Gold plating improves nanotube imaging

Chemistry WorldJon Cartwright

Published in Chemistry World, 23 Aug 2009

Techniques used to image tumours and infections improve when the carbon nanotube ‘contrast agents’ are gold plated, researchers in the US have discovered. The gold plating reduces the nanotubes’ potential toxicity while boosting their effect as contract agents, thereby allowing far fewer of them to be used for the same effect.

Doctors use both photoacoustic and photothermal imaging to examine diseased tissue. The techniques involve shining a laser onto the tissue and measuring either the emitted heat – that is, the infrared radiation – or ultrasound. By adding contrast agents, such as pigmented biomolecules, the tissue responds better to the laser and the images become clearer. […]

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Metamaterials learn to remember

Physics WorldJon Cartwright

Published in Physics World, 21 Aug 2009

Materials best known for their use as invisibility cloaks and super-lenses can now have their properties fixed with external stimuli, thanks to research performed in the US and the South Korea.

The new “memory metamaterials”, made by Tom Driscoll of the University of California at San Diego and colleagues, can have their electromagnetic properties temporarily modified depending on the level of applied voltage or light. According to the researchers, such tuning could allow for a “set-and-forget” approach to complex metamaterials for applications where it is impractical to maintain an external stimulus. […]

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Seeing quantum effects on a big scale

Physics WorldJon Cartwright

Published in Physics World, 19 Aug 2009

A scheme to couple the motion of a single atom with a crystal membrane could enable quantum-mechanical effects to be seen on a larger scale than ever before.

The idea, which has been proposed by researchers in Austria, Germany and the US, could help to solve the mystery of why quantum effects only seem to appear at tiny dimensions while the everyday world is governed by classical physics. […]

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Ozone reaction with skin causes irritants

Chemistry WorldJon Cartwright

Published in Chemistry World, 18 Aug 2009

Ozone found in indoor environments reacts with human skin, potentially producing chemicals that irritate the skin and lungs, according to researchers in Austria and the US. The study, which is the first of its kind to be performed with humans, highlights the limitations of current methods used to assess indoor air quality.

Trioxygen, or ozone, is present in low levels throughout the Earth’s atmosphere. Ozone can find its way indoors, although it is also emitted by many devices including photocopiers and air cleaners. For this reason, past studies have investigated the effect of ozone in the office environment. However, these have all focused on ozone’s chemistry with materials and consumer products, and not on its chemistry with humans. […]

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Nanomotors detect trace silver

Chemistry WorldJon Cartwright

Published in Chemistry World, 14 Aug 2009

Researchers in the US and Germany have found that the speed of synthetic ‘nanomotors’ responds to nearby concentrations of silver. The discovery suggests that nanomotors could be used to detect trace levels of silver and other toxic substances in water supplies – a practice that has previously required bulky instrumentation.

Nanomotors are nano-sized machines that can convert energy into motion. For a long time the only known nanomotors were biological and made from natural proteins, but in the last decade scientists have been able to create synthetic nanomotors with similar activity. […]

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Yushchenko poisoning study calls for dioxin tests

Chemistry WorldJon Cartwright

Published in Chemistry World, 11 Aug 2009

Research into the non-fatal poisoning of Ukrainian president Viktor Yushchenko in 2004 has revealed the unexpected breakdown of the dioxin used to poison him, and prompted researchers to call for the development of new methods to spot the compound’s metabolites.

In what is the first published study of President Yushchenko’s apparent poisoning in 2004, toxicologists from Switzerland and the Ukraine show that – contrary to popular belief – the dioxin TCDD (2,3,7,8-tetrachlorodibenzo-p-dioxin) is able to metabolise in the human body. The discovery suggests that development of methods to assess the dioxin’s metabolites would give scientists a better understanding of TCDD poisoning and possible therapies. […]

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Beetle has polarizing twist in its shell

Physics WorldJon Cartwright

Published in Physics World, 23 Jul 2009

A structure much like a liquid crystal allows the shell of a scarab beetle to circularly polarize light, scientists in the US have discovered.

Mohan Srinivasarao of the Georgia Institute of Technology and colleagues have used microscopy techniques to show that the iridescent green scarab beetle (Plusiotis gloriosa), has a shell that contains a helical structure, rather like a “cholesteric” liquid crystal. […]

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Could Fermi detect dark matter within a year?

Physics WorldJon Cartwright

Published in Physics World, 16 Jul 2009

The Fermi Gamma-ray Space Telescope could detect the telltale signs of dark-matter annihilation in as little as a year, if calculations by UK and US astrophysicists prove correct.

The calculations, which are the first to take into account the relative velocities of dark-matter particles, suggest that dark-matter annihilation is many times more prevalent than has been predicted before. If this is true, the annihilations could be producing enough gamma rays to expose several clumps or “subhaloes” of dark matter in Fermi’s first year of data collection alone. […]

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Nanoparticles show ‘inverse photoconductance’

Chemistry WorldJon Cartwright

Published in Chemistry World, 16 Jul 2009

Chemists in the US have created the first material to exhibit ‘inverse photoconductance’, in which conductance decreases with exposure to visible light. The effect could be exploited to make new types of sensor that can be tuned for different spectral properties and printed directly onto plastic substrates.

Traditional photoconductors increase their conductance when exposed to light, and are typically made of a high-resistance semiconductor. When photons strike the semiconductor’s surface, they impart energy to electrons in the valance or conduction band. These energetic electrons then jump into the conduction band and, combined with the positive hole left behind, boost the semiconductor’s conductivity. […]

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Fledgling site challenges arXiv server

Physics WorldJon Cartwright

Published in Physics World, 15 Jul 2009

A physicist in the UK has set up a new website for sharing preprints following criticisms about the way that the popular arXiv.org preprint server is moderated. Called viXra.org, which is the reverse of arXiv, the rival server — unlike arXiv — places no restrictions on the sorts of papers that can be posted. “This is an experiment to find out what kind of stuff is not managing to get into the arXiv, as well as being a serious archive for people to put their research in,” says Philip Gibbs, an independent physicist based in the UK and creator of viXra. […]

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