Wikipedia:Reference desk/Archives/Science/2017 May 23

= May 23 =

Chemistry - Chloro-amphetamine
Hello, If "Chloro-amphetamine" as well as any of its ortho/meta/para-substitutions are to be called "the CA group". Chemistry speaking, will it also include the chemical "DOC"(2,5-Dimethoxy-4-chloroamphetamine)?

Thanks for the help and sorry for my grammer, Dave. — Preceding unsigned comment added by 79.181.165.55 (talk) 09:32, 23 May 2017 (UTC)


 * I did a quick web search and saw a paper using the term here. Actually the term is "4-CA group", for 4-chlorinated amphetamine derivatives.  Two examples they give there are 4-chloro-N-methylamphetamine (CMA) and 4-chloro-amphetamine (4-CA).  Arguably, 2,5-Dimethoxy-4-chloroamphetamine is also a 4-chlorinated amphetamine, therefore chemically (since that's what you ask) part of the 4-CA group.

That said, putting oxygens on the back end of an amphetamine may chemically be a substitution, but practically, oxygenation is the relevant difference between derivatives of the amino acids phenylalanine, tyrosine, and L-DOPA. It's not that neat to explain here since (like other 4-CA group) it has a chlorine where tyrosine and DOPA have a hydroxyl, and an oxygen at a 2-position that doesn't come up much in nature that I can recall. The archetypal contrast where the aromatic ring is concerned is between meth and MDMA; it can make a difference. Anyway, all this sort of chemical logic is questionable under the best of circumstances - every compound is pretty much its own experiment, and there's no actual guarantee that what happens from a new one will make much sense a priori, not unless you have a structure for every possible catecholamine receptor and can model them all simultaneously, and I doubt if that would work either. Wnt (talk) 18:39, 23 May 2017 (UTC)

Sugar in baked beans
Apparently baked beans make people fart because the sugar in them are not digestible by humans. Does that mean even though a can of baked beans lists it as having 20g of sugar none of that sugar actually enters the blood stream and is all used up by bacteria producing gas in the large intestine? Or do the nutritional values on food packaging only list sugars that can be digested? — Preceding unsigned comment added by 59.44.40.209 (talk) 13:13, 23 May 2017 (UTC)


 * It is not the added sugar, which is in the form of sucrose, glucose, or fructose; all of which are highly digestible. There are different sugars in the beans, specifically sugars such as stachyose and raffinose, which make it to your intestines and make you fart.  These sugars are in the beans themselves, and can make you fart even in applications that don't involve added sugar, such as chili.  -- Jayron 32 13:16, 23 May 2017 (UTC)


 * I remember watching a food-related documentary, Michael Pollan's In Defense of Food, and one section mentions that the indigestible sugars known as dietary fiber are food for the bacteria, which then secrete gaseous waste products, which make you expel flatulence. 140.254.70.33 (talk) 15:13, 23 May 2017 (UTC)


 * Not exactly the same thing, while both dietary fiber and sugars are both carbohydrates, "sugars" are usually taken to be relatively small, either mono-, di-, or tri- saccharides, fiber is a very long-chained polysaccharide. Dietary fiber could also be the source of gas, depending on a person's intestinal flora.  -- Jayron 32 18:46, 23 May 2017 (UTC)
 * So, the term "sugar" refers to relatively simple sugars (mono-, di-, and tri- saccharides), while "fiber" refers to big, indigestible polysaccharides. Also, some sugars can be indigestible. And dietary fiber itself can be a source of gas. This reminds me of an instance when I used the term "benign cancer" and "malignant cancer", and the instructor corrected me that all cancers are malignant, while tumor can be benign or malignant. So, cancer is a subset of tumor. Ay, picky wording. 140.254.70.33 (talk) 13:45, 24 May 2017 (UTC)
 * As to whether those sugars are included on the label, there may not be a universal answer. It may depend on the actual methods and devices used, such as a calorimeters.  According to, there's only 1 g of "sugar" in a 177 g sample, so I have to think they are excluding most of the indigestible sugars. StuRat (talk) 16:15, 23 May 2017 (UTC)


 * "Beans (legumes) cause gas because they contain a type of sugar which is indigestible by our bodies. It’s called oligosaccharide. It’s a large molecule that is different from other sugars in the way our body handles it. It is not absorbed and broken down in the small intestine". WHY DO BEANS MAKE US GASSY AND HOW TO PREVENT IT It's not the same as dietary fibre, although beans have plenty of that. Alansplodge (talk) 11:39, 24 May 2017 (UTC)

Acidity and preservatives
Often, recipes instruct newbie cooks that lemon juice can prevent the discoloration of the avocado or apple. The fruit is still edible, but the ugliness of the color will probably be less appetizing. In regards to acids and bases, can vinegar and very dilute hydrochloric acid work just as well? How acidic does the acid have to be to avoid burning or dissolving the esophagus? What about bases? Can bases be used to preserve foods too? Instead of lemon juice, what happens if sodium bicarbonate is coated on food? 140.254.70.33 (talk) 14:59, 23 May 2017 (UTC)


 * I would avoid using HCl, since, as a major constituent of stomach acid, it smells "like vomit" to most people. StuRat (talk) 15:43, 23 May 2017 (UTC)


 * I highly doubt that. HCl ... well, you shouldn't smell it, but it just has a sharp acid smell.  People scrub concrete with moderately dilute solutions of it.  And when you mix it into anything that is a weak base that can be neutralized, like a food, it will just be chloride ions and a more protonated something.  Many of the pills people take contain HCl to turn drugs to the hydrochloride for isolation; recreational alkaloids like cocaine and morphine also use it. Wnt (talk) 18:43, 23 May 2017 (UTC)


 * For many who have vomited, or been near somebody else who has, that smell is distinctive, especially when mixed with food, and will trigger unpleasant memories. StuRat (talk) 19:49, 23 May 2017 (UTC)
 * That's probably so because the limbic system, which contains the hippocampus and amygdala, is so close to the olfactory nerve. The sense of smell is a good danger detector. 140.254.70.33 (talk) 20:57, 23 May 2017 (UTC)
 * The horrible smell is due to butyric acid. When dairy-product fat breaks up in digestion to yield free fatty acids, you get that substance. HCl has a different smell. Graeme Bartlett (talk) 11:31, 24 May 2017 (UTC)
 * "Can bases be used to preserve foods too?" - yes, see Food_preservation. SemanticMantis (talk) 16:44, 23 May 2017 (UTC)


 * Note that the example of a browning apple isn't bacterial decomposition, but rather oxidation. I don't know if bases would prevent that.  We need a chemist (and I don't mean a pharmacist, for any BrE speakers). StuRat (talk) 16:48, 23 May 2017 (UTC)


 * I just did a web search and found . This looks well written and plausible.  Polyphenol oxidase is indeed the cause of browning - note that polyphenols are a plant compound fairly analogous to melanin - perhaps even homologous, over some vast evolutionary distance, but I don't know any way to prove that.  Plants use polyphenols like insects use melanization, to make a pigment and simultaneously protect against infection.  Oh, anyway, note that it gives primary credit to ascorbic acid, though bringing the enzyme out of its optimal pH range also helps.  Vitamin C is an archetypal antioxidant, and all these polyphenol/melanin processes involve taking aromatic compounds and reacting them with so much oxygen that they turn into a hyper chemically active mess (compare the reactivity of phenol, quinone, etc.) that congeals into an extended polymer.  Wnt (talk) 18:46, 23 May 2017 (UTC)
 * Vitamin E does it also, with the side effect of making you not want to eat the apple slice afterwards. shoy (reactions) 19:23, 24 May 2017 (UTC)
 * Honey contains a small protein that inhibits polyphenol oxidase.10.1021/jf00100a002 Cyanide is also a decent inhibitor (sequesters the copper cofactor), but probably gives an objectionable result if you're aiming for food. Well, unless you're tired of your dinner guests whining about how bad your cooking is. DMacks (talk) 03:39, 26 May 2017 (UTC)
 * Or you're Alan Turing. —Tamfang (talk) 07:52, 26 May 2017 (UTC)


 * Food preparations with lye and other similar bases include lutefisk and nixtamalized maize. -- Jayron 32 18:50, 23 May 2017 (UTC)

History of Allergy Testing in the 20th Century
Can anyone point me in the direction of information about the history of allergy testing. I've looked over Radioallergosorbent test, which was a little bit helpful but not quite enough. Specifically, I'm seeking to verify the feasibly of an allergy test for meats (chicken, lamb, etc.) that was conducted in the late 1950's-early 1960's. What sort of allergy testing technology existed in that time period for food allergies? Thanks! Helene O&#39;Troy - Et In Arcadia Ego Sum (talk) 15:19, 23 May 2017 (UTC)


 * You really don't need any technology. Just feed the person a tiny sample of the item, and see if they react.  If not, give them slightly more, until you get to a normal dosage (meal).  If they still show no reaction, then they aren't allergic to that item.  The "give them a tiny amount" part might need to be even tinier amounts in ancient times, though, due to a lack of medical ways to respond to an allergic reaction. StuRat (talk) 15:46, 23 May 2017 (UTC)


 * This does make sense. However, I'm trying to verify a story about someone "getting a test when I was a teenager" that resulted in a positive allergy to lamb meat. I'm looking for information about what a doctor's procedure would have been in this situation. Helene O&#39;Troy - Et In Arcadia Ego Sum (talk) 16:01, 23 May 2017 (UTC)


 * Try searching for variants on allergen restriction or elimination diet. There were published diet schedules that eliminated possible allergens in a systematic way. I remember seeing one of these a long time ago and, oddly, in the diet schedule I read through, lamb was one of the last things to be eliminated as it was regarded as having low allergenic potential. Odd the things one's brain saves away for a rainy day. 2001:8B0:1625:41F:0:0:0:36 (talk) 23:37, 23 May 2017 (UTC)


 * There a skin test method where samples of the substances in question are adhered to the skin with something like the "dot" bandages, remain there for some time, and any skin reaction is seen as a sign of an allergy. However, I'm not sure this method would catch all food allergies and reactions, such as lactose intolerance.  Skin tests, including pricking the skin, have been around since the 1860's, so a century before your inquiry: .  Note that an allergy to lamb is sufficiently rare that they wouldn't be likely to test for it proactively, but only to verify the problem once somebody becomes ill after eating lamb.  (Personally, if eating item X made me sick, I wouldn't bother with tests to verify this fact, I'd just avoid eating it again.)   StuRat (talk) 16:21, 23 May 2017 (UTC)


 * This is reviewed at skin allergy test. I've heard more argument than usual about the accuracy of these tests, but without doing a lot of research I'm not prepared to summarize it in a neutral way. Wnt (talk) 18:24, 23 May 2017 (UTC)

== Feynman Lectures. Exercises PDF. Exercise 4-14 JPG1JPG2== . . .

There is second solution from MEPhI (earlier date of publication) which says that upper and rightmost logs must replace each other heights to keep potential energy the same before and after the falling. So Θ = 30 °. I have made some drawing https://s.sender.mobi/u/image/2017/5/23/lUnPk5ylV/-.PNG From it, it is clear that angle Θ = 15 °. It is obvious that the 2nd MEPhI solution is wrong, but I can't find a mistake in the 1st one. Why then doesn't my answer coincide?

Username160611000000 (talk) 19:55, 23 May 2017 (UTC)


 * The potential energy solution is what came to mind immediately for me, but there's a catch. If the logs fall you have three logs lined up on the bottom (i.e. the dotted log in the diagram is real).  If we arbitrarily define the center of the corner log as 0 potential energy, then the one next to it has PE = D sin theta * M, where D is the diameter of a log and M is the mass.  But that's present in both configurations and we need speak no more of it.  The dotted log has PE = 2DM sin theta by the same logic.  The top log looking to fall has energy DM sin (theta + 60) = DM sin theta cos 60 + DM cos theta sin 60 = 2DM sin theta at equal potential energy.  Given cos 60 = 1/2 and sin 60 = sqrt(3)/2 then DM sin theta * (2-(1/2) = sqrt(3)/2 DM cos theta, or tan theta = sqrt(3)/(2(3/2)) = 1/sqrt(3), so theta = 30.  It's a great solution, except for one catch, which is that the logs don't actually have to reach their potential energy minimum without jiggling (which is why wise physicists do not climb up into crashed logging trucks to admire the beauty of their equations). Wnt (talk) 20:52, 23 May 2017 (UTC)


 * Looking at your drawing, I think your method would be correct if log B and log D moved equal distances, i.e. if moving B 0.1 mm parallel to AB would move D also 0.1 mm along DC. However, I don't think that's the case, but log D would slide slower than B would. - Lindert (talk) 21:28, 23 May 2017 (UTC)
 * Yep. According drawing if the log D goes 1 unit along its trajectory the log B goes √3 units along its trajectory. So we must choose Θ such that √3 Sin(Θ) = 1 Sin(30 - Θ). Username160611000000 (talk) 04:52, 24 May 2017 (UTC)

Have any planes, ships or train cars had cables to increase stiffness or strength?
Older airliners were aluminum cause steel's too heavy so would steel-cable reinforced aluminum have been viable? Or one of those strong polymer cables/wires like Kevlar? Sagittarian Milky Way (talk) 20:30, 23 May 2017 (UTC)


 * Old biplanes and triplanes relied on cables to hold them together, including Snoopy's favorite, the Sopwith Camel.


 * Older ships used cables to secure some structures. See rigging for sailboat examples.  Here's a later steamship example:  (you may need to zoom in to make out all the cables).  The German battleship Bismarck also had some support cables:.


 * I haven't found any pure locomotive examples, but I can imagine a system that needs to raise and lower components off a rail car using cables. Locomotive-based weapons systems come to mind, but I haven't found any of them using cables to do this, yet.  A train car with it's own crane is a case I did find:, but I'm not sure if that's what you're looking for.  StuRat (talk) 20:36, 23 May 2017 (UTC)


 * Many ancient Egyptian ships were stiffened by one or more cables (though neither steel nor polymer) running lengthwise above the deck, at least according to Björn Landström's interpretation. He shows them used e.g. in a ship from the time of Sahure (3000 BCE), and in ships built 1500 years later by Hatshepsut (likely not in person ;-), both in sea-going ships for an expedition to Punt, and in giant Nile ships used in the transport of obelisks. Egypt never had good timber, so they had to assemble ships from small pieces - ok for compressive loads, but horrible for tensile loads. --Stephan Schulz (talk) 21:37, 23 May 2017 (UTC)


 * Our article says that ancient Greek triremes were stiffened with cables called hypozomata which "would act as a stretched tendon straight down the middle of the hull, and would have prevented hogging". CodeTalker (talk) 01:13, 24 May 2017 (UTC)


 * You may be interested in learning about the principles of tensegrity. Most of the examples thus far are in that vein. I think you may be thinking more in terms of reinforcement like reinforced concrete or ripstop nylon. I don't think I've ever heard of aluminum being reinforced with steel cable in that manner, though I too would be curious to see if anything like that has been tried. SemanticMantis (talk) 01:57, 24 May 2017 (UTC)


 * And some newer aircraft such as the Boeing 787 Dreamliner make extensive use of composite materials, which use things like Kevlar or carbon fiber in a plastic matrix. -Arch dude (talk) 04:50, 24 May 2017 (UTC)


 * Thor Heyerdahl built two ships from papyrus, called Ra and Ra II, hoping to prove that the ancient Egyptians could have sailed to the Americas. When the first one fell to pieces, he added "a tether that acted like a spring to keep the stern high in the water while allowing for flexibility".  Rojomoke (talk) 04:47, 24 May 2017 (UTC)
 * I read the Kontiki book half a century ago, but I think his early 1940's rafts were built of a balsa wood and with a bamboo deck.lashed together with hemp. (If all else fails, smoke the rope). . Later he made rafts of the reeds from which papyrus was made. Edison (talk) 05:15, 24 May 2017 (UTC)
 * Small quibble: Kon-Tiki was 1947, in part using WW2 surplus equipment, and with some of the participants being ex-WW2 fighters. In the early 1940s, much of the world had different priorities.The Ra expeditions were in 1969 and 1970, and while one might argue either way, I think the boats would be offended to be called rafts ;-). --Stephan Schulz (talk) 06:44, 24 May 2017 (UTC)
 * Our Kon-Tiki expedition article says it "was a 1947 journey by raft" the definition being, I think, that a boat has a hull with sides ans gunwales, whereas a raft is just a floating platform.  Alansplodge (talk) 08:53, 24 May 2017 (UTC)
 * Apologies, I see you refereing to the Ra boats. Alansplodge (talk) 08:55, 24 May 2017 (UTC)
 * No harm done ;-). Yes, I was referring to Ra and Ra II. One might argue even in their case, because they still float due to the buoyant material they are made from, not due to a watertight hull. But they certainly look boaty.. --Stephan Schulz (talk) 14:55, 24 May 2017 (UTC)
 * DFEAscenderIIIC01.jpg use cables extensively as part of the structure. Roger (Dodger67) (talk) 07:17, 24 May 2017 (UTC)]]
 * Paragliding is the closest I can think of. The shape of the wing is held in tension.  Parasaiing and parachutes work the same way.  Some older aircraft I beieve had cables from the wing to the fuselage to make sure the force of lift didn't rip the wings off.  --DHeyward (talk) 08:12, 24 May 2017 (UTC)
 * Zeppelin's are usually full with such construction choices. Its not used in modern aircraft design anymore, except in ultralight's. --Kharon (talk) 09:45, 24 May 2017 (UTC)
 * The rigidity of a Zeppelin rigid airships came from an aluminium frame; however, wooden framed airships such as the Schütte-Lanz and Spiess models were far more reliant on steel cable bracing, but had been discarded in favour of the Zeppelin system by the end of WWI. Modern airships, such as the Airlander 10 or Skyship 600 are either non-rigid, being entirely shaped by he internal gas pressure, or semi-rigid, using internal pressure and a hull formed by synthetic materials. Alansplodge (talk) 11:52, 24 May 2017 (UTC)
 * Zeppelin frames only work with cables in between like a bicycle wheel needs spokes. --Kharon (talk) 18:39, 24 May 2017 (UTC)
 * You're quite right, I found this description of the LZ 129 Hindenburg, the ultimate development of the Zeppelin method: "The fifteen main rings of the hull are arranged one behind the other at intervals of 49 feet, thus dividing the hull into sixteen sections, each of which contains a gas-bag. Between every two main rings are two auxiliary rings, all rings being in the form of a polygon of thirty-six sides. The longitudinal members are attached to the corners of the rings, the main rings having truss frame members on the circumference, braced centrally by wires, the intermediate rings having plain triangular members but with no bracing". Alansplodge (talk) 19:11, 24 May 2017 (UTC)