Wikipedia:Reference desk/Archives/Science/2015 December 31

= December 31 =

What is the programming language in which vineyard bots program is written?
Moved to Reference_desk/ComputingDenidi (talk) 02:18, 31 December 2015 (UTC)

Pre-natal genetic screening and rare diseases
How precise are pre-natal genetic screenings for detecting uncommon genetic anomalies? --Denidi (talk) 02:29, 31 December 2015 (UTC)
 * I am aware of three commonly used prenatal genetic tests: Chorionic villus sampling, Amniocentesis and Percutaneous umbilical cord blood sampling. These tests serve different purposes but importantly they are not completely risk free, most people go through pregnancy without having any of these tests. There are many other non invasive screens and tests which are used first, such as Nuchal scan. Invasive tests are typically only used when there is another reason to suspect an increased risk of the test picking something up. Vespine (talk) 22:23, 3 January 2016 (UTC)

Year-round averaged air quality score
I'm looking for a comprehensive air quality score that:

1. Is a weighted average of all the relevant air pollutants: PM2.5, PM10, NO2, SO2, CO

2. Is averaged over a long period (at least a year) so that it takes the seasonal variations into consideration

Is there such a thing?

aqicn.org gives very detailed real-time air quality statistics, but it doesn't give you one comprehensive number, nor does it give you a number that averaged over an entire year. 731Butai (talk) 10:14, 31 December 2015 (UTC)


 * 1) Weighted how ? Which pollutants would get what weights ? StuRat (talk) 02:24, 1 January 2016 (UTC)


 * Based on how dangerous each pollutant is, with respect to each other. If let's say 10 μg/m^3 of PM2.5 is X times more damaging than 10 μg/m^3 of PM10, then PM2.5 would be weighted X times heavier than PM10. 731Butai (talk) 04:32, 1 January 2016 (UTC)


 * The problem with that approach is that your comparing apples and oranges. One may trigger asthma attacks, another may be a carcinogen, another may stink, and another contributes to global warming.  So, how do you decide which is worse  ? StuRat (talk) 04:45, 2 January 2016 (UTC)


 * The standard practice is typically to generate an air quality index score from each individual pollutant (sometimes referred to as a component score) on an hourly or daily basis based on the relative hazard. For example, 55 ug/m^3 of PM10 is scored the same as 12 ug/m^3 of PM2.5 in the US EPA approach (both getting an index score of 50).  The overall AQI score is then simply reported as the highest component score.  Weekly / monthly / annual scores are then typically the average of the resulting hourly or daily scores.  Implicitly that assumes there is no compounding effects of having multiple pollutants.  In reality, we know that isn't true, but for the most part we don't have enough understanding of the impact of air pollution to adjust for the interactions of pollutants of different types.  It is also worth noting that different governments and national organizations have different scoring schemes so air quality index values reported by different organizations often aren't comparable (AQICN approximately uses the US EPA approach).  In many cases, agencies also report the annual average concentration of each pollutant.  Those averages, are often a simpler way of making comparisons than looking at index values.  So, the short version is that we don't really have a weighted annual score that mixes everything together.  Dragons flight (talk) 11:06, 1 January 2016 (UTC)
 * Wow, thank you very much for the detailed answer! 731Butai (talk) 09:56, 3 January 2016 (UTC)

E as a chemical element symbol
Not every single letter is used as a chemical symbol. I've always wondered why there are some letters that can appear as the first of a 2-letter chemical element symbol, but don't appear as a single letter on the periodic table. Any complete list??


 * A = argon until 1957 (now the symbol is Ar)
 * B = boron
 * C = carbon
 * D = deuterium (not a special element, but a hydrogen isotope with one neutron as opposed to the usual no neutrons

But how about E?? Georgia guy (talk) 14:56, 31 December 2015 (UTC)
 * It was proposed einsteinium, but IUPAC changed it to Es.
 * Continuing your list from symbol (chemistry):
 * E = proposed for einsteinium in 1955 (now Es); generic element; electrophile
 * F = fluorine
 * G = glucinium = beryllium (now Be)
 * H = hydrogen
 * I = iodine
 * J = iodine (for German Jod; now I)
 * K = potassium
 * L = generic ligand
 * M = muriaticum = chlorine (now Cl). Also currently used for a generic metal.
 * N = nitrogen
 * O = oxygen
 * P = phosphorus
 * Q = (never got used for anything AFAIK)
 * R = rhodium (now Rh). Also currently used for unspecified groups.
 * S = sulfur
 * T = tritium (an isotope of hydrogen)
 * U = uranium
 * V = vanadium
 * W = tungsten
 * X = xenon IIRC (now Xe); also a generic halogen
 * Y = yttrium
 * Z = generic element
 * Θ (Greek theta) = thorium (now Th; suggested by the Marks brothers, but nobody cared or cares)
 * Double sharp (talk) 15:12, 31 December 2015 (UTC)
 * E or E+ appear in mechanistic organic chemistry as generic electrophiles. L is often used as a symbol for a generic ligand.  EdChem (talk) 15:18, 31 December 2015 (UTC)
 * X can be a generic halogen, as in hydrohalic acids = HX and haloalkanes = RX. E can be a generic element, as can Z.  EdChem (talk) 15:24, 31 December 2015 (UTC)
 * You're absolutely right, of course. I must have been thinking of just elements. I've added these in italics. Double sharp (talk) 15:59, 31 December 2015 (UTC)

Mineral identification
I have a specimen piece of a mineral that I can't identify. It is brown, not of uniform colour, and there are on its surface, fibrous fan-like structures which are pale beige in colour. Do any of you have any ideas as to what it might be? --TammyMoet (talk) 17:59, 31 December 2015 (UTC)


 * This question of identification begins essentially "Is this Animal, Vegetable, Mineral or conceivably a combination of two of the above i.e. a Fossil". AllBestFaith (talk) 18:53, 31 December 2015 (UTC)


 * "Fan-like structures" sounds like a plant fossil, maybe a fern ? Can you provide a pic ?  The brown color makes me think of sandstone, but of course there are many other possibilities.StuRat (talk) 19:18, 31 December 2015 (UTC)

Not a plant fossil, the fibres are slightly raised from the surface and they form a section of a circle. I shall try and upload a pic tomorrow but I'm not the best photographer! --TammyMoet (talk) 20:47, 31 December 2015 (UTC)

Think I've found it - it's very similar to this photo of wavellite: http://www.mindat.org/photo-25382.html --TammyMoet (talk) 21:12, 31 December 2015 (UTC)
 * WHAOE see Wavellite which gives no credence to your crystal mineral's alleged metaphysical attributes: "Aids in the direction of one's life journey. Meditate with Wavellite, then after meditation, ask your question - what direction or choices are before you? Also aids in proper energy flow. During the new moon, it can increase intuitive abilities and inner knowledge." AllBestFaith (talk) 23:43, 31 December 2015 (UTC)
 * So tell me do, where did you get any connection with the metaphysical qualities of Wavellite in this question? Did I mention it? Did anyone else? All I wanted to know for was to see if those fibres were asbestos and therefore hazardous to health, and also in case I wanted to resell it. --TammyMoet (talk) 12:33, 1 January 2016 (UTC)
 * Happy New Year! Answers: Google search/No/The self-styled "most extensive website of crystals and minerals in the world" says this. But even there nobody had the metaphysical ability of Clairvoyance to deduce from your question your pecuniary motivation, nor apprehension of Asbestosis which has proven groundless. You have not been charged for our help. AllBestFaith (talk) 18:23, 1 January 2016 (UTC)
 * I only asked a straightforward question and expected a straightforward answer. So why answer a question I didn't ask then? I suppose I should call DNFTT here. --TammyMoet (talk) 13:44, 2 January 2016 (UTC)
 * No, after your main question you asked 3 further questions that received answers, followed by a fourth question that I shall leave ignored. AllBestFaith (talk) 20:12, 2 January 2016 (UTC)

separating L-DOPA from dopamine
How would I go about doing this? I am pretty experienced with acid-base extraction (as a chemistry major) -- but now I have a real life situation and I don't want to mess it up. I have 37 wt% HCl and sodium hydroxide powder, a a measuring flask and microbalance, but let's assume I work out the titration and create standard solutions. My concern is still that there are acidic groups on both L-DOPA and dopamine (the catechol groups) -- they're just not as acidic. Also, I'm not sure which hydroxy group on the ring will be removed first. My organic solvent is dichloromethane.

The initial situation is L-DOPA + dopamine sitting in dichloromethane (basic conditions). I'm assuming this mixture also acts as a buffer. Practically, could I bring the pH down to the pI of the L-DOPA without overshooting past the pKa of the amino group of the L-DOPA (or the COOH group of the dopamine)? I'm having a hard time predicting the pH / equivalent chart of this system, especially as it could be biphasic (DCM + water).

Also is there a convenient way to separate L-DOPA, dopamine and tyrosine? This is not as important, just a theoretical concern at the moment. Yanping Nora Soong (talk) 19:22, 31 December 2015 (UTC)


 * Ms. Song (assuming respectfully that that's you last name), you should be aware that by our guidelines, at the top of this page, we do not answer homework questions. It's three decades since I took Organic Chem Lab, but I know there are standard answers to these questions.  Can you give the context of the question?  If you do have questions with homework we will help. μηδείς (talk) 03:48, 1 January 2016 (UTC)


 * However, if this is a real life situation then you need to be ready to do much more thorough research than a few random people here are going to give. If you're trying, say, to invent some kind of nutritional supplement, you do not want to cause some kind of Showa Denko tryptophan disaster!  My impression of dopamine solutions is that they tend to want to go the way of melanin at least a little all on their own - they're not that stable (I think there was light sensitivity involved) and I don't know what the resulting compounds will do.  The best thing to do is probably to go to PubMed, go to PubChem, Google Scholar, let's not forget Sci-Hub when you know what paper you want and are having access troubles...  try to find people doing work that is closest to whatever you have in mind, try to get a protocol and advice from them directly.  Budget also matters - I see several sources about chromatography like  but I don't know it's an option.  But there's a big difference between giving references as an intellectual exercise and making a recommendation for a real life attempt, and we shouldn't gloss it over ... and our guidelines actually do warn we shouldn't give such advice ... and if given, Wikipedia accepts no liability for what goes wrong. Wnt (talk) 01:09, 2 January 2016 (UTC)


 * I think the answer will depend on the reason for doing it. Are you trying to quantify the amounts of the two substances, or are you trying to separate them in order to use one or the other? Looie496 (talk) 15:59, 2 January 2016 (UTC)


 * This is a simpler version of a more complicated problem I am solving (amino acid derivatives with an oxidation-sensitive aromatic side chain) -- dopamine and L-DOPA are simpler (catecholic) analogs for questions to avoid confusion. In this case, I am testing out the alpha-amino acid decarboxylation reaction in described here. In this case, L-DOPA would represent the starting material that did not decarboxylate, while the dopamine would represent the desired product to extract. Yanping Nora Soong (talk) 09:06, 3 January 2016 (UTC)
 * This is problematic since the difference in pKas may be different for the real system. But for DOPA  I have 2.3, 8.7, 9.7, 13.4 ; for dopamine a key pKa is apparently 8.93 but I'm missing the others.  Anyway, I assume that the pKa of a carboxylic acid is the least, i.e. the 2.3 figure - though this value seems lower than one might typically expect, it is not unusual for amino acids - which would seem to indicate the general feasibility of extracting the hydrochloride at quite acidic pH, provided it doesn't decompose or react - especially in the case where you want to throw away the carboxylic acid and keep what stays neutral overall, as you can wash repeatedly with some sort of polar solvent... provided it doesn't dissolve too much of the zwitterion anyway, which I would not guarantee (after all, patients *eat* DOPA ...).  I haven't looked at this sort of chemistry in a while, and didn't learn it all that well to start, I'm afraid... there are a lot of tricks like using tartrate in purification that I don't really understand well ... I know I liked the notion of chromatography better, if only because it is so straightforward. Wnt (talk) 16:42, 4 January 2016 (UTC)

preventing sodium borohydride from reacting with alkyl halides (including iodides) and α,β-unsaturated carbonyl compounds (enones)
Sorry for asking so frequently -- but what's a good way to decrease the reactivity of sodium borohydride with alkyl halides (methyl and primary) and α,β-unsaturated carbonyl compounds while still being able to reduce imines?

I am aware of the Luche reduction. If cerium is not present, would sodium borohydride reduce α,β-unsaturated compounds at all? What is the resonance stablization energy of α,β-unsaturated compounds anyway -- is this a significant barrier to reduction? I'm not sure how to compare sodium borohydride's "reduction potential" to modified electrophiles. Yanping Nora Soong (talk) 21:15, 31 December 2015 (UTC)
 * is one lead-ref regarding the relative reactivity of sodium borohydride, and some parameters that can affect it. has a lot of variations on the boron-hydride theme (counter-cation, boron ligands, etc). That latter site says that Luche's special nature is mostly its 1,2 vs 1,4 control and that without cerium, sodium borohydride does do 1,4 of enones fairly well. From several of your questions, it seems like you are dealing with large-scale reactions or severely restricted reactant choices for some other reason (purely focuesed on cost and specific types of purification in the methylene iodide question), and maybe do not have access to some standard chemical literature databases (easy to use SciFinder to structures that contain various functional group combinations that react in certain ways). If you give us more detail about your situation, we can perhaps provide more useful answers. DMacks (talk) 22:58, 1 January 2016 (UTC)
 * They don't talk about imines in that priority list in that first reference. An imine that is N-alkylated but still retains two hydrogens on the carbonyl carbon will be more reactive than an aldehyde correct? Yanping Nora Soong (talk) 08:54, 3 January 2016 (UTC)