Wikipedia:Reference desk/Archives/Science/2012 August 7

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August 7

Scientific article self-criticism

Hello. I was wondering what the standard procedure is for including a discussion of the limitations or possible flaws of a scientific study (in chemistry in this case, though I doubt it matters) within the paper itself. DOes one generally put an independent section at the end, or what? thank you 134.48.233.92 (talk) 01:50, 7 August 2012 (UTC)

The standard structure of a scientific paper is Introduction-Methods-Results-Discussion, and that would be part of the Discussion section. Looie496 (talk) 02:28, 7 August 2012 (UTC)

It does vary.

I suggest that you go to the library of a nearby university and look at a range of scientific journals, and/or look online for scientific papers now available free, such as those put on the Web by the British Royal Society (http://rspa.royalsocietypublishing.org/). Most universities have guideline booklets - try a university bookshop. Some academic circles like the structure given above by Looie496, others prefer a structure such as Executive Summary - Conclusion - Methods & Results - Discussion - Appendicies (if appropriate).

The structure given by Louie496 is favoured by high school and college teachers, and some univesities. The structure I gave is especially favoured in industry - as it allows management, who normally don't have the time nor the expertise to understand the details (that's what they hired YOU for) to quickly decide a) your worth, and b) the commercial value of what you came up with.

If you have identified minor flaws or limitations in work you have done yourself, that do not invalidate your conclusions, you should normally include details in your discussion section. If you have identfied flaws that prevent a conclusion (sometimes an experiment you've designed fails to work due to unexpected reasons), you would include details in your discussion, and summarise it in the Executive Summary. If you are reporting on your own work, and sincerely believe you have done good work and your conclusions are valid, but you are aware that another researcher/worker/group has drawn opposing conclusions, the professional thing to do is to summarise the opposing view in an Appendix, ending with your critique of it. You don't need to copy their entire paper, you just need to reference and summarise it.

In writing any scientific paper, you should keep uppermost in your mind three fundamental things:-

1. Write for your target audience.

2. A good scientific paper does not just describe youy findings and what you did to get them. A good paper gives just sufficient (and only just sufficient) information so that (a) another competent worker can duplicate your experiment or research, and (b) allows a competent reader to spot any mistakes or omissions in your work. This can be harder to do that to describe, but it is the mark of a good paper. For example: "I tested the melting point of an xyz lead alloy by heating it until it melted. The experiment was repeated a few times and the result averaged." That's no good. "I tested the melting point of an xyz lead alloy by heating a 100g sample in a steel crucible with a gas flame. I repeated the test 6 times, allowing it to cool each time, and averaged the result" That's much better - other folk reading your paper might suspect you forgot the effect of the lead dissolving some of the iron, and they can either take into account the inaccuracy, or repeat the test with a better crucible.

3. Just because a good structure is Summary-Conclusion-Method&Results-Discussion, or whatever, it dosen't necesarily means that's what the headings must be, but the structure should be obvious.

Keit120.145.61.75 (talk) 03:29, 7 August 2012 (UTC)

I would be very surprised to see the outline(s) described by 120.145 used in a paper presenting primary research in a peer-reviewed scientific journal, which I strongly suspect is the type of situation considered by the original poster. The Abstract - Introduction - Materials & Methods - Results - Discussion - References outline is pretty much standard for academic journals (with the occasional publication that slots the Materials & Methods in after the Discussion) presenting peer-reviewed papers that are written by scientists, for other scientists—as opposed to papers written for executives, managers, politicians, or the lay public.

The limitations of a study (along with contradictory results in the published literature) are almost always addressed in the Discussion section, though there is often some connection to points brought up in the Introduction. TenOfAllTrades(talk) 04:18, 7 August 2012 (UTC)

I did say that the Summary-Conclusion-Method&Results-Discussion format is favoured in industry, and the Introduction-Methods-Results-Discussion format is more favoured in academia. Abstract is just another name for summary, though the term abstract does suggests a summary that may employ language at a specialist level, whereas the term executive summary suggests that a more lay style of language should be used. I do agree that the Abstract - Introduction - Materials & Methods - Results - Discussion - References format is very common to peer-reviewed journals. I see no evidence that the OP is in an academic environment or a commercial environment, but note that if he/she is ready to submit to a peer-reviewed journal, it is unlikely that he/she hasn't already had exposure to such journals, and should already be familiar with common formats, and indeed the "house style" of any target journal. I had considerable research & development experience, and had written many papers, while working in the research department of a large company, long before I went to university (on company sponsorship). None of those papers were published in external journals (most of them were commercially sensitive), but that does not mean they were not legitimate. They all conformed to Summary-Conclusion-Method&Results-Discussion format. A format without a single paragraph Executive Summary and a Conclusion right at the front would not have been accepted. Keit124.182.16.69 (talk) 05:33, 7 August 2012 (UTC)

I admit that I'm reading something into the OP's use of the word 'paper'. A private-sector document that was not intended for external publication is more likely to be termed a 'report', whereas 'paper' tends to be used to refer to written works that come from the academic side of the fence. (It's not a 100% hard-and-fast rule, of course.)

I'm also guessing academic (and relatively inexperienced, at that) because this question is being asked. Someone with years of experience would know the answer to the question already because of their extensive exposure to the literature; I suspect that we're dealing with a fairly young individual: perhaps an undergraduate doing a critique of a paper, or a summer student or younger grad student preparing one of his first manuscripts for publication.

Finally, of course, the OP's IP address is assigned to Marquette University—which I think is rather suggestive. TenOfAllTrades(talk) 15:57, 7 August 2012 (UTC)

Sodium triphosphate alkalinity?

How can I convert sodium triphosphate solution molarity into pH? Ideally I'd like a general formula, not just a pH of specific molarities. 70.59.11.32 (talk) 02:56, 7 August 2012 (UTC)

You'll need the 5 K_a values for triphosphoric acid. From those you can calculate [H⁺] and thus the pH.--Jasper Deng (talk) 03:08, 7 August 2012 (UTC)

"The first two pK_a values are small, pK_a3 is 2.30, pK_a4 is 6.50, and pK_a5 is 9.24."[1] I don't understand how to use these values for acidity to get alkalinity, and am hoping there is an article explaining the [H⁺] formula. 70.59.11.32 (talk) 09:14, 7 August 2012 (UTC)

In this case, then, it may be valid to assume that there is negligible disassociation after the first two protonations, so you only have to consider the last three. Depending on the amount of precision you want, though, this calculation can be arduous. See acid disassociation constant for what I'm talking about.--Jasper Deng (talk) 16:14, 7 August 2012 (UTC)

Acid dissociation constant. DMacks (talk) 17:03, 7 August 2012 (UTC)

Oh, it's coming back to me now. I repressed all this (which seems like a reasonable coping mechanism.) So for B + H₂O ⇌ HB⁺ + OH⁻, K_b is going to be K_w (which depends on temperature) divided by K_a. The temperature is going to vary unpredictably over a wide range for the underlying question, but it seems like subtracting from 14 is the accepted thing, accurate to a few percent at 25 Celsius. 70.59.11.32 (talk) 20:28, 7 August 2012 (UTC)

H2o2

What would be the fastest way to breakdown a liter of h2o2 from local pharmacy (i think concentration is 3%) to regular h2o in case of emergency? How long would it take?GeeBIGS (talk) 07:29, 7 August 2012 (UTC)

If you are trying to get drinking water, wouldn't it be easier to store drinking water ? (Store it in glass bottles, so it won't absorb chemicals from plastic.) If, for some strange reason, you find yourself with just hydrogen peroxide, how about pouring it into a blender and turning it on, to increase the reaction rate ? StuRat (talk) 07:39, 7 August 2012 (UTC)

Yes. But when all the water is gone and the filters are spent and there is no electricity for the blender for like a year and for some reason surprisingly I still have like a half bottle of peroxide left .....What would be the fastest way to breakdown a liter of h2o2 from local pharmacy (i think concentration is 3%) to regular h2o in case of emergency? How long would it take?GeeBIGS (talk) 07:46, 7 August 2012 (UTC)

Considering that people regularly gargle with 3% H₂O₂, it's apparently not all that bad in it's initial form. However, if you've lost electricity, how about pouring it into a bowl and stirring with a whisk ? StuRat (talk) 08:00, 7 August 2012 (UTC)

Even just 3% hydrogen peroxide can kill rats if swallowed, and our own article mentions some human consequences of ingesting it. I don't think it would be appropriate for anyone here to tell you how to turn H2O2 into drinking water lest you actually try it. Someguy1221 (talk) 08:07, 7 August 2012 (UTC)

Your link labeled "can kill rats" is the MSDS, which says nothing about it killing rats. StuRat (talk) 09:26, 7 August 2012 (UTC)

Are you sure? "Hydrogen Peroxide: ORAL (LD50): Acute: 2000 mg/kg [Mouse]"[2]A8875 (talk) 10:40, 7 August 2012 (UTC)

That explains it then. I did a search on "rat" and didn't find it. A mouse isn't quite the same. StuRat (talk) 22:36, 7 August 2012 (UTC)

Give me a break. All this desk talks about is crazy chemical reactions noxious explosive radioactive substances and you don't tell the op to try it. Did you just tell me to blend peroxide and drink it. Ok here goes....thanks.GeeBIGS (talk) 08:17, 7 August 2012 (UTC)

Have you read Hydrogen_peroxide#Decomposition? Throw in your silver. (Not sure how long it would take.) --Colapeninsula (talk) 09:20, 7 August 2012 (UTC)

I seem to recall that crushing a mammals liver and throwing in an extract does it pretty well, due to traces of peroxidase.--Gilderien Chat|List of good deeds 13:30, 7 August 2012 (UTC)

Potassium iodide is commonly used as a catalyst for decomposition in the Elephant toothpaste demonstration. It is also the iodizing agent in iodized salt. I don't know how well table salt would work, and in the end I suppose you would end up with salt water, which probably isn't what you're looking for... KI is also distributed for radiation emergencies to limit the uptake of radioactive iodine isotopes. If your theoretical emergency shelter has a stockpile of KI pills in case of nuclear attack, then maybe you could use one of those to catalyze it. 209.131.76.183 (talk) 15:07, 7 August 2012 (UTC)

This is not settled policy, if the poster requires more information he should feel free to ask for it. μηδείς (talk) 22:18, 7 August 2012 (UTC)

Per Medeis, there is no such policy to close this thread, and this is hardly highly dangerous anyway; hydrogen peroxide is an approved food additive. Just boil the stuff for an hour or so. That will speed up the disproportionation reaction without contaminating it with some catalyst. H₂O₂ is added to refined sugar to bleach it white and moderate ambient heat + time leads to no detectable residual reagent in the final product; just oxygen and water. 222.165.204.195 (talk) 09:25, 8 August 2012 (UTC)

If you only have a half-bottle left, boiling it for a few hours isn't going to leave you with much... Of course, I suppose I would have been out looking for water to boil long before it got to the point where I needed to drink hydrogen peroxide to survive. 209.131.76.183 (talk) 11:51, 8 August 2012 (UTC)

OK, One liter of 3% hp solution in glass bottle at room temp: how long to get all h2o? Then things to try to speed that up: boil with lid to recapture the evaporated h2o similar to salt water:, how much faster? Or put bunch of silverware in: how much faster?165.212.189.187 (talk) 15:13, 8 August 2012 (UTC)

• Since this has been unhatted, let me make a clear statement: Anybody who drinks hydrogen peroxide, regardless of how it has been treated, is taking an idiotic risk. There is no plausible reason why it would ever be anything other than utterly stupid. Looie496 (talk) 16:28, 8 August 2012 (UTC)

Unless the "treatment" makes it NOT hydrogen peroxide any longer.165.212.189.187 (talk) 17:28, 8 August 2012 (UTC)

Which you would have a hard time verifying. Or, rather, let me say you would have a hard time verifying that you eliminated all but the h2o out; and for the amount of water you'd get versus getting any kind of sick from small amounts of remaining poison, I can't imagine the point- even in a wasteland emergency situation, the amount this small ration will prolong your life isn't really worth the risk, you'd be safer going out and looking for water than risking illness (unless you're talking post apocalyptic world and you have an endless supply of peroxide and lab equipment and etc., is this what we're talking?) Phoenixia1177 (talk) 09:03, 9 August 2012 (UTC)

Yes, endless supply.... whatever what is the rate of decomposition for h2o2. i know it says it in the article but I am not a scientist so I can't understand the formula. Cant someone answer this??I don't understand why everyone here is so concerned with the context of this question, or the op's ultimate motive.165.212.189.187 (talk) 13:06, 9 August 2012 (UTC)

The rate is not given in the article. The article only gives thermodynamic data from which the kinetic information that you want i.e. The rate, cannot be infered. Depending on the order of the rate equation, the actual rate may be a function of the concentration of the hydrogen peroxide, the dissolved oxygen or both or neither. As for why all the fuss about the OP's motives; this wouldn't be wikipedia without the drama. 112.215.36.172 (talk) 14:03, 9 August 2012 (UTC)

Using experimental data from a few high school science projects on hydogen peroxide catalysis I found with google and some back of the envelope calculations, 5mins of boiling should bring 30% peroxide down to less than 0.01%. Reflux that i.e. Cover the pot while boiling so you don't loose much steam and you should have fairly pure water. 112.215.36.172 (talk) 15:16, 9 August 2012 (UTC)

You seem to forget the catalysis part of those science projects.. Boiling a peroxide solution ,especially a stabilised one (and all commercial peroxide is stabilised) will not destroy the H2O2, it will boil away the water leaving a stronger concentration behind. The vapors are quite unpleasant, and concentrating H2O2 by boiling at atmospheric pressure likely ends with a runaway exothermic reaction of the liquid or a detonation of the fumes. Ssscienccce (talk) 04:07, 10 August 2012 (UTC)

The experimental controls provide uncatalysed reaction rate data. You wont boil away any significant amount of water in 5 minutes, and even less with refluxing. I buy unstabilised hydrogen peroxide for use in NAG testing all the time, but even with stabilisers, they only slow the reaction, which is over come by the heat. 112.215.36.179 (talk) 05:25, 10 August 2012 (UTC)

Oh, and the blank used in my NAG tests, is 15% hydrogen peroxide boiled for 2 hours. No explosive ignitions of vapors to date, with thousands of samples successfully tested. 112.215.36.179 (talk) 05:55, 10 August 2012 (UTC)

It's not drama, if the op was curious about the rate, they should have just asked about the rate, they specifically gave the context. If I came here and asked what is the most accurate crossbow I could build from household supplies, I'd expect an answer to that specific question; if I asked what's the most accurate crossbow I could build from basic supplies in the event burglars break into my house, I'd expect someone to comment on the stupidity of even bothering since I would be giving that analogously absurd context. Why phrase a science question in a context if that context has nothing to do with the question and no bearing on anything? I can't imagine it's just to keep things flavourful and interesting on the reference desk. Phoenixia1177 (talk) 20:45, 9 August 2012 (UTC)

Phoenix, I NEVER said that I was going to drink it. That was inferred by everyone.GeeBIGS (talk) 05:28, 11 August 2012 (UTC)

I'm not forgetting the catalysis part. You just don't seem to understand that in order to gauge the effect of a catalyst, you need a control. That control provides uncatalysed reaction rate data. You're not going to get any significant concentration of peroxide from 5 mins of boiling in any case, and ignition of vapors? Sensationalistic nonsense. The heat will cause the peroxide to breakdown several orders of magnitude faster than the water will evaporate at. The stabilisation slows the reaction, and not all commercially available product has stabilisers anyway (I need unstabilised stuff for NAG testing in my lab). 112.215.36.179 (talk) 05:25, 10 August 2012 (UTC)

Find an alkaline battery, break it open, take some of the black outer stuff (manganese dioxide), drop it in your H2O2. Ssscienccce (talk) 21:15, 9 August 2012 (UTC)

As for the time it takes, that depends on the surface area of the MnO2 and the amount of Mn ions formed. The MnO2 from batteries is a paste mixed with carbon, likely to have a big surface area. High PH is supposed to help (and is very likely since you probably get some NaOH on the MnO2 while disasembling the battery). Still it may take hours depending on amount of MnO2 and particle size. Ground potatoes or liver would do the job as well. Ssscienccce (talk) 21:56, 9 August 2012 (UTC)

Lets see... break open car battery to put in potential drinking water OR ground up some potatoes to put in? Hey 112 thanks, why don't you try some experiments and post results?165.212.189.187 (talk) 15:47, 10 August 2012 (UTC)

I'll be back in the lab on monday, so I'll have a quick go at it then. 112.215.36.179 (talk) 08:25, 11 August 2012 (UTC)

bug identification

Resolved

Can anyone identify this bug for me, please?—msh210℠ 17:44, 7 August 2012 (UTC)

It's definitely not a bug, it looks like a type of fly. What size is it? Roger (talk) 18:01, 7 August 2012 (UTC)

I was using bug colloquially. It's about an inch and a half long (ignoring the wings and feet).—msh210℠ 18:47, 7 August 2012 (UTC)

From the mouthparts and the general shape, it's either a robber fly or (less likelier) a mydas fly. That's about as far as identification can go without going to an expert and getting clearer photographs.-- OBSIDIAN†SOUL 18:12, 7 August 2012 (UTC)

It looks redder than any of our pictures of the Mydas fly, and than most of our pictures of the robber fly. Hard to tell (as you noted, Obsidian Soul) in my pictures, but this was reddish throughout: a sort of burnt sienna (or so) in some places and a sort of burgundy (or so) in others. (Except the wings, which were pale.)—msh210℠ 18:47, 7 August 2012 (UTC)

If it helps for identification, I found this bug in St. Louis County, Missouri. Thanks for the answerers' help thus far.—msh210℠ 18:47, 7 August 2012 (UTC)

It looks almost certainly to be "Hanging Thief" of some sort to me (which is in fact a type a robber fly of the genus Diogmites). Missouri would certainly be smack in the middle of their usual range. Specifically it seems likely to be a specimen of Diogmites ternatus, but the level of resolution in the photos leaves some doubt. That site is a great resource for entomological identification, btw, and you can always upload the images there for further (somewhat expert) opinions. Snow (talk) 19:24, 7 August 2012 (UTC)

Yes, that is, indeed, what it looks like. Thanks so much!—msh210℠ 19:39, 7 August 2012 (UTC)

Happy to be of help. :) Snow (talk) 19:41, 7 August 2012 (UTC)

Proof crosswords help with any objective cognitive function

I've seen a few critique articles of "brain game" (such as lumosity) garbage claims (which I'm not defending) that show evidence that doing such things only makes you good at those games with no transferable benefits, and more than one of the articles end with the same "you're better off playing a crossword puzzle." But is there objective evidence that that does anything other than make you good at crossword puzzles? 20.137.18.53 (talk) 18:42, 7 August 2012 (UTC)

You're right to be skeptical; there are a lot of non-empirical claims thrown about suggesting very precise correlations between various "brain teasers" and benefits to various cognitive functions and these are often untested (and even, to varying degrees, untestable, given the complexities of the mental functions involved). All of that being said, crosswords, being as popular and enduring as they are, have gotten a little bit more exposure to genuine structured inquiry (1, 2, 3). All of that being said, there's very little doubt that crossword puzzle does stimulate some amount of cognitive function in the area of memory recall, both in terms of maintaining the general robustness of those areas and in committing specific facts to memory (or reaffirming and strengthening those already there). But of course that's clearly obvious; making any more substantive claim than this general assumption is problematic, however. No mental task exists in a vacuum of course, and any activity which requires your focus is adapting your brain to process certain types of information, but as to which puzzle is likely to lead to a quantifiable uptake in which variety of cognitive performance (other than, as you say, repeating that exact task), I'd beware of any highly specific claims. Snow (talk) 20:17, 7 August 2012 (UTC)

This reminds me of my experience in selecting and hiring new employees (for technical roles). A current fad amongst human resource people is to have potential new empoyees do a so called aptitude test, such as Raven's Progressive Matrices (http://en.wikipedia.org/wiki/Raven%27s_Progressive_Matrices). In my experience, there is NO correlation between how well new employees turn out and their raven score. Doing well in a Raven test just proves you can do well in a Raven test. It is well known in the engineering game that occaisonally you get a new chap who has an outstanding academic record, honours, high exam marks, etc, but is fairly hopeless on the job. It seems that some folk are just good at passing exams. So yes, I think playing games alleged to improve cognitive ability probably just only improves your ability to play those games. Our local newspaper started printing a certain type of game in each Saturday issue. At first I found them very difficult and did not solve many of them. Now, after a year's practice, I solve them consistently in seconds. Does this make me a smarter perosn? I really don't think so. Wickwack124.178.171.30 (talk) 22:54, 7 August 2012 (UTC)

effect of exercise on cholesterol blood testing

Does exercising vigorously before taking a blood test for cholesterol levels affect the results of the test? — Preceding unsigned comment added by 98.207.213.14 (talk) 21:05, 7 August 2012 (UTC)

I think it could, yes. In any case, multiple tests are required, since any one test isn't that useful of an indicator. StuRat (talk) 22:33, 7 August 2012 (UTC)

It can. See [[3]]. Dominus Vobisdu (talk) 23:23, 7 August 2012 (UTC)

mars rover

How will the mars Rover get off of mars?

-wikifriend — Preceding unsigned comment added by 205.142.178.36 (talk) 21:39, 7 August 2012 (UTC)

Well how would you figure the Rover would get off of the red Planet? I just want to know what the plan is.— Preceding unsigned comment added by 205.142.178.36 (talk • contribs)

There is no plan. When the curiosity's nuclear battery finally dies, it will simply sit there forever. Perhaps one day future Mars explorers will recover it to send it to a museum on Earth, but there are no plans for that. Someguy1221 (talk) 22:11, 7 August 2012 (UTC)

Instead of bringing Mars satellites home to place in a museum, perhaps a future Mars colony will place them in a museum of their own. StuRat (talk) 06:10, 8 August 2012 (UTC)

Of course that won't stop the Earthers from stealing the rover with a number of other priceless national treasures during their violent suppression of the Cydonia Rebellion. Snow (talk) 11:09, 9 August 2012 (UTC)

Remember that forever's a long time. Assuming no further human or post-human intervention once it becomes kaput it will eventually either be eroded into dust by dust storms or buried by them in situ. The only thing we send back to Earth is the data. SkyMachine ⁽⁺⁺⁾ 22:43, 7 August 2012 (UTC)

Perhaps you are thinking of the Russion Fobos-Grunt mission launched in late 2011. That mission was to land on one of Mars's moons (Phobos or course) to collect and return a soil sample. The Mission Plan section briefly describes the return plan. Unfortunately, the Fobos-Grunt joined the ranks of many other failed Mars missions when contact was lost and it failed to leave earth orbit. -- Tom N (tcncv) talk/contrib 23:22, 7 August 2012 (UTC)

Don't read this unless you can handle a little sadness right now: http://xkcd.com/695/ --Trovatore (talk) 02:05, 8 August 2012 (UTC)

Our article on the rover depicted in the comic is Spirit rover. -- 203.82.91.147 (talk) 13:45, 9 August 2012 (UTC)