Triggering eruptions
While rain may well destabilise volcano domes under pressure from the magma below (7 September, p 4), could another factor associated with heavy rain also play a part? Heavy rain is normally associated with a deep atmospheric depression. This reduction in atmospheric pressure might perhaps be the final factor upsetting the pressure equilibrium of an already critically pressurised dome.
Adrian Matthews writes:
鈥� The decrease in atmospheric pressure associated with a weather system is unlikely to be significant in triggering the collapse of the volcanic dome, compared to the intense rainfall. Changes in surface atmospheric pressure are of the order of 1000 pascals. This is negligible compared to changes in pressure inside the volcano, which are of the order of 1,000,000 pascals or more.
Fungi or algae?
I got my botany degree two years ago, so I could be out of date, but I was taught that Phytophthora was a fungus (14 September, p 9).
The Editor replies:
鈥� Phytophthora were traditionally classified as fungi, and are still often included in mycology classes because of their functional similarity to fungi. However, some years ago they were reclassified as members of the Stramenopile kingdom, and are closely related to brown algae, or phaeophytes. However, they are not themselves algae, as we incorrectly reported, but are properly referred to as oomycetes, or water moulds.
Geranium detectors
Feedback mocks the humble geranium and detectors made from it (31 August). But try browsing the website at , for example, and you will find a description of how an extract from a geranium plant can be used in a device to determine relative humidity, used in meteorology. The signal from the geranium is, as it happens, processed by a silicon chip to determine the result.
I have never seen any reference to the relative humidity in the vicinity of orbiting satellites. But something must happen to the water vapour in the efflux from all those thrusters that satellites use.
Computer music
Your article on converting computer code into “music” in order to spot bugs (7 September, p 13) reminded me of the time around 1973 when I was working as a programmer at the Laboratory of the Government Chemist in London.
We found by accident that signals from the lab’s computer could be picked up clearly by a radio placed on top of the cabinet. We noted the different kinds of noises produced by things like repeating loops, sending and receiving peripheral data, and moving chunks of data around. We subsequently employed these noises as both a debugging aid and as a kind of system monitor.
Letter
In 1970 I was involved in writing test software for checking the reliability of prototype ICL 2900 mainframes. There was no way of monitoring the progress of tests until one of the hardware engineers had the idea of tuning a radio to a frequency leaking from the processor unit. Thereafter we were able to listen to the tests. After a short learning period we were able to both identify tests and recognise if they were running incorrectly, saving many hours of testing time.
Fruit repels
So Babar the elephant was aware that tomatoes could be used as an insect repellent (24 August, p 27). I, too, have developed a fruit-based mosquito repellent, which I published with Mike Davies in our book Exotic Cooking in Greece.
Since we live in Greece, we use olive oil as the base and boil up various citrus skins and leaves in it. It has a pleasant smell and we find that it works extremely well. We would love to have others try it and give us feedback on its effectiveness.
For Paula Scott’s mosquito repellent see the extended version of this letter on our website.
Designer roll
I watched the first 360-degree barrel roll used in The Man with the Golden Gun when it was first attempted at the Houston Astrodome.
The one thing you did not mention in your item on “stuntology” (24 August, p 49) was that the driver of the car was the guy who did the computer modelling of the car dynamics. Since no one else was willing to drive the car, he volunteered. His speed was just a bit off, and the landing was not perfect, but it worked. He was the only one prepared to take the risk.
From puer to poo
Tony Covington derives the word “puer”, as applied to dog dung used in tanning, from the Latin puer, meaning “boy” (31 August, p 27). Surely a more likely derivation is from the French puer, meaning to stink, which is still enshrined in the nursery-speak affected by those adults who persist in referring to human excrement as “poo” or “poop”. A tanner would be more likely to have remnants of Norman French in his speech than a knowledge of Latin.
Blackest black
The discussion about varying shades of black is quite an important one in the theatre (31 August, p 27). Between scenes, stage hands, stage managers and technical staff need to be able to move around unseen by the audience. They have to wear the right shade of black, however, as many black clothes will appear dark red under the small amount of blue light that filters through from backstage. Professionals often take a blued-out torch with them when shopping for black clothing for use at work.
For the record
鈥� The researcher pioneering gene therapy to treat hair colour (“Gene tweak will banish bad hair days”,14 September, p 16) is Robert Hoffman, not Ronald Hoffman as we said in the story.
Lasers that blind
We read with great interest your two articles about laser weapons (27 July, p 4, and 7 September, p 5). We very much welcome updates on developments in laser weapons and, in particular, the problem of laser systems that could permanently damage eyesight.
As the authors indicated, laser weapons specifically designed to cause permanent blindness are prohibited. However, contrary to what you state in the second article, this prohibition is not part of the Geneva Conventions of 1949. It was, in fact, adopted in 1995 as Protocol IV to the 1980 UN Convention on Certain Conventional Weapons.
While laser systems which are not specifically designed to blind are allowed on the battlefield, states are required by Article 2 of Protocol IV to take all feasible precautions to avoid causing permanent blindness through the use of such systems.
Thus any armed forces intending to use a 100-kilowatt laser against material targets would have to ensure that precautions are taken to minimise the risk of indiscriminate effects on civilians and of permanent blindness to soldiers.
Letter
So someone thinks that the laser weapon is unsafe because cumulative exposure can lead to long-term effects. I assume from the tone that your expert is unaware that the damage caused by the impact of a high-velocity military rifle round is much more serious and generally just as long-lasting (not just a little hole, like in the films).
This equipment could well save a lot of lives, even if the brave soldiers who stare at it unblinking for some time before escaping, have a vision deficiency later in life.
Deconstructing safety
The use of deconstruction philosophy may be helpful in drawing up guidelines on how safety texts should be written, but it would be a cumbersome tool for analysing long technical documents (7 September, p 12).
Part of my own engineering work is concerned with writing patent applications in my native tongue, English. If I need to extend patent protection to France, I have to use a professional translator who speaks good technical English but whose native tongue is French. No matter how carefully I craft the wording of my patents, the translator still finds some ambiguity.
This suggests a simple way of identifying ambiguities in safety documents: work with a technical translator, who would translate the document into another language. A second translator could add a higher level of refinement by translating the new document back into the original language.
Letter
Deconstructionism provokes a series of questions in the mind of the observer so as ultimately to raise the question: what is the relevance of anything? The aim is to dissolve the preconceived sense of absolute meaning in the obvious answers to this series of questions, so that the observer starts to drown in uncertainty. If this methodology is applied to a technical document, it can only result in uncertainty 鈥� the true aim of deconstructionism.
If the procedure proposed by Jim Armstrong is to operate logically, then he must define the term “meaning”, so that he can stop the deconstruction process when meaning has been arrived at. The snag is that deconstructionism aims to show that this can never be done.
Focus on nerves
Writer’s name supplied
The article on engineering penile tissue was very interesting indeed (14 September, p 14). I write with personal interest because I suffered complete amputation of my own penis and the destruction of my testicles some years ago following trauma which led to necrotising fasciitis, an infection which can also be a barrier to reconstructive surgery. The same accident also led to the loss of one of my limbs, so I can write with some feeling regarding such surgery.
And feeling is a direct and relevant consideration. None of the reconstructive techniques offered to me over the years for replacing my penis was able to guarantee even partial neural function. Replacing a totally absent penis using bio-engineering, but without full neural function, would achieve results no better than those available now through reconstruction, except of course that the organ would look perfectly natural.
The researchers should concentrate instead on growing or regrowing nerves to order. After all, despite being sexually disabled I don’t have to have 24-hour care and rely on a respirator, unlike those people who have suffered a severed spinal cord. Nothing would please me more than to hear that neural function has been restored to someone with a serious spinal lesion, enabling them to breathe normally once again or regain movement. Only then would I ask them to try to help the 100 or so men a year who end up in the same situation as myself.
Address supplied
Rebuilding ourselves
Douglas Fox suggests humanity is heading for extinction because the Y chromosome is fading away (24 August, p 28).
His analysis ignores one extremely important upcoming technology: within 50 years鈥� in other words, within 1/100,000th of his envisioned 5 million years鈥� we will probably be able to spruce up that Y chromosome to whatever extent we wish. We will be able to turn it upside down, inside out, add bacon and eggs to it, make it glow purple in a dark room, and modify it to work in the herds of flying pigs that we shall doubtless have at that point.
Our natural evolution is just about to come to a screeching halt, and we will be the architects of our own species long before 5 million years are up. Living systems are horrendously complex, but they are not infinitely complex. We’ll have it pretty well figured out within a small number of generations, I would imagine.