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September 16

Rare earth metals

Why do the rare earth metals behave very chemically similar? Since they react almost identically to virtually all chemicals, how do manufacturers separate them from each other? --71.153.45.75 (talk) 00:23, 16 September 2010 (UTC)

See Periodic table and especially f-block. All rare earth elements share the same electronic configuration of lower orbitals (s, p, d) and differ only in their f-orbitals. Separation was very difficult in the past (fractional crystallization), but nowadays it's done by preparative column chromatography, which is quite efficient and can be easily automated. Alfie↑↓© 00:47, 16 September 2010 (UTC)

Why don't the differing f-orbitals significantly affect their chemistry? --71.153.45.75 (talk) 00:49, 16 September 2010 (UTC)

It has to do with the fact that f orbitals are relatively deep compared to the 6s and 5d valence electrons. These deep f orbitals do not participate in chemical reactions to a significant degree leading to their chemical similarity. Rigel0 (talk) 01:12, 16 September 2010 (UTC)

(edit conflict) See electron shell and sort the table by the last column "Group". The f-orbital is the the one starting with 18 electrons for Lanthanum. Chemical bond depends on the outermost shell – these electrons are farest away from the nucleus. In rare earth elements the f-electrons are shielded by these outer electrons (i.e., they don't interact with other elements forming chemical compounds). Since the number of these electrons is identical, the chemical compounds of different rare elements also show similar properties (they are essentially different only by their molecular mass). See all RE articles and have a look at the right box (Electrons per shell). You see the shell electrons: s, p, d, f,... which is 2, 8, 18, 18→32 for the lanthanides. Now click on the image. What do you get? Alfie↑↓© 01:34, 16 September 2010 (UTC)

Ten-year late clarification: only true for 4f which has no radial nodes and is relatively small. 5f is bigger and participates more, which is why actinoids are more different from each others than lanthanoids are. Double sharp (talk) 10:33, 14 December 2020 (UTC)

is bleach compatible with any Lewis acids?

I wish to guide and activate bleach oxidising's properties while at the same time making it more selective. Does adding Fe(III) chloride to bleach simply generate chlorine? (It's mostly chemistry on paper but assume I'm doing this with a fume hood.) What if I add it in conjunction with a pH buffer? (I must be really awful at literature searching ... at least for inorganic chemistry.)

I'm trying to see if I can form a coordinated H3O+ === -O-Cl+-[Fe(III)Cl3] complex and have that do any interesting reactions, like alpha-oxidation (but possibly for any other useful oxidations). Complexed hypochlorite would be less basic, right? (The H3O+ is generated from the other Fe(III) centres but we could have a buffer that kept the pH at 7. )

Google did say that adding potassium hydroxide to Fe(III) chloride and bleach (probably not in order) actually creates potassium ferrate. I'm trying to activate the bleach via the Fe(III) chloride and not the other way round. From what I know from second semester orgo, Fe(III) chloride has a high affinity for chlorides. I'm also wondering if there any good candidate reactions for cyclic transition states.

IF hypochlorite forms a complex with Fe(III) chloride, does it also encourage attack on the Cl+ like atom, if the oxygen anion is perhaps stabilised with a hydrogen bond (maybe in a cyclic transition state)?

Sometimes I read some reactions where basic conditions seem to encourage bleach's reactivity, which puzzles me, because I assume that additional base discourages hypochlorite's electrophilicity. Is hypochlorite that good of a nucleophile? John Riemann Soong (talk) 01:08, 16 September 2010 (UTC)

No is the answer to every one of your questions above. I advise you to go and read any standard inorganic chemistry textbook, section "oxidation states of chlorine", before you ever use bleach, even (in fact, especially) in your own home. Physchim62 (talk) 01:23, 16 September 2010 (UTC)

I use bleach as my primary oxidizing agent. Please do not over exaggerate the danger of chemicals to qualified personnel. --Chemicalinterest (talk) 10:52, 16 September 2010 (UTC)

I am not "overstating the dangers of chemicals", and the OP is obviously not qualified. He is ignorant of basic chlorine chemistry (whether dangerous or not), and ignorant of his own ignorance. Physchim62 (talk) 14:23, 16 September 2010 (UTC)

Don't even think about trying this at home unless properly trained in inorganic chemistry. FeCl₃ is a really nasty compound! BTW, as Physchim62 already said – would not work they way you think. Alfie↑↓© 01:43, 16 September 2010 (UTC)

The reason I said especially not at home is that JRS obviously doesn't know (or has forgotten) that acidifying bleach will simply produce chlorine gas. Unfortunately, people die every year from accidental acidification of bleach in the home. One of my favourite exam questions in undergrad inorganic chemistry is "when should you not throw up in a toilet?" (Ans: when there's bleach in it, when you should try to flush first or at least at the same time) Physchim62 (talk) 01:57, 16 September 2010 (UTC)

Not if you use acetic acid. I get reaction NaClO + HC₂H₃O₂ → HClO + NaC₂H₃O₂. --Chemicalinterest (talk) 10:52, 16 September 2010 (UTC)

ACK. I like your exam question. ;-) Alfie↑↓© 02:04, 16 September 2010 (UTC)

I am not unaware that acidifying bleach will produce chlorine under normal circumstances. But AFAIK you need a reduced chloride anion to form chlorine ... surely it's not going to take it off of chloride-hungry ferric chloride! (Though reduction of hypochlorite might produce chloride...which will be quickly gobbled up by greedy Fe(Cl3).

Furthermore I expect that complexed hypochlorite does not behave the same way as free hypochlorite. John Riemann Soong (talk) 02:48, 16 September 2010 (UTC)

Now look up the solubility product of iron(III) hydroxide, and come back when you understand the answer. Hint: you DO NOT know it already. Physchim62 (talk) 02:52, 16 September 2010 (UTC)

Well hmm, I possibly see the problem you might be talking about. FeCl3 + 3H2O ---> Fe(OH)3 + 3HCl. Would adding acetic acid prevent the production of chloride? Or just use a chloride-free Lewis acid? Don't we still have the pH buffer option? John Riemann Soong (talk) 03:01, 16 September 2010 (UTC)

I can't comment on that specific mixture but adding vinegar aka acetic acid to bleach is generally accepted as a bad idea [1] [2]. There are plenty of people commenting in the second link who've found out that it does indeed produce chlorine gas. The only exception (other then in carefully controlled laboratory situation involving people who know what they're doing) may be if you're in an emergency and need to kill anthrax spores as evidentally it's significantly more effective when acidified [3] although in such a case I would make sure it's done outside and the products are properly diluted before mixing Nil Einne (talk) 10:06, 16 September 2010 (UTC)

How does it make Cl2? Please provide a chemical reaction. --Chemicalinterest (talk) 10:52, 16 September 2010 (UTC)

Considering you two have a great interest in chemistry and I don't, I'm surprised that I'm the one who has to answer this, but from a quick search [4] (see end). It's worth remembering there's always chlorine gas being released, hence the smell, so it isn't that surprising you just have to change the equilibrium to release a resonable amount of chlorine gas. Nil Einne (talk) 11:06, 16 September 2010 (UTC)

Hahahaha heheheheheThat reaction is not balanced. I will post it here: 2 HOCl + 2 HAc ←→ Cl₂ + 2 H₂O + 2 Ac^-. I wonder what those acetate ions bond to... they can't just float around bonding to nothing. Note: Once I tried to argue that all acids + hypochlorite yield chlorine. I COULD NOT find a chemical equation for it. That's why I say that it does not make chlorine. If anyone has a better equation, please post it here.

The problem is: Chlorine is being reduced, but nothing is being oxidized. It is a redox reaction. --Chemicalinterest (talk) 14:10, 16 September 2010 (UTC)

Also, HOCl cannot become Cl2 if no chloride species are present right? If Fe(III) chloride is that much of a problem -- it would surprise me if it was, what about BF3 or B(C6F5)3? John Riemann Soong (talk) 02:53, 16 September 2010 (UTC)

Are you proposing that typical chlorine-bleach does not contain Cl^–? DMacks (talk) 03:22, 16 September 2010 (UTC)

Isn't it an equilibrium between NaOH and HOCl? Or we could add pure sodium hypochlorite powder. John Riemann Soong (talk) 03:58, 16 September 2010 (UTC)

Bleach solution exists as an equilibrium between OCl- ions and Cl2 molecules dissolved in water. See Bleach#Chemical_interactions. --Jayron32 04:07, 16 September 2010 (UTC)

Adding potassium hydroxide to iron(III) chloride would make iron(III) oxide. Dilute potassium hydroxide or potassium hydroxide/potassium carbonate solution would not work. Bleach needs to be concentrated, too. Household bleach would not work to make the ferrate.

The reaction of ferric chloride with sodium hypochlorite is: 2 FeCl₃ + 3 NaClO → Fe₂O₃ + 3 NaCl + 3 Cl₂. This reaction is assuming there is no additional acid in the FeCl3. The natural acidity of FeCl3 in neutral solution converts it into Fe2O3 and HCl. The HCl reacts with the NaClO. I am not sure whether the HCl would react with the residual NaOH in the bleach or the NaClO first.

Base makes bleach a weaker oxidant. Just react NaCl vs. HCl with bleach; the additional acidity encourages its oxidizing powers. Some things are only oxidized when they are in a basic environment. Chromates are an example. Bleach is basic, too, so this would encourage any basic reaction.

When I use bleach, I only use millimeter quantities. I have done it in a room packed with my mother's precious stuff. The chlorine or chloramine made by reacting with 1 mL of bleach is negligible. So, if you do chemistry at home, do not use beakers.

Acidifying bleach would produce chlorine gas if there is any chloride available to be oxidized. I reacted acetic acid with bleach to make the powerful oxidant hypochlorous acid, which I used to completely rust steel wool in a short time. No chlorine was made.

Typical chlorine bleach does contain some Cl^-; the production reaction is 2 NaOH + Cl₂ → NaClO + NaCl + H₂O. Chloride does not react with hypochlorite unless acidified; in base this equilibrium leans toward the right; Cl₂ ←→ Cl^- + Cl⁺. In acid, it leans toward the left. Bleach is quite basic, so the equilibrium leans far to the right.

If you read through this long post, thank you. --Chemicalinterest (talk) 11:44, 16 September 2010 (UTC)

"No chlorine was made". How can you state that? Do you know the pH you were working at? What concentration? Depending on the exact pH, you would have made some chlorine, because that particular equilibration reaction is rapid, but you might have been lucky enough to keep it all in solution.

Bleach is not produced by the "classical" reaction 2 NaOH + Cl₂ → NaClO + NaCl + H₂O, i.e. starting from preformed sodium hydroxide and chlorine. Instead, it is an electrolytic oxidation of sodium chloride, which you can visualize as forming the NaOH and Cl₂ in situ: it is similar to the chloralkali process, but without the membrane between the two compartments of the cell (and good mixing and cooling). So there is no "excess NaOH" in commerical bleach.

There is no need for additional chloride to be available for hypochlorite to give chlorine on acidification: 5HClO → HClO₃ + 2Cl₂ + 2H₂O. You should always remember that Nature might know far more chemistry than you do!

Cl⁺ does not exist in solution: maybe you are confusing charge numbers on ions with oxidation state. Physchim62 (talk) 14:24, 16 September 2010 (UTC)

I don't know what happened: Wikipedia and several other sites went down on my computer. So my responses will be shorter and curt because I wrote them before the crash and could not save them.

A nose is a very good instrument for detecting chlorine. That's what I used. ;)

There is no excess NaOH, but the hydrolysis of NaClO (similar to NH3) produces a base.

Your reaction is not balanced. Cl5+ and Cl+ cannot yield Cl⁰.

I didn't say Cl+ existed in solution; I meant the ClO^- ion. It is just a simplified version of the reaction, removing the oxide. --Chemicalinterest (talk) 15:53, 16 September 2010 (UTC)

A nose is very bad at detecting chlorine in solution (unless you're in a swimming pool)

My equation is perfectly balanced: if you don't believe me, count the atoms and the charges. 5Cl(I) = Cl(V) + 4Cl(0). Chlorine(I) (i.e., hypochlorite or hypochlorous acid) is unstable with respect to disproportionation at any pH, although the reaction is slow at room temperature if pH >8. Physchim62 (talk) 16:07, 16 September 2010 (UTC)

I see. You didn't have the → sign, and I thought it was the HClO + HClO3 → Cl2 + 2 H2O. Sorry.

Your points are correct. But I still hold to my original belief that bleach + vinegar ≠ chlorine. --Chemicalinterest (talk) 16:30, 16 September 2010 (UTC)

See thread below. --Chemicalinterest (talk) 16:46, 16 September 2010 (UTC)

Ok, well, is it possible to use chloramine as an oxidiser, in combination with a Lewis acid then? AFAIK chloramine's conjugate acid pKa is around ~2. SN2 attack on nitrogen centre, kicking out Cl- as a leaving group. I imagine if I perform this on an ether I would get a hemiaminal. John Riemann Soong (talk) 04:03, 16 September 2010 (UTC)

So the pK_a of the conjugate acid of chloramine is about 2. What does this tell you? It tells you that chloramine is a much stronger base than your ether, so it will react preferentially with your Lewis acid, negating the whole purpose of the addition.

You have already been told that THF can be oxidized by a stoichiometric quantity of bromine to give gamma-butyrolactone, which as apparantly what you want in the first place. Why on earth you want to synthesize it, I don't know, because it is a widely available industrial solvant. It can be reduced by sodium borohydride to give the hemiacetal, and this would be how any real chemist would prepare that compound, not by oxidizing THF.

If you do decide to buy some gamma-butyrolactone, make sure you have a more convincing reason for why you want it than the one you've given here: it is a precursor to GHB, a schedule 1 controlled substance in your jurisdiction of residence, so the DEA may well have some questions for you. Needless to say, we are not going to publish the recipes for "drugs of abuse from household and other easily available substances" on the Reference Desk.

Perhaps you've never heard of GHB, many people haven't. If so, you should know about it, it would be part of your chemical culture. I might suggest that if you expanded your scientific culture in general, you would need to ask fewer questions at the Reference Desk. Physchim62 (talk) 18:00, 16 September 2010 (UTC)

Uhh, the whole point of the Lewis acid is to activate the oxidiser -- not the reductant / nucleophile. Well, I thought it was obvious. :p Also, GBL isn't available in my lab, but THF is. Acetal and carbohydrate chemistry is of interest to me, plus alpha-oxidation is just pretty damn interesting.

(Also wth, GHB is controlled? But it's a simple 4-carbon compound ... how can you expect to control it? Next thing they'll think they can control the supply of ethylene glycol. Or ban the fatty acids in butter. ) John Riemann Soong (talk) 22:28, 16 September 2010 (UTC)

Organic compounds with metal ions

What's it called when an organic compound has a metal ion trapped in the center (e.g. Vitamin B12)? --71.153.45.75 (talk) 01:32, 16 September 2010 (UTC)

Organometallic complex Alfie↑↓© 01:46, 16 September 2010 (UTC)

are receptor tyrosine kinases related by homology or analogy?

I suspect most of them are analogous (that is their common structural motifs arise out of convergent evolution), unless someone can tell me the RTK family closest to the epidermal growth factor receptor family? John Riemann Soong (talk) 05:20, 16 September 2010 (UTC)

Both. The "business end," i.e. the canonical tyrosine kinase domain itself, is conserved among the various RTKs and cytoplasmic TKs but the rest of the structures are pretty divergent. So, presumably the tyrosine kinase domain emerged very early in evolutionary history and because it was so useful it became incorporated into a variety of different genes encoding cytoplasmic tyrosine kinases and receptor tyrosine kinases, resulting in the large number of tyrosine kinase gene families. Then there were gene duplication events within each family to form multiple members of each group. Here are a few references:

• [5]: A review of the protein tyrosine kinases in humans, including a phylogenetic analysis suggesting that the tyrosine kinase domain of the EGFR family is most closely related to the SYK family of cytoplasmic tyrosine kinases.
• [6]: Phylogenetic analysis of individual protein tyrosine kinase classes suggesting where gene duplication events have happened.
• [7]: Comparison of plant and animal RTKs suggesting that "that plant receptor kinases have evolved independently of the receptor kinase families found in animals" (presumably from an ancient gene encoding a tyrosine kinase domain)
• [8]: Not exactly what you're after but phylogenetic analysis of the Ig-containing RTKs.

I hope that helps you get started. --- Medical geneticist (talk) 13:14, 16 September 2010 (UTC)

Valois in South America

Transferred to Humanities

por favor quisiera saber como llega "Valois" a suramerica, concretamente a Colombia, quienes llegan al nuevo continente utilizando este apellido, si la unica heredera de la DINASTIA VALOIS no tuvo descendientes? gracias! —Preceding unsigned comment added by 190.26.158.158 (talk) 06:47, 16 September 2010 (UTC) Below is the Google translation of the above question Rojomoke (talk) 07:37, 16 September 2010 (UTC) please let me know as it comes "Valois" in South America, specifically Colombia, who come to the new continent using this name, if the only heir of the Valois dynasty had no descendants? thanks! -

I transfered this question to the Humanities desk, please see the question there. Ariel. (talk) 10:20, 16 September 2010 (UTC)

Multiple voltage splitting circuits

Hi all,

I know that using a voltage splitting circuit, I can use a known resistor on one side, my unknown resistor on the other, and measure the voltage in the middle to work out the unknown resistance.

My question is: I want to make a circuit where I can independently measure several different unknown resistances at once. I have worked out a way to do this with an equal number of known resistors (see image here), but is it possible to do it with just one known resistor? I want to simplify my circuit.

(The actual project involves multiple resistance-changing sensors, and I want my Arduino to be able to measure the resistance of each of the sensors.)

Thanks! — Sam 76.24.222.22 (talk) 12:12, 16 September 2010 (UTC)

Yes, but if you want to do it by measuring voltages, you will have to place everything in series, not in parallel: this might lead to some pretty low voltage drops, which you might not be able to measure accurately. You also have to solve a set of four simultaneous equations to get the four resistances. So the scheme you propose is simpler and more robust for practical measurements. Alternatively, you can have a single known resistance, the four unknown resistances in parallel, and you measure the current through each unknown resistor. Physchim62 (talk) 12:36, 16 September 2010 (UTC)

Hmm, while I think I can see how I could so it mathematically if I knew the currents, I don't think it would be simple to construct a circuit to measure the current at a point on a wire using an arduino... Right? I guess I'll just stick to the circuit I drew -- it's not that complicated. Thanks! — Sam 71.174.136.111 (talk) 13:27, 16 September 2010 (UTC)

The voltage across the known resistor tells you the current. What is hard about that? Edison (talk) 19:51, 16 September 2010 (UTC)

Because I need to work out the current going into each of the individual unknown resistors in the circuit Physchim62 was describing. — Sam 63.138.152.135 (talk) 20:47, 16 September 2010 (UTC)

nb. An Arduino is a single-board microcontroller and a software suite for programming it. (For those like me who were wondering) - 220.101 talk^\Contribs 20:38, 16 September 2010 (UTC)

A purely series circuit, with one known resistor in series with N unknown resistors allows you to determine the current through each circuit element via the voltage drop across the known resistor. Then the voltage drop across each unknown series resistor, combined with the known current, tells you the resistance of each unknown resistor. If each unknown resistor is in parallel with the others, you would have to determine the current in each branch. A small, known, sampling resistor in each branch circuit would be required. You cannot get something for nothing. You cannot determine the current through unknown resistors in parallel without a current measuring device, which could be the sampling resistors, or a Hall Effect current transducer, or an ammeter, or some element to tell you the current. Write the loop and node equations and see for yourself. Edison (talk) 23:59, 16 September 2010 (UTC)

Does the incubation period depends on the infected organ?

And in particular, is it possible that the incubation period of an infection of a certain organ will be shorter than the one specified in the Examples table? —Preceding unsigned comment added by 217.132.191.179 (talk) 15:09, 16 September 2010 (UTC)

Please elaborate. For some infectious diseases (e.g. rabies) the infection (bite) site affects the incubation period. However, the infected organ (the peripheral, and eventually the central nervous system) is the same in any case of rabies. What infection and what organ are you asking about? --Dr Dima (talk) 18:14, 16 September 2010 (UTC)

It's a general question, I'm not asking about a particular infection and organ. When I've wrote 'organ' I actually meant the infection site, so your answear satisfies that question. Thank you. I still wonder if the minimum of the incubation period in the Examples table is the absolute minimum, and that there is no infection sites which will reduce the incubation period, Or if there are circumstances in which the incubation period will be lower (in people with immunity depression perhaps). 89.138.126.126 (talk) 19:21, 16 September 2010 (UTC)

A quick Google search turns up a number of reports on this topic. This paper discusses a series of cases of systemic Listeria monocytogenes infection in a hospital setting (the victims were exposed to a contaminated Camembert cheese plate). The authors note that the incubation period was indeed shorter than usual, and attribute this to two factors: an abnormally high bacterial load in the contaminated foodstuff, and a severely immunocompromised patient population. TenOfAllTrades(talk) 19:40, 16 September 2010 (UTC)

"Personality disintegration"

I've heard someone use this term before, but see few reference to it in other places. Is it a real psychological thing, or made up? "Exact words were "final stages of personality disintegration." 204.184.80.26 (talk) 15:22, 16 September 2010 (UTC)

It isn't an officially recognized diagnosis, but the term has been used many times in scholarly publications, dating back at least to the 1930s. Most commonly it is used in relation to schizophrenia, but also for dementia of various sorts. Looie496 (talk) 15:47, 16 September 2010 (UTC)

Looie's correct: it's a somewhat dated, semi-scholarly euphemism for 'having a mental breakdown'. The only time it would be used by a health professional is when they were unsure of an exact diagnosis, but reasonable sure that some kind of diagnosis would be made. --Ludwigs2 15:55, 16 September 2010 (UTC)

gutters

We had a new roof put on in Nov. We have been having a lot of rain recently, and noticed that the gutters are no longer working, the rain runs between the fachia board and the gutter, it is terrible, no rain water goes in the gutters. I called the roofer out, and he said that the gutters are not close enough to the fachia board. Its kind of odd that we didn't have that problem until we had the new roof put on. My son cleaned the gutters, and behind them, where he found a lot of nails, and pieces of old roofing, but the water still does not run into the gutters, he even made sure that the gutter was tight against the fachia. What do you think the problem could be? Thanks! --Kj650 (talk) 16:02, 16 September 2010 (UTC)

When did you have this new roof put in? And how long have you had this problem? Someone posted the exact same message over a year ago at www.5min. com/Video/Fixing-a-Leak-in-the-Gutters-19945133 (blacklisted site) [9] (archival copy). Nil Einne (talk) 16:47, 16 September 2010 (UTC)

I'd contact the original roofer and ask them to rectify the problem. When they put the roof on, they should have checked to make sure the runoff went into the guttering correctly. If they don't play ball - well you have options after that such as legal action. Exxolon (talk) 01:13, 17 September 2010 (UTC)

The roofing should overshoot the fascia board so that water enters the guttering first without touching the fascia board. If you can't get the roofers to correct the error (assuming that the problem is as I imagine), then a strip of thick plastic from under the roofing to overlap the edge of the guttering would provide a temporary solution. Dbfirs 13:24, 17 September 2010 (UTC)

Did you check to see if the downspouts were clogged? —Preceding unsigned comment added by 165.212.189.187 (talk) 17:15, 17 September 2010 (UTC)

Reverse topographic prominence

My question is basically "what is the most isolated basin/lake in the world", but in a certain well-defined sense. The topographic prominence of a peak is the least you have to go down in elevation before you can ascend to a higher peak. So, define the "reverse topographic prominence" of a basin as the least you have to go up before you can descend to a lower basin (or sea level). According to this definition, the combined surface of all the oceans has the greatest reverse topographic prominence (you could define it as equal to the height of Mount Everest).

My question is, what region on Earth has the second greatest reverse topographic prominence? My first guess would be the Caspian Sea, but I have no idea if that's right. —Keenan Pepper 16:23, 16 September 2010 (UTC)

Not sure I understand. Wouldn't the greatest reverse prominence be the Dead Sea, since it is the lowest basin on Earth? Looie496 (talk) 17:41, 16 September 2010 (UTC)

In any case there are a bunch that are greater than the Caspian, including Death Valley and Great Salt Lake in the USA. My guess, though, is that the greatest is the Turpan Depression in western China. Looie496 (talk) 17:50, 16 September 2010 (UTC)

The Turpan Depression "includes the third lowest exposed point on the Earth's surface (dry Lake Ayding, -154m), after the Dead Sea and Lake Assal (Djibouti)", but that only covers exposed points. Won't the Mariana Trench contain the point of greatest reverse topographic prominence? Or are we counting liquid water as part of the topography of the surface (I had difficulty parsing that bit)? In which case, presumably the Dead Sea wins, although do we have to take into account variation in the depth of water in lakes and inland seas, once we've decided to take water as part of the topography? Second will be tricky, unless the second deepest point is half a great-circle-distance from the deepest! But we really need clarification before we can continue. 86.164.78.91 (talk) 00:18, 17 September 2010 (UTC)

Keenan's definition does not make sense to me if it is suposed to be true that "the combined surface of all the oceans has the greatest reverse topographic prominence (you could define it as equal to the height of Mount Everest)". We're supposed to be looking for the least distance that you have to go up before you go down again. Say that in some place like California or Australia where you have desert near the ocean, there is a dry depression with its floor at say 20 feet elevation, ringed by hills varying from 40 to 500 feet high. Then the "reverse topographic prominence" of the ocean is only 40 feet, because after that you can go down into this depression, unless there is a still lower such location elsewhere in the world. Clearly, dry depressions like that do exist, as well as depressions with a lake at the bottom, so while my 40-foot example is hypothetical, Mt. Everest has got to be irrelevant.

Would Keenan care to clarify what he's actually looking for? --Anonymous, 22:52 UTC, September 16, 2010.

The prominence of a peak is the height of the peak’s summit above the lowest contour line encircling it and no higher summit.

This is what I think is meant by the OP's "reverse prominence".

Is the image on the right showing what is meant here by "reverse prominence"? WikiDao ☯ (talk) 00:30, 17 September 2010 (UTC)

The image is exactly what I'm talking about. Simply the definition of ordinary topographic prominence, but turned upside down. I made a mistake in the example I gave &em; I neglected the fact that there are places lower than sea level, so the actual place with the greatest reverse topographic prominence is the Dead Sea. So, my question is, what is the place with the second greatest reverse topographic prominence, after the Dead Sea? I suspect it's not the oceans, or Death Valley or anything like that. —Keenan Pepper 02:18, 17 September 2010 (UTC)

As I wrote above, I think it's probably the Turpan Depression. You have to rise over 4000 feet to get out of that hole. I can't think of any other hole anywhere near as deep that isn't full of water. Looie496 (talk) 03:13, 17 September 2010 (UTC)

Great, that's the answer I'm looking for then. Thanks! —Keenan Pepper 04:38, 17 September 2010 (UTC)

Do all acids form chlorine from hypochlorites?

There was a thread above that brought up this question. It was never answered satisfactorily. I will post it again here to avoid cluttering of the above discussion: Do all acids react with sodium hypochlorite to form chlorine gas? --Chemicalinterest (talk) 16:48, 16 September 2010 (UTC)

I can't comment on that specific mixture but adding vinegar aka acetic acid to bleach is generally accepted as a bad idea [10] [11]. There are plenty of people commenting in the second link who've found out that it does indeed produce chlorine gas. The only exception (other then in carefully controlled laboratory situation involving people who know what they're doing) may be if you're in an emergency and need to kill anthrax spores as evidentally it's significantly more effective when acidified [12] although in such a case I would make sure it's done outside and the products are properly diluted before mixing Nil Einne (talk) 10:06, 16 September 2010 (UTC)

How does it make Cl2? Please provide a chemical reaction. --Chemicalinterest (talk) 10:52, 16 September 2010 (UTC)

Considering you two have a great interest in chemistry and I don't, I'm surprised that I'm the one who has to answer this, but from a quick search [13] (see end). It's worth remembering there's always chlorine gas being released, hence the smell, so it isn't that surprising you just have to change the equilibrium to release a resonable amount of chlorine gas. Nil Einne (talk) 11:06, 16 September 2010 (UTC)

Hahahaha heheheheheThat reaction is not balanced. I will post it here: 2 HOCl + 2 HAc ←→ Cl₂ + 2 H₂O + 2 Ac^-. I wonder what those acetate ions bond to... they can't just float around bonding to nothing. Note: Once I tried to argue that all acids + hypochlorite yield chlorine. I COULD NOT find a chemical equation for it. That's why I say that it does not make chlorine. If anyone has a better equation, please post it here.

The problem is: Chlorine is being reduced, but nothing is being oxidized. It is a redox reaction. --Chemicalinterest (talk) 14:10, 16 September 2010 (UTC)|}

The answer is unambiguously yes. I did link to it above, but did not explain it in detail. See Bleach#Chemical_interactions which I linked to above. The equilibrium reaction shown there makes it clear that ANY source of H+ ions will push the equilibrium towards the CL2 side of the equation. H+ ions have no memory from which acid they came from; even acid salts like the aforementioned Iron (III) Chloride will generate a sizable amount of H+ ions in solution; this would be more than enough to tip the equilibrium towards the Cl2 side of the equation. Furthermore, the equilibrium is an unstable equilibrium; if the pH is sufficiently high (and sufficient is probably a pretty weakly acidic solution in this case), the reaction will convert all of the bleach to Cl2 given enough time, in an open environment. That's because Cl2 is constantly removed from the reaction in an open space, so per LeChatelier's principle, the reaction will keep producing Cl2 until the hypochlorite all but runs out. Of course, in a closed container with a sufficiently small headspace, the equilibrium will establish itself when the partial pressure of Cl2 builds up to levels which force the reaction back again. But if left in the open, the hypochlorite will eventually all run out, in the exact same way that soda pop goes flat when you leave the container open. --Jayron32 17:17, 16 September 2010 (UTC)

The equilibrium requires both H+ and Cl- ions to produce Cl2. Where to the Cl- ions come from? The bleach? --Chemicalinterest (talk) 17:45, 16 September 2010 (UTC)

(EC) I can't answer the general question but [14] appears to have what's perhaps a better explaination (see the later posts) for the reaction with acetic acid then my earlier link Nil Einne (talk) 17:14, 16 September 2010 (UTC)

(edit conflict)In your acetic acid example, by the by, the acetate will be the other half of the redox. Acetate will happily reduce to ethanol in the presence of hypochlorite. So your reaction is wrong; the acetate does not remain intact instead it reduces to ethanol. --Jayron32 17:17, 16 September 2010 (UTC)

Acetate has to oxidize, not reduce. The bleach is the oxidizing agent, being reduced. The acetate would be the reducing agent, being oxidized. I do not know organic electrochemistry so I don't know whether acetate is oxidized or reduced to ethanol. --Chemicalinterest (talk) 17:45, 16 September 2010 (UTC)

Any reasonably strong non-oxidizable acid has the potential to form chlorine from hypochlorite. Chlorine is the predominant product when the pH falls below 4.56. In the absence of chloride ions, the reaction will go at different rates depending on the acid: it is particularly rapid in the presence of chloride ions (as in commercial bleach, or by addition of hydrochloric acid), but will still go even in the complete absence of external chloride as hypochlorite can both disproportionate to give chlorate and oxidize water to oxygen at any pH. Have you never wondered why commercial bleach solutions smell of chlorine? Physchim62 (talk) 17:30, 16 September 2010 (UTC)

Yes, hypochlorites can decompose 2 NaClO → 2 NaCl + O₂. What I want is a true reaction for non-chloride acid + sodium hypochlorite → chlorine. --Chemicalinterest (talk) 17:45, 16 September 2010 (UTC)

You are saying that this reaction occurs very slowly in commercial bleach solutions? NaClO + NaCl + H₂O → Cl₂ + 2 NaOH Note: There is still a source of chloride producing the chlorine. My question again. Can chloride-free acids make chlorine from bleach? --Chemicalinterest (talk) 17:48, 16 September 2010 (UTC)

4MeCOOH + 5NaOCl → 2Cl₂ + NaClO₃ + 4MeCOONa + 2H₂O. Physchim62 (talk) 18:13, 16 September 2010 (UTC)

Disproportionation? I never heard of acid-induced bleach disproportionation. Wouldn't that be a good way to make chlorate explosives? What about 3 NaClO → NaClO₃ + 2 NaCl? That is a more accurate disproportionation reaction. --Chemicalinterest (talk) 19:46, 16 September 2010 (UTC)

That equation looks like just a combination of the two separate disproportionation reactions others have mentioned. The difference is the addition of acid, and it's pretty well-known that redox potentials are pH dependent. This is an acidic-conditions equation, so the H+ help balance it (and you can see the acetate as a byproduct...it's the non-reacting counterion to the H+). Could probably write comparable equation for alkaline-conditions, you would just have OH- somewhere, which would also look fine on paper. But to answer your specific concern, now you have heard of it. The entry for "Sodium hypochlorite" in ISBN 978-0824703530 (page 51) states "Sodium hydroxide is usually added [...] to improve stability by minimizing the hpoychlorite disproportionation to chloride and chlorate." Feel free to speculate the role of non-alkaline conditions in accelerating the reaction (redox potentials, acid catalysis, whatever), but don't use paper chemistry to say something can't/won't happen when others tell you that Nature says it does. DMacks (talk) 20:09, 16 September 2010 (UTC)

That is disproportionation to chlorate and chloride, not chlorine. That's why I fussed about the reaction. --Chemicalinterest (talk) 20:13, 16 September 2010 (UTC)

You say "Yes, hypochlorites can decompose 2 NaClO → 2 NaCl + O₂" and "Can chloride-free acids make chlorine from bleach?". Please stop and think about how silly this question sounds. You've been told many times in many ways with links to wikipedia articles that bleach can decompose to chlorine in several ways, only some of which require acid, and that bleach itself can supply chloride. DMacks (talk) 18:04, 16 September 2010 (UTC)

(edit conflict)Nil Einne, that paper was good. I see the discrepancy here: bleach vs. sodium hypochlorite. Bleach is a mixture of sodium hypochlorite and sodium chloride. According to some people's posts there, the bleach reaction goes backwards. NaOH and Cl2 are recreated. The NaOH reacts with the acid, making the sodium salt, and the Cl2 is liberated. This reaction only occurs because of the extra chloride in the bleach. So, bleach and acetic acid react to form chlorine. But do sodium hypochlorite and acetic acid react to form chlorine? --Chemicalinterest (talk) 18:05, 16 September 2010 (UTC)

Does this reaction happen? 5 NaClO + 4 H⁺ → NaClO₃ + 2 Cl₂ + 4 H⁺ + 4 H₂O. This is, according to User:Physchim62, the reaction that happens when a non-chloride acid reacts with sodium hypochlorite. --Chemicalinterest (talk) 20:10, 16 September 2010 (UTC)

Erm, I didn't quite say that! If you are at a pH higher than about 5–6 (which you have to be to have "NaClO"), the reaction is 3NaClO → NaClO₃ + 2NaCl. This is the reaction that causes domestic bleach to "go off" (or lose strength) with storage: it is slow at room temperature, but noticeable at the scale of weeks or months. The disproportionation of HClO is much much faster. Physchim62 (talk) 20:37, 16 September 2010 (UTC)

Please remember that it is my job to oil everyone's rusty inorganic chemistry skills with an occasional dispute. --Chemicalinterest (talk) 11:14, 17 September 2010 (UTC)

vandal proof remote dwelling

Some time ago, I saw a published remote dwelling design featuring exterior metal walls/covers which were [by internal levers & wheels or capstans] rolled/slid into place to cover windows, etc. The result was a two-level dwelling with an exterior of solid metal walls, like a box. A non-electric keyless door lock was the only way in.

When the dwelling is occupied, the movable exterior metal walls exposed large glass window walls on all four sides and cover fixed metal exterior walls.

Though vulnerable to graffiti, the closed dwelling is virtually impervious to fire and most hunting weapons, as well as common glass breakage using rocks or weapons.

I would appreciate your help in finding some data on this dwelling. Deafness here makes written reply best. Thanks. —Preceding unsigned comment added by 66.66.32.230 (talk • contribs) 22:03, 16 September 2010

Bad idea to leave your contact info here. I have removed it; any answers to your question will be provided here. Thanks. WikiDao ☯ (talk) 22:28, 16 September 2010 (UTC)

If there is a sheet metal shutter, it will thwart the unequipped vandal or burglar, but not someone who brings along suitable tools for breaking in. My experience has been that a vacation cabin gets broken into by kids who simply kick in the flimsy door, or jimmy open a window with a prybar, or break the glass and reach in and open a latch. A solid door and solid plywood or metal over windows might prompt a juvenile delinquent to move on to the next, and easier to break into, cabin. The metal would have to be pretty thick to stop a rifle bullet from a "hunting weapon." A 303 round is said to penetrate 40 mm of steel, a 30-06 is said to penetrate 3/8 inch steel.[15] The metal would have to be expensively thick to prevent entry if the thief had a drill, a jack, a crowbar, etc. If you build a dwelling from battleship armor plate, a thief can cut into it with a plasma torch. The more money you spend making a dwelling secure, the more incentive a thief will have to spend the effort and resources to break in, on the grounds that extreme safeguards imply treasures within. What is a "nonelectric keyless lock" and why would it be impossible to defeat it? Edison (talk) 02:51, 17 September 2010 (UTC)

I suppose your standard rotating-dial combination lock would qualify as "non-electric keyless" but a good pair of bolt cutters or a welding torch would make short work of that. The Masked Booby (talk) 07:24, 17 September 2010 (UTC)

Are you talking about these? [16], [17] They are often used to provided comfy living accommodation for site watchmen on remote sites etc. Better than a camper van. In the UK you may need to ask the local council about bylaws and things and planning permision may be required in some instances. --Aspro (talk) 10:22, 17 September 2010 (UTC)

Being shot at with "hunting weapons" is a fair way down the list of likely risks in the UK ;-) Alansplodge (talk) 23:12, 17 September 2010 (UTC)

Reversed lens

If you reverse a lens on a camera, the shorter the focal length, the greater the magnification when reversed. What is the focal length at which the focal length is the same, reversed or not? --The High Fin Sperm Whale 22:48, 16 September 2010 (UTC)

As long as the lense is symmetric, the focal length should be the same on either side, regardless of the specific value of the focal length. Rigel0 (talk) 01:51, 17 September 2010 (UTC)

A typical camera lens is optimized for a certain lens to film distance and typically a longer lens to subject distance. Reversing it might make macro photos sharper. Edison (talk) 04:06, 17 September 2010 (UTC)

Indeed: in pre-digital days (dunno about now), a popular camara accessory was the reversing ring, whose two ends mated respectively with the camera's lens mount and the lens's filter mount thread precisely in order to enable this ploy. 87.81.230.195 (talk) 11:04, 19 September 2010 (UTC)

dissolve organic compounds

So we have some bunnies and the bottom of their hutch is a metal mesh. We clean it periodically, but over time, the corners in particular, have gotten caked in a fairly hard, slightly nasty crust of fur, poop and other crud which does not come off easily because it's sort of interwoven in the mesh and stuff. So, my question is, what could I soak the mesh in that would dissolve the organic stuff off without oxidizing the mesh. Preferably something that's easy and legal to purchase please. Vespine (talk) 23:36, 16 September 2010 (UTC)

Nail polish remover? John Riemann Soong (talk) 00:04, 17 September 2010 (UTC)

Which will just be some organic solvent, probably Acetone, or maybe Ethyl acetate or Acetonitrile. I don't think that's going to do a ton of good in removing "fur, poop, and other crud". I think that you're going to have to do more than just soak it, whatever you use. I think that soap and water is going to be your best bet, but you're going to have scrub after you soak it. Buddy431 (talk) 00:27, 17 September 2010 (UTC)

I was thinking of a more industrial solution, like drain cleaner or something, but would that also oxidize the mesh? The mesh is not terribly thin, maybe 1.5mm, so I think it should survive a couple of hours in some draino, but if there was something better that didn't react with metal that would be a better option. Vespine (talk) 01:32, 17 September 2010 (UTC)

Good point. Drain cleaners are usually a strong hydroxide solution, which works well on greases and oils (breaking them down via the Saponification reaction). I don't think it should do anything to the metal (after all, they're intended to be poured down potentially metal piping), but I'm not sure how effective it's going to be against fur and stuff. Perhaps someone else with some experience in the matter can add something. Buddy431 (talk) 02:43, 17 September 2010 (UTC)

Does not drain cleaner also help with hair clogs? Take care when using it, because it tends to be nasty on your skin (i.e., if it dissolves rabbit poop, grease, and fur, it will dissolve you just as well), but that would be a good shot. --Jayron32 03:58, 17 September 2010 (UTC)

An alternative simple thing to try would be some hot water with biological washing powder. That's good at dissolving organic matter - although the challenge here might be too great. --Phil Holmes (talk) 08:55, 17 September 2010 (UTC)

If the mesh is aluminium, please do not use drain cleaner as you may see some hydrogen gas and the mesh is no more. --Chemicalinterest (talk) 11:11, 17 September 2010 (UTC)

Like this. I think it's unlikely for a cage to be made of aluminum, though (I would think stainless steel is much more likely). Buddy431 (talk) 16:57, 17 September 2010 (UTC)

September 17

light slowing down in a material

After doing quite abit of undergrad work on light,(reflection, refraction, the various velocities etc) no one ever explained why light slows down in a material. I mean at a fundamental level what are the photons and (electrons i assume?) getting up to that means the light velocity changes and why therefore material X has a different refractive index to material Y. Thanks --81.147.107.44 (talk) 12:14, 17 September 2010 (UTC)

Does this paragraph from Wikipedia's article on refraction help?

At the microscale, an electromagnetic wave's phase speed is slowed in a material because the electric field creates a disturbance in the charges of each atom (primarily the electrons) proportional to the permittivity of the medium. The charges will, in general, oscillate slightly out of phase with respect to the driving electric field. The charges thus radiate their own electromagnetic wave that is at the same frequency but with a phase delay. The macroscopic sum of all such contributions in the material is a wave with the same frequency but shorter wavelength than the original, leading to a slowing of the wave's phase speed. Most of the radiation from oscillating material charges will modify the incoming wave, changing its velocity. However, some net energy will be radiated in other directions Refractive_index#Interaction_of_light_and_the_medium Also remember, as you move towards the blue end of the spec the quanta value gets higher. --Aspro (talk) 13:08, 17 September 2010 (UTC)

Thanks, i see my problem i only looked at the refraction page not the refractive_index page--81.147.107.44 (talk) 13:18, 17 September 2010 (UTC)

Date of a photo

If I have a photo taken in a park where you can see landmarks and thus determine the direction the camera was facing and the sky looks clear and sunny could I determine the date by measuring the position of the sun? TheFutureAwaits (talk) 12:42, 17 September 2010 (UTC)

Yes. As always, Wikipedia has an article about it and everything else. It is called Forensic astronomy.--Aspro (talk) 12:57, 17 September 2010 (UTC)

Yes, the shadows would be the best guide. If it is a familiar location, you could just visit regularly until you see matching shadows, otherwise there is a fair amount of measurement and calculation involved. I'm not convinced that an exact date can be calculated reliably (and, of course, you need other clues to identify the season), but you might be interested in Masquerade_(book)#Solution. Dbfirs 13:12, 17 September 2010 (UTC)

Try checking the metadata, that usually has the date in it Quadrupedaldiprotodont (talk) 15:25, 17 September 2010 (UTC)

If you could tell the direction of a linear shadow (like the shadow of a post or pole), you would be able to tell the time of day fairly accurately as it would act as the gnomon of a sundial. The shadow would move from west to east and be pointing north at 12 noon in your local standard time (not daylight-saving time). In theory, you might be able to tell the month by the length of the shadow, but it would be difficult as I should think you would have to do a calibration as Dbfirs suggests by going to the park to check it over a long time frame. In a park, it would be much easier to look at what the flowers and trees were doing - and probably just as accurate. Only my opinion though; I'm not much of an expert. Alansplodge (talk) 23:06, 17 September 2010 (UTC)

The answer to the original question is no. By examining shadows you can determine the position of the sun and that will give you some information about the date, but it's not enough by itself to determine the date. Today is September 19, or just before the equinox; the sun will follow almost exactly the same path through the sky at the same length of time after the next equinox, i.e. sometime around March 24. And again on approximately these dates next year, and the following year, and so on, give or take a day due to the length of the year not being an integer.

If you could measure the sun position with extreme accuracy you might be able to do better by being able to say "This position is between the sun's paths for September 18 and 19 or 2010, so it must be in March 2010 or in a different year"; but most photos won't contain sufficient detail for that sort of measurement. --Anonymous, 04:06 UTC, September 18 or 19 (okay, 19), 2010.

FRACTIONAL DISTILLATION.

What are the exact weight and volume percentages of products (Petrol, Diesel, Naphtha, Kerosene , Natural Gas, Fuel Oil) obtained by Fractional distillation of crude oil???(considering normal US standards) —Preceding unsigned comment added by 180.149.48.66 (talk) 13:02, 17 September 2010 (UTC)

That will depend on the crude and whether its light heavy, tar-sands etc. --Aspro (talk) 13:11, 17 September 2010 (UTC)

Consider light crude oil. thanks —Preceding unsigned comment added by 180.149.48.66 (talk) 13:30, 17 September 2010 (UTC)

An exact answer is not possible. These fractions vary with each and every oil well, and also, the fractions change throughout the production life of a single well. Googlemeister (talk) 13:36, 17 September 2010 (UTC)

Representative answers, however, can be provided. See these Dept of Energy sites for refined proportions and monthly US refinery yield. Note that the above are still correct -- we probably can't provide exact values, but the monthly yields will let you calculate the average values. — Lomn 13:51, 17 September 2010 (UTC)

I'd be a bit cautious in interpreting those numbers. The final refinery outputs will almost certainly include products of cracking to increase the yields of lighter fractions like gasoline. In other words, the refinery numbers won't match what you would get from straight fractional distillation of the raw crude, because they involve further processing. TenOfAllTrades(talk) 14:07, 17 September 2010 (UTC)

I'm not even sure that two different refineries would give you exactly the same proportions from the same crude oil. Fractional distillation of a complex mixture like crude oil is extremely sensitive to process parameters and plant design. Even in the U.S., I doubt that every refinery is optimized for maximum gasoline production (even if most are). Physchim62 (talk) 14:18, 17 September 2010 (UTC)

aids

I remember watching a tv show a long time ago about some guy who got aids and took a load of pills and magically the aids was cured and he was a media mystery. Who was that guy? —Preceding unsigned comment added by 8947tn904 (talk • contribs) 14:52, 17 September 2010 (UTC)

No, AIDS cannot be cured in this manner. However, there are medications right now that will suppress the progress of the disease to the point where many people can lead symptom-free lives for a very long time. AIDS#Treatment and blue links you can follow from there go over how the disease is treated. --Jayron32 15:00, 17 September 2010 (UTC)

That's nice but not what I asked. I saw a tv show about a guy who took a load of pills and his aids was gone. I want to know the name of the guy, or the name of the tv show. It was some sort of documentary. I don't care if it's scientifically impossible or not, I just want to know the name of the guy so I can look it up 8947tn904 (talk) 15:04, 17 September 2010 (UTC)

Try posting on the entertainment desk, they are better at that. Ariel. (talk) 16:54, 17 September 2010 (UTC)

Agreed. It would also be helpful to specify whatever additional details you can remember like a time frame, what sort of show, the language of the show, if you can remember what country the show was from or at least in what country you saw it etc etc Nil Einne (talk) 19:49, 17 September 2010 (UTC)

I think I remember there being a very low, but not nonexistent rate of spontaneous remission of the body from the AIDS in a few individuals (and in addition a very small part of a population may be immune). It could be possible that the subject took the drugs then spontaneously healed. ~AH1^(TCU) 21:28, 17 September 2010 (UTC)

There is also a small but not nonexistent chance of a misdiagnosis.Sjö (talk) 11:44, 21 September 2010 (UTC)

You might be looking for the patient mentioned in the last paragraph of AIDS#Experimental and proposed treatments. He didn't take pills though, but received bone marrow from someone with a CCR5 mutation, which has a similar effect as Sickle Cell Anemia has with Malaria. -- 78.43.71.155 (talk) 21:04, 18 September 2010 (UTC)

wireless transmission of electricity

--Angadi Siddhartha (talk) 15:04, 17 September 2010 (UTC)
Is it possible to transmit electricity without using wires ?

Yes, see Wireless energy transfer 1230049-0012394-C (talk) 15:07, 17 September 2010 (UTC)

(ec) See wireless energy transfer and take note that making your question big big bold isn't going to get it answered better or faster. So, I removed that formatting. -- kainaw™ 15:08, 17 September 2010 (UTC)

See Crystal radio for a rather old application of wireless energy transfer. These radios drew their power directly from the radio wave. You can even build one of these yourself. :-)

Fun fact: In the early days of radio, people living near broadcasting towers would put a lightbulb between two pieces of wire tuned to the tower's wavelength, drawing power from the radio signal to light up the bulb. That was soon outlawed - but technically, it would still work today. -- 78.43.71.155 (talk) 20:53, 18 September 2010 (UTC)

Sounds bogus. How did they "tune two pieces of wire to the tower's wavelength?" How long were those pieces of wire? Edison (talk) 02:13, 19 September 2010 (UTC)

A dipole antenna is a common "homemade" antenna. It is very short compared to the wavelength and has very good gain. I used dipole antennas in an experiment a few years ago to see how much power I could get from cell towers using a series of tiny (very tiny) dipole antennas. It was enough to measure, but not enough to power anything - perhaps enough to trickle charge a battery. -- kainaw™ 03:41, 21 September 2010 (UTC)

Sulfur oxidation state discrepancy

The oxidation state of sulfur in sulfur dichloride is presumably +2 . The oxidation state of sulfur in sodium sulfate is presumably +6. Why is sulfur dichloride a so much stronger oxidizing agent? It can release chlorine gas upon standing, while sulfates can hardly do anything. Thanks. --Chemicalinterest (talk) 15:10, 17 September 2010 (UTC)

Is SCl2 necessarily a stronger oxidising agent? I think it's kinetically more unstable. Sulfates need to be protonated to be oxidised (just like nitrates) -- and of course you need a very low pH for that to happen (like, you need fuming sulfuric acid). John Riemann Soong (talk) 15:48, 17 September 2010 (UTC)

I wouldn't really say that SCl₂ is a strong oxidizing agent: I think Chem.int. is just focussing on one single reaction rather than the wider chemistry. Take the industrial manufacture of thionyl chloride, SOCl₂, for example

SO₃ + SCl₂ → SOCl₂ + SO₂

That's a classic conproportionation reaction, where S(VI) + S(II) = 2S(IV). SCl₂ is the reducing agent for sulfur trioxide (which is not a very strong oxidizing agent). Now if you look at the decomposition of SCl₂

2SCl₂ ⇌ S₂Cl₂ + Cl₂

that's an endothermic reaction, but not by much. The sulfur–sulfur bond that you form is about the same strength as the sulfur–chlorine bond you break, while the Cl–Cl bond is slightly weaker. But chlorine is a gas, which tends to push things towards the right (especially if you raise the temperature). Physchim62 (talk) 23:21, 17 September 2010 (UTC)

Are you sure its comproportionation? Isn't it symproportionation? Create a redirect if the term is really used. --Chemicalinterest (talk) 00:49, 18 September 2010 (UTC)

IUPAC says "comproportionation" [18]. In Latin, the prefix con- is the opposite of dis-, while syn- is the opposite of anti- ("n" assimilates to "m" before "p", as I forgot above). Physchim62 (talk) 01:43, 18 September 2010 (UTC)

To give some perspective, +40 kJ/mol (the heat of decomposition of SCl2) doesn't even exceed 2 OH-H hydrogen bonds). And each water molecule AFAIK forms on average 2 and half in the liquid phase. John Riemann Soong (talk) 00:56, 18 September 2010 (UTC)

Indeed. The Gibbs free energy change is only +18 kJ/mol (in the direction of SCl₂ decomposition). To put it another way, the mean bond energy of the S–Cl bonds is about 270 kJ/mol each, which is respectable for a covalent single bond but nothing amazing: carbon–chlorine bonds, for example are about 50 kJ/mol stronger. Physchim62 (talk) 01:43, 18 September 2010 (UTC)

why does blood smell like a spoon?

I understand blood is full of iron, but I didn't realise that the iron was prevalent in that high a concentration. For that matter, a drop of blood has more spoon-smell than a spoon itself. Wth? I'm pretty sure blood is not made of solid metal. John Riemann Soong (talk) 15:47, 17 September 2010 (UTC)

Metalic iron has a very low vapor pressure. Why would it smell at all? In order to smell a substance, it needs to be a gas. The ability to become a gas has nothing to do with the relative concentrations of substances. Furthermore, the smell of blood is not necessarily the smell of iron. --Jayron32 15:56, 17 September 2010 (UTC)

See this. You do not actually smell metal. What you smell is the body's reaction to metal. So, your nose is reacting to both blood and a spoon in a similar manner. -- kainaw™ 16:04, 17 September 2010 (UTC)

Thanks an interesting read. I've noticed before my hands smell like 'metal' when I've been holding keys or similar things but it's not something I've ever thought to look in to Nil Einne (talk) 19:35, 17 September 2010 (UTC)

Thanks so much. I was really puzzled at why blood would smell so strongly of metal when I was sure metal had no substantial vapor pressure. John Riemann Soong (talk) 19:45, 17 September 2010 (UTC)

It tastes like spoons too. I used to get nosebleeds in my sleep, and I have vivid memories of waking up with the taste of spoons in my mouth, and thinking "Oh no, another bloody pillow". DuncanHill (talk) 16:19, 17 September 2010 (UTC)

Are you sure it's a spoon? I just had some of my own and it tastes like more like a spork to me. DRosenbach ^{(Talk | Contribs)} 16:38, 17 September 2010 (UTC)

The hemoglobin in your blood contains iron oxide compounds, much the same substance that makes up rust. Metal spoons also contain iron and are in contact with air. ~AH1^(TCU) 21:23, 17 September 2010 (UTC)

You are smelling Oct-1-en-3-one. Graeme Bartlett (talk) 11:36, 18 September 2010 (UTC)

...which is completely devoid of iron altogether! SpinningSpark 11:57, 18 September 2010 (UTC)

liquid becoming solid at higher temperature?

There was something on the radio this morning about a substance that might be used for medical treatments that is a liquid when chilled but a solid at body temperature. Is this actually a reversable phase change or is it more like a thermoset glue? (If it's the former, is there a name for this property?) RJFJR (talk) 18:40, 17 September 2010 (UTC)

This news item sounds like what you are remembering. DMacks (talk) 19:16, 17 September 2010 (UTC)

That's it: "a injectable formulation derived from natural sugar chains that exists as a liquid when cooled and becomes a solid at body temperature." RJFJR (talk) 19:19, 17 September 2010 (UTC)

Thermoreversibilty I think could be the word. Poloxamer gels exhibit this property. They are nowhere as strong as the gels we are used to though. Perhaps that why they want to develop them further. They would have the property of keeping damaged cells from leaking out their contents out all over the place but are not up to the job just yet. --Aspro (talk) 19:46, 17 September 2010 (UTC)

The article Thermosetting polymer deals with the process in general terms; this sounds like the use of bioorganic molecules like sugars and polysacharrides to develop materials with similar properties. --Jayron32 19:47, 17 September 2010 (UTC)

Here we go: Temperature Induced Gelation. It is probably the next sec of 5.2.2. Cellulose derivatives which is applicable because cellulose is only sugar. Here's a patent as well.[19]--Aspro (talk) 20:11, 17 September 2010 (UTC)

Oh and I forgot to say: I found the patent because as always Wikipedia has an article about it (Poloxamer) and it was under references. Thermoreversible also appease to be the commonly accepted term for this property.Here is another example of its use. [20] Does this fully answer your question?--Aspro (talk) 21:22, 17 September 2010 (UTC)

hydrogen peroxide, oxidants and Lewis acids

I see we don't have any articles on Lewis acid catalysis, especially for organic redox reactions. I would eventually like to start an article on one (with appropriate research). I'm especially interested in some of these reactions as proof of concept things...when I search the literature I get really complex asymmetric catalysts -- while that's really useful I'd like to start from the basics. If I get papers from the 1870s -- even better.

H2O2 + Fe(III) + THF. Do I get an alpha-substitution? Do I get an acetal (assuming no cleavage), lactone or an ether peroxide? Or do I just get a catalytic decomposition of the hydrogen peroxide?

Cu(II) chloride + H2O2 + THF. If I get substitution, is it chlorination, peroxidation or hydroxylation? Or does the hydrogen peroxide reduce the Cu(II) to Cu(I), with the evolution of O2? Or just disproportionation of the hydrogen peroxide?

What if I use ice bath conditions?

p.s. can I prepare a solution of CuCl2 by pouring 30% H2O2 on copper and then reacting it with HCl? I actually have access to lab facilities where I can do this stuff (I mean I handle gold(III) chloride and perchloric acid regularly for biochem lab protocols...so), and a fume hood. John Riemann Soong (talk) 20:07, 17 September 2010 (UTC)

Hydrogen peroxide isn't actually all that great to work with as a reagent. IIRC, most of the time, if you require a peroxide, you use stuff like Organic peroxide and peroxyacids. Peroxides mainly work as radical initiators for things like radical halogenation and other reactions, because of the homolytic cleavage of the O-O single bond. Their use in oxidation reactions occurs by similar mechanisms. --Jayron32 20:23, 17 September 2010 (UTC)

Hmm, I seemed to think that by two-electron transfer, peroxide worked via the same mechanism as bleach -- a sort of SN2 attack on an electrophilic oxygen that would be activated by acid. I mean, they say "the O-O bond is weak" but the O-O bond is still quite a stable covalent bond. That is, OH* formation occurred but not rapidly -- just enough to jumpstart chain reactions. John Riemann Soong (talk) 23:02, 17 September 2010 (UTC)

The O-O bond is quite weak, but is stabilized in organic (alkylic) peroxides by the presence of electron donating groups, which alkyl groups tend to be. Hydrogen is a terrible electron donator, so in hydrogen peroxide, the O-O single bond is as weak as it is going to get; which is why hydrogen peroxide degrades fairly rapidly at room temperature or in strong light. --Jayron32 03:06, 18 September 2010 (UTC)

To answer the original question, using H₂O₂ with Fe(III) or Cu(II) will give you a form of Fenton's reagent. The original Fenton's reagent was with iron, but copper works as well: you simply need an element which can undergo one-electron transfer. Fenton's reagent is very effective at oxidation by oxygen transfer, but it's rather unspecific at where the oxygens go. Unsurprising really, given than the active species in Fenton oxidations is the hydroxyl radical! Physchim62 (talk) 08:45, 18 September 2010 (UTC)

Yes, you can make CuCl2 by reacting H2O2 and HCl with copper. I have 3% H2O2 and it works, albeit slowly. H2O2+HCl is a safe oxidizing acid. --Chemicalinterest (talk) 12:03, 18 September 2010 (UTC)

That's not how you'd usually make it though (assuming you have to make it instead of buying it). A standard prep would be to dissolve the copper in nitric acid, then precipitate the copper(II) as the hydroxide or the carbonate: wash the precipitate, then dissolve in the minimum of dilute hydrochloric acid to get your copper(II) chloride. Physchim62 (talk) 12:25, 18 September 2010 (UTC)

My lab doesn't have nitric acid. I don't have nitric acid. We do have perchloric acid though. Plus I'd rather spill 30% H2O2 than nitric acid eeek. Btw, Fenton's reagent appears to potentially be an oscillatory reaction. That's just fascinating....plus it's used in organic synthesis so it must have some selectivity if you have the right conditions? Esp. for alpha-oxidation? John Riemann Soong (talk) 17:54, 18 September 2010 (UTC)

Kitchen chemistry experiment

Hi. I poured sour lemonade into a bowl, then added some baking soda. At this point, mild fizzing occurred. I then proceeded to add leftover milk and mustard to the mixture, and slow mixing resulted. Afterwards, I added vinegar to the mix, which reacted with the baking soda. Next, I added more milk, and put in some ketchup. The next step was a surprise, as it produced an unexpected reaction. When I added some table salt to this mixture, it suddenly started fizzing, producing a white floating layer with a thick layer of small bubbles. Next, I put in some oil, which quickly expanded from small drops, and continues expanding. I put the bowl into the microwave for ten seconds. After that, I tried adding more salt to the mix, and an interesting thing happened. The salt fizzed as before, but within the oil regions, some salt crystals floated on top and did not dissolve, but a denser mass sank through the oil and the liquid underneath, and then rose up to form denser bubbles (denser because these were underneath the oil bubble layer). Within the oil areas, a line of bubbles from the salt began forming at the edges, but they were different in texture (if you could call it that) than the ones outside the oil. After a few more minutes, the oil bubbles proceded to expand, and the floating salt was replaced with a few bubbles, and convection started occurring when a layer of foam started in the middle of an oil layer and floated to opposite directions in a line, causing the oil layer/bubble to expand further. By the time I dumped out the contents of the experiment, the oil layer covered in patches most of the mixture's surface, with circular regions within and outside the oil layers that appeared white. Most of these regions had a foam surface on the outside, and in the central part there was an oily mass of the same bubbles that surfaced after the salt. At the end, when I poured everything out, a glob of white foamy substance remained stuck to the bottom and the bowl was left with an unappealing smell. Please help explain the following:

• What gases were produced by the reactions?
• What salts, other than the ones already present, were precipitated or dissolved into the mixture by the reactions?
• About how much water not already present was produced by the neutralization reactions?
• What factors caused the oil to expand?
• Did the microwaving have any chemical effects on the mixture?
• Why did the salt produce more fizzing than the reaction of baking soda with either the lemonade or the vinegar?
• Were any toxic or harmful compounds likely produced?
• What caused the bottom-sinking (and thus dense) glob?
• Were any plastic/polymer-like substances produced?
• What compounds were responsible for the smell?

If it is possible to answer the above questions with the information provided, please do so. This is not homework, nor am I requesting medical advice! Thanks. ~AH1^(TCU) 21:07, 17 September 2010 (UTC)

I think that's probably the most poorly designed experiment I have ever heard of, although I reviewed a paper once that was almost as bad. Not quite, though: they only had six manipulations all happening together, as opposed to the ten in your experiment. Looie496 (talk) 21:44, 17 September 2010 (UTC)

At each step, you need to test for possibilities by having diagnostic things to eliminate or confirm suspicions. That's how science is done. John Riemann Soong (talk) 23:00, 17 September 2010 (UTC)

I'll try to answer some of the questions.

• Carbon dioxide. I don't know what else would be produced.
• Many things contains acids, such as vinegar in ketchup, so sodium acetate should be a major salt. It is made by reaction of baking soda and vinegar. If citric acid was in anything, you may get sodium citrate.
• Water is produced by many acid-base reactions like you did, so quite a lot of water should be added.
• Surfectants? I don't know much in that area of chemistry so please help me out.
• Probably not, other than speeding it up by heating it.
• Please repeat your experiment with the salt and try some other acids. There might have been some discrepancy. Assuming you mean sodium chloride, it is neutral and does not participate significantly in an acid-base reaction.
• Hmm, probably not. Most chemical compounds that are in foods are either not toxic or in too small amounts to be toxic.
• Check out casein. It is a polymer that can be made from milk. You may have polymerized the milk. You also might have curdled the milk with the acids. This applies to the two questions.
• Vinegar has a strong smell. Several other strong-smelling acids may have been released as well as a mist of solution by the fizzing.

Hope this helps! --Chemicalinterest (talk) 23:22, 17 September 2010 (UTC)

While salt does not participate in traditional acid-base experiments, they (as you discussed so vigourously above) participate in redox reactions and solubility reactions. Salt denatures certain proteins. Salt especially likes to denature casein already under stress by acid. Vinegar should have been added in a side reaction as a diagnostic -- milk is already acidic. Thus you would be able to confirm whether it was the milk's acidity that contributed anything, or something else in the milk. Such is the protocol to deal with any complex mixture, as foods tend to be.

When you cook Western vegetables or chicken in water, a bubbly layer of "scum" often floats to the top -- these are organic complexes (of protein and other biochemicals) that have found new ways to interact and are no longer soluble in water, but do not have the density to precipitate. Ignoring boiling point changes, adding osmotic agents such as salt often produces more scum (so the decision to add salt early in cooking can be beneficial or harmful, depending on your purposes). John Riemann Soong (talk) 00:49, 18 September 2010 (UTC)

When you acidified sodium bicarbonate, you saturated the water with carbon dioxide, i.e. carbonated it. Adding salt to any carbonated beverage makes it bubble... though I'm not sure I've tracked down the definitive explanation for it yet. Wnt (talk) 04:56, 19 September 2010 (UTC)

Why not nucleation? I'd expect other factors, like specific ion effects, to be negligible in comparison. 109.155.33.219 (talk) 21:29, 19 September 2010 (UTC)

Mmm yes, nucleation. Diet coke and mentos anyone? John Riemann Soong (talk) 19:21, 20 September 2010 (UTC)

September 18

Symbolic suicide to end a delusional state

In many pieces of fiction, Vanilla Sky and Life on Mars (TV series) as good examples, a character is told that he is living in a dream world, and that to leave the world, he must take a "definitive step" and commit suicide in that world. Sometimes, within the fiction of the world, this is a trick being played on the character by outside forces, trying to trick him into believing that his surroundings are not real. But sometimes, in the fiction, it is not.

Is there any factual basis to this idea? Any real psychological delusional condition in which a person is living in a fantasy world, but can snap out of it and return to reality if they end their life there? Or is this notion entirely made up? gnfnrf (talk) 02:55, 18 September 2010 (UTC)

Broadly speaking, the sort of condition where one has fantastic delusions of this type is called Scizophrenia. There may be some delusions where people may believe the scenario you describe; however if these people kill themselves they are still dead. A mental illness like scizophrenia isn't cured because the sufferer commits a drastic act during a delusional state. --Jayron32 03:02, 18 September 2010 (UTC)

To be clear, in the scenario presented the subject is so delusional that he isn't taking any of the actions he imagines he is taking. He is really in a coma or other non-responsive state, and the world is in his mind. I'm asking if it is ever true that committing in that fantasy (without any real action) can ever break it and return a person to reality. Obviously committing suicide in the real world, even if surrounded by delusions, will result in being dead, not cured. gnfnrf (talk) 03:46, 18 September 2010 (UTC)

According to coma, people in a coma do not undergo standard sleep cycles, so it is unlikely they dream. I have little personal experience with anyone in a coma, but it is my understanding that they have little sense of time passing and no memory of dreams or delusions; if and when they wake up, the time spent in the coma is just "lost". --Jayron32 04:03, 18 September 2010 (UTC)

The answer is simple: no. There is no real condition that is anything like that. Looie496 (talk) 05:44, 18 September 2010 (UTC)

It's a literary/dramatic device. See Dave (Lost) for a different ending. ;) WikiDao ☯ (talk) 05:49, 18 September 2010 (UTC)

Well, an epiphany (feeling), particularly an epiphany about your own situation, might trigger some kind of tripped-out mental imagery such as imagining your own suicide, and emerging from a delusion is presumably a kind of epiphany. Delusional disorder says "Reports have shown successful use of insight-oriented therapy", sometimes, but this gradual process doesn't really square with your "take a definitive step", which sounds ritualistic and more like a part of the delusion than a way of beginning to make sense. It might be a good symbol for the falling of the scales from the eyes, though, for narrative purposes. 81.131.11.153 (talk) 10:31, 18 September 2010 (UTC)

My own OR here- I often have "bad dreams" which I realize to be dreams, but I'm not able to wake myself up. In such a case, the way I've learned to wake myself up is to kill myself. Jump off a cliff, throw myself into the jaws of the monster, etc. This fits perfectly the description of a "delusional condition in which a person is living in a fantasy world, but can snap out of it and return to reality if they end their life there". (Only difference I guess is that I know for sure the dream is a delusion.) Staecker (talk) 12:29, 18 September 2010 (UTC)

That doesn't seem a very safe thing to have trained yourself to believe. Much safer to decide that pinching yourself or saying some set phrase will always wake you up. 86.164.78.91 (talk) 16:06, 18 September 2010 (UTC)

Why not? I have never thought I was dreaming when I wasn't. Never even once considered throwing myself into the jaws of the monster in real life. Staecker (talk) 16:14, 18 September 2010 (UTC)

I've had enough dreams where I 'wake up' multiple times, each time seeming more convincingly real than the last, that I no longer assume I'll always be able to spot what is and isn't a dream, so I tend to consider it bad practice to establish a rule like that. You might never jump into the jaws of a real monster, but cliffs and jumping off them are real things, and mindstates exist in which stressed people find the real world taking on a dreamlike quality. But, everyone assesses their own risks: I'd always lead myself to believe something safer. 86.164.78.91 (talk) 17:12, 18 September 2010 (UTC)

Do you habitually sleep on the edge of cliffs? :) Matt Deres (talk) 14:15, 20 September 2010 (UTC)

I've definitely had dreams that I couldn't wake up from, even when I was pretty sure they were dreams, and I've had various waking states that I was unable to distinguish from dreaming. --Mr.98 (talk) 18:49, 18 September 2010 (UTC)

Killing yourself to prove a dream sounds like a bad plot device, and it's hard to picture any way that it could be unique psychologically. After all, there's nothing to prevent you from continuing with the dream, flying up to the pearly gates, or visiting one of Hell's many fine bordellos. (Your pick ;)) I should say though, that I do think that situations requiring a certain kind of rational analysis tend to cause waking, and it is possible that if deciding what comes after death is such a thing, then it might do so. But for example, most frustratingly, I've found that simply looking at something pretty in a dream and trying to make a note of the exact design and measurements so that I could try to draw it later is the sort of thing guaranteed to cause wakefulness. I don't think that the exact limits are absolutely hardwired - for example, sometimes it is marginally possible for to read in a dream, and other times the effort fails and risks awaking. Wnt (talk) 04:47, 19 September 2010 (UTC)

Have you given lucid dreaming a try? WikiDao ☯ (talk) 04:59, 19 September 2010 (UTC)

I haven't pursued it seriously. I'm almost always aware at some level that a dream is a dream, and to be honest, the technical quality usually isn't very good - until a mental reorganization around 17, I actually dreamed in black and white most of the time, and reds and yellows are still not very strong, and tactile or scent stimuli are extremely rare. So I should admit that I don't directly share the OP's perspective. Sometimes I take on the perspective of more than one character in a dream. The plots are sometimes rather elaborate, and most distinctive is that the dreams often have a huge, very strange background, all of which is taken for granted - (e.g. that I'm a cyclops living underground in a post-nuclear society, or a pampered child in a future society who can call out the names of my pets to transform them from plastic sculptures of words into snuggly animals). So I suppose I don't quite know what to do with lucid-dreaming. Deviating from the script would only seem to degrade the experience. Remembering them better might be nice, but I think the whole point of the dream is to dissort memory without such crude interference. Wnt (talk) 05:42, 19 September 2010 (UTC)

I think the OP's question boils down to: is there any factual basis to the existence of an afterlife? And the weight of evidence seems mostly against at this point. WikiDao ☯ (talk) 04:59, 19 September 2010 (UTC)

what evidence would that be? --Ludwigs2 05:27, 19 September 2010 (UTC)

For an afterlife: religious teaching, wishful thinking, and the like. Not very hefty, concrete data. Against an afterlife: every time anyone dies, they seem for all intents and purposes to remain quite dead (these days). The balance of evidence seems clear. I do not mean to disrespect anyone's beliefs, or dispute with them about their belief in an afterlife. But the answer to the OP's question seems to me ultimately to be that there is no quote "factual basis" to support anything further happening to someone when that someone dies. As far as anyone knows, you do not "wake up" from what you delusionally-or-not firmly believe to be your "life" when you "die". Even if you are delusional, and you die: you're still dead. That's all I meant. WikiDao ☯ (talk) 05:42, 19 September 2010 (UTC)

It is putting the cart before the horse to speak of what you experience in the afterlife, when who can say why you experience things now? Replacing all or part of the brain with a robotic replica would seem to abolish experience, but who can give the technical explanation? Who could be trusted to accurately report the experiment if it were done? Is there any logic to the notion that a person "feels" what one human body experiences, but never "feels" what another experiences, when "a person" logically should be definable as some process involving atoms which may continually exchange positions with one another and have no distinct identity? [I speak of feeling, obviously not of remembering when in one brain what has been experienced in another] (see also Atman (Hinduism))

But beyond this is a separate question, that the afterlife is "after" life in what dimension of time? In the physical time dimension of the universe moving toward its end — or in a spiritual dimension of time as a Creator tears down one cosmos and builds another more perfected? Because no measurement you take in physical time to determine natural laws can tell you what laws link the progression of spiritual time. Wnt (talk) 05:52, 19 September 2010 (UTC)

Hence: no evidence. The data is either non-existent or non-attainable at present. WikiDao ☯ (talk) 05:58, 19 September 2010 (UTC)

"Absence of evidence is not evidence of absence". Rational thought is rightly valued, and yet the mind demands to think in other ways; perhaps this is not a joke or a mistake, but also a meaningful manner of perception. Wnt (talk) 06:19, 19 September 2010 (UTC)

Just wanted to add to your initial list of movies. Total Recall is another example that contains the situation mentioned by the OP. 10draftsdeep (talk) 14:26, 20 September 2010 (UTC)

Back to the beginning: "Is there any factual basis to this idea? Any real psychological delusional condition in which a person is living in a fantasy world, but can snap out of it and return to reality if they end their life there? Or is this notion entirely made up?"

Just to be clear: you are asking about a case where someone is so delusional that their entire fantasy world seems completely real to them, right? And there is no way for them to know that it is all just a delusion except by dying and seeing if they then wake up in "reality". Right? This sort of thing gets portrayed in many books and movies. You want to know if it has ever really happened. And I do not find any formal studies to provide a "factual basis" for that having happened before. And I do not imagine it is in common practice in the psycho-therapeutic treatment of delusional people, either. So my best guess is that it is an entirely made up notion. Hope this helps. :) WikiDao ☯ (talk) 15:31, 20 September 2010 (UTC)

Physics question

Hi, I'm having some trouble with a problem on my Physics homework. This might be a bit rudimentary considering some of the other questions you get here, but bear with. The question is "A motorboat travelling on a straight course slows down at a constant deceleration from 70 kph to 35 kph in a distance of 50 m. Find the acceleration" In the textbook we are given an equation, v_final² = v_o² + 2as. Plugging in I get 1225 kph = 4900 kph + 2a(0.05) and from there -3675 kph = 2a(0.05), but that gives me a huge number that obviously can't be right. What di I do wrong? Thanks. —Preceding unsigned comment added by 24.92.78.167 (talk) 03:11, 18 September 2010 (UTC)

OK, we are not really allowed to solve homework here, but we are allowed to give hints, so I'll hive you a hint: in what units do you want to express a? --Dr Dima (talk) 03:27, 18 September 2010 (UTC)

Why can't it be right? You haven't defined your acceleration units; if we assume hours to be your time unit and kilometers to be your distance units, then your acceleration would be in units of km/hr². I don't have an intuitive sense of how big that answer should be in those units, so I don't see why the size of the answer would surprise me. --Jayron32 03:28, 18 September 2010 (UTC)

Here is another hint. When you multiply 35 times 35 you get the square of 35. When you multiply kph by kph you should get ... (But what did you get?) Dolphin (t) 04:27, 18 September 2010 (UTC)

Something that I found makes problems a lot easier: convert your initial speeds to metres per second and your distance to metres so everything uses SI units. I've run through the calculation with those and it spits out a reasonable answer. Brammers (talk/c) 08:00, 18 September 2010 (UTC)

If your question is homework, show that you have attempted an answer first, and we will try to help you past the stuck point. If you don't show an effort, you probably won't get help. The reference desk will not do your homework for you. This is the reference desk guidelines for homework questions. The original poster did show that they have attempted an answer first. The only restriction against solving homework questions is where the original poster only posted a question without showing that they are doing any work. --Chemicalinterest (talk) 11:26, 18 September 2010 (UTC)

That isn't the only restriction. Even if they've tried, we don't solve it for them: we help them solve it themselves. Accordingly, people above have been giving hints to help the question asker to solve this problem themselves: the value of homework lies in solving the problem and doing the work. The guideline above (in full) does a pretty good job of capturing this consensus view. 86.164.78.91 (talk) 15:58, 18 September 2010 (UTC)

Before plugging in numbers, rearrange the textbook equation so it states directly the acceleration

$a={\frac {v^{2}-u^{2}}{2s}}$

Then plug in the numbers paying attention to the units you use. These conversions can be handy:
1 kilometer = 1000 meters.
1 m/s = 3.6 kph.
Deceleration is the same as acceleration with a negative value. Cuddlyable3 (talk) 17:24, 18 September 2010 (UTC)

Phonetic equipment

User:Textorus has suggested that Wikipedians who patrol the science desk could have some information about good sound-sampling equipment for spectrogram analysis regarding my question over on the language desk. Thank you--el Aprel (^facta-_facienda) 04:06, 18 September 2010 (UTC)

Need to break this down into discrete parts. (1) Are you satisfied that the Laptop's sound card is up to recording at the quality that you want. No mic will make a poor card sound good. If not a external sound card would cheaply get around the problem. I don't know about the differences but others might, so what is the laptop and what is the existing sound card? Something like this I guess, has the right sort of specs for what you need in a good external USB sound card. [21] You can plug an ordinary mic straight in without the need for getting a USB mic. Ambient noise when recording outside an echo free and sound proofed studio can be a big problem, so to understand the jargon and principles about the different methods of filtering here are two articles on how to mitigate unwanted noise. noise-canceling microphone , Active noise control. Yes. Dynamic mics are much much better that condenser types. Someone else might be able to expand on this but off the top of my head I would think with the external audio interface and two microphones it would allow for good noise rejection without losing dynamic response or loss of frequencies, but I don't have practical experience how well the software works. Having one mic very close to the speaker certainly helps a lot in getting a clearer signal.--Aspro (talk) 08:23, 18 September 2010 (UTC)

You can download Visual Analyzer free and immediately see your laptop perform as a spectrum analyzer. Cuddlyable3 (talk) 12:52, 18 September 2010 (UTC)

Harmful to handle frogs, then release them?

What does the last sentence in Gigging#Frog_gigging mean? Does it really harm frogs to catch them, hold them, take some pictures of them, and release them? diff--Chemicalinterest (talk) 12:43, 18 September 2010 (UTC)

This guide cautions "Don't wear any sunscreen or bug spray on your hands. Not only will it make your hands slippery, it will harm the frogs because the[sic] will absorb the chemicals through their skin." Cuddlyable3 (talk) 13:04, 18 September 2010 (UTC)

I like to catch frogs and take pictures of them. I do not use any chemicals on my hands. I was wondering when I read the article whether handling them really harmed the frogs, other than the temporary sluggishness they get from repeatedly trying to escape and failing. --Chemicalinterest (talk) 15:23, 18 September 2010 (UTC)

As long as you handle them carefully (remembering that frogs absorb air and chemicals through their skin and are not the most physically robust creatures ever created), the frogs should be fine. Don't disturb them during breeding periods, obviously, don't hang onto them for more than a couple of hours, and make sure you put them back more or less where you found them, and it should be fine. — Preceding unsigned comment added by Ludwigs2 (talk • contribs)

OK. I'll make the gigging article less ambiguous. --Chemicalinterest (talk) 20:18, 18 September 2010 (UTC)

Inquire about semen and its impact on the face

Dear All, Have a nice day,

I have read in several forums, websites & here at wiki that the semen of a man is good for women.

Could be that she are using on the skin for a moment the emission of semen

And also helps build up the body because it contains a quantity of protein and textural material of your own if the woman drinking it down to luck.

Thanks for co-operation Ahmed atoon (talk) 12:57, 18 September 2010 (UTC)

The Wikipedia article about Semen has the information we can give. Cuddlyable3 (talk) 13:48, 18 September 2010 (UTC)

You may find this article interesting - [22]. Exxolon (talk) 17:18, 19 September 2010 (UTC)

Downloading a brain to a computer (part 1)

You know the idea that eventually we'll be able to download our brains/personalities to computer, to achieve physical immortality? Are there currently any theories as to how you could actually 'capture' the brain to do the transfer? Spoonfulsofsheep (talk) 15:03, 18 September 2010 (UTC)

Yes, I know the idea. Wikipedia has articles about Digital immortality and Mind uploading. Cuddlyable3 (talk) 16:57, 18 September 2010 (UTC)

Thanks, the mind uploading link was particularly useful! Spoonfulsofsheep (talk) 14:51, 19 September 2010 (UTC)

Downloading the brain (part 2)

Any theories about what areas of the brain would need to be downloaded? I know this would be very speculative but are there any papers on what is needed to retain 'you'? Spoonfulsofsheep (talk) 15:11, 18 September 2010 (UTC)

Downloading creates a copy of the original. The original is still there in the brain; "you" is not retained in the downloaded version, it's another "you" entirely. 82.44.55.25 (talk) 18:14, 18 September 2010 (UTC)

Well, so says one theory of things. A lot of it depends on what you define as "you". It's heady philosophical territory. --Mr.98 (talk) 18:45, 18 September 2010 (UTC)

The articles recommended to you in (part 1) are also probably good places to start for this part, too. But see also the recent film Moon for a dramatic treatment of this sort of thing (I mean the film, not the article, unless you want the spoiler first). WikiDao ☯ (talk) 19:27, 18 September 2010 (UTC)

The film Moon was moderately entertaining, but the (unrelated) novella Rogue Moon was much better. Wnt (talk) 04:28, 19 September 2010 (UTC)

That's debatable 82.44, if I make a copy of a digital file on my harddrive, is one the original and one a copy? I would say no. I would say that they're both the same file, it's simply in two places now.

If I new for a fact that next week my mind would be copied, and that one of the copies would be destroyed, then right now I'm cool with that. The person I am now will survive. (After the copy has been made, I'm sure that each of me will have some rather strong opinions on which one should live and which should be destroyed. But to me right now, I don't care. The pre-copy me survives either way.) APL (talk) 20:05, 18 September 2010 (UTC)

The original files creation and modified dates would be different from the copied file, yes? They are identical in every way, but the original is still the original, occupying the same clusters on the hard drive it did before the copy was made. The copy is taking up a new part on the drive that was empty before the copy was made. They might be identical, but they're not the same file. I'm confused about the second part of your comment. Are you talking about 2 copies being made and then one of the copies being killed, or are you talking about one copy being made and the choice of who is killed being between original you and the copy? If it's the first one, then I agree; I don't care what happens to two copies of me. But if it's just one copy, then you're basically saying next week there's a 50% chance you'll be killed, and a copy with take your life. Maybe I think differently, but I would not be ok with that at all. 82.44.55.25 (talk) 20:24, 18 September 2010 (UTC)

Certain file copy tools will keep the file creation and modification times. Also in terms of your cluster thing, what happens when you defragment and the files are moved around? Sure you can track which version goes where, but why is either one the original? In your philosphy the original is lost when you defragment since the file is read into memory, written in another location then deleted or overwritten in the original location. But why are you even calling that the original? If I write a file, very often it will be written to memory first before going to disk. But is even the copy in memory the original? What about whatever is going on in the CPU to make the file?

In other words, I agree with APL here. For the precopy self, there's no reason why either version is more me then the other version. I'm not saying I would be happy with either me being killed, I guess I'm self centred in that way :-P But if one does have to be killed, and both are exact copies, there's no real reason why me the precopy self should feel more strongly about either version. Of course, either way whoever is going to murder me should go to jail for the rest of their lives. In the Star Trek world apparently everyone is like APL hence teleporters.

Nil Einne (talk) 21:07, 18 September 2010 (UTC)

Yea, exactly. I'd like to go to the Moon, if the only way for me to get there was to make a copy of me on the Moon and destroy the original here on Earth, I'd be fine with it. My only condition is that the original is destroyed more or less immediately after the copy is made so that it doesn't have time to think about it's fate as the non-surviving me. APL (talk) 22:23, 18 September 2010 (UTC)

I would not be fine with dying and a copy of me living my life, at all. I also would never use a transporter. But that's just me, I guess 82.44.55.25 (talk) 22:43, 18 September 2010 (UTC)

Are you fine with a machine that constantly replaces every molecule in your body with new ones? That's what's happening all the time: very few of the molecules you had when you were born are still inside your body. --140.180.0.120 (talk) 03:00, 19 September 2010 (UTC)

That's very different to being copied, killed, and your copy going to the moon. 82.44.55.25 (talk) 11:13, 19 September 2010 (UTC)

Perhaps clarifying slightly : I consider the important part of "Me" to be my mind and memories. That's just data. For data "original" and "copy" have little useful meaning. (If I create a file and save it. Is the file on disk the original? Or was the original in RAM and now destroyed? If I open the file again, change one letter, then re-save it, the file is loaded into ram, wiped from the disk, then re-saved to the disk, possibly not even in the same physical location. Is the file still 'original'? Was it ever?)

If my mind were transferred or copied into a different physical body I would still consider myself to be the same "me" I always was. APL (talk) 22:38, 18 September 2010 (UTC)

Where a distinction between original and copy becomes important is a situation when the copy has inadvertently omitted some vital piece of information from the original. Most people with a religion will believe that they possess a soul, so do you believe that the soul has been copied into the copy and that two souls now exist where before there was only one? Even putting that aside (which as an atheist I am obliged to do, but I would still find the whole idea of destroying the original very frightening) there is still the possibility that the copying process has failed to copy some vital piece of information stored in an unexpected place. Copying a data stick, for instance, might be considered fairly safe, until you realise that the password was written in pencil on the original which, of course, will not have been copied by the computer. Destroying the original will have made the data unusable forever. It is possible that some aspect of human identity is likewise stored in a place completley unsuspected by medical science, for instance, I don't know, my left big toe. Copying data from the brain only is going to miss this and destroying the original will make the mistake unrecoverable. SpinningSpark 23:19, 18 September 2010 (UTC)

Well, I wasn't imagining someone saying "Here's my new human duplicator! Time to test it out for the first time ever, and then immediately murder the test subject!" There would doubtless be all sorts of subtleties to the process that would need to be worked out. APL (talk) 00:17, 19 September 2010 (UTC)

The Transhumanism article has a general discussion of some issues related to your question (both parts) that you may find interesting. WikiDao ☯ (talk) 21:45, 18 September 2010 (UTC)

Your knowledge and memories are most likely stored mainly in the cerebral cortex and hippocampus. Your emotional memories are probably stored at least in part in the amygdala; your habits and desires are stored at least in part in the basal ganglia. Your personality is modulated by a bunch of small subcortical areas. In short, a whole bunch of brain areas come into play, although the cerebral cortex is almost certainly by far the most important. Looie496 (talk) 22:22, 18 September 2010 (UTC)

I mentioned a paper here recently in a question of my own that discusses this question a bit: "Are you living in a computer simulation?". See especially the second section, "The assumption of substrate-independence", which argues that one would have to basically model on the computer the structure and activity of the human brain down to at least individual synapses. You need a whole human brain for a ("normal") whole human mind, so the answer to your question is really: all of the brain, down to each and every 1000 trillion (10¹⁵) synaptic connections. WikiDao ☯ (talk) 01:50, 19 September 2010 (UTC)

But is reproduction of every physical detail the same as preserving identity? Plutarch observed that is a controversial question. Cuddlyable3 (talk) 11:59, 19 September 2010 (UTC)

From your wl: "Plutarch thus questions whether the ship would remain the same if it were entirely replaced, piece by piece." This is (very weakly) similar to the notion of "substrate-independence". The thing here is that there is no discontinuity: the underlying substrate may change, but you are the same person from moment to moment. Then Hobbes gets closer by wondering "what would happen if the original planks were gathered up after they were replaced, and used to build a second ship." Here, there is a big "discontinuity" and probably also a different ship (by convention) unless it is exactly reproduced with the same material. Above, we are talking about reproducing ("modeling") the structure and action of your 10¹⁵ synapses as software code that can be run on a different substrate altogether: some really serious but theoretically possible future hardware. It's not your great^x-grandfather's question anymore. ;) Would "your" subjective experience as "you" be replicatable by such a process? Consensus these days seems to be: yes, it would. And see the paper for more... WikiDao ☯ (talk) 14:39, 19 September 2010 (UTC)

(OP here) Thanks for all the answers and links everyone. Just had a quick flick through so far but there's a lot of interesting information for me to digest :-) Spoonfulsofsheep (talk) 15:28, 19 September 2010 (UTC)

You're welcome! And come back any time! WikiDao ☯ (talk) 15:37, 19 September 2010 (UTC)

Don't forget to read this article Count Iblis (talk) 03:05, 20 September 2010 (UTC)

Judean date palm from 2000 year old seed

Is there any news about this? I read somewhere that it may fruit in 2010, if it is female. Has its gender been identified yet? It would be nice to green the desert with it, as it was in historical time. Why did it die out? The article does not say. Thanks. Edit: The Reuters link says it is female, but the article implies that its gender is not known. On looking more closely, the article says it died out due to being no longer cultivated. 92.28.255.54 (talk) 15:33, 18 September 2010 (UTC)

Bzzzzt!

The AC adapter for my laptop says that its output is 4.5A at 20V. What will happen to me if I put the output end in my mouth while the input end is plugged in?

Thanks, —Mark Dominus (talk) 17:46, 18 September 2010 (UTC)

You will get a Darwin Award. 92.15.24.80 (talk) 17:50, 18 September 2010 (UTC)

Okay, but I won't get a Darwin Award for licking the terminals of a 9-volt battery, so what's the cutoff? Is 14 volts enough to get me the award? If not, how about 17? —Mark Dominus (talk) 19:11, 18 September 2010 (UTC)

Current, be it AC or DC, is generally acknowledged as a more dangerous parameter than voltage. We have an article on the lethality of electric shock. — Lomn 19:50, 18 September 2010 (UTC)

I disagree. I don't think that 20 V, localized in the mouth, is going to kill you (I could be wrong; don't try this at home). If you let the current pass through your heart, then sure, it's possible to kill yourself with 20 V (or even 9 V, as this real life recipient of a Darwin Award did [23]). But you stick your tongue over a potential difference of 20 V, and I bet the current mostly just passes through the tongue, between the electrodes, giving yourself a nasty shock (and possibly burns) (again, please don't test this yourself). Buddy431 (talk) 19:59, 18 September 2010 (UTC)

I call out that Darwin Award as a hoax. What is the maximum short circuit current from that ohmmeter? What is the name of the person who was killed, and where is a reference to an actual accident investigation report? It smacks of a pious fraud intended to prevent students from doing foolish things with electricity. Edison (talk) 02:11, 19 September 2010 (UTC)

See Electroshock weapon for a good point-of-reference here. WikiDao ☯ (talk) 20:40, 18 September 2010 (UTC)

I think you may get a mild shock, but most of the current will flow through the saliva that gets into the connector and shorts the connection -- most likely the main thing that will happen is that you will blow the fuse in the adapter. Looie496 (talk) 22:16, 18 September 2010 (UTC)

How many molecules in a cubic metre of iron?

At room temperature and pressure. Thanks 92.15.24.80 (talk) 17:49, 18 September 2010 (UTC)

Iron doesn't come in molecules; that's not how metallic bonding works. They'll be about 8.5×10²⁸ atoms, though. Algebraist 17:53, 18 September 2010 (UTC)

See also Molecule#History and etymology for clarification on that point. WikiDao ☯ (talk) 18:01, 18 September 2010 (UTC)

And to explain how Algebraist (might have) derived his answer, 1 cubic meter contains 1,000,000 cubic centimeters, which has a mass of 7,874,000 g (nearly 8 Tonnes, or over 8.5 Tons if you live in North America) (see Iron, where density is listed as 7.874 g/cm³ near room temperature). We then divide by the molar mass of iron (55.845 g/mol) to get about 141,000 moles of iron atoms. Multiply this by Avagadro's number, 6.022x10²³, to get the total number of atoms, about 8.49x10²⁸, as Algebraist already said. Buddy431 (talk) 23:48, 18 September 2010 (UTC)

Thanks, I used that to help estimate the answer to the Bonding with the Rocket question above. 92.15.17.68 (talk) 16:37, 19 September 2010 (UTC)

Using the definition of a molecule rather loosely, you could argue that the answer to the question is "1". ←Baseball Bugs ^{What's up, Doc?} carrots→ 18:15, 19 September 2010 (UTC)

Bugs, do you have any reference or source for any reliable metallurgy or chemistry resource that uses that terminology? That is strictly incorrect usage of the word molecule. A block of solid iron could be a polycrystalline lattice or a single monolithic crystal lattice, but it is not correct to say it's "one molecule." Nimur (talk) 04:42, 20 September 2010 (UTC)

Flash

Is it safe to use a third-party flash with a different camera, even if the flash is made for that camera? I do know that a film flash with a digital camera will fry it. Is that risk still plausible here? --The High Fin Sperm Whale 18:42, 18 September 2010 (UTC)

As long as the third-party flash is specced to the camera in question, it's fine -- and I seriously doubt that "film flashes" intrinsically fry digital cameras. That's certainly not the case with mine (though I've found combinations that simply don't work together). — Lomn 19:48, 18 September 2010 (UTC)

Sorry, I can't answer your question, but do you have a cite for that thing about older flashes "frying" a digital camera? I've never heard that before. My father is a professional photographer and he certainly didn't replace all his lighting equipment when he switched over to digital. APL (talk) 19:59, 18 September 2010 (UTC)

It is the trigger voltage that has to closely checked. Canon for instance doesn't like anything over 6v (from memory so please check) Older flash guns often meter around 24v and this can damage some cameras. Modern camera's have got more voltage sensitive equipment inside that talks to the gun. If the third party gun is of a reputable make and the trigger voltages are within spec then it ought to be OK. With flash, I tend to keep to the camera's brand and high guide numbers and say to hell with the cost, because at the end of the day it saves so much hassle to let the electronics do all the work. However, that doesn't mean it results in photos that are any better. --Aspro (talk) 20:45, 18 September 2010 (UTC)

As stated above, you need to be aware of the trigger voltage, there is a teble here - http://www.botzilla.com/photo/strobeVolts.html - that lists many major strobe units and the sync/trigger voltage can go above 200V on older units.

Your assumption that a "film flash on a digital camera will fry it" is incorrect as I have used a Nikon SB28 on my D80 quite safely, but the SB28 does not support the newer iTTL system.

However, given that different manufacturers use differing pin configurations for communication between strobe and body, you can't be sure that using say a Canon strobe on a Nikon will not cause problems. Dlegros (talk) 21:21, 18 September 2010 (UTC)

Even if it doesn't damage the camera you WILL lose all the automatic functions in the camera/flash and you'll have to set all the flash settings on the flash yourself. Usually it's not worth the hassle to use offbrand flash. --antilived^{T | C | G} 05:15, 20 September 2010 (UTC)

wood chips

are those pine wood chips that you put in hamster cages made of real wood or is it made from like recycled particle board or chipped up pallets or something? —Preceding unsigned comment added by Kj650 (talk • contribs) 19:35, 18 September 2010 (UTC)

Well if you are in Australia it would be fresh wood chips made from timber useless for boards, made in a wood chip mill. The original wood comes from a pine plantation. You can also get pine bark chips or fines, and hardwood chips, that take longer to rot. Recycled timber is much more likely to contain preservative, nails or paint, and so be unsuitable for animals, (or gardens). Graeme Bartlett (talk) 20:25, 18 September 2010 (UTC)

im in the usa. but i think the pine chips come from china. —Preceding unsigned comment added by Kj650 (talk • contribs) 21:42, 18 September 2010 (UTC)

why isn't Iron(III) nitrate just as dangerous as nitric acid or iron(III) chloride?

Like Cl-, NO3- isn't that great of a conjugate base. AFAIK NO3- doesn't like to coordinate to much of anything, making it more spectator than Cl- (except in redox reactions). In addition, surely Fe(III) nirate is a Lewis acid analogue of nitric acid...? Or is it that Fe(III) nitrate (or a solution of it) isn't very skin-permeable, whereas nitric acid is a skin-permeable oil? John Riemann Soong (talk) 21:33, 18 September 2010 (UTC)

What makes you think that iron(III) nitrate isn't as dangerous as iron(III) chloride? Physchim62 (talk) 23:46, 18 September 2010 (UTC)

Look at the safety diagrams given for each chemical. Fe(NO3)3: 1 for health, and 1 for flammability. FeCl3: 3 for health, and 2 for reactivity. John Riemann Soong (talk) 00:08, 19 September 2010 (UTC)

Compare the pH of a concentrated Fe(NO3)3 solution with a FeCl3 solution. The nitrate ion is an oxidizing agent; do not forget that. --Chemicalinterest (talk) 00:25, 19 September 2010 (UTC)

I don't have an approximate pKa value for Fe(III)'s Lewis acidity, but it shouldn't change much. Cl- and NO3- are both very weak conjugate bases, and the differences in basicity only appear in very high H+ concentrations. John Riemann Soong (talk) 00:38, 19 September 2010 (UTC)

(edit conflict) NFPA diamonds are a joke: hopefully we'll be able to get rid of them from Wikipedia in a few months' time. The pH of a 1 M Fe(NO₃)₃ solution and a 1 M FeCl₃ solution are both around zero, and this is the hazard that naïve students ignore: [Fe(H₂O)₆]³⁺ is a pretty strong Brønsted acid. There is an additional hazard from anhydrous FeCl₃, in that it will give off HCl gas on contact with the moisture in the air and so it can be classified as a respiratory irritant (Japan does, New Zealand doesn't from the official classifications I've found). Physchim62 (talk) 00:42, 19 September 2010 (UTC)

And the additional hazard from Fe(NO3)3 would be its oxidizing capability. --Chemicalinterest (talk) 10:43, 19 September 2010 (UTC)

I've updated the safety info on iron(III) chloride and iron(III) nitrate. Both sets of NFPA values were wrong: Fe(NO₃)₃ is not flammable, example. For FeCl₃, I found a collection of NFPA values which all agreed on 2-0-0, so that's what I put. For Fe(NO₃)₃, there is a fairly typical ridiculousness in the range of published values, from 1-0-1 [24][25] to 2-0-0 [26][27] to 3-0-0 [28] to 3-0-1 [29] to 2-0-3 [30]. This is why NFPA 704 is simply "not fit for purpose" in laboratory safety. Physchim62 (talk) 22:36, 19 September 2010 (UTC)

Ok thanks for the clarification. But I notice nitric acid is really dangerous. Won't ferric nitrate dissolved in water produce nitric acid? AFAIK 1M nitric acid is a thing much worse than 1M HCl. John Riemann Soong (talk) 02:24, 20 September 2010 (UTC)

It probably will produce an equilibrium between nitric acid and ferric hydroxide. It is used in etching, don't forget, so it must be quite corrosive. --Chemicalinterest (talk) 11:06, 20 September 2010 (UTC)

Inverted leaves on plant

The plant

cucumber

I was looking over some old photos and found this odd plant whose leaves appear inverted. Could someone tell please tell me which plant this is and why its leaves appear inverted?Smallman12q (talk) 19:56, 18 September 2010 (UTC)

Inverted? WikiDao ☯ (talk) 22:11, 18 September 2010 (UTC)

It looks like a courgette or marrow or cucumber. The inverting might be due to a breeze. 92.15.24.80 (talk) 22:13, 18 September 2010 (UTC)

There's no breeze in the photograph...?Smallman12q (talk) 22:35, 18 September 2010 (UTC)

How could you tell? The lower leaves may be wilting. Sometimes lower leaves of plants wilt and wither in dry conditions. 92.15.24.80 (talk) 22:54, 18 September 2010 (UTC)

You can also look up the plant on sites such as the New York Flora Atlas and the New York Natural Heritage Program Plant Guides. ···日本穣^? · 投稿 · Talk to Nihonjoe · Join WikiProject Japan! 22:49, 18 September 2010 (UTC)

Initial examination indicates a member of the cucumber family but if you look closer at the flower you will notice some tightly enclosed green bracts at the base of the petals. These are not characteristic of the cucumber family although the male flower does sometimes show some twisted residual bracts. It looks more like a member of the mallow family to me. Richard Avery (talk) 11:52, 19 September 2010 (UTC)

I've never heard or seen anything in the mallow family having yellow flowers. 92.15.17.68 (talk) 16:40, 19 September 2010 (UTC)

Viruses in food manufacture

The manufacture of many foods, such as yoghurt, natto and kimchi, involve bacteria in an essential way. But what about viruses? Of course, viruses are much simpler, so the mechanism would have to be different. But are there, for example, foods made from virus-diseased plants? --196.215.14.166 (talk) 21:04, 18 September 2010 (UTC)

Viruses have been used to develop genetically modified food such as through virus-induced gene silencing.Smallman12q (talk) 21:30, 18 September 2010 (UTC)

Viruses turn living cells into factories to make more viruses. At best, the cells return to normal, at worst they become just dead versions of live cells. Therefore, a Virus strain which infected veg/meat/etc. may result in a slight change in taste but they would not confer any useful change to the food -as far as I can see. Also, and here is the killer: As viruses need living cells, it would be an impossible possess to control. The would be food (being live) would strive to become immune. Bacteriophages however, are beginning to be used to control the bacteria that can spoil food. --Aspro (talk) 23:29, 18 September 2010 (UTC)

Not food, but the Tulip breaking virus was historically used to make variegated tulips, which were actually quite highly prized (see Tulip Mania). The diseased tulips actually sold for much higher prices than ordinary tulips, due to their unusual coloring (and the fact that the disease made it harder to grow the tulips). I don't think people intentionally grow infected Tulips anymore (they have healthy, multicolored ones now), but it's at least a historical example of something similar to Mr. 196's query. Buddy431 (talk) 23:36, 18 September 2010 (UTC)

You have to understand a bit about why bacteria are so useful in foodmaking in this way, while viruses are not. Some bacteria (and some yeasts, and some molds, and some fungi, etc, etc.) produce waste products which are tasty. Generally these are things like lactic acid and ethanol. Bacteria produce these by eating the food in question, and then eliminating the tasty biproducts as waste (not to be crude, but its essentially bacterial poop). The deal with viruses is, they don't eat. They don't poop. Viruses, while composed of living material, are not really proper living organisms. They are basically little nuggets of genetic material which insert themselves into cells and reproduce themselves that way. They do not do anything on their own; they contain no energy producing bits; they consume nothing and produce nothing. So they aren't terribly useful in making food taste better. --Jayron32 03:18, 19 September 2010 (UTC)

To elaborate on that a little more: viruses usually have a small number of genes (not always - smallpox being an exception, carrying a Hollywood diva's worth of baggage). These genes are usually pared down to bare essentials, because a virus with more genes will replicate a little more slowly and not keep up with its lighter fellows. By "essentials" I mean proteins and perhaps some small RNAs. These build new viruses and fool with the host cell. The problem is, by and large, when you taste something, you're tasting some small chemical, not a protein. I suppose it's kind of hard in a cell made up of proteins for a receptor to be very sensitive to new proteins from the environment - even the immune system has a lot of trouble spotting new ones and telling them from old. So it's hard to have a virus where a potato infected with it suddenly tastes like cinnamon - it doesn't have the wherewithal to make cinnamaldehyde, etc. Now it is theoretically possible to have a virus that would intensify or alter a plant or animal's production of some flavorful compound, but I can't think of any example - it'd be a rather odd thing for it to do, and domestication of a plant should strive to achieve the same effect all the time by its own genetics. Wnt (talk) 06:39, 19 September 2010 (UTC)

Thermal vest?

I was wondering whether thermal vests are actually much better than a regular t-shirt at retaining heat and came to Wikipedia to find no article on thermal vests?? Are they known by another name? --178.98.60.118 (talk) 22:29, 18 September 2010 (UTC)

If you have a wp:rs, you can create an article. I created a blank for you. --Chemicalinterest (talk) 22:50, 18 September 2010 (UTC)

We have thermal underwear which redirects to "long johns" but at least covers the concept. SpinningSpark 23:28, 18 September 2010 (UTC)

Neither is there an article on string vests. These were worn under a shirt, and had been scientifically designed (during WW2?) to be warmer than a normal vest, despite being full of holes. I think men stopped wearing them in the 70s. 92.15.12.54 (talk) 23:34, 19 September 2010 (UTC)

Electron shells

If the shell theory has been discredited in favor of the cloud theory then why can you still predict the behavior and interactions of atoms and molecules with concepts such as few electrons in the outer shell makes it more likely to loose an electron? Thank you 24.92.78.167 (talk) 22:50, 18 September 2010 (UTC)

Meh, it's not about having a few electrons in a shell. It's about effective nuclear charge. Sodium doesn't hold on to its electrons very tightly because it has an ENC of about +1. Fluorine has +7, while the noble gases have about +8. Now ENC combined with how far away the valence shell is vaguely analogous to electronegativity. John Riemann Soong (talk) 23:26, 18 September 2010 (UTC)

I wouldn't say the shell model is "discredited"; it's just recognized as a fairly coarse approximation. JRS makes a good point about effective nuclear charge but, if you calculate ENC by Slater's rules (which is what most people do), you are still working in the shell model. If you want to discuss the finer points of chemical bonding, the shell model isn't good enough, but it is fine for discussing basic inorganic chemistry when you just want a simple scheme to let students arrange the various bits of information about different compounds. Physchim62 (talk) 01:47, 19 September 2010 (UTC)

Indeed, just to reemphasize the points above; don't think of the various models of the atom (the Bohr model, the shell model, the quantum model, etc.) as if the later ones disproved or discredited the earlier ones. Look at the later models as more detailed and finer, but harder to work with and conceptualize. Look at the earlier models as more approximate, but easier to work with. None of them are wrong, they just each have their particular uses. --Jayron32 03:13, 19 September 2010 (UTC)

September 19

Videogaming vs Watching TV - which is worse? any conclusive data?

I'm a gamer, my wife is a TV watcher. I hate watching TV. I consider it the same as turning your brain off. My wife hates games, considering them trivial wastes of time. I counter that a player is much more actively engaged than someone sitting on the couch staring passively at a boxy appliance. She counters that there is plenty of educational programming but few if any educational games. I counter that no one watches educational programming... What I'd like to see is a scientific analysis of the comparative "value" of playing videogames and watching TV. Which is better for the mind? Is either activity a worthy pursuit or are both equally useless, etc. Real science only please, we're perfectly able to argue opinions ourselves. Thank you. The Masked Booby (talk) 00:48, 19 September 2010 (UTC)

Does not deal with video games directly, but you would be very interested in reading the works of Marshall MacLuhan whose life works looked at the way in which various forms of media and entertainment affected people psychologically and sociologically. His book Understanding Media explores the different forms of media and attempts to divide them into "hot" and "cold" varieties based on how people interact with them. He lived and worked well before the internet and video games, but his work is still very relevent to your question. --Jayron32 03:10, 19 September 2010 (UTC)

See this http://www.bbc.co.uk/news/technology-11295257 and the linked articles at the bottom of the page. Personally I think reading non-fiction books and a quality newspaper would be better for you, as success in life or in business depends not only on intellect, but even more on knowledge. And even more on taking the initiative, risk-taking, thinking for yourself, calculating your chances. 92.15.17.68 (talk) 16:49, 19 September 2010 (UTC)

Consider what you mean by the "'value' of video games and watching TV." Neither is known for providing high educational value (and I doubt all your wife watches is educational TV, or any TV watcher for that matter). They're mostly known for entertainment value, and everyone has their own likes and dislikes on what they find entertaining. I remember a while ago there was some study (or speculation) that playing videogames might help future doctors perform remote surgery, but aside from odds and ends like this, I don't see either as being particularly enlightening for the mind.--el Aprel (^facta-_facienda) 03:43, 20 September 2010 (UTC)

Maternal death across mammal species... do the rates vary much?

I find maternal death an interesting topic, and was wondering if there are maternal death statistics available for many other mammal species? I can't remember ever hearing about a cat dying while giving birth to kittens, for example. Do the rates across mammal species fluctuate much? The Masked Booby (talk) 00:50, 19 September 2010 (UTC)

Human babies have enlarged heads. Human babies are usually grown to a quite matured phase of development. Most other mammalian animals are not born so big and so highly developed ... -- Toytoy (talk) 01:12, 19 September 2010 (UTC)

Human babies are fare *less* developed than other mammal species. Our infants are helpless, but we have a high level of parental care. Other species have babies that are much more developed. For instance, baby deer can run withing a day. Maybe Toytoy is intending to make some sort of argument based on head size of infant and pelvis size of mother, but that is not a simple matter of how `developed' the offspring is at birth. SemanticMantis (talk) 13:39, 19 September 2010 (UTC)

From what I understand, human babys are born so helpless because our species has such giant brains at birth. If the pregnancy lasted any longer babies wouldn't be able to fit through the birth canal. As it is, human babies are already born with a soft spot in their skull so that their head can compress during birth. —Arctic Gnome (talk • contribs) 18:34, 19 September 2010 (UTC)

Right, humans babies have (proportionately) much larger heads and smaller bodies than adults. This is called allometric growth, see figure 1.18 here: http://www.ncbi.nlm.nih.gov/bookshelf/br.fcgi?book=dbio&part=A79<\span>

If All Creatures Great and Small is to be believed, vets often have to intervene to turn calves and foals around in the uterus, to prevent breech births, which could otherwise kill the mother. Rojomoke (talk) 06:52, 19 September 2010 (UTC)

It seems that evolution of bipedalism may be implicated in increasing birth complications in humans. See http://johnhawks.net/weblog/topics/bipedalism/bipedal_pelvis.html You are probably correct that wild (non-domestic) mammals have lower rates of maternal death than humans. SemanticMantis (talk) 13:45, 19 September 2010 (UTC)

The making of Thai fish stomach sauce

• http://www.youtube.com/watch?v=xc3XsOBtkk0

How could they use closed small glass bottles to ferment fish intestines? Aren't they going to explode? -- Toytoy (talk) 01:10, 19 September 2010 (UTC)

They could vent them periodically. --Jayron32 03:04, 19 September 2010 (UTC)

BTW, the ancient romans used a similar condiment. See garum. That article links to other similar fermented fish sauces. --Jayron32 03:06, 19 September 2010 (UTC)

From the way the question is worded, it sounds as if yeast fermentation is assumed instead of enzymatic. Off the top of my head, I think the main gas evolved in this case would likely be hydrogen, and this would immediately oxidise to water. Such a nice anaerobic environment will also discourage oxygen loving bacteria that would spoil the sauce. Also notice: all the bottles have about a third of free space at the top and this could be to allow for a build up of any gas or a reduction in pressure due to oxidization. Anticipating the next question of ”When did she add those enzymes? I didn't see her adding anything other than salt” The woman did not have to. The Gastric chief cell start to digest the stomach post mortem. When left in situ, they start to work their way through the rest of the abdominal cavity. Some more enzymes will also come from bacteria of course. Gosh! Why do I always end up feeling so hungry when reading the Reference desk? --Aspro (talk) 11:22, 19 September 2010 (UTC)

Angular momentum of very long wavelength light

A fact I should have learned many, many years ago but didn't: All photons have the exact same spin angular momentum: $\pm \hbar$. I wish they'd just called it "angular momentum of the photon", it would have been a lot easier to keep straight than "hbar"! A great blogger tuned me in to this [31] by citing an old experiment in which circularly polarized light actually turns a target disk.

But here's the thing that gets me: Very low wavelength photons take very little energy to make... but they still have angular momentum. It seems like, in theory, you could make a sort of sub-sub-radio that beams out nearly pure angular momentum, with no energy attached, allowing a satellite to twist around any which way without annoying conservation issues. And the hapless recipient of the beam likewise would be twisted around unexpectedly.

But twisting an object around... that takes energy, doesn't it? Which means that the photons have to carry energy... don't they? It seems like something has to give. Is there an absolute lowest wavelength of light, or what? Anyway, that's my question. Wnt (talk) 04:20, 19 September 2010 (UTC)

Here is a paper that discusses parts of this question http://www.physics.princeton.edu/~mcdonald/examples/optics/atkinson_pr_47_623_35.pdf it shows that the frequency of the photon changes to account for the energy. I believe (but it's only a guess) that if you reduce the frequency so much that it's lower than the energy the momentum would impart, it would stop imparting momentum. Angular momentum is quantized, so it already "refuses" to impart angular momentum in some cases, and will only do it if it can transfer a whole amount. Very interesting question BTW! Ariel. (talk) 07:26, 19 September 2010 (UTC)

Also take a look at question #2 here: http://www.drtruth.org/paradoxes.html for an interesting twist on this question. (Yes, I know this site raises the "crank alert", but question #2 is still interesting.) Ariel. (talk) 07:35, 19 September 2010 (UTC)

For the photon climbing out of a gravity well to be brought to zero energy it must be below the event horizon of a black hole. We have no knowledge, and can have no knowledge, of the physics taking place below an event horizon so it really does not matter whether or not there is an anomoly with the left over spin: it is not an anomoly that can ever be witnessed, or even happen, in the observable universe. Back to the original question, is this not just another aspect of the phenomenon well known to radio engineers that long-waves ignore large objects like buildings? The longer the wave, the larger the object has to be before there is an interaction. SpinningSpark 10:38, 19 September 2010 (UTC)

I don't like this answer, conservation of momentum is VERY fundamental. If black holes violate that then there is very big hole in the theory. Ariel. (talk) 05:00, 20 September 2010 (UTC)

As you lower in frequency it gets harder and harder to transmit power, and reciprocally to receive power. The wavelength is bigger, and the near field is larger. (and photons bigger too) This means that even if you apply high power, little power is transmitted a long distance. Instead most of the power will return back to the transmitter twice each cycle, this will be photons coming back the other direction. Also your photons will have to be circularly polarized, which is extra difficult to do, you will need a phase shift between two linearly polarized antennas. Graeme Bartlett (talk) 12:11, 19 September 2010 (UTC)

I am considering an example of a spinning magnet next to a thick aluminium plate. The plate will start spinning as it is dragged by the magnet but it will not keep going faster and faster, instead it will gradually match the speed of the magnet, as no absorption will occur when the speed is matched. This is one way an electric motor can work. And my conclusion is that the angular momentum transferred can only get the absorber spinning up to the frequency of the photons. Since the energy of the spinning absorber is proportional to the square of the angular frequency it is in proportion of the power of the photons. Graeme Bartlett (talk) 12:25, 19 September 2010 (UTC)

It's true that there are "two photon polarization states", but that just means that you can write any polarization state as α |A〉 + β |B〉 where |α|² + |β|² = 1. This specifies a point on the Bloch sphere, where antipodal points represent left and right circular polarization, the equator between them represents linear polarizations in various directions, and intermediate points are elliptical polarizations. Another roughly equivalent way of saying the same thing is that you can transmit less than one unit of angular momentum per photon by emitting a mix of left- and right-polarized photons. So there's no minimum. There is a maximum, though: no angular momentum larger than nħ in a wave of energy E = nħω (where n is the photon count). In other words, no angular momentum larger than E/ω. This is a classically derivable limit, though I don't know exactly where it comes from. In short, quantum mechanics doesn't add anything to this question, except, as usual, some small-scale discreteness. It's still an interesting question, though, even classically, at least if this paper is to be believed. -- BenRG (talk) 19:01, 19 September 2010 (UTC)

C'mon Refdesk, this is a straightforward physics problem! Don't hide yourself behind the low probabilities of absorption/emission of low energy photons. Hint: consider a body floating in space that emits one photon. Consider how one accounts for angular momentum and energy conservation of this process in general. Count Iblis (talk) 14:46, 20 September 2010 (UTC)

I have to say, I'm still out at sea on this one. In the first part, I must have missed the part about the photon changing frequency to account for this momentum - I thought that the relationship between photon energy and frequency was very simple and proportional. I think that "Dr. Truth" knows even less about physics than I do - he doesn't think light has mass... Where black holes are concerned, they have spin, so they should conserve angular momentum somehow; if you shoot a photon straight up at an event horizon, then shouldn't any less-than-infinite acceleration fail to change its speed from c by the usual relativistic addition? So either it actually escapes or else it must take "infinite precision" to get it out?

Now the useful lead is that yes, low frequency radio waves affect only big things, and it makes sense that if a photon kicks a particle out of place somewhere on the rim of the Ringworld, the angular momentum that contributes to the macroscopic object will be much greater than if it kicked a particle out of place in a dye molecule. Or to take things to the opposite extreme, on the quantum scale the photon interacts with something and changes its orbital or spin quantum number and the angular momentum seems to just mean a transition in a molecule. What's oddest is that apparently angular momentum is conserved relative to any point anywhere. I wonder if you can reorient a satellite with a nuclear magnetic resonance machine... What I should know is that angular momentum isn't energy; it's not measured in J but in J s, suggesting that there should always be some way to use virtually no energy to change angular momentum, even if I'm not quite sure what it is.

The biggest mystery of all concerns the relationship of torque and energy - according to torque, apparently a "N m" isn't quite the same thing as a "N m". Since torque is the derivative of angular momentum, that is in "N m s", really, as is Planck's constant? But this last is very much a measure of energy times time. At the moment I don't understand from torque, for example, even why power (i.e. J/s) = torque x rotational speed... and so oddly enough it's the quantum physics that seems logical and the classical which seems mysterious and unintuitive. Wnt (talk) 18:12, 20 September 2010 (UTC)

animal maths

are humans the only living thing on earth that understands maths or do other animals do as i know allot of animals are intelligent but can they do maths. --83.71.84.246 (talk) 13:34, 19 September 2010 (UTC)

I wouldn't count on it, but there is a sub-section about animals' mathematical abilities here. Animal_cognition#Mathematics--Aspro (talk) 13:42, 19 September 2010 (UTC)

In Cormorant fishing the birds are - or so the story goes - allowed to swallow say one in ten of the fish they catch. It was said that they would refuse to dive again if they were not allowed to swallow the tenth fish due to them. Other birds I think counting, such as eggs in their nest, goes something like: one, two, lots! 92.15.17.68 (talk) 17:07, 19 September 2010 (UTC)

I am told that there was once a horse in Germany who was able to work out simple addition. Is that right ?  Jon Ascton  (talk) 18:36, 19 September 2010 (UTC)

No see Clever Hans --Digrpat (talk) 18:42, 19 September 2010 (UTC)

(ec)I googled [horse arithmetic] and a number of entries came up, including one for Clever Hans, which might be the one you're thinking about. And his Russian cousin, Sleightov Hans, was able to do card tricks. ←Baseball Bugs ^{What's up, Doc?} carrots→ 18:46, 19 September 2010 (UTC)

That's quite an interesting story. The horse was discerning "the answer", i.e. when to stop tapping his hoof, by picking up on the body language of his trainer and others who posed questions. That horse was clever. There's more to intelligence than being able to do arithmetic. In general, animals don't have much need to do arithmetic, as very few of them are planning careers in the engineering field. But understanding body language is very important to any animal's survival. It's interesting that the scientists needed to analyze the situation to figure out that body language was tipping off the horse. For the horse, studying body language just came naturally. So who was the more "clever" species of the two? ←Baseball Bugs ^{What's up, Doc?} carrots→ 19:03, 19 September 2010 (UTC)

In The Mathematical Brain Brian Butterworth analyses various instances of apparent "counting" in anaimals, and reaches the conclusion that many animals in the wild demonstrate "numerosity" - a sense of number that allows then to compare the relative sizes of two groups of objects. He also discusses research that shows that chimpanzees in captivity can be taught/trained to correctly match Arabic numerals with groups of objects up to about 4, and to perform simple arithmetic with small numbers at about the level of a 3-year old human child. Gandalf61 (talk) 20:09, 19 September 2010 (UTC)

What this all speaks to is the needs of various species, which go hand-in-hand with their evolutionary development. Humans are not as good with body language as other animals are, but we're "good enough to get by", because it's a less critical need for us than it is for animals. The same could be said for factors such as sense of sight, smell, etc., which are much more acutely developed in certain species, due to evolutionary pressure or whatever. Humans also use that "numerosity". If you go to an event, you don't have to know precisely how many people are there in order to get a sense of how big the crowd is. What I wonder about training chimps in arithmetic, is what would they do with that info? Is it of real use to them, as it is for humans; or might they see it as just a game they're playing with their keepers? ←Baseball Bugs ^{What's up, Doc?} carrots→ 20:30, 19 September 2010 (UTC)

I used to hike with what I thought was a fairly smart dog. A regular route involved crossing a river that I could wade across but he had to swim. He eventually developed the habit of leaping in, finding he was being swept downstream, climbing back out and walking upstream a varying distance that always seemed to get him to the right spot directly across on the opposite bank, based on how much he got swept downstream by the the current. Did he understand vectors? HiLo48 (talk) 01:06, 20 September 2010 (UTC)

He certainly understood the concept even if he didn't know what to call it. So, was your dog named Victor? :) ←Baseball Bugs ^{What's up, Doc?} carrots→ 01:16, 20 September 2010 (UTC)

HiLo makes a good point with his vector-dog. Math is much more than just numbers. Some see math as the (formal) study of patterns, structures, etc. In that light, many species (dolphins, chimps, New Caledonian crows) could be said to have some understanding of math, but probably not in any formal terms.SemanticMantis (talk) 02:32, 20 September 2010 (UTC)

science

where is the silicon controlled rectifier is demonstrated and is its first application? —Preceding unsigned comment added by Thethesarfraj (talk • contribs) 15:00, 19 September 2010 (UTC)

Does the silicon-controlled rectifier article not have the answers to your question? SpinningSpark 16:07, 19 September 2010 (UTC)

Elasticity

Who discovered the phenomenon of elasticity? —Preceding unsigned comment added by Blaze250 (talk • contribs) 15:58, 19 September 2010 (UTC)

I don't know that it was discovered as such, it has always been around, like hardness and wetness. But you are probably looking for Robert Hooke and his law of elasticity, Hooke's law. SpinningSpark 16:11, 19 September 2010 (UTC)

Ancient humans used to kill animals for food. It was probably while exploring carcasses that they discovered elasticity (intestines etc ). They used them to make bows.  Jon Ascton  (talk) 18:47, 19 September 2010 (UTC)

Your last point is incorrect, Jon: bowstrings are made of materials like Dacron which have a minuscule amount of elasticity. The power is stored in the limbs, so you want a string that will not stretch when under the 300 N or so of force at full draw. Please don't answer questions with unsupported speculation. Brammers (talk/c) 21:53, 19 September 2010 (UTC)

Cavemen had Dacron? :) ←Baseball Bugs ^{What's up, Doc?} carrots→ 23:37, 19 September 2010 (UTC)

Only the ones with facilities to order it over the internet. SpinningSpark 00:38, 20 September 2010 (UTC)

To be fair, he didn't say they made bowstrings, he said they made bows - see Mongol bow. Matt Deres (talk) 14:29, 20 September 2010 (UTC)

According to Bow_string, the amount of stretch in bow strings varies. Strings with more stretch transmit less shock to the bow limbs but are less powerful. It is true that the power of the bow is in the limbs, not the string for the most part. Exxolon (talk) 01:44, 20 September 2010 (UTC)

Metal compared to ice

Ice is frozen water. Metal could be considered 'frozen' liquid-metal. Do ice and metal have a similar structure, despite being composed of different atoms? 92.15.12.54 (talk) 23:38, 19 September 2010 (UTC)

The bonding between metal atoms (see Metallic bond) and water molecules (Hydrogen bonds) are somewhat different, and the Crystal structures are also somewhat different (in general). Ice, in particular Ice Ih (which is what "normal" ice is) has a Hexagonal crystal system (and a sort of odd one at that, with a large amount of empty space). Metals have lots of different types of crystal structures, so it's hard to make generalizations. Many (most?) metals have some sort of Cubic crystal system, with generally less empty space. Some metals (Yttrium, Titanium, and Scandium, for example) do have hexagonal structures like water (though generally without the empty space like water). Buddy431 (talk) 00:15, 20 September 2010 (UTC)

I was wondering something similar: is Ice Ic equivalent in structure to lithium oxide? Wnt (talk) 00:20, 20 September 2010 (UTC)

No, not at all. In lithium oxide, the lithium ions and the oxide ions are basically charged spheres, and they "bond" by electrostatic attraction. The "bonding" is not in any given direction, but the spheres are different in size (oxide being much larger than lithium). The structure comes down to how those spheres can pack together as closely as possible – a mathematical problem – and the various solutions are taught in basic chemistry courses. In water, and ice Ic, the bonds are directional: in other words, you can represent them with lines to show where there is a bond and where there isn't one. So the hydrogen atoms are not free to go wherever they like or wherever they would fit best, they have to stay at a certain distance from the oxygens and with a certain bond angle between them. This is why ice has so much more free space than a metal or than an ionic solid like lithium oxide. Physchim62 (talk) 00:38, 20 September 2010 (UTC)

Ooops, looks like I was off base on this one - it's not even the same kind of cubic structure. Wnt (talk) 03:56, 20 September 2010 (UTC)

As an aside, the OP might find the Pykrete article interesting. Exxolon (talk) 01:41, 20 September 2010 (UTC)

Under extreme pressures water ice turns into a metal conducting electricity. Graeme Bartlett (talk) 01:55, 20 September 2010 (UTC)

Really? What exactly do you mean it turns into a metal? The atoms of hydrogen and oxygen are still hydrogen and oxygen, and they are listed in the Periodic table as being non-metals. Do you mean it behaves as a metal? — Sam 18:20, 20 September 2010 (UTC)

September 20

Update to Aug 22, 2010 question by me re "Instructions for Filtering Water in Urdu Language"

This post was a notification that a question had been resolved. Moved to the original archived thread SpinningSpark 07:54, 20 September 2010 (UTC)

Uses of natural rubber

Dear friends, I'd like to know that which type of natural rubber use for tires and tubes?

amin —Preceding unsigned comment added by 80.191.71.237 (talk) 07:53, 20 September 2010 (UTC)

The Pará rubber tree (Hevea brasiliensis), is the cheapest and primary source of natural rubber and so it would be this one. --Aspro (talk) 08:02, 20 September 2010 (UTC)

What is the proper English name of this lamp?

whatsitsname

What is the name of this lamp? I've tried to check around Gas-discharge lamp and List of light sources, but didn't see something quite like that. It may be a diode after all, but it's main function is (obviously) generating light.

The piece on the picture was built in Hungary in the 70's (by Tungsram) and have completely disappeared from the market after the regime shift of '89. (And just hung up the sales guy at GE Lighting who said that the probability of it ever manufactured again is zero since all the misc parts [glass, metal parts] will be discontinued due to new EU regulations over tungsten lamps. Sad.) I have been told that similar items (figure lamps) are still on sale in Russia, Bulgaria and such but since I am not able to figure out the name I cannot really search for it. The dictionary suggested "glow lamp" which seems not to be the particular phrase to convey the meaning... :-( Ideas, or maybe for-sale items (in private email)? Thank you. --grin ✎ 08:41, 20 September 2010 (UTC)

Novelty neon lamp, similar to the flame flicker bulbs. Other designs are still obtainable. tritek taiwan corporation --Aspro (talk) 09:08, 20 September 2010 (UTC)

I Agree with Aspro. To quote wikihow: "Flicker Flame" light bulb is a form of specialty lighting which produces a candle-like "flame" effect. The bulbs use two metal plates in an evacuated bulb, filled with the rare-earth gas neon, to create a dancing orange glow. Although these bulbs are appreciated by many lighting enthusiasts, they can be difficult to find. EverGreg (talk) 13:37, 20 September 2010 (UTC)

Transmembrane protein

Why do you we find alpha helix str. in transmembrane region of membrane protein? —Preceding unsigned comment added by 123.252.174.26 (talk) 09:40, 20 September 2010 (UTC)

The alpha helix structure is stable within phospholipid membranes, so transmembrane proteins can remain transmembrane proteins (and not fall out of the membrane). Our article on transmembrane domains provides some more information. Cheers, Mattopaedia ^{Say G'Day!} 10:43, 20 September 2010 (UTC)

absorbers

can i know names of absorbers that can absorb carbon mono oxide —Preceding unsigned comment added by Harikishanchem (talk • contribs) 09:43, 20 September 2010 (UTC)

Do you mean absorbers that actually remove the carbon monoxide from the air so it won't poison anybody? --Chemicalinterest (talk) 10:57, 20 September 2010 (UTC)

Hopcalite is used in rescue equipment where carbon monoxide is a risk. Wikipedia -as always- has an article on it. It is a convesion into CO2 however. --Aspro (talk) 11:16, 20 September 2010 (UTC)

By absorber...you mean a scrubber or air purifier right?Smallman12q (talk) 11:53, 20 September 2010 (UTC)

The hopcalite is a catalyst that makes carbon monoxide react with oxygen to make carbon dioxide. Normally this happens very slowly, unless the CO is ignited. --Chemicalinterest (talk) 15:13, 20 September 2010 (UTC)

Massive dose of radiation

What can be seen immediately after someone receives a massive dose of radiation? --Chemicalinterest (talk) 14:53, 20 September 2010 (UTC)

A large puff of smoke! Can you be a little more precise.--Aspro (talk) 15:04, 20 September 2010 (UTC)

Our article on radiation poisoning has a reference table of the symptoms of various levels of radiation exposure. For whole-body exposure of 30 gray or higher, it lists nausea, vomiting, diarrhea, headache, fever, seizures, tremor and ataxia, followed by death. Gandalf61 (talk) 15:10, 20 September 2010 (UTC)

(edit conflict)Smoke??? A radiation dose of 50 grays, for example. Could someone tell just by looking at the person that they have just received the dose of radiation? (No infrared radiation is present.) --Chemicalinterest (talk) 15:11, 20 September 2010 (UTC)

The article states what happens after half an hour or so. What can be seen immediately, if anything can be seen? --Chemicalinterest (talk) 15:11, 20 September 2010 (UTC)

Radiation burns develop pretty quickly, depending on the type of radiation. Physchim62 (talk) 15:46, 20 September 2010 (UTC)

(ec) At most a radiation burn if the source was intense and close. --Mr.98 (talk) 15:47, 20 September 2010 (UTC)

Radiation_poisoning#Exposure_levels lists that for massive doses, vomiting begins immediately so that would be the first symptom/visual sign? Exxolon (talk) 15:53, 20 September 2010 (UTC)

The article says that nausea and vomiting occur immediately with high levels of exposure. The extent of visible radiation burns, if any, will depend on the type of radiation - beta radiation is heavily absorbed by the skin and causes visible burns; gamma radiation and X-rays are absorbed throughout the body and may not cause immediately visible burns. Anyone with 50 grays of whole-body exposure is not going to be walking around for more than a few minutes. Gandalf61 (talk) 15:57, 20 September 2010 (UTC)

Aspects of scientific studies

One illustration in a reading I'm doing for school is a story of scientists studying cognitive energy in a group of students based on food: they make students memorise numbers of different sizes and allow them to choose between two different types of dessert afterward. The scientists observe that the students who must memorise larger numbers tend to choose chocolate cake, while the students who have smaller numbers tend to choose fruit salad; from this, the scientists conclude that memorising larger numbers takes up enough brain resources that students have a hard time choosing the healthier dessert. Now for my question — do studies such as this take into account the subjects' likes and dislikes for certain types of food? If I were one of these individuals, regardless of how large of a number I would have to memorise, I'd go for the fruit because I don't like chocolate, and I suppose that there are individuals who will go for chocolate because they think they're too skinny and need to gain weight. Two final things — I'm a library science student, not a psychology student; this isn't at all a request for help with homework. Secondly, the story is on pages 9 and 10 of this document. Nyttend (talk) 15:44, 20 September 2010 (UTC)

Done properly, this sort of research would take that into account. I don't have time to read the paper you linked, but the normal way of doing this sort of thing is to make sure that your test groups are large enough that these sorts of personal preferences average out. Additionally, the groups might not be split up randomly. Sometimes they intentionally split them up evenly. (ie: They might have done a survey ahead of time, found that they had eight people who professed a strong love for healthy deserts, and made sure that four of them wound up in each group.)APL (talk) 15:51, 20 September 2010 (UTC)

The article Randomized controlled trial is a bit heavy, but it discusses the subject better than I just did. The article mostly talks about medical trials, but they don't have to be medical. I this case the 'intervention' isn't some experimental drug, it's just being forced to memorize large numbers. APL (talk) 15:56, 20 September 2010 (UTC)

And it's probably healthy to be a little dubious of the kind of conclusion made. To me it seems to be a big jump between "we noticed a small but statistically significant correlation between choosing the cake and memorizing the larger numbers" to "well this must have to do with 'brain resources' and metabolization of energy." I mean one can come up with all sorts of alternative interpretations even if one accepts their data is good and the experiment itself was done well. (Chocolate, for example, is not exactly a pharmacologically neutral substance. We might be learning more about the cognitive effects of chocolate here than the amount of energy needed for memorization.) --Mr.98 (talk) 15:57, 20 September 2010 (UTC)

(edit conflict)Psychology#Controlled experiments has :"A true experiment with random allocation of subjects to conditions allows researchers to infer causal relationships between different aspects of behavior and the environment." (Causal seems a bit strong, but okay because ideally it does allow that). Presumably, the students were randomly assigned into the two groups such that it could be statistically safe to say that there was no a priori difference between one group's average food preference and the other's. If the experiment was done right, in other words, the only difference between the two groups before they were offered a choice was that one group memorized a 7-digit number and the other a 2-digit number, in which case, yes, it accounted for that. (I'm surprised that there was enough difference in "cognitive effort" between these two tasks to account for such a measurable result -- it sounds like it may have been poorly designed, I wonder if any other studies have replicated support it. See also The Magical Number Seven, Plus or Minus Two for a sense of the "cognitive effort" involved here.) WikiDao ☯ (talk) 16:05, 20 September 2010 (UTC)

People who have had to work hard feel sorry for themselves and decide that they "deserve" to eat chocolate. It's well known that people treat food as a reward and a comfort. That's just one alternative explanation for the effect. Itsmejudith (talk) 16:31, 20 September 2010 (UTC)

(Note) In case anyone has library access to the study quoted in Nyttend's link, it is: "Heart and Mind in Conflict: The Interplay of Affect and Cognition in Consumer Decision Making'" (Baba Shiv, Alexander Fedorokhin, Journal of Consumer Research, University of Chicago Press, vol. 26(3), pages 278-92, December, 1999). link to JSTOR with abstract. I can't access the study directly, but this link suggests that 63% of the 7-digit memorizers chose chocolate cake, as opposed to only 41% of the 2-digit memorizers. ---Sluzzelin talk 16:40, 20 September 2010 (UTC)

Judging from the first page of the article and abstract, it doesn't seem like it is making an argument about brain energy at all, but a more complicated one about consumer choice. --Mr.98 (talk) 16:51, 20 September 2010 (UTC)