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Many transplant patients are given the drug cyclosporine to suppress their immune systems and prevent rejection. But cyclosporine also increases the risk of cancer, always thought to be a side effect of the depressed immune system. A new study shows that cyclosporine directly affects tumour growth and may be the culprit.
What flavour are the short-lived virtual quarks inside the nucleon? Two experiments have reported an excess of down- over up-antiquarks in the proton, contradicting expectations that the two flavours should be present in equal numbers.
An experimental study shows that the silica shells of diatoms, a hugely important component of the oceans' phytoplankton, can be enzymatically attacked and dissolved by bacteria. The finding extends knowledge of marine cycling of nutrients, that of silicic acid in particular, and helps explain certain patterns of shell deposition in sediments.
Quasars - the most luminous type of active galactic nuclei in the Universe - may not be active all the time. There is a growing consensus that quasars may have unstable galactic disks and therefore radiate only 10% of the time. If all observed quasars represent the outburst state, then this would explain how they can be so luminous without running out of fuel.
Most cells need to be attached, through integrins, to a semi-solid meshwork called the extracellular matrix in order to survive. But if peptides with the sequence arginine-glycine-aspartic acid are added, the cells detach and die. The reason was always thought to be a blockade of integrin signalling, but a new mechanism has emerged. It seems that the RGD peptide activates caspases directly inside the cell.
Primates — humans, monkeys and apes — have a very different retinal structure to that of other mammals. We use a trichromatic system, made up of three types of cone cell with peak sensitivities in different regions of the visual spectrum. Now, using an imaginative new technique, we can take our first look at the arrangement of these cones in the living human retina.
Explosives that detonate at the speed of light, rather than at the speed of sound (or slower) could be made with the help of photochemical dyes. However, photosensitive explosives will require careful handling and storage if they are going to transform the business of blasting rocks.
Further evidence that HIV-1 originally came from chimpanzees bears on a variety of issues — the evolution of AIDS viruses, disease transmission from animals to humans, and chimpanzee conservation and welfare.
It is increasingly evident that ocean variability in the Arctic can have global consequences. During the 1990s, thanks in part to data gathered by US submarines, unprecedented and system-wide changes in the region have been observed, and they were subject to discussion at a meeting late last year.
When mathematicians play with marbles they make advances in number theory and arithmetic progressions. A new proof calculates the maximum number of marbles that can be placed in a line without any four of them being evenly spaced, and raises hopes that a long-standing problem in number theory might finally be solved.
The ‘electron gas’ is an important model of the electrons in a solid. Its properties depend on the electron density, and it has long been suspected that at low densities the electrons would be susceptible to magnetic ordering. The difficulty of producing a dilute electron gas in the lab has now been overcome, and magnetic polarization has been observed at unexpectedly high temperatures.
Apoptotic cell death is driven by two classes of caspase — one to initiate the response and the other to carry it out. But initiator caspases can also activate death-promoting factors from the mitochondria. One of these is cytochrome c and another, the apoptosis-inducing factor, has now been identified. Both reside in the space between the inner and outer mitochondrial membranes, flagging this compartment as an important store of death factors.
How are messages from different regions of the brain bound together so that we can, say, associate a particular smell with a particular place? The accepted theory is that different stimuli are represented by the synchronous firing of different groups of nerve cells. Two studies provide evidence for this theory by showing that such synchronization occurs in humans at a frequency of around 40 Hz.
Explosive eruptions of volcanoes, such as that which destroyed Pompeii, are especially threatening to neighbouring human populations. Understanding of this type of eruption is still at an early stage, although it is clear that fragmentation of magma in the conduit inside the volcano is a key process. New models of magma fragmentation provide improved — but still imperfect — simulations of the behaviour of real volcanoes.
Thin, soapy films can be created because, if a region suddenly thins, surface tension rises and hauls it back to a safe thickness. Daedalus wants to apply this principle to glass, to allow the creation of an ultra-thin glass film that could be used for glazing, to produce unscratchable, unbreakable windows, or even for making books with glass pages.
Ever since the creation of the first Bose-Einstein condensate in 1995, physicists have been dreaming up ways to explore their macroscopic quantum properties — now they want to make them spin. New calculations of a rotating Bose gas predict what these spinning condensates would look like.
