News from Statistical Physics & Dynamical Systems
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The latest news from Statistical Physics & Dynamical SystemsThu, 23 Nov 2017 17:14:24 GMT2017-11-23T17:14:24ZSpringer Statistical Physics & Dynamical Systemshttp://images.springer.com/cda/content/designimage/cda_displaydesignimage.gif?SGWID=0-0-17-901483-0
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Gap geometry grasped
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A new algorithm could help understand the structure of liquids, and how they flow through porous media <br /><img align="right" src="https://images.springer.com/cda/content/image/cda_displayimage.jpg?SGWID=0-0-16-1682938-0" /><div>Theoretical physicist Moumita Maiti and colleagues at the Jawaharlal Nehru Centre for Advanced Scientific Research in Bangalore, India, have now implemented an algorithm for analysing void space in sphere packing, where the spheres need not all be the same size. This <a href="http://link.springer.com/article/10.1140/epje/i2013-13005-4">method</a>, about to be published in <a href="journal:10189">EPJ E</a>, could be applied to analyse the geometry of liquids present between multi-sized spheres that are akin to a model for porous material. This provides a tool for studying the flow of such fluids through porous material. More importantly, it can also be used to study the packing geometry of proteins.<br /><br />There have been several previous attempts to calculate the volume and the surface area of packing of spheres. But few methods have taken into account the connectivity of empty space between spheres, which matters, for example, when detecting buried cavities in proteins.<br /><br />To remedy this issue, the authors have relied on a programme capable of performing a very detailed study of the size distribution of the free volumes of individual spheres—that is, the volume swept by the centre of the sphere without overlapping with any of the other spheres—in jammed sphere packing. It also makes it possible to calculate the exact volumes and surface areas of cavities by detecting the disconnected components of cavities. <br /><br />The team applied this method to the analysis of protein structures. This led them to compute various key quantities such as the distribution of sizes of buried cavities and pockets between spheres, the matching of areas accessible to solvent in which protein are found with the corresponding volumes and the composition of residues lining cavities. <br /><br />Ultimately, the authors are planning to prepare this algorithm for distribution as open source software.<br /><br /><br /><strong>Reference:</strong><br />M. Maiti, A. Laxminarayanan and S. Sastry (2013), Characterization of Void Space in Polydisperse Sphere Packings: Applications to hard sphere packings and to protein structure analysis, <em>European Physical Journal E</em>, DOI 10.1140/epje/i2013-13005-4<br /><br /><strong>The full-text article is available to journalists on request.</strong></div><br /><h2>Further Information:</h2><a href="http://www.epj.org">European Physical Journal</a><br /><br /><h2>Contact:</h2><div>Ann Koebler, tel. +49 6221 4878414, ann.koebler@springer.com</div><br />New York | HeidelbergThu, 31 Jan 2013 23:00:00 GMThttp://www.springer.com/about+springer/media/springer+select?SGWID=0-11001-6-1404644-02013-01-31T23:00:00ZLiquid crystal’s chaotic inner dynamics
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Scientists have unearthed a new dynamic process induced by strong electric fields in thin liquid crystal cells <br /><img align="right" src="https://images.springer.com/cda/content/image/cda_displayimage.jpg?SGWID=0-0-16-1676530-0" /><div>Liquid crystal displays are ubiquitous. Now, Polish physicists have demonstrated that the application of a very strong alternating electric field to thin liquid crystal cells leads to a new distinct dynamic effect in the response of the cells. The <a href="http://link.springer.com/article/10.1140/epje/i2013-13002-7">theory</a> of spatio-temporal chaos explains this effect. It was elucidated by Wojciech Jeżewski and colleagues from the Institute of Molecular Physics, Polish Academy of Sciences, in Poznań, Poland, and is about to be published in <a href="journal:10189">EPJ E</a>. This effect has implications for the operation of liquid-crystal devices because their operation is based on the electro-optic switching phenomenon, subject to the newly discovered effect.<br /><br />The authors first applied an alternating electric field to semi-transparent, conducting plates of cells containing a liquid crystal substance. Such systems are characterised by a spontaneous electric polarisation that can be reversed by the application of an external electric field. <br /><br />The Jeżewski team then registered the resulting molecular reorientations by recording changes in the intensity of light transmitted by the liquid crystal sample, or spectra. In particular, the authors experimentally identified a distinct high-frequency band in the response, reflecting the activation of a specific dynamic process inside the sample.<br /><br />Theoretical studies of the complex molecular reorientation dynamics confirmed experimental observations. The team explained the response of the sample by numerically solving the equation describing the motion of molecules subjected to very strong alternating fields. Unlike previous approaches, these simulations did not make any assumption about the sample dynamics. <br /><br />The effect they showed was associated with a chaotic molecular reorientation induced by a strong field of sufficiently high frequency. Furthermore, a unique experimental setup led to signals, due to strong excitations of liquid crystals at frequencies less than the frequency of the external electric field, being registered. <br /><br /><br /><strong>Reference:</strong><br />W. Jeżewski, I. Śliwa, and W. Kuczyński (2013), Strongly nonlinear dynamics of ferroelectric liquid crystals, <em>European Physical Journal E</em>, DOI 10.1140/epje/i2013-13002-7<br /><br /><strong>The full-text article is available to journalists on request.</strong></div><br /><h2>Further Information:</h2><a href="http://www.epj.org">European Physical Journal</a><br /><br /><h2>Contact:</h2><div>Ann Koebler, tel. +49 6221 4878414, ann.koebler@springer.com</div><br />New York | HeidelbergWed, 23 Jan 2013 23:00:00 GMThttp://www.springer.com/about+springer/media/springer+select?SGWID=0-11001-6-1403243-02013-01-23T23:00:00ZStatistical Physics & Dynamical Systems
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