September 26, 2011
Physics News Highlights of the American Institute of Physics (AIP) contains summaries of interesting research from the AIP journals, notices of upcoming meetings, and other information from the AIP Member Societies. Copies of papers are available to journalists upon request.
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Rapid cooling of ordinary water or compression of ordinary ice: either of these can transform normal H2O into an exotic substance that resembles glass in its transparency, brittleness, hardness, and luster. Unlike everyday ice, which has a highly organized crystalline structure, this glass-like material’s molecules are arranged in a random, disorganized way. Scientists have studied glassy water for decades, but the exact temperature at which water acquires glass-like properties has been the subject of heated debate for years, due to the difficulty of manipulating pure glassy water in laboratories. Now, in a paper published in the AIP’s Journal of Chemical Physics, physicists from the University of Pisa and the Consiglio Nazionale delle Ricerche at the Institute for Chemical-Physical Processes (CNR-IPCF) in Pisa, Italy, claim to have put an end to the controversy. Unlike previous attempts in which scientists tried to measure the transition temperature directly, the CNR team “snuck up” on the answer by inferring the temperature from a thorough study of the dynamics of water. They examined water’s behavior in bulk and at the nano-scale, at high temperatures and low, combining their own experimental results with 15 decades’ worth of research by colleagues. They also measured the glass transition temperature and the molecular behavior of water that had been doped with other materials, and used this information to set lower and upper boundaries on the transition temperature for pure water. Taken together, their evidence points to a magic number of approximately 136 Kelvin (-137 Celsius). The authors say their work supports traditional views of this phenomenon and refutes recent claims that the transition is above 160 Kelvin (-113 Celsius). The research could find uses in technology associated with food science and the cryopreservation of biological materials, as well as in the study of water in comets and on the surface of planets.
Article: “Resolving the controversy on the glass transition temperature of water?” is published in the Journal of Chemical Physics.
Authors: Simone Capaccioli (1, 2) and K. L. Ngai (1, 3).
(1) CNR-IPCF, Dipartimento di Fisica, Pisa, Italy
The integration of electronics into textiles is a burgeoning field of research that may soon enable smart fabrics and wearable electronics. Bringing this technology one step closer to fruition, Jin-Woo Han and Meyya Meyyappan at the Center for Nanotechnology at NASA Ames Research Center in Moffett Field, Calif., have developed a new flexible memory fabric woven together from interlocking strands of copper and copper-oxide wires. At each juncture, or stitch along the fabric, a nanoscale dab of platinum is placed between the fibers. This “sandwich structure” at each crossing forms a resistive memory circuit. Resistive memory has received much attention due to the simplicity of its design. As described in the AIP’s journal AIP Advances, the copper-oxide fibers serve as the storage medium because they are able to change from an insulator to a conductor simply by applying a voltage. The copper wires and the platinum layers serve as the bottom and top electrodes, respectively. This design easily lends itself to textiles because it naturally forms a crossbar memory structure where the fibers intersect. The researchers developed a reversible, rewritable memory system that was able to retain information for more than 100 days. In this proof-of-concept design, the copper wires were one millimeter thick, though smaller diameter wire would allow for an increase in memory density and a reduction in weight. In practical applications, e-textiles would need to integrate a battery or power generator, sensors, and a computational element, as well as a memory structure. Taken together, an e-textile could potentially detect biomarkers for various diseases, monitor vital signs of the elderly or individuals in hostile environments, and then transmit that information to doctors.
Benzocaine, a commonly used local anesthetic, may more easily wiggle into a cell’s membrane when the membrane is made up of compounds that carry a negative charge, a new study shows. The finding could help scientists piece together a more complete understanding of the molecular-level mechanisms behind pain-blocking medicines, possibly leading to their safer and more effective use. Most scientists believe that local anesthetics prevent pain signals from propagating to the central nervous system by blocking nerve cells’ sodium channels, but exactly how the medicines accomplish this feat remains vague. Since the solubility of anesthetics in the cell membrane can affect the medicine’s potency, some scientists have hypothesized that certain anesthetics may block the action of sodium channels indirectly, by entering the cell membrane and jostling the channels into a new shape that prevents ion flow. With the aim of further investigating such complex processes, scientists from the Universidad Politecnica de Cartagena in Spain and the Universidad Nacional de San Luis in Argentina have created a computer model that calculates the probability of molecules of benzocaine entering a cell’s membrane, based on the composition of the membrane. As reported in the AIP’s Journal of Chemical Physics, the model predicts that membranes made of a large percentage of DPPS, a negatively charged phospholipid component of cells, present less of a barrier to benzocaine molecules than membranes made mostly of DPPC, a neutral phospholipid. DPPS is normally found in humans as a component of the inner side of cell membranes.
Article: “Thermodynamic study of benzocaine insertion into different lipid bilayers” is accepted for publication in the Journal of Chemical Physics.
Authors: J.J. Lopez Cascales (1), S.D. Oliveira Costa (1), and R.D. Porasso (2).
(1) Grupo de Bioinformatica y Macromoleculas (BIOMAC), Universidad Politecnica de Cartagena, Spain
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