Archive for March, 2009

Blood clotting light work for new molecule

Published in Chemistry World, 31 Mar 2009

Scientists in the US have created a light-activated molecule that can control blood clotting. The molecule, which works with the help an enzyme, could one day be used in medicine to shut off blood supply to localised areas of the human body such as tumours.

The past decade has seen a strong interest in studying the way light can trigger certain molecules to change from a stable state to an unstable one. This transformation is known as photochromism, and it is exploited, for example, in certain eyeglasses that darken on exposure to UV sunlight. One type of photochromism generating interest in medical science is photoisomerism, in which light causes molecules to switch their entire structural symmetry, from ‘cis’ (when chemical groups occupy the same side of the molecule) to ‘trans’ (when they take opposite sides). [...]

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Quakes eat up the heat

Published in Chemistry World, 26 Mar 2009

More than half of the heat generated by friction in earthquakes could go to towards endothermic reactions, a study by geoscientists in Japan and Taiwan has shown. The conclusion suggests that chemical reactions ought to be more seriously considered when modelling the dangerous events.

Earthquakes are among the most deadly natural hazards, yet are also some of the most poorly understood. They tend to occur at the ‘fault zones’ between two tectonic plates in the Earth’s crust, and start as small cracks which quickly grow in a chaotic fashion. During these events a huge amount of energy bursts free - perhaps hundreds of megaJoules per square metre - in the form of seismic waves, fractures and heat. To gain a better understanding of the underlying mechanics, geoscientists need to know how the energy is distributed between these forms. [...]

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Cold fusion: The ghost of free energy

Published on GroundReport, 23 Mar 2009

Two decades ago a pair of eminent chemists claimed to find the secret of almost limitless energy, only to have their results dismissed several weeks later. Today many scientists think there was truth in the claims but, as Jon Cartwright discovers, few are still listening

The late writer Arthur C Clarke had a knack for anticipating great developments in science. In the mid 1940s, more than a decade before the formation of NASA, he said that man would walk on the moon before the century was up. Around the same time he wrote a paper in which he suggested that satellites in special geostationary orbits would be ideal for worldwide radio communications, an idea that was realized some 25 years later. And in 1993, he wrote a letter to the new vice-president of the US, Al Gore, with another of his nagging hunches. “Dear Mr. Gore,” it read. “I am happy to learn that you are being briefed on the above — perhaps misnamed — subject, as it is impossible to imagine anything of greater potential importance from both the economic and geopolitical points of view.” The subject reference at the top of the letter was “cold fusion”. (more…)

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Medical probes get easy to spot

Published in Chemistry World, 20 Mar 2009

Scientists in the US have created nano-scale medical probes that are visible via both magnetic resonance imaging (MRI) and optical microscopy. They say that the probes, which contain gold nanorods and magnetic particles, can be easily tracked as they target cancerous tissue.

The last few years has seen a lot of research focused on medical probes that can simultaneously target, track and treat diseased parts of the human body. One tracking option is to base the probes on magnetic particles, which show up clearly in MRI scans. The magnetic fields of MRI penetrate deep into tissue, but the technique is not terribly precise. An option that provides more accuracy is to base the probes on luminescent particles such as gold, as the light emitted from these particles is visible to optical microscopy. However, optical microscopy also has a drawback in that it can only see things close to the surface of the body. [...]

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Metals lose identity under pressure

Published in Chemistry World, 11 Mar 2009

Two independent teams have demonstrated that metals can lose their high conductivity under pressure, proving that the standard models used to describe their behaviour are inadequate.

Yanming Ma of Jilin University in Changchun, China, and colleagues from Switzerland, Germany, Russia and the US have shown that sufficient pressure causes sodium to become optically transparent. Meanwhile, Takahiro Matsuoka and Katsuya Shimizu of Osaka University, Japan, have shown that it causes lithium to turn into a semiconductor. [...]

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Molecular junctions make a switch

Published in Physics World, 11 Mar 2009

Physicists in the US have shown how the electrical current flowing through certain molecular junctions can be switched on and off on by simply stretching or compressing the molecules. The discovery could be exploited to make switches in future molecular devices, and could also help in the understanding of resistance at the nanoscale.

In normal electronic devices, resistance is a well-understood property. When an electric field is applied across a metal, charge–carrying electrons begin to drift but bump into ions and impurities, which slow their motion. At nanometre distances, however, things are not so simple: electrons are able to “tunnel” across small insulating barriers with a finite probability. This means that the electrons can overcome obstacles without losing energy, and therefore without electrical resistance. [...]

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Nanotubes wreak havoc with heat

Published in Physics World, 2 Mar 2009

Physicists in the US have discovered that electrons flowing in carbon nanotube-based circuits dissipate energy in very different ways from electrons flowing through devices made from conventional semiconductors such as silicon. The findings reveal processes of heat conduction that were never previously thought important and could influence the types of materials chosen for the next generation of electronic devices in order to prevent them from overheating.

In conventional semiconductor devices, different layers of material are always joined by chemical bonds. This provides continuity for heat flowing through such devices, making them relatively easy to cool. Many researchers believe that future generations of electronic devices could be made from carbon nanotubes — tubes with walls just one atom thick — which could enable much smaller feature sizes and hence much better computing performance. However, nanotubes do not bond chemically to adjoining structures, which suggested that it should be very difficult to remove heat from such devices. [...]

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