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Herschel. image: ESA

Herschel. image: ESA

Issue no. 6, 2009 Published: Feb 13, 2009
'Silver sensation' seeks cold cosmos
Photosynthesis viewed in a flash
Twisted radio beams could untangle the airwaves
New tool maps dengue's climate spread
Moth eyes inspire more efficient solar cell
Batteries get a boost with hybrid nanocables

'Silver sensation' seeks cold cosmos
The European Space Agency (ESA) has been working on its new space observatory for more than 20 years. At 3.5m in diameter Herschel will soon become the biggest telescope mirror in space, surpassing that of Hubble. Soon it will be launched in space and take up a vantage point a million-and-a-half kilometres from Earth, to open up what scientists expect to be an utterly fascinating new vista on the Universe. Unlike Hubble, which is tuned to see the cosmos in the same light that is visible to our eyes, Herschel will go after much longer wavelength radiation - in the far-infrared and sub-millimetre range. It will permit Herschel to see past the dust that scatters Hubble's visible wavelengths, and to gaze at really cold places and objects in the Universe. Some of these targets are frigid in the extreme (between -268 to -223C) and for Herschel to register them requires an even colder state be achieved on the observatory itself. This involves the use of a cryostat. It is akin to a giant 'thermos' bottle. Filled with more than 2,000 litres of liquid helium, its systems will plunge Herschel's science instruments into the deepest of chills. Critical detectors will be taken to just fractions of a degree above absolute zero (-273C), from where they can make the most of their remarkable design performance. Herschel's other instruments are HIFI (the Heterodyne Instrument for the Far Infrared) and PACS (Photodetector Array Camera and Spectrometer). With the entire package, the observatory can investigate a broad range of wavelengths (55-672 microns), including a swathe that has hitherto been missed by orbiting telescopes.
BBC News Feb 09, 2009	back to top

Photosynthesis viewed in a flash
A new method of examining the inner workings of plants has shed light on how they harvest the Sun's energy. Irish and British scientists have taken ultrafast laser snapshots to examine the role of electrons in energy transfer. The approach will be key in discovering how energy trickles through other systems and could lead to better solar cells. The researchers examined the protein LH2, a well-known photosynthetic system. The protein helps to pull electrons out of water which are then used to drive the reaction that makes sugars from CO2. Significant research has been performed to assess the role of electrons in that process. What has remained unclear is the way in which electrons interact with each other or with the molecules of the machinery. Current laser-based methods to examine that electron coupling require that the delicate proteins are subject to thousands or millions of laser pulses, which can change their structure or destroy them altogether. However, the new method can look at those electron couplings directly with just one 'ultrafast' laser pulse lasting only 100 femtoseconds. Such short pulses are made up of a broad spectrum of colours, with each colour corresponding to the particular energy of the photons that make it. The new method works by splitting powerful laser pulses into three beams and crossing them in the protein samples in a specific geometry. The light that comes out gives an unambiguous picture of how the different colours interact inside the protein.
BBC News / Physical Review Letters Feb 07, 2009	back to top

Twisted radio beams could untangle the airwaves
The radiofrequency spectrum available for wireless communication is becoming the increasingly crowded, with virgin 'veins' of frequency running short. However, an international team of physicists say that twisting radio beams into a helical shape as they are transmitted could help ease the congestion. Radio frequency encompasses electromagnetic waves between 3 kilohertz and 300 gigahertz, and as wireless communications technology advances much of that range is being used. Satellite TV, wireless computer networks and cellphones are among the growing technologies vying for space up to 30 gigahertz, with some technology even beginning to extend beyond 100 gigahertz leaving a dwindling supply of virgin terrain to exploit. The researchers have demonstrated that it is possible to put a spin on radio beams during their transmission to produce a twisted beam. That advance could prove important as it provides a new way to encode information into radio transmissions. The signal is twisted by firing antennas in sequence to describe a circle, instead of having all of them transmit the same signal at once. The twists remain coherent across vast distances - light years, even - and can store information in the form of digital bits (1s and 0s), encoded into the pitch of the twist.
New Scientist / Physical Review Letters Feb 13, 2009	back to top

New tool maps dengue's climate spread
Australian and US scientists have developed a method to predict the spread of the dengue-carrying Aedes aegypti mosquito as the climate changes. They identified the key factors that determine where A. aegypti mosquitoes can live. These factors include aspects of the mosquito's biology such as the ability of its eggs to tolerate drying out, environmental factors such as temperature, and factors that in part depend on human behaviour, such as the availability of standing water for the mosquito to lay its eggs in. By combining these factors with climate change projections, the researchers found that suitable habitats for A. aegypti will increase in the next 40 years in Australia — into areas that had previously been hostile to the mosquito. The model can be used anywhere with A. aegypti populations, particularly the tropical and subtropical countries where dengue is a problem, the researchers say. The model can also be used to predict the spread of any disease vector.
SciDev / Functional Ecology Feb 12, 2009	back to top

Moth eyes inspire more efficient solar cell
Researchers at the AMOLF institute in the Netherlands have developed an anti-reflective coating based on the nanostructure of a moth’s eyes, which could reduce the reflection from photovoltaic cells and thereby make them more efficient. The researchers say that their 'moth-eye' technology is superior to other known anti-reflection measures. Additionally, they have developed a new eco-friendly production technique that can apply the coating with high precision. Moths seek light in the dark. To maximize the amount of light entering their eyes, to help them see at night, the insects' eyes are covered in tapered nanostructures. This creates an 'effective medium' where the refractive index gradually increases as light travels from air through to the insects' optical nerve. The resulting effective index is graded from close to one at the top to close to 3.4 at the bottom, which means that very little light is reflected out of the eye. Inspired by these biostructures, the researchers have mimicked the effect by growing nanowires of different lengths - creating a metamaterial with optical properties that change gradually as a function of distance. The team used gallium phosphide (GaP) nanorods on top of a GaP substrate, then measured reflection and transmission simultaneously. They showed for the first time that light transmission was dominant, with only a minor part of the reduced reflection linked with scattering losses and absorption, according to the researchers.
Physicsworld.com / Advanced Materials Feb 09, 2009	back to top

Batteries get a boost with hybrid nanocables
Need to store electricity more efficiently? Put it behind bars. That is essentially the finding of a team of Rice University researchers who have created hybrid carbon nanotube metal oxide arrays as electrode material that may improve the performance of lithium-ion batteries. The team described the proof-of-concept research in which nanotubes are grown to look and act like the coaxial conducting lines used in cables. The coax tubes consist of a manganese oxide shell and a highly conductive nanotube core. The researchers put in two materials – the nanotube, which is highly electrically conducting and can also absorb lithium, and the manganese oxide, which has very high capacity but poor electrical conductivity. The result of this combination would be the ability to hold a lot of juice and transmit it efficiently. The researchers expect the number of charge/discharge cycles such batteries can handle will be greatly enhanced, even with a larger capacity. The hybrid nanocables grown could also eliminate the need for binders, materials used in current batteries that hold the elements together but hinder their conductivity.
Eureka Alert / Rice University Feb 09, 2009	back to top