| |
|
|
Issue no. 16, 2010
Published: May 07, 2010 |
|
 Elusive tetraquark spotted in a data forest | | Is water the key to cheaper nanoelectronics? | | Lasers could be used to make rain | | Cheap hydrogen fuel from seawater may be a step closer | | MIT researchers print solar cell on paper | | Green machine: Generating more light than heat |
|
| Elusive tetraquark spotted in a data forest |
Particle hunters are claiming a sighting of a tetraquark. A jumbo
particle made up of four quarks, it is a hitherto undiscovered form of
matter. Tetraquarks were first posited to exist over 30 years ago, as
solutions to the equations of quantum chromodynamics.
In 2003, results from the BELLE collaboration at the KEK particle
accelerator in Tsukuba, Japan, hinted at the existence of a pentaquark.
Subsequent analyses of data from other experiments seemed to confirm
this, but other groups were unable to recreate Belle's results. As the
pentaquark evidence dried up, a number of possible tetraquark sightings
have been made by groups at KEK in Japan, the SLAC National Accelerator
Laboratory in Stanford, California, and D-Zero at the Fermilab
accelerator in Illinois.
Now researchers at the German Electron Synchrotron (DESY) in Hamburg,
Germany, have found another tetraquark candidate while looking to
explain an anomaly reported in 2008. BELLE researchers had collided
beams of electrons and positrons in an attempt to create an energetic
form of 'bottomonium' - a meson made of a bottom quark and its
antiparticle. Their product of their collisions, however, decayed much
faster than predicted. The researchers found that if a tetraquark made
of one bottom quark, one up quark, and each of their anti-particles was
created instead of bottomonium, the faster decay could be explained. |
| New Scientist / Physical Review Letters
May 04, 2010 |
 back to top
|
|
| Is water the key to cheaper nanoelectronics? |
To get complicated nanostructures on a silicon chip it is sometimes
necessary to grow them in separate layers and then transfer these one by
one onto the final chip to build them into working components. Often it
takes strong chemicals to separate the layers from the surface on which
they are grown, and high temperatures may be needed to activate the
thermal adhesives that keep the components in place.
Researchers at the Kavli Institute of Nanoscience in Delft, the
Netherlands, have found a way to use water to quickly and easily
transfer layers from one surface to another. They exploit the fact that
different materials have different hydrophilicity - the tendency to
attract water through transient hydrogen bonds.
The team took a relatively hydrophilic silicon wafer onto which a
graphene structure had been deposited in the required pattern. Then they
dipped it into a solution containing a hydrophobic polymer that dried to
form a strong, solid hydrophobic layer on top of the wafer. Next, they
submerged the wafer in water. Because graphene is equally hydrophobic,
the water molecules muscled both layers out of the way to wet the
hydrophilic silicon beneath it, gradually 'wedging' them off the silicon
base. The polymer-graphene film then floated to the water surface.
The team then placed a second silicon wafer beneath the floating film
and used a needle to prod the film into position before draining away
the water. Intermolecular forces between the graphene and silicon then
provided a stable attachment, removing the need for glue. They then
dissolved away the hydrophobic polymer to leave the graphene attached to
the new wafer. Repeating the technique several times would allow
graphene layers to be built up into a complex electronic nanostructure. |
| New Scientist / Nano Letters
May 06, 2010 |
back to top
|
|
| Lasers could be used to make rain |
Optical physicists from the University of Geneva in Switzerland and the
Free University of Berlin have shown that lasers can be used to create
tiny water droplets when they are fired into the air. The idea could
eventually develop into an alternative to cloud seeding as a way of
stimulating rainfall.
The researchers reasoned that shooting a laser into the air would ionize
oxygen and nitrogen molecules around the laser beam forming a 'plasma
channel' of ionized molecules, which could then act as condensation
nuclei. To test the idea, they used a laboratory cloud chamber and fired
short pulses of infrared laser light into the chamber in conditions of
low temperature and very high (230%) humidity. A second low-powered
laser was used to illuminate the chamber and allow them to observe what
was happening, and measure any water droplets produced.
After the laser was fired microscopic droplets formed immediately along
the plasma channel, forming a miniature linear cloud, and the drops then
coalesced to form larger droplets during the three seconds after firing.
The total volume of condensed water in the chamber was increased by 50%
and the cloud could be seen with the naked eye. |
| PhysOrg.com / Nature Photonics
May 04, 2010 |
back to top
|
|
| Cheap hydrogen fuel from seawater may be a step closer |
A new catalyst has been developed by scientists at the University of
California, Berkeley, to generate hydrogen from water cheaply.
Conventional catalysts capable of splitting water into hydrogen and
oxygen are generally too expensive or too weak to work on water
effectively enough to produce hydrogen for an inexpensive fuel, but new
research has developed a molybdenum catalyst that is robust and cheap
enough to do the job.
The new study aimed at combining metal atoms with organic molecular
groups to produce molecules with the properties of bulk magnets. The
researchers found that one of their molecules, a molybdenum-oxo complex,
was capable of transferring electrons. This is a major requirement of
water-splitting systems, so they tested its ability to split water to
generate hydrogen gas and found it was highly successful.
The molybdenum compound was so successful it could work on seawater or
pure water without additives. The compound is stable due to five bonds
holding the molybdenum in place. The researchers say the molecule is
stable for long periods in aqueous solutions, and shows no degradation
in catalytic activity over their three-day experiment. The molecule
remains stable even when impurities, such as those found in seawater,
are present. This would further reduce the cost since no organic acids
or solvents are needed. |
| PhysOrg.com / Nature
Apr 29, 2010 |
back to top
|
|
| MIT researchers print solar cell on paper |
Scientists at MIT have successfully coated paper with a solar cell, part
of a suite of research projects aimed at energy breakthroughs.
The technique, in which paper is coated with organic semiconductor
material using a process similar to an inkjet printer, is a promising
way to lower the weight of solar panels. The materials MIT researchers
used are carbon-based dyes and the cells are about 1.5% to 2% efficient
at converting sunlight to electricity. But any material could be used if
it can be deposited at room temperature.
The paper solar cells are one of many avenues being pursued around
nanoscale materials at the Eni-MIT Solar Frontiers Center. Layers of
these materials could essentially be sprayed using different
manufacturing techniques to make a thin-film solar cell on a plastic,
paper, or metal foils.
MIT is focusing much of its effort on quantum dots, or tiny crystals
that are only a few nanometres in size. By using different materials and
sizes, researchers can fine-tune the colours of light that quantum dots
can absorb, a way of isolating good candidates for quantum dot solar
cells. Researchers at the centre are also looking at different molecules
or biological elements which can act as solar cell material. These cheap
thin-film materials can be used on their own or added to silicon-based
solar panels to enhance the efficiency. |
| CNN / CNET
May 06, 2010 |
back to top
|
|
| Green machine: Generating more light than heat |
Not only are fossil-fuel-fired power plants major polluters, they are
also inefficient. Most of the energy in the fuel is lost as heat.
Salvaging some of this energy to reduce our consumption of coal and
natural gas is not a new idea. Combined heat and power stations already
do this, using the waste heat to keep local homes warm.
But most power plants are sited far from towns and cities, making it
impossible to use the heat in this way. So efforts are under way to
convert the heat into useable electricity. One option is to use a twist
on the Rankine cycle - the thermodynamic cycle used in power stations
whereby superheated steam is generated in a boiler, drives a turbine and
is then fed back to the boiler.
Among others, GE Global Research based in Munich, Germany, is developing
'organic' Rankine cycle technologies for waste heat recovery. These
systems use a refrigerant liquid with a lower boiling point than water,
meaning less energy is required to transform it into a high-pressure
vapour to drive a turbine. However, such technologies are costly because
they involve installing new generators to existing power plants.
Alphabet Energy, a spin-out company from the Lawrence Berkeley National
Laboratory, aims to cut the cost of waste heat recovery using a
thermoelectric device that can convert a temperature difference across
its surface into a current. The company claims that this could offset as
much as 500m tonnes of carbon per year worldwide. But it refuses to
reveal how the company's device works. |
| New Scientist
May 04, 2010 |
back to top
|
|
|
