News & Views in 1999

The rapidity and amount of carbon being released through human agency have been thought to be unprecedented. Not so, it emerges. From the evidence of anomalies in the ratios of carbon isotopes in an ocean core, it seems that, around 55 million years ago, there was an equivalently swift and massive blast of carbon into the ocean and atmosphere. The source was probably methane hydrates that are usually locked up in huge deposits on continental shelves.

Mammals and flies both stave off pathogens using the innate immune response. In the fruit fly this involves cell-surface receptors belonging to the Toll family, which mediate separate anti-bacterial and anti-fungal responses in the same type of cell. Studies of two mammalian Toll-like receptors, TLR2 and TLR4, indicate that this system is also used in the innate immune responses of higher animals.

The main problem with using concrete as a building material is that it cannot creep under load and so it cracks. Daedalus plans to create a crack-free concrete. Known as 'Wet Cement', his concrete will be a calciferous mortar that takes up water from the air, so it never dries out. It will be much less stress-sensitive than conventional concrete, and it will be welcomed by architects and householders alike.

The wave-particle duality postulate is well verified and holds that 'atomic' particles have wave as well as particle properties. But, in terms of increasing mass, how far does this principle of quantum theory apply? Experiments with the fullerene C₆₀extend evidence for wave-particle behaviour by an order of magnitude towards -- but still far short of -- the macroscopic domain.

For astronomers, devising better photon detectors is far cheaper than building bigger telescopes. Such detectors can be key elements of progress, and the pulsar at the centre of the Crab nebula is a challenging target for them. New types of superconducting detector have the speed and sensitivity to meet that challenge, and the technology concerned is not yet at its limits.

One elusive goal in semiconductor technology is realizing the ideal nonvolatile memory -- that is, one that retains information when the power is switched off without battery back-up. In this context, so-called ferroelectric random access memories are promising. Work on a particular form of ferroelectric material provides encouraging evidence that it has the desired properties for nonvolatile memory.

When we encounter a particular pathogen for the first time, the immunological response is often slow. Yet if we re-encounter that pathogen the response is rapid and vigorous owing to a phenomenon known as immunological memory. The best assay yet to distinguish between the various T cells involved in the memory response has now been developed, and it may help us to understand more about how this response is generated.

A hurricane's path is quite easy to forecast, but its intensity is not. A new model, which takes into account the interaction of the storm and ocean-surface temperature, gives remarkably accurate retrospective simulations.

The way we see the world around us depends on an interplay between two types of signal in the brain -- 'bottom-up' signals, which are derived from the physical data that bombard our sensory receptors, and 'top-down' signals, which interpret these data. For the first time, using a new surgical technique, we can directly see top-down signals in the brain, providing evidence that these signals come from the prefrontal cortex.

How do biodiversity and ecosystem properties, such as nutrient cycling and response to disturbance, interact? New work shows that in some ecosystems, rather than being a function of the number of species present, this relationship might be dominated by the extrinsic environmental factors that determine biodiversity.

How does a cell decide to become a nerve cell and not, say, an endothelial cell? Such cell-fate decisions are made by certain 'master' genes, which switch on cellular programmes to differentiate precursor cells into various cell types. Differentiation is thought to be kept in check by molecular 'brakes', and a study of mice lacking Id1 and Id3 indicates that these proteins could act as just such brakes.

Plants using 'CAM' metabolism have an advantage in dry, sunny places. So you wouldn't expect to find them on the floor of the rainforest. But one CAM species can survive here by thriving in conditions for which its neighbours are not adapted.

Both graphite and diamond can be found in single-crystal form, so Daedalus proposes to flip one crystal form into the other by explosive forming. His idea is to lay an explosive next to a carefully shaped piece of single-crystal graphite, then to detonate it. The shock-wave running through the graphite should collapse its lattice into the denser structure of diamond.

In the field of plant-pathogen interactions there have been three recent bursts of knowledge. The first was the isolation of the disease-resistance (R) genes; the second was the ability to isolate mutants in 'model' plants; and the third was identification of a conserved delivery system in plant and animal pathogens. Progress in all three areas was discussed at two recent meetings.

Studies of Bose–Einstein condensates continue to provide dramatic displays of quantum-mechanical behaviour. The long-sought goal of creating a quantized vortex in these unusual fluids has now been achieved.

From the onset of the Industrial Revolution to the mid-1970s, the emission of acidifying compounds to the atmosphere has increased steadily. Measures to cut international emissions of problematic sulphur and nitrogen compounds have been in place since the mid-1980s, and there is new evidence that they are working -- the chemistry of some surface waters is showing signs that the acidification process is reversing.

Recent years have seen the emergence of new forms of photonic crystal structures for controlling electromagnetic waves in three dimensions. A further step is now being taken with the additional incorporation of liquid-crystal technology: the result could, for instance, be light-emitting diode displays with pixels whose colours can be altered.

Cell shape and movement are largely driven by changes in the cytoskeletal protein actin. Bacteria such as Listeria, which subvert a cell's actin system for their own movement within a cell, are used to study those changes. This bacterial propulsion system has now been stripped down to its minimum requirements -- which, it turns out, are actin and a mere three other proteins