Wikipedia:Reference desk/Archives/Science/2014 March 24

= March 24 =

Excess weight being more dangerous for men than for women
Someone previously told me that studies show that excess weight is more dangerous for men than it is for women partly because men store fat around the waist, which squishes the organs, whereas women's bodies are more likely to store fat in the thighs/hip area first. Is this individual's statement in regards to this true/correct/accurate? Futurist110 (talk) 06:54, 24 March 2014 (UTC)


 * This is unlikely to be true. It illustrates a common fallacy - it purports to explain WHY it is more dangerous for men than women to have excess weight, but without demonstrating that it has actually been shown by some sort of scientific rigor. For example, I might say "sharks that spend most of their time in shallow water close to the coast are smaller than sharks that spend most of their time far out to sea because there are fewer small fish close to the coast and so sharks in this area have a poorer diet." Some people might say "Hey, I didn't know that, but it makes sense. Yes, coastal sharks are smaller than their deep-sea cousins." However, nobody should believe what I wrote. (I confess I just fabricated it for the sake of an illustration.) My fallacy is evident because I made no attempt to demonstrate that there is any objective evidence to suggest that coastal sharks are different in size from deep-sea sharks. I merely stated a plausible explanation that might apply if, in fact, it occurs. (I doubt that it does.)
 * So having a plausible explanation as to why excess weight might be more dangerous in men than in women doesn't establish whether or not there is credible evidence either way. We need to learn more about the "studies" rather than about the possible explanation. Dolphin  ( t ) 07:12, 24 March 2014 (UTC)


 * So in other words, this statement can be true, but we can't/don't know for sure without more evidence when it comes to this, correct? Futurist110 (talk) 07:46, 24 March 2014 (UTC)


 * Correct. "Someone previously told me that studies show ..." We need to be very curious about what these studies were, and what factual information they actually showed. The bit about "... partly because men store fat around the waist, which squishes the organs ... etc. etc." is speculation. It is someone's theory about what might be the cause of this health problem. It isn't factual information.
 * Critical thinking requires that we always ask ourselves about what sort of information we are looking at - for example, is it objective information (factual) or subjective (someone's opinion). We should always be very skeptical when we are given little or no objective information, and a much greater amount of subjective information, and then encouraged to believe the underlying premise. Dolphin  ( t ) 12:24, 24 March 2014 (UTC)


 * Also relevant to Dolphin51's discussion is the notion of correlation does not imply causation. Frequently, we get scientific results that show a relationship between two factors (for example, being overweight and premature death in males, just as a possible example).  However, that is different than proving a mechanism to explain the correlation.  Does being overweight cause premature death?  We don't know, because we're not even sure how it might, or how to isolate weight from a plethora of other issues.  For things like this, the literature is usually much better at showing relationships between factors but not so good at explaining how (or even if) factor X leads to result Y.  -- Jayron  32  14:30, 24 March 2014 (UTC)


 * 1) I have heard, from multiple sources, one being Dr. Oz, that belly fat is correlated with more health problems than evenly distributed weight.


 * 2) However, "squishing the organs" is not the mechanism, as I've not heard of people dying from that except as a result of impact injuries.


 * 3) It seems that men tend to have more belly fat than women, but I haven't actually seen any studies proving so.


 * 4) Even if men do have more belly fat, and men have decreased longevity, that doesn't necessarily mean men having more belly fat is the reason. For example, women tend to die more from heart attacks, since they are less able to detect them and get medical help.  So, that would tend to make excess weight (a risk factor for heart disease), more of a danger to women. StuRat (talk) 17:19, 24 March 2014 (UTC)
 * 5)Part of the point of the comments above is that "I've heard" isn't a reference. Your point 4)"For example..." in particular is rather useless without a reference. I don't know anything about this subject, but I know what kinds of claims need reference, especially at a -- reference -- desk. SemanticMantis (talk) 19:33, 24 March 2014 (UTC)

Hmm, organ squishing is otherwise knwon as hypertension leading ultimately to lung and heart failure and stroke and heart attack as possible results, no? μηδείς (talk) 23:01, 25 March 2014 (UTC)

See here:

"There are numerous theories as to the exact cause and mechanism in Type 2 Diabetes. Central obesity is known to predispose individuals for insulin resistance. Abdominal fat is especially active hormonally, secreting a group of hormones called adipokines that may possibly impair glucose tolerance. Insulin resistance is a major feature of Diabetes Mellitus Type 2 (T2DM), and central obesity is correlated with both insulin resistance and T2DM itself.[43][44] Increased adiposity (obesity) raises serum resistin levels,[45][46][47][48] which in turn directly correlate to insulin resistance.[49][50][51][52] Studies have also confirmed a direct correlation between resistin levels and T2DM.[45][53][54][55] And it is waistline adipose tissue (central obesity) which seems to be the foremost type of fat deposits contributing to rising levels of serum resistin.[56][57] Conversely, serum resistin levels have been found to decline with decreased adiposity following medical treatment.[58]"

"There is enough evidence in the scientific community where an impaired non-esterified fatty acid (NEFA) metabolism could give way to the insulin-resistant state of individuals with this type of obesity. Hypertrophy of intra-abdominal adipose cells causes it to be in a hyperlipolytic state in which it is resistant to the antilipolytic effect of insulin. The resulting NEFA flux to the liver causes impairment of liver metabolism which leads to over production of glucose in the liver.[61] Individuals with obesity are more likely to develop weakened non-esterified fatty acid (NEFA), which can weaken the metabolism of the liver causing [62] high glucose production. An individual is at a higher risk of developing ischemic heart disease if they have hyperinsulinemia-dyslipidemia while being abdominal obese.[63] Visceral fat, unlike subcutaneous fat, is implicated in many aging-associated diseases. Surgical removal of visceral fat, but not subcutaneous fat, has been shown to extend the mean and maximum lifespan of rodents.[64][65] Abdominal adipose tissue is a major source of increased inflammatory Interleukin-6 (IL-6) associated with aging.[66] Induction of cellular senescence by visceral fat contributes to the inflammation.[67]"

Count Iblis (talk) 19:23, 24 March 2014 (UTC)

sum of a position wavefunction and its conjugate
Hi all,

I was reading Griffith's Introduction to Quantum Mechanics and came across the claim that if $$\psi(x)$$ satisfies the Time-independent Schrödinger equation then $$\psi(x) + \psi(x)^{*}$$ is a real valued function.

Trying to show this claim highlighted my lack of a definition of what $$\psi(x)^{*}$$ for a wavefunction is. (Up until now it was just "replace all $$i$$'s with $$-i$$'s" (so $$i\sin\left(\frac{ix}{\hbar}\right)e^{-x^2}$$ would have a conjugate of $$-i\sin\left(\frac{-ix}{\hbar}\right)e^{-x^2}$$ but I see now this isn't as rigorous as other definitions.)

My question is what is actually the definition of the conjugate of a (position) wavefunction, does it satisfy the above claim and if so why?

Neuroxic (talk) 10:48, 24 March 2014 (UTC)


 * In this elementary context, a wavefunction is "just a number" (a more rigorous definition would be $$\Psi(x) = \langle x|\psi\rangle$$, where $$\langle x|$$ and $$|\psi\rangle$$ are vectors in Hilbert space). As a complex number, you can write it in the form $$\Psi(x) = Re[\Psi(x)] + i Im[\Psi(x)]$$ (where Re[] and Im[] are real), and so its conjugate would be $$\Psi(x) = Re[\Psi(x)] - i Im[\Psi(x)]$$ as usual. In most cases, simply replacing i with -i does work, and in your particular case, you can see that by using the fact that $$\sin(iy)= i \sinh(y)$$. I don't see why $$\Psi(x)$$ needs to be a solution to the TISE though, since $$z + z^*$$ is always real by definition. -Anagogist (talk) 14:02, 24 March 2014 (UTC)


 * If $$\psi$$ did not satisfy the TISE then it would be function of t as well as x, so it would have to be written as $$\psi(x,t)$$, not as $$\psi(x)$$. Gandalf61 (talk) 16:23, 24 March 2014 (UTC)

The correct question is to show that if $$\psi(x)$$ satisfies the Time-independent Schrödinger equation that then $$\psi(x)$$ can be chosen such that $$\psi(x) = \psi(x)^{*}$$ is a real valued function. Count Iblis (talk) 17:09, 24 March 2014 (UTC)
 * Yes, however for me the rest of the argument was simple provided that $$\psi(x) + \psi(x)^{*}$$ was real. (Well, provided you also take $$\left(\frac{\partial \psi}{\partial x}\right)^{*} = \frac{\partial \psi^{*}}{\partial x}$$ (as you've said below) and a few other things but a definition of $$\psi^{*}$$ would have provided these claims anyway.

Neuroxic (talk) 10:20, 25 March 2014 (UTC)

What you need to do then is to show that if $$\psi(x)$$ is an energy eigenfunction with energy eigenvalue E, then than implies that $$\psi(x)^{*}$$ is also an eigenfunction with eigenvalue E (Hint: take the complex conjugate of the time independent Schrodinger equation and write that in terms of $$\psi(x)^{*}$$, the main issue here is to correctly treat the second derivative term). Count Iblis (talk) 17:42, 24 March 2014 (UTC)

isn't this also true? $$\psi(x)$$ * $$\psi(x)^{*}$$=1. And multiply both sides by $$\psi(x)$$ Voila.--DHeyward (talk) 01:42, 25 March 2014 (UTC)
 * Not quite, the statistical interpretation dictates that $$1=\int_{-\infty}^{\infty}|\psi(x,t)|^{2}dx = \int_{-\infty}^{\infty}\psi(x,t)\psi^{*}(x,t)dx$$, not that $$\psi(x)$$ * $$\psi(x)^{*}$$=1 for any $$x$$

Neuroxic (talk) 10:20, 25 March 2014 (UTC)

Factors affecting pyloric sphincter distension
which factors affect pyloric sphincter distension ? does it include CO2/ carbonated drinks. — Preceding unsigned comment added by 182.185.240.247 (talk) 11:08, 24 March 2014 (UTC)
 * The article Gastric distension does not note any connection with carbonated beverages, but does say that it is commonly caused by air being pumped into the stomach, as caused by CPR. So perhaps...  There's also another article titled Abdominal distension which seems more detailed and may help you in your research.  -- Jayron  32  14:25, 24 March 2014 (UTC)

Erasers
How do pencil erasers work? I was hoping to find a more technical explanation than about.com gives. 2001:18E8:2:28CA:F000:0:0:7A27 (talk) 17:40, 24 March 2014 (UTC)
 * The Eraser article is kind of vague on precisely how it works, but maybe it has some usable references? ←Baseball Bugs What's up, Doc? carrots→ 18:21, 24 March 2014 (UTC)
 * The first reference is in Japanese. The second page is a biography of Joseph Priestley.  The third is something Priestley wrote that doesn't talk about erasers.  The fourth is a Supreme Court of the United States decision about patents.  The fifth is link rot.  The Eraser: How Products are Made link is a search engine, the JSTOR article is about eraser damage to paper (not to pencil marks), and the Goodyear Rubber History talks about Charles Goodyear, not about erasers.  2001:18E8:2:28CA:F000:0:0:7A27 (talk) 19:04, 24 March 2014 (UTC)


 * The "rubber" partially absorbs and abrades the ink or graphite on the surface, and abrades the underlying stained paper as well, the harder you rub. absolution. μηδείς (talk) 19:07, 24 March 2014 (UTC)


 * A pencil eraser is made of a weakly bound polymer material such as rubber or PVC. When rubbed on paper the action is sacrificial: friction force detaches grains of the polymer exposing molecular bonding sites to which graphite pigment particles attach in preference to remaining on the paper. Non-carbon marks such as wax crayons and coloured pencils make tend to smear rather than be erased. 84.209.89.214 (talk) 20:14, 24 March 2014 (UTC)
 * Thank you, since I was hoping for this kind of explanation. Do you mean that a chemical reaction occurs?  If not, what kind of molecular bonding is involved?  2001:18E8:2:28CA:F000:0:0:7A27 (talk) 20:45, 24 March 2014 (UTC)


 * For reference, our general articles relevant to 84's description are adhesion and ablation. SemanticMantis (talk) 21:10, 24 March 2014 (UTC)


 * Wouldn't absorption be more relevant than ablation? In any case, the process is mechanical, not chemical, per se. μηδείς (talk) 23:36, 24 March 2014 (UTC)
 * I meant that the eraser is being ablated (and perhaps a small bit of the paper as well, if one erases vigorously.) I think that the process of graphite sticking to the bits of ablated rubber is Adhesion, but I don't have a ref for that, and didn't want to speculate. I can't rule out Adhesion, at least not from first principles. Do you have any refs for that action or your claim? SemanticMantis (talk) 00:17, 25 March 2014 (UTC)


 * This is rampant speculation, question rather than answer, but I have a suspicion there's some kind of difference between a freshly exposed rubber surface and one which has reacted with air. There are things like Silly Putty that can visibly pull pencil marks off a page on contact, but simply touching the eraser doesn't seem to do anything - until small pieces of it start getting ablated.  While they can wear away the paper, I don't think they always do so, depending on the strength of the paper and force of the rubbing.  And I recall crummy ones that would actually leave a bit of dye their color and a feeling of themselves in the paper rather than taking the paper away. Wnt (talk) 15:39, 25 March 2014 (UTC)


 * Here's a reference ('Everyday Chemistry') that says "Erasers are primarily adsorbents." --Heron (talk) 11:03, 26 March 2014 (UTC)

Filling bubbles
Is it physically possible to produce soap bubble filled with a liquid?

I guess it might require using different liquids like soapsuds and oil. Or could it be not soap at all?

Antibubbles do not count. 91.77.161.202 (talk) 21:19, 24 March 2014 (UTC)


 * Probably not in air, as it would drop like a rock and break apart. However, you can create a "bubble" of one liquid in another, such as oil in water (think lava lamps, although larger spherical bubbles are possible if the fluids are both still). StuRat (talk) 21:35, 24 March 2014 (UTC)


 * See Micelle and Liposome for examples of these liquid-in-liquid bubbles. 24.5.122.13 (talk) 01:36, 25 March 2014 (UTC)