Mite-free mats
I read with interest your article highlighting Courtaulds’ work on producing bedding that kills dust mites
(This Week, 19 September, p 7).
As your expert John Maunder could have told you, Courtaulds are not the first to achieve this
breakthrough.
Our Kingsmead Carpets company has been offering carpets for more than two
years that work in a similar way to create a healthy household. Dynomite-treated
carpets have been certified by the British Allergy Foundation and provide relief
for those with dust mite allergy, particularly asthma sufferers.
Bad backs
A recent paper in the British Medical Journal (vol 316, p 1356)
contradicts George Felis’s claim that the “overwhelming majority of back pain
cases resolve themselves given time”
(Letters, 19 September, p 54). It states
that most back pain patients will still be experiencing pain and related
disability a year after consulting their GPs.
According to the paper, almost 90 per cent of patients with low back pain
will stop consulting their GPs within three months, but will continue to suffer
pain.
Chiropractors treat people with back pain, including many chronic cases for
whom painkillers and hospital outpatient referral have failed, regularly and
highly successfully.
Perhaps it is doctors who are deluding themselves that their patients have
recovered spontaneously simply because they have not returned.
Less is more
Alex Galloway’s facts concerning the unchanging energy demand per household
from 1970 to 1993 give a distorted picture of energy consumption in Britain
(Letters, 3 October, p 56).
Total national energy consumption did increase during this period, as did
consumption per individual. Presumably the money saved on domestic fuel bills
has been spent on air travel, petrol, an increase in the proportion of a
“household” occupied by the individual, and generally more consumption of goods
that require energy to manufacture.
This was essentially the point made in your Focus article (This Week, 5
September, p 18). I wonder what reaction the author, Fred Pearce, would have
received if he had made the following assertion: all fossil fuels located near
enough to the surface to be extracted with a net energy yield will eventually go
up in smoke, and so we need only assess the costs and benefits of prolonging the
process compared with continuing as we are. Personally, I wouldn’t dare make
such an assertion, but you have to ask.
Letter
After 41 years of highly successful practice, I had thought my finely honed
skills in manipulation, careful case management and rehabilitation were the
reasons for my good results in dealing with back pain. Now Felis’s letter puts
me right.
According to him it is not these after all鈥攊t has been my “placeboid”
saturnine good looks, the shining teeth and deep, warm and comfortable office
carpets that have been curing them.
Abandon your five-year BSc degree courses, young chiropractors, don’t leave
anything to chance. Get thee to the charm school and polish your smiles.
脰tzi's arrows
I wonder if Tom Loy’s comparison of the iceman 脰tzi’s bow and arrows with Neolithic examples
(“Blood on the axe”, 12 September, p 40)
would have led to the same conclusions if he had a few examples of modern East African hunting
bows and arrows to hand.
The Akamba people of Kenya would be very impressed with 脰tzi’s armoury. They
also have no need for notches on the bow to anchor the bowstring. A noose at one
end, a figure-eight lashing and a clever elbow and knee routine is all they need
to tension a bowstring to the very high load required for a “snap pull” hunting
bow, which demands a variable length bowstring.
A lightweight arrow and head fired from this bow has remarkable power of
penetration over middle distance and is ideal for big game. The Akamba use heavy
arrows and heads for small game, as an average hit will cause significant damage
and result in a blood trail to follow. There is lots of street cred in carrying
only three arrows鈥攐ne for the shot, one in case the quarry turns on you,
and one spare.
Another similarity is the fact that 脰tzi’s arrowheads may be designed to part
company with the shaft after impact so that you get to recover the shaft for
reuse.
The question that would be left on the lips of the Akamba would be what sort
of poison 脰tzi was using, because high penetration detaching arrowheads in the
hands of the Akamba are given a liberal coating of arrow poison before use. Did
脰tzi have an accident with a poisoned arrow?
Fireball file
Charles Seife considers that “the mystery of ball lightning may finally have been solved”
(This Week, 26 September, p 6).
Sadly, Antonio Ranada’s theory suffers from certain inconsistencies that make it
hard to believe, although the idea may appear attractive.
He proposes that a strong magnetic field is confined within the fireball,
this field being associated with currents in hot ionised filaments tangled
within the ball. He argues that linkage of magnetic field lines will prevent the
outward explosion that might otherwise be expected (due to the very large
magnetic pressure within the ball).
This is not the case, however. Spherically symmetrical expansion of a ball
containing a tangled magnetic field is entirely compatible with the conservation
of magnetic helicity (the simplest measure of entanglement), and magnetic energy
in such a process of expansion decreases in inverse proportion to the radius of
the ball. Magnetic field entanglement does not impede this process.
Ranada and his coauthors also assume that the gas inside the ball flows with
the local Alfv茅n velocity, to maintain “magnetohydrodynamic equilibrium”.
Such equilibrium is possible only in an incompressible medium. It does not
prevent expansion of the ball, which is linked with the compressibility of the
gas.
Given the estimated magnetic intensity, the Alfv茅n velocity would be
about 2000 metres per second, and the resulting flow in the fireball would be
supersonic. It is implausible that very rapid expansion鈥攅xplosion鈥攐f
the ball would not occur in these circumstances.
Letter
Fellgett is quite correct in his observation that failure of the neutral wire
in a Protective Multiple Earthing (PME) system causes metalwork to rise above
earth potential. The metalwork does indeed rise to some potential between earth
and live. This is simply Ohm’s law applied to the potential divider formed by
the attached load resistance and the resistance of the earth return path.
However, this does not necessarily constitute a hazard.
In a properly fitted PME installation, all the metalwork (washing machine
casing, water pipes, gas pipes, and so on) is bonded to the same local earth
terminal. All metalwork therefore rises to the same voltage. There should not be
any accessible points between which there is a sufficient voltage to constitute
a danger. Between which two points was the potential difference of 180 volts
measured?
Fellgett is quoted as saying: “Rarity is no excuse for ignoring necessary
precautions.” If he consults his Contract for the Supply of Electricity, he
should find that the responsibility for adequate earthing lies not with the
installer, but with the householder.
Wired up
No domestic wiring system is proof against multiple faults. The purpose of
the Institution of Electrical Engineers’ wiring regulations is to reduce the
risk to a tolerable level
(This Week, 19 September, p 6).
However, the regulations require more than just the earth/neutral link and
the “stake in the ground”. If the regulations had been followed properly then
the fact that the stake was not deep enough would have been revealed by testing
on installation and every five years thereafter.
You can’t get a shock unless there are two things at different potentials.
The regulations require all exposed metalwork to be connected, so that even
under the fault conditions described by Barry Fox there would be no potential
difference around the kitchen, except perhaps for a bare stone floor.
Peter Fellgett says: “Nor is it adequate to rely on the installer to assess
all the circumstances.” So who will? Electrical installations can be dangerous
if not fitted and maintained properly, and someone has to accept responsibility
for making it safe. If not the installer, then who?
As for banning joints that might corrode, that’s just silly. Should we ban
pipe joints that might leak, or tyres that might get punctures?
Letter
脰tzi couldn’t have died during cold, clear weather. The choughs and other
scavengers would have dealt with the corpse in an hour or two. It must have
happened during the onset of heavy snow, most likely in the autumn and probably
during one of the cold fluctuations that interrupted the general post ice age
warming. The snow saved him from the choughs’ beaks.
Letter
The suggestion that the end of the bow had no notches and therefore was
unfinished was ridiculous. As a bow and arrow maker myself, I know that notches
in the wood itself are dangerous on powerful bows. A cut at right angles to the
grain on the convex side spells disaster.
Longbows found on the Elizabethan ship the Mary Rose have horns at the tips
shaped to take the string and avoid a direct cut into the sapwood. This made the
bow safer to use.
脰tzi’s bow avoids the problem of cuts in the timber by having coned ends. A
simple, self-tightening bowyer’s knot is all that is required.
Unpronounceable
Contrary to Nigel Depledge’s assertion
(Letters, 5 September, p 56),
an acronym does not have to be pronounceable. It is, to quote Chambers
Dictionary, “a word formed from or based on the initial letters or
syllables of other words”鈥攁lthough of course its creator may well aim at
pronounceability.
RSPCA is an acronym, but my attempts to pronounce it have not yet met with
success.
Letter
In my youth a restaurant in Geelong, Australia, was convicted of selling
dishes containing “roof rabbit”, which is, of course, cat.
Letter
Cowboys riding the Canadian prairies sometimes partake of a delicacy called a
“prairie oyster”. This item is generally available only when the young male
bulls are rounded up for castration. If the camp cook lightly saut茅s
these savouries with butter and garlic, they have some of the gastronomic (and
other?) characteristics of oysters, hence the name.
Shame about the name
Following on from the discussion about how some restaurants like to use
euphemisms to describe their dishes
(Letters, 10 October, p 54),
I’d like to draw attention to the reverse tendency, which can often be found in France.
A couple of appetising examples are: Pets de nonne, small cream
cakes, which in English are “Nun’s farts”; and Crottin de Chevignol, a
goat’s cheese, which means “Chevignol dung”.
Letter
G贸mez-Alonso should read the very convincing book by Paul Barber,
Vampires, Death and Burial (Yale University Press, 1988), which suggests an
equally plausible explanation: that tales of vampirism result from a
misunderstanding of the processes of decay and putrefaction.
Perhaps G贸mez-Alonso is not quite as dogmatic as you present him.
After all, there does not have to be just one explanation.
Teeth of the tales
Juan G贸mez-Alonso is the latest in a long line of doctors to attempt a
rational explanation for vampirism
(This Week, 26 September, p 22).
As with the others, his theory does not provide a convincing match to the
literature of folklore, which mostly refers to individuals whose vampiric
behaviour supposedly begins after death, rather than shortly before.
Moreover, one of the best known and most extensive outbreaks of vampirism
took place in Poland and Russia in 1693, before his rabies epidemic. Indeed,
vampires are found in early medieval, classical and ancient Jewish literature,
as well as in tales from Africa, the Americas and Australasia.
Attempts at rational explanation fail to show why certain categories of
people (suicides, the executed, those murdered, women who died in childbirth,
those lost at sea) dominate the list of those accused of vampirism. These were
all people who had suffered “bad” deaths and were therefore seen as the most
likely not to lie silent in their graves.
A “supernatural” element involving the fear of the dead by the living cannot
therefore be denied within vampiric folklore.
Digital excess
Following Feedback’s comments on excessive numbers of characters used to identify products
(5 September and
Letters, 3 October, p 57),
I recently dealt with a travel insurance company who insisted I quote their 28-character
reference in all communication (CIL97/ 00001330/2422/OPS$YAMA). This is
more characters than are required for the English language.
The Bond effect
You mention pseudoscience in connection with the Martini publication Art of Mixology
(Feedback, 12 September, and
Letters, 10 October, p 54).
Dr Hahnemann, the founder of homeopathy, required his dilutions to be “shaken, not
stirred” and even specified exactly how that was to be done (banging the bottle
against a block of leather-covered wood).
No wonder, therefore, that the work by French scientist Jacques Benveniste,
so exhaustively investigated by Nature, turned out not to provide any
support for homeopathy. They used the quicker, standard mixing technique by
pipette.
Bog iron
The stony nodules created by bacteria found by Max Coleman
(This Week, 19 September, p 25)
were also an important resource for our forebears. In the
absence of ore bodies, they were smelted for their iron content.
A typical instance is found at the Viking site of L’Anse aux Meadows in
Newfoundland. Archaeologists have uncovered the remains of a smelter where about
a kilo of iron was produced during the brief occupation. It was a major factor
in establishing that the site could not be Native American, and “bog iron”
(Coleman’s nodules) was the raw material.
Officially organic
In the final paragraph of your article on farming techniques
(This Week, 5 September, p 13),
you say that the Soil Association certifies Britain’s organic
farmers. In fact, several bodies do this.
The United Kingdom Register of Organic Food Standards (UKROFS) implements the
European Commission regulation governing the production of organic foodstuffs.
In turn, the UKROFS approves a number of certified bodies, including the Organic
Food Federation, Organic Farmers and Growers, the Scottish Organic Producers
Association and the Soil Association. All these bodies operate certification
schemes approved by the UKROFS for certifying organic producers.
Magnetic brake
Pioneer 10 may well be decelerating faster than the theory of gravity predicts
(This Week, 12 September, p 4),
but it is unlikely that this is evidence of an error in the theory.
The outer planets are not behaving in the same way, and this gives a clue
about where the extra deceleration might be coming from. Pioneer is made from
various light metals, and the outer planets are gas giants. When non-ferrous
metals move through a magnetic field they are subject to eddy-current
braking.
On a terrestrial scale the force generated by this phenomenon can be
significant: it is used to supply the initial brake force for passenger coaches
to avoid brake-pad heating and brake fade, for example.
The Sun and many of the planets generate large magnetic fields. The forces
that magnetically induced eddy currents create depend on many things, and in
this case they would depend on the shapes and materials of the parts of the
spacecraft. However, the force generated always tends to oppose the motion
generating it, a bit like friction and viscosity.
Pioneer’s tiny extra deceleration of 80 billionths of a centimetre per second
squared could well be caused by eddy currents. A significant test would be to
see if spacecraft falling towards the Sun fail to accelerate as fast as they
should do. Eddy current braking works both ways.
Danger tests
Feedback
(26 September)
makes fun of a warning accompanying a mains-tester
screwdriver to the effect that it cannot always be relied on to respond.
However, may I repeat this warning to your readers.
I once received a very severe electric shock after using one of these devices
to find out whether an electrical point was safe. It is not as though I am an
ignoramus regarding electrical matters鈥擨 am a chartered electrical
engineer.
The fact is that unless you are reasonably well earthed, it is quite possible
that the indicator will fail to light up. In my opinion the things should be
banned鈥攖hey are dangerous.