A way with waste
The article by Rob Edwards regarding the Basel Convention on the transport of waste (“Dirty tricks in a dirty business” 18 February and Letters 18 March) unfortunately contains errors. For example he refers to a leaked document from this organisation, dated May 1994, in a context that implies sinister intent. The document was never secret but widely distributed.
Industry supports the legal, environmentally sound management of transboundary movements of materials for legitimate recycling purposes. We oppose disposal operations masquerading as recycling. We support a legitimate trade and environmentally sound processing of secondary materials, all of which benefits both exporter and importer.
This organisation took the unusual step last May of reversing its previous strong support for the Convention and for US implementation and ratification. We still strongly support the Convention as a means of bringing environmental protection and rationale to trade in hazardous wastes. However, the present decision to ban shipments of materials for recycling from OECD to non-OECD countries 鈥� no matter what its legal status 鈥� will contravene good intentions and harm the economies of the countries who need to be able to afford environmental protection. It will leave intact the trade in such materials among non-OECD countries, which is considerable.
Worldwide industry has made, and will continue to make, proposals as to how the convention can assure benefits from trade and recycling, and that the recycling is legitimate and environmentally sound.
Skin repairs
May I respond to the article by Dickman and Strobel about tissue reconstruction (“Life in the tissue factory”, 11 March and Letters, 1 April)? I am quoted as saying that collagen-based skin substitutes are “non-starters”. However, in the light of our clinical research, such grafts can be moderately successful, even to the extent of some allogeneic cell survival.
Our work used patients electing for tattoo removal, so that the tissue fabrication was done to order and the patients were able to receive the operation at the graft’s convenience, so to speak. These operations resulted in good cosmetic effects with little scarring and virtually no wound contraction. Repigmentation was more variable.
The comments quoted from me in the article related to our (as yet unpublished) preliminary studies on the use of collagen-based skin substitutes in burned patients. By their nature such wounds are highly active enzymatically, and grafts may suffer further if infection occurs. I repeat that in a burn wound condition, native collagen is hard put to survive these biological insults, and we are “back to the drawing board”.
That is not to say that in the final analysis, some form of collagen, as the major extracellular protein of the dermis, will not have a future in skin replacement. However, the advances in biopolymers may enable some skin substitutions to be “artificial”, or they may not. Time will tell, and there may yet be life for collagen.
One mystery
The variation on Young’s slit performed by Raymond Chiao et al, reported by John Gribbin (New 杏吧原创, Science, 11 March), does not deepen the mysteries of quantum physics at all, but rather confirms that there is one mystery and one only: non-locality.
According to classical electromagnetic analysis, the wave at the second screen has an intensity corresponding to the “no interference” case, but it is linearly polarised with an orientation that varies cyclically across the width of the pattern. The linear polariser therefore simply resolves the beam into two, complementary, interference patterns, only one of which is transmitted.
Thus individual photons also emerge from the slits with a polarisation that is correlated with the angle of deflection. Of course, the interaction at the slits must be non-local: the photon reflects with the slit screen as a whole. The mechanism for this kind of thing is the mystery behind quantum mechanics.
However, a photon does not need to know what lies in store for it in the future 鈥� there is no need for further mystification. It simply emerges from a single slit (not both) with a fully determined polarisation that equips it to decide how it will behave if it happens to encounter a linear polariser 鈥� or any other “trap” set for it 鈥� some time later.
Perhaps the photon does not need to “know” after all 鈥� if one forgets, that is, about the Copenhagen interpretation of the particle-wave duality and one adopts instead some version of De Broglie’s concept about quantum particles having associated waves.
In the latter type of interpretation, one can imagine that the collapse of the wave function in the presence of the circular polarisers, which in turn leads to the disappearance of the observed interference pattern (if the eraser is not there as well), should not necessarily mean a disappearance of the wave itself.
It may mean, for instance, only a decoupling between the particle and the wave. So, while the wave itself may still exist and still experience an interference after the slits, the detectors at the second screen would detect only the particles, unaffected by the interference.
On the other hand, when the eraser is also present, it may produce a re-coupling of the particle to the wave pattern, and now the position of the particle will again be determined by the wave-function. Since the wave would always create an interference pattern after the slits, so will the positions at which the recoupled particles interact eventually with the second screen.
This explanation would eliminate the puzzle of the prescient photon and in general, there is nothing about the above assumptions that would contradict the mathematics of quantum physics. The only thing that changes is the interpretation.
Surely it is relativity theory which is thickening the plot? Einstein’s special theory says that time does not exist for an entity travelling at the speed of light.
So to a photon, its birth, its journey through the apparatus, and its death in the measuring device are all simultaneous. There can be no doubt, therefore, that the photon is “aware” of all parts of the apparatus, and proves that this is so when any portion is altered.
The above would be true even if half the apparatus were on Alpha Centauri.
It is probable that interchanging the linear and circular polarising filters in the experiment described would make no difference either.
The spatial position of the obstacles, provided they are actually accessible to the photon, is not relevant because the terminal velocity c is involved, where time stands still.
Square hexagon
The French do not say “from the 4 corners of a hexagon” (Forum, 25 February) but 鈥� of the hexagon” meaning France, because of its shape. Children learning to draw a map of France are taught to start drawing a hexagon and then to fit in the map, having thus the approximate shape and good proportions; for all French people “the hexagon” is a synonym of France. The 4 corners are of course North, South, East and West. So “from the 4 corners of the hexagon” means “from everywhere in France”.
Message mission
Jon Lomberg and I were extremely pleased at your enthusiastic endorsement of the Cassini/Huygens “message” idea (Comment, 18 February). We hope we encounter no major obstacles in pursuing this idea, and would therefore appreciate some correction of the errors accidentally reported in your article.
In brief, the Cassini mission consists of the Cassini orbiter, named after the Italian/French 17th-century astronomer who studied Saturn’s rings, to be placed in orbit around Saturn, not Titan as mentioned in your article; and a smaller probe, named after the renowned 17th-century Dutch physicist and discoverer of Titan, Christian Huygens, to be dropped early in the mission into the atmosphere of Saturn’s largest satellite Titan.
Titan is a Mercury-sized object with an atmosphere consisting primarily of molecular nitrogen with smaller amounts of other gases like methane (as you reported), but the nature of its surface is still a matter of intense dispute. At the present time, the radar data do not seem to admit the possibility of large, Pacific-like oceans (as you reported), but rather small Mediterranean-like seas (if any) of liquid hydrocarbons. I am sure, though, that some scientists would disagree with this statement as well.
Impact of print
I was intrigued by Timothy May’s analogy between the latter-day impact of the Internet and the impact of printing on medieval guilds (“Identity crisis on the Internet”, 11 March).
May’s view that the guilds began to decline as the arrival of printing spread the knowledge of their skills, while seeming plausible, does not seem to hold true for England at least. Printing began in England in the late fifteenth-century; and whilst “How to 鈥�” books on being a gentleman, a farmer, a husbandman, a midwife, an angler, a cook and so on can be traced quite far back, the first instruction books on guild trades don’t appear in any numbers until well after the Restoration.
The first practical treatise on printing itself, for example does not appear until 1678, reflecting a decline in English guild strength that was probably more a consequence of economic changes than anything to do with printing.
May may very well know something about the Continental guilds that I don’t, but I would be surprised to find such an effect anywhere 鈥� the system of apprenticeship, for one thing was so assimilated into the society of the period that book-taught tradesmen would have found it hard to find anything approaching social acceptability before the end of the seventeenth century at least.
Whilst the whole “The-Internet-is-the-biggest-thing-since-printing” line is moot in itself, it would perhaps help if we could all agree about what, exactly, the impact of printing was in the first place.
Correction
An error crept into Feedback’s story about a school chemistry experiment (25 March), turning liquid nitrogen into liquid hydrogen.
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Crammed into boxes
Colin Tudge says anthropomorphism, “if used carefully”, can help us understand animals (Forum, 11 March). Perhaps, and to a limited degree. But then he goes on: “We know that we would suffer if crammed in a lorry and sent across the sea.”
Yet every year millions of Britons cram themselves into crowded boxes (cars, planes, trains) to go to Europe, and pay for the privilege. Quite obviously we do not “suffer”: possibly some of us experience mild discomfort. If you are going to insist on anthropomorphism you have to conclude that calves do not suffer either.
A more plausible hypothesis would be that it depends on the exact conditions. For humans, knowing why and where we are going is crucial. But it’s rather unlikely that this condition is crucial for calves. Perhaps lighting, temperature, or density of packing may be the crucial elements for them. Who knows? Tudge doesn’t discuss this kind of issue; he seems to have decided in advance to believe that the calves (unlike us) suffer 鈥� except, mysteriously, if the journey last less than 2 hours. How does he know this?
As far as we know, a sense of security could be the crucial factor for calves. Conceivably, the close presence of other calves is reassuring. Perhaps they are happier with a longer journey because it gives them time to become familiar with the strange conditions. None of this is very likely but who knows?
If he wants a more plausible complaint about the way we treat cows, Tudge might start campaigning against the human consumption of cow’s milk. The separation of calves from their mothers is almost certainly distressing to calves and cows alike, yet it is fundamental to the milk trade. Of course, as a campaign subject it has a disadvantage: instead of putting the ultimate blame on the wicked French you’d have to point the finger at wicked English mothers and their fiendish kids.
The ideal would be to reduce the number of veal calves to those figures demanded by home consumption and exported carcasses. Careful separation of male and female sperm during treatment of semen could go a long way to achieving the above in a manner where all would benefit.
The farmer would be rearing a higher percentage of heifers, all yielding dairy products throughout their lives and useful meat when slaughtered. Separated sperm would be expensive, but the reduced cost of policing riotous crowds would more than compensate.
Perhaps the agriculture minister William Waldegrave could start the ball rolling by using separated semen from his herd and reducing his quota of bull calves.
Killer dust
Around 150000 British citizens will die from asbestos-related diseases (mainly lung cancer, mesothelioma and asbestosis) in the next 30 years (This Week, 11 March). Why? You say that the reason was, “A disastrous miscalculation by the British safety authorities in the 1960s 鈥�” But the 1898 Annual Report of HM Inspector of Factories wrote in detail about the “evil” effects of asbestos dust.
So how do we come to have this massive, and preventable, epidemic of asbestos-related disease? One simple word: profit. It has been very profitable to push this deadly dust into all our lives (schools, hospitals, homes and work-places) over the past 100 years until very recently.
Amazingly, 5000 tonnes of asbestos is still imported into Britain each year; there are even indications that some sales are rising (for example, roofing slates). Use in the “developing” world is growing, while Denmark, Germany, Holland and Sweden have banned the use and import of asbestos.
In 1993 a 36-year-old single parent schoolteacher, Shirley Gibson, died of the asbestos cancer mesothelioma due, an inquest found, to a 10-year exposure to low levels of asbestos dust at her school. We urgently need a public enquiry on the dangers of asbestos, or I fear the deaths will carry on much longer than 30 years.
Milk on demand
I was interested to read about Ronald Barr’s studies on the cultural differences in breast-feeding routines and crying in babies (This Week, 4 March). Perhaps the “endless crying and battles to establish sleep patterns” are not as ubiquitous as was once thought because since the 1960s (and probably before) many Western mothers have chosen the halfway house of “demand feeding”.
In 1965, when my first child was born, 1 decided to demand feed, then a popular option. This did not turn out to be “continuous” feeding, like the !Kung San mothers, although it could perfectly well have been. Instead, within a week of getting home I was giving between 5 and 7 feeds a day, most of which fell into the daytime period; by five weeks our daughter had on average 4 to 5 feeds per 24 hours and slept a perfectly reasonable “night” of 6 to 8 hours (which quickly extended). She was 6lb 6oz at birth and gained weight normally: she was a very active, but contented baby, hardly ever crying.
It seems that our Western babies, when given the option of continuous feeding, settle into an easy pattern of “demand”, which could be very close to the more rigid regimes but has the flexibility of more frequent nutrition, as with the !Kung San mothers, if the baby wants it.
It is obvious that parental attitudes affect babies’ behaviour, but the inflexibility or otherwise of parental views in response to social custom seems to be what counts most. As a baby I was fed every four hours “on the dot” and was “very difficult”. I had to be woken for some feeds that I then did not want, and cried mightily for others but had to wait. It was unhappy for everyone and I was not keen to have such an experience with my children.
I have often been struck by the relative inability of more regimented friends to “give in” to crying, whilst the “demand” mother happily fed in any circumstances, with no angst. If demand feeding could be advocated as an option for breast-feeding mothers, then Barr need not conclude that Western babies will continue “to cry a heck of a lot more” than the !Kung San infants.