Wikipedia:Reference desk/Archives/Science/2008 August 2

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August 2

Body part focus of cell phone health studies

Most studies I have heard about on cell phones and health focus on brain diseases. But most people I know carry their cell phone in a trousers pocket or a purse or have it hanging on the belt most of the day; people don't put their cell phone next to their head unless they're talking on it, and most people spend more time during the day carrying a cell phone then actually talking on it. So shouldn't the torso, waist, and pelvis be more affected than the head by the radiation? If so, why are the studies focusing on the head and brain; isn't their focus misplaced? —Lowellian (reply) 00:00, 2 August 2008 (UTC)

Cell phones are usually not transmitting, especially not when they are in your pocket and "inactive" - the device may be on, but the transmit radio is almost entirely off. (They may periodically send a short pulse to the local cell tower to retain link connection). However, during conversation, the mobile device is actively transmitting (at "maximum power"). This necessarily increases the exposure to electromagnetic radiation while a telephone call is active. The assumption is that the cell phone is held near the head (ear) during conversation, thus, during peak radiation levels, so this is the time period of interest to many scientists. Nimur (talk) 00:13, 2 August 2008 (UTC)

Addendum: As we get more "internet"-ish cell phones, which use persistent data connections, the connectivity model I just described may become less accurate as a descriptor of the cell phone transmitter/radio usage; however, the historical technology trend has been a move towards lower-power radio signals with more sophisticated digital modulation to preserve signal integrity. This will almost certainly be true of any persistent data connections; if for no other reason, it's usually better for battery life, since even complex digital circuits use less power than a nasty high-power narrow-band transmitter. Nimur (talk) 00:22, 2 August 2008 (UTC)

Considering how many people keep their cell phones in their pockets or otherwise attached to the waistband of their pants/shorts while talking using hands-free sets though, studies on other parts of the body besides the head would still seem useful. —Lowellian (reply) 00:33, 2 August 2008 (UTC)

Also, you wrote "This necessarily increases the exposure to electromagnetic radiation while a telephone call is active." Another question: how much of an increase? Two-to-one? Ten-to-one? A hundred-to-one? —Lowellian (reply) 00:38, 2 August 2008 (UTC)

Well, if the transmitter is off, it generates 0 (zero) watts, and if it is on, it generates about 1 (one) watt. You could look at a specific chip used on a specific telephone to determine more precise values. Even when "off", it seems plausible that a minute amount of leakage may occur, but I'd guess this is on the order of tens or hundreds of decibels below the active transmit level. (If you aren't familiar with decibel scales, that would be a factor of hundreds of times more power). Nimur (talk) 17:13, 3 August 2008 (UTC)

Keep in mind, that while EM radiation is indeed "radiation", it is not ionizing radiation. It is not the same kind of "radiation" that one means when talking about nuclear weapons or reactors or things like that. Whether there are long-term health effects that can be traced to it or not (I suspect not, other than distraction-related injuries), one should be aware that the terminology can get slippery if one is not careful. --98.217.8.46 (talk) 00:23, 2 August 2008 (UTC)

Ionizing radiation and radiation may help clarify. Of course, though ionizing radiation is generally considered worse, it is not valid to use this classification as the sole distinction between dangerous and not-dangerous. Nimur (talk) 00:25, 2 August 2008 (UTC)

I wasn't implying that it was. But "radiation" in the common parlance is something very different than the "radiation" in cell phones, or light bulbs, for that matter. It's entirely true that light bulbs output LOTS OF RADIATION!!! but that doesn't really mean "radiation" in the sense that most people know it. When most people think of "radiation", they mean ionizing radiation—they are thinking about genetic damage, cell damage, etc., not the sorts of things one gets at the microwave level, e.g. heating. --98.217.8.46 (talk) 00:27, 2 August 2008 (UTC)

Research has been done in mammals and through observational methods in humans, see this and all of it's linked papers and this study on mammals. Nanonic (talk) 00:25, 2 August 2008 (UTC)

Also, how much radiation are wireless cards generating in comparison to cellphones? —Lowellian (reply) 00:34, 2 August 2008 (UTC)

Cellphone: 2 W

WiFi card: 0.1 W

These are the regulatory limits [1], but the devices don't operate flat-out all the time. --Heron (talk) 14:11, 2 August 2008 (UTC)

A Cell phone transmits at "maximum power" only when the cell signal is weak. The cell tower interacts with the cell phone to restrict the power what is actually needed. Thus, you are exposed to more power when you are in a weak signal area. this is why your battery runs down faster when you are in a weak signal area.If you are worried about radiation from your cell phone and it your hours or office gets a weak signal, you might want to install a femtocell. -Arch dude (talk) 16:20, 2 August 2008 (UTC)

Won't that replace the radiation from your cell phone with radiation from a base-unit? It may even increase your exposure levels. Nimur (talk) 17:15, 3 August 2008 (UTC)

That depends how close you are to the femtocell is guess. Remember the primary issue is that people tend to have phones very close to their heads/brains. While a femtocell obviously transmits with greater power, unless you are within say a metre of one (random guess) you're probably going to receive less EM radiation. Nil Einne (talk) 19:35, 6 August 2008 (UTC)

Predatory Dinos

I remember reading a book on predatory dinosaurs a long time ago, which wass mainly about theropods, but had some passing references to 2 other types of carnivorous dinos, herreravians, which I don't know how to spell, and another which I forget. Google turns up nothing. they might have undergone a name change. Does anyone have an info on these "herreravians"? Sliver Slave (talk) 02:13, 2 August 2008 (UTC)

Herrerasauridae ? They are technically theropods AFAIR. --Dr Dima (talk) 03:09, 2 August 2008 (UTC)

Predatory Dinosaurs of the World by Gregory S. Paul is the book you're thinking of. Paul invented his own classification scheme which is a bit outdated and was not widely accepted by others. Herreravia was one group that lumped together primitive types like Herrerasauridae, as Dr Dima guessed. The 'avia' part may have come from his including Protoavis as a herrerasaur--he thought they were highly convergant with birds because of this, seperate from his "Protoavia" (roughly the modern Maniraptora minus birds). I do recall he had another, even more primitive group than Herreravia (I don't have the book with me here so I can't check on the name and exact content). IIRC, it contained mainly Lagosuchians and relatives, now considered an assemblage of ancestral dinosauromorphs and not true dinosaurs (I think Bakker in Dinosaur Heresies also included lagosuchians as dinosaurs. Under modern cladistic methods, they fall outside this group because they did not descend from the common ancestor of Megalosaurus and Iguanodon--that is, they're neither Saurichians nor Ornithischians and therefore aren't true dinosaurs). Hope this helps! Dinoguy2 (talk) 00:30, 4 August 2008 (UTC)

Allylic halides and nucleophilic substitutions

How do you know when an allylic halide would rather undergo S_N1 rather than S_N2? Is there some sort of rule? I ask because my organic chemistry textbook just says that allylic halides can undergo both but doesn't mention specific conditions for either. On top of that, one of the exercises just claims "S_N2 conditions!" with no explanation of why it's S_N2-favoring conditions. --M1ss1ontomars2k4 (talk) 03:35, 2 August 2008 (UTC)

There may be something specific to sp²-hybridized carbons (in which I'd be quite interested), but ignoring that, I think the conditions favoring S_N1 or S_N2 mechanisms are the same as for sp³-hybridized carbons: Polar solvents, more-substituted carbons, and stearically hindered attack angles (opposite the leaving group) favor S_N1, the opposite conditions favor S_N2. —Keenan Pepper 04:47, 2 August 2008 (UTC)

See Neighbouring group participation which speeds up both SN1 and SN2 reactions (quite a lot)87.102.86.73 (talk)

Thanks! I actually found it in my notes already. I never remember a thing about my notes once I've taken them; it turns out that nonpolar solvents tend to favor S_N1, whereas polar aprotic solvents encourage S_N2. --M1ss1ontomars2k4 (talk) 04:54, 2 August 2008 (UTC)

I think it's the other way round - polar solvents should favour SN1 !87.102.86.73 (talk) 12:38, 2 August 2008 (UTC)

Yes there is something special about allylic halides assuming you mean XCH₂-CH=CH₂ etc (and not CH₂-CH=CHX which are vinylic haldide technically)

SN1 is favoured compared to a normal alkylic halide due to stabilisation of the carbon cation CH₂⁺-CH=CH₂ by resonance

eg CH₂⁺-CH=CH₂ and CH₂=CH-CH₂⁺

Additionally SN2 can occur at the gamma carbon too eg

XCRH-CH=CH₂ + Y^- >>> CRH=CH-CH₂Y + X^-

Watch out for the above reaction when the question says SN2 conditions. —Preceding unsigned comment added by 87.102.86.73 (talk) 12:36, 2 August 2008 (UTC)

Actually Neighbouring group participation points out that allyl groups have faster SN2 reactions as well...87.102.86.73 (talk) 13:40, 2 August 2008 (UTC)

Can you explain this 'major discovery'?

What was the novelty the MIT team in fact discovered in this press release? [2]. When electricity -- whether from a photovoltaic cell, a wind turbine or any other source -- runs through the electrode, the cobalt and phosphate form a thin film on the electrode, and oxygen gas is produced. Well, I thought the production of oxygen and hydrogen from water would happen with any electrode, just using the electricity.

So, they convert surplus electricity to H2/O2 for storage. Where is the deal? --Ayacop (talk) 07:05, 2 August 2008 (UTC)

See User talk:SteveBaker#Interesting? for discussions made by one of the greatest (ex-)RD contributors on this topic. --antilived^{T | C | G} 07:44, 2 August 2008 (UTC)

Thanks. To summarize, splitting water with normal electrodes isn't 100 percent efficient (probably producing too much heat), so that can still be optimized which they apparently did. I hope the PR writer will never edit Wikipedia. --Ayacop (talk) 07:52, 2 August 2008 (UTC)

Confirmed. As I understand it, using two platinum electrodes is about 60% to 70% efficient [3], with the rest lost as heat. Nearly all of the loss is at the anode where O2 is made [4]. Nocera's catalyst fixes the anode problem, increasing the overall efficiency to "near 100%" (can't find the exact figure), but still requires a platinum cathode to make the H2. The next step is to find a cheap cathode material. --Heron (talk) 13:59, 2 August 2008 (UTC)

Life time of hydrogen economy

A question that bothers me for a good time, already: How long can a hydrogen economy survive, given nonzero leaking of hydrogen into the atmosphere plus nonzero leaking of hydrogen from atmosphere into space? What's the order of magnitude of lifetime if you assume 5% leakage on earth, and the normal rate into space? --Ayacop (talk) 08:03, 2 August 2008 (UTC)

I assume by hydrogen economy you mean using hydrogen as main carrier of energy. But where would that hydrogen come from in first place? From water, consuming lots of energy, leaving O2, or from hydrogen carbons, consuming lots of energy, leaving, perhaps graphite or soot? I admit I never understood the benefits. As for the leakage, I guess H2 would be oxidized pretty fast and the leakage into space would be quite that from natural water vapor. 93.132.136.138 (talk) 11:29, 2 August 2008 (UTC)

As far as I'm aware, most proposals for a hydrogen economy have it coming from seawater since we have it in abudance. 5% leakage seems rather high to me but even so, I expect it would last several million years or more. I don't think anyone seriously thinks were going to run out of seawater. The main problem is finding a way to produce the energy needed to produce said hydrogen. Nil Einne (talk) 12:31, 2 August 2008 (UTC)

A quick calculation shows that, at current world energy consumption levels, even if we assume that all the hydrogen we burn immediately vanishes into space by magic, we still have 30 million years or so before we run out. We are not going to run out of ocean any time soon. Algebraist 12:50, 2 August 2008 (UTC)

The article hydrogen economy states. "As an energy carrier, hydrogen could substitute for dwindling supplies of petroleum and provide energy independence to countries without oil resources."

How could that be? 93.132.136.138 (talk) 13:12, 2 August 2008 (UTC)

I think the principle is Nuclear+Wind+Hydro etc >>> Energy and then Energy+Water >>> Hydrogen

Thus avoiding any petroleum in the chain.

However I can't imagine Hydrogen power ships/planes/trains anytime soon - so I think the emphasis is on could87.102.86.73 (talk) 13:37, 2 August 2008 (UTC)

So the energy independence really comes from "Nuclear+Wind+Hydro etc". Why is the article falsely implying hydrogen alone could lead to energy independence? 93.132.136.138 (talk) 13:55, 2 August 2008 (UTC)

It's slightly misleading perhaps "As an energy carrier, hydrogen could substitute for dwindling supplies of petroleum and provide energy independence to countries without oil resources when coupled with alternative energy sources"

Is that better - make the change yourself if you wish.87.102.86.73 (talk) 14:12, 2 August 2008 (UTC)

It would still be subtly but massively misleading. Energy independence does not depend on the energy carrier but on the energy resources. For renewable energies, this is mostly land, and not an alternative (though a valuable supplement) for highly populated countries. 93.132.136.138 (talk) 14:49, 2 August 2008 (UTC)

In the current world, you need both an energy carrier and energy resources. While trains in particular can use electricity most other forms of transport including air, sea and trucks+cars and a lot of other stuff (e.g. farm machinery) can't for long distance at least given the current state of battery technology (fuel cells may change this although I suspect it will be a long, long time before we're using electric planes). Also I don't think it purely depends on land. A desert country for example can get a lot more out of solar then say, Scotland. Some countries have good access to geothermal, others don't. Inland countries have no access to tidal power. Wind is better in some countries then others. Hydro depends on rainfall, rivers etc. And some countries have a lot of uranium, others not much. Tropical countries can potentially produce an equivalent amount of biofuels with less land usage then temperate countries (although again this varies a lot from location to location) although of course if you are producing biofuels you may not need hydrogen as an energy carrier. Fresh water may be a limiting resource for biofuel production in some cases Nil Einne (talk) 16:46, 2 August 2008 (UTC)

I tweaked the article in an attempt to make it less ambiguous. --Heron (talk) 14:44, 2 August 2008 (UTC)

Note that hydrogen could potentially be used for energy storage as well as an energy carrier. Energy storage is particularly vital for renewable sources which (barring hydrogen and perhaps geothermal to some extent) tend to be unreliable and also can't respond to demand & may also be useful for nuclear which can only respond very slowly to demand. Currently the only energy storage I'm aware of suitable for power stations is pumped hydro. (Non-pumped hydro can of course also respond on demand and can be used to supplement other renewable sources and nuclear but isn't an energy storage system.) Energy storage may also be deemed necessary for security reasons (e.g. if a big chunk of your power is coming from solar and your solar power stations are mostly in one area that may be deemed a big security risk.) Hydrogen could also potentially be used as an energy carrier over long distance where simply high tension wires are not deemed feasible e.g. desert countries could produce hydrogen via solar power and sell it to countries with less available solar power (obviously this doesn't help energy independence), some ideas appear to be here [5]. Of course all these are simply possibilities what actually happens is anyone's guess (I personally believe the hydrogen economy idea is overated) Nil Einne (talk) 16:59, 2 August 2008 (UTC)

Pumped air and NaS batteries have also been demonstrated for energy storage at the power station scale. Dragons flight (talk) 16:52, 2 August 2008 (UTC)

Zenker's Diverticulum is well know among Gastroenterologists, who was Zenker and where did he publish his new disorder?

As a retired medico, I have encountered patients with Zenker's Diverticulum. Most embarrassing when I had to admit to one of them that I didn't know who Zenker was. That was before Wikipedia, of course! —Preceding unsigned comment added by 77.127.125.172 (talk) 12:12, 2 August 2008 (UTC)

Um now that this is after Wikipedia, did you try looking at Zenker's Diverticulum? Seems the obvious place to look... Nil Einne (talk) 12:25, 2 August 2008 (UTC)

Applied maths

Which type of engineering uses the most maths and which uses the least? I would also liek to ask the same question for physics. Clover345 (talk) 17:54, 2 August 2008 (UTC)

How do you measure maths and physics? Without knowing that, there's no way of telling who uses most. 93.132.136.138 (talk) 19:18, 2 August 2008 (UTC)

As a gross generalization someone majoring in biophysics will have probably have taken fewer math courses than someone majoring in theoretical particle physics for example. Physics pretty much entails doing math, though the complexity of the math varies from problem to problem and depends on how difficult you want to make it and what sort of answer you are looking for. If this question relates to picking a major, it is probably best to look at the major requirements are at whatever institution is relevent. If you are asking which type of physics or engineering is the "harder science" (vs. the "softer science"), I don't think you can get an answer everyone will agree on. —Preceding unsigned comment added by 71.16.107.2 (talk) 19:58, 2 August 2008 (UTC)

Probably the heaviest use of mathematics in physics is in particle physics, especially string theory (a lot of which is indistinguishable from pure mathematics). In engineering I have no idea—aerospace? The least mathematical is harder to judge because of the fuzzy boundaries of both subjects. Building Lego structures could count as engineering and juggling could count as physics. -- BenRG (talk) 20:00, 2 August 2008 (UTC)

I think this question can be answered, although I can't answer it myself. The engineering disciplines differ in how much they rely on experience and professional intuition, rather than using theory and math in practice. My gut feeling is that electrical engineers are relatively reliant on the math and civil engineers are relatively reliant in experience and intuition. I'd love to hear from others on this. ike9898 (talk) 17:18, 3 August 2008 (UTC)

Each discipline uses different styles of analysis (and accordingly, they use different types of mathematics). Electrical engineers use transform theory and complex analysis. Mechanical and structural engineers use partial differential equations. Environmental engineers use statistics and stoichiometry. Computer engineers use number theory and generalized algebra representations. You could survey a lot of engineers and ask them how often they "do math", but you are going to have to be pretty specific - do you mean number-crunching, or analysis, or theory? Nimur (talk) 17:24, 3 August 2008 (UTC)

Why didn't man evolve wings?

I thought that every life form evolved based on need. Don't get me wrong, I believe in evolution , but it seems odd that such a useful trait wasn't given to us. Instead it was given to birds, and insects (As if they need it. There's too damn many of em, already!)

But seriously, imagine how useful it would be.- Gas crisis? Solved! Road congestion? Solved! Elevator repairmen? Sadly, unemployed. Oh well, there's always a trade off. Hey, I'm Just Curious (talk) 18:18, 2 August 2008 (UTC)

Evolution doesn't work based on "need" in the sense that it can make major changes to body plans based on what might eventually be helpful. To slightly modify an example of yours, if the gas crisis is going to affect human evolution, it would favor those who can run with speed and stamina approaching that of the cars we can no longer use, not cause people to start growing wings. Even if some amazing mutation caused us to develop angel-type wings(that is, a new pair of limbs) and hollow bones, it'd probably be debilitating to the rest of the body, and therefore not very helpful(you might be interested in the story "The Fliers of Gy" by Ursula Le Guin, which is about humanoid aliens who occasionally have a wing-sprouting mutation, which they consider a deformity). 207.233.84.97 (talk) 19:37, 5 August 2008 (UTC)

If "that would be handy" was the only factor in the natural selection of animals, birds would long ago have evolved into F-15 Strike Eagles. There are costs as well: flying needs one to be light (which generally means small, with thin honeycombed bones) and strong (a winged human would have impossibly massive chest and back muscles), and (for larger animals at least) flight is very expensive (energy wise). Animals all live in a complex multivariate world - you have to survive drought and famine and flood and you have to exploit times of plenty when they come, and you have to find a niche in life that isn't occupied by something that's better at living there than you are, and doesn't make you lunch for too many other things. And (returning to the lighter-hearted tone of your question) wings are for chickens. -- Finlay McWalter | Talk 18:34, 2 August 2008 (UTC)

(EC) If you're talking about traits being 'given', you don't understand evolution. If you think life forms evolve base on 'need' you also don't understand evolution. I don't say this to put this down, simply suggest that you may want to read our articles, e.g. Introduction to evolution, Evolution & Modern evolutionary synthesis since it will help you answer this question for yourself and a lot more besides like asking 'why' something didn't evolve is pretty pointless. But to put it simply, evolution doesn't happen based on need. 'Nature' doesn't choose what traits would be best for an organism and add them because it 'know's' the organism 'needs' them (that's a design view not evolution). Instead, random/spontaenous mutations give rise to different traits. If a trait is advantageous in a organism population's current niche, then it is likely this trait will become more common in that population over time (see Adaptation). There is no guarantee a trait is going to arise, and even if it does, there is no guarantee it will be fixed in the population even if it's advantageous. Also, flight requires a lot of tradeoffs (e.g. light body) and it's unlikely to be advantageous for humans to have natural flight in any case IMHO. (Not that this matters since as I've said, traits aren't selected in any way). And BTW, flight is itself a very complicated trait and only arose after a lot of mutations and their corresponding different traits lead there. Since as I've said, there is no overall purpose (i.e. there was no consideration, we need flight and we need to do this to get there), understanding how & why flight evolved in any given organism that has flight is not so simple as it may seem. (Although it's worth understanding not every single step happened because it was advantageous, see genetic drift and that we can never know for sure why something evolved, we can only speculate on possibilities.) This is a greatly simplified view of evolution and not entirely accurate so I suggest you read the linked articles if you want to learn more. Nil Einne (talk) 19:00, 2 August 2008 (UTC)

If you read Last and First Men you'll see that we will eventually have wings, we just haven't got there yet. Dmcq (talk) 19:45, 2 August 2008 (UTC)

If we had wings we wouldn't have arms. If we had wings we'd be birds, and we'd be wondering why we don't have arms, as we have to use our beaks and feet for everything. --M1ss1ontomars2k4 (talk) 19:51, 2 August 2008 (UTC)

Those before me have posted useful links, another would be Common_misconceptions#Evolution. --Mark PEA (talk) 21:50, 2 August 2008 (UTC)

I may be wrong, but didn't Leonardo da Vinci come up with a few sketches of what an angel would look like if it had wings? I seem to recall the rib cage and muscular structure would have to be grotesque in their enormity, and you would have to spend every waking hour consuming food to generate the energy to beat them for sustained flight. --russ (talk) 22:57, 2 August 2008 (UTC)

It's not impossible for a large animal to be able to fly. Pterosaurs are quite a bit larger than humans. As for the original question, just because being able to fly would be useful doesn't mean we are guaranteed to evolve it. It would be useful to fly. It would also be useful if we were stronger, more intelligent, had eyes in the back of our heads, could absorb energy from the sun directly, had four arms instead of just two, were immune to disease, had stronger teeth, had skin as hard as iron, etc. Mutations are random. Those mutations just never came up, therefore natural selection couldn't select those traits. Of course, if you wanted those traits, there's nothing stopping us from genetically engineering them... It would be extremely difficult though. ScienceApe (talk) 23:55, 2 August 2008 (UTC)

It's not size that's important, it's weight. That article says: "Pterosaur bones were hollow and air filled, like the bones of birds." Human bones are not hollow and air filled. You would have to significant lighten the human body in order to make it feasible for it to fly under its own power, and that has it's drawbacks (it would make us weaker, for a start - we break bones often enough as it is). --Tango (talk) 02:25, 3 August 2008 (UTC)

To be more precise, it's thrust to weight ratio that's important. Some of the largest pterosaurs such as Hatzegopteryx, were heavier than humans, but their large wingspan, and power allowed them to fly. For their size, they were quite lightweight due to hollow bones. ScienceApe (talk) 15:37, 3 August 2008 (UTC)

Synthesis problem

How might this synthesis be accomplished? I'm guessing that butadiene becomes the central part of the new molecule, but I don't see how to do the addition. --M1ss1ontomars2k4 (talk) 19:41, 2 August 2008 (UTC)

What does the text say eg "from any SM and S-C" - What does that mean.?87.102.86.73 (talk) 20:10, 2 August 2008 (UTC)

The little note says "from butadiene and any Starting Material 5 Carbons or less". --20:20, 2 August 2008 (UTC)

Oh, I was thinking that if I started with cyclopentene and used a bromine radical to abstract an allylic hydrogen, I might add that way, with 1 π electron from each double bond moving inward to form the new double bond and the other π electron moving outward to form a new bond with the allylic radical. --M1ss1ontomars2k4 (talk) 19:47, 2 August 2008 (UTC)

We cannot do homework for people on the ref desk. We can help point you in the right direction though if this is indeed a homework question. You will need to extend the butadiene by forming new carbon-carbon bonds. You may need to add some more reactive functional groups to it first. Note that the end product is symmetrical, this might make things easier. --Russoc4 (talk) 19:50, 2 August 2008 (UTC)

I'm not asking you to do my homework. I've already thought about it, and several classmates have already spent a great deal of time thinking about it (or so they've led me to believe). I've been here probably just as long as you, and I don't appreciate the fact that you assumed I was trying to get others to do my homework for me. This problem is neither homework nor required; I ask because there is an exam on Monday and this showed up in the professor's review handout (which has no solutions, just questions), and I'm assuming that we are expected to know how to do it, when I can't find anything in my notes or the text that seems to help with extending the butadiene or usefully adding functional groups.

The closest I've come so far is this: first hydroxylize the double bonds (monohydroxylation with BH3), use PCC without water to get to the aldehyde, convert cyclopentadiene into an organocuprate, then mix them up. Get rid of the carbonyl oxygen with whatever's handy, and you end up with something similar to the product but lacking a double bond. Besides the obvious problem of not making the desired molecule, this synthesis is far longer than our professor usually expects of us. Also, this is a class, not real life, so we're not expected to use BH3 as that was featured in another class. --M1ss1ontomars2k4 (talk) 20:19, 2 August 2008 (UTC)

I don't know if it is relevant to this problem, but don't forget the possibility of designing a reaction so that the rings of the molecule close up on their own. 71.16.107.2 (talk) 20:08, 2 August 2008 (UTC)

(convert to di-epoxide, react with 2x (3-metallo-cyclopenta-1-enyl) grignard, convert to 1,2 dioxide to an alkene...? There must be a better method)87.102.86.73 (talk) 20:15, 2 August 2008 (UTC)

As I've said elsewhere, this is a class, not real life, so while that may be a viable method of synthesis, converting alkenes to epoxides and using Grignards on them is probably not part of the solution. Pretty much the only tools we have are carbonyls and delocalized pi systems. --M1ss1ontomars2k4 (talk) 20:25, 2 August 2008 (UTC)

It says use any starting materials 5 or less C chains. What's wrong with Grinards? Is this what we've come up with so far, because it's all I can think of. I can't quite figure out how to get the double bond back without disrupting the cyclopentenes. And you aren't allowed to use reactions you've previously learned?? --Russoc4 (talk) 20:31, 2 August 2008 (UTC)

Update: is the last step here possible? --Russoc4 (talk) 20:46, 2 August 2008 (UTC)

Well I'm certainly allowed to use reactions I've previously learned, but all previous test questions I've done so far for this course haven't involved as much usage of "old stuff" as we've been using here, and this is from a review guide thing for the chapter on delocalized π systems. Plus, the teacher specifically mentioned that stuff from our previous course would not be tested in this course (except for basic things like ozonolysis, hyrdogenation of double and triple bonds, and oxidation with PCC and/or chromate) and that our syntheses should use stuff from this course. That's why I'm hesitant to use other stuff. As for the first image, that was indeed my thoughts, but like we've said, it doesn't quite work. The other reaction you've suggested can afford the desired product if ??? is PCC or chromate followed by Wolff-Kishner reduction, I think. Like I said though, this question is supposed to be somehow related to delocalized π systems... --21:24, 2 August 2008 (UTC)

P.S. Those are nice drawings; I would have done the same but 1. ChemSketch isn't cooperating with Wine and 2. I haven't really figured out how to make a nice reaction sequence like that; the arrows are always too long, too short, or not straight. --M1ss1ontomars2k4 (talk) 21:24, 2 August 2008 (UTC)

(IF I was teaching I'd assume that epoxidation and grignard reactions were basic things)

Have you done pericyclic reactions yet - I can't help wondering if there is a 'clever' way to do this using a cycloaddition followed by rearrangement - but nothing I can think of makes any sense...87.102.86.73 (talk) 21:39, 2 August 2008 (UTC)

Oh, Grignards are quite often used in this course, just not in this particular chapter. So they're less likely to be involved in the solution, but it's certainly possible. Epoxidation has never even been mentioned in this course, so that's most likely out of the picture... We have indeed done pericyclic reactions (specifically, electrocyclic reactions and cycloadditions) and that stuff is also in the chapter that this problem came from. That was my first though too, given the context of the problem, but I couldn't see any way to do it either. --M1ss1ontomars2k4 (talk) 22:06, 2 August 2008 (UTC)

Mmmh if you split the molecule down the middle you might get (C5H7)-CH2-CHO (you could dimerise this with a few steps..) Know any good ring contraction reactions (6 to 5) ???87.102.86.73 (talk) 22:27, 2 August 2008 (UTC)

ChemSketch can be tough to use. There is a toolbar button for reaction arrows. Anyway, you say it probably focuses on pi systems. The final product has no delocalized pi bonds, so going from a system with them to a system without them is going to take a considerable amount of energy. The only thing I can think of right now that comes close would be a pseudo-Freidel-Crafts reaction, but I'm not sure how to work it in here.--Russoc4 (talk) 22:30, 2 August 2008 (UTC)

Well, I tried to incorporate a Diels-Alder using butadiene, but that gets you to a 6 carbon chain. It would be quite the task to add only 8 carbons when the rings contain 5. Here's how I did it. Though all the transformations are theoretically possible, I definitely don't recommend using it. --Russoc4 (talk) 23:07, 2 August 2008 (UTC)

Ozonolysis of cyclohexene above will easily get you the six carbon chain. If you could cleave cyclobutene, you would get the four carbon chain that we got earlier, and then you could carry on. The only thing is that to get cyclobutene from butadiene is not a favored reaction, and would be pointless when you could just turn the double bonds of butadiene into aldehydes. --Russoc4 (talk) 23:34, 2 August 2008 (UTC)

According to our article on Grignards, Grignards also attack other electrophiles, including alkyl halides. So I think it might be possible for the allylic Grignard in the upper right corner of your image to make a carbon-carbon bond at those beta positions with bromines. My professor's hint (I emailed him with my thoughts and your idea about how to get the double bond in there) was that cyclopentene Grignard is correct; "Identify where the butadiene is and figure out what that needs to be if you are reacting it with grignards." I take this to mean that 1,4-dibromo-2-butene should be made from 1,3-butadiene, because that would certainly create the desired molecule; the creation of 1,4-dibromo-2-butene from 1,3-butadiene is actually given in the chapter. You mix the butadiene with bromine gas in carbon tetrachloride at 20 degrees C; unfortunately this only gives 46% of the desired dibromobutene. However, this seems far simpler than any of the other syntheses we've come up with, despite it not having much to do with pretty much anything in the chapter. Unfortunately, I don't think Grignards actually react with alkyl halides, contrary to what the article says, as otherwise they would react with themselves during preparation of the reagent. It looks like an organocuprate reagent has to be used instead. --M1ss1ontomars2k4 (talk) 23:55, 2 August 2008 (UTC)

Indeed. Making 1,4-dibromo-2-butene from butadiene would require a 1,4-addition to a diene. I was trying to avoid diene reactions because it could undergo 1,2-addition as well. The reaction conditions would have to be just right, and as you say, the yield is only 46%. I do not think that Grignards can attack alykl halides. This is why I would turn butadiene into the double-ended aldehyde. But, if you choose not to go this route, and would rather aim for 1,4-addition of bromine, I can tell you after some double checking that Gilman reagents do react with alkyl halides in the way you mention. --Russoc4 (talk) 00:12, 3 August 2008 (UTC)

human cloning

in human cloning, can it be done to make someone at desired age or start from a baby? will their life style be similar to ours, lifespan,health? should all the parts be stitched into them? when life is put into them, will they feel totally blank or will they remember anything, atleast can their brain adapt soon to its ambience? —Preceding unsigned comment added by Shiniga (talk • contribs) 19:44, 2 August 2008 (UTC)

At the moment it's nearly impossible to clone humans. Once we do, however, it would have to start from a baby, and it would hopefully have similar lifespan and health. They won't remember anything, as we don't know how to transfer memories. Of course, it's possible that in the future we'll come up completely new techniques to transfer memories, start clones off as adults (or make them mature faster), or whatever. It's hard to say for sure, as we're currently stuck in the present, and we can't even solve the problem of getting an embryo to develop properly. --M1ss1ontomars2k4 (talk) 19:50, 2 August 2008 (UTC)

Another thing to take into account is that clones will develop differently from the "original" because it is impossible to place them in indentical environments and chance events in development will result in them having non-identical physical and mental features. Clones should theoretically have about the same level of similarity that identical twins have with each other (they are not completely identical mentally or even physically). One problem with clones produced from mature cells is that they really don't have the same DNA. Cells modify their DNA epigenetically in order to regulate the activity of genes and to differentiate themselves from each other. If you use the DNA of a skin cell to create a clone, it already has been modifed. The electric shock is intended to strip some of these modifications off, but this is kind of like using an axe to cut a slice of bread, it's not very clean or precise and some modifications may stick around or the DNA could be damaged. Geneticists suspect this can lead to some down the road health problems, so clones produced from already differentiated cells may have reduced health compared to "originals".

If a clone is produced like a normal baby, then it has a "clean memory slate" and should develop and behave like any non-cloned human will. Thus a clone will be fully "human" in that it has an independent conciousness and will and is a totally different human being than the original, the same way identical twins are separate people. A clone of Gandhi would not be Gandhi: raised in a normal environment the clone is no more likely to become a great political spiritual leader than any other human on earth.

Memory and consiousness is created by the physical layout of the neurons in the brain, the structure and other stuff going on inside of the neurons themselves, how they connect to each other, and how they signal to one another. To reproduce someone's memory and personality (this is speculation by the way), identical neurons would have to be stuck in the same places, connected the same way, and induced to signal each other just like the originals. Brain development relies in part on chance events that even two genetically identical brains in identical conditions will not develop exactly the same. It would probably be easier to try to brainwash someone to believe that they had a past experience than to try to reproduce a memory by controlling the brain's development or creating a copy of a brain. 71.16.107.2 (talk) 20:37, 2 August 2008 (UTC)

I wouldn't say a clone of Ghandi is no more likely than the average person to behave like Ghandi. At least a portion of our personality comes from our genetics. And, if he were told he was a clone of Ghandi, this might make him more likely to behave like Ghandi than to run a convenience store. StuRat (talk) 02:41, 3 August 2008 (UTC)

Instead of thinking of cloning as "copying", think of it as making a baby that happens to have the same DNA as someone already alive, instead of new DNA from a mother and father. --98.217.8.46 (talk) 23:43, 2 August 2008 (UTC)

Well your age has nothing to do with your physical size. Afterall, humans define age relative to childbirth, thus you have to realize the biases that exist in discussing the cloning issue. A successful living human clone would think of hisself or herself the same way you think of your self. The clone would start out as a single cell, just like you or I would. Some humans (not clones) already feel memories of past lives and I've met someone who truely thinks that they were in WW2 in a past life. So if a clone had similar memories, are they more valid? Sentriclecub (talk) 02:54, 3 August 2008 (UTC)

Any clone would start from age zero, just like anyone else. However, there are ways to alter the rate at which the clone would grow. Dolly the cloned sheep, for example, may have been inadvertantly made to age more rapidly by the cloning process. StuRat (talk) 16:51, 3 August 2008 (UTC)

Pigs on the wing

How difficult would it be for humans to genetically engineer a pig with wings and the ability to actually fly? —Preceding unsigned comment added by 84.66.29.34 (talk) 22:26, 2 August 2008 (UTC)

Very - a pig is far too heavy to fly under its own power without massive changes. You would probably be better off starting with a bird and engineering it to look like a pig. --Tango (talk) 23:27, 2 August 2008 (UTC)

It would involve more than one gene. The pig, if you removed enough genes and substituted them with the minimum amount of alleles to accomplish the goal, then you may have removed so many genes that the pig lost some of its familiar phenotype (e.g. can it lose its curly tail and still be called a pig?) Speciation is a wreckless art, and one of the few agreed upon criteria is the count of chromosomes. That said, its probably possible, but I dont know how you can "program" the pig to know how to fly? I mean, what if we gave him the genes to grow some spectacular 30 feet wings made out of a super-light biologically feasible polymer? It might need a "mother" to teach the pig how to use it. i.e. like how those otters can crack shells on a rock--its learned from other otters. But I'd say its definitely possible. Look how far nature has came? A tyrannosaurus from a bacteria? or a flying pig from a regular pig given the earth is populated with a flood of nobel laureates in biomedical engineering (and hopefully this one some day ;) I think its less of a challenge to make enough genetic modifications to pig to accomplish your goal, than what nature has already done (t-rex from a prokaryotic bacteria, one or two incremental gene modifications at each offspring level). The main bottle neck is that we don't have computers than can predict the tertiary and quaternary structure of proteins given a sequence of amino acids. (the sequence of amino acids is the unit of a gene) Sentriclecub (talk) 02:34, 3 August 2008 (UTC)

The answer I've heard used for this type of question is another question: "How many corners can you add to a circle to make look like a square?" None - it is impossible. Once you add a corner (or four of them) to a circle, it is no longer a circle. So, it can never be a circle that looks like a square. Similarly, if you replace a pig's front legs with wings, it will not longer be a pig, so it will never be a pig that flies. If you want a serious discussion on this topic, try something like, "How many (or what specific) body parts in a human can be replaced with artificial parts without making the human non-human (ie: a robot)?" -- kainaw™ 03:36, 3 August 2008 (UTC)

Genetic engineering is only about changing the pig's DNA so that a 1-celled embryo with the modified genes grows up into a fully developed organism with his stipulated phenotype. Replacing tissue doesn't count since it would then answer a question that asked can I surgically put wings onto a pig? Sentriclecub (talk) 03:57, 3 August 2008 (UTC)

After carefully reviewing the semantic structure of the OP’s question, I believe that it can be logically deduced that s/he is talking about STARTING with a pig. This is a good example of the sorites paradox by the way. --S.dedalus (talk) 05:07, 3 August 2008 (UTC)

Yes, I was thinking about achieving the end result of a pig that looks like a pig - but with wings on its back. Which would mean giving it six limbs. --84.71.59.70 (talk) 22:16, 3 August 2008 (UTC)

While we are speaking hypothetically, would a different technique (not genetic modification) be easier to accomplish the task at hand? (I.E. structural reformative surgery, or something drastically different?) Nimur (talk) 17:27, 3 August 2008 (UTC)

Just attach it to an airplane. We can even put a chip in the brain of the pig and allow it to pilot the airplane with its mind. If you're only counting adding biological tissue, I'm not sure if we can do it now, but it's still definitely much easier than genetic modification. It's much easier to graft wings onto a pig than to modify its genes so they interact with each other in in such a way that perfectly functional wings sprout out of the pig's back. — DanielLC 03:23, 4 August 2008 (UTC)

Risk of contracting MRSA

Would it be possible to contract MRSA by picking your nose, and eating it? --russ (talk) 22:46, 2 August 2008 (UTC)

Nostrils are one site for MRSA infection. If you picked your nose, and what you picked has MRSA in it, you are likely to already have contracted the disease.--Fangz (talk) 23:02, 2 August 2008 (UTC)

If you picked someone else's nose and ate it, maybe. You can't contract a disease from yourself, since it would require you to already have it. --Tango (talk) 23:28, 2 August 2008 (UTC)

You wouldn't be contracting a disease from yourself though. You would be allowing a way for the bacteria that always live on your skin to enter your body and initiate the infection. --Russoc4 (talk) 00:00, 3 August 2008 (UTC)

If it's already in your nose, I think you're probably already infected. Bacteria can get on the skin from all kinds of places, but getting into the nose would probably require you to either inhale it, or for it to come from the inside, either way, you're already infected. In fact, even without that, eating it isn't that likely to cause an infection - stomach acid is pretty good at killing bacteria. You're more likely to get infected due to scratching the inside of your nose and letting the bacteria in that way. --Tango (talk) 02:21, 3 August 2008 (UTC)

The mrsa is more likely to infect you by crossing the thin wet linings of epithelial tissue in your nose, than risk the harsh environment of the stomache. Indeed scratching your nose might invoke tissue damage and weakness. 99x more likely to contract it in the local proximity of your nasal cavity than your mouth/throat/stomach/intestines. Sentriclecub (talk) 02:49, 3 August 2008 (UTC)

I'm not satisfied with the answers so far. In fact, staphylococci in those parts of your nose you can get at with fingers aren't something to be worried about, it's perfectly normal. That's why a good doctor, when checking for systemic MRSA, will make smear tests of your nose and your throat because if you have something in your sinus it will show in a throat smear.

Now, to the bogey eating part, it's not the worst you can do, as long as you have stomach acid and a good digestion. Actually, it's even clever, because your immune system will see the digested parts and learn from that. The worst would be trying to clean your nose the usual way, i.e., by pressuring your nose while holding a kerchief (and possibly closing the nose opening, that's the really worst), because this way you push the MRSA into your paranasal sinus where it will thrive and go into the other sinuses. --Ayacop (talk) 07:38, 3 August 2008 (UTC)

You lost me at a good doctor, when checking for systemic MRSA, will make smear tests of your nose and your throat because if you have something in your sinus it will show in a throat smear.

In my unscientific opinion, MRSA is just a fancy staph infection. The question could be answered if the OP inserted the word staph infection for MRSA. The only difference being that MRSA is linked to Stevens-Johnson syndrome which is a nightmare. The question can be answered with a yes and more specifically by explaining the two infection risks (specifically the picking with fingernail, and the ingestion of contaminated mucus). I think this question has been satisfactorily resolved, and exceeded the expectations set forth by the OP. Could we do better? Yes! I think the OP has been treated very diligently and will use this service again. I hope he enjoys his experience with wikipedia and will think highly of its hard-working editors. Sentriclecub (talk) 11:57, 3 August 2008 (UTC)

The answers thus far have failed to distinguish between infection and colonization. If MRSA is residing in your nose without causing disease, you're colonized, not infected. The usual reason for culturing someone's nose is not to determine if he's infected, but rather whether he's colonized. If a colonization is found, it can be treated with topical antibiotics to reduce the risk that MRSA will be transmitted to someone else, who (especially in hospital settings where this is done) may be less well immunologically equipped to deal with the organism and would develop an actual infection. - Nunh-huh 15:48, 3 August 2008 (UTC)