Focus Topic Descriptions, 11.8.1 - 12.7.6
See also Focus Topic Descriptions 02.8.2 - 07.11.6 and Focus Topic Descriptions 13.6.1 - 23.12.6.
| 11.8.1 | DCP | Structure and Dynamics of Interfacial Water The goal of the symposium would be to bring together experimentalists and theoreticians from different communities (physics, chemistry, and biology), who study the properties of interfacial water as it relates to its interaction with electrons in different environments (cluster, surface, protein), in order to advance the knowledge on how the environment affects the local structure of water, and in turn, the dynamics of electron transfer, solvation, conduction, etc. that is vitally important in fields such as photosynthesis, respiration, photocatalysis, corrosion, atmospheric chemistry, and others. Organizers: | |
| 11.8.2 | DCP | Ion Channel Physics and Chemical Physics The past decade has seen tremendous strides in our understanding of the structure and function of protein channels that embed in lipid bilayers to allow the passage of ions – a key component in many critical physiological functions, including energy and signal transduction. The determination of the crystal structures of several ion channels, as well as advances in cryo-microscopy, NMR and other spectroscopic techniques, have provided insights into mechanisms of their motions and function, including ion permeation kinetics and channel gating in response to channel-specific stimuli. In this Focus Topic session, recent progress in both experimental and theoretical/computational aspects of ion channel science will be explored from a condensed matter physics perspective, including molecular and coarse-grained microscopic and mesoscopic models of ion channel structure-function relations, and experimental measurements made via state-of-the-art spectroscopic probes (ESR, NMR, FRET, etc.). Ion channel based applications to biotechnology, e.g., single-molecule sensing and fuel cell design, will also be featured. Organizer: | |
| 11.8.3 | same as 17.13.4 | DCP/ DCOMP | Fundamental Developments in Density Functional Theory This session will focus on recent developments in the field of Density Functional Theory (DFT), emphasizing new directions in both ground-stateand time-dependent formulations. DFT has been enormously successful in describing quantitatively a widerange of ground-state properties of atoms, molecules, clusters, and extended systems. Its time-dependent analog, TDDFT, is now routinely used in order to extract electronic excited state energies of matter at all levels of aggregation. Not withstanding this success which underscores the popularity that DFT and TDDFT are enjoying in quantum chemistry and materials science, several limitations of existing approximations to the density functionals have been identified. Understanding and overcoming such limitations remains a major challenge of contemporary chemical physics. Examples include the correct treatment of dispersion (Van-der-Waals) forces, the accurate description of strongly-correlated electron systems, and the efficient treatment of electron dynamics in the presence of strong fields. Coinciding with the 45th anniversary of the Hohenberg-Kohn theorem thatlaid the foundation for DFT, and also with the 25th anniversary of the Runge-Gross theorem that put TDDFT on firm footing, the present focus session will cover a range of new frontiers, with the specific aim of discussing those regimes where existing approximations to the density functionals are insufficiently accurate to describe the phenomena of interest. Organizer: |
| 11.8.4 | DCP | The Transition State in Physics, Chemistry, and Astrophysics The proper departure point for a discussion of the Transition State are the proceedings of the lively 67th General Discussion of the Faraday Society. In his admirable summary of this Discussion, given during the Spiers Memorial Lecture of the 110th Faraday Discussion of 1998, W. H. Miller recounts how two distinct points of view emerged on rates of chemical reaction from the discussions of the 67th meeting: Eyring's thermodynamic picture and Wigner's dynamical perspective, which, in the decades between the 1930's and 1970's was buried by the enormous numbers of applications of the thermodynamic picture. In his perceptive paper, Wigner gave a clear outline of the subject in terms of his "Three Threes." First there were the three steps in the theory of kinetics: (1) Constructing the potential energy surface, (2) calculatingthe rates of elementary reactions, and (3) combining many elementary reactions into a complex reaction mechanism. Next came the three groups of elementary reactions, and finally, were the three assumptions of Transition State Theory (TST): (1) No electronically non-adiabatic transitions (2) validity of classical mechanics for the nuclear motion, and (3) the existence of a dividing surface, separating the reactants and products, that no classical trajectory passes through more than once. Wigner noted that the failure of the last assumption will lead, in general, to values of the reaction rate that are too large. Wigner's formulation quickly leads to the recognition that the Transition State (TS) is actually a general property of all dynamical systems, provided that they evolve from "reactants" to "products." The TS, therefore, is not confined to chemical reaction dynamics, but it also controls rates in a multitude of interesting systems, including, e.g., the rearrangements of clusters, the ionization of atoms, conductance due to ballistic electron transport through microjunctions, diffusion jumps in solids, and statistical rates of asteroid capture. The papers in this session will discuss the reemergence of Wigner's dynamical approach to TST. Organizer: | |
| 11.8.5 | DCP | Theory of Electron Transport Through Molecular Wires Recent years have seen a rapid proliferation of experimental probes of electron transport on the single molecule scale. These experiments pose significant fundamental challenges to theory: How can we connect the familiar tools of electronic structure to model this new field of "transport spectroscopy"? How can we incorporate the effects of dissipation and dephasing on the current? Under what conditions do vibronic interactions influence the current? This symposium will address the cutting edge theoretical developments that are helping us answer these fundamental questions. Organizer: | |
| 11.8.6 | DCP | Evolution from the Prism of Physics "Nothing in Biology makes sense except in the Light of Evolution." This famous maxim by Theodosius Dobzhansky is more relevant today than ever. While understanding how function and form evolve in Biology had been an intellectual quest for the last two centuries, it is only now that definitive answers are beginning to emerge, largely due to the avalanche of data on sequences, structure and function of genes in multiple organisms. Evolution of form and its relation to function has been the subject of fascination and active study in Biology since its inception. Early efforts, dating back to pre-gene era evolved into powerful mathematical approaches known as classical population genetics. Guided by Darwinian principles and inspired by early genetics experiments dating back to Mendel, theorists developed an approach whose cornerstone is a concept of fitness often defined as a degree of reproductive success of an organism. Classical population genetics apriori assigns fitness to alleles without considering physical, molecular mechanisms that give rise to structure and function of their products – proteins. On the other hand Molecular Biophysics progressed to the point that many aspects of protein folding and function are understood on a fundamental level. In particular Protein Folding Theory has outlined conditions on protein sequences to form stable and fast-folding proteins and provided estimates of how many such sequences exist. Several studies provided deep insights into biophysical aspects of protein function, including enzymatic catalysis, motor function, transport and simple networks such as chemotaxis and response regulators. In some cases relationship between structure and function has been understood in full microscopic detail and experimental approaches to rationally modify (improve) protein function have been developed. These important developments notwithstanding, there remains a significant gap between macroscopic analysis of biological evolution that describe organisms and populations under Darwinian pressure and microscopic description of life at the level of proteins that are microscopically detailed but agnostic of how these properties came about in the process of natural selection. On a larger scale of analysis of multitudes of genes and proteins we have observed highly non-trivial, fractal rules of their organization that could be testament to certain dynamic processes of evolution of the Protein Universe or probably some intrinsic structural or functional preferences for some types of proteins to evolve faster or more efficiently than others. While strictly preliminary, some of the questions that this Session may address productively and with great success are:
We expect that methods and tools of Chemical Physics will be instrumental for success in meeting these challenges. To this end we expect to attract a significant number of participants with background in Chemical Physics as well as Theoretical Physicists and Biophysicists and fully anticipate that they will find the topics of the Workshop both challenging and intellectually stimulating. Organizers: | |
| 11.8.7 | DCP | Excitonic Energy Transfer in Artificial and Natural Light Harvesting System Every day, 5x1021 J of energy from the sun reaches the Earth’s surface. By 2040, anthropogenic energy consumption will have doubled requiring 2x1018 J of energy for daily use. Therefore, given the abundance of untapped energy, scalable, economical solar energy harvesting is an attractive alternative energy source. The vast majority of the energy available to living organisms in the food chain emanates from photosynthesis. The mechanisms that photosynthetic organisms employ for light energy harvesting differ from those of solid-state inorganic devices both in their organization and in the degree of excitonic localization. Electronic excitations in solid state inorganic devices are delocalized and separated charge carriers are transported long distances; therefore these materials require a high degree of order. In contrast, natural light-harvesting antennas are organized at smaller length scales and employ more localized excitons; these excitons are then transported prior to charge separation. For the development of artificial light-harvesting devices, a fundamental understanding of the excitonic transport process is crucial for the development of novel nanostructured and organic photovoltaic materials. In this symposium, we seek to identify design principles of natural light harvesting systems and lay the foundation for the next generation of artificial light harvesting devices. Topics such as the role of coherence in excitonic energy transfer, excitonic diffusion, charge separation, and carrier recombination in both artificial and natural light-harvesting systems will be discussed. Organizers: Gregory Engel | |
| 11.8.8 | DCP | Nanomaterials for Energy Applications The development of new methods to harvest, store, and generate energy is one of the most important global scientific challenges. Nanomaterials research has made a big impact in this area, and nanomaterials have led to the emergence of improved solar cells, hydrogen-storage devices, and powerful batteries and fuel cells. This symposium aims to unite chemists and physicists for a discussion of the current problems, goals, challenges, and opportunities facing researchers in each of these areas. It will consist of three sections; one concerning the fabrication and physical characterization of nanomaterial-based photovoltaic devices, another focusing on the synthesis and gas-sorption properties of new designer nanoporous materials, and a third detailing the use of nanomaterials in battery and fuel cell power generation. Each session will be comprised of speakers whose expertise ranges from synthesis and fabrication to physical characterization and theoretical modeling. Organizers: Alex Star | |
| 11.8.9 | DCP | Spectroscopic Probes of Biomolecular Structure and Function The function of a biological molecule is intimately related to its structure and dynamics. Exciting developments in spectroscopy over the last decade have enabled measurements of these properties of peptides and proteins, nucleic acid base pairs and their complexes, and sugars, lipids, and carbohydrates for the first time. This symposium will highlight these developments. We propose three sessions. The first session will focus on ESR, microwave and NMR methods to measure the structures of membranes and aggregated proteins. The second session will feature new methods like THz, 2D-IR and Raman spectroscopy to measure folding patterns and dynamics of biomolecules in aqueous solution. The last session will focus on (both frequency and time resolved) laser-based and X-ray measurements of the motions of large biomolecules in real time, both in the gas and condensed phase. Organizers: David Pratt | |
| 12.7.1 | GSNP | Structure and Dynamics of Complex Networks Networks shape our lives, from cell regulation and food webs to transportation infrastructure and social communities. The characterization and understanding of the commonalities and differences of various networks is an inherently interdisciplinary endeavor in which physicists are playing a major role. The topological structures of different kinds of networks, and their implications for network stability to external perturbations, have been studied for some time; dynamical properties of network growth, rewiring, adaptivity, and optimization have recently attracted increased interest, especially if it involves interactions between the degrees of freedom associated with nodes and those associated with links. This session will attract researchers interested in the interplay of topological and dynamical properties of networks, from a fundamental to an applied perspective. The proposed invited speaker is a leader in the field and has made many fundamental and intriguing contributions over the past five years, from an understanding of gradient networks to the resolution of certain queuing problems. Organizer: | |
| 12.7.2 | GSNP | Jamming: Theory and Experiment A jammed material is defined as one that is structurally disordered but, unlike a fluid, possesses a yield stress. Understanding jamming is important from a technological, environmental, and basic science perspective. Jamming of grains in silos causes catastrophic failures. Avalanches are examples of unjamming, which we need to understand to prevent and control. The phenomenon of jamming poses fundamental challenges in basic science because there is no known framework leading from the microscopic interactions to the macroscopic properties that reflect collective behavior. Experiments point to many similarities between the jamming transitions in granular materials, driven foams, emulsions and gels. Phenomena such as shear banding in granular materials, has interesting analogs in the plastic failure of amorphous solids, in foams and in colloids. We are proposing two speakers for this session who have made recent novel contributions in theory and experiment, respectively. More generally, we solicit abstracts for new results from experimental, numerical, and analytical approaches, which address the similarities and differences between the jamming transition and seek a unifying framework. Organizers: Bulbul Chakraborty | |
| 12.7.3 | GSNP/ DBP | Stochastic Processes in Biological Systems Recent research, both theoretical and experimental, has led to an increased focus on analyzing stochastic phenomena in biological systems. For example, biochemical reactions occurring in the fundamental unit of life, the cell, typically involve small numbers of molecular species and are thus intrinsically stochastic processes. Cellular systems are thus constrained by the necessity to maintain function in the presence of large fluctuations, and in some cases, can even exploit the intrinsic noise. Both theoretical and experimental efforts to understand biological systems have uncovered several examples wherein a stochastic analysis yields qualitatively different results from the corresponding deterministic analysis. This Focus session proposes to bring together different scientists working on stochastic modeling approaches to understanding diverse biological systems with the aim of highlighting both commonalities and differences and identifying new directions to guide future research. Organizers: Uwe C. Täuber | |
| 12.7.4 | same as 10.14.22 | GSNP/ DBP | Noisy Reaction-Diffusion Systems In many instances, especially in low-dimensional systems, diffusion-limited reactions are not adequately mathematically described by mean-field rate equations. Instead, intrinsic noise, fluctuations, and emerging correlations lead to very rich and complex behavior. The resulting intriguing properties have attracted scientists from a variety of disciplines, from materials science to biology and ecology. This Focus Session proposes to bring together these scientists and to provide them with a forum where they can present their research and discuss the state of the field as well as the new directions that have emerged in recent years. Organizers: Michel Pleimling
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| 12.7.5 | GSNP | Dynamics of Glassy Systems Whereas a fluid's correlation length diverges at crystallization, no such diverging length scale appears to accompany the glass transition. Not only does the structure of a glass resemble that of a fluid, conventional measurements of the velocity-velocity correlation function show only modest increases at the same time that the viscosity increases by many orders of magnitude. New light has been cast on this puzzle by the recent classification and enumeration of soft vibrational modes in glass-forming systems. This theoretical framework quantitatively explains the measured thermodynamic properties, including the so-called "boson peak," in such disparate systems as colloidal glasses and silica networks. As such, it may provide the basis for a complete theory of the glass transition. This session invites abstracts on these recent findings of soft modes at the glass transition and other aspects of the dynamics of glasses. Organizer: | |
| 12.7.6 | GSNP | Elasticity and Geometry of Thin Objects Over the past few years, the physics community has taken the field of elasticity, usually in the realm of the more applied engineering sciences, into a new fundamental direction. In particular, the elasticity of thin rods, sheets or shells can be very rich but highly nontrivial. During the deformation process of a thin object, even if its material properties may remain perfectly linear, large displacements can give rise to non-negligible geometric nonlinearities. Mathematical tools from differential geometry, together with a hybrid of continuum and statistical mechanics are often involved in their study. One of the first problems regarded in this spirit was the description crumpled sheets and its singularities. There is also a great potential for coupling the elasticity of thin objects with other phenomena: fluid flow, surface tension, fracture and adhesion, to name but a few. Moreover, in some instances of morphogenesis of living matter, it is thought that mechanical stresses may have a significant role through the coupling of elasticity of the animal or plant tissue to its growth. Earlier this year, in New Orleans, we organized the first focus session, at an APS March meeting, covering this topic . The feedback from both speakers and audience was extremely positive and attendance was well above expectations. This points to a solid growing community of study of elasticity of thin objects seen from a physics perspective. Repeating the experience at the March Meeting 2009 would allow for continuity and strengthening of this APS channel in which to present, share and discuss the latest advancements in this emerging field. Organizer: |
