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Wednesday, July 13, 2005

The U.S. space agency NASA called off the launch of Space shuttle Discovery today after a problem with a fuel sensor in the external tank used to detect fuel exhaustion. According to the agency-run NASA TV, the low-fuel sensor was either malfunctioning or damaged. The launch was already facing the threat of a scrub due to thunderstorms in the area.

The sensor is one of four used to trigger the engine cutout after launch. Although only two are required for normal operation, and the Shuttle can be flown with one, NASA elected to maintain full redundancy. Should more of the sensors fail, the engine might burn out due to lack of fuel, a situation that has not been tested.

The problem was detected during a simulation of an empty tank. When placed in a mode simulating an empty tank, three of the sensors correctly registered that the tank was empty, while the faulty sensor stayed in the “full” state. NASA is currently unsure whether the problem relates to the sensor, the instrumentation circuits reporting the sensor’s state, or the simulation circuits.

The problem comes after a separate incident yesterday when a cockpit window cover fell from the Orbiter, damaging thermal protection tiles. A similar problem caused the replacement of the fuel tank in June. NASA described the problem as an “intermittent fault”.

The launch, which was scheduled for 3:51 ET (20:51 UTC), would have been the first launch of a shuttle since Columbia‘s February 2003 crash which killed all crew members aboard.

It is still unknown to NASA officials what caused the sensor to become defective. It is also unknown at the moment whether the issue will be fixed on the launch pad, or in the Vehicle Assembly Building – in which it takes close to a full day’s time to transport a shuttle between the two areas.

In the interim, the crew of the shuttle will stay at KSC unless there are further delays, in which case the crew might be transported back to JSC in Houston for refresher training.

Tuesday, September 16, 2008

The International Monetary Fund and the European Union approved aid packages to help Georgia recover from its conflict with Russia, which occurred in early August. The IMF approved a US$750 million loan which will allow Georgia to rebuild its currency reserves. The European Union also approved an aid package of €500 million in aid by 2010, which is expected to help internally displaced people (IDPs) and economic recovery in the form of new infrastructure. Only €100 million of the EU aid will be given to Georgia this year.

These loans are aimed to restore confidence in Georgia’s economy and send a signal to international investors that Georgia’s economy is sound. According to the IMF, international investors have been “critical to Georgia’s economic growth in recent years.”

Takatoshi Kato, Deputy Managing Director and Acting Chairman of the IMF executive committee, said the loan will “make significant resources available to replenish international reserves and bolster investor confidence, with the aim of sustaining private capital inflows that have been critical to Georgia’s economic growth in recent years.”

Georgia has requested $2 billion in international aid to help it recover from the conflict. So far, the United States has pledged $1 billion in aid. Further assistance and loans to Georgia are expected from other organizations. Kato noted that “…Georgia is expected to receive financial assistance from multilateral and bilateral donors and creditors in support of the reconstruction effort.” It is expected that an international donors’ conference will take place next month to solicit more aid for the country.

Georgia’s government expects that economic growth will be more than cut in half as a result of the conflict. Last year, Georgia’s GDP increased 12.4% and it is predicted by the IMF that growth will be less than 4 percent in the coming year.

Sunday, August 29, 2010

A University of Tokyo group of researchers, led by bioengineer Shoji Takeuchi, has made an electronic sensor capable of smelling gases. The sensor uses genetically engineered frog cells. Since previous sensors were not very accurate, the scientist decided to try a biological approach. The invention was revealed in a US scientific journal yesterday, and is supposed to be used to design better machines to detect polluting gases in the atmosphere.

Previous smell sensors were based on quartz rods, which vibrate when a substance binds to them. The gases are distinguished by their molar masses, which can be similar for molecules with different structure, thus relatively often triggering a false positive. Trying to find a more accurate solution, Takeuchi decided to follow an example from insect world. As he explained, “when you think about the mosquito, it is able to find people because of carbon dioxide from the human. So the mosquito has CO₂ receptors. When we can (extract) DNA (from the mosquito) we can put this DNA into the frog eggs to detect CO₂.”

Genes of several insects (the silk moth, diamondback moth and fruit fly), injected into African clawed frog Xenopus laevis eggs, allowed them to produce relatively inexpensive and useful sensors. The choice of the species was caused by their widely studied and well-understood protein expression mechanism.

The modified cells responded to three kinds of pheromones and one odourant, which have similar chemical properties. When a molecule of an odorous substance adhered to the receptor on the membrane protein, ion channels opened for a certain period of time, and a current was generated. Its magnitude was clearly different for all four tested substances, allowing to distinguish between them accurately.

The colleagues embedded the sensor into a mannequin, so that it could shake its head when a gas was detected. It was easier to observe. Pheromones and molecules with quite similar molecule structure produced clearly distinguishable reaction, with higher accuracy than other biological or human-made sensors. As the research group said, the detection sensitivity of the odor sensor is several tens of parts per billion (ppb), and it is as high as the sensitivity of an existing odor sensor that uses an oxide semiconductor. The distinctive feature of the new sensor is its capability to selectively detect some odorous substances, rather than its sensitivity. Very few false positives were possible due to the biological mechanism involved.

At normal temperature, the sensor lifetime is about 12 hours, which can be extended by putting it into a refrigerator before first use.

Shoji Takeuchi says has a great hope for research use in future, since the frog eggs are very practical for genetic engineering, and can be conveniently used to develop smell sensors for a wide range of gases. He said, “The X. laevis oocyte has high versatility for the development of chemical sensors for various odorants. We believe that a shared ability to smell might open a new relationship between man and robot. .. The research will have wide implications… If the sensor is embedded in a nursing robot, it will be able to identify certain mouth odors or body odors. Also, it can be used for detecting CO₂, air pollution, water pollution and food. It’s very important for the environment.”