Showing posts with label method. Show all posts
Showing posts with label method. Show all posts
Monday, July 8, 2013
Sunday, July 7, 2013
Tuesday, April 23, 2013
NASA Uses New Method to Estimate Earth Mass Movements
Global present-day trends in the transport of water mass around Earth, as determined using data from GRACE, surface measurements and an ocean model. Darker areas represent greater loss of mass. Image credit: NASA-JPL/-Caltech› Larger image September 14, 2010
NASA and European researchers have conducted a novel study to simultaneously measure, for the first time, trends in how water is transported across Earth's surface and how the solid Earth responds to the retreat of glaciers following the last major Ice Age, including the shifting of Earth's center of mass.
To calculate the changes, scientists at NASA's Jet Propulsion Laboratory, Pasadena, Calif.; Delft University of Technology, Delft, Netherlands; and the Netherlands Institute for Space Research, Utrecht, Netherlands, combined gravity data from the NASA/German Aerospace Center Gravity Recovery and Climate Experiment satellites with direct measurements of global surface movements from GPS and other sources and a JPL-developed model that estimates the mass of Earth's ocean above any point on the ocean floor. Results are reported in the September issue of Nature Geoscience.
Using the new methodology, the researchers, led by Xiaoping Wu of JPL, calculated new estimates of ice loss in Greenland and Antarctica that are significantly smaller than previous estimates. According to the team's estimates, mass losses between 2002 and 2008 measured 104 (plus or minus 23) gigatonnes a year in Greenland, 101 (plus or minus 23) gigatonnes a year in Alaska/Yukon, and 64 (plus or minus 32) gigatonnes a year in West Antarctica. A gigatonne is one billion metric tons, or more than 2.2 trillion pounds. The smaller but significant ice loss estimates reflect the revised role that post-glacial rebound was found to play in relation to current ice mass loss in Greenland and Antarctica. Post-glacial rebound (known as glacial isostatic adjustment) is the response of the solid Earth to the retreat of glaciers following the last Ice Age. After the weight of ice from the land surface was removed, the land under the ice rose and continues to slowly rise.
In addition, the team found that the shift of water mass around the globe, combined with the post-glacial rebound of Earth's surface, is shifting Earth's surface relative to its center of mass by 0.88 millimeters (.035 inches) a year toward the North Pole. The estimate of the shift due to rebound-0.72 millimeters (.028 inches) per year--is believed to be the first estimate based on actual data, rather than a model prediction.
Wu said the shift of Earth's surface is due primarily to the melted Laurentide ice sheet, which blanketed most of Canada and a part of the northern United States around 21,000 years ago. "The new estimate of shift is much larger than previous model estimates of 0.48 millimeters [.019 inches] per year," said Wu. "This suggests that either Earth's lower mantle must be much more viscous than previously believed, or that the history of Earth's deglaciation needs to be significantly revised."
Wu said previous GRACE-based estimates of the movement of mass at Earth's surface have been calculated by correcting the data using a post-glacial rebound model, while estimates of post-glacial rebound itself have been estimated using a hydrological model. These models are not as precise as the geodetic data, however, and contain unknown and potentially large errors that will throw off estimates of the other process.
GRACE project scientist Michael Watkins of JPL, who was not an author on the paper, said that although some of the new results, such as those for Greenland, are surprising, they are not due to a reanalysis of GRACE or GPS data alone. Rather, they are a result of the simultaneous use of GRACE, GPS and other geodetic measurements to help objectively sort out the relative sizes of post-glacial rebound and present-day ice mass loss. "Both the GPS and gravity measurements are accurate on their own, but untangling the relative contributions of the two processes as observed by satellites is difficult. This technique provides a first global attempt at doing that," Watkins said.
"The Earth system is so complex that measuring and understanding it requires scientists to combine observations from as many satellites and ground-based measurements as possible," Watkins added. "With each new study like this one, we learn more and more about how to conduct future studies and interpret their data. The more data, and different types of data we collect, the better we'll be able to answer fundamental questions about how our planet works."
Alan Buis 818-354-0474
Jet Propulsion Laboratory, Pasadena, Calif.
Alan.buis@jpl.nasa.gov
2010-298
Thursday, April 18, 2013
Material screening method allows more precise control over stem cells
William Murphy, the Harvey D. Spangler professor of biomedical engineering(Phys.org) —When it comes to delivering genes to living human tissue, the odds of success come down the molecule. The entire therapy - including the tools used to bring new genetic material into a cell - must have predictable effects. 
Provided by University of Wisconsin-Madison
Now, a new screening process will simplify non-viral transfection, providing a method researchers and clinicians to use to find an optimal set of biomaterials to deliver genes to cells.
Developed by William Murphy, the Harvey D. Spangler professor of biomedical engineering at the University of Wisconsin-Madison, the method gives researchers greater control over how cells react to the gene delivery mechanism. The broader implication is more nuanced, effective control over cell behavior. "We've been exploring using this concept for reprogramming of adult cells, as well as controlling differentiation of stem cell types," he says.
Murphy and his collaborators published news of their advance in the March 28, 2013 issue of Nature's Scientific Reports.
In a current successful approach, researchers use specialized viruses to deliver genetic material to cells. While efficient, that method also carries a greater risk of turning on unwanted genes or provoking an immune response from the body—making it less attractive for sensitive biomedical applications like controlling stem cell behavior, says Murphy.
His team has developed a process that does not rely on viruses. Rather, the researchers can grow specific calcium phosphate coatings that serve as a medium via which genetic material can be delivered to cells more efficiently. By matching a coating to a specific application for delivering genes, Murphy has seen up to a 70-fold increase in successful expression of those genes in human stem cells.
"From an application standpoint, the advance could be really impactful, and could enable gene delivery to become an integral part of medical device design and tissue engineering applications," says Murphy.
The process could be critical to further advances in regenerative medicine. Since researchers can apply it to any size or shape of tissue engineering structure, it could help provide engineers a simpler way to build the complex tissue structures required to deliver next-generation drug screening and patient therapies.
More information: www.nature.com/srep/2013/130328/srep01567/full/srep01567.html
Provided by University of Wisconsin-Madison [News & Analysis] Neuroscience: Tissue Imaging Method Makes Everything Clear
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Wednesday, April 10, 2013
New method for uncovering side effects before a drug hits the market
Side effects are a major reason that drugs are taken off the market and a major reason why patients stop taking their medications, but scientists are now reporting the development of a new way to predict those adverse reactions ahead of time. The report on the method, which could save patients from severe side effects and save drug companies time and money, appears in ACS' Journal of Chemical Information and Modeling.
Yoshihiro Yamanishi and colleagues explain that drug side effects are a major health problem—the fourth-leading cause of death in the U.S.—which by some estimates claim 100,000 lives every year. Serious side effects are the main reason why existing drugs must be removed from the market and why pharmaceutical companies halt development of new drugs after investing millions of dollars. Current methods of testing for side effects are costly and inaccurate. That's why the scientists sought to develop a new computer-based approach to predicting possible side effects.
They show the usefulness of their proposed method on simultaneous prediction of 969 side effects of 658 drugs that already are in wide medical use. The method is based on knowledge about chemical and biological information about ingredients in these medications. They also used the approach to identify possible side effects for many uncharacterized molecules. Based on that work, the scientists conclude that the new method could be helpful in uncovering serious side effects early in the development and testing of new drugs, avoiding costly investment in medications unsuitable for marketing.
More information: Drug Side-Effect Prediction Based on the Integration of Chemical and Biological Spaces, J. Chem. Inf. Model., 2012, 52 (12), pp 3284–3292. DOI: 10.1021/ci2005548
Abstract
Drug side-effects, or adverse drug reactions, have become a major public health concern and remain one of the main causes of drug failure and of drug withdrawal once they have reached the market. Therefore, the identification of potential severe side-effects is a challenging issue. In this paper, we develop a new method to predict potential side-effect profiles of drug candidate molecules based on their chemical structures and target protein information on a large scale. We propose several extensions of kernel regression model for multiple responses to deal with heterogeneous data sources. The originality lies in the integration of the chemical space of drug chemical structures and the biological space of drug target proteins in a unified framework. As a result, we demonstrate the usefulness of the proposed method on the simultaneous prediction of 969 side-effects for approved drugs from their chemical substructure and target protein profiles and show that the prediction accuracy consistently improves owing to the proposed regression model and integration of chemical and biological information. We also conduct a comprehensive side-effect prediction for uncharacterized drug molecules stored in DrugBank and confirm interesting predictions using independent information sources. The proposed method is expected to be useful at many stages of the drug development process.
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