Letters: Teenage Trekkies
In your article ‘Education . . . the final frontier’ (This Week, 26
February) it is claimed that the Nobel prize-winning physicists Steven
Weinberg (b. 1933) and Sheldon Glashow (b. 1934) were both avid fans of
Star Trek when in their teens. This is extremely unlikely, unless, of course,
they won their Nobel prizes for the invention of the Tardis.
Philip Diamond London
Letters: Pins and angels
The title for your book review, ‘Angels on a quantum pinhead’ (5 March)
reminded me of a small bit of research into this subject that I conducted
some years ago.
This was initiated by the discovery, in looking through the International
Critical Tables section on units, that in pre-metrication times the Netherlands
had a unit of apothecaries’ weight called the Engel (or angel), equal
to 1.153 grams.
I was led to think that the question of how many angels could balance
on the end of a pin may not be limited by their size but by their mass and
the buckling load which the pin will support.
Only having access to a 20th century pin, I measured its diameter (25
thou) and length (1 inch) and took a figure for the Youngs Modulus of mild
steel, which gave a figure of 7100 angels to cause it to buckle. For this,
I had to use the gravitational acceleration (on Earth). Of course this will
almost certainly be different in Heaven, which is maybe where the question
really arises.
Donald Morten Southampton, Hampshire
Letters: By popular demand . . .
New 杏吧原创 has finally caved in to all those who keep asking us to
start a column in which readers ask and answer questions about the science
of everyday life. This means that in future, questions such as why the Godalming
station clock has one wrong digit, how vertical ice spikes form on a bird
table and why flamingos stand on one leg, will have a place of their own.
To start the ball rolling, here are a few questions sent in by readers
which we have not so far found the space for in our Letters section. If
you think you know the answer to any of these, write in. And if you have
a question of your own, let us know. We will publish more as they come in
and, once we have the answers, we will begin an occasional – perhaps even
weekly – column dedicated to this exchange of information.
Questions and answers should be kept as concise as possible; we reserve
the right to edit items that are too long. Please make sure that you always
include a daytime telephone number and a fax number if you have one. Restrict
your questions to scientific queries about everyday phenomena. A 拢10
book token will be sent to the author of each answer we publish. Write to
Kate North, New 杏吧原创, King’s Reach Tower, Stamford Street, London SE1
9LS, or fax to 071 261 6464. More questions will appear in the 9 April issue
of New 杏吧原创.
Letters: Psychedelic breakfast
Q: When I eat toast in the morning (particularly wholemeal with crunchy
bits), I notice that the green glowing symbols on the clock/timer of my
microwave bounce up and down in a sort of rippling manner. However, the
green symbols on the gas cooker clock (a slightly different hue) can only
be persuaded to take exercise with the most strenuous mandibular effort.
The red LEDs on my old calculator also appear lethargic. If I bounce up
and down, the whole microwave, including the display, seems to bounce up
and down in anti-phase. What is going on?
Graham P Evans Buckinghamshire
Letters: Behind bars
Q: There is a sequentially updated bar code appearing on the front cover
of copies of New 杏吧原创. I have tried without success to decipher these.
How does the coding system (or any bar-coding system) work and how do bar
code readers work?
Andrew Pettit West Sussex
Letters: Pipe dream
Q: In one of the earliest issues of New 杏吧原创, a scheme was outlined
for the long-distance transport of solid goods by pipeline. The idea was
for a national network of pipes about a foot in diameter, through which
cylindrical containers up to three feet long would be propelled by fluid.
The author maintained that many goods carried by road or rail could be transported
by this method. The original plan had a pipeline terminal in each town where
there would be a depot to provide distribution. If this proved successful,
the pipes were to be extended to homes so that food and mail could be delivered.
Does anyone know what became of the scheme?
Roger James Southsea
Letters: Clear thinking
Q: My nine-year-old son has come up with a question that has beaten
my years of science education. Why can you see through water? Can anybody
help us understand what it is about water – or glass, or any transparent
medium – that lets light through it?
Martin J Benwell Charterhouse College of Radiography London
Letters: Clammy claims
Q: It is very firmly held in this country, supported by a wealth of
anecdotal evidence, that ‘damp’ cold feels colder than ‘dry’ cold. Is there
any physical basis at all for this, or is it purely psychological?
Michael Bell Hertfordshire
Letters: Fast asleep
We read with interest your article concerning awareness under anaesthesia
(Technology, 29 January), and would like to clarify a few points.
There have been enormous advances in anaesthesia over the past 20 years,
and this has been associated with a progressive reduction in the incidence
of awareness. There is currently no evidence to support Gavin Kenny’s claim
that the incidence of awareness is 1 per cent. In the recent study of 1,000
patients by Liu et al from Nottingham (Anaesthesia, vol. 46 pp 435-437),
only two patients had conscious awareness with recall; and in both cases
the awareness was of some events immediately following the induction of
anaesthesia, but before surgery.
The incidence of awareness is linked to the particular anaesthetic technique
used, and is virtually unheard of where one of the potent inhalational anaesthetic
agents is used in appropriate concentrations. The potential for awareness
associated with the operation of Caesarian section has been addressed aggressively
by anaesthetists, and it is now generally recognised that deeper planes
of general anaesthesia are not so detrimental to foetal outcome as once
thought. There has been a significant reduction in recent years of awareness
during anaesthesia for Caesarian section.
The trauma associated with conscious awareness is well recognised and
its avoidance during general anaesthesia is the goal of all anaesthetists.
However, the assessment of a patient’s level of consciousness when paralysed
during anaesthesia is unreliable, and any clinically useful tests or monitors
will be welcome. Anaesthetists are therefore watching the progress in measuring
auditory evoked brain activity with interest. The real question is, will
this technique yield a clinically useful monitor. This will not be easy,
as it would have to detect reliably the two patients or so in 1000 who are
aware for a short time, without generating false positives.
P. Stewart and R. Nickalls University of Nottingham
Letters: But does it last?
Regarding the re-evaluation of sun protection factors (‘Sunscreens
and the protection racket’, 22 January, and Letters, 19 February), SPF says
nothing about the ability of the product to survive as a thin continuous
film on, or partially in, the skin. The term ‘Initial SPF’ would at least
reflect the truth that the artificial tests take only a few minutes and
tell us nothing about the protection we will be getting after that time.
Protection drops off at varying and often alarming rates during the hours
of use.
SPF 15, wrongly regarded as the maximum required figure, was based correctly
on the premise that we receive, on a sunny day, about 15 times the dose
required to produce a detectable burn, but incorrectly on the premise that
the protection does not deteriorate during that time.
Then there is the big question as to whether a test based on burning
human skin is a reliable indicator of protection from other harmful effects.
Published work on carcinogenesis and immunosuppression indicates that it
is not.
SPF measured at the end, rather than at the beginning, of a period of
use would be more useful, but laboratory conditions are not as relevant
as field tests in sunlight. The latter can involve activity and the accompanying
sweating and skin movement that tends to break up the protective film. There
are plenty of sunny days but everyone concerned has been looking for reasons
not to use this, the most relevant test of all.
Much of the published work on sunscreen efficacy is suspect because
of the omission of relevant data on product properties. I suspect that people
are dying because sunscreens are not as good as they could be. Incidentally,
hats don’t protect us from the significant amounts of UV reflected from
our surroundings.
Brian Wilkins Victoria University of Wellington New Zealand
Letters: But does it last?
I refer to the letter of Gavin Greenoak on protection against solar-induced
skin cancer by sunscreens. He is possibly not aware of a recent study from
Margaret Kripke’s group (Journal of the National Cancer Institute, vol 14,
pp 99-105). They measured protection in mouse ears by three sunscreen lotions
against ear swelling as well as pathological changes (sunburn cells) caused
by exposures to a sunlamp. However, the same lotions did not protect against
progression of malignant melanoma, in fact, they appeared to enhance it.
Thus, use of sunscreen lotions might actually enhance the dangers of overexposure
to solar photons by inducing a false sense of security in the user.
Meyrick Peak Argonne National Laboratory Illinois, US
Letters: Acid alarm
The idea of vaginal contraceptives such as 9-Nonoxinol being released
from polymers incorporated into contraceptive diaphragms or sponges is innovative
(Technology, 26 February) but rang loud alarm bells. Agreed, the pH of
the vaginal secretions is acidic, maintained by the normal lactobacilli
flora. But, there are compounding factors.
Cervical mucus tends to be alkaline and premenstrually, under the influence
of oestrogen, increases in volume and pH rises further. Also, there are
a number of aerobic and anaerobic organisms which colonise the vagina and
which usually make up some one per cent or two per cent of the flora. Overgrowth
with displacement of lactobacilli is not uncommon, producing changes in
the vaginal environment with pH levels usually above 4.5. Indeed, this is
clinically regarded as a diagnostic criterion for bacterial vaginosis –
probably the commonest cause of vaginal discharge rather than the ubiquitous
‘thrush’ or vaginal candidosis.
But asymptomatic colonisation with mixed bacterial organisms, producing
changes in flora and pH, is not uncommon, and has been increasingly recognised
in recent years. The pH range with bacterial vaginosis can vary from 5 to
8, and the absolute pH level is not specifically linked to symptomatology.
So, problems can arise in the asymptomatic female with high vaginal pH.
I. Alexander Dundee Royal Infirmary, Scotland
Letters: Minewater madness
I was glad to see New 杏吧原创 finally taking up the issue of the threat
of serious river pollution by minewaters (This Week, 19 February). Because
acid mine drainage is not a new phenomenon, there has been a tremendous
inertia over the current concerns in the northeast since I first raised
these possibilities on behalf of Easington District Council in December
1992. At that time, even the National Rivers Authority was reluctant to
accept the potential scale of the problem. But as your article rightly reports,
they are now taking the problem very seriously indeed. In fact, the issue
at stake is new in that we are now facing closure of coalfields, not merely
the closure of isolated mines.
British Coal actually pumps around 105 000 cubic metres a day from
nine pumping stations in the Durham coalfield (not 45 000 from three). When
one considers that the minimum maintained flow of the Wear at Lumley is
only 173 000 cubic metres a day, the impact of the total problem is potentially
vast.
Your article fails to mention the central issue of the debate locally
that the City of Sunderland currently takes about 20 per cent of its water
supply from the Wear at Lumley. A further 20 to 30 per cent of the city’s
supply (and the entire supply of Hartlepool) comes from the Permian aquifers
which may also receive a proportion of the minewater pollution. The possibility
that rising water, which is expected to be highly corrosive, might also
intersect buried services and old landfills also deserves consideration.
In addition, there is a serious risk of subsidence as rising water enters
old unstable board-and-pillar workings which are present in the shallowest
seams throughout the area. Finally, temporarily elevated methane gas emission
rates might also be expected as rising water increases subsurface pressures.
As the annual pumping costs for the entire coalfield are in the order
of 拢1 million, the economics of continuing pumping suggest that a
25-year investment in developing methods for a staged and controlled rise
in the water table would be a sensible solution.
Paul Younger University of Newcastle upon Tyne
Letters: Useful fax
The most serious snag in the fax software, which forces your reviewer
to buy himself an expensive plain paper fax machine (Review, 12 February),
is a printing problem for some of his fax pages. There are two solutions
for this. The first is to install additional memory in the printer – always
useful if he wants to print any graphic image. The second solution is cheaper:
lower the print resolution from 300 dpi to 150 dpi. This decreases the amount
of data to be processed by the printer by a factor of four.
Johan de Wit Klampenborg, Denmark
Letters: Oh dam
In your article ‘Britain’s other dam scandal’ (26 February) you state
that John Sutcliffe and Ben Piper, hydrologists on the Victoria Dam project,
were then both at ‘the British government’s hydraulics research station
near Oxford’. In fact they were from the Institute of Hydrology, just down
the road from us.
Dion Wright HR Wallingford Wallingford, Oxfordshire
Letters: Tape resurrection
I read with interest your article ‘Does a fate lie in store for videotape?’
(Technology, 5 March).
We were confronted with sticky degraded tapes containing our database
accumulated during the early 1980s. In all, there were 168 tapes out of
200 which were badly affected. We devised a reel-to-reel cleaning system
using lint-free iso-propyl alcohol saturated wipes which has enabled us
to ‘resurrect’ over 99 per cent of the data.
In your article you quote a ‘baking’ technique which enabled the tape
to be played ‘one last time’. Our cleaning technique allowed the tapes to
be replayed on a sufficient number of occasions to copy almost all the data.
Apart from those few data partitions where the oxide was very badly degraded
(1 per cent of the total), the quality of the data remained intact.
James Watson Medical Research Council Cambridge