Letters: Bronze Age past
Numismatists have known about our new ‘magnetic’ bronze coins for some
time, as they are listed in current coin catalogues. But anybody who uses
vending machines cannot have failed to have noticed the nonuniformity in
the thicknesses and masses of the new shrunken 5p and 10p coins. What has
brought about this recent debasement in the Royal Mint’s standards?
Something else that puzzles me is why the geometrically congruent, and
chemically identical, 20p and 50p were not designed to exhibit direct weight-value
proportionality. In the pre-decimal coinage 拢1-worth of silver weighed
4 ounces whether it consisted of 4 crowns, 8 half-crowns, 10 florins, 20
shillings, 40 sixpences or 80 silver threepenny bits.
Stephen Clackson Aberystwyth, Wales
Letters: Hot choc shock
Perhaps some reader can explain a phenomenon I recently discovered while
in a mundane domestic environment.
I made a cup of hot chocolate, using partly skimmed milk and a brand
name chocolate drink powder. I stirred it up using your average teaspoon
– the cup was your average coffee mug. Keeping the spoon in the liquid and
tapping it against the sides or bottom immediately after stirring produced
a relatively low-pitched sound whose frequency increased (almost inexorably
it seemed) with time. The form of the stirring made no difference – rotation
or just general turbulence produced the same effect.
I could not reproduce the phenomenon in hot or cold water, hot or cold
milk or cold ‘hot’ chocolate, but hot chocolate in a different kind of mug
still worked. Exams are on the way, and now I have yet another displacement
activity, not to mention the distraction caused by all the other mug tappers.
I disclaim responsibility for time and comestibles wasted, mugs broken and
nerves frayed by others repeating the experiment. An early explanation will
put us all out of our misery.
Anik Egan University of Guelph Ontario, Canada
Letters: No fifth fuel
Nick Gotts (Letters, 4 December) claims that energy conservation is
the cheapest way to cut the use of fossil fuels (the so-called ‘fifth fuel’).
The claim is perhaps based on the belief that more efficient use of fuel
will lead to lower fuel consumption.
However, it has been known for at least 125 years that efficient energy
use is associated with increases not decreases in total and per capita energy
consumption (see the work of Stanley Jevons, which is discussed by L. G.
Brookes in Energy and Environment, vol 1, p 318, 1990). Consequently, although
greater efficiency is desirable, it can only have the effect of increasing
consumption of electricity (and fossil fuels if the electricity is not generated
by nuclear power). There is no fifth fuel.
Gotts’s argument against the spread of nuclear power on the grounds
that it can conceal the ability to manufacture nuclear weapons is only superficially
valid. First, although a reactor is needed to produce plutonium, a bomb
can be constructed from uranium (as used at Hiroshima). Secondly, the construction
of a nuclear weapon is a formidable task, involving skills and materials
completely unrelated to those involved in the operation of a reactor.
A country’s lack of a reactor is no guarantee that it cannot construct
a bomb. Conversely, possession of a reactor does not necessarily lead to
the development of weapons. In any case, the plutonium produced in civil
power reactors is not suitable for making bombs (and has not been so used).
Nuclear weapons will be produced and used by those who want to do so
whether or not they operate reactors. Fear of the misuse of nuclear energy
is not a valid argument for failing to put it to good use.
Steuart Campbell Edinburgh
Letters: Cure for acne
We were interested to read ‘Peering through the smoke screen’ (9 October).
The author highlights an apparent protective effect of cigarette smoking
on a number of inflammatory diseases. In addition to these, we have recently
shown that severe acne is also a disease of nonsmokers.
To investigate further the effect of smoking on the inflammatory response
in the skin, we measured skin reactivity to a number of stimuli. These included
histamine injections, ultraviolet B, a detergent causing skin irritation
(sodium lauryl sulphate), ‘deep heat’ cream (containing nicotinates) to
increase blood supply to the skin, reactive hyperaemia after occlusion of
forearm blood supply, and common antigens.
We found that the smokers’ skin was significantly less responsive to
the stimuli applied to the skin than the matched controls. Smokers’ skin
reacted less vigorously to sodium lauryl sulphate. Interestingly, there
was no difference in the response to intradermal histamine alone, but after
injection of the intradermal antigens (including the house dust mite antigen)
there was a significant reduction in the number and degree of positive responses
in smokers compared to nonsmokers suggesting that smokers were reacting
less vigorously to those immunological stimuli.
The skin has obvious advantages as a model to study the mechanisms whereby
smoking alters the inflammatory response. This may be extremely relevant
to the effects seen in other tissues and disease states.
Our evidence, therefore, supports the observation that smoking has a
‘protective effect’ in inflammatory disease states. We certainly do not
condone or promote the ‘filthy’ habit, but further study of the potential
therapeutic mechanisms involved may eventually lead to new drugs for the
treatment of inflammation.
C. M. Mills and R. Marks University of Wales College of Medicine Cardiff
Letters: Blood and budgets
I regret to say that the letter from John Symington (4 December) regarding
autologous blood transfusions is somewhat misleading.
Autologous transfusion has been evaluated in a large number of British
hospitals over the past 20 years or more. Only healthy patients who are
undergoing elective surgery are eligible for autologous transfusion. The
process is time consuming and expensive. The additional costs of taking
a number of donations over a period of time in general hospitals that do
not routinely bleed donors (a function efficiently performed by the National
Blood Transfusion Service) does not help already overstretched budgets.
The increasing expertise in surgery has resulted over the years in a
huge reduction of blood being transfused to elective surgery patients. The
potential for autologous transfusions in a routine general hospital is still
only a small percentage of the overall transfusion needs of that hospital
and it is usually only small private hospitals that charge a premium for
this service who actually routinely use autologous blood.
The claim that autologous blood causes less post-operative infection
is possibly caused by stimulation of the immune system from the actual donation
of the blood in the first place. If indeed this is significant, then there
must be a good case for encouraging all able elective surgery patients to
donate blood prior to surgery, thereby solving two problems – post-operative
infection and a blood shortage.
D. R. Vale Sanguin International Barton-Under-Needwood Staffordshire
Letters: Bronze Age past
John Bexon (Letters, 18 December 1993) is quite right in his numismatico-metallurgic
researches: the British currency has been debased, as I found to my embarrassment
when I tried to demonstrate to my daughter that coins were not magnetic.
Enquiries showed that the 1p and 2p coins issued since 1992 are made from
what is officially described as ‘copper-plated steel’. The older bronze
(which was introduced as a coinage metal in 1860 to replace copper) is now
fast becoming history. The masses (3.56400 grams and 7.12800 grams respectively)
and diameters of the new coins are, however, identical to those of their
predecessors.
Malcolm Bacchus London
Letters: Read the comments
I have only very recently become aware of the human genome mapping and
sequencing projects.
I have difficulty believing that 90 per cent of our DNA is really meaningless
junk.
As a practising computer programmer and software engineer, I have been
writing coded instructions for well over twenty years, and nearly every
computer programming language I have ever used has made provision for the
language user to incorporate sections of program which are not used by
the machinery when the program is ‘expressed’. In a preliminary step, the
compiler or interpreter edits out these sequences before the code is expressed
in terms of actions.
In partial attempts to quantify what is required for software to be
‘well documented’, some programming standards have suggested minimum ratios
of comments to code: for example ‘at least two to one’. In practice, I have
often found a ratio of approaching ten to one more appropriate.
The function of the comments is to help human readers understand the
meaning of the program code. For many purposes, reading well-written comments
is sufficiently revealing to obviate the more difficult task of analysing
the code itself.
When developing software, however, it is common practice to ‘bury’ old
working code or alternative code or special purpose code by ‘commenting
it out’, so that it can easily be switched on and off.
To me, the actual and possible parallels between the so called ‘junk
DNA’ and computer program comments seem too intriguingly suggestive to ignore.
It may well be that biologists, too, will find their learning accelerated
by reading the comments before studying the code.
Hedley Lester Havant, Hampshire
Letters: Return of ING
Re ‘Mixed reaction to ‘safe’ reactor’ (This Week, 4 December): a thorium
reactor was proposed by Atomic Energy of Canada’s Chalk River Nuclear Laboratory
in the 1960s. It was to have been based on a very high intensity proton
linear accelerator and was known by the name of ING – intense neutron generator.
In 1967 the project failed to receive funding from the Canadian government
after our feasibility study yielded an estimated cost of 100 million dollars,
if memory serves me correctly.
Bill Chapman Camberley, Surrey
Letters: Neurals next
Your wonderful front page graphics and title promised us ‘Computers
that listen’ (4 December), but the article seems to have been deaf to the
amazing work done using neural computers.
Neural computers were inspired by research into how the biological brain
works. In a discontinuous speech recognition system a neural network approach
performs as well as or better than hidden Markov modelling (HMM). However,
it outperforms HMM in all cases with continuous speech recognition. It does
not require an endpointing algorithm and can model the coarticulation between
words. The neural network makes use of context information that is unavailable
to frame-level HMM processing. What is more important, a neural network
approach does not require the ‘ten times computing power’ mentioned in
your article.
First there were bandpass filters in the 1960s, linear predictive coding
in the 1970s and then HMM in the 1980s. Managers have invested company resources
in these technologies through the decades to crack the speech recognition
problem. How can we now persuade these companies to throw away this work
and move to neural computing – the technology of the 1990s?
Nick Ryman-Tubb Petersfield, Hampshire
Letters: Catalytic con
The article by Mick Hamer (This Week, 13 November) quite rightly highlighted
some of the dangers of using unleaded fuel in cars not equipped with catalytic
converters. However, the catalytic converter is itself far from being the
‘green’ solution to automotive emissions which it is represented as. The
main difficulties are as follows:
For the first two or three miles from a cold start the converter is
still warming up, and the emissions are largely uncontrolled. This means
that many short journeys (trips to schools, shops, etc.) create far more
pollution than the same mileage in one long journey.
The three-way catalyst (removal of unburnt fuel, carbon monoxide and
oxides of nitrogen) requires the fuel to be burnt inside a critical range
of air/fuel ratio centred on the stoichiometric ratio. Burning the fuel
at this ratio is 5 per cent to 15 per cent less fuel efficient than possible
for operation at lean air/fuel ratios (more air than for stoichiometry),
and also produces more carbon dioxide.
Current engine air/fuel ratio control systems cannot handle sudden
acceleration or deceleration and the corresponding perturbations in air/fuel
ratio outside the critical range are responsible for bursts of uncontrolled
emissions.
Damage to the converter may occur for several reasons, such as through
a malfunctioning fuel metering system, engine misfiring, combustion of engine
oil, or misfuelling with leaded petrol. As there are no on-vehicle sensors
to detect this (as there are for oil pressure, for example), the failure
could remain undetected until the next service, after which the polluting
vehicle may have been driven 10 000 miles. This would of course make a nonsense
of the legislated emission levels.
P. G. Eastwood Institute of Physical and Theoretical Chemistry Tubingen,
Germany