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e/5 particles discovered

In 1980 Klaus von Klitzing discovered that the so-called Hall conductance across a material varied in steps, not continuously, as the magnetic field was changed. In other words the Hall effect was quantized. The size of the steps was related to the charge of the electron. In 1982 Störmer and Tsui discovered the fractional quantum Hall effect, which suggested the existence of charge carriers with a charge of e/3.

To explain these findings, Laughlin proposed that the electrons combine with the magnetic “flux quanta” to form quasiparticles, and that the flux lines effectively “shield” the charge on the electron. A quasiparticle made from two flux quanta and one electron, for instance, would have a charge of e/3. Subsequent experiments have suggested, indirectly, other quasiparticles with charges of e/5, e/7 and so on.

In the mid-1990s Heiblum’s team and teams in France and the US found direct evidence for quasiparticles with a charge of e/3. The Weizmann team has now developed a more sensitive version of their earlier experiment. They embedded a tiny point contact within the two-dimensional electron gas to separate the quasiparticles according to their charge and found evidence for the elusive e/5 particles (M Reznikov et al . 1999 Nature 399 238).

Nanotubes muscle in on ‘smart materials’

The new technique works because the salt water conducts electricity. As the voltage on the tape changes, electrical charge carriers are injected into the nanotubes. These form electrolyte ions near the surface of the tape. On the cathode side of the tape, electrons are attracted to the nanotubes and cause them to expand. On the anode side, electron “holes” cause the nanotubes to contract.

According to Baughman and his colleagues the nanotube ‘muscle’ could generate and survive higher stresses than any other materials, including real muscle tissue and ferroelectric materials. Moreover, the voltages needed to bend the nanotubes are much lower than those needed to change the shape of ferroelectric materials. This suggests the nanotube sheets could have a wide range of practical applications including optical fibre switches and microscopic pumps.

Pugwash calls for new roles for Aldermaston

Aldermaston has over 4000 employees and a budget of £300m. Over half of this (£168m) is spent on the manufacture, maintenance and testing of nuclear weapons, and on related research. Another £91m is spent on the Trident nuclear weapons programme and £11m goes on dismantling nuclear weapons.

According to the report, a shift in emphasis towards disarmament and verification programmes at Aldermaston would help the UK to carry out its obligations under the nuclear non-proliferation treaty (NPT). The treaty states that nuclear weapon countries should pursue a policy of eliminating nuclear weapons. By involving Aldermaston with similar programmes in Russia and the US, the report argues, AWE could help build new trust mechanisms between the nuclear states. These new roles would also help Russia safeguard its nuclear materials and prevent them from falling into the hands of ‘rogue states’ or terrorist groups. Another benefit, according to the Pugwash report, would be to attract more high-calibre scientists to Aldermaston.

Last year the UK government set up a pilot study to investigate the possibility of establishing an arms control and disarmament group at Aldermaston as part of the strategic defence review. The report is due out next spring.

Pugwash received the 1995 Nobel Peace Prize for its work towards nuclear disarmament along with Joseph Rotblat, its ex-president.

Understanding avalanches

Snow avalanches occur when the mass of the snow overcomes the frictional resistance of the slope. This usually takes place when snow layers near the slope are loosened by spring rains or vibrations. Daerr and Douady coated an inclined felt surface with layers of the beads, making sure that the beads remained static on the felt. (The friction between the beads and the felt is larger than the friction between the beads, making this an ideal system for modelling avalanches.) Adding more beads, or jolting a layer of them, caused the beads to roll down the slope and freeze back into a layer of glass beads. Again this was similar to the observed behaviour of snow.

Daerr and Douady repeated the experiment at a number of different inclinations and with different materials – such as crushed walnut shells and Sinai sand – and confirmed their initial hypothesis about the two different types of avalanche.

Galactic nuclei outdistances quasars

Wil van Breugel from the Lawrence Livermore Laboratory and colleagues from the University of California, Berkeley and Leiden Observatory in the Netherlands found their galactic nucleus by looking for radio sources that generate strong radio waves over a narrow band from a single power source. They looked for optical candidates of these sources at near infrared wavelengths using the Keck II telescope. This allowed them to measure the redshift of the objects. The galaxy at TN J0924-2201 was measured at a redshift of 5.19 – further than any known quasar source. This overturns the idea that quasars are the most distant radio sources in the universe.

Earlier this year the Hubble Space Telescope pinpointed the most distant galaxy at ultraviolet wavelengths at a redshift of 6.68 – 5% the present age of the universe.

Boost for UK physics

The JIF scheme is funded by the government and the Wellcome Trust, the world’s largest biomedical research charity. It was established after several reports found that a shortage of state-of-the-art research equipment was making it difficult for universities in the UK to remain at the forefront of international research. Nearly £150m has been awarded to 37 projects in 22 different institutions in the first round of the scheme.

The VISTA telescope will spend three-quarters of its time conducting a detailed all-sky survey, and will be the first UK project in this field since the 1.2-metre Anglo-Australian Schmidt telescope. Unlike Schmidt, VISTA will use CCD cameras instead of photographic plates to obtain its images. “VISTA will be an outstandingly powerful tool for British astronomy, ” says Emerson. “The whole astronomical community is delighted with this decision.”

ESA tightens its belt

The ESA Council meeting, held in Brussels over the past two days, also formalised closer ties to the European Union. ESA hopes that the EU will become a major new source of funds for some of the industrial programmes such as Galileo, a joint ESA/EU global navigation system. A final decision on the future of Galileo will happen at an EU transport meeting in June. During the ESA meeting, Lord Sainsbury, the UK Minister for Science and Space, was appointed chairman of the European Space Agency (ESA) Ministerial Council.

The Earth science programme is an attempt to put “Earth sciences on a more equal footing with ESA’s traditional strengths in scientific research” says Sainsbury. The programme includes new satellites to monitor the effects of global warming from space. The ministers also confirmed Europe’s involvement in the International Space Station by putting Euro 298.5m ( £ 196m) towards its operating costs over the next two years.

One unexpected surprise was the approval of Mars Express – a Euro 150m spacecraft to be launched in 2003. Space scientists have lobbied against the proposal as funds originally scheduled for the FIRST/PLANCK mission have been diverted to fund Mars Express. However, no funds were made available for Beagle 2 – a small lander craft attached to Mars Express. But Colin Pillinger of the Open University and principle proponent of the project remains optimistic that the Euro 38m (£ 25m) needed for the lander will become available from another source.

Dispute threatens JET extension

Under the terms of the new European Fusion Development Agreement (EFDA), JET would no longer carry out one common programme of work approved by the EU. Instead, the JET facilities would be run by the UKAEA on behalf of Euratom. Visiting teams of researchers from JET’s 16 member states or “associations”, which include the UK, would then do experiments at JET agreed by a peer-review selection panel. A non-UK director would be appointed to lead the experimental work.

The EFDA, which was negotiated by the European Commission and the various associations, came into force at the end of March. It includes an “implementing agreement” to allow JET to continue until 2002, and an “operating contract” to let the UKAEA run the facility. But if all the individual associations and the European Commission do not sign the agreement, JET will have to close. The UKAEA would then have to decommission the facilities and return the Culham site to green fields, as planned when JET was launched in 1979.

Although the UKAEA is confident that the associations will sign, the main stumbling block is the dispute over staff salaries, which has been rumbling on for more than a decade and has now gone to court. “The court case is the last obstacle to agreeing the new arrangement, ” says Martin O’Brien, a fusion programme manager at the UKAEA. “But if there is no significant progress with the court case, some parties say they will not sign.”

Martin Keilhacker, director of JET, agrees: “The court case could be an impediment. If the court case is still dragging on, it’s not clear if all countries will sign.” The European parliament will now negotiate with the various parties to try to resolve the dispute. Keilhacker hopes that an out-of-court settlement can be reached.

One promising sign is that most of the 100 or so Euratom staff at JET will have left the project by the end of the year for other EU posts. Non-UK scientists at JET will in future be employed by their own countries and will only visit JET for short periods. They will not necessarily be earning more than their UK colleagues.

JET was designed as the first step on the path to a commercial fusion reactor. It was meant to be followed by the $10bn International Experimental Fusion Reactor (ITER). But when the US pulled out of ITER last summer after six years of design studies, ITER’s three remaining partners – the EU, Russia and Japan – agreed to concentrate on a smaller and cheaper version of the reactor. Researchers at JET hope to use the extension to look at the science and engineering behind a smaller reactor, where several challenges exist.

Derek Stork, head of neutral-beam heating at JET, welcomes the prospect of a three-year extension. “The JET reactor has a substantial potential for improved performance, and we have a broad and exciting range of experiments that can only be performed on this machine, ” he says. However, Stork admits that JET’s programme could become less coherent without a dedicated project team. “Operating a novel management structure will be a challenge, and there will inevitably be ups and downs.”

Keilhacker sees next year as a transition period, when the individual associations will have to learn to use the JET facilities according to new rules, both technically and organizationally. “In fact, the new arrangement could make Europe’s fusion programme more closely integrated because the individual countries will have to discuss the division of work, ” says Keilhacker.

If an agreement is reached, Keilhacker is confident that JET could even continue beyond 2002. “My personal opinion is that it will carry on for about another two years, assuming, of course, that money is still available.” Keilhacker thinks that an extension would be more likely if a decision on the future of ITER takes longer than expected.

Knots make polymers weaker

Polymers are long chain-like molecules made up of smaller molecules called monomers. It is well known that polymer chains often tie themselves in knots, but it was not clear how this influenced the mechanical properties of the polymer. Klein and colleagues modelled what happens when a knotted polymer chain consisting of 144 carbon atoms was stretched. They found that as the ends of the chain were pulled apart, the knot gradually got tighter and tighter – reducing the number of carbon atoms in the knot – until the polymer chain ruptured next to the knot. According to their calculations, a polyethylene polymer breaks once the number of carbon atoms in the knot is reduced to 23.

Magnetic mystery on Mars

Geophysicists realised that the Earth’s crust consisted of a series of tectonic plates when they noticed that as magma flowed out of the ocean ridges and cooled, iron in the magma magnetized in the direction of the Earth’s magnetic field. This field changes direction roughly every 10000 years. The material from the ocean ridge gradually expands outwards along the ocean floor, creating a pattern of magnetic stripes on either side of the ridge.

The patterns seen on Mars are more strongly magnetised than those seen on Earth. “We had no idea we’d see anything of this magnitude. It was mind blowing, ” said Jack Connerney of the NASA Goddard Space Flight Center in Maryland. One possible reason is the high iron concentration (15%) in the Martian crust. The magnetic strips are also longer and wider than those seen on Earth – which suggests that Martian magma flowed more quickly than the Earth’s and the global magnetic field flipped less.

However, other physicists are perplexed by the results. In an article in the same issue of Science Sean Solomon of the Carnegie Institution in Washington writes that the magnetic footprints measured by Global Surveyor are too strong to be explained by plate tectonics and could therefore have been created by some other process such as chemical activity.

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