News & Views in 1999

Conventional semiconductor devices rely on the transport and storage of electronic charge. But electrons have spin as well as charge, and spin electronics is an emerging field that has already delivered commercial devices based on metallic materials. The goal of making similar devices from semiconductors is getting nearer thanks to two studies that show how to inject spin into a semiconductor.

Microtubule-based motor proteins, such as dynein and kinesin, can transport organelles around the cell. But many of these motors were originally identified for reasons other than this. A direct assay for organelle transport has now been devised, however, and initial tests using it have identified two hitherto unknown kinesins in the slime mouldDicytostelium discoideum.

The task of ranking scientists according to their citations by other scientists could be made easier when all research is published on the Internet. In the future it should be possible to analyse the citation index in greater detail, revealing cases of self or mutual citation.

Alzheimer's disease is characterized by the accumulation of aggregated tau protein. These aggregates are thought to form because hyperphosphorylation of tau causes it to dissociate from the microtubules to which it normally binds, and the tau molecules can then bind to one another. The cyclin-dependent kinase-5 (Cdk5) is suspected to be the kinase that hyperphosphorylates tau, and a new study reveals how Cdk5 might do this.

A process known as fragmentation is how erupting magma from a volcano breaks up into fine particles and ash, and it determines the type of eruption — gentle or violent — that occurs. Theoretical and laboratory studies show that treating magma as a brittle material can explain its behaviour at the point of fragmentation, when it is transformed from a foam into a gassy spray.

Animal populations might cycle because they are linked to the population of a predator or prey species, or because their reproduction has become synchronized, so that crowded generations have few offspring, which have many offspring, and so on. Work with the water fleaDaphniaand its algal prey shows what ecological factors drive and damp the population cycles in these species.

Glutamate is best known for its function in nervous transmission, where it is secreted from nerve terminals and acts as an extracellular excitatory neurotransmitter. There is now evidence that glutamate also has an intracellular function. It has been found to be involved in preparing secretory granules for release from the insulin-secreting β-cells of the pancreas.

Could a particle accelerator destroy the world? Fears that the Relativistic Heavy Ion Collider at Brookhaven in the United States could trigger an unforeseen disaster have been allayed by two studies that show the risk of worldwide catastrophe to be truly negligible.

Matter waves can now be amplified in the same way that a laser amplifies light. Such matter-wave amplifiers will be essential for future developments in atom optics, and may be the basis of better and brighter atom lasers.

The Gulf Stream transports heat from low latitudes through the Gulf of Mexico and on to the northern Atlantic Ocean. Work involving oxygen-isotope analysis of foraminifera shows that, at the time of the Last Glacial Maximum around 21,000 years ago, the Gulf Stream's flow was about 35% weaker than it is today. A cold climate, then, seems to have coincided with reduced northerly transfer of heat.

The areas of the brain responsible for early processing of sensory information have a systematic anatomical organization, allowing the topographies of the various sensory features to be mapped. Higher cortical processing centres were not thought to be organized in this way. But recordings made in monkeys using a unique electrode array reveal a functional organization for one of the highest cortical-processing areas in the brain — the hippocampus.

Our understanding of planet formation is surprisingly incomplete, so new ideas are always welcome. Computer simulations suggest that the giant planets formed together in a narrow region of our Solar System, and ended up in their present orbits after chaotic interactions. Another computer simulation proposes that the birth of one giant planet in the disk around a young star could trigger the formation of others.

When things go wrong on an aircraft there is sometimes little the pilot can do to keep it in the air. Ideally, then, aircraft should be fitted with parachutes for a safe descent in the event of an emergency. In practice, a big enough parachute would occupy almost the whole interior of the plane, so Daedalus has a plan to deploy a small parachute, but one that descends a little faster than the aircraft just before it hits the ground.

The study of chemical reactions is closely connected with the study of energy-relaxation processes. The discovery that an important energy-relaxation process in water is much faster than we thought means that vibrational energy gets dispersed too quickly in water to affect most chemical reactions.

Tom Jukes: Nutritionist turned molecular biologist, who was a redoubtable opponent of creationism and claims for quack cures for cancer.

The sequence of human chromosome 22, now published, is the first phase in a biological revolution. This chromosome is the second smallest, and consists of some 33 million base pairs and as many as 1,000 genes. The projected date for sequencing all 23 chromosomes is 2002, and the eventual upshot of this revolution will be a transformed appreciation of human individuality.

Alzheimer's disease is a progressive dementia in which massive protein deposits accumulate as either amyloid plaques or neurofibrillary tangles. The plaques are composed of a peptide called Aβ, which is liberated from its precursor, the amyloid precursor protein, by cleavage at two sites. The enzyme that cleaves at one of these sites, the β site, has now been identified, and it is likely to be a good target for drugs.