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John Cuthber

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Posts posted by John Cuthber


  1. Also, while it's hot make sure it doesn't oxidise in air and give zinc ozide and SO2.

     

    If you are trying to get something to glow in the dark then I think the big problem is that the real stuff is made in a rather complicated way to get the best performance.


  2. Interesting chain of logic. I asked precisely one question; it was this "Still, what other product can you think of which, when used in accordance with the manufacturers instructions, has a 50:50 chance of killing you?"

    It seems the answer is "There is a 100% chance that eating carrots will kill you. A survey made in 1900, showed that every one surveyed had at some time eaten a carrot or carrots. Almost all are now DEAD, and the couple still around really look bad, expected to die soon."

     

    BTW, are you sure about what you said. I'm quite happy to believe that they record incidence of tobacco use on death certificates. Are you sure that's the only way they decide that tobacco is the cause of death. I know the medical and legal professions can be idiots at times but that one seems to be a step too far. If it is then, since they don't do that in the rest of the world, the aparent risk from cigarettes in the USA would be practically 100% whereas it's different elsewhere. Surely that would becom a ludicrous anomaly.

    Practically everyone has tried smoking once. Does this mean that 100% of deaths in the USA are recorded as smoking related?


  3. Err, it's a fair point that the media exagerate things like it's going out of fashion, but since plutonium is roughly a million times more radioactive than uranium it's a reasonable candidate for this list. It has an LD 50 of about 50 µg/kg which is pretty low and it certainly got a mention early on in this thread.

    I think the problem with including it is that you would also need to include every radioisotope with an apropriate half life (too short and you will never get enough into someone to kill them; too long ant it won't do any harm).


  4. Careful addition of liquid oxygen to the fuel in a car could easily result in the car reaching the speed of sound. Unfortunately this will be in a multitude of directions simultaneously. Also, the driver wouldn't survive to claim any glory, in fact it might be difficult for his next of kin to find any bits of the driver big enough to claim for burial.


  5. IIRC the lifetime risk from smoking is about 50% ie half of smokers die from something related to it.

    Of course the lifetime risk from living is 100% - everyone dies. There's also the fact that even non-smokers die from things, like lung cancer, that are usually thought of as smoking related.

    Still, what other product can you think of which, when used in accordance with the manufacturers instructions, has a 50:50 chance of killing you?

     

    The fact that you don't smoke much now is pretty near irelevant. Nobody ever started off as an 80-a-day smoker.

    Like many people here, I think you should quit while you are still ahead of the game.


  6. SkepticLance,

    I think that's a fine method for determining whether or not something is self-aware, but it has a problem. All blind animals fail.

    Now, I'm not a great admirer of cats- as far as I'm concerened they just mess up my garden. I pointed out to some cat lover that cats are dumb- they don't even react to their reflection in a mirror.

    He pointed out that it could be because cats are smart- they know that the image doesn't smell like a cat so they know it's not real.

    Good luck applying the mirror test to an animal that generally lives in the dark and percieves its environment by echolocation.

     

    Also, re

    ""What Greenpeace should do is very clear and has been for years. Accosting whaling ships in the Southern Ocean does not work. If the leadership of Greenpeace is sincere, which I doubt, then they will work on the democratic process, since Japan is a democracy. They will set up an anti-whaling organisation within Japan, using the many conservation minded Japanese to run, and educate the Japanese people, in Japanese, about what is going on. "

     

    What, like this?

    http://www.greenpeace.or.jp/index_en_html

     

    Would you like to revisit your opinion of Greenpeace's sincerity?

     

    I think that it's quite sensible behaviour for them to continue the work that brought whaling under some sort of controll in the first place and to add on other strategies, like Japanese websites, too.

    I agree that the greenpeace boats out there with the whaling ships probably don't achieve a lot directly, but they provide vivid images that do a lot to raise awareness and raise funds.


  7. Oh, BTW, I think the same problems (eddy currents and demagnetisation) will happen with magnetic bearings. They still work so the idea is perfectly plausible, I'm just not sure how many applications you will find for it. The "gogging" effect ie the variation in torque will be horrible if you only use 4 teeth but I can't see a problem with using lots (OK that's like a conventional gear) but it's still non contact, so no friction and no wear.

    It would be interesting to see what the people who do "nano machines" think of this- they have real problems with friction.


  8. I don't see Blair as the type to read much so I guess it was down to Rushdie's support from the literary world (rightly or wrongly).

    (and I think most of the queen's grandchildren are a bit old for Harry potter but that assumes they havew normal reading abillity.)


  9. Why are ethics and philosophy not open to scientific explanation?

    In the limit they both happen in human brains; they are the results of a very complicated set of chemical reactions.

     

    As far as I know religion doesn't really answer anything anyway- saying "because God said so" isn't an answer unless you explain God.


  10. You could do it with very clean glass. Paint the image on with silicone oil then spray a fine mist of water onto it. The mist will stay as fine drops where the oil is but will spread out to a thin layer where the glass is clean.

    That way you can really use water in the spray.

    Otherwise you are basicly looking at the world of invisible inks and developers. I'm sure google will help you with that.


  11. Since nobody has specified the pressure in the helium ballon it is perfectly possible to have a helium balloon in a vacuum. You just need to be sure not to put much helium in it.

    BTW, I don't play baseball so I'm no expert but re. "at ground level look more like a baseball in the bottom of a condom". Wouldn't that be the wrong way up?


  12. There are real losses due to eddy currents.

    On the other hand the idea that the magnets"wear out" isn't a real problem.

    The worst position for a magnet to be in from the point of view of demagnetising force is next to another magnet N to N and S to S.

    Any combination of gears will sometimes be less strongly demagnetising than this.

    Think about an ordinary bar magnet- it is 2 magnets stuck together head to head and tail to tail. If you cut it carefully down the middle you get 2 magnets.

    Since ordinary magnets are stable for years there is evidence that these gears should work well.

    On the other hand, normal gears are fairly efficient anyway so, except in a few odd situations, it's probably not worth bothering.

    The thread's title is misleading. These are not really gears so the fact that you can't have gears without friction doesn't apply. "Something that isn't a gear does something that gears can't" isn't very eye catching.

     

    "you need to remember conversation of energy." There's nothing inconsistent with the conservation of energy with using magnetic forces to move things. A magnet has, by virtue of the field) some stored energy. For you to say this energy "goes away" is actually a breach of the conservation principle unless you can say where it goes.


  13. Joy,

    Do you understand that there is a difference between "poodles are dogs" and "dogs are poodles"?

     

    Similarly, there is a difference between "liquids that acts like a solid under pressure are non newtonian" and

    "non newtonian liquids acts like a solid under pressure ".

     

    Since the second of these is what you said, but the first of them is true I still think you were wrong.


  14. I agree that you should "think before you drink"; it's darned hard to think properly afterwards.

    Anyway, I used to brew my own and the best advice I can give is keep everything clean. (Also don't prime bottles with too much sugar)


  15. Well, you may say "That's assuming the building doesn't have a decent ventilation system... but ours does."

    But there seems to be some question of the adequacy of the ventillation.

    "After about an hour and a half, they let us back into the building, but they turned up the vacuum system in the building, so get the fumes out and to cycle the air, I guess. The problem, is that this changed the pressure significantly in our P2 lab (for dealing with hazardous pathogens), which set of an alarm. (sigh)."

     

    Anyway, no reasonable ventillation system can keep the methanol concentration above a large spill within safe limits.

     

    Ravio, before posting this

    "In my humble opinion such reaction to the methanol spill was surely an overkill. Not that this kind of spill does not need attention - it surely does - but funny thing is that university with all its educated minds is not able do deal with it and so much help from other institutions is needed. " Did it occur to you that those educated minds might have a better informed humble opinion than yours and that their reaction was not overkill?

     

    Just think what one static spark could have done in the right place at the right time. Then think what you would be saying if they hadn't decided to clear the building and get the clean-up squad.

    Would you be saying "Well, we lost the building and a few people but since it was only a methanol spill that's OK"?


  16. If you need to ask that sort of question please don't try working with phosphorus (red or white).

    The reactions are rather complex but they can be summed up as the glycerine get's oxidised by the permanganate. This reaction generates heat and the hotter the mixture gets the faster it reacts. The temperature rises rapidly until the material catches fire.


  17. Yeah, It's just methanol. Roughly as flammable as gasoline. Burns with a near invisible flame so it's possible to walk into a methanol fire before you see it.

    It's got an idlh value of about 8 g /metre cubed so 4 liters ie 3.2Kg is enough to make 400 cubic metres of air unbreathable.

    Hey, why tell anyone to get out of the building?

     

    It is noted for its ability to be absorbed through the skin but that's no reason for the delivery bloke to remove any contaminated clothing. It sends you blind at doses less than it takes to kill you but if it's a choice between that or flashing next week's washing at passers by then hey, who wants their underwear on display.

    Get 6 % or so of it into the air and then you can light it too. This stuff is used to power racing cars but that's no reason to worry about it exploding in the building is it?

     

    Seriously, as far as I can see the only things that went wrong during that event were that the stuff should have been packed better and someone should have tripped the fire alarm to get everyone out. I would ask why you didn't set the alarm off ecoli, but I know that when I had an incident with a leaking hydrogen cylinder I didn't sound the alarm. People don't always think straight in emergencies.

    At the end of the day nobody was hurt, the emergency services might have had their day livened up a bit and your experiment went West.

    As you said,

    "Or maybe the problem is that scientists just like to complain about everything... especially when it comes down to criticizing their university amoungst themselves. "


  18. Since AgSCN is practically insoluble you can't really do a titration with it.

    You can use it as part of an indicator system (in the presence of Fe).

     

    Titrating with HCl then trying to measure Cl would be ill advised- it's much easier not to add lots of the stuff you are trying to measure.

     

    There's nothing to stop you doing the titration with HNO3 to as exact an end point as you can get for the determination of the base then adding excess acid and titrating with AgNO3 to measure the chloride, again to as good an end point as you can get.

    Warming the solution isn't going to help a lot either.


  19. Since many elements show multiple oxidation states the table is ambiguous. If it's meant to me highest oxidation states then copper is wrong; if it's meant to be most common then iron is wrong. If the asignment is arbitrary then it's all wrong.

    It also fails to convey any information about the underlying reason for the periodic nature. It springs from the arangement of the electrons in what for simplicity's sake are usually called shells.

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