Wikipedia:Reference desk/Archives/Science/2010 May 27

= May 27 =

Cheetah speed
a cheetah is the fastest land animal and can achieve a peak velocity of 100 km/h upto a distance less than 500 m.if it spots its prey at a distance of 100 m then what is the minimum time it will take to catch its prey if the average velocity attained by it is 90 km/h ? —Preceding unsigned comment added by 117.205.176.131 (talk) 00:33, 27 May 2010 (UTC)
 * Probably not as fast as you could solve this simple math problem on your own. Please do your own homework.  -- Jayron  32  00:37, 27 May 2010 (UTC)
 * Maybe the confusing part is the wording of the problem which is pretty bad! Assuming the subject is the cheetah every time they refer to "it" which makes more sense, this problem is very simple: How long does it take to travel 100m at a velocity of 90km/h. If you have a problem with this, you need to re read the chapter of your text book. Vespine (talk) 00:55, 27 May 2010 (UTC)
 * Do we need to account for the time it takes for the cheetah to accelerate to 90 km/h? I've also added a header ~ A H  1 (TCU) 01:37, 27 May 2010 (UTC)
 * Nope. It clearly states "average velocity" which takes all changes into account, including the acceleration from stop.  Its as simple as finding out how long it takes to run 100m at 90 km/hr.  -- Jayron  32  01:44, 27 May 2010 (UTC)
 * You don't have enough information to give the minimum time. The prey could turn and run towards the cheetah, and you aren't told how fast the prey runs. --Trovatore (talk) 01:48, 27 May 2010 (UTC)
 * I remember getting questions this poorly worded all the time. Generally you are expected to make the fewest possible assumptions, if they didn't explicitly say the prey moves then you assume the prey doesn't move. It's a maths question not philosophy. The point about the prey and all that other stuff about top speed and 500m and all that are red herrings there to throw off the "logical" part of your brain. ;) Vespine (talk) 02:02, 27 May 2010 (UTC)
 * I assumed that the second "it" referred to the prey, and the prey attained a speed of 90 km/hr, with the cheetah chasing it at 100 km/hr, in which case the question is quite different (though still easily solvable). It is a poorly worded question, though. Buddy431 (talk) 03:06, 27 May 2010 (UTC)
 * But the 100 km/hr is stated as a peak velocity Nil Einne (talk) 03:31, 27 May 2010 (UTC)
 * That's the bad wording i was talking about. I think it makes more sense if you just assume the cheetah as the object of the question all the way through. Any time it says "it" or "its" assume cheetah. I think the question is essentially "How long does the prey initially have to react if the cheetah starts from 100m and can obtain an average speed of 90km/h over that distance." Vespine (talk) 04:14, 27 May 2010 (UTC)
 * An interesting thought, Cheetahs like to trip their prey as it runs. Would they even go after an gazelle that stands its ground?  65.121.141.34 (talk) 13:10, 27 May 2010 (UTC)

Two methods, two solutions
You have identical objects at 300K, 300K, and 100K that are perfectly insulated from their surroundings. Using heat engines, what's the highest temperature to which any object can be raised?

If you assume that the 300K and 100K objects do work on the other 300K object at the Carnot efficiency, you get 354K. If you assume that the change in entropy is 0, you get 400K. Both approaches seem equally valid to me. Why do they give different answers? --99.237.234.104 (talk) 01:11, 27 May 2010 (UTC)


 * I don't fully understand your question, but heat pumps (is that what you mean by heat engine?) waste energy - so does that wasted energy count toward raising the temperature? Ariel. (talk) 03:08, 27 May 2010 (UTC)


 * Would you care to share your calculations with us to make our job of pinpointing any mistakes a little easier? Dauto (talk) 04:46, 27 May 2010 (UTC)
 * The calculations are quite simple, but long and tedious. Anyhow, here they are.
 * The entropy method: Suppose the final temperature of one 300K one 100K objects is T1. Suppose the other 300K object is raised to T2.  2T1+T2=300+300+100=700 due to conservation of energy.  dS=dQ/T=c*dT/T=clnT, so for all three objects, the condition that total entropy change = 0 is equivalent to lnT1/100 + lnT1/300+lnT2/300=0.  Solving the two equations gives T2=400K.
 * The brute force method: Suppose a 300K and a 100K object are used as the heat source and sink for a Carnot engine, and that the engine's work is used to raise the other 300K object's temperature.  W=Qh(1-Tc/Th) and Qc=Qh*Tc/Th for a Carnot engine.  Qc=Qh*Tc/Th is equivalent to -c*dTc=c*dTh*Tc/Th, or dTc/Tc=-dTh/Th.  Solving this gives Tc*Th=T1T2, where T1 and T2 are the initial temperatures (100K and 300K).  W=Qh(1-Tc/Th) is equivalent to dW=-c*dTh*(1-T1T1/Th^2).  Solving this equation gives W=c(sqrt(T1)-sqrt(T2))^2.  Setting this equal to the heat absorbed by the other 300K object, c*delta-T=c*(sqrt(T1)-sqrt(T2))^2 and delta-T=(sqrt(T1)-sqrt(T2))^2.  This gives delta-T=54 degrees and final temperature=354K.  --99.237.234.104 (talk) 05:07, 27 May 2010 (UTC)


 * The first method is not correct. The carnot cycle is reversible and does not increase the entropy but the subsequent conversion of the work produced by the cycle into heat delivered to the third system is not reversible and does increase entropy. dS=0 is incorrect. Dauto (talk) 05:55, 27 May 2010 (UTC)


 * On a second thought, if you are also allowed to use heat pumps (which are nothing more then heat engines running backwards), then it is possible to dump the work in the third body reversibly by pumping heat from one of the colder bodies into the hot one using the work extracted from the heat engine attached to the two fist bodies. If you are allowed to do that then the first method gives the correct answer. Dauto (talk) 14:33, 27 May 2010 (UTC)
 * Thank you, that makes sense. Yes, you're allowed to use heat engines, heat pumps, refrigerators, and absolutely anything else in the world except outside energy.  --99.237.234.104 (talk) 03:27, 28 May 2010 (UTC)

Shaker
What are the ingredients in the shaker?174.3.121.27 (talk) 06:24, 27 May 2010 (UTC)
 * [[image:Foodstuff-containing-Zinc.jpg|thumb]] (I embedded the image for you.) I think it's Crushed red pepper. Ariel. (talk) 07:43, 27 May 2010 (UTC)
 * Agreed, it's crushed red pepper. Comet Tuttle (talk) 23:08, 27 May 2010 (UTC)

reproduction in plants
Life span of May fly is 01 day while that of Banyan tree can be 200 yrs. What message do you get from this data concerning BMR (Basic Metabolic Rate)? —Preceding unsigned comment added by 180.215.248.143 (talk) 08:35, 27 May 2010 (UTC)


 * Nothing. I get no message about BMR from that at all. Ariel. (talk) 08:50, 27 May 2010 (UTC)


 * Adult mayflies may only live for a day but their larvae live for several years. Plants do have a lower metabolic rate compared to animals as they don't have to move. Have you read Metabolic_rate? Incidentally 200 years is nothing - check out the bristlecone pine. 86.7.19.159 (talk) 09:08, 27 May 2010 (UTC)

terminology for the concept of group immortality
. What is the terminology for the concept of group immortality? —Preceding unsigned comment added by 180.215.248.143 (talk) 08:37, 27 May 2010 (UTC)


 * Hu? I don't understand the question, please rephrase it. Ariel. (talk) 08:50, 27 May 2010 (UTC)
 * The collective term would be "immortals" ?77.86.125.207 (talk) 10:01, 27 May 2010 (UTC)


 * Species? 92.15.30.36 (talk) 17:20, 28 May 2010 (UTC)

You need to use a better translator and more words to describe your question. http://translate.google.ca/#

Falling under the category of having immortality describes those that do not decay towards death and/or those that can not be killed, ideally living forever, but these are always qualified by how immortality is bestowed, for example Adam & Eve were immortal until God left them, therefore it was a "conditional immortality." 24.78.167.139 (talk) 05:17, 29 May 2010 (UTC)

Synthetic life: human health-care implications?
Could the recent "digitally programmed" loops of DNA used to create synthetic bacteria be scaled up to create and repair the complex DNA in a human, for example to create new heart or hair cells? Or are macroscopic problems in tissue engineering a bigger block to replacing damaged body parts? [Trevor Loughlin]80.1.88.1 (talk) 10:43, 27 May 2010 (UTC)


 * I think we're far too early in this technology to really know what it's total health care potentials will be or whether there will be insurmountable difficulties. Don't expect to see direct health care implications for another 10-15 years, which is the general turn-around time for cutting edge technology before it becomes something "tamed" enough to start using in actual patient settings. --Mr.98 (talk) 13:17, 27 May 2010 (UTC)
 * Technology to create or regrow damaged body tissue already exists, though it too is still in its infancy. — Æµ§œš¹  [aɪm ˈfɹ̠ˤʷɛ̃ɾ̃ˡi] 17:37, 27 May 2010 (UTC)


 * As impressive as the "synthetic cell" accomplishment is, it took Venter's team about 15 years to develop the technology to where it is right now. They are many years away from being able to apply this to something on the scale of a human.  First, as far as I can tell from reading the papers, the ability to synthesize a genome from scratch using current techniques will reach a certain size limit that depends on how much DNA the yeast cells can reliably recombine.  I'm not sure what that limit is, but it will almost certainly be far below the size of the average human chromosome.  Second, the researchers don't really understand the mechanism by which the genome transplantation works, and it isn't even clear if the technique will work in species other than Mycoplasma.  I don't think it is realistic to expect that someone will try to synthesize an entire human genome and transplant it into a recipient cell for the purpose of tissue regeneration... we already have lots of experience with stem cells that will probably get there much faster.  More likely they will start by synthesizing novel types of microbes that can do useful things. --- Medical geneticist (talk) 12:03, 28 May 2010 (UTC)

Selenic acid
How can chlorine be used to oxidize selenious acid to selenic acid, itself being reduced to chloride ions? The article also says that selenic acid can oxidize chloride ions to elemental chlorine. Is it an equilibrium? Thanks. --Chemicalinterest (talk) 12:30, 27 May 2010 (UTC)
 * The article clearly states you have to remove the HCl byproduct to drive the reaction. The statements have footnote references. One of them, a free abstract of an article, states that there is also a temperature effect. DMacks (talk) 15:12, 27 May 2010 (UTC)


 * The reaction must be an equilibrium since it is described going both ways, the textbook source - available in part on line gives no further clues see page 544 77.86.125.207 (talk) 16:57, 27 May 2010 (UTC)

speeding
whats a good place to take my car up to 100 mph ? i tried my street late at night when no one was around but its not long enough i only get up to 70 mph. i dont want to do it on the highway cause i might get pulled over. whats a good secluded place to go to 100 mph ? —Preceding unsigned comment added by Tom12350 (talk • contribs) 13:40, 27 May 2010 (UTC)
 * Find a sanctioned dragstrip in your area if you think 1/4 of a mile is enough distance to get up to the speed you want. Outside of that you have few legal options unless you want to drive to a dry lake.  --Jmeden2000 (talk) 13:51, 27 May 2010 (UTC)


 * FWIW, you will need a car with very good acceleration to get up to 100 in a quarter mile. My, uh, friend, has had luck using short spurs between highways where they don't bother with speed traps.  In a place where this was perfectly legal, of course.  Also is your car in good shape?  How are your tires and brakes?  You don't want to travel at high speeds in a car that's not up to the job.  Friday (talk) 13:59, 27 May 2010 (UTC)


 * Along the lines of illegal options, though, trying this on the highway is much much safer than on surface roads. You'd be on a road more closely intended for 100 MPH and driving in one-way traffic moving more closely to 100 MPH.  The former means you're less likely to have a one-car accident, and the latter means that in addition to reducing the chance of a two-car accident, you'll put the closing speed of the collision closer to 30 MPH than to 130 MPH.  Finally, in the event that the police take notice of you, you'll all but certainly get more lenient treatment trying this on the highway.  Now, all that said, follow Jmeden's advice above and find a dragstrip.  And absolutely never try this again on a two-way street. &mdash; Lomn 14:05, 27 May 2010 (UTC)
 * Go to Germany and drive on the Autobahn on a day where the traffic is incredibly light. They have no speed restriction there, assuming it is considered safe to do so. It's recommended you don't go above 85mph, but they aren't going to pull you over because you're doing more. 14:14, 27 May 2010 (UTC)Regards, --— Cyclonenim | Chat


 * I think it is an incredibely irresponsible thing to try to speed to 100mph in a city street late at night. I sincerely hope the police pulls you over. Dauto (talk) 14:23, 27 May 2010 (UTC)

it wasent a city street it was a residential street at like 3 am no one was on it. —Preceding unsigned comment added by Tom12350 (talk • contribs) 14:28, 27 May 2010 (UTC)


 * Yeah, yeah, yeah... I hope you get pulled over. Dauto (talk) 01:06, 28 May 2010 (UTC)


 * Wow you aren't going to win friends with that argument... not to sidetrack this but people (like me) from time to time walk their dogs late at night (even at 3am) and would enjoy not having to dodge a car going ~100mph... At that speed you likely won't likely realize your observation of "no one was on it" was wrong until they are under your car.  --Jmeden2000 (talk) 14:32, 27 May 2010 (UTC)
 * Additionally at speeds like that your margin of error is very low, and being surrounded by houses full of people is pretty dangerous. A residential area has a lot of people and a lot of property in it. Don't drive recklessly there even at 3am (when there are more people around than you probably realize). Go somewhere where there aren't any people at all so that if you lose control and total your car you don't kill anyone else in the process. In these situations it is not the "normal" that you prepare for and worry about, but the freak accident. Take some responsibility. --Mr.98 (talk) 14:47, 27 May 2010 (UTC)

i drove down the street first to make sure no one was walking and it also had a sidewalk. im not here for a moral lesson just give me advice how to do it. what do you mean by "short spurs between highways where they don't bother with speed traps. " where is that. —Preceding unsigned comment added by Tom12350 (talk • contribs) 14:42, 27 May 2010 (UTC)
 * On a residential street you're probably going three times the speed limit. If they catch you doing that, they won't bother writing a ticket. Your car will be towed and impounded, and you'll be handcuffed and put in prison. (Question : Are you certain that no one living in that neighborhood is a cop? Would you bet the next couple years of your left on it?) APL (talk) 15:58, 27 May 2010 (UTC)


 * Well I've had my car up to 100 mph on a UK motorway (quite by accident - I'd just bought it and didn't realise I didn't have to have my foot down as far as I was used to in my old car, your honour). I don't think you're in the UK though! Seriously, don't drive at that speed in a built-up area. While there may not be people walking around, if you lose control of your car (and at that speed it's ludicrously easy - maybe hitting a kerb will do it) then you may well land at first floor level in someone's house. I'm pretty sure they won't appreciate being woken by some twat parking a car in their bedroom - and I'm also pretty sure you wouldn't be alive to hear them scream at you for doing it. --TammyMoet (talk) 14:58, 27 May 2010 (UTC)


 * Find a local Track day event, and do it safely and legally. A residential area at 3am is the worst idea, people going out are likely to be making emergency trips (sick kid on the way to hospital), walking the dog, or cycling because its cool and safe. -- Q Chris (talk) 15:07, 27 May 2010 (UTC)
 * I recommend I-76 in eastern Colorado. A cop followed me for a couple miles (I was driving 95 mph) and finally just passed me.  There is pretty much nobody out there.  One thing to note, the road is not great, and I was not comfortable going above 110 on it.  65.121.141.34 (talk) 15:17, 27 May 2010 (UTC)


 * If you're determined to do it illegally, I don't see what the big deal is. Go out on the freeway and do it. You didn't need us to tell you that a good place to drive fast is the freeway? Surely you've noticed that a lot of people seem to do 80-90 on a regular basis? APL (talk) 15:58, 27 May 2010 (UTC)


 * You drove down a residential street, saw no one so you presumed there was no possibility someone would be out on the road at that time? You aren't aware then that people live in houses and yes, they do sometimes come out of their houses at 3 am and walk along their street after you 'checked for people', and no, they don't monitor to see if there's some person driving along the street to check if people are walking and presume that said person is later going to drive along the street at 100mph so they should wait until said person has finished driving along the street particularly given that said person doesn't sound like the sort of person likely to be able to safely drive at 100 mph so could easily lose control and kill them for the 'crime' of walking along the street after said person had driven along the street to look for people (or perhaps simply not being seen by said person).
 * Or for that matter you never considered that you could lose control and hit a house killing someone in it in process (not outside the realms of possibilities if you're driving at 100mph).
 * And yes, it is personal because although I don't live in the US so thankfully I'm unlikely to ever meet the OP, I do sometimes go out late at night (I don't drive so I'm either walking or cycling) and while I'm aware there are always going to be some risks, it's quite a different thing to meet someone who openly admits he's one of those security risks to people like me. Since I'm usually going to some shopping complex the latest tends to be slightly after midnight since that's the latest their open here, at Christmas time but it's always possible I would go out at that time, why shouldn't I? But apparently people like me don't matter because hey I wasn't supposed to be out so late and if I was I was somehow supposed to make sure people like the OP see me before they go driving along the street at 100mph. So don't bother telling me off for WP:NPA or WP:Civility, this message is well and truly deserved.
 * Nil Einne (talk) 19:41, 27 May 2010 (UTC)

what do you mean by "short spurs between highways where they don't bother with speed traps. " —Preceding unsigned comment added by Tom12350 (talk • contribs) 17:44, 27 May 2010 (UTC)
 * See Spur route. I'm not sure what the difference is between a Spur Route and a Connector. It may just be regional dialect.
 * I'm not confident that they're necessarily ignored by highway patrol. APL (talk) 20:04, 27 May 2010 (UTC)
 * While it depends on the highway, your local police and other factors, if you regularly drive along a highway you are probably aware of the favourite spots for cops so the OP's best bet is to find one of them and try it. Perhaps a spur route perhaps just a part of the highway that doesn't tend to be monitored much (perhaps far from the main urban areas). Ultimately as APL said earlier, if you're determined to do it illegally, you can't expect a guarantee you won't be caught. Nil Einne (talk) 20:13, 27 May 2010 (UTC)


 * Please don't ever again do anything idiotic like drive at 100mph down a residential street, no matter whether or not you think there's nobody there. You may not know that in the US, in most states, exceeding 100mph is a felony, and I would hope the prosecutor would pile on charges of reckless endangerment and actually send you to prison for 3-5 years.  Comet Tuttle (talk) 23:12, 27 May 2010 (UTC)
 * Actually I just read the article about reckless driving: in most states it's a misdemeanor punishable by 5 to 90 days in prison and up to $1000 in fines (and in some states a mandatory license suspension for 6 months), but can become a felony if you hurt someone. 67.170.215.166 (talk) 02:31, 29 May 2010 (UTC)
 * I think you'll find that if you find a local police station and drive past a few times at 100 mph, the police will consistently ignore you so you will not have any problems with getting arrested. --Phil Holmes (talk) 11:24, 28 May 2010 (UTC)
 * I think you'll find that if you find a local police station and drive past a few times at 100 mph, the police will consistently ignore you so you will not have any problems with getting arrested. --Phil Holmes (talk) 11:24, 28 May 2010 (UTC)


 * In Montana there's no speed limit on freeways in the daytime, so you could go as fast as you want (traffic and road conditions permitting). Only place where it's legal to drive faster than 100 -- anywhere else it would be considered reckless driving. 67.170.215.166 (talk) 02:02, 29 May 2010 (UTC)
 * That is no longer true. The maximum speed limit in Montana is now 75 mph; this has been the case since 1999. TenOfAllTrades(talk) 16:07, 30 May 2010 (UTC)

Applied Logic - What is this?
Do you have any idea what this sign means? In cleaning out my lab, I found it behind a solvent locker. It may have been there for decades. ike9898 (talk) 15:08, 27 May 2010 (UTC)
 * The first thing to decide, is whether its supposed to read
 * "not quite physics envelope but close" or
 * "not quite envelope physics but close".
 * I'd say the spacing is ambiguous, it could be read either way. Googling "envelope physics", yields almost exclusively hits containing "back of the envelope physics", which doesn't seem to make much sense without the introductory "back of the", at least not to my non-native ears. Googling "physics envelope", on the other hand, yields hits like "Adult tarantulas are pushing the physics envelope with exoskeleton size & so are very susceptible to damage from falls", there's a Nature article called "pushing the physics envelope" (which I can't read now, as I'm writing from my home PC). Another hit reads: "Does no one push the Physics Envelope anymore? Have we really reached the highest point in the helicopter design...". So it appears to me that "physics envelope" means "limits of what physics can achieve".


 * So I'd interpret it as: APPLIED LOGIC gets you not quite to the limits of what physics can achieve, but close. --NorwegianBluetalk 16:04, 27 May 2010 (UTC)
 * I think it is likely that it is supposed to read "not quite envelope physics but close, with "back of the envelope physics" being what it is referring to. See back-of-the-envelope calculation, it means "a rough calculation", as doing physics on the back of an envelope is less accurate than using a computer or something.   So, applied logic is not quite as (in)accurate as doing physics calculations on the back of an envelope, but it is close.  I guess somebody didn't like applied logic.  --Cerebellum (talk) 16:40, 27 May 2010 (UTC)
 * I agree with the above (2 makes sense) ie
 * Hitting things with clubs < Handwaving < Applied logic < Back of envelope calculations < Full solution of multi-electron shrodinger equation ..etc...77.86.125.207 (talk) 17:01, 27 May 2010 (UTC)


 * Question - did the department you're at used to have an "Applied logic department"? - might have been a joke comment on the quality of research they did there, or something.77.86.125.207 (talk) 17:02, 27 May 2010 (UTC)
 * This building is highly interdisciplinary, and changing all the time, so figuring out if applied logic was being used at some undefined point in the past would be a significant task. ike9898 (talk) 18:52, 27 May 2010 (UTC)

"Envelope physics" means "physics that pushes the envelope" -- the envelope being the boundary between the possible and the impossible. So it's basically a bit of humor that means "we're not quite out at the bleeding edge but we're close to it". Looie496 (talk) 17:44, 27 May 2010 (UTC)

I'm not sure this discussion has converged on a single explanation, but I've certainly got a better idea than I did before. Thanks, everyone! (Further thoughts welcome) ike9898 (talk) 19:00, 27 May 2010 (UTC)


 * A bit off topic, but around the edges of the sticker one side is tinted blue and the other side orange. This effect appears visually as well for the edges of sources of light or bright reflections of light. ~ A H  1 (TCU) 18:43, 30 May 2010 (UTC)

Aircraft HVAC
How is temperature controlled onboard a commercial airplane ? I'm guessing that they lack heaters and A/C, but rather use the excess heat from the jet engines and the cold from the air at altitude to control temps. However, neither of these are available on the ground, and this might explain why the passenger compartment quickly overheats when a plane is stuck on the ground. (I suppose it could also get cold in very cold weather, at night, with an almost empty plane, where solar heating and heat given off by passengers would be minimal.) Also, has there been any thought to providing a truck that could drive out to a plane stuck on the tarmac, and hook it up to provide an external A/C or heat source ? Obviously the plane would need some place to connect to. I suppose the passenger door(s) could be opened and air could be pumped in one flexible duct and out another. I was on a plane that was only stuck like this for 15 minutes, and it got hot, so I wonder just how hot they get after many hours like this ? I've also noticed that they don't seem to overheat when parked at the gate, so do they have some external hook up they use to prevent this from happening there ? StuRat (talk) 16:47, 27 May 2010 (UTC)


 * Commercial airliners do have air conditioning units. Heating is achieved with an engine-bleed heat exchanger. When an aircraft is on the ground, with the main engines not running (but with passengers boarded), the auxiliary power unit is run, which has the same effect - even the APU has enough juice to run both heating and A/C. When at the stand, some airports have power hookups.  I too have spent some uncomfortable time at EWR in the Summer on a plane with no APU at a stand with no hookup. After a (long) while they came up with some truck, which I think had a generator to do the job of the APU. Refs: http://www.b737.org.uk/airconditioning.htm http://www.boeing.com/commercial/cabinair/ecs.pdf -- Finlay McWalter • Talk 17:23, 27 May 2010 (UTC)

Gregory-Madhava Series
(moved to Ref Desk/Math) --pm a 18:15, 27 May 2010 (UTC)

Fungus
“Any organic material kept in moist and dark conditions gets infected with fungus, although there was no sign of fungus prior to it.” How fungus does make it possible, although it is a microbe? —Preceding unsigned comment added by 180.215.248.62 (talk) 18:20, 27 May 2010 (UTC)
 * I heard that mold spores are floating all over in the air. When they find a good environment, they attach to it and multiply. --Chemicalinterest (talk) 18:34, 27 May 2010 (UTC)


 * The original statement is clearly untrue - there must be either fungus or fungal spores in the air or in the original organic material in order for a fungus 'infection' to happen - in which case, the statement that "there was no sign of fungus prior to it" must be false. Perhaps there were no visible signs - but under close enough analysis, some kind of fungal material had to be present at the outset. SteveBaker (talk) 20:07, 27 May 2010 (UTC)
 * I think it means no visible sign, since there are always fungal spores around. We're all exposed, all the time, to to fungal spores, and if they do find somewhere moist area then they can settle. I don't see how dark conditions matter, fungi aren't damaged by light, at least not any of the fungi I've heard about. Regards, --— Cyclonenim | Chat 21:22, 27 May 2010 (UTC)
 * There was no mention that the organic material was kept in an air-tight container, only that it was kept dark and moist. An unlit basement would count, and there could be wet rot, bread mould, and other similar organisms in the air. CS Miller (talk) 14:24, 28 May 2010 (UTC)


 * First of all, fungus is not the same as a microbe (microorganism). More precisely, some fungi are microorganisms, and some are not; some microorganisms are fungi, and some are not. Second, as people have already said above, fungi do not "spontaneously generate", they grow from spores. The theory of Spontaneous generation has indeed been disproved for at least 200 years now. (On the other hand, the life on Earth may well have spontaneously generated in the first place; but that took a few billion years, see abiogenesis; and the first life forms were certainly nothing like the modern fungi). Third, not all organic material kept in moist and dark conditions gets infected with fungi. See putrefaction, decomposition, saponification, and fermentation. --Dr Dima (talk) 21:38, 27 May 2010 (UTC)


 * I don't think saponification has anything to do with fungi? or very much to do with stuff going off in the pantry?77.86.125.207 (talk) 23:09, 27 May 2010 (UTC)


 * That's my point exactly. I was trying to explain that not all organic material kept in moist and dark condition gets infected (and decomposed) by fungi. Saponification is an example of such non-fungal process. Putrefaction is another example of a non-fungal process (putrefaction is mostly carried out by anaerobic bacteria.) --Dr Dima (talk) 06:55, 28 May 2010 (UTC)

smoke
wouldent the people in this vid get really stoned from the smoke in this vid

http://www.youtube.com/watch?v=0TWy7ZScURU&feature=channel —Preceding unsigned comment added by Tom12350 (talk • contribs) 19:05, 27 May 2010 (UTC)


 * (This is a vid of opium poppies being destroyed by burning them.) I think that a: people are not standing in the smoke, and b: the flames might be hot enough to destroy the active ingredients. Regular smoking is not a flame, but rather embers which are cooler than a flame. Ariel. (talk) 21:45, 27 May 2010 (UTC)
 * Note that the burning includes all parts of the plant - not just the resin that contains the opium - thus it would be unpleasant to breath in. (like inhaling the smoke from burning straw). 77.86.125.207 (talk) 23:08, 27 May 2010 (UTC)

Lead dissolution
How would you dissolve lead metal to form lead salts using household chemicals? Thank you. --Chemicalinterest (talk) 19:08, 27 May 2010 (UTC)
 * I would guess that bleach would do it, especially in the presence of strong base, which solublises both Pb2 and Pb4 salts.
 * The reaction is postulated as being a possibility in the corrosion of lead pipes, but doesn't seem to be certain.77.86.125.207 (talk) 19:31, 27 May 2010 (UTC)
 * Alternatively a route to lead oxide (which should readily react with acids to form salts) - is by heating and stirring molten lead to effect the oxidation of lead - which can be removed from the surface.
 * You know lead is considered poisonous in general?77.86.125.207 (talk) 19:33, 27 May 2010 (UTC)
 * In theory, any acid should react with lead to form salts, such as:

Pb + H2SO4 → Pb SO4 + H2
 * However, lead is just above hydrogen on the reactivity series, so an acid-lead reaction could take a very long time. --The High Fin Sperm Whale 19:37, 27 May 2010 (UTC)
 * I have some ancient lead solder that I dissolved in hydrochloric acid, leaving the lead and rosin behind. (I used the tin(II) chloride formed as a reducing agent). I was wondering if there was any way to form lead compounds from the lead powder left behind. --Chemicalinterest (talk) 20:08, 27 May 2010 (UTC)
 * Are you sure that it was lead solder and not tin solder? 'Cause lead chloride is only slightly soluble in HCl -- did you use a big excess of acid? 67.170.215.166 (talk) 07:02, 28 May 2010 (UTC)

What about using acetic acid from vinegar? Lead(II) acetate is well known and can apparently be synthesised by reaction of acetic acid with lead(II) oxide, PbO. You could first convert Pb to PbO by blasting it with a blowtorch or something.

Ben (talk) 20:43, 27 May 2010 (UTC)
 * No blow torch needed. As you have already lead powder you have a high surface area - the surface should be lead oxide already - dissolve the surface layer with acid, filter, wash, allow to dry - divide the powder again (allow time for another oxide layer to form) .. repeat. However this will produce finer and fine lead powder - which is not a good idea health wise.77.86.125.207 (talk) 21:06, 27 May 2010 (UTC)

Sodium amalgam
Is the reducing properties of sodium amalgam relevant to the sodium content, or the mercury being in a negative valence. Or is it considered covalently bonded? --Chemicalinterest (talk) 20:15, 27 May 2010 (UTC)
 * The reducing power will always increase with concentration.. (avoiding the issue of what the thing in sodium amalgam actually is .. article claims Na2Hg - but I wouldn't count on it.) 77.86.125.207 (talk) 21:31, 27 May 2010 (UTC)
 * Possibly different compounds will be formed depending on the amount of Na - suggests NaHg, Na2Hg ,Na3Hg -not sure if this is right - there are definately a lot of different species
 * Na2Hg definately exists and is an Intermetallic - it's somewhere between a normal metal alloy and a salt - may look like a 'shiny ceramic'. The bonding can be considered primarily metallic (which is similar to a non directional covalent bond) but with polar character too - additionally the structures of isolated amalgams may not have all that much bearing on what may often be a solution of Na in Hg (or a mixture of different sodium/mercury intermetallics)- you coukd think of it as simply Na in solution in Hg, with some charge transfer from the Na to the surrounding Hg's - which will form a coordination shell similar to that found when Na+ is in solution in water solvated to Hg (it wouldn't affect the understanding of the redox chemistry much)- in general the actual situation in any Na/Hg mixture is complex.77.86.125.207 (talk) 21:38, 27 May 2010 (UTC)


 * The main thing to remember is that its action is by electron transfer, and that the electrode potential is not the same as that of pure sodium (amalgam is less reducing).

Crystal structures of NaHg, Na2Hg, Na3Hg etc have been determined, so these intermetallics are stable.

Ben (talk) 11:27, 28 May 2010 (UTC)

Crocodile Poo
We posted here earlier, but were unfortunately dismissed. Allow us to rephrase our question so that your dilettantes are able to understand, and can hopefully help without deleting this post. Do crocodiles leave solid excrement or do they lose waste primarily through the skin and fluids. THANK YOU. —Preceding unsigned comment added by 129.67.38.99 (talk) 22:15, 27 May 2010 (UTC)
 * - yes they shit.77.86.125.207 (talk) 22:25, 27 May 2010 (UTC)
 * Your google search helps very little. —Preceding unsigned comment added by 129.67.39.207 (talk) 23:17, 27 May 2010 (UTC)
 * You're supposed to click on the links and read them.77.86.125.207 (talk) 23:22, 27 May 2010 (UTC)
 * Given that people respond to you out of their goodwill, you could be a bit nicer, though when all google search returns are fosilized crap one may indeed wonder how that helps to find out something aout modern animals. The thing with crocodiles and such is that those are not animals of one species and charecteristics of diffrent spiecies may vary. The article says that they have no urine bladder, so it is more likely they don`t urinate. The fact that there is fosilized shit and unusal characteristics (such as getting rid of all the waste products by other means than shit) usualy are pointed out suggests that they shit. Also if you google crocodile anatomy you`ll notice that they have a cloaca, which is meant for sex, shit and urine, by looking up that, I found site on captive care of crocodiles, maybe you`ll find something there as people who keep them are quite likely to get up close and personal with crocodile shit, if it exists, their guide on determening the pet`s sex hints that they may shit if someone examines their butts  Xil  (talk) 23:56, 27 May 2010 (UTC)
 * Unless your results are majorly different from me, you don't even need to click the links. The fact that a book is talking about "Coronavirus Coronavirus-like particles were found by transmission electron microscopy in negatively stained faeces of four 2-3-year-old crocodiles from a ..." and a research paper is talking about "found by electron microscopy in the faeces of farmed Nile crocodiles in South Africa"  and a FAQ on Crocodilian Captive Care says "The stool can often be very soft and difficult to collect - a croc's  digestive system is very thorough. The faecal sample will enable the..."  and someone in a journal says "One of the highlights of this hour is to have pointed out to us crocodile faeces!"  is evidence enough that they shit. So I don't understand how the Google search 'helps very little' to anyone who bothered to actually take a glance thru it. And that's even if you ignore the fossilised faeces Xil discusses above that there are images of and is mentioned in "The 15 million year-old fossilised faecal matter, or coprolites, are each the size of a fist and bear clear impressions of prehistoric shark ..."  what's the second link for me. Of course, if you have any abouts that these are talking about crocodile faeces, you can click them to see it in context. Nil Einne (talk) 00:08, 28 May 2010 (UTC)


 * My previous response and another was removed as it also complained about linking to Google and treating the OP poorly, but I feel the response had substance and the previous poster did not answer what appears to be the OP question.


 * All the papers and coprolites say that solid excrement exists, but what is it? Does it excrete with urea like in birds? A very very difficult online hunt provides zero images of actual fresh croc dung, but does give a nice description of liquid excrement (Google books: Huchzermeyer. "Crocodiles: biology, husbandry, and diseases." Look up excrement or urine). What's interesting is that there is in fact very little urea in the urine, which is in direct contrast to birds (the white stuff in the poop is urea). I'm sad that for crocodiles and reptiles in general there is very little information online and surprisingly no pictures. Surprising because there's an entire human-excrement appreciation website called ratemypoo.com. SamuelRiv (talk) 16:36, 29 May 2010 (UTC)
 * Its a very serious breach of etiquette to remove people's comments, especially when it is to avoid criticism. Who did it? 92.28.242.45 (talk) 19:00, 29 May 2010 (UTC)
 * See Wikipedia_talk:Reference_desk - which is the correct place to place any criticism.94.72.235.30 (talk) 15:34, 31 May 2010 (UTC)