Wikipedia:Reference desk/Archives/Science/2008 January 24

= January 24 =

Developmental Biology - Maturation after pairing
There is an animal species that does not complete development and maturation until it has paired with a mate. In other words, juverniles pair, develop to maturity, then mate. They pair for life, as do some other species. I have forgotten the name of the species. Does anyone else knows it?

Thanks,

4.239.0.107 (talk) 01:25, 24 January 2008 (UTC)


 * Any idea on mammal/bird/lizard etc? -- .ιΙ I n hu man 14 Ιι. 03:35, 24 January 2008 (UTC)

Probably mammal, probably small in size. —Preceding unsigned comment added by 4.239.6.115 (talk) 20:46, 24 January 2008 (UTC)


 * Schistosoma mansoni, according to this external article. (EhJJ) 00:34, 25 January 2008 (UTC)

Thanks, the article on Schistosoma is interesting, but the animal I am looking for is not a parasite but a free-living small animal, and it is the male that does not complete maturation until paired (probably the female as well). —Preceding unsigned comment added by 4.239.138.187 (talk) 22:37, 26 January 2008 (UTC)

Soluble solids of coffee
Why do "Gold Blend" style instant coffee granules take so much longer to dissolve in the hot milk than standard blend granules? DuncanHill (talk) 02:31, 24 January 2008 (UTC)


 * Firstly, I'm intrigued as to why you're dissolving them in milk rather than water, but anyhoo... Solubility of instant coffee generally depends on the shape of the granules and how 'holey' they are. I would not expect the type of coffee used to make them to affect the solubility much; mostly I would expect that to be a product of the drying process. I would suggest looking at the granules under a microscope if you can, to see the difference. Skittle (talk) 02:41, 24 January 2008 (UTC)


 * I use milk 'cos it tastes nicer! I do have a microscope - good idea, I'll do that. DuncanHill (talk) 02:57, 24 January 2008 (UTC)


 * I was intrigued because I've only encountered it as a South American thing to do, previously I'd be interested to hear your results. Skittle (talk) 03:29, 24 January 2008 (UTC)


 * I'll put up pics, but need to buy some "regular" instant first. Preliminary results indicate that the "Gold Blend" type granules are compact masses of fine crystals, with a low level of holey-ness. DuncanHill (talk) 03:34, 24 January 2008 (UTC)


 * Sounds like they could potentially be conglomerates of spray-dried particles then. These typically have lower solubility than freezedried granules, which have a more 'holey' appearance and are not conglomerates. But, we shall have to wait for a comparison. Skittle (talk) 03:41, 24 January 2008 (UTC)


 * Ouch! Speed to dissolve and "solubility" are completely different things. Some sugars for example are hard and slow to dissolve but you can ultimately dissolve a lot before saturation so they are very soluble. --BozMo talk 13:18, 24 January 2008 (UTC)


 * Yes, yes, but in the coffee industry they tend to use the terms fairly interchangably when refering to the exact thing which Duncan was asking about. So replace 'solubility' with 'speed to dissolve' in my earlier answers if it helps. Skittle (talk) 18:55, 24 January 2008 (UTC)


 * Anyway, I haven't been able to get any decent pics, but I have examined the two types of granule under the microscope. The "Gold Blend" type are, as I said before, fairly smooth compact masses of fine crystals, with few, small holes. Regular type are very irregular in shape, with a high level of holey-ness. Physical testing also indicates that the regular type are much more crumbly. DuncanHill (talk) 09:58, 26 January 2008 (UTC)
 * This gives the immediate explanation of the difference in time to dissolve (difference in surface area, as sugested by Skittle), but of course leads to the corollary question - why are "gold blend" type granules produced in a different way to regular type granules? DuncanHill (talk) 10:00, 26 January 2008 (UTC)
 * As you probably know coffee granules are produced by solvent extraction - the structure of the regular granules suggests very rapid solvent removal, the visibility of crystals in the gold blend suggests slower solvent removal (slower crystallisation gives larger crystals often) - so maybe the gold blend granules are produced by a slower process retaining more of the rich taste you love. ? this was a guess87.102.89.223 (talk) 18:32, 26 January 2008 (UTC)
 * I think that spray drying would tend to remove more of the 'essential oils'/'flavour compounds' in the process (a bit like steam distillation in some respects) - so may be a less good method to use - but can be carried out a lot quicker (more cheaply then) than freeze drying.87.102.89.223 (talk) 18:36, 26 January 2008 (UTC)
 * try http://ww.google.co.uk/search?hl=en&q=freeze+vs+spray+drying+coffee&meta= eg http://www.teaandcoffee.net/0105/special.htm "There are two main types of coffee solubles: those that are freeze-dried and those that are spray dried. Giestas points out that spray dried coffee is less expensive to produce than freeze dried. He says, “Due to changes in technology, over the years the gap has widened between the cost to produce freeze dried and the cost to produce spray dried, as it is now nearly three times costlier to produce freeze dried than spray dried.” Freeze dried coffee is frozen at 45-50°C below zero. “This requires lots of energy and equipment,” Giestas says, “so the cost is much higher than for spray-dried, which is processed using a vertical tower.” But the spray dry process, even though it costs substantially less than the freeze dry process, “has improved dramatically.” Giestas opines that “spray dried has kept pace with freeze dried, especially in terms of variety of flavors since each change in the spray dry process yields a change in the taste of the product.” He adds that with aroma recovery technology “we can change the entire taste profile of our product.”" - and read further this article to discover that the aroma needs to be recovered and readded after spray drying...87.102.89.223 (talk) 18:43, 26 January 2008 (UTC)
 * From http://www.asic-cafe.org/pdf/abstract/16_051.pdf "An advantage of freeze concentration is that little loss of volatile components occurs,'"
 * So just in case you're having a really slow day I'll finish by summarising that more expensive products use the more expensive freeze drying process which produces a better tasting/smelling (but slightly less soluble due to lower surface area to mass ratio) product.87.102.89.223 (talk) 18:46, 26 January 2008 (UTC)

Cool experiment ideas
Hey all, I just recently discovered the Reference desk, and it so happens that a fellow science geek and I are itching to do a non-school affiliated experiment of some kind. We've had several ideas, and we are thinking big:


 * Arc Furnace - see Theodore Gray's PopSci column here
 * Thermite - Dangerous, yes, but we are going to take full safety precautions and parental supervision, all the good stuff
 * Trebuchet - Also potentially dangerous, but same deal as above

Those are the three we came up with on our own.

Here's the question: Can you guys come up with any cool, self-satisfying, 'legal' experiments that would occupy two studious high-school brainiacs for several weeks? Also, is there anything horrendously dangerous/evil about the above ideas we had?

Thanks muchly! -- .ιΙ I n hu man 14 Ιι. 02:47, 24 January 2008 (UTC)


 * Assuming you're taking all the necessary precautions, I would note that when my school tried to show us the thermite reaction the flowerpot exploded (instead of iron dripping out the bottom into a brick). When they repeated it a week later, the new flowerpot exploded. So, prepare for catastrophic failure! Personally, I'd be tempted to build a Van de Graff generator, but that can be stupidly dangerous if handled badly.


 * Any of these plans will require large open spaces, so you can get a good safe distance from the experiment. And make sure you have plans for if something goes wrong, even if you don't think it will. Make sure you think through 'what if (something) happens?'. Do you know what you'd do? Is there anything you should have to hand, just in case? I enjoy these things, but how stupid would you feel if you hadn't planned for something that went horribly, predictably wrong? Skittle (talk) 03:39, 24 January 2008 (UTC)


 * Hows about a working replica of an ancient siege weapon? Great fun as long as you remain behind it. --TreeSmiler (talk) 04:12, 24 January 2008 (UTC)

Here are a couple things to beware of: —Steve Summit (talk) 04:15, 24 January 2008 (UTC)
 * 1) If you have no first-hand, hands-on experience with these reactions, it is difficult to know how careful you have to be. It's not enough to say "be as careful as you can be", because you don't necessarily know what to be careful about.  If you don't know what the real and likely failure modes are, you can potentially spend all your "careful" energy on something that doesn't matter that much, and totally overlook something that really matters.  So it's best if you've seen someone do these things at least once before trying them yourselves, or alternatively, if you can have someone on hand who has done it before who can tell you if you're doing anything foolish.
 * 2) What's considerably more dangerous than doing one of these reactions for the first time, is doing them for the tenth time, showing off for your friends, after you've gotten complacent about the dangers. You must always remember the dangers, and always exercise proper care.  I don't want to admit how many times I've hurt myself doing something dangerous, that I'd done dozens of times before, where I made basically the same stupid mistake that a rank idiot would make, by being careless, because I "knew" I knew how to do the thing carefully.  But it's not enough to know you're careful: you have to actually be careful.


 * Yes maybe you should do a risk assessment first (like all professional experimenters have to these days) listing all the things that could possibly go wrong and how you intend to ensure your and other peoples safety if they do go wrong.--TreeSmiler (talk) 04:20, 24 January 2008 (UTC)


 * You may wish to reflect upon the experiences of David Hahn, and learn from them. DuncanHill (talk) 04:29, 24 January 2008 (UTC)
 * Aw come on, what could possibly go wrong? -- f f r o  t   h  04:33, 24 January 2008 (UTC)

In terms of cool experiments other than blowing up or smashing things, you might want to have a look at the Old Nassau reaction. It's a crowd pleaser, especially if you do it in a lot of beakers simultaneously. And you get to play around with the delay by varying the solutions. And as long as you dispose of the chemicals appropriately, it's safe. - Nunh-huh 05:06, 24 January 2008 (UTC)


 * What about someone drinking the chemicals? Is that safe? If not you have to prevent it!--TreeSmiler (talk) 06:25, 24 January 2008 (UTC)
 * In what universe would "drinking the chemicals" constitute "disposing of the chemicals appropriately"? Certainly not this one.- Nunh-huh 08:20, 24 January 2008 (UTC)


 * I wasn't suggesting disposal by drinking the chemicals, just pointing out colored liquids might be attractive to young children or animals (esp dogs) and that precautions against anyone drinking them should be taken. Thats all. But that would come into the risk assessment (ie the probability of someone drinking them). Unlikely I admit; but possible.--TreeSmiler (talk) 18:20, 24 January 2008 (UTC)

The trebuchet is very amusing; it's not dangerous at all. What you may find dangerous are the tools you need to cut the wood. I built one for a competition once. --M1ss1ontomars2k4 (talk) 05:33, 24 January 2008 (UTC)


 * An experiment that I like (because the result is not what most people expect) is to take an insulated wire, attach a short antenna (or just strip it bare) at one end. Get that end as high up as possible (kite, balloons, water tower...).  Then, measure the voltage and amperage difference between the end of the insulated wire on the ground and a metal stake driven into the ground.  Is there a difference in voltage between the bare wire high up in the sky and ground itself?  If so, why?  Is it always the same?  Why would it change?  Is there a reason you should stay far away from the wire if storm clouds come near? --  k a i n a w &trade; 13:10, 24 January 2008 (UTC)


 * This sounds a bit like the apocryphal Ben Franklin attempted suicide experiment--TreeSmiler (talk) 00:28, 25 January 2008 (UTC)


 * That is because most people are trained from childhood stories to imagine this experiment taking place during a lightning storm. I noted that you should stay away from storms.  So, what happens if you do it on a clear sunny day? --  k a i n a w &trade; 13:28, 25 January 2008 (UTC)


 * Make a hologram from scratch. -- LarryMac  | Talk  17:36, 24 January 2008 (UTC)

Wow, thanks a lot for the feedback! We're not really looking for an overly educational experiment, unless it can be really cool to take data for. I don't want to mess around with Mercury Iodide/poisonous chemicals with the Nassau reaction, though Orange and Black do happen to be my school colors...

"But it's not enough to know you're careful: you have to actually be careful." Great advice, thanks! We have access to people that know what they are doing, and will research the experiment that we choose to do fully before we start preparing.

Yes, I've heard of the Radioactive Boy Scout, and we do not plan to mess with radioactivity/other phenomenon like that.


 * (Inserted) made that a link --Anon, 20:03 UTC, Jan. 24.

I'll add the electricity experiment to that, it sounds very neat.

Any other ideas?

-- .ιΙ I n hu man 14 Ιι. 17:59, 24 January 2008 (UTC)
 * Helium. --NorwegianBluetalk 21:54, 24 January 2008 (UTC)
 * Thanks, but no thanks. There was an interesting program on making liquid helium, though... but that'd be too much money and glasswork...-- .ιΙ I n hu man 14 Ιι.  23:24, 24 January 2008 (UTC)

U bend in steam pipes
Why are there U bends in long steam pipes that are fixed at both ends? I know this sounds like a homework question; that's because it is. Obviously I would not have asked, however, if I didn't think someone here could give me an answer better than the one I came up with. I figured that when steam doesn't flow the pipes, the pipes will contract. If the two ends are fixed, a pipe without a U bend would pull away from whatever it's attached to. However, with a U bend the bend can give the pipe some leeway. Does anyone have a better answer? --M1ss1ontomars2k4 (talk) 05:32, 24 January 2008 (UTC)


 * Your answer is basically correct. What does metal do when it get hot? Expand, contract or stay the same? If there were no U bends, what would happen to the pipe?--TreeSmiler (talk) 06:19, 24 January 2008 (UTC)


 * Your answer is theoreticaly correct, practically almost correct. What (average) temperature is a pipe when installed? what happens after it is put into service? is there a difference between steam lines and coolant lines? would you use the same approach or a different approach for a coolant line? extra credit: are there any dynamic effects? (hint: water hammer.) would a u-bend ameliorate or exascerbate dynamic effects? -Arch dude (talk) 23:41, 24 January 2008 (UTC)

colliods
why that some colliods are homogenous? —Preceding unsigned comment added by 125.60.241.164 (talk) 10:54, 24 January 2008 (UTC)
 * You mean a colloid? A mixture could be evenly mixed. DMacks (talk) 16:09, 24 January 2008 (UTC)

Two non-medical questions related to health
''Request for medical diagnosis removed. "I have X symptom, why?" is clearly such a request, regardless of the accompanying disclaimer.'' &mdash; Lomn 14:19, 24 January 2008 (UTC)

Recently, a person whom I know distantly was found pale and almost bloodless. He was taken to the hospital and is now in a stable condition. The fact is that he had no external wounds or blood loss and had suffered no physical trauma which could have caused an internal hemorrage. I don't want to ask his family as they are suffering with his illness, but I'd like to get an idea of what happened to him.


 * This is not a non-valid medical question either; the person in question is already under expert medical care and this question only seeks some information on the nature of his illness.

Thank you. -- Leptictidium (mammal talk!) 14:03, 24 January 2008 (UTC)


 * This person you know could have any number of conditions, but most likely a form of anemia. The article lists the several types of anemia that exist, as well as how to distinguish between them. (EhJJ) 15:28, 24 January 2008 (UTC)

Gas leaks
Hi. I hope I'm writing in the right place. Anyway, my stove had a clicking noise last night. It wasn't lit, but it kept making the same noise as it usually does if it's being lit. I called the fire department and they came and checked it out, but I was just wondering - I should've asked them really - if I did a right or foolish thing when I turned on the stoves following the noise. I couldn't tell if there was any leak, so I figured, it's better to burn off any gas than to leaving it hanging somewhere. But today I remember that you're not supposed to light a fire or even turn on a cellphone when you have a gas leak. So, did I do a foolish thing? Thanks. —Preceding unsigned comment added by Imagine Reason (talk • contribs) 19:51, 24 January 2008 (UTC)
 * When I last had a gas range, I was instructed to immediately vacate the house when I reported a slight smell of gas. If you've got any reason to suspect a leak (and most gas is doped with a super-smelly chemical to make leak detection easy), then evacuation is your best option and testing the stove igniter is one of the worst things you can do.  &mdash; Lomn 20:06, 24 January 2008 (UTC)


 * I agree with Lomn about the safety stuff. If in doubt, get it checked out (and it sounds like you did, well done). Having said that, my gas cooker often keeps clicking if one of the rings is very slightly on, and it can be stopped by making sure they're all completely off. The clicking is usually a piezoelectric mechanism used to create a spark to light the gas, so if it's clicking, then it's likely that any lurking gas would already have been ignited. BUT - if there is any lurking gas then you really don't want to be 'burning it off', unless you want to be losing your eyebrows and/or your roof! So if you can smell gas, don't wait around to turn things on and off, just get out and call for help. Eve (talk) 21:50, 24 January 2008 (UTC)


 * Ok, I won't light the stove next time. Question: is the piezoelectric mechanism independent of the gas valve (when you turn the dial, you're activating both, though, right)? That is, when it's making the clicking noise, is the gas automatically being released? Imagine Reason (talk) 04:13, 25 January 2008 (UTC)


 * On mine, the ignition mechanism starts going just before any gas is released, so it's just about posible to leave it clicking but not have any (much?) gas. But that will depend entirely on the design of your stove, so I have no idea. And don't rely on it. Eve (talk) 09:42, 25 January 2008 (UTC)


 * The igniter on a residential gas stove (cooker) isn't piezoelectric. (Outdoor barbecues where you push the red button and it clicks are the peizo ones.) Instead, the igniter takes mains electricity, runs it through a series if switches (one per gas tap/valve, with all the switches arranged in parallel, and then converts that mains electricity to a series of high voltage pulses. If any of the switches on the several gas taps are closed or even just sufficiently electrically leaky, the igniter may start operating, with or without the gas tap actually being open. Last time I looked, the circuit was an SCR-based relaxation oscillator.


 * Atlant (talk) 13:00, 25 January 2008 (UTC)


 * By the way, the practice of adding smelly stuff to gas, as mentioned by Lomn, was inspired by a disaster in 1937 when a major gas leak was not noticed and hundreds of children were killed. See New London School explosion.  (That's Texas, not Connecticut.) --Anonymous, 23:24 UTC, January 24, 2008.


 * !! Imagine Reason (talk) 04:13, 25 January 2008 (UTC)


 * I think you'll find that for natural gas, the added odorant is Methanethiol (Methyl Mercaptan) rather than ethanethiol.


 * Atlant (talk) 13:03, 25 January 2008 (UTC)


 * Well, I went by what it said at Thiol, plus the fact that I've heard ethyl mercaptan (another name for ethanethiol) mentioned in that context. --Anonymous, 20:08 UTC, January 25.


 * Out of curiosity, what's the danger from a cellphone? Seems rather remote. I'd be more worried about static electricity—don't wear rubber-soled shoes on the carpet—in a gas leak than a cell phone. --24.147.69.31 (talk) 04:08, 25 January 2008 (UTC)


 * It's probably easier to lay a blanket "Get the heck out!" prescription on people than to try and explain exactly what's safe and what's not in the presence of a gas leak. Tell them it's okay to use a cell phone and someone will try to use a cellphone with a dead battery; they'll then plug in the charger and...


 * Atlant (talk) 13:04, 25 January 2008 (UTC)

Firing flare guns at people
Apparently, it's considered faux pas to fire a flare gun at someone because it sets them on fire. If this were to happen, would it not be a simple case of stop, drop and roll, or does it cover the ungrateful recipient with something that makes the fire more difficult to shake? --Seans Potato Business 22:46, 24 January 2008 (UTC)


 * Emergency flares are generally designed to keep burning under hostile conditions (driving rain, high winds, extreme cold, etc.), so they're quite hard to put out. If the flare is not tangled in one's clothing, stop, drop, and roll should put the fire out -- as long as you don't roll over the flare. --Carnildo (talk) 23:19, 24 January 2008 (UTC)


 * They burn right down into the flesh, don't they? I suppose you'd have to do your best to pull it out before you stopped, dropped and rolled. Then again, that's probably not the least painful/most healthy thing to be doing either. --Kurt Shaped Box (talk) 01:33, 25 January 2008 (UTC)


 * According to the Nicole Kidman picture Dead Calm, if someone shoots an emergency flare in your mouth you should fall off a sailboat. --Sean 23:22, 24 January 2008 (UTC)


 * Do you have to be within the vicinity of a sailboat for that to work? Seans Potato Business 23:47, 24 January 2008 (UTC)


 * No, but it's easier that way. *rimshot*  —Ilmari Karonen (talk) 01:26, 25 January 2008 (UTC)


 * A search brought up this video. If it’s real the guy got off remarkably easily. Possibly the flare did not have time to light before it impacted his head. This video on the other hand is a bit more disturbing. The kid is lucky to have gotten away with only a few second-degree burns. --S.dedalus (talk) 03:42, 25 January 2008 (UTC)

Wow. How did they even get the guy to volunteer?  bibliomaniac 1  5  03:44, 25 January 2008 (UTC)


 * Boys will be boys. I'm more curious about his vowels: is that a local or a generational thing? —Tamfang (talk) 09:25, 25 January 2008 (UTC)


 * One word. Jackass. --Kurt Shaped Box (talk) 12:01, 25 January 2008 (UTC)


 * Three words, often famous last words: "Hey, watch this!"


 * Atlant (talk) 13:09, 25 January 2008 (UTC)


 * A few more:
 * "Don't worry - it's not load..."
 * "I wonder what happens when I do *this*?"
 * "It's okay, I'm a good driver..."
 * "What a cute little bear cub..."
 * "Ten bucks says that I can swallow this..."
 * "Shut up! I can reach it..."
 * "I've done this *hundreds* of times..."
 * "This is going to be so cool..."
 * --Kurt Shaped Box (talk) 17:15, 25 January 2008 (UTC)
 * At work, the oft-quoted famous last words are "what could possibly go wrong". -- f f r o  t   h  16:16, 27 January 2008 (UTC)
 * At work, the oft-quoted famous last words are "what could possibly go wrong". -- f f r o  t   h  16:16, 27 January 2008 (UTC)


 * You forgot "Hold my beer a sec..." 78.32.138.240 (talk) 00:00, 29 January 2008 (UTC)