Wikipedia:Reference desk/Archives/Science/2015 January 29

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January 29

What is the simplest fatty acid?

184.59.104.40 (talk) 01:23, 29 January 2015 (UTC)

We don't normally answer homework questions. However, we do have excellent articles on fatty acids and on carboxylic acids in general. I suggest you read them, and, if you have any further questions, please ask them here. Dr Dima (talk) 01:46, 29 January 2015 (UTC)

Body Odour

Do children aged 3/4 have body odours? The disgusting smell that puts others off? -- (Russell.mo (talk) 07:28, 29 January 2015 (UTC))

Here are some links that may help you research the answer to your question. --Jayron32 10:46, 29 January 2015 (UTC)

One source of a foul odor is young children is phenylketonuria. StuRat (talk) 13:44, 29 January 2015 (UTC)

I don't trust any other links rather than Wikipedia's and Wikipdians. Body Odour article stated about 'puberty', 'ovulation', diseases, and lifestyle related things. I'm curious whether a general scent is available in children, especially the arm pit smell. -- (Russell.mo (talk) 15:20, 29 January 2015 (UTC))

If you don't trust anything except Wikipedia, I'm not sure what we can do for you. I've provided you with lots of reading material on the matter, if you can't be bothered to read it, then there's nothing else anyone here can do for you. You already know how to find the Wikipedia article on the subject, and note that the Wikipedia article does not answer your problem. I provided additional sources, and you said you can't be bothered to read through them to find information you can trust. Good luck and vaya con dios... --Jayron32 15:24, 29 January 2015 (UTC)

I said 'I don't trust any other links rather than Wikipedia's and Wikipdians'. I didn't say, "I can't be bothered to read through the information (help) you provided". Another reason behind this is, I have to attribute the links appropriately, in most cases they don't allow to retrieve information from their site... Anyways, thank you for your help. -- (Russell.mo (talk) 15:37, 29 January 2015 (UTC))

I don't really understand what you mean "I have to attribute the links appropriately, in most cases they don't allow to retrieve information from their site". If you mean you're writing this for somewhere and need to cite sources, be aware that many things will not accept even wikipedia itself as a good source, and definitely very few will accept something some random wikipedian said as a source. And any thing which is so loose with their sourcing requirements that they do accept stuff some random wikipedian said would likely accept most of those as sources too and it shouldn't be that hard to work out how to cite them (and you could always ask if you really have problems.). If you mean you have problems accessing other sources, some explaination of this when asking the question, would help a great deal. Most of the links in the Google search result are just to ordinary web resources like help sites, and also some forums and other such stuff. They aren't to journal articles or anything likely to behind a paywall. And they also don't seem to be particularly controversial. So you'd need to be behind a very, very restrictive internet connection if you can't access them. Nil Einne (talk) 17:37, 29 January 2015 (UTC)

The OP is difficult to understand, but I think he means "I only trust external links provided to me in Wikipedia articles or by Wikipedians here, as opposed to those I find in a Google search". StuRat (talk) 17:41, 29 January 2015 (UTC)

OR and not quite what the OP was asking, but children of that age have natural non-pathogenic body odours which they do not find offensive and by which they can recognise each other. This ability tend to be abandoned early because of social pressure from adults. Dbfirs 18:51, 29 January 2015 (UTC)

That seemed to be said in the OP's first point. Since they said it was "another reason", I presume the second was intended to cover a different reason. Nil Einne (talk) 19:18, 29 January 2015 (UTC)

@Nil Einne, StuRat, and Dbfirs: Ammm, you baffled me Nil Einne! Anyways, I'm on 'pay kilobyte as you go' price plan, the only price plan available in this country. Its almost the end of the month, I'm on about less than 250 Mb, I got to cover it till to 7th of next month (unsure). Wikipedia is my school/college/university, the only website that doesn't take megabytes as you enter... Other websites (some/most) restrict picking information off of their website; whatever I've come across so far, whenever I tried to retrieve... What put me off of looking at other websites... A Wikipedian taught me a golden rule, still they advised to provide the links of the websites I collect information off, and whatever I've put my finger on, so far, is a copyrighted material, which does not allow me to copy my way even if I provide their link in my work. I only trust Wikipedia's articles (I don't have a choice). Its like an e-Bible to me. The ones who help me all the time or the 'Reference desk', its like angelic desk for me, where angels assist me (lol)! Of course demons are available, but I have not come across any yet. You guys might have since you (and most, even WP) thinks WP is not a reliable source

Hello Dbfirs, think of it as children sitting in 'airtight dry atmospheric room', obviously they will sweat and smell. I understand the armpit smell which may begin in puberty, what can I use to explain 'the airtight dry atmospheric rooms children smell'? How can I say, "The body odour, the scent of human being (children) was unpleasant because of ________________________________?"

You give me jokes Stu..lol Do my words/sentences/paragraphs seriously come across like a 'broken type writer' work? I do put my heart into making sense of my words/sentences/paragraphs you know, not joking at all...

Thanks for offering the helping hand Nil (like some)

(Russell.mo (talk) 20:38, 29 January 2015 (UTC))

It was a bit hard to understand which links you trust and which you don't. Back to the question, I recently had the misfortune to sit next to a young kid in a restaurant, who smelled like mildew. It might have been his clothes or coat. Then again, if he used a towel full of mildew, say to dry his hair, then he might smell that way, too. I blame his parents for not washing his clothes or towel with bleach, to kill the mildew. StuRat (talk) 04:08, 30 January 2015 (UTC)

Could use it; I was expecting a general word that will provide the understanding of the complete dry indoor suffocating environment. Thanks though -- (Russell.mo (talk) 17:53, 30 January 2015 (UTC))

Name that med

I saw a TV ad recently for a med, and I didn't catch the name of the med or what it was for. It causes increased urination, and one of the side effects is urinary tract infections, since the urine contains more sugar than normal. (Perhaps it was to treat diabetes ?) Anyone know the name ? I would like to read Wikipedia's article, if we have one, or an outside source, otherwise. StuRat (talk) 13:41, 29 January 2015 (UTC)

• There's a new drug for diabetes that does that, Invokana, it makes you pee out glucose. There's a whole new class of these drugs. μηδείς (talk) 17:45, 29 January 2015 (UTC)

• Yep, that's it. Thanks ! StuRat (talk) 18:03, 29 January 2015 (UTC)

• See Category:SGLT2 inhibitors for Wikipedia articles all of them. -- Ed (Edgar181) 21:39, 29 January 2015 (UTC)

Resolved

Is formic acid a fatty acid?

This is mostly an issue of nomenclature, but the question above about fatty acids got me a bit confused. Fatty acid says "fatty acid a carboxylic acid with a long aliphatic tail" (emphasis mine). But formic acid shows up in Short-chain_fatty_acid, as it has "aliphatic tails of less than six carbons". So, I suppose a "tail" with zero carbons is also a tail with less than six carbons (and apparently a zero-length tail is aliphatic), but it seems odd or wrong to say that formic acid has a "long aliphatic tail." "Fatty acid" does not appear on the formic acid article. I would hope that all short-chain fatty acids are indeed fatty acids. Acetic acid actually seems to imply that it is not a fatty acid (in the biochemsistry section), but at least it has one whole carbon on the "tail", that seems to qualify as truly aliphatic... I can see making the call either way, but I'm curious of what the actual usage is. If the usage is slightly contradictory, or different definitions require different tail lengths, that's fine too. Additionally, does anyone think that perhaps the list at short-chain fatty acids should be changed (or amended and clarified)?

Thanks, SemanticMantis talk) 16:02, 29 January 2015 (UTC)

I don't know if there is any "official" definition of a fatty acid; IUPAC, generally considered the authority on chemical nomenclature, has a vague definition here: http://goldbook.iupac.org/F02330.html.

Having worked in chemistry for 20 years, I can confidently say that no chemist would ever describe formic acid as a fatty acid. I would definitely support removing formic and acetic acids from any list of fatty acids, even short chain fatty acids. Propionic acid should probably go too. -- Ed (Edgar181) 21:35, 29 January 2015 (UTC)

Thank you! That is what I expected; I have posted on the talk page for short-chain fatty acid with a link back to here [1]. If I don't get any feedback within a few days I will remove formic and acetic acid from the list at the short-chain article. SemanticMantis (talk) 21:58, 29 January 2015 (UTC)

@Edgar181 and SemanticMantis: Nonetheless, there are many such uses in PubMed ( http://www.ncbi.nlm.nih.gov/pubmed/?term=%22short+chain+fatty+acids%22+%22formic%22 ) [2][3][4] etc. One thing about biology (and the "fat" in fatty acids makes people assert this as under its province) is that anyone writing a paper or giving a lecture can get up and define a term like "fatty acid" in the way that pleases him best for purposes of his work, and there's nothing you can do about it. :) Though there's no fat in the short chain fatty acid, there actually is some sense in it though, in the sense that a fatty acid minus two carbons = a fatty acid. Wnt (talk) 04:04, 30 January 2015 (UTC)

Yeah, that's not too surprising either, thanks. I don't really care one way or the other, but I think our articles could represent the multiple definitions/aribitrariness a little better. Maybe I'll just put an asterisk in the article, explaining that inclusion of some acids as "fatty acids" is context-dependent. SemanticMantis (talk) 14:44, 30 January 2015 (UTC)

Surely there has to be some name for "saturated monocarboxylic acid where everything else is a hydrocarbon", doesn't there? Just like methane is a paraffin even though you can't make wax out if it? Formic, acetic, propionic, butyric, valeric, caproic — you can't make fats out of all of them, but they're all the same class, and if they're not "fatty acids", what are you going to call them? --Trovatore (talk) 15:19, 30 January 2015 (UTC)

Not all groupings or categories have special single-word names though, right? What's wrong with "saturated monocarboxylic acid"? Are those compounds often discussed as a group? I mean, we don't have a special word for finite alternating groups with an even number of elements either, but we can just describe them if we want to single them out. SemanticMantis (talk) 15:59, 30 January 2015 (UTC)

Well, I think traditionally they have been discussed systematically. You have the paraffins, their alcohols, their aldehydes, their acids. They make a nice rubric. I think this is the way it was done in my dad's chem texts, anyway (from the forties). Fashion may have changed since then for all I know. --Trovatore (talk) 17:30, 30 January 2015 (UTC)

By definition, lipids are biomolecules more soluble in non-polar solvents than water (that is, they are hydrophobic. Small-chain carboxylic acids are decidedly hydrophilic. If I am not mistaken, the largest carboxylic acid which is soluble in water to any reasonable degree is valeric acid; that provides what is probably a reasonable limit for the size of "fatty" acids (given that "fats" are hydrophobic). --Jayron32 04:59, 31 January 2015 (UTC)

I am certainly not claiming that formic acid is in any ordinary sense "fatty". However, I do believe it is part of a systematic grouping that has traditionally been called the "fatty acids", if only for want of a better name. --Trovatore (talk) 06:23, 31 January 2015 (UTC)

Fat may be hydrophobic, but I don't think of that as its defining feature. If I were to make up a definition from scratch, I would say it depends on whether the molecule is a substrate for beta oxidation. At least in the textbook instance, this would exclude propionic acid, acetic acid, and formic acid, but not valeric acid. However, one could just as logically define it according to products of beta oxidation, in which case the former two would still be within the definition. But that's all really quite arbitrary, and of course we're not actually supposed to make up an answer. :) Wnt (talk) 13:09, 31 January 2015 (UTC)

Perhaps you should think less, than, if you think it isn't the defining feature. See here. A selection of definitions "Lipid - any of a class of organic compounds that are fatty acids or their derivatives and are insoluble in water but soluble in organic solvents.", "Lipid - "Any of a large group of organic compounds that are oily to the touch and insoluble in water", "A lipid is chemically defined as a substance that is insoluble in water and soluble in alcohol, ether, and chloroform." , "Lipid - any of a group of organic compounds consisting of the fats and other substances of similar properties: they are insoluble in water, soluble in fat solvents and ..." So, before you go one with what you think, perhaps you should actually read and cite references which tell you what you should think. The defining characteristic of all lipids (including subclasses of lipids like fats and fatty acids) is hydrophobicity. --Jayron32 21:16, 31 January 2015 (UTC)

@Jayron32: I started off with references; you're the one who started the diversion into logical arguments. But people can write dictionaries however they want, and they don't have to be logically consistent either. Valeric acid, which you established as water-soluble as our article says, is described by Merriam-Webster as "any of four isomeric fatty acids C5H10O2 or a mixture of these" Indeed, they describe propionic acid the same way. [5] But not acetic acid. Which proves what, I'm not sure, but when article writing you can use this as a reference for something. (However, I don't dispute that "lipid" is hydrophobic because it was generally defined in terms of what you can isolate by extracting the hydrophobic components of a cell. Lipid, fat, and fatty acid may all have different meanings.) Wnt (talk) 22:16, 31 January 2015 (UTC)

People can write dictionaries however they want, but at least they are reliable according to Wikipedia's standards. It's OK to provide references which support a certain view. It isn't OK to discount other references which support a view you don't like, as you do here. Look, valeric acid and propionic acid, and acetic and formic can all be fatty acids if they want to be. And if they don't wish to be fatty acids, I'm not going to object either. But as I've been trying to say all along, the definition is not clear-cut and simple: there is no hard-and-fast line for carboxylic acids which says that some of them are fatty acids and some are not. The entire set of them is a homologous series, and their properties vary gradually and continuously, with no clear dividing line. My only point is that: There is no clear line, but we at least can point to what are long-standing and well-accepted, and well referenced definitions of "fat" "lipid" and "fatty acid" and let the reader decide for themselves. I don't know what your goal is, but my goal is to provide as many different perspectives as possible and let people understand the complexity and subtlety of such definitions, not to call others wrong. --Jayron32 01:38, 1 February 2015 (UTC)

I don't really understand how this became an argument. To me saying "all fatty acids have to qualify as lipids" and "all substrates for beta oxidation have to be counted as fatty acids" are two equally reasonable and at the moment equally unsourced assertions. P.S. Though I don't know this exists, it's at least theoretically possible to have a triglyceride in which one of the three chains is a short chain fatty acid, even formic acid, which nonetheless could be soluble in organic solvents rather than water. Wnt (talk) 13:30, 1 February 2015 (UTC)

IUCN Red List for plants

The IUCN Red List article makes it sound as if plants are rated. Lots of animal species have their Red List status near the top of the infobox (see Pygmy hippopotamus for an example), but I'm not seeing a comparable thing in plant articles, whether common things like tomato, somewhat-known things like deadly nightshade, or rare things like Galium divaricatum. Is this simply an editorial decision (i.e. it was decided not to give Red List information for plants), or is this because the rankings given for animals somehow aren't available and/or aren't relevant for plants? Nyttend (talk) 17:36, 29 January 2015 (UTC)

The Red List lists plants, you can read about it on their web site [6]. (As an aside, I can't get their search feature to work - is it just me or is the site broken?)

Here's a some random plant articles I found that do have conservation status in the taxobox - Asplenium_bifrons, Aschisma_kansanum. So we know that the taxobox can take conservation status data, just like animals can.

So I'm not sure why more plants don't have status listed. I don't think it's due to either of your suggestions. In popular culture, threatened plants get way less attention than endangered animals. Many endangered animals don't even get much attention - we hear about Charismatic_megafauna, but much less so endangered mosquitoes. There are also very few plants considered Flagship_species. So it might just be unintentional animal bias creeping in. We do have pages like IUCN_Red_List_data_deficient_species_(Plantae) IUCN_Red_List_vulnerable_species_(Plantae), and a few other similar lists (that really should be cross-linked under "see also," IMO). Maybe there's a drive at Wikipedia:WikiProject_Biology to rectify this, or perhaps we could start one :) SemanticMantis (talk) 18:04, 29 January 2015 (UTC)

I've added notices at Wikipedia talk:WikiProject Biology and Wikipedia talk:WikiProject Tree of Life asking participants to go to Template talk:Taxobox, where I've proposed adding a maintenance category to all taxoboxes that don't mention IUCN Red List status. The point's to identify articles where we haven't addressed Red List status; it's not meant for Data Deficient and any other status (if there are any?) where we can't supply information, since I'm trying to identify ones where Wikipedia effort, not scholarly effort, is missing. Nyttend (talk) 18:21, 29 January 2015 (UTC)

WP:PLANTS would probably be the best place to add a note. I always assumed that most plants aren't rated - after all, someone has to do the work to rate a species. And sort out the nomenclature. Since it's pretty much impossible to generate a list of all plant species, I can't see how anyone can rate all of them. Guettarda (talk) 05:06, 31 January 2015 (UTC)

History of ocean going ships late 1800s - early 1900s

Does anyone know where I could find some systematic information on the history of ocean going ships during the late 1800s to the early 1900s, say roughly 1880 to 1930? I am primarily interested in knowing how the characteristics of ocean going vessels evolved during this time in terms of parameters such as size, weight, speed, means of propulsion, and choice of construction materials (e.g. metal / wood). Ideally, I would be looking for something that talks about the characteristics of the mean (or median, etc.) ship over time. However, given the difficulties in obtaining good data from that era, I would take whatever I can get. In broad strokes, at the very least, I'd like to be able to say whether this was either A) a period of very little change in ship construction, B) a period of rapid innovation in ship construction, or C) something in between. Dragons flight (talk) 21:02, 29 January 2015 (UTC)

I cannot point to what you want, though I'm sure it exists in a Jane' Ships or Lloyds list sort of way. I can give you Turbinia, Dreadnought and Ship gun fire-control system which all yell B. --Tagishsimon (talk) 21:25, 29 January 2015 (UTC)

Age of sail indicates refinement and development - "between 1850 and the early 1900s when sailing vessels reached their peak of size and complexity," but the ref for that sentence has link rotted. SemanticMantis (talk) 21:50, 29 January 2015 (UTC)

Matthew Turner (shipbuilder) should give you an idea about innovations in design in ocean going sailing vessels for some of that period, at least in the Pacific. Mikenorton (talk) 22:00, 29 January 2015 (UTC)

Are you interested in ships in general, in military ships, or in civilian ships? My go-to book is Björn Landström's The Ship. The field saw massive development during the period you mention. HMS Devastation (1871) launched in 1871, the first modern turreted warship without backup sails. HMS Royal Sovereign in 1891 had 1.5 times the tonnage, twice the crew complement, and was build from streel, not iron. 1906 saw HMS Dreadnought, "obsoleting all existing battleships at the time", with 2.5 times the firepower of the latest Pre-dreadnoughts and turbines instead of reciprocating steam engines. Dreadnought was itself obsolete by the time of WW1, which saw the Queen Elizabeth-class battleship, bigger, better, and switching from coal to oil as the main fuel. The next major steps were geared turbines, and then radar. In 1930, arguably the decline of the battleship had begun, with aircraft carriers and U-boats taking over. --Stephan Schulz (talk) 22:39, 29 January 2015 (UTC)

Specifically I care about ships that were used in the systematic collection of weather data. That includes both military and civilian vessels, but probably skews more towards the civilian side in terms of numbers. Dragons flight (talk) 01:55, 30 January 2015 (UTC)

NOAA History - Tools of the Trade (Ships) has lots of information dating back to NOAA's predecessor Federal agency, the United States Survey of the Coast. You might also find U.S. Coast Guard and Navy history websites worthwhile. Systematic large-scale weather collection, however, is very new - it really took its present scientific form after the rise of aviation and probably didn't standardize until circa World War II. More on that: Weather Technology. Bit of Meteorological History (which has extensive information on the 19th and early 20th century) suggests that in the Civil War era and Reconstruction era, the Smithsonian Institute collected weather information, including maritime and seacoast data, for the Federal government. You can buy historical ship plans from SI: $20 just for the catalog - so those won't be cheap, but they probably rank among the most thorough historical resource available for a large number of vessels. The Navy also has historical records of every vessel ever contracted, with particularly thorough records for 1892 to 1945. NARA has extensive maritime records, including the Lighthouse Service and weather archives.

One tidbit at the Navy's website got to me: they have a free book-length guide called Professional Readings in U.S. Navy History, which is the introduction to the vast research resources available; and they recommend you visit various offices in person to talk to historians. In other words, you might go far by asking a real historian - rather than just talking to a bunch of scientists who are interested in history. Nimur (talk) 07:11, 30 January 2015 (UTC)

That's the most interesting period of development for battleships, a great introduction is the DK Brown book "Warrior to Dreadnought". It's also when Froude got to grips with hull shapes. Greglocock (talk) 00:53, 30 January 2015 (UTC)