Wikipedia:Reference desk/Archives/Science/2017 February 20

= February 20 =

Where did electronegativity come from?
Everything I've seen tells me what it is and how it affects chemical bonds, but where did the idea come from? Why did anyone think it was necessary? I read something about energy levels, which makes me think somebody must have measured something, but what did they measure and how did they measure it? Bogwon. — Preceding unsigned comment added by 50.43.36.155 (talk) 03:54, 20 February 2017 (UTC)
 * Our "Electronegativity" article has historical notes and cites for them if you want to learn more. DMacks (talk) 05:12, 20 February 2017 (UTC)
 * While no one doubts the meaning of "positive" applied to numbers (root is Latin positivus), its usage for a particular Electrical polarity seems to have arisen quite arbitrarily, around 1755 according to the etymology reference. That was before the main electrical current carrier, the Electron was found and has lead to generations of students being taught that "Electric current is electrons flowing in the opposite to conventional current direction". It gets worse when we grapple with n-type and p-type doped semiconductors in explaining how Transistors work. Blooteuth (talk) 10:34, 20 February 2017 (UTC)


 * One of the best (and surprisingly easy to follow) books on this subject is The Nature of the Chemical Bond by Linus Pauling. Most of what is taught in a typical first year chemistry class is straight from Pauling's work.  -- Jayron 32 11:44, 20 February 2017 (UTC)

Biology
Hormones — Preceding unsigned comment added by 197.210.44.44 (talk) 15:40, 20 February 2017 (UTC)


 * Hormones. StuRat (talk) 15:44, 20 February 2017 (UTC)

What dangerous in Diesel exhaust fluid to human body?
According to the article (Diesel exhaust fluid) it contains 32.5% urea and 67.5% deionized water. Urea we have naturally in our body, then I think the thing that can damage or interrupt homeostasis is the deionized water. Isn't it? --93.126.88.30 (talk) 16:05, 20 February 2017 (UTC)


 * Just because something is found in the human body, in some concentration, doesn't mean it is safe at any concentration. For example, you probably have some arsenic and uranium atoms in your body. StuRat (talk) 16:10, 20 February 2017 (UTC)


 * To support StuRat's statement, please read The dose makes the poison. Also, understand why urea is in your body.  Urea is toxic, and it's main function is to be a water-soluble way of flushing nitrogen wastes out of your body.  Your body doesn't use it so much as get rid of it as best as it can.  See also Urea cycle.  -- Jayron 32 16:16, 20 February 2017 (UTC)
 * "The dose makes the poison". Diesel exhaust fluid is urea, diluted with water until it is acceptably safe to handle. It is still far from safe. This 1/3rd urea solution is considerably more concentrated than even "strong" human urine (3× - 10×). I believe it's similar to that of some pigs, and pig urine will be familiar to anyone with a farming background. Urea creams are used as a topical skin treatment for some conditions such as psoriasis for their debriding effect. Regularly handling exhaust fluid (i.e. mechanics and fuelling staff, rather than domestic drivers) is known to give rise to dermatitis.
 * The body only contains urea because it's trying to excrete it. Andy Dingley (talk) 16:21, 20 February 2017 (UTC)
 * Does long-term urea touching have a dermatitic effect besides osmosis? Does the bladder, kidney, ureter, prostate and urethra have special urea-resistant cells? Sagittarian Milky Way (talk) 16:29, 20 February 2017 (UTC)
 * Please read the article Urinary bladder and ureter which directly address your question. Urine does not normally come into contact with the prostate gland, which is separated from the urine stream by the valves of the Seminal colliculus.  -- Jayron 32 16:45, 20 February 2017 (UTC)

Multiple infections simultaneously
Is it possible for a human to have multiple infections at the same time caused by different bacteria or virus? For example, maybe a cold from other infected people, a parasitic infection from ingesting contaminated food and another systemic infection (maybe tetanus) from a wound. If this is possible, how would the immune system react to it? Would it cause a major life threatening illness or would it not make much difference? 2A02:C7D:B97E:DF00:C401:C078:9E85:9104 (talk) 22:28, 20 February 2017 (UTC)
 * I have several ancestors who caught the flu during the post-WWI pandemic. The one that died was already suffering from tuberculosis. So, the answer is Yes. ←Baseball Bugs What's up, Doc? carrots→ 23:31, 20 February 2017 (UTC)


 * Each infection the immune system has to fight weakens it, making the individual more susceptible to further illnesses. Remember that HIV doesn't in itself kill you.  It just makes you vastly more open to all the other bugs that surround us.  Rojomoke (talk) 23:48, 20 February 2017 (UTC)


 * I disagree with your first sentence. Many infections cause an immunity to that disease in the future, and potentially to related diseases.  Famously, a mild cowpox infection provides immunity to smallpox. StuRat (talk) 01:01, 21 February 2017 (UTC)


 * We are reading the statement differently. Each infection the immune system has to fight makes the immune system weaker WHILE IT IS FIGHTING AN EXISTING infection. There is a limit to what the immune system can do at any given point in time. So, fighting an infection uses up resources that cannot be used to fight other incoming infections. That is why you shouldn't get a vaccination when you are sick. The vaccination places stress on an already taxed immune system that can cause it to temporarily fail and cause an even worse infection. 209.149.113.5 (talk) 13:15, 21 February 2017 (UTC)


 * Superinfection. Fgf10 (talk) 08:07, 21 February 2017 (UTC)


 * Also related, Opportunistic infection. -- Jayron 32 17:30, 22 February 2017 (UTC)

each person has thousand of micro punctures developing in the vascularisation - every day?
I saw this video (8:20) in which the lecturer say that "every day even in the perfect healthy person, thousand of micro punctures developing in the vascularisation.". Is there any source that supports that claim? 93.126.88.30 (talk) 22:29, 20 February 2017 (UTC)


 * Sounds like a cognate of leaky gut syndrome. StuRat (talk) 20:42, 22 February 2017 (UTC)