Hitler's lentils
Ursula Mittwoch, in her review of Feminism, Animals and Science: The Naming of the Shrew, makes the mistake of naming Hitler as a vegetarian (Review, 21 January). He was not, but followed a non-meat diet occasionally for medical reasons.
Wood-be fuel
Fred Pearce, discussing the cultivation of wood as a fuel for electricity generation (“Seeing the wood for the trees”, 14 January), fails to mention its most significant advantage. Most renewables, like the wind “which bloweth where it listeth” are unpredictable, but electricity from wood can be produced to order. A farmer’s crop can therefore be utilised to supply the more valuable demands of winter, rather than to compete with the much lower year-long average value.
As Pearce says, the best locations for wood-burning plants are in rural areas close to their fuel source. In fact, the very best place, involving zero transport, is at the farm, using mass-produced engines and generators, operated by the farmers themselves. One British example of this type of plant is generating electricity at Enniskillen in Northern Ireland.
Wood crops on surplus farmland are timely, not only to counter atmospheric CO2. They are well positioned to improve the health of the power market. The electricity regulator, Stephen Littlechild, is concerned about lack of competition for winter peak generating capacity where some additional competition, he says, would be particularly helpful. The generating capacity of 6000 megawatts, which he suggests would be sufficient to create significantly more competition, is, surprisingly, just about the capacity that farmers could contribute from wood cultivation on set-aside.
What’s wrong with introducing “hedges” of coppices into our so-called “prairie” fields? I should have thought these could then be more easily harvested whilst giving the added advantages of combating soil erosion, providing cover for wild flora and fauna, and, equally important in these uncertain times, leaving the “set-aside land” readily available for the job it may well have to do again 鈥� produce food.
Unlucky leaks
New 杏吧原创 has had many articles on mercury contamination in recent years. Rereading Gail Vines’ article “The mercury the physicists left behind” (1 December 1990) provokes me to comment on the ubiquitous mercurial blood pressure machines (sphygmomanometers).
Affectionately known by health professionals as “sphygmos”, these devices are in fact 70 grams of a classified hazardous substance in an unsealed container, without the appropriate warning label one expects on a boring old bottle of methylated spirits.
Among hundreds of nurses I’ve spoken to there’s agreement that sphygmos leak, raising the possibility of chronic poisoning of nurses. Sounds fanciful? Consider a report in Brisbane’s The Courier-Mail (July 3) which revealed that mercury vapour 1.7 times the actionable level (50 micrograms per cubic metre) was found in the breathing zone of a hospital patient. Small droplets of mercury in the tray holding the arm cuff at the base of a wall-mounted sphygmo were the source.
Nurses are in and out of this tray all day with their hands, apart from breathing in significant doses along with the patient. The National Health & Medical Research Council of Australia recommends a “no touch technique” for handling mercury. Nurses cannot meet this criterion due to the vented design of the noble sphygmo.
Arguments of superior accuracy with mercurial sphygmos are negated by leakage which must affect the meniscus level in the graduated glass tube. Next time your doctor wants to check your blood pressure, ask for an aneroid machine. You deserve a choice.
Power drain
The proposals made by F. Robb for electric vehicles (Letters, 7 January) could no doubt be implemented. However, before anything is done it is as well to ask the basic question 鈥� do electric vehicles reduce the emission of CO2 and other combustion products?
Leaving aside alternative power sources such as nuclear or other non-fossil fuels, a vehicle can only claim to have a comparatively “green” effect if it uses less fuel per unit of delivered traction power than other alternatives.
The energy that can be converted from primary fuel into electricity is 38 per cent on average for the British generating system. The power then has to be transmitted from the station to the electric motor in question. Over the British distribution network as a whole, a further 38 per cent of the power generated is lost before it reaches the point of use.
In the more densely populated areas, however, the distribution loss is lower than the national average. In view of this, a transmission loss of 30 per cent would be a reasonable estimate for zones where electric vehicles are most likely to be used.
For vehicles such as trolley buses or trams the final transmission stage is through overhead lines and a sliding contact. Losses at this contact vary as they are very sensitive to the condition of the exposed sliding surfaces. For inland areas, well away from corrosive salt air, a sliding contact loss of 5 per cent might be achievable. The electric motor is an efficient machine under constant running conditions but, even so, about 10 per cent of its electrical input is not converted into power at the output shaft.
From these figures, the basic overall energy conversion efficiency from primary fuel to road use for this type of electric vehicle is about 23 per cent. That is, somewhere below the efficiencies generally quoted for petrol engines (25 per cent) and diesel engines (35 per cent).
Battery-driven ones are even less efficient as, though the sliding contact loss is eliminated, battery charging and discharging efficiencies have to be considered. There are a number of alternative battery types under development, all slightly different in their efficiency characteristics but at present it seems unlikely that any battery will better 90 per cent in charge and discharge efficiencies. A basic thermal efficiency of about 19 per cent is therefore the best that can reasonably be expected from a battery-powered vehicle.
Window on past
Reading the article on plastic windows by Tim Thwaites (Technology, 7 January), I felt a strong attack of d茅j脿 vu; and indeed, after some rummaging in the dustier nooks of my bookshelves, I dug up edition 1901, of Das neue Universum, an almanac dedicated to the dissemination of knowledge about the latest advances in science and engineering into the minds of its adolescent readership.
Here it was: Luxfer-Prismen, the novel pane-and-prism system for better natural illumination of basement and ground-floor rooms. It seems to have been a bit more clumsy than its present-day successor, being made from mineral glass as a replacement for, not an adaptor to, existing window panes. Apart from that, there is a striking similarity; down to the fact that to achieve optimum lighting for a given room, the prisms would have to be custom-made.
However, I have never ever seen an actual application of the Luxfer-Prismen system. Hopefully, Edmonds/Cowling’s design will fare better, but there is one reason why it might not: Would you gladly accept the chore of cleaning the fissured surface? It could turn out to be the most effective dust and fly shit catcher that has ever been designed.
Jug runneth over
With reference to Ian Stewart’s interesting article on how to make two spheres out of one (“Paradox of the spheres”, 14 January), readers may be interested to know of a simpler method which, while perhaps lacking something of the elegance of the Banach-Tarski procedure, is quite satisfactory for home use.
Take a sphere composed of an infinite number of points and place it in a jug or other suitable container. Stir briskly to reduce it to a topologically fluid state, with no points left sticking together. Pour into a spherical wooden or plastic mould; tap the mould to ensure that no voids are left. The mould may now be carefully disassembled, leaving a sphere made up of an infinite number of points.
You have not emptied the jug, however, since the number of points it contained was infinite. You can now therefore pour another sphere, or a different shape if you wish, and the process can be repeated to make as many more shapes of equivalent volume as you are likely to need; indeed the limit is set not by what is left in the jug but by how long you are prepared to go on doing it.
A short letter will limit me to highlighting a single error in Stewart’s article, which was repeated twice.
We are told that the inhabitants of Xodarap, whose alphabet is literally an alphabet, as it contains only the letters A and B, have a dictionary containing an infinite number of words of finite length. This is impossible.
Assume that the longest word in the dictionary has a finite number of letters, n. It follows that the total number of words in the dictionary cannot exceed 3n which is also a finite number.
Ian Stewart writes: But there is no longest word in the dictionary. For example, it contains the words A, AA, AAA, AAAA, and so on. Each has finite length, but there are infinitely many of them. Michael Godin is assuming that the length of the words is bounded (they all have the same finite upper limit to their length), which is a stronger condition than each word alone being finite.
The “proof” that a sphere can be chopped up and reassembled to form two spheres the same size as the original is surely based on a fallacy. A sphere, or any other object, is not “made up of an infinite number of points” as the article suggests. A point, by definition, has zero volume and it does not matter how many are grouped together, the total volume is always the same: zero.
The volumes of spheres and other bodies are determined using calculus by assuming that the body shape can be approximated by a finite number of finite volume regions. The volume is then found to any desired accuracy by allowing the number of regions to tend to infinity whilst the volume of each region tends to zero. The calculation never relies on the number of regions actually becoming infinite nor on the size of the regions actually reaching zero. Banach and Tarski’s proof, on the other hand, depends crucially on the number of points within the sphere being infinite. As any physicist will tell you, infinites are bad news.
I cannot help thinking that Banach and Tarski’s proof is a variation on one of the well-known cod proofs that 1 = 2, 1 = 0, etc. These mathematical conjuring tricks usually rely on dividing by zero at some stage of the calculation. The attempt to divide a sphere into an infinite number of complex regions of zero volume would seem to be just such an exercise in sleight of hand, albeit a more elaborate one.
Ian Stewart writes: No, it’s not a fallacy. I agree that the volume of any single point is zero, but despite this a sphere is made up from an infinite number of points. It is not correct to add up all the volumes of all the points to get a total volume of zero. This is because 鈥� dare I open up a new can of worms? 鈥� there are different kinds of infinity. The number of points in a sphere is what is known as an “uncountable infinity”, meaning that the points cannot be matched one-to-one with the whole numbers 1, 2, 3 鈥� Volumes can be added up correctly for a countable infinity of pieces but not for an uncountable infinity.
Several readers decided that the source of the “paradox” must be some kind of fallacy, akin to arguments like 1 脳 0 = 2 脳 0 therefore 1 = 2. Sorry, no. Cancelling zeros is plain wrong, and no mathematician would countenance it. The overwhelming consensus among mathematicans is that the Banach-Tarski proof is right, although a few who espouse fringe or unorthodox philosophies of mathematical logic object to it. General point sets include “objects” whose behaviour is very far from that of the everyday shapes upon which much of our intuition about volume is based.
No religion here
Peter Rowland may be suffering from atheist’s paranoia when he asserts (Letters, 21 January) that the anthropic principle is “quasi religious”.
The starting conditions needed for the big bang to eventually produce the observable universe may have been highly unlikely. However, the fact that we are here to see it can be seen simply as evidence that the very unlikely can happen. There is no need to bring God, psychology or our own arrogance into the debate at all. The anthropic principle can sit quite happily within the non-mystic, scientific world of physics.
Though neither a parent nor a grandparent, I beg to differ from Rowland. He confuses the “anthropic principle” with an “anthropocentric principle”. Whatever the latter may be, the former simply holds that the existence of life in the forms found on Earth is one of the factors scientists must take into account.
Puzzle solved
You recently carried an account of research into the link between the HLA-B27 gene, spondyloarthropathy and gut bacteria (This Week, 17 December). The report suggests that the link remains a puzzle and that the development of a mouse strain carrying the HLA-B27 gene will permit further research to understand the link.
This is very puzzling. Alan Ebringer of King’s College London first described cross-reactivity between Klebsiella aerogenes and B27 lymphocyte antigens in ankylosing spondylitis as long ago as 1976 (in Dausset J, Svejgaard A, Eds. HLA and disease. Paris: INSERM, 1976).
Ebringer has continued this work, showing quite clearly that epitopes associated with HLA-B27 in the paraspinal tissue resemble epitopes on Klebsiella. Patients with ankylosing spondylitis have cross-reacting IgA in their blood. This work has been confirmed by several groups of workers.
Gentle wind
Re your item on the Seine Bridge’s ability to withstand winds (In Brief, 21 January). I hope there is a misprint here, since 120 kilometres per hour = 74.52 miles per hour.
During our recent weather there have been records of gusting to 90 miles per hour.
Not another Tacoma disaster in store, I hope.
The figure was correct. It does sound a bit worrying, doesn’t it? 鈥� Ed
Gooner skreshers!
May I refer all those interested in language that must be heard to be understood (Letters, 19 November and 14 January) to the works of Afferbeck Lauder, Australian “Professor of Strine Studies, University of Sinny”, and in particular to his guide to the language of London’s West End (Fraffly Well Spoken, Wolfe Publishing, 1968) in which are contained such nuggets as “Gooner skreshers! Hoss choop toffmeh!” and “Ah peck your poncer, but mairn tropp choofra, merment?”
Anyone interested in this form of writing may care to avail themselves of a volume entitled Mos D’Heures: Gousses, Rames by Luis D’Antin van Rooten (Angus & Robertson, 1967). This is a slim volume of 40 verses familiar to many anglophone children, but a deep mystery to francophones, even though a “translation” is provided. By way of example, the first verse begins:
Un petit d’un Petit
S’茅tonne aux Halles
Un petit d’un petit
Ah! degr茅s te fallent 鈥�
Thanks, Star Wars
The excellent article by Elizabeth Wilson explains how the development of adaptive optics and laser guide stars is bringing a new lease of life to Earth-based astronomical telescopes such as the Hooker Telescope on Mount Wilson (“New eyes for an ageing star”, 14 January).
The article, however, contains one error 鈥� of historical fact. Although the publication by Renaud Foy and Antoine Labeyrie was the first to appear in the open literature concerning the proposal to use lasers to create artificial guide stars for telescopes fitted with adaptive optics, the credit for this invention rightly belongs to Julius Feinleib. In 1981 Feinleib made the proposal as part of the classified work carried out under the Strategic Defense Initiative, as acknowledged by Dr R.Q. Fugate (director of the starfire optical range of the USAF Phillips Laboratory) in the letter to Nature (Vol 363, 1991) which first disclosed the work carried out on adaptive optics under SDI.
A prize for the invention of adaptive optics for astronomical telescopes was awarded to Horace Babcock by the Rank Prize Funds in London on 30 November 1993. At the same ceremony the prize for the invention of laser guide stars was awarded to Julius Feinleib.
Letters to the Editor
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Correction
Correction: The publicity material for schools mentioned in Forum (21 January) is produced by the Biomedical Research Education Trust, not the Research Defence Society as stated.
Brian drain
What is it that makes owners of the name Brian so attractive? I refer to your picture caption, “Brian magnetism”, in the article, “Maps of the mind” (7 January).
The most magnetic Brians are, of course, eligible to compete for the title “Brian of Britain”.
I'll scratch yours
I was interested to read in Gail Vines’s article “Get under your skin” (Inside Science, 14 January) that Terence Kealy suggests that the acne-producing mechanism is good at producing acne and appears to serve no other function. I tend to agree with him but would moot a different explanation than the suggested “marker of puberty”. How about social bonding through grooming?
In the higher primates especially, mutual grooming serves not only the requirement of physical health but also that of appeasement, deference, bonding and even pleasure. This last aspect can be obsered in chimpanzees by the fervid excitement when a particularly interesting blemish or parasite is detected.
Distasteful though it may be to some, there are those of our species who attack their own scabs or acne with similar enthusiasm and the phrase “don’t pick it” springs to mind and memory.
As with (other) animals, the action is not confined to one’s own body. Mothers sometimes insist on attacking their offspring’s spots, and lovers also engage in the act 鈥� sometimes even being distracted by it to the detriment of procreation.
It also agitates some individuals to be confronted by another with a visible inflamed pustule when constraints of social etiquette prevent action. Nor is the compulsion restricted to acne 鈥� a dirt mark on the face or spinach between the teeth will also elicit a reflex response.
The areas of the body most afflicted with acne are those which are either difficult to reach or cannot be seen by oneself, namely the back, buttocks and face. It would seem therefore that assistance would be required in their eradication. Since the advent of mirrors, self-spot depletion has become possible, but nature didn’t anticipate the invention. Nor of course is it now acceptable to strengthen social relationships by offering to examine buttock acne, but as in so many other cases we are left with the legacies of our progenitors.
Private scanner
So the National Academy of Sciences in the US has recommended to redesign the banknotes so that blind people can tell which is which (This Week, 21 January). They think of something like a bar code which can be read with a hand-held scanner.
Brilliant idea that! With a bit of luck they might even turn up a system which the Dutch have been using for many years, namely a pattern of embossed dots. Dutch blind people are able to read these with their own private hand-held scanner: their fingers.
Upside down
It is a pity none of your staff can read Hebrew or they would have realized that the photo of a scroll that you published was upside down (This Week, 14 January). Maybe it looks more aesthetic the way it is and probably would not have troubled the majority of people but remember that you do have scholars among your readers.