Placebo effect
In our recent meta-analysis, Guy Sapirstein and I asked what proportion of
the therapeutic effects of antidepressants can be attributed to a placebo
response. Though mostly accurate, your coverage of this analysis gave the
impression that the difference between the claims made in our study and those
made by the drugs companies is bigger than it really is
(Editorial, 11 July, p 3
and This Week, p 13).
If 75 per cent of the drug response is a placebo effect, as our study found,
then the advantage of drug over placebo is 33 per cent (25 divided by 75), not
the 25 per cent that you reported. The drug companies claim a 40 per cent
advantage to drug over placebo. That translates to about 71 per cent of the drug
response being a placebo effect and 29 per cent being a drug effect (because 29
is 41 per cent of 71). This is very close to what we found.
Helium through heat
One of your summer features states that two hydrogen atoms are consumed to
form helium in the Sun
(“Final summer”, 25 July, p 40).
This statements is incorrect. Hydrogen atoms consist of a proton and an
orbiting electron. However, in the Sun’s interior, high temperatures would
ionise the atoms into protons and free electrons. A combination of heat and
pressure and momentum would then overcome the coulombic repulsion of like
positive charges causing the fusion of two protons by the strong force. One of
the protons would then eject a positron and be converted to a neutron, thus
forming deuterium.
Two deuterium particles would in turn fuse to form helium (two protons and
two neutrons), releasing energy and consuming four hydrogen atoms, not two.
Projects@home
Readers fascinated by Hazel Muir’s article about using volunteers’ home
computers to hunt for alien life might be interested in taking part in other
Internet-based distributed processing projects, while they are awaiting the
start of SETI@home
(“First contact”, 25 July, p 46).
Ongoing projects include the Great Internet Mersenne Prime Search
(http://www. mersenne.org/prime.htm), the Optimal Golomb Ruler Search
(http://members.aol.com/golomb20/index.html), and PiHex, for calculating pi
(http://www.cecm.sfu.ca/projects/pihex/pihex.html).
There are also a number of prize cryptography challenges, which aim to
demonstrate the security (or otherwise) of various encryption systems. By far
the largest distributed cryptography project is distributed.net’s attempt to
crack the RC5-64 Challenge. Information can be found at
http://www.distributed.net/rc5/. This project is arranged in teams. The
fastest British team (“Prof James Challis’ Most Excellent RC5-64 Team”) has its
homepage at http://www.cix.co.uk/~rigel/rc5.htm.
On your bus
Feedback
(1 August)
complains about Railtrack’s website and some of the
problems experienced with it. We have also had some strange routeings and
timings when using the site to look at journeys for colleagues coming to
Bradford from King’s Cross in London.
One particular jouney (using the 9.10 from King’s Cross to Bradford) puzzled
us, as it said to change at Wakefield. The puzzlement occurred because there is
no train route from Wakefield to Bradford. Further inspection of the journey
details showed that the chosen routing involved using a bus to get from
Wakefield to Bradford, as opposed to the usual train route changing at
Leeds.
The puzzle became rather clearer, though, when we saw that the company
providing the bus was GNER, the same company that provides the London to Leeds
rail service, whereas the Leeds to Bradford rail journey is provided by a
competitor, Northern Spirit (formerly Regional Railways North East). Perhaps the
website has a preference for the same company rather than the best journey?
Incidentally, the Deutsche Bahn website (http://bahn.hafas.de/english.html)
has reliable Europe-wide train information鈥攊ncluding that for Britain鈥攊n
English, which actually uses trains rather than buses. Guess which one we use?
Turbulent turtles
Feedback
(25 July)
reported the case of a pilot who couldn’t take off because
there were turtles on the runway. But what if he couldn’t land because there
were turtles in the sky?
The Roman army had a saying that you should never pitch camp in the lee of
hills when there were turtles in the sky. These turtles were in fact lenticular
clouds formed by lee waves when strong winds blow across lines of hills under
unstable atmospheric conditions. In Britain they can be seen quite frequently
and are used by glider pilots to soar in the rising air along the leading
edges.
The Romans encountered the associated problems of extremely turbulent rotor
flow at ground level under a wave peak. If the camp were at the position where
the air is descending, compression can cause higher local winds than general, in
a venturi effect. Both can wreak havoc to a tented camp site or an aircraft.
On 5 March 1966 a BOAC Boeing 707 broke up in rotor flow turbulence while
flying in the lee of Mount Fuji, Japan, with the loss of 124 lives.
Severe damage was done by compression flow in Sheffield, in the lee of the
Pennines, during a gale on 16-17 February 1962. Three people were killed and 250
were injured, while 7000 properties were damaged.
So, as they did back in Roman times, watch out for the turtles.
Teddy therapy
Your article about the fly swatter being used against the frustrations of
office machinery has hit a familiar chord
(Feedback, 25 July).
In our department we have a teddy which plays a similar role. Poor Ted
carries the name of whichever senior academic is currently wearing the head of
department’s crown. As heads of department occasionally behave like mentally
unhinged prima donnas, support staff have no alternative but to take out their
frustrations on Poor Ted. It gets kicked around the corridor, punched, thrown
against walls and even chucked out of the window. However, every now and then a
member of staff takes pity on it and it ends up on the shelf with its arm in a
sling or a bandaged head.
Fortunately, these heads of departments are unaware of this valuable member
of staff.
Adjectivally challenged
Simon Casey points out that New Zealanders have no adjective to describe what
is theirs, and wonders if there are others thus deprived
(Letters, 1 August, p 49).
The inhabitants of the US have no true adjective of their own, but subsist on
goods stolen from their neighbours. Any cartographer would agree that “American”
should be the adjective for the whole region from Canada to Chile, but the
larger part of this region have been deprived of a merited adjective to satisfy
the needs of a subsection.
Letter
When Czechoslovakia broke up into Slovakia and the Czech Republic, my aunt
noted that some people could be “Slovakian”. But were the others “Czech
Republican”?
Letter
I disagree that there is a lack of an adjective related to insects.
“Creepy-crawly” is used universally, even as a noun. It is of course shunned by
scientists because it indicates a failure to count the number of legs. Thus the
term is broad enough to encompass everything from maggots through spiders to
millipedes.
Beach life
Fred Pearce asserts that Britain’s beaches and coastal waters are becoming
too clean
(“Washed up”, 25 July, p 32).
In publicising some interesting research findings on the adverse ecological
effects of mechanical cleaning on sandy shores, he also takes the opportunity to
propose that the considerable effort expended in recent years to reduce the
inputs of sewage-derived organic material to estuaries and coastal waters is
misguided and is leading to undesirable environmental changes.
In gathering support for this thesis, the principal concern expressed is over
the decline in the number of various bird species. I find this a curious and
rather dated approach. An emphasis on the benefits for one group of organisms
ignores the wider effects on other aspects of biodiversity.
Surely a more modern holistic approach would take a balanced view of the
effects of reductions in the input of sewage and sewage effluents on the whole
system. Take, for example, one of the negative consequences of supporting this
organic enrichment in estuarine environments: sewage discharges into estuaries
often create severe oxygen sags in the upper estuary, leading to fish kills and
posing a barrier to the passage of migratory fish. Several of these fish species
have a similar legal status under European legislation to that of the birds for
which Special Protection Areas are being designated in estuaries.
Reductions in sewage inputs to estuaries usually improve the conditions for
resident and migratory fish. Is this a more or less desirable outcome than
supporting populations of some bird species through enhancing certain of their
prey species?
There are other outcomes of sewage-derived organic enrichment which are
undesirable if a wider view is taken. Sewage may indeed provide a food source
for cockles, mussels and other commercially important molluscs. Experience
suggests, however, that contamination by sewage-derived bacteria can create a
health-related barrier to their commercial exploitation.
Surely the days of promoting environmental management to support single
interests are waning.
Letter
The blame placed at the door of the Marine Conservation Society for the
sanitisation of beaches and overzealous removal of debris is misplaced.
The society coordinates Beachwatch, a campaign to monitor litter levels on
British beaches and target the polluters to clean up their act. This has been
highly successful in raising awareness about the impacts of litter which, if
left in the marine environment, can entangle wildlife and also cause damage if
ingested. The campaign involves thousands of volunteers in manually collecting
litter from beaches, and promotes community initiatives for beach cleaning
rather than mechanical beach cleaners.
The society asks that all organic matter be left in place, including seaweed
and driftwood, which provide important habitats for marine fauna and flora.
We too are concerned about the growing desire for pristine beaches at any
cost, but, as ever, prevention is better than cure. The levels of litter
recorded today on our beaches are a legacy of our throw-away society. The
problem is not so much how it should be removed, but how we can ensure that
litter is not there in the first place.
Dope versus cancer
Michael Roth’s “preliminary evidence” suggesting that the THC in marijuana
may promote a carcinogenic effect
(This Week, 25 July, p 16) flies in the face
of Louis S. Harris’s findings inAnalgesic and Anti-Tumor Potential of The
Cannabinoids (Medical College of Virginia, 1972) that delta-8 THC, delta-9
THC and cannabinol are quite active as anticancer agents.
At the time of Harris’s research, no anticancer agent that was much more
potent than delta-9 THC existed and no compounds differentiated between tumour
and normal cells the way delta-9 THC does. Considering that delta-9 THC alone
increased survival in cancerous rats by 36 per cent, it seems very unlikely that
THC promotes carcinogenic effects.
THC’s known anticarcinogenic properties are probably the reason the Center
for Disease Control in Atlanta, Georgia, has never been able to trace any
cancers to marijuana use.
Fewer, longer lives
Your interesting piece on the “population bombshell”
(Inside Science, No 112, 11 July)
reminded me of a correlation I’ve never seen mentioned in any article
on population. I came across it accidentally when testing a graph-plotting
program some years ago.
The data I used came from the World Bank database that was then located at
the University of Bath. It consisted of tables of annual data for the 27 years
stretching from 1960 to 1986, for each of 120 countries, for various variables,
including some population variables.
Plotting the fertility ratio (number of children per woman) against life
expectancy at birth showed a very strong relationship between the two variables.
Fertility always reduced as life expectancy went up.
Whether it was industrial countries, agricultural, First World, Third World,
Catholic or non-Catholic, individual countries or all countries lumped together,
annual data or 27-year means, the exact correlation might vary but there was
always a very strong relationship. For the pooled data, the crossover point
where fertility went below the replacement rate of 2.1 children per woman was a
life expectancy of 79.5 years.
Finding a correlation between two variables does not prove that one drives
the other (both could be driven by something else), but it would make a kind of
sense if life expectancy did influence the fertility ratio. If life is short and
people tend to die young, there would be strong psychological pressure to have
children as soon as possible. Conversely, if people survive for many years, then
children can be postponed. It seems probable that the older people are when they
start having children, the fewer children they are likely to have.
If fertility really is driven by life expectancy, this has profound
implications for aid programmes and population control. It would mean that it’s
not the aluminium smelter or the big dam that matters, but rather the
unglamorous sewage systems, clean water, health services, affordable food,
decent shelter, and anything else that leads to an increase in life span.
Unfortunately the data I have end in 1986. I would be most interested to see
comparable data for more recent years. I would really like to know if the
relationship has remained as strong.