NASA prepares to launch mission to nearby asteroids
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Wednesday, September 19, 2007
NASA is beginning the final preparations for next Wednesday’s launch of the Dawn probe, aboard a Delta II rocket. The Dawn probe, costing over US$250 million, will visit the dwarf planet Ceres and the asteroid Vesta. The launch was originally planned for mid-June, however due to a damaged crate, shipping delays, and a damaged solar panel, NASA chose to delay it until now. Last week the spacecraft was delivered to the launch pad, and engineers performed tests to ensure that it is ready for launch. Today, the payload fairings were installed, and the probe is ready for its launch next week onto its 5 billion kilometer (3.2 billion mile) mission.
As the Delta II launches, three stages of rockets will propel the probe towards its first target. With the help of ion thrusters, it will reach Mars in mid-2009. Using Mars’ gravity, the probe will speed up and proceed towards the first asteroid, Vesta, in late 2011. After orbiting for seven months, it will leave Vesta in mid-2012, and arrive at Ceres in 2015. After making scans of Ceres, it will enter an orbit around Ceres that will ensure that it does not impact the asteroid for half a century. This is required due to the United Nations’ “Outer Space Treaty”, which states that “harmful contamination” of these asteroids must be avoided.
The targets of this mission, Ceres and Vesta, couldn’t be less alike. Ceres (diameter 975 km, 600 miles) is larger than Vesta (578 km, 350 miles). This makes Ceres approximately the size of Texas. NASA believes Ceres could contain water beneath its outer crust because, like Earth, its inner layers are heavier than the outer layers, and Ceres’ outer layer is lighter than water. Vesta, on the other hand, is the size of Arizona, and has a surface of volcanic rock, which astronomers believe came from its hot inner layers. Vesta also has a large crater – almost 500 km (300 miles) across – on its southern pole. The collision that caused this likely blasted enough rock into space to fill a container 160 by 160 by 80 km (100 by 100 by 50 miles).
The probe will make several observations of these asteroids: it will compare the makeup, shape, size, and densities, analyze craters, and determine mass, gravity, rotation. To determine the makeup, the probe carries a mapping spectrometer, and tools to map emissions of neutrons and gamma rays. Using this information, NASA can compare the formation of these bodies to learn more about our solar system, for example, to test a theory which states that a number of stony meteorites may be debris from Vesta.
There’s one more piece of equipment aboard the probe: A small silicon chip containing the names of 350,000 people who submitted their names to the “Send Your Name to the Asteroid Belt” campaign. After next week’s launch, the spacecraft will deploy its solar panels and undergo two months of testing before it begins the cruise to Mars.
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Incomplete data may mislead doctors into overprescribing expensive medicines
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Thursday, September 25, 2008
Medical doctors have not been getting the full picture about newly FDA-approved drugs, concludes a research team from the University of California, San Francisco. This is because not all the studies required for FDA approval get published. New drug studies that do see publication tend to be ones where the medicine appears to perform well while poor and middling results are less likely to appear in medical journals. The result appears to be that doctors who read the available literature may get an inflated impression of new medications and may prescribe expensive new drugs in place of older medicines that perform as well or better. As Jordan Lite of Scientific American wonders, are drug companies cherry-picking the studies they publish to make their drugs look better than they actually are?
The University of California team reviewed trials that had supported new drugs approved from 1998 to 2000 and examined 909 trials of 90 medications. The search was conducted upon PubMed and other search tools that a typical medical doctor or patient could access. They concluded that less than half of the studies had been published five years after drug approval and a publication bias existed.
Erick Turner, who coauthored a similar study earlier this year, expressed concerns to Scientific American that the problem was not merely the raw percentage of studies published, but that a disproportionate share of the research that appeared in journals are examples where new medications appear to perform well:
| When trials are selectively published … it will skew the efficacy of the drug and make it look like it works better than it does. | ||
- When trials are selectively published … it will skew the efficacy of the drug and make it look like it works better than it does. It’s going to create a lot more enthusiasm among consumers of that information or in the words of Alan Greenspan, ‘irrational exuberance.’
Ken Johnson, senior vice president of the Pharmaceutical Research and Manufacturers of America (PhRMA), defended the pharmaceutical industry by saying FDA review of new drug applications is more important than publishing the results of medication trials in medical journals. Approved medications come with labels that give patients and doctors enough information, assures Mr. Johnson.
Yet concerns about full and appropriate disclosure have been serious enough that a new law was enacted last year. FDA Amendments Act of 2007 (FDAAA) requires that all trials which support FDA-approved drugs be registered at the National Institutes of Health website. The requirement goes into effect this coming Saturday. Congress enacted the legislation in response to hearings that determined pharmaceutical companies were less likely to publish studies that indicated significant side effects. One shortcoming in the legislation, according to UCSF associate professor Ida Sim, is that the FDA is still not required to specify which trials it weighs when considering applications for drug approvals. Yet she praises the new law as a major improvement. It’s critically important that we know trials exist and that we get the summary results, positive and negative, into the public domain—that’s a huge step and more than any [other] country is doing now.
