Wikipedia:Reference desk/Archives/Science/2014 June 17

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June 17

free convection of heat transfer fluids

I have designed heat transfer engines using free convection. I have tried commercially available heat transfer fluids and none of those I have tried so far are as good as water in free convection.

I have suggested to manufacturers of these fluids that they grade their fluids according to their free convection properties compared with water. This would be quite easy to do using a vertical cylinder of the fluid with a heat source at the base. They could then rate the efficiency of their heat transfer fluid according to how fast the fluid higher up in the cylinder heats up using water as a standard for comparison.

Does anyone know if this grading of fluids according to the test described above has ever been done? And if it has what would it be called? If this has been done already I would not have to waste a lot of time trying different types of heat transfer fluids and finding in the end they are not as good as water for free convection heat transfer. — Preceding unsigned comment added by Petercl14 (talk • contribs) 02:33, 17 June 2014 (UTC)

Sure! There's a ton of money in mud engineering! It's a really empirical science; those guys have parameters for everything - fluid density, fluid thermal conductivity; electrostatic characteristics, chemical behavior ... variations of all of the above, with respect to temperature and pressure... you name it! From the Schlumberger Oilfield Glossary entry on temperature gradient , I found a link to High-Pressure, High-Temperature Technologies, a review article of common technologies used to characterize borehole fluids. That paper has an entire reference section, "For more on laboratory testing of fluids, see..." the dozens of references they cite. You might also find references on a variety of downhole heaters.

You can bet that if water was better for the job than commercial mud, production companies couldn't charge as much as they do for all their special chemical formulations! Nimur (talk) 02:46, 17 June 2014 (UTC)

Note that the test you devised is not testing thermal convection alone, but also conduction, radiation (unless you add dye to the fluid to make it opaque), and thermal capacity. Depending on the parameters of the test (height and diameter of the cylinder, temperature difference, elapsed time), different factors will play more or less or a role in the outcome. So, while water may be the best fluid given your parameters, it may not be for all such parameters. StuRat (talk) 05:29, 17 June 2014 (UTC)

A Heat pipe is a passive device that offers high thermal conductivity between points whose temperatures correspond respectively to liquid and vapour states of the internal fluid. The vast majority of heat pipes for room temperature applications use ammonia (213–373 K), alcohol (methanol (283–403 K) or ethanol (273–403 K)) or water (298–573 K) as the working fluid and have much higher thermal conductivity than is possible by convection or conduction in a single-phase substance. 84.209.89.214 (talk) 21:23, 17 June 2014 (UTC)

What gene (or genes) produces DHA?

Thx. Ben-Natan (talk) 06:45, 17 June 2014 (UTC)

To do this one, I first went to NCBI and chose the "Gene" database option, but the list was all eukaryotes for some reason. There ought to be a way to get the data out (i.e. go to PubMed and look up the papers the right way) but not having the patience I went to KEGG, which fortunately for the moment seems to have risen out of the water again, but is making some plea for funding. Anyway, it sent me straight to [1] which gives the immediate reaction upstream of DHA. This gives me an EC number [2] which represents the reaction catalyzed, which potentially could be more than one homologous gene, but often was evolved just once. Regrettably... that's a red herring; it's palmitoyl hydrolase, present in humans and many other organisms. But clicking on the precursor gets us quickly to [3] (well, at least, in not many clicks... the site is kind of slow) which is a diagram of the biosynthesis of many unsaturated fatty acids. Unfortunately, it turns out it's not providing the details on the precise enzymes doing the desaturation, though it does give an indication of the order in which the bonds are processed. [4] provides no EC number for example. So... looking for the last step, delta-6, quickly turns up in PubMed a paper that says that rats do it [5]. Now I remember that it's actually linolenic acid that is more special as a precursor. So I go back to scratch at PubMed and search "docosahexaenoic acid" "essential" "precursor" (spelling the first one is the challenge of this assignment) and find [6] which says the alpha-linolenic acid is the one that is essential. Looking back at the KEGG figure, this is on it; the linolenic acid is downstream of the delta-15 desaturation. After some flailing around I search "delta15" "docosahexaenoic acid" and get [7] which is one of those too sensible to work ideas of genetically engineering the benefits of omega 3 directly into an animal to improve its health. (This is one of those GMOs I dread, because it sounds like such a great idea, but messing with lipid metabolism has a thousand trickle-down effects that could be unpredictable) Anyway, this paper identifies some of the key genes they used to make the difference. I could go on, but have to pause for now... Wnt (talk) 08:46, 17 June 2014 (UTC)

Going on, they mention a delta-4 desaturase (just upstream of the delta-15 but also important, and an easier lead because they use the delta-15 from C. elegans) and one of the sources is "marine microalgae Pavlova lutheria" which our disambiguation link names as a chromalveolate. (As I recall this is your special interest) Unfortunately they don't give an accession number but they do reference [8] which is, somewhat surprisingly, "Elsevier open access" (honest) and so the audience can follow along here. I really ought to read that article, but for now I ^F'd "accession" and clicked [9]. It is tempting to hit "Run BLAST" from this but don't -- the link is for a blastn search of the mRNA, which will probably get you nothing that is not pretty closely related. Instead hit on the hyperlink for protein-id = [10] which gets you just the amino acid data. Now you can hit Run BLAST if you want, and if you're doing this for a serious purpose you would in a variety of ways trying to scrape every last homologue, but for now, I find the precompiled results at BLink lower down on the right sidebar to be sufficient. [11]. Sho'nuff, there are other chromalveolates in the list -- Rebecca from Pavlovaceae, the heterokont Aureococcus -- but after that the list takes a turn toward the multicellular, with choanoflagellates and a few outright animals, then on to trypanosomes and euglenoids... which leaves us with a need for a more careful search. The thing to remember, after all, is that BLink highlights the very best matches, which means that if you have an incomplete sequence, a few errors in your sequence, etc., or even just a turn in evolution that added a little loop somewhere in the catalytic site, then those hits are going to tumble down the rankings. Now if you can just look at the species names and tell which are chromalveolates you can get more out, but so far about all I recognize is Thalassiosira from further down the list. So now it's time to finally hit that Run BLAST link [12]. Going into the search parameters I'll turn the E-value down to 0.1 because I don't want a bunch of crap I'd have to confirm experimentally to convince anyone it's a real match, which should shorten the output a little. However, there's a bit of a snag ... turns out the taxonomy input won't take Chromalveolata - doesn't recognize it because when browsing taxonomy Alveolata is right under Eukaryota. So you'll have to assemble your own Chromalveolata according to taste. For now, I'll just run with Alveolata as an example. This yields [13] <--- TEMPORARY link, will expire June 20. This reveals one clear "hypothetical" delta4 for Paramecium, which is more than you had, but the others come up as delta5 or 6. There's some comment even in the first paper about the various bonds and how the enzymes work - I'm afraid you actually need to look very carefully at this point and figure out if the "delta5/6" activity delivers what you want. You can also BLink back from any of these proteins and see if they match a different protein as top link (subject to the caveats above) for organisms where you know you have a true ortholog. You may well end up drawing up multiple sequence alignments and trees before it is through. And of course you also have the other chromalveolate groups to do. At this point I can't go on much without having a better understanding of the underlying reasons behind your question and what you're really hoping to find, but I hope this gets you primed up to get started. Wnt (talk) 17:36, 18 June 2014 (UTC) @Ben-Natan:

Normal behavior by a headless cat?

The Jerome Lettvin article states that the neurologist found that a headless cat could walk on a treadmill, scratch an itch, and maintain its balance to avoid falling over. It cites a textbook as a reference, "Neurons and Networks Second Edition, John Dowling, Belknap Press of Harvard University Press 2001, page 307, Figure 13.5" as a ref but the relevant page is not viewable online. Presumably the body was connected to a source of oxygenated blood. I removed as vandalism the last sentence, added long after the rest, which stated that the cat later made a full recovery and led a happy life. The article says that unidentified Russian scientists replicated the experiment. There has long been a supposed film of Russian scientists having a disembodied but responsive dog's head connected to a source of oxygenated blood, which some have said is crude trick photography. I have certainly seen decapitated chickens run around flapping their wings for perhaps a minute, but I question whether higher vertebrates such as cats (or humans for that matter) have the decentralized nerve centers needed for walking, for instance, or maintaining balance even for a minute after decapitation. Does anyone have access to the book in question to confirm what it states about Lettvin's work? Edison (talk) 21:46, 17 June 2014 (UTC)

I don't have access to the source either, but I think there might be a misunderstanding here. Very few scientific studies have used cats that were actually headless, but there were quite a number of studies (in the "old days") that used cats that were spinalized -- in other words, the spinal cord was cut in a way that disconnected the head from the rest of the body. It's possible to get spinalized cats to walk on a treadmill by holding the body in place over a running treadmill -- see for example PMID 2357538. Looie496 (talk) 22:24, 17 June 2014 (UTC)

(EC)I found the page in question online [14] but it has a cat with surgical transection of the brain stem and electrical stimulation causes walking apparently due to spinal reflexes. However it lists several scientists as doing an original 1911 experiment and a Russian/Swedish team as doing a followup, with no apparent mention of Lettvin. Thus it was not quite a "headless cat" and Lettvin does not appear to be involved, but i would still appreciate confirmation that he is not referenced anywhere else in the book cited, before removing mention of the cat studies from his bio article. Would a human with a severed spinal cord be able to walk on a moving treadmill, or would carefully timed electrical stimulation at the spine suffice? Or would electrodes have to be on the limbs which were to move? Edison (talk) 22:56, 17 June 2014 (UTC)

Paralyzed humans don't walk reflexively in the way cats and some other quadrupeds do. It's pretty clear that eliciting walking with spinal cord stimulation is feasible in principle, but the technology isn't yet mature enough for use with humans -- PMID 24549394 is the closest thing I know about. I'd be surprised if devices to do that don't exist 10 years from now. Looie496 (talk) 01:31, 18 June 2014 (UTC)

Mike the Headless Chicken lived for 24 months after most of his head had been cut off. 84.209.89.214 (talk) 23:08, 18 June 2014 (UTC)

Keep it in mind that a short term (acute) experiment with electrical stimulation of the nervous tissue is one thing but a chronic functioning is another. Electrical stimulation of the visual cortex (area 17) was performed by Bradley (in the UK) if I am not mistaken in blind humans and caused some phosphenes but soon glial degeneration took place. In short, the neurons died out but glia proliferated at the stimulation site. --AboutFace 22 (talk) 14:54, 18 June 2014 (UTC)

• Death. μηδείς (talk) 20:27, 18 June 2014 (UTC)

The "walking headless cat" story made me think of an 1842 grammar book saying "Charles the First walked and talked a half hour after his head was cut off" just needed a semicolon and a dash added to be correct. Edison (talk) 00:02, 19 June 2014 (UTC)

Detleff Neumann-Neurode

Why is the article about Detleff Neuman-Neurode still in question ??? Why does it say in the beginning: NEEDS ADDITIONAL CITATION FOR VERIFICATION ??? Dr.Reinhard Ganz wrote his dissertation about D. N-N. and Mrs. Dehn opened a D. N-N Clinic in London, England. What more verification is needed??? I am D.Neumann-Neurode's granddaughter and wrote my memoirs about my childhood which I have spent at my grandparents home with my two sisters and my mother. (Title of the book: ONE LIFE MANY CHAPTERS) I am Margrit von Kleist. Please remove the note at the beginning of my grandfather's article. Thank you — Preceding unsigned comment added by 99.251.181.93 (talk) 23:32, 17 June 2014 (UTC)

This belongs at Talk:Detleff Neumann-Neurode, but anyway: The problem is not that anyone doubts your grandfather's existence (though Wikipedia has had some remarkable hoaxes over the years), but that the typical reader has no idea where most of the information in the article came from – and thus of its reliability. —Tamfang (talk) 01:14, 18 June 2014 (UTC)