Letter: Hit the deck
Your article makes mention of the effect of fitting sponsons to roro
vessels in order to improve stability under damage conditions; for example,
after a collision. As often happens in engineering when measures are taken
to ameliorate one problem, another is made potentially worse, in this case
the behaviour of the ship under undamaged or intact conditions. The effect
of fitting sponsons is to increase the righting moment when the vessel is
heeled and thereby to increase the natural frequency of rolling.
The roll amplitude can be controlled by the action of active stabilisers
(fins) or flume tanks where these are fitted. However, any increase in roll
frequency will more than proportionately increase the lateral accelerations
and so the forces experienced by passengers and cargo. Apart from the discomfort
of the passengers, the effect on items of cargo such as trucks and trailers
will have to be taken into account, especially where these are placed on
the upper decks of a ship. Any inadequacy in the restraints or lashing systems,
both of the vehicles to the ships’ decks and of the cargo within vehicles,
may therefore have serious consequences in the shifting of cargo. As the
article pointed out, cargo shifting accounts for a significant proportion
of roro vessel casualties.
David Dawson Lancaster
Letter: Speakers cornered
As a recent recruit to postgraduate research and a firm believer in
‘science popularisation’, I was slightly disturbed by some of the assumptions
made by certain eminent contributors to your recent article, ‘The perils
of popular science’ (18 August). In particular, I was concerned that because
academic appointments are to be based solely on research record, then young
scientists, serious about their career prospects may be encouraged to neglect
wilfully the development of wider communication skills.
The damage done to the understanding and appreciation of a particular
discipline by bad lecturing cannot be underestimated. Surely, then, a recruitment
policy which discriminates positively in favour of inexperienced and/or
reluctant orators to fill university teaching posts is dangerously short-sighted.
Taken to its logical conclusion, as ever increasing financial constraints
push the emphasis further in the direction of ‘the straight and narrow path’,
it is possible to envisage a future where science departments will be populated
entirely with communication-shy introverts, not in the habit of transmitting
enthusiasm for their subject matter. This bodes ill for the future of science
education in the short term and, by extension, for real scientific endeavour
in the long term.
John Mooney London
Letter: Bloody Rover
William Wood seems to have overlooked the common knowledge that the
best way to remove skunk odour from clothes and hair (including dog hair)
is to wash with tomato juice (Science, 4 August). This remedy is almost
universally applied in areas where frequent dog/skunk interactions are encountered.
Malcolm Comyn Calgary Alberta Canada
Letter: Not fazed
Brian Clement is a little unfair on the ‘worldwide community of quantum
physicists’ (Letters, 11 August). The quantisation of the electromagnetic
field is treated sketchily, if at all, in university undergraduate courses,
but that part of the community concerned with quantum optics has not neglected
the concept of phase.
We can quantise the energy states of a single mode of a radiation field,
just as the energy states of a simple harmonic oscillator are quantised
in simple quantum mechanics. The classical energy variable goes over to
an operator usually called the photon number operator. Eigenstates of this
operator define the number of quanta of energy in the mode (or photon number).
Similarly, the classical phase goes over to a quantised ‘phase operator’
producing a measurement of what is usually (unhelpfully) described as the
‘photon phase’. Its eigenstates define the phase of the wave relative to
spatial axes.
Heisenberg’s Uncertainty Principle shows that an experiment where the
number of photons is perfectly defined destroys all phase information, and
an experiment where the phase is perfectly defined destroys all energy information.
Classically, we usually think of an ‘ideal’ monochromatic sinusoidal
wave with well-defined amplitude and phase. In quantum optics this is not
an easy thing to do, but we can define so-called ‘coherent states’ of the
field, where the uncertainty in the photon number and photon phase are together
minimised and become negligible as the photon number becomes large. These
coherent states then go over to our classical picture.
The subject is well covered in Loudon’s The Quantum Theory of Light
(OUP).
D G C Jones The University of Sussex Brighton
Letter: Plucky parrots
Marian White, writing on parrots, omits to mention the slaughter of
cockatoos as pests in Australia by poisoning, shooting, gassing, and clubbing
in nets, and yet none are allowed to be exported (Letters, 9 June).
We have seen many cockatoos, principally Indonesian, over the last 30
years and yet very few were feather pluckers and none were given to self
mutilation. There are two depluming conditions known to vets: feather plucking,
and beak and feather syndrome. The first, although unsightly, is relatively
benign, has unknown causes, and often responds to a change in the conditions
under which the bird is kept. The second is probably caused by a naturally
occurring virus (it affects free-living birds as well as captive ones) and
is currently the subject of research.
With regard to the use of parrots as a natural resource, she seems to
miss the point completely. In the Third World they have three ‘values’ that
have persisted since prehistoric times: as food, as items of commerce, and
entirely negatively, as crop pests. Put to the first and last use they yield
little or nothing of benefit to their populations or to mankind. As high-value
live birds for the international trade they, and the forests from which
they are produced, become a valuable asset.
As for the unsubstantiated allegation of 80 per cent mortality in birds
taken for trade, it is contradicted by independent studies and official
reports, indicating that 75-80 per cent survive, and is nothing more than
attempts by some propagandists to malign the trade.
Barry Riley The Pet Trade and Industry Association Bedford
Letter: Darwin's ills
In his review of John Bowlby’s new biography of Chalres Darwin it was
acute of Morton Schatzman to doubt whether hyperventilation could cause
vomiting (Review, 11 August). Some of Darwin’s other symptoms could not
be caused by this syndrome either, such as rheumatics and swollen limbs.
The Chagas disease theory is exploded by his doctor’s statement to Maria
Edgeworth that the Beagle voyage ‘was not the cause, only the continuance
of his suffering – for that before he went to sea he was subject to the
same’.
Only one theory can explain every one of Darwin’s symptoms and their
fluctuation under physical and emotional stress: multiple allergy arising
from a dysfunctioning immune system. The inheritance pattern is there, and
evidence of crucial immunosuppressive encounters.
Fabienne Smith Edinburgh
Letter: Human zoo
How very apt that your article ‘Too much of a good thing’ on fertility
treatments should be followed by ‘All the world’s a zoo’, concerning endangered
species (18 August). Is not Earth’s greatest problem one of people pollution?
W T R Bowley Bracknell Berkshire
Letter: Pin sticker
David Slade suggests that of the USSR, US, China and the Middle East,
only one is a good candidate ‘for demonstrating a global social conscience’
(Letters, 25 August). Which one?
Reg Nelson Jesmond Newcastle
Letter: Wing and a prayer
David Fisher from Cardiff is, I hope, the only one of your select readers
who doubts Bernoulli (Letters, 11 August). An aircraft with a conventional
wing profile sustains lift even when flying upside down, since the reference
is not the ground but the surrounding air mass and an aircraft with a symmetrical
wing profile sustains lift at an angle of incidence higher than that of
a conventional wing. I leave the further explanation of these banalities
to the efforts of the gliding instructors around Cardiff.
Wolf Seufert Universite de Sherbrooke Sherbrooke Quebec Canada
Letter: Fertility debate
I was interested to read Margarate Stacey’s article and would support
her call for more research into the sociological implications of the new
reproductive technologies (‘The case of the missing science’, Forum, 18
August). However, as former secretary of the Interim Licensing Authority
(ILA) I would like to correct the rather mistaken impression she gives of
the Authority and its attitude to the social issues surrounding assisted
conception.
The Interim (formerly Voluntary) Licensing Authority was not set up
by the government but, following the Warnock Report, jointly by the Medical
Research Council and Royal College of Obstetricians and Gynaecologists.
Its members included one social scientist (a research psychologist) but
it must also be borne in mind that 50 per cent of the Authority, including
the chairman, is lay and that the contribution of lay members becomes particularly
important in the discussion of social issues.
The sociological implications of egg donation provoked much discussion
within the Authority and in an attempt to reach a consensus, in order to
draw up appropriate guidelines, the Authority had a meeting on the subject
in association with the King’s Fund Centre in September 1988. The meeting
extended over one day and the social and cultural implications of egg donation
were discussed, particularly the effect of known and unknown donors on our
kinship system, the likely effect on family relationships and the development
of the child, and on the status of the child within our existing laws.
The speakers included an eminent sociologist and social anthropologist,
a psychologist specialising in child analysis and an expert in family law.
The participants included other sociologists, professional counsellors,
patients and clinicians. A short account of the meeting may be found in
the Fourth Report of the Voluntary Licensing Authority (1989). Sadly, the
King’s Fund decided not to publish the proceedings.
The Authority lists little sociological research in its report because
a licence from the Authority is not required for such research. Licensed
centres carrying out in vitro fertilisation are required to send to the
Authority details of their publications. These are, of course, predominantly
clinical and scientific; few centres have the resources to undertake sociological
research. The Authority would not be aware of sociological research being
undertaken elsewhere unless specifically approached.
Jennifer Gunning Agricultural and Food Research Council Swindon Wiltshire
Letter: Hit the deck
Mike Hamer’s article on ferries ignores things which may quickly and
cheaply reduce the death toll in the event of a roro capsizing (‘The risks
of ferry travel’, 18 August).
In March this year I travelled overnight from Hull to Rotterdam on the
Norsun and from Zeebruge to Hull on the Norland. In both vessels the evacuation
instructions were ‘Dress in warm clothing and go to assembly areas in lounges
..’ These areas would take many minutes to evacuate to the boat deck, where
life jackets were stored.
My advice to my wife was ‘At the first indication of trouble, head for
the open deck and get a life jacket on. Walk through any crew member who
tries to delay you as there may be only 45 seconds before you are in the
sea!’ Is it not about time that the ferry companies at least revised their
evacuation procedures to reflect the risk of a ferry capsizing?
David Fawthrop Halifax