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Thursday, 26 August 2010


Having a picture framed is an expensive business - if the frame is going round a print it can cost three or four times as much as the print itself. And even if the frame is for an original painting it can cost a significant fraction of what the painting cost (unless you are the sort of person who needs to re-frame a Caravaggio).

It's also a difficult job to do yourself. Even the most careful amateur carpenter can have trouble mitering the corner of the moulding to get a perfect 45o cut.

My father was a painter, and he would frame his own pictures for sale. The machine on the right used to live in our kitchen when I was a child. It is a Morsø mitering machine, and it makes the cutting of a perfect 45o miter easy; anyone can get a good result with one of these. It guillotines the moulding to form two mitres simultaneously.

But it obviously makes no sense for everyone to have such a machine for themselves for use on the one occasion every two years when they want to frame a picture.

There are many products that are designed to break once cleanly. Think of the perforations around postage stamps, or of the ring pull on a Coke can. Why not make picture frame mouldings that have a series of 45o indentations along the back every few millimeters designed to snap cleanly? The indentations would have to be symmetrical about the middle of a length of moulding with -45o to the left and +45o to the right. You could then buy two lengths a little too long for the width of your picture, and another two a little too long for the height, and make your own frame of any size you liked.

It ought to be possible to do the design with added clips that would fit into the remaining indentations to hold the corners together, so you wouldn't even have to use a hammer and nails.

Wednesday, 18 August 2010


Deaths of passengers from airline terrorism are, of course, fabulously rare. The worst decade was the 1980s, when about 150 passengers per year were being killed. The figure has fallen steadily since then, and is now around the same level as it was in the 1960s - about 40 deaths per year.

Today there are many more flights than there were in the 1960s, so the relative figures are even better than those numbers imply. The reduction in deaths is due to a combination of factors, the two principal ones being better airline security and the general fact that terrorism - airline and otherwise - is much rarer now than it was.

The world's airlines fly about two billion passengers each year. If each passenger spends an extra three-quarters of an hour getting through airport security over what they would have spent in the 1960s, then 2,300 human lifetimes are taken up in airport security per year.

So airport security takes about sixty times more human lives than the threat that it protects against...

Thursday, 12 August 2010


Loctite Blue glue is remarkable stuff. In the presence of oxygen it is a liquid, and it only sets hard when oxygen is excluded. This means that when you put it on a bolt thread it is easy to screw the bolt onto its nut. But once the bolt is tight (which excludes the oxygen) the glue locks up, preventing the thread coming undone.

Even cleverer, the reaction is reversible. Thus, when you loosen the thread a bit with a spanner, the ingress of the air releases the bond, and the bolt can easily be undone the rest of the way. Rather neatly, the bottle in which the glue is sold is permeable to oxygen, so the glue stays easy to pour.

There are often photochemical reactions that are equivalent to this type of reversible bonding. So how about a glue that sets solid in the dark and is liquid in the light?

You would paint it on a surface, where it would stay happily liquid (well, it would till dusk...). But when you put down the other surface to be stuck on top of it, the glue would instantly set solid as the shadow fell, holding both fast.

If one of the two items to be stuck were translucent, but covered (except for the sticking surface) in an opaque paint, the glue would still work. But you could release it simply by opening a window in the opaque paint. It would be possible to set up all sorts of complicated simultaneous sticking and release mechanisms that were worked by allowing light in and excluding it.

It might even be possible to have the material respond to different wavelengths if the no-stick chemistry were only triggered by photons of a specific energy. Different coloured lights could then be used to release different bonds.

You could also have an electric release mechanism: simply bury LEDs in one of the surfaces...

Thursday, 5 August 2010


Tobacco, notoriously, is not very good for you. Consequently there is an ongoing battle between the people who sell it and - more-or-less - the rest of the human race. The former want to push more cigarettes; the latter want to stay alive. The battle is quite instructive in a game-theoretic way. In particular, the sellers carefully manipulate the level of the addictive component (nicotine) to maximize the number of cigarettes that they sell.

When there is a large number of smokers, it makes sense for the tobacco companies to reduce the nicotine level; that way they sell more (and so make more money) as people have to buy more to get the level of nicotine in their blood up. But as the number of people smoking drops, the companies raise the nicotine level in order to create more addicts among people (particularly teenagers) who only try two or three cigarettes. The reduction in the number of smokers in recent years (at least in the developed world) is the reason that the companies have been cynically upping the dose. (See, for example, this article in The Washington Post.)

Those on the other side who are concerned with keeping us all alive deprecate this, and advocate controls on the maximum nicotine levels allowed. Jack Henningfield and Neal Benowitz in a British Medical Journal editorial, say: "Possible strategies to be overseen by the Food and Drug Administration could include ... restrictions on the amount of nicotine in tobacco products..."

A single cigarette contains about 10 mg of nicotine. It is one of the more poisonous substances known - about 60 mg will kill a non-smoker and about double that will kill a smoker. It is a particularly effective insecticide, which is why tobacco plants have evolved a metabolic pathway to make it, of course. But nicotine is one of the less harmful ingredients in tobacco. The things in there that really kill people are the tars, benzene, formaldehyde, and so on in the smoke, and the carbon monoxide that is consequent on the combustion that creates it.

So it may well be that restricting nicotine levels in cigarettes is the wrong way to go. The authorities should require them to have a minimum nicotine level. That level would be set so high that non-smokers starting would immediately throw up, thus putting them off, and so that smokers would only need to smoke one cigarette a day to get their dose, thus much reducing their exposure to all the substances that really harm them.