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May 19

Nitroglycerin final ph

many people take Nitroglycerin for heart problems and its also added to gunpowder. since its made from nitric and sulfuric acid. wouldent it burn the mouth of the patient taking it and cause corrosive damage to the gun barrel? —Preceding unsigned comment added by Tom12350 (talk • contribs) 00:31, 19 May 2010 (UTC)

Reviewing several nitroglycerine MSDS safety sheets from various sources, nearly all list "not applicable" for the pH. For example, Nitroglycerin MSDS from Duke University. There are other hazards, including flammability and shock sensitivity; for skin contact, the MSDS suggests immediately flushing with water (though this is contraindicated by the typical medical application, rubbing it on the skin - but medical nitroglycerin is often dissolved in propylene glycol and is not pure). I would speculate that pure nitroglycerine has an almost perfectly neutral pH, if anybody bothered to measure it, gauging from its chemical structure; keep in mind that just because a precursor chemical was a strong acid does not mean that the final product is also a strong acid. As far as reactivity with metals, no metals are counter-indicated on the MSDS. Nimur (talk) 00:49, 19 May 2010 (UTC)

Seenitroglycerin manufacture. Oxide atoms are basic, but they are "locked up" in the glycerol structure. When the strong H⁺ ions attack the glycerin (along with the nitrate), the oxide atoms react with the hydrogen ions to form water, which is neutral. --Chemicalinterest (talk) 11:55, 19 May 2010 (UTC)

It's true that there are components that act as acid and base and give water in the reaction process (leading to neutral product), but the question wasn't about why glycerin doesn't make things basic. Also, please read the production section you mentioned to see how it actually happens--the mechanism you explain is not correct. DMacks (talk) 14:14, 19 May 2010 (UTC)

There is no reaction on that page that shows how the acids are added to the glycerol to form an ester(an ester is the compound of an alcohol and an acid, it doesn't specify whether it's inorganic or organic). If it is esterification, then they react to form the ester(glyceryl trinitrate) and water. I'm just saying that the acids are neutralized, so there is not harm from protons like there is in the free acid. --Chemicalinterest (talk) 21:37, 19 May 2010 (UTC)

To quote the article, "The sulfuric acid produces protonated nitric acid species, which are attacked by glycerin's nucleophilic oxygen atoms. The nitro group is thus added as an ester C-O-NO2 and water is produced.". That's...pretty clearly not "Oxide atoms are basic, but they are "locked up" in the glycerol structure. When the strong H⁺ ions attack the glycerin (along with the nitrate), the oxide atoms react with the hydrogen ions to form water". The nitrate is what attacks the H⁺; the glycerin O remains within the structure. DMacks (talk) 23:13, 19 May 2010 (UTC)

This esterification reaction involves the replacements of the OH^- groups in the glycerol with NO₃- groups. The H₂SO₄ acts as a catalyst. The H⁺ from the nitric acid and the OH^- from the glycerin react to form water. So the simplest(not the mechanism of reaction, just the difference between reactants and products) formula would be glycerol + 3 nitric acid → glyceryl trinitrate + 3 water. You can see how the acid is neutralized. What makes nitro explosive is because the reducing carbon group is bonded to the oxidizing nitrate group. --Chemicalinterest (talk) 11:19, 20 May 2010 (UTC)

Aircraft repairs

Would a blowtorch burn in a monsoon? I'm planning to write a novel about a flight around the world, and in one of the proposed scenes the pilot, while getting ready to depart from Calcutta on the first day of monsoon season, discovers that the plane has been sabotaged at an earlier stop in Pakistan by clipping the generator wires, and decides to repair it by soldering the wires together. Unfortunately there's no power available to run the electric soldering iron (the plane's battery is dead, and the generator is obviously non-functional), so the soldering iron has to be heated using a soldering torch, which has to be used a safe distance away from the fully-fueled aircraft, in the torrential rain. What (if anything) is wrong with this picture? Thanks in advance! 67.170.215.166 (talk) 01:37, 19 May 2010 (UTC)

Twist the wires together along with a strand or two of soldering wire and then heat with the blow torch directly until the solder melts, that would work. I'd be more worried about taking off in a monsoon then soldering some wires together near a fueled plane, especially since presumably everything's going to be pretty wet. I've arced a battery under the hood of a "fully fueled" car by accident more then a few times without any explosions so far. I'm pretty sure you can even weld under the hood without too much risk, unless you directly contact the fuel lines or components. Vespine (talk) 03:35, 19 May 2010 (UTC)

Just a note that doesn't really answer your question. Cutting the generator wire may not be a logical way to sabotage an aircraft - piston aircraft do not need a functioning battery or alternator (which is the generator that charges the battery) to remain flying with the engine(s) running. They use magnetos. Without a functioning battery, you have to hand-prop the aircraft (which means turn the magnetos on and turn the propeller(s) by hand until the magnetos engage and the engine is running by itself, which I should mention is dangerous if you are not trained in doing that), because the starter won't work and the turn coordinator, radios, navigation equipment, lights, and some of the other gauges, such as the fuel guages, would not function. If the attitude indicator is electronic (which is typically not the case, at least not on single engine aircraft such as the one I fly), that would not work either. Vespine brings up a good point. You want your electronics working if you are going to be flying through clouds. A good pilot will make the choice not to fly for any reason if the weather is dangerous, but since it's a book, you have a lot of leeway ;-). Falconus^{p t c} 03:42, 19 May 2010 (UTC)

I think Falconus would agree that 90% of pilots in this situation would unhesitatingly hand-start the aircraft, because that's the macho thing to do. The least likely part of the whole scenario sounds like the pilot taking off in a monsoon at all. Comet Tuttle (talk) 06:01, 19 May 2010 (UTC)

Um, no, I would not agree with that at all... I was talking about what is technically possible, not what is the smartest thing to do. While there is not an inherent risk to flying without the electrical system (heck, some aircraft don't even have an electrical system), that is only under optimum conditions (excellent weather, no need to fly through airspace requiring a radio, etc). I personally would not be comfortable doing that even if I knew the area like the back of my hand. If the weather was going to be bad, the pilot would have to be a certifiable madman to make the decision to fly without the electronic navigational devices, various gauges, radios, and the electrical instruments. I seriously doubt that many pilots would choose to fly with no electronics for a long distance flight (I could see with a GPS, and a backup GPS) even in great weather. It just isn't worth it. There are a couple of pilots that are "macho" and they are the ones that end up in the news. Maybe a handful (I'm guessing) would seriously consider flying in a foreign land with an aircraft that does not have any of the equipment that they typically rely on, but of these, I can only hope that very few would be stupid enough to attempt it in poor weather. Most modern pilots operate under the "err on the side of caution" philosophy. People don't realize that, because those pilots don't end up in the news. Falconus^{p t c} 06:28, 19 May 2010 (UTC)

Also, I should mention that hand-propping works (in theory) on all piston aircraft, but is rather dangerous to attempt on tricycle gear aircraft, just because when you lean forward to push the prop down, your head gets way too close to the arc. That is another reason why I would never attempt it on the aircraft I fly (reason 1 being that nobody has ever shown me how). Falconus^{p t c} 06:33, 19 May 2010 (UTC)

If the airplane was sabotaged in Pakistan, how did it get to Calcutta in India? And if the sabotage was so minor that the pilot simply flew from Pakistan to Calcutta, why doesn't he just fly on to his next port and fix the damage there, or somewhere else where it will be more convenient and miles away from the monsoon? Dolphin (t) 12:14, 19 May 2010 (UTC)

To answer your questions in the order asked:

1)The presumable intent of the saboteur(s) was not to prevent the plane from taking off altogether, but to cause a dangerous failure once in the air (the Paki saboteur was presumably angry with the pilot for breaking sharia law and then resisting arrest);

2)To this effect, the wires on the generator (mounted on the starboard engine in this model of aircraft) have been cut and then loosely re-attached in such a way as to vibrate loose during flight (also, the machine screw holding one of the valves on the portside engine has been loosened, which will cause a failure further down the line), therefore the sabotage has gone unnoticed until after landing in Calcutta;

3)During the flight from Pakistan to India, the weather is for the most part CAVU, so one could get by without electrical power, whereas from Calcutta to the next stop (Bangkok) it's close to zero-zero -- therefore, for this flight it's absolutely imperative to have fully functioning flight instruments and a working power supply. 67.170.215.166 (talk) 23:43, 19 May 2010 (UTC)

Guys, the question has little to do with the above answers. All he wants to know is if a blowtorch will work in a torrential downpour. Googlemeister (talk) 12:53, 19 May 2010 (UTC)

Oxy-acetylene torches will even work under water (see underwater welding), because they provide both fuel and oxidizer. If the wind were very strong, it is conceivable that the flame would blow out, but I think it's reasonable to say the rain is not an issue. Nimur (talk) 13:52, 19 May 2010 (UTC)

The following "retro" methods of soldering are not suggested as being safe or practical for actual usage, and are only presented in the context of possible use in the fictional work described above. In practice, there would be danger of burns or of starting something on fire, and hazard from inhaling lead fumes. If the electric soldering iron is heated while the wind is blowing and it is getting rained on, it will cool off too much to melt the solder by the time the hero has run several paces from his "safe open flame" location to where the wires are. In the early 20th century, there were soldering irons which were designed to be heated by a torch, (see some at [1]), and they had several ounces of copper in the business end. They would stay hot a bit longer. Something with several ounces of metal and an insulated handle or a handle that could be gripped with Visegrip or similar pliers could be heated with a torch or fire and might stay hot enough to heat the copper wire as well as melting the solder (needed to avoid a cold soldered connection). Maybe a golf club could be pressed into service as such an improvised soldering iron (though with an unwieldy long handle) or a small hammer with a metal handle and a leather grip further insulated with rags could be used, but a larger torch than a little propane torch would be needed to heat it. Maybe some aviation fuel could be burned in a can to heat the found soldering iron. A soldering iron, to melt solder, does not need to be red hot, so if heated red hot, it would still be at working temperature after it cooled a bit. Another old soldering trick is the solderpot. The wire connection was twisted together and left dangling downward. The solder was melted in an iron pot over a flame, and lifted up so the wires dunked into the solder. If there is enough solder, and a metal can, like a metal measuring cup and any sort of fire, and pliers to hold the can with, this would be an easy solution to the problem. If you Google ehow solder pot there are detailed instructions for using a solder pot. Edison (talk) 15:31, 19 May 2010 (UTC)

Thanks everyone, I think I'll have my hero(ine) use a torch-heated soldering iron that he/she has in the toolkit as a backup for the electric iron. BTW, if it's safe to heat the wires directly with a blowtorch on a fully-fueled twin-engine plane that has more than a thousand gallons of 100-octane avgas on board (as Vespine claims), I don't see why using a torch to heat the soldering iron while in close proximity to said fully-fueled plane would pose a significantly bigger danger of "setting something (i.e. above-mentioned plane) on fire" -- if anything, the danger would be less in this case. And as for hazard from inhaling lead fumes, it's very much overblown -- lead is not so volatile as to give off more than a tiny bit of fumes at the temperatures involved, so the pilot's exposure won't be significant (even if said pilot is a pregnant woman) from doing this job just one time. IMHO a bigger danger would be either setting the plane on fire with the blowtorch, or getting your fingers chopped off afterward when hand-propping the engine. FWiW 67.170.215.166 (talk) 00:01, 20 May 2010 (UTC)

Notes like the one about lead fumes are just ass coverage in case someone in the future reads a good-faith ref desk posting and does something idiotic like sitting in a small closet with a boiling pot of lead solder for hours, then wants damages paid from the person who posted information. We live in a litigious society. The US government has regulations to prevent children eating bicycle gears which contain lead. Personally I like the narrative having the person take a pipe cap and make it into a solder pot, heated over some burning fuel. Edison (talk) 19:04, 20 May 2010 (UTC)

Above seems about right. Comment - in the context of this story the whole thing seems a little like overkill - just as easy to strip the two wires, force them together, and tape up - and weak connections will spark and tend to just spot weld the wires together, additionally solutions such as finding a jubilee clip of similar clamp seem a lot simpler for our hero..77.86.115.45 (talk) 16:48, 21 May 2010 (UTC)

Good point about twisting the two wires together and taping the joint, that's another option for making the repair. However, jubilee clips are used on hydraulic lines, not on electrical wires (easy to see why, 'cause they're made of metal and thus conductive). 67.170.215.166 (talk) 04:19, 22 May 2010 (UTC)

soap labels

i noticed that some liquid soap bottles have a paper label. (dr. bronners is one i think but there are others as well) that label dosent dissolve even in my shower.

A) what kind of paper do they use that dosent dissolve and B) what kind of ink do they use that dosent run and C) what kind of glue do they use that dosent dissolve but it also safe for skin contact ect. —Preceding unsigned comment added by Tom12350 (talk • contribs) 02:40, 19 May 2010 (UTC)

FYI...Dr. Bronner's paper labels do most certainly dissolve, which might explain why they don't use them as much anymore in their liquid soap products under the half-gallon size. Sounds like your bottle isn't getting wet. Long-term users of the good doctor will often buy the soap in bulk and transfer it to smaller bottles, which often lacks a label. It's true that the paper labels on the old bottles didn't come off easily, however, and could take up to six months or so if you reused the bottle as I describe above, so maybe there was some water-resistant protection, but I think the company phased out the paper labels on the smaller bottles to save trees. Viriditas (talk) 04:21, 19 May 2010 (UTC)

i dont use Dr. Bronner's that much but other soaps labels i have dont come off that easily . in general what are they made out of? —Preceding unsigned comment added by Tom12350 (talk • contribs) 05:31, 19 May 2010 (UTC)

The new bottles have silk-screened labels, so no paper. Keep in mind, this is one of the most famous liquid soap labels in the world, so you should be able to find out what the old label was made of very easily. You can contact the company here. There's a phone number listed on that page as well. Remember, DILUTE! OK! Viriditas (talk) 06:49, 19 May 2010 (UTC)

can we stop talking about dr. bronners. i said i have other soap labels i have dont come off that easily . in general what are they made out of? they are a type of paper im holding one right now. —Preceding unsigned comment added by Tom12350 (talk • contribs) 08:39, 19 May 2010 (UTC)

Our Waterproof paper article is extremely sparse, but it does have a couple of references. The Times Higher Education link ([2]) describes a recent breakthrough in making waterproof paper. Making paper waterproof--and writable from CNET says, "Manufacturers today produce waterproof labels, but it requires embedding polypropylene fibers in paper. The process is expensive but also makes the paper waxy and tough.". Apparently the big push is to make waterproof labels which are also ecologically friendly.

Sadly, Waterproof ink and Waterproof glue are redlinks; this suggests that one way of making waterproof ink is to add glue to it, but it doesn't go into much detail.

There appears to be a wide spectrum of waterproof glues from make your own! (Cheese required) to Clues to Waterproof Glue Found in Antarctic Creature. It actually seems as though the glue may be the most straightforward of the three to create. --Kateshortforbob _talk 15:18, 21 May 2010 (UTC)

Could it be that both the paper and the ink are impregnated with waterproof glue to increase the water resistance? That would be the most logical solution for me. 67.170.215.166 (talk) 04:22, 22 May 2010 (UTC)

Lung cancer tumor eroding bone in rib

Hi There, My father was recently diagnosed with non-small cell lung cancer. The doctor said this has not spread to the bones but that it has eroded the rib at the tumor site. My question is what is the mechanism whereby the cancer causes the bone to erode? This is not a request for advice, I am wondering about the physiology of the bone deteriorating. Thanks! —Preceding unsigned comment added by 64.234.6.24 (talk) 04:41, 19 May 2010 (UTC)

I believe the erosion is simply due to pressure from the tumor, but I can't seem to find a citation to back this up. Regards, --—Cyclonenim | Chat  06:35, 19 May 2010 (UTC)

I would say metastasis (Lungs, bones, liver, and brain are the most common metastasis locations from solid tumors). AFAIK Lung cancer frequently sends metastasis to other organs through blood circulation. Metastasis are colonies of amorphous tumoral cells that substitute, in this case, bone tissue, making it more fragile. --151.51.20.38 (talk) 17:43, 19 May 2010 (UTC)

The docs were very specific, based on PET scan, that the cancer had not metastisized, rather the tumor had caused the bone to deteriorate. We will see the doc Monday and I will ask him about the mechanism of this as it seems the question is more difficult than I imagined. Thanks! —Preceding unsigned comment added by 64.234.6.24 (talk) 01:01, 20 May 2010 (UTC)

Perhaps the tumor is sucking too many nutrients from neighboring tissues? 67.243.7.245 (talk) 04:16, 20 May 2010 (UTC)

This section is a perfect example of why Wikipedia policy forbids giving medical advice. Looie496 (talk) 14:20, 20 May 2010 (UTC)

I don't believe this is an instance of a poster seeking medical advice, though you're welcome to take this up on the talk page, Looie496. (Granted, the reliability of the answers here is certainly dubious. Responders should remember that our goal is to provide detailed, factual, referenced responses to questions — not guesses.) TenOfAllTrades(talk) 15:09, 20 May 2010 (UTC)

In general, tumors (primary tumors and metastases) don't generally directly attack bone. Instead, they may secrete factors (proteins) which locally or systemically up-regulate the activity and growth of osteoclasts: cells that normally resorb bone at a carefully-maintained level. (While bones look static, they're actually continuously being taken apart and regenerated at a microscopic level. Osteoblasts build new bone, while osteoclasts trim it back; it's a dynamic equilibrium that responds to stress, strain, and fracture.)

There's a whole alphabet soup of different proteins which can be involved in shifting the balance from bone maintenance to bone destruction. Here's one paper – that I've linked to primarily because the fulltext is free – which specifically fingers MCP-1 in some non-small cell cancers; the discussion section towards the bottom of the article also lists a large number of factors identified in other studies.

To further complicate matters, the tumors don't have to secrete the osteoclast-stimulating factors themselves — the presence of an invasive tumor can trigger an inflammatory response in nearby cells which in turn drives osteoclast activation. This latter model is similar to a process of bone loss seen in inflammatory arthritis: [3] (that paper deals with cholesteatomas, but the idea is the same).

In other words, there are a number of mechanisms which can ultimately lead to overstimulation of osteoclasts and bone loss. I can't speculate on which might be active in any particular patient, and your father's oncologist is the one to talk to about treatment or prognosis options. TenOfAllTrades(talk) 15:54, 20 May 2010 (UTC)

Great, just what I was looking for. Thanks Ten! —Preceding unsigned comment added by 64.234.6.24 (talk) 16:57, 20 May 2010 (UTC)

safety of tinned food

Is it safe to eat tinned food that is past the use-by date? I have some tinned tomatoes that are about 4 years out of date, but it's a "best before" date rather than a use by date. I've checked the article, but it doesn't say there. Thanks in advance, It's been emotional (talk) 06:41, 19 May 2010 (UTC)

By definition, goods are not considered safe for consumption after the use by date.--Shantavira|^{feed me} 07:17, 19 May 2010 (UTC)

This article suggests that that may not be necessarily true: "Canned food retains its safety and nutritional value well beyond two years, but it may have some variation in quality, such as a change of color and texture. Canning is a high-heat process that renders the food commercially sterile. Food safety is not an issue in products kept on the shelf or in the pantry for long periods of time. In fact, canned food has an almost indefinite shelf life at moderate temperatures (75° F and below). Canned food as old as 100 years has been found in sunken ships and it is still microbiologically safe". Ghmyrtle (talk) 07:21, 19 May 2010 (UTC)

The integrity of the container is of paramount importance. Any rust? any dents? Discard the can. 218.25.32.210 (talk) 08:09, 19 May 2010 (UTC)

In part this will depend on how the canned food was sterilized. Some are irradiated thoroughly to kill off practically all microbes within the can, and this can leave the food with a use by date into tens of years. Whether it'll still taste good is a different matter. Regards, --—Cyclonenim | Chat  11:08, 19 May 2010 (UTC)

There is a reason they put a "best before" rather than a "use by". The former means that the texture or flavor may not be at it's absolute peak after that date - the latter means that you need to toss it out. So I would expect this stuff to be perfectly OK to eat. Most canned goods retain their edibility for decades. However, whether it still tastes OK is a different matter. Open one and find out! If it's been rotting for two years, you'll definitely know! SteveBaker (talk) 14:44, 19 May 2010 (UTC)

I would argue against the "just try it" method. Rotting is obvious, yes, but not all dangers come from rotten foods. Bacteria may set in that haven't really produced noticible decay. Bascially, the "use by"/"best before" date is the longest a company is willing to assert that the food is fresh and safe. Beyond that, you're taking a risk with the product. — The Hand That Feeds You:^Bite 15:15, 19 May 2010 (UTC)

With tomatoes one concern is corrosion of the can. The acid in tomatoes will quickly corrode an unprotected can. This is solved in the short term by lining the inside of the can with enamel or a layer of polycarbonate (yes, there's BPA in food cans). These will only last for a short time. After a while, they'll no longer be sufficient to protect the metal from acid errosion, and your tomatoes will get an off "metallic" flavor, or become unfit for consumption. -- 174.24.200.38 (talk) 16:13, 19 May 2010 (UTC)

I'd put inspection way over any date for determining if it's good. Is the can corroded, dented, bulging ? Toss it. If not, open it up. Are the tomatoes gray and bad smelling ? Toss them. If it looks and smells good, take a taste. If it tastes bad, toss it. If not, eat up. I've also had many items go bad before the USE BY date, it's more of a question of being 100% sterilized or not. If not, the food is unsafe almost right away. StuRat (talk) 17:57, 19 May 2010 (UTC)

If a can has been properly sterilized, there won't be even one single living microorganism in the whole thing. The "best before" dates are related to possible deterioration of the nutrients, not to bacterial growth. The speed of deterioration is tremendously dependent on temperature, though, so it's hard to set fixed time spans for usability. Looie496 (talk) 20:22, 19 May 2010 (UTC)

It's not just microorganisms that can be dangerous though. As Mr. 174 pointed out, there could be metal leaching into the food, perhaps to an extent to be harmful to the OP's health. It's not like canned tomatoes are that expensive; buy a new can. Buddy431 (talk) 04:25, 20 May 2010 (UTC)

Can coyotes co-exist with elk for any duration of time, without attacks?

Sorry for all the "wild animal kingdom" questions, but I'm on vacation and thought this board would have some biology experts about. Anyway, all I'm basing my question off of is what I could see through my binoculars and a Maglite pointed into the dark. A coyote was barking/howling about 20 feet away from me (I'm on a high porch facing a valley); he was loud enough to scare the daylights out of me when I was inside, and I quickly went out to listen to him. I could hear him sort of "quietly" grunting (when not howling). He stopped... so I ran inside to get the binoculars and flashlight, and when I returned, he was gone. However, a small herd of elk was grazing about 50 feet off to my right, and I saw two or three pair of "floating" eyes in the distance on the left. That meant the coyote was standing amidst this small herd, and I stood out there for probably 20 minutes waiting for a pack to take down one of the elk. But nothing happened. Is this ... normal? Any ideas what was going on? Was the coyote trying to spook the elk away? Cause it didn't work lol. Thanks so much in advance. And also if any birders are around, I'm still hoping for a bird call identification up in my "Loons in Colorado" question above. – Kerαunoςcopia^◁_galaxies 08:37, 19 May 2010 (UTC)

If the coyotes had just eaten, they might not want to eat the elk. But that doesn't explain why the elk weren't scared of them. --Chemicalinterest (talk) 11:42, 19 May 2010 (UTC)

I would be pretty surprised if a single coyote was any threat at all to an adult elk. That could explain their apathy, especially if the herd did not have any young. Googlemeister (talk) 12:48, 19 May 2010 (UTC)

Exactly. I don't like the chances of a coyote bringing down an elk, even if they have a partner, unless there is some exceptionally vulnerable herd member around. Those antlers aren't just for show. Vranak (talk) 12:57, 19 May 2010 (UTC)

Agreed, you'd need a wolf pack to hunt adult Elk. StuRat (talk) 17:50, 19 May 2010 (UTC)

Googlemeister, there was only one coyote from what I could tell, so maybe that's it. And I've seen entire roads closed off with signs saying "Closed until summer for elk calving", so maybe there weren't any young yet. I'm directly in the path of the elks' migration as they're always coming through here. So maybe one coyote decided to get a little possessive of his territory or something, it was kind of amusing. Thanks all for your replies, I greatly appreciate it. – Kerαunoςcopia^◁_galaxies 19:32, 19 May 2010 (UTC)

To be honest, I doubt the coyote calls had much to do with him trying to warn off the elk; it probably had more to do with letting other coyotes in the area know that he had claimed that bit of property. Matt Deres (talk) 20:32, 19 May 2010 (UTC)

Interesting. The Coyote article though mentions the territory thing doesn't happen until fall, and it's spring here now. But if that's the case, I kind of hope he returns. – Kerαunoςcopia^◁_galaxies 20:55, 19 May 2010 (UTC)

Turning off car

Over here in my city, we have timers on traffic signals that show how long till the signal turns green or red. I turn off the car when the timer is over 30 seconds( for it to turn green). I know that starting the car back on consumes fuel, but my question is how much time on the timer would make it feasible to turn off an average family sedan (mine is a 2000 Honda Civic). Thanks.--119.155.30.13 (talk) 10:34, 19 May 2010 (UTC)

Besides the cost in fuel, you should also calculate in the extra wear and tear on your starter. The starter for my Jeep is pretty cheap and it's a breeze to replace but yours might be different (more difficult/expensive). Dismas|^(talk) 10:55, 19 May 2010 (UTC)

An idling 4-cyl consumes around 1 liter per hour. Let's say you managed to save 10 minutes idle time each workday, it's around 40 liters annual savings. Is it worth it? If the car is out of warranty period, think of what Dismas said. IMO, if idle time becomes a financial (not just ethical) concern, you need to reconsider your daily route, place of work etc. East of Borschov (talk) 11:30, 19 May 2010 (UTC)

Recent BMWs turn of the engine automatically at any stop, and start it again when the accelerator is depressed. So the wear on the starter cannot be that bad. --Stephan Schulz (talk) 11:40, 19 May 2010 (UTC)

From what I had explained to me by a BMW salesman, the engine doesn't turn off-off. It's just a sort of really low "state". Rimush (talk) 13:11, 19 May 2010 (UTC)

I haven't seen an idle-shut-off feature listed on any of the marketingese at the BMW website; I suspect there's a misconception here. The Toyota Prius, however, does have the capacity to shut down when idle - but it has a completely different engine design, called the Hybrid Synergy Drive. In fact, it has no "starter motor" - the hybrid motor is the starter. This complete re-engineering changes the fuel-consumption/wear-and-tear tradeoff equation very significantly. But in an ordinary car, I would think that the extra wear on your starter is not worth the small fuel savings you may be getting by shutting down when idle. Nimur (talk) 13:39, 19 May 2010 (UTC)

They definitely had the feature on the BMW 1 Series in 2007-08. Maybe they discontinued it, or it's an Euro-only thing. Rimush (talk) 13:41, 19 May 2010 (UTC)

It is certainly a feature of some BMW cars.

On older cars without computer-controlled fuel injectors, I think the extra fuel used to restart the engine made it not worthwhile to stop the engine for the duration of a traffic signal. But modern cars can inject just exactly the right amount of gas to restart an already warm engine - so there is almost zero penalty for doing that - and killing the engine for even a brief stop turns out to be worthwhile.

However - there are some weird legal issues in some US states over cars that do this automatically - and the car manufacturers won't make different designs of cars for different states - so if just a couple of states have stupid laws, everyone is screwed (think about that the next time someone advocates increasing state's rights over federal government!). But certainly there are plenty of cars in Europe that do this. The MINI (which is a BMW brand) has different software in the USA and in the rest of the world specifically for this reason. The law here in Texas was designed to outlaw those remote starters that some people in cold climates use to start their cars 5 minutes before they go outside so that the engine and passenger compartment are nice and warm when they go to drive off. These things can be dangerous if someone leaves the car in gear by mistake or something. It seems that this law was written stupidly such as to disallow any device that causes the car to start without someone inside the car specifically commanding it to do so...or some such madness. Anyway - on my MINI (bought in the US), it doesn't do it - and on my sister's almost identical one (bought in the UK), it does. The Prius got away with it by saying that the engine doesn't directly drive the wheels - so technically it's just a generator. The answer to this question is that, yes, it does save gas to do that - and no, it doesn't noticably shorten the life of your starter motor. Even if it did, it, it also lengthens the life of the rest of your engine, clutch, water pump, belts, etc, so it would be a net win in any case. The latest MINI goes even one step further - when the engine has automatically stopped - and you push gently on the gas pedal, it rolls the car forwards using only the starter motor! Hence, when you are in heavy stop-start traffic, edging forwards a couple of feet at a time, you effectively have an electric car! It only restarts the engine when you get over one or two miles per hour, or if the battery is getting low, or if the cabin temperature gets high enough that the A/C has to turn on. I'm really pissed that some stupid outdated law prevents these kinds of intelligent fuel-saving ideas from being sold in the US market - even on cars that have all of the hardware to do it! SteveBaker (talk) 14:39, 19 May 2010 (UTC)

I see my error! Assuming that auto start-stop was a "luxury" feature, I checked the highest-end 7-series BMW, which does not have the option. Apparently auto start stop is only available on smaller BMWs - 1- through 3-series. Nimur (talk) 21:15, 19 May 2010 (UTC)

From occasionally driving and often being driven in a 2-3 year old 3-series BMW, I can, with very very very high certainty, state that at least the German model does indeed completely switch of the engine automatically when idling. It also switches off fuel injection completely if the car is engine-braking. --Stephan Schulz (talk) 18:45, 19 May 2010 (UTC)

The no-fuel-injection-during-engine-braking thing is a pretty common and well-established feature on cars with electronic fuel injection. My 1994 Civic did it, and I don't think it was particularly novel at that time. -- Coneslayer (talk) 19:58, 19 May 2010 (UTC)

How much does a starter typically cost? And how many starts does it take to wear one out? Thanks.--221.120.250.69 (talk) 18:52, 21 May 2010 (UTC)

http://www.google.co.uk/products?hl=en&q=starter%20motor&um=1&ie=UTF-8&sa=N&tab=wf

~£100 / $150

lifespan is long - starter motors are (I think) DC motors - so eventually the brushes may wear out or need replacing. I would guess the clutch or the contacts that turn it on/off would fail first.77.86.62.107 (talk) 19:03, 21 May 2010 (UTC)

My old auto shop teacher said, as a general rule, one minute of gas would be used by starting up the car. But you really have to take this with some salt, because it depends entirely on the car in question; obviously a big-arse Cadillac with a V8 is going to be different than a Yugo is going to be different than an Aston Martin is going to be different from a van, and the model year has a lot to do with it on account of increasing efficiency. And the temperature of the engine, temperature of the day, all that junk has to be taken into account as well. ZigSaw 12:25, 24 May 2010 (UTC)

Nuclear fuel

I read that Iran is swapping enriched uranium for nuclear fuel. What is the difference basically?--Mudupie (talk) 11:00, 19 May 2010 (UTC)

Enriched uranium discusses this at length, with diagrams to match. Regards, --—Cyclonenim | Chat  11:06, 19 May 2010 (UTC)

It's the level of enrichment—or, rather, the proportion of the isotope U-235 to the isotope U-238. Basically Iran is giving away a large storage of low enriched (3-5%) nuclear fuel, in return for a small amount of (ideally carefully controlled) fuel that is enriched to 20%, which is considered "highly enriched" even though it is not "bomb grade". The enrichment level determines in part what you can do with the fuel. 20% enriched fuel can run different types of reactors than 3-5% enriched fuel. In this case, I believe they want the 20% fuel to run a reactor that will make medical isotopes. (This is not a bad thing, in and of itself. Medical isotopes are good things.)

The reason for all of this is that ideally people don't want Iran to be able to enrich fuel to 20% on their own. The reason is not that 20% fuel can do anything interesting from a weapons point of view (it can't), but because the difference between 5% to 20% enrichment is actually a LOT larger than the difference between 20% and 90% enrichment. (This is, as first glance, counterintuitive—why should 5 to 20 be more than 20 to 90?—but it is because enrichment is exponential, to put it simply. This post goes into more detail as to why this is the case.) 90% enrichment is bomb-grade. So the goal here is to keep Iran from enriching their own material to 20%, because if they do that, they'll basically know how to make bomb-grade uranium. Giving them the 20% by itself is not necessarily dangerous, if it is monitored (so that it is not more enriched) and if they don't know how to enrich up to 20% on their own. Getting Iran to give away their existing stock ideally puts a limit on how much more enrichment they can do to it, and depletes the total number of bombs they could make if they enriched all of that fuel.

Note that there are some pretty obvious plans with the deal. Iran still intends to learn how to enrich its uranium to 20% anyway, and has kept enough low-enriched fuel that, if they did enrich it to 90%, they could have a bomb's worth of uranium. The U.S. analysts have largely viewed this as a "stalling" measure on Iran's part—to "give" a little bit so that sanctions don't kick in, while they work on their enrichment ability all the while. --Mr.98 (talk) 15:49, 19 May 2010 (UTC)

If you really believe that they want 20% enriched uranium to make "medical isotopes", then you must have your head under about two meters of sand. The thing is, 20% enriched uranium can actually do some interesting things from a weapons point of view without needing further enrichment -- if you stick it into a breeder reactor along with a lot of depleted uranium, then you can make "medical isotopes" indeed... 67.170.215.166 (talk) 00:15, 20 May 2010 (UTC)

Dirty bomb? --Chemicalinterest (talk) 11:12, 20 May 2010 (UTC)

That requires additional processing facilities and know-how that they likely don't have (nobody is alleging they have plutonium facilities), and the 20% they'd get from Turkey/Brazil would be heavily safeguarded anyway. I don't think there's any danger there other than them stalling. The risk of dirty bombs is exaggerated and certainly not what they are going after here. They do want the medical isotopes, in part because they want to be able to claim they've been doing civilian work on this all along. Their strategy from the beginning is to slowly get the infrastructure necessary to build multiple weapons if they wanted them. They wouldn't take the 20%, break safeguards, turn it into plutonium, and then try to turn that into a single weapon (if you could even get that out of 120kg of 20% fuel—the amount of plutonium produced even in a breeder reactor is small relative to the whole of the fuel mass, but I don't know the exact numbers). That would be the dumb approach. The smart approach would be to take the 20%, turn it into medical isotopes, show everybody how peaceful they are, drag out the UN process, continue developing U-235 enrichment capacity, divert other LEU into that, and get to the point where they could develop, say, a warhead a month if they wanted to. Then they have stealth nuke capability (like Israel), but have not yet violated the NPT in an explicit way, thus avoid sanctions, possibility of war, etc. Which is just a way of saying, one need not be blinkered about Iranian intentions to think that the 20% stuff is not going to be a military problem (it won't be). --Mr.98 (talk) 14:39, 20 May 2010 (UTC)

Also bear in mind that even "legit" medical isotopes (Sr-90, Tc-99, I-131, etc.) can, if produced in sufficient quantity, be used in a dirty bomb. You don't need plutonium for one of those things -- and if you're making plutonium, it makes much more sense to use it in a real nuke. BTW, regarding plutonium manufacture, Iran has actually been building a breeder reactor near Isfahan (and another one in Natanz near the main enrichment plant, so I've heard); I don't know if that thing is ready for use, though (they've had big delays with getting parts from Russia). FWiW 67.170.215.166 (talk) 04:35, 22 May 2010 (UTC)

Dirty bombs are, again, over-hyped, which basically every expert agrees on. Iran is not going to leave the NPT for a dirty bomb. A dirty bomb is not a sufficient deterrent, in any case. Again, the problem here is not about Iran taking this 20% material and doing bad things with it, the problem is that this is a move meant to derail other efforts to get Iran's stuff under control, and the more time they waste on that, the further they can get ahead in their domestic program. They've shown zero interest in any kind of short-term bomb; they want an independent production capability, if anything. --Mr.98 (talk) 21:30, 23 May 2010 (UTC)

Thank you for the explanation. --Mudupie (talk) 11:13, 20 May 2010 (UTC)

Reverse of hydraulic diameter?

While modelling fluid flows often the hydraulic diameter concept is used to model a non-circular duct as a circular one. I need to model a circular pipe as an equivalent rectangular one. So 1)Can this be done? (2)If so will it be modelled only as a square or can it be modelled as a rectangular section with any width to height ratio I choose? (3)Is this done in simply a reverse manner to how the hydraulic dia is calculated or is there some other technique (or does it depend very much on my fluid flow process and cannot be generalized)? Thanks —Preceding unsigned comment added by 125.17.148.2 (talk) 12:34, 19 May 2010 (UTC)

What exactly are you modeling? In general, you can model anything as anything - you can model your pipe as a spherical cow if you like. The question really is, "what parameters and results will you derive from your model," and as a followup, "what errors are introduced by your modeling assumptions/simplifications?" For example, if you intend to solve your flow with a FDTD solver and derive a fluid-flow rate for the pipe, your effective pipe shape will dramatically affect the resulting flow-rate. But if your procedure approximates the rate by simply calculating a cross-sectional area, the actual shape is irrelevant. So - what parameters do you hope to derive from your model? Once we know those, we can help direct you towards estimating the errors that result from your modeling approximation. Nimur (talk) 13:32, 19 May 2010 (UTC)

I am modelling the pressure loss in a cyclone separator. I have a correlation which is based on the entry duct being rectangular whereas my actual duct is circular. the pressure drop is dependant (at least according to the relation) mainly on the width of the rectangular entry duct and only to a smaller extent on height. so how do i change my circular duct to an equivalent rectangular one? If i know that the ideal/ general width to height ratio is 1:3 can i form that equiv rectangle? or since the model is dependent on a particular dimension (width) rather than area i cannot model it at all? Thanks once again. —Preceding unsigned comment added by 122.172.10.93 (talk) 16:31, 19 May 2010 (UTC)

If it is the pressure loss in the cyclone separator it self and not the pipe I don't think there are any generic translation. This depends on the mixing of fluids with different velocities at different radius in the cyclone. You will need a empiric formula CFD-simulation or very complex calculations. As an approximation I would guess between the pressure loss for a square with the same side as the diameter and a square with the same diagonal as the pipe diameter. —Preceding unsigned comment added by Gr8xoz (talk • contribs) 22:08, 19 May 2010 (UTC)

engineering

What is the scope of jobs if i do electronics in engineering<BE>?? —Preceding unsigned comment added by Swet69kak (talk • contribs) 13:21, 19 May 2010 (UTC)

Electrical engineering is huge. I mean, really huge. If you obtain an undergraduate degree in electronics engineering, you may be qualified to work in semiconductor manufacturing, MEMS, analog circuit design, digital electronics, computer architecture, system integration, firmware programming, software engineering, image processing, information theory, telecommunications, radio science, energy, and more. Have you looked at our article, electrical engineering? Nimur (talk) 13:26, 19 May 2010 (UTC)

Electronic engineering is really huge. Sometimes confused with Electrical eng —Preceding unsigned comment added by 79.76.203.64 (talk) 18:49, 19 May 2010 (UTC)

Note that this vocabulary distinction differs by region. In the US, at least, electronics engineers often have a degree in "electrical engineering", though they have extensive training in electronics. Comet Tuttle (talk) 23:00, 19 May 2010 (UTC)

The great thing about doing a BE is that it teaches you to think like an engineer. In any real job, you rapidly find yourself applying the thinking skills to information that goes into greater depth than you learnt in your course. After a while, it becomes possible to apply that process effectively to fields that didn't feature in the course at all (I can point to Electronic Engineering graduates who, 20 years on, spend most of their day doing Aeronautical, Marine, Automotive and Hydraulic engineering mixed with project management).

Proving you can cope with the academic rigour of a BE course also makes you attractive to all sorts of non-engineering employers (accountancy firms always used to like employing recent engineering graduates). Zeusfaber (talk) 19:27, 19 May 2010 (UTC)

moist towelettes

I watched the movie "The Book of Eli" back when it was playing and one thing that was a big trade item were moist towelettes, like the kind you use to clean your hands at a BBQ restaurant. I was wondering if those are a reasonable substitute for bathing in situations where a shower might not be available, like on a camping trip? I mean will one packet significantly reduce the BO, or would they need so many of the things that it would be inconvenient to haul dozens of them around? Googlemeister (talk) 13:38, 19 May 2010 (UTC)

The towelettes really vary in terms of the amount of liquid in them and they also gradually dry out over several months/years - even "sealed" as they are. I don't think they'd reasonably be useful for reducing BO, though; there's just too much "you" and not enough moisture in the packets to cover it all. Using one under each arm and one around the face/neck and one around the crotch might take some of the edge off, but after you've been sweating and in camp smoke for a few days, the stank (to use the technical term) is basically all over you - even your hair. Matt Deres (talk) 14:44, 19 May 2010 (UTC)

Exactly. And remember one of the opening scenes, where Eli says the good thing about no showers is that "You can smell hijackers a mile away", right before he's ambushed by the very same. Still, I think moist towelettes were a comfort item in that film, to, like Matt says, 'take the edge' off. Similar to the shampoo that Gary Oldman's character gave to his wife. Vranak (talk) 20:24, 19 May 2010 (UTC)

You'd be better off finding a stream or pond to wash off with (not necessarily in, mind you). In dryer climates, just rubbing sand on you can help clean off the sweat & grime, though it won't do quite so much for the smell. — The Hand That Feeds You:^Bite 15:28, 19 May 2010 (UTC)

You can always use a shower in a can to cover up the smell. 131.111.30.21 (talk) 17:23, 19 May 2010 (UTC)

Look in the baby aisle of your local supermarket - they'll have packets of moist wipes used for cleaning pooh off of babies rear-ends. That stuff is antibacterial so it should handle BO - and you get like 100 of them in a small container without a gazillion foil wrappers to lug around. SteveBaker (talk) 14:49, 20 May 2010 (UTC)

Beans growing on Crete

Does anyone know the name of the beans which grow on Crete and are used in locally produced "Coca-Cola" look a like called Fimi, these beans are also used by Nestlé. I forgot what they were called... I saw them growing in the wild in Crete... Sεrvιεи | T@lk page 16:54, 19 May 2010 (UTC)

Carob? Ghmyrtle (talk) 17:05, 19 May 2010 (UTC)

Still used, rusty aquaduct pipe lying in creek

At the tail end of a lake, the water rushes through a waterfall before continuing down a creek into the massive city-used reservoir eight miles away. Lying on top of some of this creek is a rusty pipe that is "picking up" some of the water and acting as an aquaduct to take it elsewhere (not sure where). The pipe is just resting on the surface of the creek; it's kind of gross. Are there any potential environmental or health concerns from this pipe touching future-drinking water? The pipe is slightly orange-ish in hue, with spots and discolorations on it. – Kerαunoςcopia^◁_galaxies 19:40, 19 May 2010 (UTC)

Almost certainly not - the orange patches are certainly rust - and iron is not a harmful element.77.86.10.27 (talk) 20:31, 19 May 2010 (UTC)

Even after it's oxidized? Is the amount of iron controlled at some point then? – Kerαunoςcopia^◁_galaxies 20:52, 19 May 2010 (UTC)

Rust is fairly insoluble in normal water, so it stays stuck to the pipe. If it goes into a water supply for humans it may be filtered to remove flakes and other gunk. Graeme Bartlett (talk) 21:16, 19 May 2010 (UTC)

Rust isn't harmful; it is a natural occurrent in the earth's crust. See hematite, the natural form of rust. --Chemicalinterest (talk) 21:33, 19 May 2010 (UTC)

Well, you can have too much of a good thing. I wouldn't expect the concentration of iron in the water coming off the pipe to be remotely high enough to be harmful, though. --Tango (talk) 21:46, 19 May 2010 (UTC)

If you are really concerned contact your local water authority or enviromental health agency (whatever they are called in your country) - better safe than sorry. The fact that a pipe links a water course to somewhere else raises the possibility of pollution by 'bad water' running in the opposite direction. In general though a rusty pipe in a water resovoir is not going to be a big problem.77.86.108.78 (talk) 11:03, 20 May 2010 (UTC)

Botfly

What actually happens if a human carries a botfly to full term in their flesh? Is there actually any lasting damage or health implications? No, not asking for medical advice here - I don't have botfly, nor does anyone I know. Just simple curiosity. --Kurt Shaped Box (talk) 20:21, 19 May 2010 (UTC)

Extracted human botfly larva. The arrow points to the larva's mouthparts

Dermatobia hominis captures a mosquito and lays an egg on it. Then when it feeds on a human the egg is transferred and a larva starts to develop (pictured) by feeding on flesh. Once it reaches full term it forces its way back out through the skin, falls to the ground and pupates. There was a great BBC Nature documentary showing it happen to a cow but I can't remember which it was. Searching the literature, the only problem caused seems to be myiasis (the larva feeding on your flesh). Adding "complication" to a search only comes up saying that it does not normally cause any complications. The danger comes if somebody attempts to remove the larvae and does a bad job, if the gut contents are spilled into your blood you could end up with a nasty infection (but having looked I can't find any recorded cases of what type of infection). So basically, like a good parasite should (to try and keep plenty of its hosts alive), it doesn't seem to cause any lasting damage. I spent the summer with some tropical biologists and heard a story of a professor who became so used to having the larvae that he no longer cared, once when at a football game, the larva decided it was time to leave, he took of his cap and out popped the grub, much to the disgust of those around him! That should probably be taken with a pinch of salt but I think it makes it clear that while being disgusting, they don't do any harm. 86.7.19.159 (talk) 21:45, 19 May 2010 (UTC)

Cracked disagrees. The bottom of this article says they can eat your brain. Of course, that problem wouldn't specifically be related to carrying it full-term... Vimescarrot (talk) 05:58, 20 May 2010 (UTC)

Hmm, that doesn't look like the most reliable source in the world. It also says that bullet ants "shriek" before they bite, but through personal experience I know that's not the case. It also has a picture of driver ants when its talking about the army ant, Eciton burchellii. Obviously if the mosquito happens to bite you in an important place then losing that bit of your body might be annoying - how exactly is the larva supposed to get through the skull though? —Preceding unsigned comment added by 86.7.19.159 (talk) 07:59, 20 May 2010 (UTC)

Certainly not a reliable source itself, but Cracked usually references some other source within its articles (I can't see it from here, it's blocked on this network). I think the idea was that to get to the brain it would simply float aruond the body (through blood vessels? I don't really remember) until it found somewhere it liked, then it'd settle down for a feast. 212.219.39.146 (talk) 08:02, 20 May 2010 (UTC)

That wouldn't work as they develop in the subcutaneous layers of the skin and don't enter the bloodstream. There are no sources in the article at all. _{To make things worse, they even stole the driver ant picture off this guy breaking the GFDL.} 131.111.30.21 (talk) 13:46, 20 May 2010 (UTC)

Through your ears? According to Myiasis#Clinical_presentation_in_humans, at least. Though this doesn't seem to be specifically referring to botflies. --Kurt Shaped Box (talk) 15:56, 20 May 2010 (UTC)

This article in Time discusses someone getting infected in their ear but it doesn't sound like they would be able to get into the brain through there. It seems more likely that the image in Cracked is of a Screw-worm fly - they can travel through the blood "Unlike the botfly, these larvae can enter the bloodstream and travel to distant sites such as the brain, lungs, heart, maxillary sinuses, inner ear, and even bone. If they remain localized, they feast on the host's tissues and can produce deep disfiguring wounds". That really wasn't a very good article! 131.111.30.21 (talk) 16:39, 22 May 2010 (UTC)

That quote came from this by the way there's no abstract available but if you search for "botfly brain ear" in google scholar it's the first hit. 131.111.30.21 (talk) 16:42, 22 May 2010 (UTC)

Evolution of movable eyeball

I know how the eyeball evolved, as per the WP article, but I can't think of an path for the eyeball to detach itself from the flesh around it, so that it can be moved. Is there there some speculative ideas on this? A google search [4] turns up a few hits, mainly from creationists questioning this. CS Miller (talk) 20:49, 19 May 2010 (UTC)

I have no idea how it actually happened, but it doesn't seem too difficult to me. Even a small amount of movement is beneficial, so it could start with an attached eyeball with a little flexibility and an appropriate muscle and gradually get less and less attached and more and more precise muscles until you reach the current state. --Tango (talk) 21:37, 19 May 2010 (UTC)

The most useful approach would probably be to compare the lamprey and hagfish, considered the two types of vertebrates with the most primitive body plans by most biologists. Lampreys have large movable eyes, but hagfish have lensless eyes with no exterior eye muscles. Looie496 (talk) 21:53, 19 May 2010 (UTC)

I've searched for some articles but it doesn't seem to have been discussed in any journals from what I can tell. This is because it is bound to be speculative and would be difficult to test so can't really be published in a journal. Tango's answer sounds very plausible, remember the amounts of time that evolution has to play with (unless you are an young earth creationist) and would be able to make infinite numbers of adjustments that would be either neutral or an improvement on previous eyes. Because eyes are so important, the selective pressure to improve would be strong. The creationist argument of irreducible complexity is pretty poor, this, the first hit in your link says that even the first eyes were complicated but ignores the fact that the simplest eyes would never have been fossilised! That also says "The fascinating thing about the evolution of the eye is its apparent sudden appearance" - this needs to be thought of on a geological time scale though - there have been huge changes to live today in the last few million years. There does not appear to be a convincing exact mechanism to show how the movement of the eye evolved, but remember that absence of evidence is not evidence of absence. The previous link ends with "For non-evolutionists there is no debate" - this is absolutely useless! You can't say that a theory is wrong without providing some alternative, more plausible explanation. Sorry for the rant - sounds like we're not really sure about it. 86.7.19.159 (talk) 22:10, 19 May 2010 (UTC)

It's of note that the eyeball is not totally detached by any definition. It is receded and has muscles that allow it to be pointed in different ways, but it still very much connected to the flesh. Receding into flesh would seem to make sense from a protection point of view; muscles to manipulate its location would also make sense. One can easily see how "half" of this capability would still be useful (humans only have "half" of the capability of, say, a chameleon), so that throws irreducible complexity out of the window (it is not an "all or nothing" type of thing). --Mr.98 (talk) 22:21, 19 May 2010 (UTC)

• I was under the impression that to get to the the the pin-hole state the retina evolved into the flesh, rather that the folds evolved outwards. It's the path from a lens-covered pit to a muscle-attached organ that I'm after.
• If the pit already had a lens before the sphere was moveable, then pointing the lens only at the object of interest is likely to reduce focusing accuracy.
• I can see that if the eyeball was on a stalk (a bit like snails'), then moving it into the body would be an advantage.
• 86.7--- / Mr98 - I'm not invoking argumentum ad ignorantiam, I'm trying to dispel my ignorance. CS Miller (talk) 22:58, 19 May 2010 (UTC)

The eyeball is still a lens-covered pit, isn't it? It's just a lens-covered pit that's also somewhat free to move from the surrounding flesh. I agree it's probably useless for the lens to be moved alone. The whole apparatus has to be moved together, which is why it might become somewhat less attached to the surrounding flesh. If you're thinking that the lens developed into the whole eyeball and the pit developed into the eye-socket that doesn't seem to make sense to me, although I'm just speculating. Rckrone (talk) 23:56, 19 May 2010 (UTC)

No, it is not necessary for the whole apparatus to move together. Salticidae have developed eyes where the lens is immobile but the retina moves. Of course Salticidae are arthropods, not chordates, and their eyes are not homologous to the eyes of the chordates. But no, the whole apparatus does not have to be moved together. Lampreys (already mentioned by Looie) indeed have an eyeball that is moved by extraocular muscles. (To be fair, lampreys have 5 extraocular muscles while most craniates -- from fish to mammals -- have 6; also, in contrast to most craniates, lamprey eyes are also focused by the extraocular muscles; AFAIK lampreys lack ciliary muscles in their eyes). This may suggest that lamprey eyes are indeed the most primitive "proper" craniate eyes extant. (Hagfish, on the other hand, is something of an enigma; either their eyes are the basal chordate eyes, or they have lost the advanced eyes their ancestors possessed, as the hagfish ecological niche does not require vision. There are reviews on that subject in literature. I recommend "Evolution of the vertebrate eye..." by Lamb, Collin, and Pugh, Nature Reviews Neuroscience (2007) v.8 pp. 960-975). This brings us back to the original question, how did the eyeball of the craniates evolve from the "cup" eyes of our basal deuterostome ancestors. Indeed, one mechanism by which hagfish may have lost the advanced eyes is neoteny. Larval stage of a lamprey has primitive eyes much like the hagfish; it is only during the lamprey metamorphosis that the proper eyeballs develop. Following the lamprey metamorphosis gives us a pretty good idea of what the eyeball evolution may have looked like. What happens is (1) light sensitive layer balloons laterally, forming a vesicle, (2) surface ectoderm is modified to form a lens, and (3) the extraocular muscles are formed from the mesoderm and the neural crest. Hope this helps. --Dr Dima (talk) 22:14, 20 May 2010 (UTC)

Trichlor illegal?

Is trichlor outlawed? It says so in the sodium hydroxide article. Thanks.--Chemicalinterest (talk) 21:32, 19 May 2010 (UTC)

it means trichloroethane (not Trichloroisocyanuric acid) , I've corrected the article [5]. Yes CCl3CH3 is outlawed.77.86.10.27 (talk) 21:59, 19 May 2010 (UTC)

Thanks. --Chemicalinterest (talk) 22:35, 19 May 2010 (UTC)

I still have some! Will I be arrested? Dbfirs 07:26, 20 May 2010 (UTC)

I think that it outlawed its production and sale, not its use (like halons). Naughty. You aren't concerned about the environment.--Chemicalinterest (talk) 11:06, 20 May 2010 (UTC)

Only a very small quantity - too little to be worth destroying (if that's possible). It has a very attractive odour, but I avoid inhaling it. Dbfirs 11:15, 20 May 2010 (UTC)

Which one is it? --Chemicalinterest (talk) 12:21, 20 May 2010 (UTC)

the 1,1,1 form was the most common - I used to have some Carbon tetrachloride - it too had a lovely smell - like many halocarbons (most of which are now banned or very heavily controlled) - you could hand it in to the local enviromental agency if you want rid of it (as an individual I doubt they would charge) - but company's probably have to pay to get rid of the stuff.77.86.115.45 (talk) 12:29, 20 May 2010 (UTC)

Yes, 1,1,1 (Liquid Paper thinner). Dbfirs 23:09, 20 May 2010 (UTC)

Wow, haven't seen any of that for over 2 decades - I think they banned it in the UK long before 1996 and replaced it with water or something - kids at school were sniffing it, - apparently the hallucinations they experienced interfered with paying attention in class or something...77.86.115.45 (talk) 23:47, 20 May 2010 (UTC)

Don't smell carbon tet! Can give you liver cancer. --Trovatore (talk) 23:50, 20 May 2010 (UTC)

Yes, almost all these compounds are toxic - and I don't think any are available any more for that reason. Possibly Methyl bromide is still used for fumigating silos for lack of an alternative but is heavily controlled. Dichloromethane is still available as a 50/50 mixture with methanol as paint stripper (in the UK) - I think it (should be) only a matter of time before the sale of that is banned too.77.86.115.45 (talk) 00:00, 21 May 2010 (UTC)

Here in the USA, we're still allowed to use dichloromethane as an industrial degreasing solvent (OSHA rules require good ventilation and the mandatory wearing of protective gloves, though, and there are EPA rules limiting emissions). Our policy is based on limiting the amount of pollutant emissions, rather than blanket bans on entire classes of substances which cause more harm to the economy than our mitigation-based approach. 67.170.215.166 (talk) 05:33, 21 May 2010 (UTC)

Atomic mass unit

"A single atom of carbon-12 has a mass of 12 u exactly, by definition", according to Wikipedia's article on the atomic mass unit. Because electrons contribute slightly to the mass of an atom, the mass of the nucleus of a carbon-12 must be slightly less than 12u. But this would seemingly imply that protons and neutrons have a mass that's slightly less than 1u, but in fact they have a mass greater than 1u. So what's going on here? Is this a relativistic effect involving potential energy reducing mass, or what? 173.179.59.66 (talk) 22:46, 19 May 2010 (UTC)

Electrons generally wouldn't count in the mass number. The total mass of the electrons in an atom carbon-12 would be 0.003291 (approx.) u. --Chemicalinterest (talk) 22:58, 19 May 2010 (UTC)

Terminology clarification: mass number is just the number of protons and neutrons and is an integer. The original poster is talking about the atomic mass, the actual mass of an atom, typically measured in atomic mass units; and yes, this includes the electrons. --Anonymous, 04:02 UTC, May 21, 2010.

A free carbon atom weighs slightly less than 6 loose protons + 6 loose neutrons. See nuclear binding energy. CS Miller (talk) 23:05, 19 May 2010 (UTC)

What you are observing here is that the mass of the assembled nucleus is less than the sum of the masses of the constituent particles. There is a loss of mass! See Mass defect where it says When the nucleons are grouped together to form a nucleus, they lose a small amount of mass, i.e., there is mass defect. The lost mass has been converted to energy according to Einstein’s formula $E=mc^{2}$ to hold the nucleus together against the electrostatic forces trying to disperse the positively-charged protons.

One amu is defined to be one-twelfth of the mass of a carbon-12 atom. As a consequence of the mass defect, the mass of a free neutron or proton is greater than one amu.

The mass defect is different for different elements, and different isotopes of any element. For example, the mass of the hydrogen-6 isotope is not 6 amu as you might expect from the definition of amu, but 6.045. Less mass is lost per nucleon in assembling a hydrogen-6 atom than in assembling a carbon-12 atom, possibly because hydrogen only has one proton so only one electrostatically-charged particle in its nucleus.

The mass of an electron is only 1/1836 that of a proton so the mass of all the electrons in an atom is not significant in the mass of the atom. Dolphin (t) 02:39, 20 May 2010 (UTC)

Whenever a net energy input is needed to pry something apart into its constituent pieces, conservation of energy together with E=mc² implies that the mass of the bound system must be less than the sum of the masses of the parts. This also applies to electromagnetically bound objects like atoms and to gravitationally bound objects like planets. "The lost mass has been converted to energy [...] to hold the nucleus together against the electrostatic forces trying to disperse the positively-charged protons" is incorrect. You have the sign backwards. If you have to spend energy to force like-charged objects together against their mutual repulsion, the binding energy/mass is positive, not negative. The negative binding energy of nuclei comes from the nuclear force. Electromagnetism contributes a positive binding energy, but not enough to make the binding energy positive overall. -- BenRG (talk) 03:38, 20 May 2010 (UTC)