Issue no. 24, 2010
Published: Jul 16, 2010 |
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 Alternative nuclear fuel is surprisingly reactive |
| Artificial lung 'breathes' in rats: study |
| Graphene soaks up arsenic |
| Smoke-detector isotope to power space probes |
| Scientists create cloth that can listen |
| Old blue jeans recycled as solar panels? |
| Reconstructed: Archimedes's flaming steam cannon |
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| Alternative nuclear fuel is surprisingly reactive |
The threat of climate change and uncertain fossil fuel prices have made
nuclear power a tempting option for meeting some of the world's future
energy needs. The nuclear industry uses oxides of uranium and plutonium,
but some chemists think they could one day be replaced with uranium
nitrides. Uranium nitrides are denser and more stable, and conduct heat
better than mixed uranium-plutonium oxide fuels – properties that
suggest the fuels could run cooler in reactors to generate more energy.
But few uranium nitrides have been produced, and those that have are
large and complex, containing many uranium-nitride bonds. Understanding
how each bond reacts is critical to predicting its behaviour, both as a
nuclear fuel and later as nuclear waste. Now researchers at Los Alamos
National Laboratory have synthesised a molecule complex that is the
first known to contain just a single, isolated uranium-nitride bond.
The team created the uranium nitride unit by firing photons at a complex
containing uranium azide, molecules of which are made of one uranium
atom joined to a chain of three nitrogen atoms. The light excited the
electrons in the complex and caused the release of two nitrogen atoms,
leaving a triple-bonded uranium nitride molecule.
The team was surprised to find that the uranium nitride molecules
subsequently reacted with carbon-hydrogen bonds elsewhere within the
molecule complex. Such bonds are strong, and normally almost entirely
inert. Understanding the molecule's reactivity could have implications
for how nuclear fuels composed of uranium nitride are stored before and
after use. |
| New Scientist / Nature Chemistry
Jul 13, 2010 |
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| Artificial lung 'breathes' in rats: study |
US researchers have created a primitive artificial lung that rats used
to breathe for several hours and said on Tuesday it may be a step in the
development of new organs grown from a patient's own cells. The finding
is the second in a month from researchers seeking ways to regenerate
lungs from ordinary cells.
Researchers at Massachusetts General Hospital and Harvard Medical School
in Boston removed the cells from rat lungs to leave a scaffolding or
matrix. They soaked these in a bioreactor along with several types of
human lung cells, creating pressures to simulate the pressure inside a
body to make the lung workable and flexible. The cells took up residence
and grew into different tissue types seen in a lung. When transplanted
into rats, they worked for about six hours, although imperfectly.
The researchers said it may be possible to try the experiment with more
immature stem cells, the body's master cells. These could include
embryonic stem cells, which can mature into any cell type in the body,
or induced pluripotent stem cells - ordinary cells with genes added to
make them behave like flexible stem cells.
Last month, a team at Yale University implanted engineered lung tissue
into rats that helped the animals breathe for two hours. |
| Reuters / Nature Medicine
Jul 13, 2010 |
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| Graphene soaks up arsenic |
Researchers have found yet another use for the wonder material graphene.
A composite material made from reduced graphene oxide and magnetite
could effectively remove arsenic from drinking water. Arsenic is one of
the most carcinogenic elements known and is toxic above 10 ppb.
Graphene is a sheet of carbon just one atom thick that also exists as an
oxide. Reduced graphene oxide (RGO) is a chemical state of the material
that has gained electrons. The purification process works by dispersing
a magnetite-RGO composite in water, where it soaks up arsenic. The
composite is then quickly and efficiently removed from the water using a
permanent magnet.
Arsenic can be removed from drinking water by using activated carbon or
precipitating it out with iron minerals, such as iron oxides – for
example, magnetite (Fe3O4) nanocrystals. However, such particles cannot
be used in rivers, or other environments where water flows, because of
their small size and the fact that magnetite rapidly oxidizes when
exposed to the atmosphere. Researchers have recently overcome the latter
problem by combining iron oxides with carbon and carbon nanotubes, and
graphene-based materials such as graphene oxide.
Building on this work, researchers at Pohang University of Science and
Technology in South Korea have created a new type of magnetite composite
based on RGO. The hybrid material, which is superparamagnetic at room
temperature, can remove over 99.9% of arsenic in a sample and reduce its
concentration to below 1 ppb. |
| PhysicsWorld / ACS Nano
Jul 12, 2010 |
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| Smoke-detector isotope to power space probes |
What do spacecraft and smoke alarms have in common? A material commonly
used to detect smoke on Earth could soon power robotic missions to other
planets.
Previous spacecraft travelling to the outer solar system have been
powered by the decay of plutonium-238. The isotope is running out,
though and this could mean that there will not be enough plutonium-238
for a joint NASA and European Space Agency mission to Jupiter and its
icy moon, Europa, which is planned for launch around 2020.
ESA now plans to build up an alternative supply of americium-241. In
smoke detectors, the material's decay helps to make ions that trigger an
alarm when smoke particles attach to them. Americium-241 decays more
slowly than plutonium-238, potentially allowing for longer missions,
says Ralph McNutt of Johns Hopkins University in Baltimore, Maryland,
who co-authored a report on the plutonium-238 shortage in the US.
On the downside, it takes more of the material to supply one unit of
power, which could be a drawback for space missions, in which weight
must be kept at a minimum. |
| New Scientist
Jul 14, 2010 |
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| Scientists create cloth that can listen |
Scientists at MIT have created a cloth that gives a whole new meaning to
the phrase power dressing. The team has created a type of functional
fibre that can detect and produce sound.
According to the researchers, applications could include clothes that
are themselves sensitive microphones, for capturing speech or monitoring
bodily functions, and tiny filaments that could measure blood flow in
capillaries or pressure in the brain. The decade-old research project
aims to develop fibres with ever more sophisticated properties, to
enable fabrics that can interact with their environment, they say.
The new fibres are based on a similar plastic used in microphones.
Researchers manipulated the fluorine content to ensure its molecules
stayed lopsided. That imbalance makes the plastic piezoelectric, meaning
it changes shape when an electric field is applied.
In addition to wearable microphones and biological sensors, applications
of the fibres could include loose nets that monitor the flow of water in
the ocean and large-area sonar imaging systems with much higher
resolutions, the researchers say. A fabric woven from acoustic fibres
would provide the equivalent of millions of tiny acoustic sensors. |
| ABCnet / AFP / Nature Materials
Jul 13, 2010 |
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| Old blue jeans recycled as solar panels? |
Researchers at Cornell University have discovered a way to use the
molecules typically found in blue jean dyes to make an organic, flexible
framework that researchers hope to translate to better solar cells.
Today's solar cells are mostly made from silicon, but they can be heavy,
inflexible and inefficient. The researchers organised the dye molecules
into a covalent organic framework (COF), a bonded material that is very
light, porous and strong.
The process used an acid catalyst to reorder the molecules into a
two-dimensional sheet. The sheets were then stacked on top of each other
to make a crosshatched framework pathway to conduct the electrical
charge. The scientists used phthalocyanine, a molecule used to make blue
and green dyes in plastics and jeans.
The structure by itself is not a solar cell, but it is a model that will
significantly broaden the scope of materials that can be used in COFs,
according to the researchers. The next step is to begin testing ways of
filling the crosshatched framework with other organic molecules that
could lead to a flexible, lightweight material for solar cells. |
| MSNBC / Nature Chemistry
Jul 07, 2010 |
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| Reconstructed: Archimedes's flaming steam cannon |
The ancient Greek inventor Archimedes is said to have built fantastic
machines of war, ranging from catapults to giant claws, that were used
against the Romans during their siege of Syracuse, Sicily, in the third
century BC. One of the most controversial stories is that Archimedes set
fire to Roman ships by focusing the sun's rays onto them with concave
mirrors. Sceptics say it would be impossible to use mirrors to keep the
sun's rays focused on a moving ship. What's more, they say, the fires
would start slowly and could easily be put out by those on board.
Now Cesare Rossi of the University of Naples Federico II suggests an
alternative scenario. He points out that several scholars, including
Petrarch and Da Vinci, wrote that Archimedes invented a cannon which
used pressurised steam to force a projectile out of the barrel at high
speed. In 2006 a team at the MIT constructed such a cannon to their own
design and successfully tested it. Rossi reckons that steam cannon could
explain the mirror legend. He suggests that such a cannon could have
been heated by sun-focusing mirrors, while the projectiles would have
been hollow and filled with an incendiary fluid – perhaps a mixture of
sulphur, bitumen, pitch and calcium oxide.
Although using mirrors in this way might seem impractical, Rossi says it
would have made sense for the Syracusans to avoid using open fires as
the cannons would have been positioned on the city walls, on platforms
made of wood. Rossi calculates that a cannonball measuring 20
centimetres across would have weighed around 6 kilograms and could have
been fired from the gun at 60 metres per second. A gun positioned 10
metres above sea level and firing at an angle of 10 degrees to the
horizontal would have had a range of around 150 metres. |
| New Scientist
Jul 13, 2010 |
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