Wikipedia:Reference desk/Archives/Science/2010 August 6

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August 6

Scent + washing

I kneaded some ground beef into patties this evening barehanded and then rinsed my hands with water. My hands still smelled of the ground beef (be it the actual beef or the spices I used). What generates the smell? Is it antigen? Is it actual beef/spice on my hands? And is washing enough to get rid of the smell a good indicator that any harmful bacteria from the raw beef is also gone? DRosenbach ^{(Talk | Contribs)} 03:07, 6 August 2010 (UTC)

Lots of spices and other food smells can dissolve in skin, and then remain behind for a considerable time afterwards. Onion is particularly potent for me, after cutting onions I can smell them for days. What I discovered works for me is to use undiluted automatic dishwasher liquid (like Cascade or the like) directly on my hands. Most handsoaps, in order to avoid drying out your hands, end up being as much moisturizer as soap (moisturizers and soaps work at cross purposes with regards to cleaning. One is trying to get grease off of your hand, the other is trying to put grease into your hands). Since the automatic dishwasher liquid is not normally designed to wash hands, it tends to be harsher as a soap, which is generally what you need to clean these smells off. This is of course all and YMMV. --Jayron32 03:52, 6 August 2010 (UTC)

I don't think you could use smell to indicate whether there's harmful bacteria on your hands. If the chemical making the smell has gotten right into your skin cells - in essence "staining" them - your hands might be perfectly clean (i.e. there's nothing "on" them), but still smell off. I mostly use ground chicken rather than ground beef, but I usually make use of disposable plastic gloves. Between the smell and the risk of contamination, to me it's worth the nickel to slip on pair of cheap plastics and toss them afterwards. Matt Deres (talk) 13:23, 6 August 2010 (UTC)

You might also try some of the hand-cleanser goop that they sell in DIY and Auto-parts stores - those are grey and don't smell of fruit and come in one gallon bright orange containers that don't look nice on your bathroom counter-tops - but they are really powerful degreasers with ground pumice as an abrasive. They do a spectacularly better job at cleaning your hands than the namby-pampy-girly stuff they sell in the soap aisle of a regular store...although you might want to apply some pretty scented moisturizer afterwards! SteveBaker (talk) 13:23, 6 August 2010 (UTC)

Yes, it's good stuff. See Swarfega. 87.81.230.195 (talk) 21:11, 6 August 2010 (UTC)

The stuff contained in the bright orange container has lots of pumice in it. Sure, it may scrape your skin cells off, but after a cleaning like that your hands won't smell like ground beef anymore! -- Sjschen (talk) 03:48, 7 August 2010 (UTC)

I don't know about ground beef, but I find the same can happen after chopping chillies (lick your fingers hours after washing your hands and it still burns your tongue) and that's because the capsaicin in the chilli isn't very soluble in water. If you wash you hands in oil (just normal cooking oil is fine), it gets them clean. It is possible some of the spices you were using are also oil-soluble. --Tango (talk) 16:28, 6 August 2010 (UTC)

You can also try using stainless steel soap, but it will only get rid of the scent and not any of the bacteria. ~AH1^(TCU) 00:24, 7 August 2010 (UTC)

microscopy terminology in a formal paper

I want to use terms like "north" and "south" instead of "above" or "below" to avoid ambiguity with structures below or above the focal plane. Is this permissible in a formal paper or a poster? John Riemann Soong (talk) 04:06, 6 August 2010 (UTC)

I would say no. I think that would annoy readers. Looie496 (talk) 04:43, 6 August 2010 (UTC)

Is there a good alternative? John Riemann Soong (talk) 05:30, 6 August 2010 (UTC)

Higher/lower? more/less gpe divided by mass? more/less attraction to the earth? —Preceding unsigned comment added by 91.103.185.230 (talk) 08:30, 6 August 2010 (UTC)

I would say that if there are no pre-existing conventions for describing such things and providing you define your terms clearly - then it should be acceptable. If you're going to do that, I would suggest that you use North/South/East/West to describe positions within the focal plane and Above/Below to describe positions along an axis perpendicular to the plane. But there are other approaches you might consider: X, Y, Z with (X,Y) being in the focal plane and Z being above/below it. You could also define a couple of acronyms: AFP and BFP for 'Above focal plane' and 'Below focal plane' (eg "In this image, the longitudinal structures are ~10um AFP"). So long as you are very clear about your conventions up-front, you should be OK. If there is an established convention that you're merely unaware of, then I'd expect the peer-reviewer or editor to suggest an alternative - I doubt that an otherwise meritorious paper would be rejected on those grounds so long as you take care to clearly state the conventions you are using. SteveBaker (talk) 13:17, 6 August 2010 (UTC)

I don't believe I've ever seen that nomenclature used in a formal poster, and certainly not in a paper. You might hear a more casual speaker use that sort of terminology with a friendly audience. While I completely understand why you'd want to use unambiguous terms here, I'd be afraid that such non-standard terminology would be very jarring to a reader or a reviewer. In most cases, you can write your text and figure captions in such a way that the intent of "above" is clear from context. In the remaining situations – as SteveBaker says – your best bet is to go with x, y, and z. The xy plane is almost always taken to be coplanar with a focal plane, while the z direction takes you through different focal planes. If there is any potential for confusion about the orientation of any images or renderings, you can even include a little two-arrow legend adjacent to or overlaid on the image that explicitly identifies the axes shown. TenOfAllTrades(talk) 13:52, 6 August 2010 (UTC)

"Closer" and "farther". Cuddlyable3 (talk) 20:01, 6 August 2010 (UTC)

resin

what's a resin chair —Preceding unsigned comment added by Tomjohnson357 (talk • contribs) 05:39, 6 August 2010 (UTC)

Resin in this case is just a kind of plastic. Looie496 (talk) 05:51, 6 August 2010 (UTC)

This picture (at right) is a typical kind of resin chair - they are cheap because they can be injection molded with a simple two-part mold, they are lightweight and stackable (which makes shipping them cheap) and they are made from an inexpensive resin-based plastic. From an industrial design perspective, they are the perfect solution. From the customer's perspective, they are cheap, moderately comfortable and waterproof - but the plastic gets brittle from prolonged exposure to UV light and tend to break catastrophically - so they actually do a fairly poor job as lawn furniture. SteveBaker (talk) 13:02, 6 August 2010 (UTC)

Probably this kind of chair. ~AH1^(TCU) 00:09, 7 August 2010 (UTC)

Bacon Cheeseburger Armpits

This is rather odd, but I've noticed my underarms smell like bacon cheeseburgers sometimes. Even thought I haven't eaten one in months. (And I don't sleep with cheeseburgers nestled in my pits either). And I bathe 1-2x daily with non-cheeseburger scented body wash. Any ideas on how a person's body could make such a scent? (Please don't let this fall under the dreaded 'medical advice') I'm just curious how a cooked meat scent could be manufactured from a body. Or is my nose just picking up similar compounds and it's firing the same triggers in my brain that equal cheeseburgers? --69.148.250.94 (talk) 06:12, 6 August 2010 (UTC)

Odor in the underarms in not created by the body. It's created by bacteria. However the bacteria eat food that is secreted by the body, so the body can influence them to some degree. It seems to me you were colonized by bacteria that happen to excrete that particular smell (which is not strange, the smell of lots of foods is created by bacteria, for example cheese, wine, etc.) If you can culture them, maybe you can sell it :) If you want to change the smell first you need to serializesterilize your underarms (harder than it sounds), then colonize them with your choice of bacteria - another person is probably your best source. Ariel. (talk) 09:26, 6 August 2010 (UTC)

Serialization is really the best way to go? Vimescarrot (talk) 09:36, 6 August 2010 (UTC)

Probably sterilize. Bus stop (talk) 09:50, 6 August 2010 (UTC)

Yes, that's what I meant, I was tired and didn't proof read. Ariel. (talk) 19:35, 6 August 2010 (UTC)

I cannot fucking believe you just told this guy to culture his underarm flora and (presumably) proceed to sell it as all-natural natural cheesburger-flavoring. Would your mother be proud of you if she knew you were enabling a guy to feed his underarm flora to millions? 84.153.230.246 (talk) 12:38, 6 August 2010 (UTC)

Hmm, 84.153 I'm very impressed how well your English has improved since your lasts edits!!! Caesar's Daddy (talk) 21:58, 6 August 2010 (UTC)

Woaah...calm down! I think everyone but you understands that this is a little gentle humor - which is permitted on the reference desk. We might, perhaps, encourage Ariel to toss a couple of <small> tags into an otherwise interesting and relevant answer. SteveBaker (talk) 13:07, 6 August 2010 (UTC)

I put a smiley on there! It was a joke, and like the best jokes it has an element of truth - he really could do that, and I bet people would buy it (but not to eat, to use in their own underarms). But it would be very difficult, many bacteria are hard to culture out of their home environments. Ariel. (talk) 19:35, 6 August 2010 (UTC)

Similarly, I have noticed a close similarity between the white matter I scrape from under the nails of my big toes, and certain expensive varieties of cheese. I truly believe that the sweaty fatty exudate from the human body can ferment to duplicate various pungent gourmet dairy flavors/odors. Evolutionarily, in primitive mammals, before there were milk glands, there was fatty sweat, as from monotremes. Edison (talk) 02:50, 7 August 2010 (UTC)

Well Ariel, they just happen to do life saving feces transplants. Maybe you are simply ahead of the game with this whole armpit bug transplant business ;) -- Sjschen (talk) 03:43, 7 August 2010 (UTC)

oil paint

why is oil paint in ny illegal —Preceding unsigned comment added by Tomjohnson357 (talk • contribs) 06:45, 6 August 2010 (UTC)

Reasons include toxicity and odor of the fumes, as well as potential ozone-layer-damaging chemicals. But frankly, this is proving a pain in the ass to find good information on; my google searches are only turning up blogs and forums. Someguy1221 (talk) 08:42, 6 August 2010 (UTC)

Several states in that area have banned oil paint (the kind used for walls, etc.; not sure if it also applies to artists' materials) in 2005. See for example [1] DMacks (talk) 08:48, 6 August 2010 (UTC)

No, I believe artists' oil paint is still available. Bus stop (talk) 11:08, 6 August 2010 (UTC)

Professional paints are likely alkyd based. In many countries they are indeed banned or discouraged because of the toxic fumes, to be replaced by waterbased paints, see Latex#Uses_of_latex. --VanBurenen (talk) 11:19, 6 August 2010 (UTC)

Disposal of the stuff is very difficult - it clogs drains alarmingly easily and it's pretty toxic too. There are plenty of modern, water-based, paints that do a comparably good job and are much less harmful both to the environment and the city infrastructure. SteveBaker (talk) 12:54, 6 August 2010 (UTC)

Type of engineering degree

Help me please :) Chemical engineering or mechanical engineering at university - which one gives better career prospects? I would like a job involving foreign travel. Thanks! 86.144.112.57 (talk) 11:57, 6 August 2010 (UTC)

Both career tracks have reasonably good prospects over so many broad fields that it's hard to answer your question meaningfully. Though, with the decline of the auto-industry, there's been a bit of a deflationary trend in mechanical engineering, compared to other disciplines. The U.S. Bureau of Labor Statistics introduction to Engineers has some useful links and you can find hard numbers for number-of-hires across disciplines. (But, analyzing those kinds of statistics is not as straightforward as counting the number of new-hires). Also, whether these current trends will be relevant over the timescales of your entire career is all speculation. Chemical engineers can work in all kinds of fields; if you work in upstream petroleum, your prospects of foreign travel are very high; but chemical engineers more often find careers in refining and petrochemical companies. Chemical engineers can also work in materials, biological/medical/pharmaceutical industries, and like all engineers, can cross discipline-boundaries depending on individual specializations. Nimur (talk) 13:51, 6 August 2010 (UTC)

I was already thinking of oil, actually. Just wasn't sure which subject (or perhaps a totally different one?) would be most useful in that industry. So you think chemical engineering is a better bet? My problem is I really don't know how oil exploration or drilling works in detail, so not sure what the most important skills to pick up would be. There's not much chance of a school trip to an offshore rig in the North Sea (I'm in England btw). 86.144.112.57 (talk) 14:57, 6 August 2010 (UTC)

You might be surprised the kinds of programs and educational opportunities available in the oil industry. Society of Exploration Geophysicists' Student Education Program is geared toward advanced undergraduate and graduate students (so, wait a year or two), but they can provide funding for travel and training. So can EAGE's Student program - both are international, but EAGE has a definite European concentration. As a chemical engineer working upstream, you can be a valuable asset - geochemistry, mud logging, and assaying all happen in the field. As a chemical engineer working in the refinery, you'd be focused on process control, efficiency, and the world's largest stoichiometry problem: balancing the carbon in and the carbon out, and making sure you have enough hydrogen atoms (and energy) for the reaction. Also consider if your university offers a course in petrochemistry or petroleum engineering. Nimur (talk) 16:05, 6 August 2010 (UTC)

The major aircraft manufacturer I used to work for hires a lot of mechanical engineers and is often involved in long-term multinational projects. For some engineers, there is a great deal of travel between international partners and/or suppliers, though not all engineers get to travel.

Of course, you shouldn't pick your degree based on which one could result in international travel. If you are good enough in your stay-at-home job, the rewards could lead to you being able to travel for leisure, and I think most people will tell you it is nicer to travel the world as a tourist, than going great places and only ever seeing the inside of an office. On the other hand, whenever I've travelled on business, I've made a point of getting out of the hotel and taking weekends off (working extra hard during the week makes that easier to do :-)). Astronaut (talk) 21:54, 6 August 2010 (UTC)

Chronobiology of sunsets

If we assume that most people find sunsets pleasing in some way, perhaps even beautiful, we should ask why. Could it be that the pleasure derived from watching a sunset leads to calm and relaxation, and helps us sleep? Do sunsets have light effects on circadian rhythm in mammals? Viriditas (talk) 12:25, 6 August 2010 (UTC)

I think you've probably nailed it already. To humans living out in the wilds with no electric light, etc - the setting of the sun would indicate the end of the main work for the day - a time to start unwinding and getting ready for sleep. Such cues to behavior are ingrained into our bodies more deeply than many of us realize. But I'm not aware (and was not able to easily find) any research on the subject. SteveBaker (talk) 12:52, 6 August 2010 (UTC)

But we also find sunrises beautiful. I think it's an unintended consequence. As primates,we have good colour vision and we find bright colours pleasing (usually) as part of our "programming" to find ripe fruit. Sunrises and sunsets are beautiful for the same reason rainbows and bright blue skies and strawberries are beautiful - because they are full of bright colour. Matt Deres (talk) 13:29, 6 August 2010 (UTC)

Not everything needs an evolutionary explanation. I'd venture the guess that sunsets, like many natural phenomena with a dramatic visual component, are actually aesthetically pleasing. Paul (Stansifer) 16:26, 6 August 2010 (UTC)

Actually, everything has an evolutionary explanation, whether you think it's needed or not. Even if the explanation is "Because it randomly occurred in my ancestor and any survival disadvantage to the trait was not very significant". Comet Tuttle (talk) 17:07, 6 August 2010 (UTC)

Which is a pointless tautology. An explanation like that is too generic to be of use to anyone and can safely be disregarded. Matt Deres (talk) 18:09, 6 August 2010 (UTC)

But why do we have a sense of aesthetics that is such that sunsets are aesthetically pleasing? --Tango (talk) 23:20, 6 August 2010 (UTC)

The article Aesthetics considers why we appreciate Beauty. Some sunsets are shown in the article Sunset and in wide varieties here. (OR) No printed photograph captures the brilliance and surprise value of some real sunsets, and they make one aware of the temporary and unique nature of what one is seeing. It's a lovely way to round off the day. Cuddlyable3 (talk) 19:55, 6 August 2010 (UTC)

See beauty of nature. ~AH1^(TCU) 23:58, 6 August 2010 (UTC)

Why? That article doesn't mention sunsets. Cuddlyable3 (talk) 03:41, 7 August 2010 (UTC)

Surface tension

I'm a bit confused about surface tension. I know that surface tension should act parallel to the surface, but the diagram of water molecules on the surface tension page seems to suggest that the force is perpendicular to the surface. Can someone help me visualize why, from the molecular picture of a liquid, the force would be parallel? Thanks. Related question: If water is placed in a capillary, why will the surface tension pull it up?76.69.241.253 (talk) 14:01, 6 August 2010 (UTC)

Surface tension#Cause offers an explanation. When an isolated (from gravity) drop of water attains a spherical shape, no inward movement of the surface molecules is possible and only forces parallel to the surface ( = tangential to the sphere) are demonstrable (think of a balloon). Surface tension#Liquid in a vertical tube explains capillary action. Example: The attraction between water & glass molecules is greater than water & water molecules. That results in a non 90 degree contact angle between the water surface and the inside of a glass tube. In a thin tube or capillary the water column is pulled up. Cuddlyable3 (talk) 19:39, 6 August 2010 (UTC)

Okay, I get the balloon analogy. But about the capillary action; I would think that the surface tension would pull the liquid inward, and stop the surface from rising... 70.52.44.90 (talk) 21:15, 6 August 2010 (UTC)

For some combinations of liquid and tube material, it does. Cuddlyable3 (talk) 21:33, 6 August 2010 (UTC)

I know, but I'm talking about in all cases (like, say, water and glass). The adhesive forces of the glass are stronger than the cohesive forces of water, so the miniscus is U-shaped. But if the surface tension pulls the water inward, then wouldn't the water be drawn in and not rise? 70.52.44.90 (talk) 22:33, 6 August 2010 (UTC)

I got a new water heater

This refers back to this question. Since the Sears store where I bought it didn't have one, they ordered online for me, and I believe it's model 32636 on this page.

The plumber who installed it said, after I specifically asked that the water not be too hot, that he turned it up a little because it was set real low. It is the perfect temperature, as it turns out, so it makes me wonder what is "real low" and how did they (whoever set it before the plumber) decide to set it there in the first place?Vchimpanzee · talk · contributions · 20:02, 6 August 2010 (UTC)

I think the defaults are often set to be safe for babies, who can very easily be scalded by hot water. Looie496 (talk) 20:14, 6 August 2010 (UTC)

Any idea what that temperature is? And what if someone has a dishwasher and needs really hot water?Vchimpanzee · talk · contributions · 20:19, 6 August 2010 (UTC)

Hot water heater#Water heater safety has some info about temperature settings. I don't know if there are local codes prescribing specific licensed-installation standards (probably...there is for damn near everything else). DMacks (talk) 20:35, 6 August 2010 (UTC)

I did read that before asking my original question. I did miss the part about dishwashers heating the water further. That makes sense.Vchimpanzee · talk · contributions · 20:38, 6 August 2010 (UTC)

Not all dishwashers do that, you have to check your model specifically. But the biggest problem with low water temperature is the growth of legionnaires bacteria. Personally I would not risk it. Ariel. (talk) 23:17, 6 August 2010 (UTC)

I don't have one. I mentioned dishwashers only because they would be a reason for having the water temperature high enough to cause burns. Thanks for all your responses.Vchimpanzee · talk · contributions · 15:55, 7 August 2010 (UTC)

I have a follow-up question. The hot water now looks like it has soap in it. It's actually bubbles that dissipate quickly. Why would that be?Vchimpanzee · talk · contributions · 20:39, 8 August 2010 (UTC)

Is this what you mean? Aeno•talk to me 09:35, 9 August 2010 (UTC)

You may want to re-ask this as a new question. Old questions don't get read as often.Ariel. (talk) 06:30, 10 August 2010 (UTC)

Voltaic pile question

Is this true? It says that zinc ions oxidize copper to copper(II), themselves being reduced to zinc metal. I though it was the other way around (copper sulfate reacts with zinc). If it is wrong, then how does it work? Thanks. --Chemicalinterest (talk) 22:46, 6 August 2010 (UTC)

AFAIK, it's another counterion (hydroxide?) that balances the charge. 2 H2O + Cu(0) ===> 2 H+ + 2e- + Cu(II) + OH- ---> H2 + 2OH- + Cu(II). Cu(II) hydroxide is deposited. This is good, because it's hard for the copper hydroxide to come back and reverse the charge. That's how I think it works -- very high energy electrons are replaced with more stable anions. John Riemann Soong (talk) 22:44, 9 August 2010 (UTC)

I think that the reaction you stated happens on the zinc. My explanation would be oxygen gets reduced to hydroxide at the cathode and zinc gets oxidized to zinc ions at the cathode. --Chemicalinterest (talk) 00:27, 10 August 2010 (UTC)

The problem is that dioxygen IIRC is not usually reactive (in the kinetic sense) under STP for the purposes of electrochemistry (compared to say hydrogen peroxide, even though it is thermodynamically at a higher potential). It's in fact the primary problem with making hydrogen fuel cells. If you solve the problem of how to feasibly incorporate oxygen into an electrochemical reaction at STP you'll make billions. ;-) John Riemann Soong (talk) 20:41, 10 August 2010 (UTC)

Sub-woofer orientation

Should the sub woofer port point up or down? If down, then what clearance does it need from the floor, and is this affected by the type of floor covering: carpet, lino, wood etc? Also, can other structures in the room detract from the sub woofer output level?--88.104.88.126 (talk) 23:25, 6 August 2010 (UTC)

It is best to point to the listener, but second best would be into the largest volume of air, so down does not sound good if it is on the floor, it is more likely to vibrate the floor and produce other vibrating and shaking noises. Graeme Bartlett (talk) 00:31, 7 August 2010 (UTC)