ScienceDaily (Feb. 8, 2010) — Workers exposed to tricholorethylene (TCE), a chemical once widely used to clean metal such as auto parts, may be at a significantly higher risk of developing Parkinson's disease, according to a study released today that will be presented at the American Academy of Neurology's 62nd Annual Meeting in Toronto April 10 to April 17, 2010.

"This is the first time a population-based study has confirmed case reports that exposure to TCE may increase a person's risk of developing Parkinson's disease," said study author Samuel Goldman, MD, with the Parkinson's Institute in Sunnyvale, California, and a member of the American Academy of Neurology. "TCE was once a popular industrial solvent used in dry cleaning and to clean grease off metal parts, but due to other health concerns the chemical is no longer widely used."

For the study, researchers obtained job histories from 99 pairs of twins in which only one of the twins had Parkinson's disease. All of the twins were men and identified from the World War II-Veterans Twins Cohort study. Scientists used twins in the study because they are genetically identical or very similar and provide an ideal population for evaluating environmental risk factors.

The study found workers who were exposed to TCE were five and a half times more likely to have Parkinson's disease than people not exposed to the chemical. Those who were exposed to TCE had job histories including work as dry cleaners, machinists, mechanics or electricians.

The study was supported by grants from the National Institute of Neurological Disorders and Stroke, The Valley Foundation and the James and Sharron Clark Family Fund.

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Adapted from materials provided by American Academy of Neurology.

ScienceDaily (Feb. 7, 2010) — In a just-published paper in the magazine Science, IBM researchers demonstrated a radio-frequency graphene transistor with the highest cut-off frequency achieved so far for any graphene device -- 100 billion cycles/second (100 GigaHertz).

This accomplishment is a key milestone for the Carbon Electronics for RF Applications (CERA) program funded by DARPA, in an effort to develop next-generation communication devices.

The high frequency record was achieved using wafer-scale, epitaxially grown graphene using processing technology compatible to that used in advanced silicon device fabrication.

"A key advantage of graphene lies in the very high speeds in which electrons propagate, which is essential for achieving high-speed, high-performance next generation transistors," said Dr. T.C. Chen, vice president, Science and Technology, IBM Research. "The breakthrough we are announcing demonstrates clearly that graphene can be utilized to produce high performance devices and integrated circuits."

Graphene is a single atom-thick layer of carbon atoms bonded in a hexagonal honeycomb-like arrangement. This two-dimensional form of carbon has unique electrical, optical, mechanical and thermal properties and its technological applications are being explored intensely.

Uniform and high-quality graphene wafers were synthesized by thermal decomposition of a silicon carbide (SiC) substrate. The graphene transistor itself utilized a metal top-gate architecture and a novel gate insulator stack involving a polymer and a high dielectric constant oxide. The gate length was modest, 240 nanometers, leaving plenty of space for further optimization of its performance by scaling down the gate length.

It is noteworthy that the frequency performance of the graphene device already exceeds the cut-off frequency of state-of-the-art silicon transistors of the same gate length (~ 40 GigaHertz). Similar performance was obtained from devices based on graphene obtained from natural graphite, proving that high performance can be obtained from graphene of different origins. Previously, the team had demonstrated graphene transistors with a cut-off frequency of 26 GigaHertz using graphene flakes extracted from natural graphite.

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Adapted from materials provided by IBM.

ScienceDaily (Feb. 7, 2010) — Scientists at the Department of Microsystems Engineering (IMTEK) and the Freiburg Materials Research Center (FMF) have succeeded in developing a method for treating the surface of nanoparticles which greatly improves the efficiency of organic solar cells. The researchers were able to attain an efficiency of 2 percent by using so-called quantum dots composed of cadmium selenide.

These measurements, well above the previous efficiency ratings of 1 to 1.8 percent, were confirmed by the "Dye and Organic Solar Cells" research group of the Fraunhofer Institute for Solar Energy Systems at the FMF. The photoactive layer of hybrid solar cells consists of a mixture of inorganic nanoparticles and an organic polymer. As it is theoretically possible to apply the method developed by the researchers to many nanoparticles, this breakthrough opens up new potential for increasing the efficiency of this type of solar cell even further.

The procedure has been patented and the results were published in a recent issue of the journal Applied Physics Letters.

Organic solar cells belong to the so-called third generation of solar cells and are still in the developmental stage. The world record for purely organic solar cells, a type in which both components of the photoactive layer consist of organic materials, is currently at 7 percent for layers created through wet chemical methods. Organic solar cells have many advantages over the conventional silicon cells typically used for large-scale energy production: Not only are they are considerably thinner and more flexible, they are also less expensive and quicker to produce. They are thus better suited for powering everyday devices and systems which are not in constant use, such as sensors or electrical appliances. In the long run, organic solar cells could drastically reduce our dependence on batteries and cables.

The research group which developed the groundbreaking new solar cells is a close-knit team of chemists, physicists, and engineers from IMTEK and FMF.

"The interdisciplinary orientation of the group is a clear advantage and has led to rapid progress on the project. We were able to carry out all of the steps on our own: from the synthesis of the nanoparticles to the modification of their surface and integration into composite materials," says group head Dr. Michael Krüger. His "Nanosciences" research group is part of the Chair for Sensors at IMTEK held by Prof. Dr. Gerald Urban. The group is now applying the methods described in the publication to other promising materials systems -- also as part of a joint research project sponsored by the German Federal Ministry of Education and Research -- in order to refine them further and shape them into a market-ready technology. The necessary preconditions for marketability are marked improvements in efficiency, a further increase in the durability of the materials, and a reduction in production costs.

The project "Quantum Dot Polymer Hybrids as Photoactive Material in Solar Cells" receives funding from the German Research Foundation through the IMTEK research training group "Micro Energy Harvesting."

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Adapted from materials provided by Albert-Ludwigs-Universität Freiburg, via AlphaGalileo.

ScienceDaily (Feb. 6, 2010) — Scientists have published the first report on a new way of preventing potentially harmful plasticizers -- the source of long-standing human health concerns -- from migrating from one of the most widely used groups of plastics. The advance could lead to a new generation of polyvinyl chloride (PVC) plastics that are safer than those now used in packaging, medical tubing, toys, and other products, they say.

Their study is in the American Chemical Society's Macromolecules, a bi-weekly journal.

Helmut Reinecke and colleagues note that manufacturers add large amounts of plasticizers to PVC to make it flexible and durable. Plasticizers may account for more than one-third of the weight of some PVC products. Phthalates are the mainstay plasticizers. Unfortunately, they migrate to the surface of the plastic over time and escape into the environment. As a result, PVC plastics become less flexible and durable. In addition, people who come into contact with the plastics face possible health risks. The U.S. Consumer Product Safety Commission in 2009 banned use of several phthalate plasticizers for use in manufacture of toys and child care articles.

The scientists describe development of a way to make phthalate permanently bond, or chemically attach to, the internal structure of PVC so that it will not migrate. Laboratory tests showed that the method completely suppressed the migration of plasticizer to the surface of the plastic. "This approach may open new ways to the preparation of flexible PVC with permanent plasticizer effect and zero migration," the article notes.

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Adapted from materials provided by American Chemical Society, via EurekAlert!, a service of AAAS.

Journal Reference:

1. Navarro et al. Phthalate Plasticizers Covalently Bound to PVC: Plasticization with Suppressed Migration. Macromolecules, 2010; 100121082610027 DOI: 10.1021/ma902740t

ScienceDaily (Feb. 6, 2010) — Using an elaborate sleuthing system they developed to probe how cells manage their own division, Johns Hopkins scientists have discovered that common but hard-to-see sugar switches are partly in control.

Because these previously unrecognized sugar switches are so abundant and potential targets of manipulation by drugs, the discovery of their role has implications for new treatments for a number of diseases, including cancer, the scientists say.

In the January 12 edition of Science Signaling, the team reported that it focused efforts on the apparatus that enables a human cell to split into two, a complicated biochemical machine involving hundreds of proteins. Conventional wisdom was that the job of turning these proteins on and off -- thus determining if, how and when a cell divides -- fell to phosphates, chemical compounds containing the element phosphorus, which fasten to and unfasten from proteins in a process called phosphorylation.

Instead, the Johns Hopkins scientists say, there is another layer of regulation by a process of sugar-based protein modification called O-GlcNAcylation (pronounced O-glick-NAC-alation). "This sugar-based system seems as influential and ubiquitous a cell-division signaling pathway as its phosphate counterpart and, indeed, even plays a role in regulating phosphorylation itself," says Chad Slawson, Ph.D., an author of the paper and research associate in the Department of Biological Chemistry, Johns Hopkins University School of Medicine.

Because the sugar molecule has some novel qualities -- it is small, easily altered, and without an electrical charge -- it is virtually imperceptible to researchers using standard physical techniques of detection such as mass spectrometry.

Suspecting that the sugar known as O-GlcNAc might play a role in cell division, the Hopkins team devised a protein-mapping scheme using new mass spectrometric methods. Essentially, they applied a combination of chemical modification and enrichment methods, and new fragmentation technology to proteins that comprise the cell division machinery in order to out and analyze their molecular makeup, identifying more than 150 sites where the sugar molecule known as O-GlcNAc was attached. Phosphates were found to be attached at more than 300 sites.

They noticed that when an O-GlcNAc molecule was located near a phosphate site, or at the same site, it prevented the phosphate from attaching. The proteins involved in cell division weren't phosphorylated and activated until O-GlcNAc detached.

"I think of phosphorylation as a micro-switch that regulates the circuitry of cell division, and O-GlcNAcylation as the safety switch that regulates the microswitches," says Gerald Hart, Ph.D., the DeLamar Professor and director of biological chemistry at the Johns Hopkins School of Medicine.

Using a standard human cell line (HeLa cells), the scientists discovered abnormalities when they disrupted the cell division process by adding extra O-GlcNAc. Although the cell's chromosome-containing nuclei divided normally, the cells themselves didn't divide, resulting in too many nuclei per cell -- a condition known as polyploidy that's exhibited by many cancer cells.

The researchers not only mapped O-GlcNAc and phosphorylation sites but also measured changes in the cell division machinery, because, Hart says, the chemical changes act more like "dimmer" switches, than simple on/off ones.

As important as the discovery is to a deeper understanding of cell division, Hart says, this extensive cross talk between O-GlcNAc and phosphorylation is paradigm-shifting in terms of signaling. Signaling is how a cell perceives its environment, and how it regulates its machinery in response to stimuli. The new sugar switches reveal that the cellular circuitry is much more complex than previously thought, he adds.

The research was funded by the National Institutes of Health.

Johns Hopkins authors on the paper are Zihao Wang, Chad Slawson, Kaoru Sakabe, Win D. Cheung and Gerald W. Hart. Other authors are Namrata D. Udeshi, Philip D. Compton, Jeffrey Shabanowitz and Donald F. Hunt, all of the University of Virginia.

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Adapted from materials provided by Johns Hopkins Medical Institutions, via EurekAlert!, a service of AAAS.