Wikipedia:Reference desk/Archives/Science/2013 April 15

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April 15

The science (if any) of sunglass tints

I understand that glasses can usefully cut UV light (and that visually transparent lenses can do this perfectly well). And I understand that people may wish to reduce glare, to hide their eyes, or even to, uh, look at the world through rose-tinted glasses in order to tint the world rose.

I'm puzzled by the other claims for the benefit of various colors. This PDF from the American Academy of Ophthalmology tells readers that yellow is "optimum for object definition" and that amber "allegedly makes distant objects appear more distinct, especially in snow or haze" (my emphasis).

My understanding of color is very shaky but I do understand (or misunderstand) that filtering of visible light of some waveband may improve perception of light in other wavebands. Thus I suppose one could design a sort of experimental environment in which the definition of objects would be helped by yellow-tinted sunglasses. But in the larger, multicolored world, how could yellow, or any other color, be optimum for the definition of objects in general?

I've tried Googling for this but mostly just get retailers. Of course retailers want to shift product and have an interest in persuading novice anglers, skiers, etc. that experienced/expert anglers, skiers, etc. benefit from a certain tint of sunglasses. What I don't see is evidence or reasoning. Is there anything too this, or is it just old husbands' tales? (I'm guessing that it's more masculine than feminine.) Morenoodles (talk) 09:02, 15 April 2013 (UTC)

The problem with blue is that it seems to be defracted/reflected by everything, such as fog. So, if you block the blue, you can see more clearly in fog. On the other hand, on a perfectly clear day, I don't think it makes much difference. Then there's the negative effect of messing up color perceptions, making traffic lights look wrong, etc. StuRat (talk) 13:30, 15 April 2013 (UTC)

So, do you have any references to support your conclusions, or are you just giving the OP guesses, StuRat? TenOfAllTrades(talk) 14:17, 15 April 2013 (UTC)

What StuRat says are true statements...but you'd have to read a dozen different articles to pull together all of the disparate facts that make it so...hence, I'm not going to dig up all of the article names either! The atmosphere (by virtue of the Raleigh and Mie scattering mechanisms) takes the blue light out of sunlight and scatters it in all directions equally. That means that there is less sharpness to the blue light that we see because it's coming from absolutely everywhere. The problem is much worse at longer distances because the light from distant objects is also being scattered - making the blue part of the light "fuzzy". The complementary color of blue is yellow - and yellow-tinted glasses filter out much of that blue light. The result is a slightly dimmer image with less blue in it. Our eyes are able to adjust to the lesser amount of light coming in - so that effectively boosts our sensitivity to the colors that are not being scattered so badly - which makes everything look sharper - especially in the distance. SteveBaker (talk) 15:09, 15 April 2013 (UTC)

Thanks, Steve. I'm amazed that Ten doesn't know that blue light scatters more. That's the reason the sky is blue, after all, as the blue light coming from the Sun scatters the most, while the reds and yellows scatter far less. StuRat (talk) 17:34, 15 April 2013 (UTC)

No, StuRat's statements are inaccurate and misleading. It is true that atmospheric molecules scatter blue light more than red, due to the strong wavelength dependence of Rayleigh scattering. However, nowhere does StuRat use the word "scattering", and it's not true that objects generally "defract" (diffract?) or reflect blue light. For a fixed aperture size, diffraction has a larger effect for long wavelengths, as you can see from the first equation in the section on single-slit diffraction.

It is also not true that fog preferentially scatters blue light. If that was true, fog would appear bluish, but it's actually white. The theoretical reason for this is that Rayleigh scattering is an approximation of Mie scattering that only works when the scattering particles are much smaller than the wavelengths they scatter. For large particles, like the water droplets that make up fog, Mie scattering is not strongly wavelength dependent. See this link, for example: "Mie scattering is not strongly wavelength dependent and produces the almost white glare around the sun when a lot of particulate material is present in the air. It also gives us the the white light from mist and fog." --128.112.25.104 (talk) 01:09, 16 April 2013 (UTC)

Thank you all for your comments.As there's disagreement, I'm a bit lost. From one understanding of the relevant physics, it does seem that yellow tinting would be beneficial; from another, not. I distrust anecdotal evidence for this kind of thing, in that I imagine that competitive cyclists (for example) use unthinking imitation and hearsay for a lot of their decisions, and then come up with anecdotes and evidence to support these decisions. I wonder if there have been empirical tests for the value (or not) of tints for perception of distance, objects, etc. Morenoodles (talk) 05:53, 17 April 2013 (UTC)

To be clear, I don't think we are disagreeing that yellow lenses improve distance vision. There are details about fog and haze that are complicated...but overall, it's clear that these things should work, and for sound scientific reasons. User:128.112.25.104's comments are only about foggy conditions - we know that blue light is scattered by the atmosphere because that is why the sky is blue. SteveBaker (talk) 15:12, 17 April 2013 (UTC)

Blood Circulation

HI! I'm just studying about Blood Circulation and I need some clarification. 1. Why do RBC's pile up in blood vessels during blood circulation and what this process is called? 2. What is Haemocytometer? 3. What is Microcystic Anaemia? Please help me in clarifying my doubts. 114.79.141.44 (talk) 10:43, 15 April 2013 (UTC)

"Pile up" is a rather vague term, but you might find our articles on coagulation, hemocytometer and microcytic anemia helpful. Gandalf61 (talk) 11:01, 15 April 2013 (UTC)

Most populous species

Which is the most populous species in terms of total world population? Bacteria are not a single species. Human population is 7 billion. Which species has a world population that exceeds 7 billion? --Yoglti (talk) 12:12, 15 April 2013 (UTC)

Have a look here [1] for a good discussion on exactly your question. The answer seems to be krill, btw. Aaadddaaammm (talk) 12:40, 15 April 2013 (UTC)

Sorry, krill are probably the most abundant animal. I'd guess that pretty much any bacteria beats them. Some back of the envelope calculations: total bacterial cells on earth = 5x10^30 [2]. Number of bacteria species: more than 10 million (largest estimate) [3]. Let's say 10 billion to give the microbiologists some breathing room. Then the most abundant bacteria has at least 5x10^30/10 billion = 500 quintillion cells! This beats krill by 500 quitillion / 500 trillion = 1 million times. Wooo! Aaadddaaammm (talk) 12:50, 15 April 2013 (UTC)

(ec) It's estimated that there are 350 trillion krill out there. You might think that they win because of that - but not even close!

Consider that some species of cyanobacteria can double their population size in 6 hours...given enough space and nutrient, a single bacterium can produce:

• 2 bacteria in 6 hours.
• 65,000 in 3 days.
• 4 million in 5 days.
• 270 million in a week.
• ...and exceed the number of humans in just 9 days.

We don't stand a chance.

In a cup of yogurt, in your refrigerator, there are at least three billion bacteria per milliliter...although not from a single species. But if you killed all of the bacteria in a 10 gallon barrel of yogurt - then added one cyanobacterium and waited, then in a bit less than two weeks, they'd outnumber all of the krill on the entire planet by a comfortable margin.

Consider this - there are 10 trillion "good" bacteria in the gut of every single human being. Of those, about 50% come from just five species. So there are roughly 5% of each of those major species...which means that there are at least 500 billion bacteria of just one species in your gut right now. Our gut bacteria have the krill outnumbered by just the amount in the guts of a moderate sized football arena full of people.

So I don't know what the answer is - but it's not krill or humans...it's got to be some kind of bacterium or other uni-cellular organism.

...unless we decide to say that viruses are "alive" because if we count them, then the bacteria will be outnumbered to a crazily high degree.

SteveBaker (talk) 15:00, 15 April 2013 (UTC)

This is no kind of direct answer, but the query reminded me of a possibly apocryphal story: when asked what the study of nature could tell us about the Creator, J.B.S. Haldane supposedly replied only that one could conclude that He had, "an inordinate fondness for beetles." --Mr.98 (talk) 17:44, 15 April 2013 (UTC)

See "Lists of organisms by population".—Wavelength (talk) 17:52, 15 April 2013 (UTC)

What is the most populous macroscopic species other than humans? --Yoglti (talk) 00:34, 16 April 2013 (UTC)

What do you consider macroscopic? wiktionary:macroscopic says "Visible to the unassisted eye." Krill and insects are visible. And do you include plant species? Some of those are quite large and frequent in forests. PrimeHunter (talk) 01:35, 16 April 2013 (UTC)

Did you read the link or comment I posted above? Euphausia superba is the answer to your question. There are 500 trillion and they are visible to the naked eye (grow up to 6 cm). Aaadddaaammm (talk) 09:07, 16 April 2013 (UTC)

D-mannose

This substance works by letting E-Coli bacteria to attach to D-mannose and be "escorted" out of the body. The reliable sources about how it functions can be found on the WP:MEDRS discussion.

My question is, is that mechanism of action is absolutely unique? Is there any medicine on the market or in the development that works not by killing bacteria, but rather by allowing bacteria to attach to it? Thank you.

P.S. I'm asking this question, because it's a very interesting mechanism of action that may not result in bacteria resistance. Ryanspir (talk) 14:54, 15 April 2013 (UTC)

(1) Not unique - for example, proanthocyanidins in cranberry juice are thought to have a similar effect. In addition, the Tamm-Horsfall protein may inhibit uropathogens in the same way.

(2) Resistance to this mechanism was described at least 30 years ago (PMID 6105132). This is not surprising - adhesion mechanisms are quite mutable. -- Scray (talk) 20:26, 15 April 2013 (UTC)

Cranberry is not a medicine. My question relates "if there is any medicine..".

2) Thanks for correction. I meant to say evolving resistance. Ryanspir (talk) 13:53, 17 April 2013 (UTC)

quassia amara L. against glucose

In Brazil they use the tea of quassia amara-L to control the glucose. Do you know it? — Preceding unsigned comment added by 151.62.28.190 (talk) 15:07, 15 April 2013 (UTC)

Our article on quassia amara doesn't discuss that use, but there is a small amount of scientific literature on the topic, for example PMID 21480415. Looie496 (talk) 15:40, 15 April 2013 (UTC)

Searching on PubMed I found one article from a university in Uttar Pradesh. [4] They report lower glucose levels in rats and higher glucose tolerance. Another from Argentina seems focused on "preventing self-medication" to avoid what are apparently very rare risks (if only 15 adverse effects could be found in a pharmacovigilance program for this and two other herbs). [5] Unfortunately both of these are in obscure journals unlikely to be found at a local library. The degree to which research into herbal treatments has been neglected is just unbelievable, and often as not the emphasis of research seems to be toward spiking a competitor before there's any chance for benefit to be observed. Wnt (talk) 21:42, 16 April 2013 (UTC)

It's quite difficult to do rigorous research on herbal treatments unless there is a known active ingredient. Without that, there's no way of knowing whether doses prepared at different times and places are equivalent. That doesn't make it impossible, but it greatly increases the challenges. Looie496 (talk) 06:13, 17 April 2013 (UTC)

I don't agree at all! Most of biochemistry was worked out by people doing experiments with stuff like "fraction VII" and observing interesting effects, and none of those were pure compounds. Wnt (talk) 15:06, 17 April 2013 (UTC)

EKG words

Hey there, I have a question about the ElektroKardioGrama, the question is: Why Dr Willem Einthoven has used in the words p-q-r-s-t for the graph, precisely? what was his meaning in these words just (and not another like ABCDE)? מוטיבציה (talk) 15:24, 15 April 2013 (UTC)

From our article here, "Originally, four deflections were noted, but after the mathematical correction for artifacts introduced by early amplifiers, a fifth deflection was discovered. Einthoven chose the letters P, Q, R, S, and T to identify the tracing which was superimposed over the uncorrected labeled A, B, C, and D. [6]". That reference discusses your question quite thoroughly, let us know if you don't have access. Aaadddaaammm (talk) 15:31, 15 April 2013 (UTC)

Thank you, I have not paid attention to that. מוטיבציה (talk) 20:06, 15 April 2013 (UTC)

What is muscle stiffness and how does massage work?

What exactly is actually happening when we have stiff muscles? Wikipedia redirects to DOMS, which I don't mean (or maybe I do but I don't realize). I am talking about the stiffness which occurs after long periods of holding the same position, after sleep, or due to disuse of a muscle. How does massage help in anyway? Many of my friends have their joints cracked and muscles massaged, yet when I read wikipedia many of these treatments are treated as pseudoscience. What does massage actually do? 137.224.239.102 (talk) 17:09, 15 April 2013 (UTC)

I'm not sure the literature provides solid answers, but I'll give you my own thoughts. I believe there are at least three things going on: (1) overuse of muscles causes swelling, which means entry of fluid into the tissues, and massage moves some of the fluid around; (2) muscle tissue is full of sticky proteins and has a strong tendency to form glue-like adhesions -- massage breaks up the adhesions; (3) massage activates stretch receptors in the muscles and thereby causes effects on the nervous system. There is certainly a lot of pseudoscience in the field of massage therapy, and people sometimes overreact against it, but it doesn't seem to me that there is much doubt that basic massage is genuinely helpful for sore muscles. Looie496 (talk) 17:27, 15 April 2013 (UTC)

It might be as simple as temperature. That is, if you are in a cold environment, and haven't used your muscles recently, they may be below the ideal operating temperature (more so on muscles in the arms and legs than on the torso). All chemical reactions are highly dependent on temperature, and that includes those which cause our nerves to fire and muscles to contract. A massage might raise the temperature just enough, by friction and increased blood flow, to make them work properly. StuRat (talk) 17:26, 15 April 2013 (UTC)

I'm a fully trained Swedish masseuse. Muscle stiffness and soreness after exercise is due to a build up of lactic acid in the tissues, which a good sports massage will help to break down so that it can be eliminated: soreness can also be due to small tears in muscles. Massage aims to increase blood flow to tissues so that healing can occur quicker than if left. The sort of stiffness that occurs after a period of inactivity is different as there is no lactic acid to break down. I believe the problem lies in the shortening of certain muscle fibres and tendons which occurs in these circumstances. There is another problem which is that lymph is secreted constantly and circulates around the body - but has no pumping system of its own: it relies on muscle movement and the pumping of the blood around the body to promote the movement of lymph. If the body stays in one place for a long time, lymph gathers in much the same way as water does and tissues swell. Manual lymphatic drainage is one massage technique which gives some relief to people who suffer lymphoedema: other techniques involve strapping and compression. --TammyMoet (talk) 17:51, 15 April 2013 (UTC)

"seabrid" ?

What does the word "seabrid" mean? It is an adjective to refer to the morphology of leaves. --İnfoCan (talk) 17:17, 15 April 2013 (UTC)

I'm pretty sure that's a misspelling of "scabrid", which means slightly rough to the touch. Looie496 (talk) 17:35, 15 April 2013 (UTC)

advanced directives

when do you start implementing advanced directive? — Preceding unsigned comment added by Ucclemm (talk • contribs) 19:06, 15 April 2013 (UTC)

See Advance health care directive. The precise circumstances when it becomes active will depend on jurisdiction and the wording of the document, but it's basically when the patient lacks capacity to make (or communicate) decisions regarding his or her treatment. Tevildo (talk) 19:51, 15 April 2013 (UTC)

a book of blood tests (or with another medical laboratory tests)

Hello, I'm looking for two things, and I would like to get a help for that. The things are: 1. a book which includes the best matter about the blood tests (or tests of laboratory at all, but only medical tests -of course). This book should be with clear information about' like how is each tests made in laboratory, and what is the normal levels of the results etc. (Of course, It's very important to me that this book will be the most recent) 2. website that includes much as possible of the above. — Preceding unsigned comment added by מוטיבציה (talk • contribs) 21:18, 15 April 2013 (UTC)

Searching for "laboratory reference manual" will provide a lot of informative lists, like this one. Searching for "laboratory procedure manual" is less rewarding, but there may be some useful hits. -- Scray (talk) 23:59, 16 April 2013 (UTC)

Buffer Zone

What is a buffer zone? I've heard of a buffer capacity, but not of a buffer zone. On a graph, where is the buffer zone located?

Thank you.

--Jethro B 22:46, 15 April 2013 (UTC)

I normally hear the term buffer zone in a geographic or general sense, like "administrative assistants create a buffer zone between the executives and the public". Did you want it's meaning in a chemistry context ? I know you can add acids or bases to a buffered solution, up to the buffer capacity, before the pH changes substantially. Perhaps they are also calling this the buffer zone. StuRat (talk) 23:28, 15 April 2013 (UTC)

StuRat is correct in regard to buffered solutions. See http://uccpbank.k12hsn.org/courses/APBioI/course%20files/assignments/chapter2homework05.html. However, the term buffer zone has a more general use in graphs: It can be used to describe any straight line or approximate straight line portion of a graph between 2 points of inflexion, outside of which the graph slopes or curves quite differently, there being different processes happening on either side of the buffer zone. Ratbone 124.178.59.243 (talk) 00:03, 16 April 2013 (UTC)

The buffer zone is the region of the titration curve where the Henderson-Hasselbach equation applies. It is any point in the titration where both parts of a conjugate acid/base pair are present; for example where you have HC₂H₃O₂ molecules and C₂H₃O₂^1- ions in the same solution. --Jayron32 00:10, 16 April 2013 (UTC)

Thank you. Not a fan of the Henderson-Hasselbach equation. I prefer using the buffer equation, then using the [H+] value or [OH-] value to calculate the pH. But whatever you prefer! So you're saying it'd be the part of the titration curve from the beginning when the conjugate acid or base is added (mL>0), until the equivalence point (since past the equivalence point, you're just adding excess acid or excess base)? --Jethro B 01:25, 16 April 2013 (UTC)

Bingo. --Jayron32 04:49, 16 April 2013 (UTC)

The Great Apes

Hello, here's my question. If raised as an exotic pet, which would prove to be the least agressive and risky of the two: a bonobo, or an orangutan? — Preceding unsigned comment added by JadeGuardian (talk • contribs) 23:00, 15 April 2013 (UTC)

You might have a different problem with bonobos, when they try to mate with everything in sight. StuRat (talk) 23:32, 15 April 2013 (UTC)

Lol, that's what I thought. Maybe a tufted capuchin will do... --JadeGuardian (talk) 23:44, 15 April 2013 (UTC)

First, let's be very clear. Great apes make horrible pets, and there are serious ethical objections. Apes are today illegally poached from their native habitat, and they continue to rapidly approach extinction. Wildlife_trade just makes them go extinct faster. Read the articles. Here's some specific reasons, for orangs: ([7]) and for bonobos: ([8]). In fact, many people think that apes are persons, see Great_ape_personhood. Even if one could navigate (or criminally ignore) the financial and legal (CITES) hurdles of owning an ape, they would still make terrible pets. Now that that's out of the way, I'll note that some single wild animals can successfully be kept by amateurs, but they tend to be species that are not naturally gregarious or social. This is simply because it would be necessary to provide for dozens of animals to maintain any semblance of natural conditions. Make of that what you will. SemanticMantis (talk) 23:45, 15 April 2013 (UTC)

Oh, no, I'm just as much for animal rights as anyone, that was just more of a hypothetical question. I'm not looking for a pet or anything... --JadeGuardian (talk) 23:48, 15 April 2013 (UTC)

Hypothetically, either could become sexually aggressive towards humans, and be sold off as a research subject for experiments that would be unethical if performed on humans. Not so hypothetically, see the sad history of Oliver_(chimpanzee). The article recounts "Janet Berger herself claimed that Oliver was becoming attracted to her when he reached the age of 16.[4] He mounted her and tried to mate with her. After he tried it several times it became apparent that Oliver was a threat to Janet, and had to be sold." SemanticMantis (talk) 00:01, 16 April 2013 (UTC)

I don't think SemanticMantis has it correct. His cited references are about it being ethically wrong to acquire and keep primates as pets, not about whether they would make good pets once you've got one. Dogs are both gregarious and social - and millions of single dogs are kept as pets and companions by millions of individuals and families. However dogs have three important charecteristics built in: they assign their human master the role of Leader (the alpha male or alpha female), they instinctively want to help and protect both alphas and puppies (they seems to identify children as human puppies), and they are quite intelligent but not TOO intelligent. In addition, humans look and smell so different to dogs that I suspect that dogs just don't see humans in the least bit sexually attractive. These characteristics are not present in anywhare near the same degree in orangatangs and bonobos. One should also note the "randy teenager" phenomenon. We once got a male kitten and a female puppy at the same time. They played together and slept together and got on really well. The dog's growth rate way outstripped the kitten's, but that didn't seem to matter. One day though, when the cat got to it's equivalent to the human teenager years, it tried to have sex with the dog. (I assume that a dog makes, for a cat, a right uggly cat, but that cat was horny. It took a while to figure out what to do, but managed it) The dog made it VERY clear that penetration was not acceptable, and from then on their relationship was much cooler. It ended completely when the dog, now 10x the size of the cat, accidentally knocked the cat flying. One supects that if the cat was 10x the size of the dog, the dog would have had a very sorry life indeed, raped and beaten repeatedly. Wickwack 120.145.63.92 (talk) 00:43, 16 April 2013 (UTC)

Thanks Wickwack, I realize what I wrote was unclear. I thought about dogs and cats while I wrote, quite a bit. But I stand by what I said: dogs and cats are domesticated animals, not wild animals; thousands of years of artificial selection result in a number of behavioral changes. Even "as fast as possible" is ~12 generations, in the case of the dedicated Russian fox domestication experiment). So we can't really expect a wild animal to behave towards humans like a domestic animal might. It is true that sometimes a social instinct can be co-opted in favour of the humans, and it was likely a role in the domestication of dogs (e.g. Domestication_of_the_dog#Promise_of_food.2Fself-domestication). But I would still advise against a single wild wolf kept as a "pet," and I think my link to Oliver the chimp provides an example of "whether they would make good pets once you've got one." SemanticMantis (talk) 01:14, 16 April 2013 (UTC)

Ah! You have a point I overlooked - a very long period of domestication breeding undesirable characteristics out and desirable characteristics in. A wild dog native to Australia is the dingo. Keeping them has been illegal, and whether or not they make good pets is controversial. Many people have done so succesfully though, claiming they have a personality quite similar to dogs. Small numbers of Australians have kept kangaroos - a somewhat gregarious social animal with no history of domestication. Also quite physically capable of killing a human. My cousin had a pet kangaroo and always claimed it was good loving pet, but more difficult to house train than a dog. They have plenty of photos of roo and children cuddled up together. It's really only satisfactory if you have plenty of land area, which my cousin had (10 acres). We once had a neighbour who had a red kangaroo (they grow as high as a man and are downright dangerous in the wild) without any problems, except that it liked to go on long runs and could jump any fence - you need tolerant neighbours. Roos are cheap to keep as they get their own food (Grass and leaves. If you have any nice flowers in the garden, they eat them. If you catch them in the act and say sternly "Bad Roo!", they hop 3 or 4 m away and look at you as though you are weird). Wickwack 124.182.145.187 (talk) 01:48, 16 April 2013 (UTC)

Read The Murders in the Rue Morgue. Looie496 (talk) 23:54, 15 April 2013 (UTC)

Not a bonobo or an orangutan, but Project_Nim_(film) is an excellent doco. The impression that I got was that after a certain size / age, any of the apes become too unpredictable to be safe. I listened to a podcast recently with a primatologist, who did say that unlike all the other apes, a bonobo has never been observed to kill another bonobo, and they exhibit behavior that appears like remorse. In one particular case a bonobo would cower in the presence of a researcher whose finger it had "accidentally" bit off.. Not really comforting IMHO  :) Vespine (talk) 00:36, 16 April 2013 (UTC)

Bonobos will also happily tear monkeys apart and eat them! (see a recent question with a link). I realize now I've gone on way to much on this question, so I'm out now :) SemanticMantis (talk) 01:19, 16 April 2013 (UTC)

Just curious OP, why not gorilla?165.212.189.187 (talk) 12:54, 16 April 2013 (UTC)

I suggest that OP not to jump in at the sallow end. Instead start with a 3.5 day old Homo sapien (I use that phrase kindly – Neanderthal would be more descriptive). Note: Disregard the fact that they don't come with any reliably User Manual!!! Yet, after just the first 35 years, the OP will be ready to take on, not only Bono's and Orang-utans but realise and avoid, all those things that, that un-motherly control-freak Ellen Ripley did wrong. Also Jane Goodall's books are a very good read. --Aspro (talk) 19:47, 17 April 2013 (UTC)

Yes, young humans don't make good pets, for just the reasons I alluded to above: Especially when they become teenagers, they are just too darn independent, they assert their own will, and, dammit, they are most often smarter than their parents. Very well portrayed in Zits (http://en.wikipedia.org/wiki/Zits) Wickwack 120.145.20.216 (talk) 01:13, 18 April 2013 (UTC)