Read a good book
Roger French’s letter regarding laptops on aeroplanes (9 November, p 29) had me quaking in my seat and clutching my wallet. Building processing power, screens, keyboards and so on into each seat for the benefit of the few can only eat away at the already inadequate available space and mean higher fares for the rest of us. And if people want to avoid being bored, what’s wrong with a good book?
Antarctic fungi
Plant pathologist Benjamin Held wonders about the origin of the soft rot attacking Antarctic huts (9 November, p 11).
One obvious possibility is that the fungus came with the wood from which the hut was built. At Antarctic temperatures the growth rate of such as fungus would be incredibly slow, but not necessarily zero. Selection for tolerance to cold would be very strong, and 100 years of such harsh environmental pressure could result in the appearance of a cold-adapted strain.
Pluto's warming
Why should it be surprising that Pluto is continuing to get warmer as it moves farther from the Sun (19 October, p 25)?
One plausible explanation is that we are seeing “greenhouse” warming. Once Pluto gets close enough to the Sun for its atmosphere to start to regenerate and thicken, surely any greenhouse gases in the atmosphere, such as methane, will lead to a positive feedback loop: the thickening atmosphere will lead to further warming, and hence further thickening of the atmosphere. This effect might be expected to outweigh the cooling effect of reduced energy input from the Sun, at least initially.
Dinogram?
In regard to the Feedback story on the “agile Stegosaurus” poster at the Society of Vertebrate Paleontology meeting (16 November), it must have occurred to others that “T. R. Karbek” is an anagram of R. T. Bakker, well known advocate of homeothermy among the dinosaurs and author of The Dinosaur Heresies.
For the record
鈥� 1.5-tesla magnets referred to in the story about a magnetic neutron star (16 November, p 22) are used in magnetic resonance imaging, not CAT scans.
Far-out fantasies
It is true that the impact of limiting our production of carbon dioxide will be small and slow (9 November, p19). Even if we were to stop all CO2 production, it would take more than a hundred years for the atmospheric CO2 to return to pre-industrial levels. During that time, the icecaps will begin to melt and the oceans will rise.
But there are probably cheaper ways to counter global warming than building vast structures in space. For instance, it might be possible, at an affordable cost, to cover a few million square kilometres of ocean with white floats to reflect sunlight back into space. This would be cheaper than a Fresnel lens in space of the same size.
And even though solar radiation is stronger in space, it would be cheaper to put vast arrays of solar panels in deserts than to make them in space together with the means of transmitting the energy to Earth.
Letter
Those “far-out” ideas in your article about curbing global warming already make me feel like we have lost hope 鈥� and our sanity. Though the terrestrial environment is becoming more of a risk to our lifestyles, it is still the only environment within which we have a good chance of engineering a solution to our global energy crises.
Without going into the details of how harsh the space environment is and how engineering-intensive these space-based solutions will be, just consider how effective, and comparatively economical, a little education in energy use and global warming would be.
Letter
Breeder reactors are ruled out of the energy supply, partly because of the risk of fuel being used for weapons. Yet analysts appear to have no such problem with another alternative energy system: gigawatt laser or maser beams, the ultimate death ray, directed at the Earth’s surface from a satellite. I am sure the military applications of this system have simply been overlooked. Or have they?
What's a safe dose?
I read with interest the article on retinal damage in rodents fed monosodium glutamate (26 October, p 11). The rats were fed a large amount of MSG. However, I believe that any analysis of MSG’s potential effects on humans must take into account the following published findings.
First, the glutamate was given to rats in food. When people ingest 150 milligrams of MSG per kilogram body weight in a meal, their blood glutamate levels peak at 10.8 micrograms per decilitre. When MSG is given in water, the peak is six to seven times as high. MSG is commonly found in soups and bouillon cubes. This suggests one must divide the dose given to rodents by a factor of 6 or 7 to determine the equivalent glutamate dose in liquids.
Secondly, while blood glutamate levels in humans peak at over 70 micrograms per decilitre for a dose (in water) of 150 milligrams of MSG per kilogram body weight, in rodents given an equivalent dose the peak is only 15 micrograms per decilitre. Thus you might have to divide the dose given to rodents by an additional four or five to determine the equivalent human dose. This might apply to food as well as liquids.
Thirdly, the adverse effects on the retina were noticed after the rodents were on the diet for only three months. While three to six months of regular MSG ingestion might not cause retinal problems in most humans, there may be questions over whether many years of MSG ingestion may cause retinal problems in a subset of the population.
While the latest rat experiment is important, I think it is also important that damage to other areas of the brain unprotected by the blood brain barrier, such as the hypothalamus, have been seen in rodent experiments at MSG doses that could be ingested by children, after adjusting for differences in rodent versus human glutamate metabolism (Nature, vol 227, p 609).
Risk overplayed?
Balancing the benefits of medical irradiation with risk of cancer is an issue of growing importance. There are recognised difficulties in developing informed judgements and communicating them to patients, particularly when cancer predisposition is known or suspected. Your recent article on the risks of mammograms for certain women includes quotes from me and others that relate to this issue (9 November, p 10).
The German researchers quoted have coupled selected radiobiological data on abnormal cells in culture with ill-defined calculations of breast cancer risk to support claims of very high cancer risks from mammography in young women who are genetically predisposed. In my view, these calculations are not at all helpful. First, the radiobiological data used are not representative: other investigators do not judge that low-energy mammography X-rays have such high biological effectiveness (British Journal of Radiology, vol 62, p 910, and Radiation Research, vol 158, p 13).
Secondly, the cancer risk estimate made is unpublished and, given the data available, must make a series of unspecified assumptions about how much more sensitive to radiation breast tissue is in a woman with a predisposition. The calculation, as quoted, suggests that a cumulative dose of 40 milligrays, which would typically be received from 10 mammograms, to the breast of a genetically predisposed woman less than 20 years old would more than double her lifetime risk of breast cancer from, say, around 50 per cent to 100 per cent. In my view, this is biologically implausible, somewhat at odds with a recent epidemiological study (Cancer Causes and Controls, vol 13, p 711) and extremely difficult to reconcile with the fact that by the time a woman is 40 years old she will have accumulated a similar dose from natural background radiation.
And is a medical scenario which assumes 10 mammograms before age 20 at all realistic?
Keep the cats
I do not dissent from Tony Green’s view that some cat owners should show more responsibility in controlling their pets’ activities (16 November, p 24). However, he is obviously unaware that the benefits to human health of keeping a pet far outweigh any harm that may arise.
Numerous well-researched studies have concluded that pet owners suffer significantly fewer health problems 鈥� particularly depression and heart disease 鈥� than non-owners. Given that about half the population have pets in their household, the positive effects of their existence must be enormous.
Green should accept that even in terms of his cold-hearted logic, the responsible keeping of pets should be encouraged.
Letter
Green’s argument that getting rid of cats would save a lot of small mammals 鈥� as well as protecting us from Toxoplasma gondii 鈥� ignores the reason cats were domesticated in the first place. They act as very efficient biological controls for these rodents, many of which did (and often still do) greater harm to humans than Toxoplasma.
Kyoto and forests
Your article on tree farms gives the false impression that CO2 released when land is prepared for reforestation is ignored by the Kyoto Protocol’s accounting procedures (26 October, p 10).
In fact, the monitoring conditions outlined in the Marrakech Accords and the accounting rules set up by the Intergovernmental Panel on Climate Change require net accounting of all greenhouse gases. Thus the CO2 released by soils following land preparation would be considered before assigning carbon sink credits.
The article also suggests, correctly in many people’s view, that conservation is more effective than replanting. Unfortunately, largely for political reasons but also for some practical ones, forest conservation is not included in the first commitment period for Kyoto. That could be revisited later.
Letter
Riccardo Valentini’s reported claim that the Kyoto Protocol “has no measures to stop deforestation” is incorrect. Article 3.3 of the protocol requires accounting for net emissions and sequestration from deforestation as well as afforestation and reforestation. Article 3.7 requires countries with a net source of emissions from land use change and forestry in 1990 to include these emissions in calculating the baseline against which targets for CO2 reduction are measured.
Benign cannabis
I am distressed once again to read an article that compares the effects of smoking cannabis to the effects of smoking tobacco, without exploring the alternatives to smoking (New 杏吧原创 online news, 13 November). The brief mention given to Corporate Pharma’s smoking alternatives such as under-the-tongue spray (very high-tech, very profitable) completely ignores one alternative that is enjoying increasing popularity.
That is to deliver cannabis via a simple vaporiser. This completely mitigates the harmful effects of carbon monoxide, tar and benzene, while delivering the healthful benefits of THC and other cannabanoids.
Your article also fails to ask the obvious question of why cannabis is typically held in the lungs longer than tobacco. I suspect that if cigarettes cost $5 each and were illegal, nicotine addicts would turn themselves blue in the face as their lungs gleaned every last molecule of drug from the smoke.