Letters : Too much talk
London
David Gaskill sings the praises of voice recognition by computers (“Working
by Words”, Letters, 15 June, p 52). This may be fine for those who are
sufficiently elevated to have their own office or who work from home, but would
be considerably less than desirable for those of us who share an office with
several others.
It is difficult enough to concentrate when people are having normal
conversations around you, let alone speaking very slowly and clearly to their
computers. At least keyboard tapping is easy to screen out.
Letters : Physicists' fault
Uppsala, Sweden
R. K. King complains that the butterfly is always held responsible for
hurricanes etc. (Letters, 6 July, p 48). I fully agree and I find that Philip K.
Dick has given a much better description of the consequences of chaos theory in
his novel The Man in the High Castle (1962). There he writes: “It’s the
fault of those physicists and that synchronicity theory, every particle being
connected with every other; you can’t fart without changing the balance in the
Universe.”
Letters : Never safe
Waterbeach, Cambridge
Almost every time the differing effects on the body of mirror-image drugs
(enantiomers) is mentioned in the scientific literature (both lay and academic)
the example of thalidomide is given (“Thinking big”, 13 July, p 22).
It is usually claimed that one form of thalidomide is the notorious agent of
deformities while the other is “a harmless sedative”. This is now known to be
untrue and may give readers the false impression that the thalidomide tragedy
could have been averted had the technology for filtering out the harmful
component been available at the time.
The so-called harmless form is in fact partially converted in the body into
the other form and so a “safe” morning sickness drug based on thalidomide is
simply not possible.
Letters : DNA danger
As someone working in computing, I read the story on DNA computers with great
interest. I was full of admiration at the ingenuity of researchers in this area.
However I was also shocked and surprised at the apparent lack of responsibility
and respect for DNA.
Recombinant DNA experiments under strict lab conditions to promote
understanding and advancement of medical knowledge are one thing, but to
introduce countless random DNA fragments into the environment is nothing short
of lunacy and I believe would result in strains of organisms that could evolve
to kill us all. I would not be surprised to learn that many of the new viruses
we are fighting may have arisen from a DNA soup carelessly washed down the
sink.
Letters : Balloon isn't up
Weymouth, Dorset
John Smith writes about high altitude balloons and solar sails (Letters, 13
July, p 51). Unfortunately, there is no overlap between the zones over which
each can operate. There is a gap between the zones of at least 30 miles. There
is also the problem of aerodynamic heating.
However, he has my sympathy. Rockets are an inelegant method of getting into
space and their undoubted success has had the effect of inhibiting serious
consideration of other methods.
I suggest that Smith should take a look, if he has not already done so, at D.
H. DeVorkin’s Race to the Stratosphere (Springer-Verlag 1989), which
summarises most of what has been achieved with high altitude balloons. He might
also note that though solar sails cannot function at the heights reached by
balloons, other methods of propulsion using the Sun’s radiation might. These
might include very large thermal propulsive ducts operating on a principle
demonstrated by the radiometers that used to be seen spinning merrily in most
chemist’s windows, or possibly very large arcjets powered from photocells on the
large surface areas available on high altitude balloons.
However in order to climb higher, aerodynamic lift is needed and eventually
the balloon, propulsion system, lifting surfaces and all have to reach orbital
velocity. The light weight and large flimsy structures necessary in high
altitude ballooning will be unable to withstand the aerodynamic heating inherent
in reaching space and this will probably kill the method. But hopefully, there
may yet be another and better way than rockets.
Letters : Timely rejoinder
NSW, Australia
In his piece on my Time’s Arrow and Archimedes’ Point (Review, 29
June, p 42) Peter Coveney complains that I dismiss non-equilibrium statistical
mechanics and chaos theory too quickly.
Following Ilya Prigogine’s “Brussels School”, Coveney believes that these
theories provide the key to the time-asymmetry of thermodynamics 鈥攕ee for
example his own book The Arrow of Time (W. H. Allen, 1990), written
with Roger Highfield.
Like everyone else who tries to apply statistical mechanics to explain why
entropy increases irreversibly, the Brussels School is attempting a piece of
mathematical magic: to derive an asymmetric result from symmetric mechanical
theories (without putting the asymmetry in at the beginning, primitive and
unexplained).
This is not my main reason for dismissing this approach, however. Its more
basic mistake is to misunderstand what is actually puzzling about the
thermodynamic arrow.
The odd thing is not that entropy is high in the future, but that it is not
high at all times. The Brussels methods do a fine job of telling us how
non-equilibrium systems behave, given that there are some. However, they tell us
nothing about why such systems exist in the first place. As I explain in my
book, that’s the real mystery of the subject, and the Brussels methods simply
don’t touch it. (As writers such as Roger Penrose and Stephen Hawking have
emphasised, the best current prospects for an explanation lie in cosmology.)
Coveney recommends that my book be read in conjunction with “more broadly
based works” on the subject. If his own book on the arrow of time is one of
those he has in mind, then I, too, recommend the combination鈥攖hough partly
in the hope that my book will serve as an antidote to some of the confusions of
the Brussels School. (In a nice bibliographical symmetry, I reviewed Coveney’s
The Arrow of Time when it appeared in 1990. Interested readers will
find my review in Nature, vol 348, p. 356, or on the Web at
http://plato.stanford.edu/price/preprints/arrow.html.)
Letters : Uncertain universe
Fukui-Ken, Japan
I was intrigued by Russell Smith’s criticism of the attempts to explain the
origin of the Universe by applying Heisenberg’s uncertainty principle (Letters,
25 May, p 57). If there was no observation or “measuring event” possible at the
origin of the Universe, why would the probability wave function that symbolises
the energy and matter to be found in space ever “collapse” into a reality
(analogous to an electron “choosing an energy level” instead of simultaneously
inhabiting both)?
How does this relate to Hawking radiation which, again, would be an
“unobserved phenomenon”?
Letters : Better batteries
Gosport, Hampshire
Mick Hamer erroneously concluded that with the demise of Silent Power, went
the last British hopes of a lead in advanced battery technology (This Week, 1
June, p 6).
At the Defence Research Agency we have been developing an advanced
rechargeable, high temperature battery for 15 years. It is the
lithium-aluminium/iron sulphide battery, which is commonly referred to
as LAIS.
This system was originally developed for submarine propulsion, but also has a
part to play in land-based electric vehicles. We are now at the stage where we
are looking for partners to exploit the technology commercially.
This is not the only system we are researching . In addition to fuel cell
development, we are also developing specialised batteries for military systems
such as seawater batteries, high temperature primaries, advanced lithium
rechargeables, and reserve batteries.
Letters : Hidden subsidy
Buxton, Derbyshire
“Polluter pays” is an appropriate principle, despite what Alex Milne says
(Letters, 13 July, p 50). If fuel oil users who burned desulphurised oil were
taxed less (or exempted from fitting flue-gas desulphurisation equipment), you
would create a demand for desulphurised oil, and some oil would have sulphur
removed at source as a result, if that was cheaper.
When the polluter isn’t made to pay, this amounts to a hidden subsidy. The
same goes for any other damage to public assets. My thanks go to A. K. L.
Dymoke-Bradshaw (letters, same issue, same page) for an excellent example: heavy
goods vehicles with large axle weights do not pay an appropriate charge for wear
and tear to the road, and this is one of the hidden subsidies they enjoy.
If the final consumer has to pay extra because of pollution, that is a
valuable market signal for us to avoid products which involve pollution. For
example, if road transport and shipping companies had to pay more for the damage
or pollution they cause, we would all be encouraged to buy local products made
with local materials.
Letters : Radio risk
Liverpool
John Simpson from Microshield writes that “epidemiological studies will be of
no use for at least 10 to 15 years”, with regards to the hazard of using mobile
phones (Letters, 20 July, p 50). However, a quick survey of radio equipment
around my office reveals some interesting statistics: two-way radios typically
operate at a much higher power and lower frequency than mobile phones, and have
been around for a great deal longer.
So it would seem that security guards, police and other members of the
emergency and armed services, who have been using two-way radios for many years,
are at much greater risk than the occasional user of a mobile phone. The
frequencies two-way radios use penetrate further into the brain than the higher
frequencies used by most mobile phones.
My mobile phone, one of the newer PCN digital variety, operates at a
frequency of 1800 MHz with a power output of 250 milliwatts to 1 W, depending on
the reception. However, one of our two-way radio operates at the highest UHF2
bands of around 450 MHz, with a power output of 5 W. A corresponding GSM digital
phone which operates at a similar frequency still only has a maximum power
output of 1 W.
Two-way radios have been in general use for at least 25 years, so there
should now be enough data to conduct an epidemiological study on the people who
use these radios.
Letters : Safe as …
London
Paul Murdin, director of science at the British National Space Centre,
unwittingly reveals the awful truth about formal risk assessment when he says:
“As a result of its origins, Ariane 5 had an estimated success factor of 98.5
per cent, from the outset. Whatever happened was evidently outside this
calculation of risk鈥攏o one calculates the probability of the utterly
unexpected” (Forum, 29 June p 48).
The trouble with this view, and the trouble with risk assessment, is that the
unexpected is one thing that can usually be relied upon. The problems that are
expected, and hence evaluated in the risk assessment, are those that diligent
engineers would try to minimise in advance. This leaves unexpected problems as
the most likely cause of accidents, but because no one knows what they are or
how to assign their probability they remain outside the risk assessment. Should
the estimated Ariane 5 “success factor” of 98.5 per cent have carried small
print pointing out that this figure did not apply to unexpected problems?
It is distressing to recall that these logically dubious techniques are also
applied to much more hazardous operations such as the safety of nuclear power
stations, design of nuclear waste dumps and release of genetically engineered
organisms.
Letters : . . .
Koenigswinter, Germany
In order to check ESA’s claim of “98.5 per cent reliability” for the new
launcher, one would just have had to look at the past 40 years of space flight.
According to the newsletter Jonathan’s Space Report (No. 289, 5 June),
Ariane 5 was the 35th totally new launcher introduced in the history of
spaceflight鈥攁nd of its 34 predecessors only 63 per cent succeeded in their
first attempt.
Even if one considers only medium and large rockets, the success rate of
their maiden launches before Ariane 5 was only 69 per cent. So even ploughing a
staggering amount of money into the development programme doesn’t automatically
buy you safety.
Letters : . . .
Munich, Germany
Jennifer Naylor’s letter about one possible (in my mind rather improbable)
cause for the Ariane 5 failure reminded me about the blow-up of the last Europa
II (F 11) in Kourou on 5 November 1971.
In that flight, the inertial guidance computer (housed in the German third
stage, but under British responsibility) stopped executing its program about 150
seconds into the flight, resulting in a break-up due to wind forces quite
similar to the Ariane 5 mishap. A missing or faulty grounding in the payload
fairing triggered an arc-discharge which stopped the program.
The catch: this failure mode of the inertial guidance computer had been
identified long before the flight during ground tests on an electrical mock-up
at the Hawker Siddley Dynamics facility in Stevenage, but nobody talked the
English into modifying the software, for example by adding an automatic restart
capability.
Moments before everybody noticed that something was going wrong, the poor
Briton monitoring his inertial guidance computer telemetry was overheard
mumbling, “I think we’ve got program corruption”鈥攚hich in fact we had.
Letters : Bomb material
Watford, Hertfordshire
Estimates of the damage done by the two recent IRA bomb attacks in England
run up to 拢700 million. Both attacks used ammonium nitrate, probably sold
as fertiliser. Savings by shipping fixed nitrogen in this concentrated form
probably amount to barely 拢7 million less than the cost of transporting
ammonium sulphate. Is the risk worth it? If this substance must be used, why not
distribute it dissolved in water? Road tankers could deliver it conveniently to
farmers who almost always have a variety of tanks and spraying equipment.
Letters : Depleted by deer
Grantham, Lincolnshire
I share the enthusiasm for trees expressed in Oliver Tickell’s article (This
Week, 6 July, p 5) but have two reservations: deer and fire.
Throughout mainland Britain we are experiencing an unprecedented explosion in
the deer population which already adversely affects natural tree regeneration
and will, without serious and concerted deer-proofing, preclude future natural
forest development.
In the woodlands of the English Midlands and East Anglia already colonised by
muntjac, all ground flora, including tree regeneration, is being seriously
depleted. In Scotland, wherever red deer are present in woodland, regeneration
simply does not occur. Equally, the steady recolonisation by roe deer of most of
Britain will, I predict, also prevent regeneration, as is already evident in
woodland across most of Southern England.
The risk of fire must also be considered seriously in those areas where a
build-up of dead wood is encouraged. This management strategy provides the
tinder, made more combustible by the predicted hotter, drier and longer summers.
Add to this unrestricted public access to our forests, which is encouraged and
will increase, and the spark is there for frequent and widespread forest
fires.
With these two elements combined, naturally generated forests in the future
must be just a dream.
Letters : Getting a rise
Sandwich, Kent
We read with interest your article on a gel for treating impotence
(Technology, 27 July, p. 18). The suggestion made in the article that a pill
being developed by Pfizer to treat impotence “promotes the production of nitric
acid in the penis” is misleading.
There is compelling evidence from animal studies and in vitro experiments
with human tissue to suggest that nitric oxide (not acid) and its intracellular
messenger, cyclic guanosine monophosphate (cGMP) play an important role in
penile erection. During sexual stimulation, nitric oxide, released from nerve
endings and the endothelial lining of blood vessels, stimulates the production
of cGMP. cGMP in turn relaxes the smooth muscle cells of the corpus cavernosum
in the penis and allows blood to engorge the lacunar spaces of the penis, a key
factor in producing an erection.
Sildenafil (Viagra) is a selective inhibitor of the type 5 phosphodiesterase
enzyme, which metabolises cGMP in the human penis. Sildenafil therefore does not
promote the production of nitric oxide in the penis but improves penile
erections by enhancing the action of endogenous nitric oxide and cGMP on the
penis. Experimental evidence demonstrates that this is a peripheral action on
the penis. Furthermore, the way sildenafil works suggests that it will only
improve erections during sexual stimulation when nitric oxide is released.
Impotence, or penile erectile dysfunction, is a common medical condition
which can affect up to 50 per cent of men aged between 50 and 70 years. There is
currently no efficacious oral therapy for this condition which is often
distressing and is frequently associated with depression and poor
self-esteem.
We are encouraged by the efficacy and toleration profile of sildenafil in
clinical studies in men with impotence. We believe that sildenafil represents a
new class of orally active and peripherally acting drug for the treatment of
impotence.