News & Views in 1998

Fossils of very old — Devonian — ancestors of the centipedes and millipedes have been found only in the Northern Hemisphere. That situation changes with the discovery and description of two specimens from Australia; the oldest one dates to almost 400 million years ago. The new fossils raise issues about the biogeography of this group of arthropods, and also plausibly become the oldest-known remains of Australian land animals.

Last week, Daedalus planned to grow carbon nanotubes on a catalytic anode with circular reaction sites. Now, he wants to generalize the idea by making the reaction template more complicated. A hexagonal lattice of reaction sites, for example, would grow carbon honeycomb. Strong and light for structural purposes, carbon honeycomb could also be used as an insulator, a one-dimensional conductor, a molecular sieve or an absorbent.

Cell movement is mediated by dynamic networks of actin — monomers of actin polymerize into filaments near the plasma membrane. How are these actin structures organized? Two groups have found that a seven-protein complex, containing the actin-related proteins Arp2 and Arp3, is responsible for initiating and organizing an actin-based dynamic meshwork that forms protrusions at the leading edge of motile cells.

The first brain waves to be observed were measured at a frequency of ten cycles per second — that is, 10 Hz. Since then, waves have been detected at frequencies of 5, 40 and 200 Hz. But what do they do? One group has found that the 40-Hz waves are involved in a feedback-inhibition mechanism for coding 'events' (such as memories) in the brain. Another group has studied the 200-Hz waves, and they conclude that synchronization of neuron firing, which causes these waves, is due to gap junctions between nearby axons.

Galaxy clusters must trap large quantities of dark matter, and we expect it to be sharply concentrated near their centres. But using a new method for interpreting the effects of gravitational lensing, a much smoother and less centrally concentrated distribution of dark matter is inferred in one cluster. This could produce insights into the mechanisms governing galaxy-cluster formation, or even be a clue to the nature of dark matter.

Mathematician and master of singular integrals

High-temperature superconductors need to be doped with elements that donate charge-carrier. By changing the dopant cation, the superconducting transition temperature can be changed markedly. Why? It is due to lattice strains, caused by disorder in the cation size. This solves a ten-year old puzzle — but leaves open the question of the microscopic mechanism of high-temperature superconductivity.

Dendritic spines are small, actin-rich structures that protrude from the sides of dendrites, and receive excitatory inputs to the brain. Using a clever piece of video imaging, one group has found that each spine seems like a tiny, writhing sack of actin filaments, struggling to escape. This movement depends on polymerization of the actin, and it may be involved in synaptic plasticity, contributing to the formation of so-called ‘perforated synapses’.

Switches in the glacial-interglacial cycle are linked to climatic change, which is one reason for wanting to know more about them. The history of such switches can in part be traced by estimating sea level, which reflects the amount of water locked up in ice sheets. A study that uses the Red Sea as a gauge now takes estimates of lows in sea level back 500,000 years, well beyond the last glacial period.

If electronic devices are to be shrunk from the current micrometre length scale all the way down to the single-atom or molecule scale, we need to know how such tiny constructions will behave. Electrical measurements have now been made on the smallest electronic components possible — single metal atoms. They show that the conductivity depends on the number of valence electrons available in each atom.

Many theoretical models have been developed to study the conditions under which unrelated individuals should cooperate or not cooperate. But such behaviour is rarely ‘all or nothing’, and new mathematical models allow the optimal level of cooperation to be determined.

Despite its bad press, smoking is socially almost harmless - users do not become abusive or turn to crime because of it. In fact, the only antisocial aspect is the smoky smell that lingers, owing mainly to the fact that free nicotine reacts with oxygen. Daedalus now plans to rid smokers of such smells by delivering their nicotine fix to them together with another widely used drug — alcohol.

When you listen to music through headphones, the sound seems to come from inside your head. But there is an illusion known as ‘virtual auditory space’ which makes such sounds seem to originate outside the head. This virtual sound is now closer to reality thanks to a study showing that the parameters that need to be measured to create this effect are not as complicated as first thought.

Experiments with fruitflies have shown that those with fewer offspring generally live longer. Twelve-hundred years of genealogical data from British aristocrats now suggests that this relationship extends to humans.

The deep ocean is stirred; if it wasn't, the dense, cold and salty waters that sink at high latitudes would fill up the ocean basins from underneath. The energies required for such stirring, and the mechanisms involved, have been subject to a provocative analysis in which the prime movers implicated are tidal dissipation, largely driven by the Moon, and wind driving.

At present, attempts to harness the energy released by nuclear fusion centre on the so-called first-generation fuel, a deuterium-tritium plasma. This combination has the considerable drawback of intense neutron emission, which damages the plasma-confining structures. Hence the interest in investigating second- and third-generation fuels which emit few or no neutrons. But many hurdles remain to be surmounted if such fuels are to prove viable.