News & Views in 1997

George Orwell once said that the purpose of light music is to prevent you thinking. Daedalus agrees, and he is devising a way of filtering out unwanted background music. The idea is to create a circuit that can distinguish between speech and music. Music has regular peaks at the intervals of the musical scale, and it should be possible to generate a circuit that detects and responds to this pattern. Any sound with the tell-tale musical periodicity in its power spectrum could then be cut out.

How does consumption of meat products infected with bovine spongiform encephalopathy (BSE) lead to development of Creutzfeldt-Jakob disease (CJD)? Studies of the brain, spleen and marrow of many immunodeficient mouse lines indicate that differentiated B lymphocytes are important for neuroinvasion. This discovery has implications for therapies against CJD, and also for the broader public-health issue of screening blood products against possible infection.

Whether or not plant cells contain the growth factor cyclic AMP has been a source of controversy for over 25 years. Now, characterization of an enzyme that produces cAMP and mediates the action of the plant hormone auxin marks a decisive defeat for the majority view.

Quantum chromodynamics describes the colour force, which binds quarks and gluons into neutrons and protons, and binds them together in the nuclei of atoms. The colour force is very strong, very short-range (less than 10-16 m) and very complicated — eight different fields respond to the presence and motion of three types of charge, each of which can be positive or negative. Remarkably, we can now observe coherent effects in the colour force, where the fields from two or more particles overlap and reinforce one another.

When, where and why was the two-humped Bactrian camel first domesticated? A new analysis tackles these issues, drawing on a variety of archaeological evidence (and including discussion of a translation of a twelfth-century Chinese manual on camel husbandry). The answer to the first question remains pretty much a mystery. As to the second and third, the authors surmise that the likeliest answers are Kazakhstan, northern Mongolia or northern China, and for meat.

Quantum chromodynamics describes the colour force, which binds quarks and gluons into neutrons and protons, and binds them together in the nuclei of atoms. The colour force is very strong, very short-range (less than 10-16 m) and very complicated — eight different fields respond to the presence and motion of three types of charge, each of which can be positive or negative. Remarkably, we can now observe coherent effects in the colour force, where the fields from two or more particles overlap and reinforce one another.

Clues to our past climate can be found in marine sediments. The ratios of different oxygen and carbon isotopes within the buried shells of marine creatures depend on water temperature, among other things. But it now seems that they also depend on the total concentration of carbonate in sea water. For many periods, these palaeoclimatic codes will now have to be deciphered again — lowering our estimate of temperatures during the last ice age, for example.

This week Daedalus wonders how to make an artificial solar eclipse, and concludes that it should be possible to do so by obscuring the Sun with a high-flying circular shutter. His ‘Eclipsat’ will orbit the Earth at a height of 1,000 km, producing a solar eclipse every 105 minutes along a track 5 km across and up to 8,000 km wide. It should also be able to generate an ‘anti-eclipse’, reflecting the Sun down onto a narrow track on the dark side of the Earth.

The difference between men and women could be getting smaller, according to a paper that describes a function for female hormones (oestrogens) in the male reproductive tract. Mice that lack the gene for the a form of the oestrogen receptor are infertile, and this turns out to be due to a defect in the process by which sperm are prepared for storage in the testis. Usually, storage involves resorption of fluid from around the sperm, but, in the knockout mice, more fluid is secreted. So the effects of female hormones in males may actually be widespread.

A common consequence of large-scale oil spillage in coastal waters is the fouling of marine birds; a common response is to clean those birds that survive the initial incident, and release them back into the wild. Two papers, analysing British and Dutch data on the rehabitation of oiled guillemots, show, however, that such cleaning endeavours are largely doomed to failure — they respectively report that only about 1% and 20% of the birds survived their first year after release.

Last month, two new moons were discovered orbiting Uranus. They differ from those already known, being much further from the planet, and having elongated orbits — these are ‘irregular’ moons, such as are seen around all the other giant planets, Jupiter, Saturn and Neptune. So the discovery makes Uranus more like the other planets, to the relief of some astrophysicists.

A gravity anomaly, centred over Hudson Bay in Canada, has defied definitive explanation. Among the reasons for the anomaly could be that this area has not yet recovered (in a process known as post-glacial rebound) from being covered by a massive ice sheet during the last glacial maximum; or that it is one manifestation of unusual mantle convective flow in the Earth below. An innovative analysis of the global gravity field, which explores variation in the field's spectral content, provides the best answer yet — that 50% of the anomaly is due to incomplete post-glacial rebound. Moreover, the new approach will be widely applicable to other questions about Earth's structure.

Magnetic storms bring auroras to low latitudes and perturb the magnetic field all over the Earth, disturbing navigational systems and sometimes even electrical power grids. They are caused by sudden changes in the currents flowing close to the Earth, particularly the ‘ring current’ that flows intermittently within the Earth's magnetosphere. It was thought that the ring current was fed by smaller magnetic disturbances called substorms. But it seems that substorms are instead earthquake-like releases of magnetic stresses, allowing the ring current to be built up by the larger-scale interplanetary magnetic field.

The Chicxulub crater is the remnant of a meteorite impact that is blamed for killing off the dinosaurs. A new seismological survey shows that it is smaller than many scientists had thought, and extends deeper than anyone had suspected.

How can we make predictions about variability in the sizes of populations or the species composition of communities? Two new papers begin to solve these problems by dissecting them into smaller pieces — specifically, by looking at microbial microcosms. And they find that, in these systems, the predictability of communities may depend on species richness. In other words, the more ‘redundant’ species there are in the community, the more consistent is the function of the ecosystem.

Whenever biomass is degraded, and oxygen runs out, the methanogenic bacteria appear and make profuse amounts of methane. The structure of the enzyme that produces it, methyl-coenzyme M reductase, has now been worked out. The structure of the nickel centre and its interaction with substrates reveal the mechanism of one of the few organometallic reactions in biochemistry. Because the methanogens belong to the Archaea, one of the ancient divisions of organisms, the new work also gives a glimpse into what may have been one of the earliest forms of metabolism.

The puritan conscience holds that pleasure is sinful and should be followed by, and maybe even preceded by, pain. Daedalus is now inventing a drug appropriate for this stern view — it is an alcohol which gives you a hangover first. The chemistry is decidedly tricky, but the delayed rewards offered by the resulting ‘Pain and Pleasure Pill’ would have decidedly interesting applications.