would have to fill 2/3 of the bucket. - Lindert (talk) 09:50, 14 March 2014 (UTC)[reply]

The question can be answered with a simplifying assumption that the bucket is thermally insulated from the environment; that means we can wait until ice/water/bucket have equalised at temperature T °C. In the process:

the ice cube gains

(T - T_i) M_i 2.05 joules

where T_i is the initial temperature of the ice (e.g. -100 °C), M_i is the mass of the ice in gm and 2.05 J/gm °C is the specific heat of ice.

the water first loses

( T_w - T) M_w 4.186 joules

where T_w is the initial temperature of the water, M_w is the mass of the water in gm;

the water then if T sinks to 0 °C further loses its Latent heat of fusion which is 334 M_w joules;
the bucket itself loses

( T_w - T) M_b S_b joules

where M_b is the mass in gm of the bucket and S_b is the Specific heat of the bucket material, possibly steel S_steel = 0.49 joules/gm °C.

When values are provided for T_i T_w M_b M_i and S_b we have a neat homework question: does T fall below 0 °C i.e. does all the water freeze? However to make a practical experiment the thermal isolation must be very good because ice itself is a poor heat conductor and will tend to float a long time on slightly warmer water. As already noted, T_i cannot be less than -273 °C 84.209.89.214 (talk) 11:38, 14 March 2014 (UTC)[reply]

Yes it can −273.15° (theoretically) :-) Richerman (talk) 19:49, 14 March 2014 (UTC) [reply]

Human instinctive behaviour in nightlife

I read an article in a scientific journal recently about how humans tend to most clearly exhibit their natural instincts in clubs, both in terms if survival and finding a mate. But is there any truth to this? I know alcohol lowers inhibitions but surely that only shows the individual's personality more than anything else. Some get angry, some are quiet, some are aggressive. In terms of "finding a mate" some try, some don't in clubs and some are successful and some aren't, but I would have thought this is more to do with personality again more than instincts. — Preceding unsigned comment added by 194.66.246.46 (talk) 09:56, 14 March 2014 (UTC)[reply]

Which journal was that ? I'm curious how they figured out what a "natural instinct" is in humans. Sean.hoyland - talk 10:07, 14 March 2014 (UTC)[reply]

"Natural instincts" are exhibited in all sorts of ways. There are a lot of "scientific journals" out there, some more reliable than others, so it would help to know which one and exactly what they claim.--Shantavira|^{feed me} 11:27, 14 March 2014 (UTC)[reply]

Perhaps: (?)

Gad Saad, Ph.D (November 19, 2012). "Sexual Signaling at a Nightclub". Homo Consumericus. Psychology Today.

Grazian, D. (2007). "The girl hunt: urban nightlife and the performance of masculinity as collective activity". Symbolic Interaction, 30(2), 221-243. DOI: 10.1525/si.2007.30.2.221 (Abstract) —71.20.250.51 (talk) 16:01, 14 March 2014 (UTC))[reply]

Cardboard

If a human tried to digest a small piece of corrugated cardboard, what would happen? --Bnā We must Eashgf (talk) 13:38, 14 March 2014 (UTC)[reply]

Cardboard is made of cellulose and glue. Humans can't efficiently digest cellulose, so the cardboard would pass through, acting as sort of a rough fiber. Generally speaking, small quantities of cardboard would not be harmful to your health; however, it may have toxic glue or other additives. Justin15w (talk) 13:46, 14 March 2014 (UTC)[reply]

Glad you qualified that. See Kraft process - doesn't sound tasty. Wnt (talk) 14:50, 14 March 2014 (UTC)[reply]

So that's the process they use to make Kraft American "cheese" slices ! :-) StuRat (talk) 18:51, 14 March 2014 (UTC) [reply]

Metals Fusing in Space

I read something a few days ago which I find very difficult to believe. It said that if two identical metals touched in space, they would fuse together - like cold fusion. The author said something to the effect that as there were no other particles to keep the two metals apart, they would automatically fuse together. Is this true, or is this an early April Fool's joke? KägeTorä - (影虎) (TALK) 15:21, 14 March 2014 (UTC)[reply]

Two unoxidised metals will indeed fuse together. On Earth, the oxygen in the air stops this from happening. It has nothing to do with cold fusion though.217.158.236.14 (talk) 15:25, 14 March 2014 (UTC)[reply]

Yup - I think you mean 'like welding' Cold fusion is (or would be) something else entirely. AndyTheGrump (talk) 15:27, 14 March 2014 (UTC)[reply]

Cold welding.--Shantavira|^{feed me} 15:54, 14 March 2014 (UTC)[reply]

You might also be interested by the wringing together of gauge blocks, smooth blocks used in tool shops. μηδείς (talk) 17:03, 14 March 2014 (UTC)[reply]

And we need consider what "touch" means. If one hits another at high speed (the most common type of contact in space), they won't fuse, and may each break up if the speed is high enough. They need to be still or almost still relative to one another to fuse (does anybody know exactly how still ?). At some point the relative velocities will be low enough that gravitational attraction should held them together long enough to fuse. StuRat (talk) 18:21, 14 March 2014 (UTC)[reply]

How still? Enough that motion doesn't overcome Intermolecular force (presumably). ~:71.20.250.51 (talk) 18:37, 14 March 2014 (UTC)[reply]

Note that metal objects made on Earth will be surrounded by an oxide layer. I'd assume that metal oxides, just like the oxides of lunar regolith, would fail to fuse because of the more covalent and localized nature of the metal-oxygen bonds? Wnt (talk) 20:15, 14 March 2014 (UTC)[reply]

Gauge blocks are made of special alloys and kept oiled to help prevent this. μηδείς (talk) 20:34, 14 March 2014 (UTC)[reply]

With metals, the electrons bind the metal atoms closer, but the atoms are still separate. In Cold Fusion, hydrogen (isotope) nuclei are fused to form a new type of atom, Helium , and this requires a lot of energy. Star Lord - 星王 (talk) 15:02, 15 March 2014 (UTC)[reply]

If the surfaces are perfectly smooth then the atoms from the different parts will fit into the crystal structure of the merged metal. You can also consider the fact that the laws of physics imply invariance under time reversal. So, if we break a metal into two parts, the time reversal of that act would merge the two metals back together without any need to glue or weld them together. In that case the two parts fit exactly toghether. If we are given two pieces that were not created from a single piece, then they would not fit toghether unless the surfaces of the two parts are perfectly smooth.Count Iblis (talk) 15:25, 15 March 2014 (UTC)[reply]

Plurals of Abbreviated Words

[Moved to language desk]

Hot water

What's the highest temperature of water (or other liquid) that's tolerable for (a) drinking, (b) being immersed in? --rossb (talk) 16:20, 14 March 2014 (UTC)[reply]

In case of b) this is slightly above 40 C. The body then cannot keep its body temperature from rising to the water temperature which will eventually be fatal. Count Iblis (talk) 16:26, 14 March 2014 (UTC)[reply]

That depends on how much of the body is immersed in the water and if cooling methods like fans and drinking cold fluids can be used. And much hotter water would be needed to kill you quickly. StuRat (talk) 18:36, 14 March 2014 (UTC)[reply]

... and for a) I would guess around 80 C, but it seems to vary between individuals and depends on how carefully and how fast they drink. I suspect that people who consume drinks at this high temperature have some trick for reducing the temperature in the mouth to below 70C within a very short time. I burn my tongue and top lip! For most people, the temperature will drop to below 50C as the liquid goes down the gullet, and will fall to below 40C in the stomach. Dbfirs 22:13, 14 March 2014 (UTC)[reply]

The British Health & Safety Executive require that bathing water for vulnerable people should not exceed 44C (110F), or 46C if supervised. Water just five degrees hotter than this (49C, 120F) can cause minor damage to the outer layer of skin in 90 seconds, and a serious scald in ten minutes. Immersion in water at 71C (160F) can result in serious scalds (third-degree burns) in as little as one second. Don't try it! Dbfirs 14:07, 15 March 2014 (UTC)[reply]

44 or 46C seems like it would cause overheating of the core body temp, since that should be around 37C. How is this prevented ? StuRat (talk) 15:13, 15 March 2014 (UTC)[reply]

By sipping slowly. ←Baseball Bugs ^{What's up, Doc?} carrots→ 17:00, 15 March 2014 (UTC)[reply]

Sipping bathwater ? Ewwww ! StuRat (talk) 19:05, 15 March 2014 (UTC) [reply]

Ha. Mixed up Dbfirs and yourself while in edit mode. :( ←Baseball Bugs ^{What's up, Doc?} carrots→ 07:40, 16 March 2014 (UTC)[reply]

By not submerging the head. You lose an immense amount of head through the head. 86.152.129.197 (talk) 02:47, 16 March 2014 (UTC)[reply]

Especially if you are Marie Antionette. StuRat (talk) 15:29, 16 March 2014 (UTC) [reply]

Given the modern habit of labelling disposable coffee cups with warnings that the contents may be hot, I'm wondering if there are official rulings in various places as to what temperature requires such a helpful warning. HiLo48 (talk) 22:00, 15 March 2014 (UTC)[reply]

Here in the USA, water heaters are required to display a table of time-to-scald vs. water temperature (mine sure does, and I know from personal experience that the times in the table are calculated with quite a safety margin too). 24.5.122.13 (talk) 08:45, 16 March 2014 (UTC)[reply]

In the UK, hygiene regulations require reheated food to be reheated to at least 82°, which is too hot for most people to eat. --ColinFine (talk) 12:29, 16 March 2014 (UTC)[reply]

Slurping involves taking in a bit of hot liquid while bringing in sufficient cool air to rapidly reduce the temperature of the liquid while preventing prolonged contact with the lips, and other mouthparts. (It's amazing Wikipedia lacks an article on this notable, useful, and annoying practice). I am able to slurp coffee at a temperature which would certainly cause second degree burns if I simply sipped it. Edison (talk) 22:53, 16 March 2014 (UTC)[reply]

Body painted blindness

Would a color blind person (Monochromacy type) perceive a body painted person as naked?--85.52.89.152 (talk) 20:41, 14 March 2014 (UTC)[reply]

That would depend on the darkness of the paint. If it was just as dark as the person's skin, then it wouldn't be visible to the colorblind person. If it was significantly lighter or darker, then it would be visible.

Also note that normal vision individuals would see the same thing in dim light, where color vision is absent. StuRat (talk) 21:35, 14 March 2014 (UTC)[reply]

Would we perceive a body painted person in a black and white picture as naked? OsmanRF34 (talk) 23:19, 14 March 2014 (UTC)[reply]

Also note that color blindness rarely leads to completely monochromatic vision -- the vast majority of colorblind people can in fact perceive some colors, just not very well. 24.5.122.13 (talk) 01:19, 15 March 2014 (UTC)[reply]

Agreed - see Types of Colour Blindness which explains what colour blind people actually see. Alansplodge (talk) 13:05, 15 March 2014 (UTC)[reply]

First riddle me whether a non color blind person would see a person painted in "flesh tones" (their own, or those of any race?) as being naked. For that matter, whether the titlillation of the art form is based primarily on us seeing body paint of any color as not quite nakedness. Bonus points: whether women coerced into wearing ugly Western style cosmetics should be counted as wearing a hijab for legal purposes. Wnt (talk) 15:39, 16 March 2014 (UTC)[reply]

What is this

[8] One of those animated gifs of a reaction in a beaker (erlenmeyer flask?) I'm curious what it is. What the reacting chemicals are, not the flask. -71.238.189.52 (talk) 23:35, 14 March 2014 (UTC)[reply]

It looks like elephant toothpaste. Red Act (talk) 23:58, 14 March 2014 (UTC)[reply]

Thanks! -71.238.189.52 (talk) 00:18, 15 March 2014 (UTC)[reply]

Not Erlenmeyer flask, probably volumetric. Rmhermen (talk) 02:02, 15 March 2014 (UTC)[reply]

Volumetric flask indeed. DMacks (talk) 07:43, 16 March 2014 (UTC)[reply]

March 15

Mass and space and nothingness

Is it true that space cannot exist without mass? If so, how can it be that the universe formed out of nothing? If there was originally no space and no mass, what came first? Also, if there was nothing at the start, in what space did that nothing exist?--109.144.153.12 (talk) 00:59, 15 March 2014 (UTC)[reply]

Space exists because there are things in space which define the space. If you have no objects, you have no frame of reference, so you have no space to define. It isn't mass per se (though all objects have mass, because mass and volume are the two fundamental properties of matter) but the presence of a thing to define dimensions of space. --Jayron32 02:02, 15 March 2014 (UTC)[reply]

See Massless particle. -- Jack of Oz ^{[pleasantries]} 03:09, 15 March 2014 (UTC)[reply]

Massless particles are not matter.--Jayron32 04:48, 15 March 2014 (UTC)[reply]

Don't they contain energy, and isn't there an equivalence of matter and energy? -- Jack of Oz ^{[pleasantries]} 07:00, 15 March 2014 (UTC)[reply]

"Matter" is often defined as any particle with non-zero rest mass, hence because massless particles have zero rest mass, then by definition they are not matter. Dragons flight (talk) 07:15, 15 March 2014 (UTC)[reply]

There may have been no beginning, only a current universe we are in which may be one of many. Or if time only exists in a universe how can one talk of a time before the universe? Dmcq (talk) 11:48, 15 March 2014 (UTC)[reply]

Where does the premise: "If there was originally no space and no mass" come from? As far I recall the Big Bang, there was an initial mass and a (small) initial space. Star Lord - 星王 (talk) 14:54, 15 March 2014 (UTC)[reply]

There may have been a lot of energy around at the time, but not mass I suggest. Of course later on some of the energy was converted to mass.--31.55.104.196 (talk) 00:34, 16 March 2014 (UTC)[reply]

Right you are. Star Lord - 星王 (talk) 11:33, 17 March 2014 (UTC)[reply]

This is a difficult question. Our article on Mach's principle does a pretty good job of explaining the issues and the way various people have thought about them. Looie496 (talk) 15:58, 15 March 2014 (UTC)[reply]

Maybe there was no start, to start with. OsmanRF34 (talk) 20:14, 15 March 2014 (UTC)[reply]

Is it true that space cannot exist without mass?

Definitely not. See vacuum, which is space without mass.

If so, how can it be that the universe formed out of nothing?

We don't know that the universe formed out of nothing, and no reputable scientist would claim it did.

If there was originally no space and no mass, what came first? Also, if there was nothing at the start, in what space did that nothing exist?

Again, we have no evidence that the universe formed out of nothing, or that there was originally no space and no mass. --Bowlhover (talk) 20:59, 15 March 2014 (UTC)[reply]

Coffee to help you sleep?

request for medical OR, answer rejected by OP

The following discussion has been closed. Please do not modify it.

My mum sometimes has trouble getting to sleep. Am I right in thinking you could leverage caffeine to make sleep easier by drinking coffee in the morning so that in its absence in the evening you'd be more tired? --78.148.110.69 (talk) 02:30, 15 March 2014 (UTC)[reply]

I'm afraid we cannot offer medical advice, including therapies for sleep problems. You're going to have to tell your mum to seek the advice of a professional directly. --Jayron32 02:32, 15 March 2014 (UTC)[reply]

Lame. I'm gonna get her to try my coffee idea. --78.148.110.69 (talk) 02:38, 15 March 2014 (UTC)[reply]

Sorry, but "lame" is not a reason to break ITN policy. μηδείς (talk) 02:58, 15 March 2014 (UTC)[reply]

I think it is a fact that caffeine is a stimulant. Draw your own conclusion.--31.55.104.196 (talk) 00:28, 16 March 2014 (UTC)[reply]

Yes, that's why Modafinil is usually prescribed. Count Iblis (talk) 02:24, 16 March 2014 (UTC)[reply]

March 16

Practical magnetics problem

If a magnetic material is fully saturated, will it exhibit any loss to an applied alternating magnetic field? In other words, what is the value of u when the material is magnetically saturated?--31.55.104.196 (talk) 00:20, 16 March 2014 (UTC)[reply]

That didnt come out right. I meant mu prime prime. Wiki markup seems to put that inti italcs.--31.55.104.196 (talk) 00:40, 16 March 2014 (UTC)[reply]

Try this: μ''. StuRat (talk) 01:17, 16 March 2014 (UTC)[reply]

You can apply "nowiki" to itself: <nowiki>μ''</nowiki> —71.20.250.51 (talk) 01:34, 16 March 2014 (UTC)[reply]

Try this: μ″. —Tamfang (talk) 08:06, 16 March 2014 (UTC)[reply]

Certainly a material can become "saturated," but in view of the exacting language in "any loss," I wonder about "fully saturated" since the B field approaches an asymptote, but can always increase a tiny amount if the H field increases, according to Saturation (magnetic). Edison (talk) 22:43, 16 March 2014 (UTC)[reply]

Should have mentioned its fairly square loop ferrite. So can I assume negligible core loss in a ferrite material if it is fairly heavily saturated? I think so but Im not sure. Im not talking about resistive losses due to eddy currents.--86.179.250.140 (talk) 15:14, 17 March 2014 (UTC)[reply]

Philip experiment

Philip Experiment. Philip experiment on youtube. I know it is probably a hoax, but I still don't understand what was really going on even after I read the article? The group probably imagined all the noises. My question is was the table really moving by itself? Was the table actually floating above the ground by itself? If the floating table was just the participants' hallucinations then how can I see it in the video? How could they capture their hallucination on video? Or was there some kind of trick behind the scenes? 75.168.134.220 (talk) 06:52, 16 March 2014 (UTC)[reply]

That video is a documentary about the experiment, as the description says: "A story about this experiment done in the early 1970's". None of it is actual footage. --140.180.249.239 (talk) 07:41, 16 March 2014 (UTC)[reply]

Is that mean all of the things happened in the footage were made up? — Preceding unsigned comment added by 75.168.134.220 (talk) 16:37, 16 March 2014 (UTC)[reply]

It means they were "reenactments," not footage from the original experiments. — The Hand That Feeds You:^Bite 20:16, 16 March 2014 (UTC)[reply]

Self-defense

It's widely known that when protecting yourself against a man, kicking his testicles is a good way to cause extreme pain. What about women? Where should one strike to cause the most pain for the least force? --140.180.249.239 (talk) 07:31, 16 March 2014 (UTC)[reply]

Considering that men are generally stronger than women, they may simply restrain women without the need to hit them. But in extreme cases and when you don't know any submission hold, my bet would be celiac plexus, as in addition to pain hitting it induces temporary breathing problems (but even then - do not hit by knee!). Brandmeister^talk 11:19, 16 March 2014 (UTC)[reply]

Note also that the groin is a very hard area to hit effectively if the opponent expects an attack. We have very good reflexes that way. --Stephan Schulz (talk) 12:15, 16 March 2014 (UTC)[reply]

A blow to the kidneys is extremely painful, but you have to hit a person on the back (to the side, just above belt level). That's not particularly useful for self-defense, though. Looie496 (talk) 14:00, 16 March 2014 (UTC)[reply]

Women (among many others) hate it when you gouge their eyes, and even a baby can do it. InedibleHulk (talk) 14:15, March 16, 2014 (UTC)

"kicking his testicles is a good way to cause extreme pain." One who has studied judo might question that it is a "good way" for an attacker without training, since anyone with a little training in judo might be able to dodge the kick and grasp the attackers foot, leaving the attacker very vulnerable to the defender's move of sweeping the attacker's other foot out from under her, causing her to fall on her back. It would be a good way for someonewell trained in martial arts to attack a man. Edison (talk) 00:46, 18 March 2014 (UTC)[reply]

Waist–hip ratio

What is meant when a person has a "high waist–hip ratio"? (as seen in "Lifestyle" section of Diabetes mellitus type 2). Don't understand what that mean. Please link to my user page when you reply. HYH.124 (talk) 08:26, 16 March 2014 (UTC)[reply]

HYH.124, are you asking how to obtain the ratio? It's very simple: just measure the waist, then measure the hips (at positions shown in the article you link), then divide the first by the second. Ideally your answer should no more than 0.7 or 0.9, depending on your gender. Please clarify if you were asking about something else. Dbfirs 09:42, 16 March 2014 (UTC)[reply]

User:Dbfirs: I was asking how many is considered high. Also I am actually asking how one would shape/look like if one has "high waist-hip ratio". HYH.124 (talk) 09:44, 16 March 2014 (UTC)[reply]

The right-hand example in the picture of waist–hip ratio illustrates a high ratio. Also from the article "abdominal obesity is defined as a waist–hip ratio above 0.90 for males and above 0.85 for females". Dbfirs 10:10, 16 March 2014 (UTC)[reply]

Thanks for explaining. HYH.124 (talk) 12:18, 16 March 2014 (UTC)[reply]

Aircraft wing deformation

Do aircraft wings gradually bend and deform due to engines suspended below them? What is used to prevent that? --93.174.25.12 (talk) 11:11, 16 March 2014 (UTC)[reply]

There are two relevant types of deformation:

1) Elastic deformation. This is the type of deformation where the object returns to it's original shape once the force (engine weight, in this case) is removed.

2) Plastic deformation. This is the type of deformation that does not return to it's original shape.

Most materials first undergo elastic deformation with a small force and then plastic deformation with a larger force, although how much of the total occurs in each range varies wildly (with elastic having a larger elastic deformation range and plastic having a larger plastic deformation range). Metals have moderate amounts of deformation in both ranges. So, as long as the force (engine weight) is kept below the line where plastic deformation will occur, then the sagging under the engine weights won't bend the wings permanently.

If this was an issue, I'd expect supports to be mounted under plane wings while on the ground (I do expect they would add supports when doing work on the wings which lessens their strength for a while). Also note that aerodynamic lift causes the wings to bend upwards while in flight. This bending down when on the ground and back up in the air could also lead to metal fatigue, but that's another issue. StuRat (talk) 15:13, 16 March 2014 (UTC)[reply]

While not the engines the Learjet 25 and the Learjet 35 that were/are stationed at Cambridge Bay Airport are never fuelled up until the destination was known. According to the operators this was to reduce the stress on the wings. Of course there is no point in putting fuel in to go to Edmonton International Airport (969 nautical miles (1,795 km; 1,115 mi)) if you are only going to Gjoa Haven Airport (204 nautical miles (378 km; 235 mi)). CambridgeBayWeather (talk) 17:01, 16 March 2014 (UTC)[reply]

The weight of engines on the wing, fuel in wing tanks, and weight of the wing structure cause the wing to deflect but the wing does not deform. Permanent deformation is prevented simply by building the wing strong enough to avoid permanent deformation, even under the most severe loads likely to be imposed on the aircraft in service. This is no different to designing a bridge or a multi-storey building so that it can withstand all loads likely to be imposed on it in service.

Locating engines on the wing is actually much better from a structural perspective than locating them on the fuselage, such as on the Boeing 727 and Hawker Siddeley Trident! When the aircraft is in flight, the lift on each half-wing (the left half-wing and the right half-wing) is pushing the half-wing upwards, creating a substantial bending moment that reaches its maximum at the wing root, next to the fuselage. If an engine is located on each half-wing, the weight of the engine is pushing downwards and causing a reduction in the bending moment at the wing root. This phenomenon is called bending moment relief and it allows the airframe designer to use less metal in the wing structure and this leads to a lighter airframe. In contrast, the engines in the Boeing 727, Trident etc provide no bending moment relief. Engines buried in the wing root, adjacent to the fuselage, as seen in the De Havilland Comet and the V bombers, provide a little bending moment relief but not as much as engines located further outboard on the wing. Four-engine aircraft such as the Boeing 747 achieve substantial bending moment relief, especially from the outer engines. The maximum bending moment relief is achieved by moving some of the aircraft's weight to the tip of each half-wing; this explains the fuel tanks on the wing tips of some aircraft such as the Learjets and Mitsubishi MU-2. Dolphin (t) 23:37, 16 March 2014 (UTC)[reply]

Which plant is this ?

which plant ? http://i.imgur.com/ODXwL9s.jpg — Preceding unsigned comment added by 182.185.191.116 (talk) 12:36, 16 March 2014 (UTC)[reply]

Hard to say from that picture. Maybe a Phlox of some kind? --Jayron32 02:36, 17 March 2014 (UTC)[reply]

Which insect is this ?

Which insect is this ? the legs are orange/red coloured.

Superior view http://i.imgur.com/tpVz3cP.jpg

Lateral view http://i.imgur.com/TcUnn4M.jpg — Preceding unsigned comment added by 182.185.191.116 (talk) 12:41, 16 March 2014 (UTC)[reply]

It's a moth, for starters. Not sure of the specifics, but I'm almost certain the same kind are on my house every August in Northern Ontario. Might help. Of course, lepidopterists are a picky bunch. May have a slightly different cousin there. InedibleHulk (talk) 13:31, March 16, 2014 (UTC)

Actually, the antennae are different. That might be an ugly butterfly. Or whichever gender mine aren't, maybe. InedibleHulk (talk) 13:34, March 16, 2014 (UTC)

Comparison of butterflies and moths makes me think I was right the first time. InedibleHulk (talk) 13:39, March 16, 2014 (UTC)

SO, this is a moth ? How can I determine it's gender ? which other views are needed for species determination ? — Preceding unsigned comment added by 182.185.191.116 (talk) 14:30, 16 March 2014 (UTC)[reply]

Yes, a moth. That dude looks like a lady. Mine have those feathery ones. Shorter, too. I think the views are good (high detail, too), if someone smarter on moths than I sees them. If nobody like that shows up here, you can try sharing the picture with BugGuide. InedibleHulk (talk) 14:42, March 16, 2014 (UTC)

I have always found What's That Bug very helpful, you may have to wait for a while but the 5 or 6 times I have used it they came up trumps. Richard Avery (talk) 14:43, 16 March 2014 (UTC)[reply]

This photo reminds me of a wooly bear (Isabella Tiger Moth), but the black markings are much weaker than those in [9] and the coloration seems more orange. Either it's simply a color phase from a region not often represented in this photo collection, or some other species, likely somewhat closely related. Wnt (talk) 15:44, 16 March 2014 (UTC)[reply]

The original question was posted from Pakistan, so not likely. Alansplodge (talk) 18:28, 17 March 2014 (UTC)[reply]

Main Battle Tank (Maintenance)

It is always mentioned by many military experts that Russian tanks require more maintenance than western why ? and what are the maintenance requirements generally in a tank ? Tank Designer (talk) 13:36, 16 March 2014 (UTC)[reply]

Russian main battle tanks are more likely to be used close to home (say for invading the Ukraine), so sending them home for maintenance is more feasible than US tanks, unless the US plans to invade Canada or Mexico. This fact may have affected the maintenance specs for each. StuRat (talk) 15:24, 16 March 2014 (UTC)[reply]

Or Cuba? But first, I'd like to see these "military experts". For many kinds of equipment, Russian/Soviet designs are more rugged and require less maintenance than the Western equivalent. Compare AK-74 and M16, or, historically, Panther tank and T-34. --Stephan Schulz (talk) 15:31, 16 March 2014 (UTC)[reply]

I don't see the US invading Cuba, as it's simply not militarily important enough to warrant an invasion anymore (unless they offer to host Russian nukes again). And if the US did invade, they could do tank maintenance at Gitmo. StuRat (talk) 16:55, 16 March 2014 (UTC) [reply]

I think the main concern for US tank crews is what CDs to take with them. KägeTorä - (^影_虎) (Chin Wag) 15:54, 16 March 2014 (UTC)[reply]

You can't go wrong with Clash's Combat Rock — Ahhh, the good-ol'days! —71.20.250.51 (talk) 16:25, 16 March 2014 (UTC)[reply]

Can anyone tell me what are the maintenance aspects in the tank engine or give me a link so I can read it alone ? Tank Designer (talk) 17:01, 16 March 2014 (UTC) I′m not bigoted to western weapons , most of my information is derived from English documentary videos which are almost bigoted to their countries,sorry for my weak English I′m Arabian .Tank Designer (talk) 17:11, 16 March 2014 (UTC)[reply]

Which tank? They all have some distinctions, notably: M1A1 Model TGA1500 Lycoming Turbine —71.20.250.51 (talk) 20:22, 16 March 2014 (UTC)[reply]

I meant Diesel Engine tanks as they are the most common tanks but thank you for help . Tank Designer (talk) 20:35, 16 March 2014 (UTC)[reply]

Not Diesel but petrol, but here is the Panther Fibel (unfortunately in German, but a real hoot). --Stephan Schulz (talk) 21:36, 16 March 2014 (UTC)[reply]

Thanks everyone .Tank Designer (talk) 03:36, 17 March 2014 (UTC)[reply]

Here is a maintenance manual for the M1 Abrams. KägeTorä - (^影_虎) (Chin Wag)

Thank you Tank Designer (talk) 10:15, 18 March 2014 (UTC)[reply]

Two Port Network

Are the cell phone charger and laptop charger two port networks.117.194.239.211 (talk) 18:10, 16 March 2014 (UTC)By the way can adapters be regarded as two port network.117.194.239.211 (talk) 18:12, 16 March 2014 (UTC)[reply]

A charger adapter like this has two ports, mains input and dc output, but it is not a linear two port amenable to electrical network analysis. 84.209.89.214 (talk) 22:47, 16 March 2014 (UTC)[reply]

Visual acuity in the human retinal periphery.

Approximation of the acuity of the Human eye, horizontal cross section

I want to get hold of a curve describing how visual acuity changes when a test object moves from the center (fovea) to the periphery. Anybody knows where to get this information?

Thanks, - --AboutFace 22 (talk) 19:15, 16 March 2014 (UTC)[reply]

Something like this graph from Fovea centralis? : [71.20.250.51 (talk) 21:18, 16 March 2014 (UTC)] →[reply]

Thank you, --AboutFace 22 (talk) 21:55, 16 March 2014 (UTC)[reply]

March 17

Do other armies besides the Israeli's also wear Mitznefet?

OsmanRF34 (talk) 01:01, 17 March 2014 (UTC)[reply]

Per Helmet cover "Helmet covers are used by most armies" --Jayron32 02:32, 17 March 2014 (UTC)[reply]

Note however, from what I can tell most don't appear to use anything near as floppy as the Mitznefet, so it really depends on what you mean by a Mitznefet. On the other hand, I'm not sure how strict other armies are at requiring a specific form of helmet cover [10], so it's possible provided it meets other standards and depending on their immediate superiors, some may choose to wear a Mitznefet [11] or something else you may or may not call a Mitznefet e.g. [12]. Nil Einne (talk) 05:56, 17 March 2014 (UTC)[reply]

Cockpit pressurization

One and two-seat combat jet aircraft such as the F-15, F-16, F/A-18, Eurofighter Typhoon and Sukhoi Su-27: Do they have pressurized cockpits? On one hand, their occupants wear oxygen masks, and cabin pressurization would provide unnecessary trauma in an ejection at high altitude. But on the other hand, pressurization helps guard against hypoxia, facilitates maintaining a comfortable cockpit temperature, and helps guard against barotrauma during high-speed climb and descent. Dolphin (t) 06:02, 17 March 2014 (UTC)[reply]

See the F-16.net - General F-16 forum which says of the General Dynamics F-16 Fighting Falcon: "The cockpit pressurization schedule is ambient pressure up to 8,000 feet. Between 8K-23K, cockpit pressure stays at 8K feet. Above 23K, the Environmental Control System(ECS) maintains a 5psi pressure differential between the cockpit and ambient pressure;". According to our Lockheed P-38 Lightning article, experiments with pressurised cockpits for fighter aircraft began during World War II. Alansplodge (talk) 08:56, 17 March 2014 (UTC)[reply]

Thanks Alan. Perfect! Dolphin (t) 11:52, 17 March 2014 (UTC)[reply]

You're most welcome. Alansplodge (talk) 18:57, 17 March 2014 (UTC)[reply]

Further research reveals that the wearing of oxygen masks is required because any decompression of a fast jet's small cockpit would be very rapid indeed and would not give the pilot time to put a mask on. Airliners in contrast, have a huge amount of pressurised air in the cabin, which would take time to leak out, however big the breach. See this article on hypoxia. I have added this to the Cabin pressurization article. Alansplodge (talk) 19:52, 17 March 2014 (UTC)[reply]

It's not just due to differences in cabin volume. There have been survivable incidents involving passenger jets losing very big pieces of cabin wall, which would have been accompanied by virtually instantaneous losses of cabin/cockpit pressure. (cf Aloha Airlines Flight 243, which lost an enormous piece of its cabin roof; or British Airways Flight 5390, which blew out an improperly-installed cockpit window—and half of the captain. Both incidents occurred while the aircraft involved were at altitude.)

Cruising altitudes and service ceilings for passenger jets tend to be significantly lower than for military jets, which makes a significant difference in time of useful consciousness. For example, the service ceiling for the Boeing 777 is 43,100 feet, whereas the ceiling for the F-15 is 65,000 feet. Fighter jets are often operated with a single crewperson onboard; passenger jets have at least two pilots. Further, as you noted in your earlier message, aircraft like the F-16 don't maintain full cabin pressurization (to 8,000 feet, anyway) when the aircraft is at high altitude. Finally, I would suspect that the availability of supplementary oxygen would be more important to military pilots who may be engaged in sustained high-gee manoeuvers not possible for their civilian counterparts. TenOfAllTrades(talk) 16:45, 18 March 2014 (UTC)[reply]

Many thanks. Dolphin (t) 06:15, 18 March 2014 (UTC)[reply]

Body mass index

Is this an accurate measure of body fat? Or can someone who has lots of muscle still show high BMI without being fat?--86.179.250.140 (talk) 15:21, 17 March 2014 (UTC)[reply]

According to this article: BMI. "BMO is particularly inaccurate for people who are fit or athletic".Star Lord - 星王 (talk) 15:25, 17 March 2014 (UTC)[reply]

Cold Fizzy Drinks

Why is it that cold fizzy drinks tend to feel so much more refreshing than non-fizzy drinks? I am sure it's an illusion, too, because I can chug a full bottle of cola, then whilst feeling bloated and burping incessantly for the next ten minutes or so, I still feel thirsty - but not during the process of the actual drinking itself. KägeTorä - (^影_虎) (Chin Wag) 15:38, 17 March 2014 (UTC)[reply]

The aftertaste, maybe? ←Baseball Bugs ^{What's up, Doc?} carrots→ 16:26, 17 March 2014 (UTC)[reply]

I have always assumed it was the carbonation. Flat soda, especially warm, flat sodas, are often very unpleasant. μηδείς (talk) 17:07, 17 March 2014 (UTC)[reply]

A matter of taste as well. Brits supposedly like warm ale. Yuch. Yuch to warm, flat soda as well. But McDonald's Hi-C orange drink is essentially uncarbonated, and it's excellent when served cold. ←Baseball Bugs ^{What's up, Doc?} carrots→ 17:48, 17 March 2014 (UTC)[reply]

Unrefrigerated yes, warm no. Cask ale should be served at cellar temperature which is 12-14 C (54-57 F).[13] It's not carbonated either. A growing number of British drinkers prefer ~~cold~~ chilled fizzy beer in the foreign style - they ask for lager. As you say, there's no accounting for taste. Alansplodge (talk) 18:16, 17 March 2014 (UTC)[reply]

Possible reasons are discussed in a Popular Science article. AndrewWTaylor (talk) 17:43, 17 March 2014 (UTC)[reply]

Please refrain from giving opinions, whether a drink is "more" or "less" refreshing is not something a Reference Desk should be suggesting. I'm deeply shocked this thread hasn't been closed down already. Sorry about that. The Rambling Man (talk) 19:17, 17 March 2014 (UTC)[reply]

I believed there is a valid scientific explanation to this. I like cold water, but I prefer cold fizzy water - I know many people do (this is why it exists). I was just wondering if anyone had any idea why this is so often preferred over normal cold water. Cola was just the example I gave. Andrew's answer above was perfect. Thanks. KägeTorä - (^影_虎) (Chin Wag) 19:40, 17 March 2014 (UTC)[reply]

Agreed, there was no reason to shut down this Q, as that source shows. StuRat (talk) 22:34, 17 March 2014 (UTC)[reply]

Resolved

March 18

The meaning of SMAC

What is the meaning of SMAC when it occurs in a list of blood test. (It's a name of blood test) 194.114.146.227 (talk) 06:39, 18 March 2014 (UTC)[reply]

Sequential Multi-Analysis - Computer, a system of automated multiple blood tests, a little more information at Comprehensive metabolic panel. Richard Avery (talk) 07:23, 18 March 2014 (UTC)[reply]

I bet all the people here who read the title immediately thought about Sid Meir’s Alpha Centauri Diwakark86 (talk) 09:35, 18 March 2014 (UTC)[reply]

Main Battle Tank

When I read the article of AMX-30 tank , I was shocked about its armor , what an 80 mm armor can sustain ? a bullet ? Tank Designer (talk) 10:33, 18 March 2014 (UTC) Maybe the French designers were very concerned about the speed of the tank but does that worth building a tank which can′t sustain anything but bullets ? — Preceding unsigned comment added by Tank Designer (talk • contribs) 10:39, 18 March 2014 (UTC)[reply]

After WWII, tank design philosophy shifted from highly armored heavy tanks to more maneuverable and versatile "main battle tanks." The somewhat newly developed high explosive anti-tank (HEAT) rounds could penetrate enough to negate almost all armor, making heavy tanks virtually useless overnight. So, France and other countries decided to go with the lightly armored, fast MBTs to provide protection. Justin15w (talk) 14:40, 18 March 2014 (UTC)[reply]

Thank you , I was thinking about this point but I was uncertain about it . however your armour is strong . you will find a missile that will penetrate it Tank Designer (talk) 14:55, 18 March 2014 (UTC)[reply]

You're welcome. Nowadays new armor technology such as composite armor, ceramic, etc. provide much more protection than the rolled homogeneous armor used back then. So the MBT has shifted back towards a highly armored (but still maneuverable) MBT. Many countries have switched from HEAT to kinetic energy penetrator rounds so as to better defeat new armor technologies. Justin15w (talk) 15:13, 18 March 2014 (UTC)[reply]

Also kinetic energy penetrators can′t be defeated by hard kill protection systems . Tank Designer (talk) 15:22, 18 March 2014 (UTC) French Tank designers were determined to have the fastest tank in the world even after they used composite armour technology in Leclerc Tank Designer (talk) 15:31, 18 March 2014 (UTC)[reply]

Sucrose solution freezing

When you add some salt or sugar to the water in order to lower its freezing point does it make the resulting ice any less firm? 195.94.247.195 (talk) 10:58, 18 March 2014 (UTC)[reply]

Sea ice has an intragranular porous substructure that consists of submillimeter diameter air bubbles and brine pockets, totaling 4-5 vol.%, arrayed in a plate-like manner parallel to basal planes. [14] Brine inclusions 3 vol.%, typical of first-year sea ice, lower the flow stress by a factor of two [Op. cit.] and increase the quasisteady-state creep rate by about an order of magnitude. 84.209.89.214 (talk) 12:53, 18 March 2014 (UTC)[reply]

However, features of sea ice are not necessarily shared by all salt-water ice. For example, air bubbles may be due to wave action and bacteria and plants below the ice releasing gases. StuRat (talk) 17:15, 18 March 2014 (UTC)[reply]

How do they encase cheese in wax without bad stuff from the wax getting into the cheese?

I saw a wheel of cheese encased like a pill in wax. It looked as though it had been dipped into liquid wax because there was no seam at all. How is this (the encasing) done? I'd think liquid wax, before it had solidified, could seep into the cheese. 75.75.42.89 (talk) 12:00, 18 March 2014 (UTC)[reply]

Dutch Edam cheese is protected by a coat of food-grade paraffin wax E905 which won't hurt you, but whose colour tells a lot about the cheese.

The typical red wax coating denotes a young Edam produced for export. In Holland, the cheese is sold with a yellow wax coating. A black wax coating shows that the cheese has been matured for at least 17 weeks and therefore has a stronger flavour. Other colours of wax coating can be found, for example, a green coating generally indicates that the cheese contains added ingredients such as herbs or garlic. 84.209.89.214 (talk) 13:10, 18 March 2014 (UTC)[reply]

So is it dipped in liquid food-grade paraffin wax or are semisolid sheets wrapped around it with the seams smoothed out or something else? 20.137.2.50 (talk) 13:37, 18 March 2014 (UTC)[reply]

The "food grade" part is key. You could eat the wax, if you wanted, although it would be quite tasteless. Lip balm also often contains such wax, and you obviously will end up consuming some of that, too. StuRat (talk) 13:23, 18 March 2014 (UTC)[reply]

The wax seems to separate easily from the cheese when it is opened. I expect someone here knows the process, but, if not, I can ask at the Hawes Creamery (near my home) where this is done on small Wensleydale cheeses. Dbfirs 12:19, 18 March 2014 (UTC)[reply]

Waxes to cheese are applied by either dipping or brushing. Dipping occurs more frequently in industrial processes, while brushing occurs more often in home or small factories. It's just faster to dip. Justin15w (talk) 16:11, 18 March 2014 (UTC)[reply]

Shelf life of electronics products?

Do modern electronics products have a "shelf life"? By that I mean a time after which a significant percentage (say 10%) of the units of a product will not work properly, even if they have been stored properly and have not been operated. Batteries and electrolytic caps are two things that degrade over time, but what are other ways electronic parts will fail because of old age? Do modern electronics products have a design shelf life? Assuming that they do, what are the design/observed shelf lives of common electronics products like smartphones, flat panel monitors, Wi-Fi routers, and battery-less(?) dongles like the Chromecast? --173.49.82.36 (talk) 12:24, 18 March 2014 (UTC)[reply]

Yes, and it's sometimes intentional. See planned obsolescence#Lifespan-limiting design. InedibleHulk (talk) 13:20, March 18, 2014 (UTC)

I've noticed that LCD TVs and monitors don't last nearly as long as CRTs did (they could last for decades). StuRat (talk) 13:48, 18 March 2014 (UTC)[reply]

I used to throw heavy (for a kid) rocks at those in the dump, and they'd often bounce right back. A Wii controller wouldn't stand a chance. My LCD TV is still flawless since mid-2007. Time will tell. InedibleHulk (talk) 14:41, March 18, 2014 (UTC)

Often part will have a designed life. A switch may be good for 10,000 operations, flash memory is typically good for 100,000 program-erase cycles. Anything which moves, connectors, pots, motor brushes, will have a typical life which you can find in datasheets. They will also have designed limits for operating and storage conditions. Often 0°-70°C. Keeping/using items outside these ranges will shorten life. Some products come in normal and military grades, the latter generally have much wider ranges and cost much more. Other effects might be plastics degrading, and cosmic rays causing problems with memory.--Salix alba (talk): 15:42, 18 March 2014 (UTC)[reply]

We're mixing up terminology here. The term "shelf life" is usually used for food, and it refers to the time that a product remains good if it is stored without being used. That's what the OP is talking about here. It doesn't really have anything to do with planned obsolescence. None of the responses above actually address the question that was asked. (I have no idea what the answer is.) Looie496 (talk) 15:47, 18 March 2014 (UTC)[reply]

Thermal Imaging

does the thermal sight work at day or it only works at night ? why if yes or no ? Tank Designer (talk) 17:28, 18 March 2014 (UTC)[reply]