Wikipedia:Reference desk/Archives/Science/2014 April 30

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April 30

Any sources on skin allergies/reactions to vinyl ?

...either inside Wikipedia or outside ? I Googled, but didn't have much luck. StuRat (talk) 03:41, 30 April 2014 (UTC)

@StuRat: [1] (section Vinyl Gloves and Allergic Reactions) may have what you are looking for. Zhaofeng Li [talk... contribs...] 10:29, 30 April 2014 (UTC)

This paper has some info [2]. A key search term is contact dermatitis. SemanticMantis (talk) 15:16, 30 April 2014 (UTC)

Thanks so far. Any more info ? StuRat (talk) 14:07, 1 May 2014 (UTC)

Overtraining

This isn't a request for advice, more of a curiosity. Looking at various sources around the web, I've seen all sorts of recommendations on how long you should wait between exercising - some vague, some very specific. At any rate, most of what I've seen seems somewhat contradictory - some sources claiming that exercising every other day can be counterproductive and that you should only exercise twice a week, other sources claiming that you can exercise every day, etc. Most places do not go into any detail about what counts as "exercise" either - obviously an intense session at a gym using your whole body is going to be different that doing some pushups and situps between commercials. So, I wanted to know, if there were any studies that go into greater detail, or if anyone could give a good explanation of what exactly causes overtraining/what exactly it is. --Again, I'm not looking for medical advice, I haven't been to a gym in years, I just stumbled into the topic and find it rather odd and confusing. Thank you for any assistance:-)Phoenixia1177 (talk) 08:11, 30 April 2014 (UTC)

Basically exercise works by damaging the body, which then needs to be repaired. Where the damage occurs, more muscle cells, blood vessels, etc., are added during the healing process, to prevent future damage when repeating the same exercise. The body will obviously take some time to heal, but how long it takes varies by the amount of damage and other conditions, and also varies by individual. Here focusing on a different part of the body each time a person exercises will help give the previous target more time to heal. If the person's body is sore when they start exercise, then they should probably avoid exercising in that area, so they don't damage it further, until it has time to repair. StuRat (talk) 11:29, 30 April 2014 (UTC)

• It partly depends on the type of exercise, and partly on how intense it is. Top-level athletes train every day, but usually take a break for a couple of days after an event because the exertion is so intense that they need to let the damage heal. There are lots of people who run 5 miles every day, or bicycle 20-30 miles, or walk on a treadmill for an hour, or do Pilates, etc. Looie496 (talk) 13:09, 30 April 2014 (UTC)

Have you looked through the refs at the article you linked? This paper "Definition, Types, Symptoms, Findings, Underlying Mechanisms, and Frequency of Overtraining and Overtraining Syndrome" seems like a decent overview, but it is not freely accessible. [3]. As usual, you can probably get it via WP:REX. SemanticMantis (talk) 15:13, 30 April 2014 (UTC)

It also depends on your age see: [4]. I know the Daily Mail is not the most reliable source but one of the quotes from a cardiovascular surgeon says "As we get older the efficiency with which the heart pumps blood round the body and the way both the heart and the muscles use oxygen in the blood changes and becomes less efficient". And from my own original research I can tell you that when you get into your sixties a bit of damage to a muscle by overworking it can take months to repair. Also see this and this. Richerman (talk) 08:46, 1 May 2014 (UTC)

How is the Electron configuration in other Dimensions???:

How is the Electron configuration in other Dimensions???:

Dimension 2: (THAT must be RIGHT!!!...)

x² [+0]: s₂ - p₂ - d₂ - f₂ (2_s + 4_sp + 6_spd + 8_spdf...) : [ 2-⁴-6-⁴-10-⁶-16-⁶-22-⁸-30-⁸-38...]

Dimension 2: (THAT must be FALSE!!!...)( "Pauli spin -1/2 +1/2 rule...)

x² [+2]: s₂ - p₄ - d₆ - f₈ (2+6+12+20...) : [ 2-⁶-8-⁶-14-¹²-26-¹²-38-²⁰-58-²⁰-78...]

Dimension 3:

x³ [+4]: s₂ - p₆ - d₁₀ - f₁₄ (2_s+8_sp+18_spd+32_spdf...) : [ 2-⁸-10-⁸-18-¹⁸-36-¹⁸-54-³²-86-³²-118...]

Dimension 4:

x⁴ [+6]: s₂ - p₈ - d₁₄ - f₂₀ (2+10+24+44...) : [ 2-¹⁰-12-¹⁰-22-²⁴-46-²⁴-70-⁴⁴-114-⁴⁴-158...]

[ Noble Gases ]

2-2-2 = Helium

8-10-12 = Oxygen-Neon-Magnesium

SPYROU Kosta - Greece - Honeycomp (talk) 14:02, 30 April 2014 (UTC)

There was a Chemistry Olympiad question some years back that asked this question for 2 dimensions; you might like to dig that up. IBE (talk) 02:36, 1 May 2014 (UTC)

SPYROU Kosta: I didn't knew that...I only thought that IF the Physics make calculations in 10 Dimensions... THEN they have to calculate the electron configuration too...(???!!!)... I also ask if the elektron configuration:{s2-p6-d10-f14} says something about our three Dimensional Space???... - Honeycomp (talk) 14:03, 1 May 2014 (UTC)

I'm no expert, but I think it's more likely to be the other way around - the specific shell sizes are a function of their being embedded in three-dimensional space. 3-space has its basic metric and geometric properties whether or not an atom is present, but the properties of the atom are strictly determined by its embedding in the space. When physicists - usually string theorists - speak of 10 or 26 dimensions, they're not proposing that our space is a 3-dimensional hyperplane through a higher-dimensional Euclidean space. Rather, as our article on string theory explains, they suggest that the additional dimensions are very compact - that the possible extension of anything into them is orders of magnitude smaller than even an electron orbital. AlexTiefling (talk) 14:18, 1 May 2014 (UTC)

SPYROU Kosta: THANKs Alex!!! - Honeycomp (talk) 01:10, 2 May 2014 (UTC)

Extracting neutronium from a neutron star

Say there's a neutron star nearby, and we want to extract some neutronium from it. If we wanted to break off a tiny piece of it, would throwing an asteroid at it do anything, or would it be largely unphased? ScienceApe (talk) 14:23, 30 April 2014 (UTC)

It would do very little, both because of the low relative mass of the asteroid and because of the low density. It would be like shooting a cotton ball at a mountain. However, if you could accelerate a Jupiter-sized planet to near light speed, that might do something. But, of course, if you can do that, you can probably make your own neutronium with a lot less effort. StuRat (talk) 16:15, 30 April 2014 (UTC)

If you could, it probably wouldn't stay neutronium long enough for you to use it for any purpose. Once it is taken from the star, and is no longer subject to the extreme pressures that made it neutronium, it would either become free neutrons, or degrade back to protons and electrons. --Jayron32 16:21, 30 April 2014 (UTC)

Big, common misconception: Neutron stars aren't all neutronium. They have a pretty thick crust of other stuff on top of it. I would, however, like to see more about what happens to neutronium as pressure is reduced... I have a feeling there must be some neat surprises. Wnt (talk) 19:45, 30 April 2014 (UTC)

A degenerate neutron gas would be a pretty nasty thing to come across at STP conditions. Radioactive, extremely toxic, highly carcinogenic. Plasmic Physics (talk) 06:08, 1 May 2014 (UTC)

<tl;dr>Think about it that way:

On a high-gravity planet, a spring is compressed by its own weight. Now have Scotty of Star Trek beam it up, into the 1g environment of the USS Enterprise. It will expand immediately and, depenging on the surface g of the planet, jump around more or less violently, possibly killing one of the redshirts in the process. (Big surprise.)

Now, neutron-degenerate matter is extremely elastic. (Contrast electron-degenerate matter, which is "only" completely awesome.)

Worse, one cm³ of neutron-degenerate matter is heavier (or more massive to be precise) than a battleship. If you extract it, it'll not only expand to about that size, but it will do so extremely fast. (A neutron star has an extremely high surface gravity; if you dropped something from a height of 1 cm, it would hit the surface at roughly 150km / 100 miles per second.

So, how fast would your sample expand? After 1cm of expansion (from a radius of ~0.6cm to ~1.6cm), its surface would move at that velocity (think of the spring; it could sustain that kind of pressure on the surface, so it'll exert that pressure when external forces vanish). This is only an order-of-magnitude result, but poor Scotty wouldn't have time to pull one of these if it happened.

Would it continue to expand?

It wouldn't accelerate much beyond that point, but the matter would impact the walls at about 100km/s. And we're looking at a lot of matter, easily outweighing the entire Enterprise.

</tl;dr>Like Jayron32 said, it won't stay degenerate. - ¡Ouch! (^{hurt me} / _{more pain}) 06:57, 6 May 2014 (UTC)

Protein and ingestion

Does this link say that only 20 g of protein is utilized by the body and that too it should be taken for every 4-5 hours and anything other than that will be a waste of protein ? http://www.exercisebiology.com/index.php/site/articles/should_you_eat_protein_every_2-3_hours_for_muscle_growth/ — Preceding unsigned comment added by 119.235.54.187 (talk) 17:28, 30 April 2014 (UTC)

Yes, it seems to say 20 grams of protein at a time is as much as your body can use, however, they only tested with it taken every 2-3 hours, but theorized that an interval twice that long might work, too, as amino acids (the building blocks of protein) remain in the blood after that. Also, taking 20 grams every 2 hours, while awake, would get you to an absurd amount of protein, like 400 grams. That's almost ten times what a normal person needs, and may be too much for your kidneys to process. Myself, I can tell when I've eaten more protein than my body can use, because my urine smells like bacon (which I believe to be amino acids). I don't agree when they say that eating protein every 2-3 hours is inconvenient. Just keep a bag of nuts with you (assuming you're not allergic) and nibble on them all day long. (Make sure they are unsalted, though, or you will get a sodium overdose.) If you find them unpalatable, add in some raisins. StuRat (talk) 19:49, 30 April 2014 (UTC)

@StuRat So if we assume it works for 4-5 hours then it means even 5*20 i.e 120 gms of protein is optimal for our body ?? — Preceding unsigned comment added by 119.235.54.187 (talk) 05:20, 1 May 2014 (UTC)

5x20 = 100, but that's still about twice the amount of protein we normally need. However, a bodybuilder or athlete might need that much. StuRat (talk) 14:05, 1 May 2014 (UTC)

Blended color perception

Based on our discussion earlier on this Desk, it came up that humans are unable to distinguish between an object which reflects the green frequency of light and one which reflects both the blue and yellow frequencies of light. This isn't the case for sound, where we can distinguish a medium frequency from a high and low frequency heard simultaneously. So, do any other animals seem to have the ability to distinguish blended colors ? Do any people have this ability ? If so, how do they describe the difference ? StuRat (talk) 22:02, 30 April 2014 (UTC)

Light perception is the stimulation of certain rods and cones in your retina right? So green light must stimulate the same receptors as yellow and blue light... This is incorrect by the way, yellow and blue PIGMENTS make green, yellow and blue LIGHT make white. Regardless, I get what you mean. We have Trichromatic vision, this is what lets us distinguish the different colors, different light stimulates our three different receptors, which are obviously deficient because 2 different sources of light can stimulate exactly the same proportion of receptors in our eyes. As might have been mentioned before, there is nothing qualitatively different between the colors, they are different frequencies of a continuously varying spectrum. The mantis shrimp has not three, but SIXTEEN photoreceptor pigments, it would no doubt distinguish between green and "yellow and blue", how would it describe it? I guess the same as you would describe the difference between two different colors. Vespine (talk) 22:59, 30 April 2014 (UTC)

Also, in respect to other people, at least one person HAS been confirmed as Tetrachromatic, and possibly it's not extremely rare. However it sounds like this makes a measurable but not extreme difference to their color perception, I don't believe it's like they can perceive a whole new color we don't "know", i think it just means they are able to more easily distinguish between more shades of colors than most people. Vespine (talk) 23:06, 30 April 2014 (UTC)

Actually, functional tetrachromacy has never been validated in a human, though genetically speaking, it is speculated that a tetrachromatic combination of photoreceptors could manifest in a woman, due to variations in a specific allele. However, this would be exceedingly rare and even if that particular combination did exists in the retina itself, there's a high degree of uncertainty that the neurological pathways for color perception within the brain itself would be able to process the additional colors in a way leading to an actual or significant expansion of differentiation between colors. I say uncertain and not impossible because some six or seven years back, a research team genetically modified some mice (naturally dichromats) to be trichromats. They did this with the assumption that they would be confirming that the mice would still be functional dichromats, despite the trichromatic retinas, but to their amazement (and with repercussions to this field of study that are still being weighed today), they discovered they had created true trichromats (these mice, and others in replicated studies) seem to be able to distinguish between colors with near the same level of differentiation found in normal trichromats; the mammalian visual cognition centers are apparently more plastic in this regard than anyone ever suspected. Now, obviously, the fact that this worked with regard to mice moving from the level of dichromat to trichromat does not necessarily mean the principle would hold with humans, or any trichromat, who possesed tetrachromatic retinas, but it is a fascinating area of inquiry. For the record though, the upgrade would not be minor if the neural architecture matched the capabilities of the eye; human vision could go from being able to distinguish roughly one million hues to possibly over 100 million, though this would depend on the specific wavelength of light which the new photoreceptors were sensitive to -- for example, it's worth noting that the theoretical tetracrhomat women who are postulated would actually have a fourth type of photoreceptor that is really not all that far off in the wavelengths detected from that of one of the existing cell types, so the upgrade would be minimal for them, even if the visual centers of their brain were up to the task of processing the information. Snow (talk) 00:04, 1 May 2014 (UTC)

@Snow Rise: you said they tried to change dichromat mice into trichromats, but actually got tetrachromats. Is that what you meant to say ? StuRat (talk) 01:38, 1 May 2014 (UTC)

Wooops, no, it was not. Thanks for the catch, Stu. I've edited the passage above to read as it should have -- that is, that they created trichromats. Sheesh. Snow (talk) 01:49, 1 May 2014 (UTC)

@Snow Rise: Nice try, but you ended up with "tritrachromats". Is that hybrid, or are you editing under the influence ? :-) StuRat (talk) 03:24, 1 May 2014 (UTC)

LOL, yes - of sleep deprivation. Thanks again! Snow (talk) 04:17, 1 May 2014 (UTC)

Also, you claimed functional tetrachromacy has never been validated in a human, but even in the article that I linked it states: In June 2012, after 20 years of study of women with four cones (non-functional tetrachromats), neuroscientist Dr. Gabriele Jordan identified a woman (subject cDa29) who was able to detect a greater variety of colors than trichromatic ones, corresponding with a functional tetrachromat (or true tetrachromat). I had actually heard of this case before looking up the article. Vespine (talk) 04:31, 1 May 2014 (UTC)

Well, I recall that story but to the best of my knowledge the details of that case and the testing procedures were never released to peer-review and were only reported in the general press and I remember my general impression of the details that were released was that they raised more questions as to the verification procedure than they answered. The fact that this case has still not seen review in research literature since then raises further questions as to how verifiable the findings were. That said, Dr. Jordan is known for research in this field. It's possible she did in fact find a functional tetrachromat, but I'd take the claim with a grain of salt until the testing procedure is better validated. I also tend to doubt that, even she did have some increased differentiation, that the subject in this case was seeing a vast new spectrum of colors, as per the question of the ability of the visual modules of the human brain to keep up. Snow (talk) 05:45, 1 May 2014 (UTC)

As a complete aside, why does everyone only ever talk about green as being a mix of yellow and blue, when some greens are obviously a mix of yellow and indigo? RomanSpa (talk) 09:10, 1 May 2014 (UTC)

Problem #1 is that people talk about mixing paint/dyes (which is subtractive mixing) versus mixing light (which is additive mixing). In light, green is a primary color (for trichromat humans) - so you can't get it by mixing anything else. In subtractive mixing, it's usually said to be a mixture of yellow and blue.

Problem #2 is that "blue" is a pretty vague term for most people. The more sciency thing would be to say that in subtractive mixing, green is a mix of yellow and "cyan" (cyan being a pale "sky-blue"). Yellow paint absorbs blue light and reflects red and green. Cyan paint absorbs red light and reflects blue and green. A combination of the two absorbs red and blue and reflects only green. Hence yellow plus cyan makes green.

Pure blue paint would absorb red AND green and reflect only blue light - mixing that with yellow would result in all three primaries being both reflected and absorbed - so the resulting color is likely to be muddy and the exact color you perceive would be sensitively dependent on the dyes and the ratios of the colors and so forth. "Indigo" is another vague color description...it's hard to say what exactly it is...best description is a very dark blue..which would mean that it absorbs some blue light as well as all of the red and green.

Problem #3 is that paint can be laid onto a bright white surface or a dark one - and the consequences for light transmission get really complex. Some light is reflected from the surface of the paint - some passes through the paint, reflects off of the backing material and is then selectively absorbed on the way back out. Since some chemicals in the dye reflect color differently than they transmit it - you can get all sorts of complicated effects by mixing them.

Problem #4 is that when you're mixing light, you have a self-contained system that's easy to describe. With paint and dyes, the color of the incoming light matters. Sunlight is yellowish - and the sky is blue - so you get color changes depending on whether the material is in sunlight or shaded (and therefore lit mostly by blue light from the sky). Interreflections between objects add more complexity - and the fact that our eyes and brain adapt to the prevailing light color and attempt to produce 'perceptual' colors that match what the underlying object's color "should be" if it were not for colored light falling onto it. This mess can get very confused - such as when you view the world lit by old-fashioned orange sodium streetlamps.

SteveBaker (talk) 16:16, 1 May 2014 (UTC)

You can get green light by additive mixing of yellow and cyan light, as you can see from a chromaticity diagram. -- BenRG (talk) 03:44, 3 May 2014 (UTC)

Ah, that might be what's going on: you think indigo is just the same as blue. My father can't tell when something is indigo or not either - you show him something indigo and he just says it's blue. I suppose if other people have this problem (blue/indigo colour-blindness?) it might explain the confusion. (It would also explain why so many people wear clothes that clash horribly with indigo jeans, but that's another story!) If you can't see the difference between blue and indigo I suppose you wouldn't be able to see the difference between yellow-blue and yellow-indigo either. RomanSpa (talk) 05:50, 2 May 2014 (UTC)

Curious. To me, indigo never seemed like a "real" primary color, just something shoehorned into a list of colors of the rainbow. It's not that I can't tell it from blue, but it seems closer to both blue and to violet than cyan seems to blue or to green. I'd think an "indigo-yellow" would just be a slightly blue green, though not as blue as cyan. I wonder if the difference is all semantics or if there's actually a variation in photoreceptor profiles. Wnt (talk) 12:16, 2 May 2014 (UTC)

Without somehow wiring up your eyes to my brain, and vice versa, we probably can't ever know. It's intriguing that you see indigo as closer to blue and violet, though - to me, the difference between blue and indigo (or indigo and violet) is as large as that between yellow and green. It's probably just individual variation. RomanSpa (talk) 18:53, 2 May 2014 (UTC)

Are you sure you're both talking about the same blue and indigo? Are they   and   as shown in Indigo#Classification as a spectral color, or   and   as shown in the respective articles' infoboxes?

Indigo was in fact shoehorned into the list of spectral colors by Isaac Newton for a silly reason, as the article mentions. -- BenRG (talk) 03:44, 3 May 2014 (UTC)

Yea, they list these colors:

Red:  Orange:  Yellow:  Green:  Blue:  Indigo:  Violet: 

But I would classify them differently:

Red:  Orange:  Yellow:  Green:  Cyan:  Blue:  Violet: 

StuRat (talk) 16:28, 3 May 2014 (UTC)

Ah, I see. This was Newton's classification, and is a function of both antiquity and perhaps the variation of medieval English also. But does @RomanSpa: use a definition like that, or the modern one? Wnt (talk) 23:07, 3 May 2014 (UTC)

Gosh, this is still going on! I wouldn't classify either Indigo:  or Blue:  as "indigo", though this may be partly because screens always get things wrong with the blues and indigos and violets anyway. This is closer to indigo:   - it's what the article on indigo calls "electric indigo". According to the article it's in the middle of the "indigo" range, though it doesn't seem like an "average indigo" to me. Annoyingly, the more I think about this the more confused I get, because naming colours is so subjective - think how many shades of green get just vaguely classified together as "green" (I vaguely remember that it's even worse in Japanese, where they count some blues as green too!). RomanSpa (talk) 05:25, 4 May 2014 (UTC)

Now that I see it next to the "violets" above I'm even more of the view that it's not quite right either. The problem is partly that the violets aren't "violet" enough, though this may be an illusion because of the screen. RomanSpa (talk) 05:29, 4 May 2014 (UTC)

Well, all our experience is subjective, though I suppose there's a social science of how people calibrate and recalibrate color. For example, my own experience of indigo was formed from ancient Crayola crayons (though according to the indigo article they've since redefined the color to something none of us would call indigo), included in popular kits presumably for the nearly sole purpose of drawing "proper" rainbows with blue, indigo, and purple, though such look like anything but a proper rainbow. The shade I recollect was somewhere between "midnight blue" and "persian indigo", though I think my modern choice would be to pick pretty much persian indigo directly. Blue, purple, and cyan, however, have all been pretty thoroughly redefined in my mind by RGB monitors. Also, in my mind violet is a "real" color obtained from a prism (and virtually no other source) while purple is a "false" color. I'm not absolutely sure I'd even tell them apart yet I still have the sense that there's something about violet that a monitor cannot duplicate, and that purple is "unstable". But I don't see how to move from all our little anecdotes and stories to anything scientifically informative, or indeed, replicatable by anyone else. And if we really want to get into the craziness of subjectivity... then there's my crank opinion that, because all sensation has pitch and the pitch of something seen is its color, that the beauty of something has a color that is completely distinct from that of the object/person itself. Wnt (talk) 05:15, 5 May 2014 (UTC)

That sort of matches my feeling: violet seems to me very different from purple, but people use the words interchangeably. RomanSpa (talk) 15:05, 5 May 2014 (UTC)

SPYROU Kosta: "they raised more questions as to the verification procedure than they answered" This is the problem by most things!!!... THANK you both for this interesting article!!!... It helped me a lot!!!... - Honeycomp (talk) 23:23, 4 May 2014 (UTC)

"All points bulletin: Be on the lookout for a Stutz Bearcat, burgundy."

Officer Lou: "Hey Chief, isn't that a Stutz Bearcat ?"

Chief Wiggum: "Yea, but it's more of a maroon, really, so keep on looking." StuRat (talk) 21:12, 7 May 2014 (UTC)