Archive for February, 2010

Reactions on DNA origami watched with AFM

Published in Chemistry World, 28 Feb 2010

Chemists in Denmark have for the first time imaged chemical reactions on a DNA origami scaffold so that they can precisely attach single molecules. Their method, which involves atomic force microscopy, will help researchers to create self-assembling DNA nanodevices for applications ranging from biosensing to drug delivery.

Although DNA itself has limited potential in chemistry, optics and electronics, its structure can serve as a template for building materials with new functional properties. For complex structures, long DNA molecules can also be folded into different shapes, known as DNA origami. The idea is that different molecules can then be attached to the origami ‘pegboard’ so composite structures become tailored, say, for conducting or optical circuits. [...]

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Biofuels without the blend

Published in Chemistry World, 25 Feb 2010

Scientists in the US have come up with a method to recycle agricultural waste into renewable alkenes for jet and diesel fuel. The breakthrough opens the door to biofuels that do not rely on special farms and that can directly replace their petroleum counterparts.

Biofuels have long been considered a promising means to reduce our dependence on oil, but traditional candidates have faced several problems. Ethanol, for instance, can be oxygenated for use in combustion engines, but only as a blend where the other 90 per cent is petrol. It is also of little use to aeroplanes, since it has such a low energy density. Finally, there is the issue of where the ethanol comes from: typically vast corn fields, which often require huge areas of deforestation. [...]

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Ultracold magnetic atoms bode well for quantum studies

Published in Physics World, 18 Feb 2010

Physicists in the US have for the first time trapped ultracold atoms of dysprosium, the most magnetic element in the periodic table. The breakthrough could open the door to a greater understanding of superfluidity, highly sensitive probes of magnetic fields, and new ways to read and encode quantum information.

Researchers would like to trap as many of the periodic table’s elements as possible, because the unique properties of each allow for different simulations of condensed-matter systems. The typical method involves a magneto-optical trap (MOT), in which a laser causes atoms to temporarily absorb photons and jump into an excited state. These photons give the atoms a push that, combined with the right magnetic field, is directed towards the centre of the group and keeps the atoms cooled and trapped. [...]

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Warm white dwarfs could reveal ‘inelastic’ dark matter

Published in Physics World, 11 Feb 2010

Direct observations of dark matter – the substance thought to account for 80% of matter in the universe – are sketchy, at best. Some experiments have found what seem like dark-matter signals, while others looking within the same parameter range have found nothing. Yet there is a hypothetical candidate for dark matter, known as “inelastic” dark matter, that could reconcile such results – and now two teams of physicists have proposed new ways to see if it exists.

The story of inelastic dark matter begins over a kilometre beneath Gran Sasso mountain in Italy, which is home to the underground DAMA experiment. Here, a bank of detectors watches out for the flash of light that is expected when a dark-matter particle strikes a nucleus within the experiment. Although such collisions are very rare, in theory there should be more flashes in summer, when the Earth is orbiting against the prevailing “wind” of dark matter in our galaxy. [...]

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London, the ‘polycentric’ city

Published in Physics World, 3 Feb 2010

How do commuters move around in big cities? Most people would assume that they all do pretty much the same thing: travel from the outskirts to the centre, and then back again. Yet according to a group of physicists in the UK and France, this is not the case.

“The popular conception of a city – that people work in the centre and live around the edge – is, to a certain extent, a gross simplification of what actually happens,” says Michael Batty, director of the Centre for Advanced Spatial Analysis at University College London (UCL). “The notion that one could simplify the sort of complexity that is evident is probably a non-starter.” [...]

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