Seminars
Upcoming Physics Graduate Student Seminar (2011/2012 Academic Year)
SPRING 2012
Friday, February 3, 2012
Time: 11:00 am
Location: B. H. Snell 177
Speaker: Professor Shannon L. Starr; Department of Mathematics, University of Rochester
Statistical Mechanics of Spin Glasses
Professor Shannon L. Starr
Department of Mathematics
University of Rochester
Spin glasses are a toy model, which also model certain materials, for a special type of ergodicity breaking. They are disordered models of spins where the interactions for each pair of spins are chosen randomly to be ferromagnetic or antiferromagnetic. Their main feature is a high amount of frustration. We will discuss the context and then move on to the main solvable model, the Sherrington-Kirkpatrick model. This was solved by Giorgio Parisi in 1979-80, but recently Parisi's ansatz has been proved completely rigorously. In fact the proof of ultrametricity, the main feature of the model, was proved within the past few months by Dmitry Panchenko by introducing a novel resummation. Time permitting we will explain his recent development.
Friday, February 3, 2012
11:00 a.m.
177 B.H. Snell Hall
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FALL 2011
Friday, September 16, 2011
Time: 11:00 am
Location: B.H. Snell 177
Physics Graduate Student Simon Rock
Simon Rock
Physics Department, Clarkson University
will speak on: Electrochemical Analysis of the “Corrosion” Mechanisms of Chemical Mechanical Planarization
Electrochemical techniques have proven to be practical tools in characterizing thin films in a multitude of systems. For the present study, Tafel analysis, linear polarization resistance measurements and electrochemical impedance spectroscopy are employed to investigate the surface films formed by certain complexing agents used in chemical mechanical planarization (CMP) of Ta barrier lines. Our electrochemical approach will be discussed in detail, and the associated theory will be outlined. It will be shown how electrochemical data-trends can be correlated with similar behaviors of slurry-dependent polish rates. Illustrative data from a recent experiment will be discussed to demonstrate how these electrochemical tests provide useful information about the formation and removal of “polishable” surface films in CMP.
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Upcoming Physics Colloquia (2011/2012 Academic Year)
Friday, September 9, 2011
Time: 11:00 am
Location: B.H. Snell 177
Prof. Vyacheslav N. Gorshkov
Department of Physics & Center for Advanced Materials Processing
Clarkson University
COLLOQUIUM
Prof. Vyacheslav N. Gorshkov, National Technical University of Ukraine
will speak on: Formation of Nanoclusters and Nanopillars in Nonequilibrium
Surface Growth for Catalysis Applications
Abstract
Growth of nanoclusters and nanopillars is considered in a model of surface deposition of building blocks (atoms) diffusionally transported from solution to the forming surface structure. Processes of surface restructuring are also accounted for in the model, which then yields morphologies of interest in catalysis applications. Kinetic Monte Carlo numerical approach is utilized to explore the emergence of FCC‑symmetry surface features in Pt-type metal nanostructures. Available results exemplify evaluation of the fraction of the resulting active sites with desirable properties for catalysis, such as (111)-like coordination, as well as suggest optimal growth regimes.
Biography
Undergraduate: Rostov-on-Don University (Soviet Union), Department of Physics, 1965-1970;
Graduate: Institute of Physics of Ukrainian Academy of Sciences (IP NASU), Kiev 1973-1976;
1976 – Ph. D., Thesis “Some questions of pinch-effect dynamics in plasma of gas discharge and electron-hole plasma of semiconductors”; 1992 – Doctor of Science, Thesis “Nonlinear electro-hydrodynamical phenomena in bounded semiconductors and liquid metals”.
Current Scientific Interests: Electron-Hole Plasma of Semiconductors and Plasma of Gas Discharge; Nonlinear Electro‑Hydrodynamics; Plasma-optics; Physics of Singularities of Optical Beams; Physics of Nanoparticles; Data Mining
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Friday, Sept. 30th, 2011
Time: 11:00 am
Location: B.H. Snell 177
Prof. Dr. A. Morozov
Joint Colloquium with Biology Abstract coming soon....
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Friday, October 7th, 2011
Time: 3:30 pm
Location: B.H. Snell 214
Dr. Judith Klein-Seetharaman
Department of Chemistry and Biomolecular Science and Department of Physics
Clarkson UniversityJoint Colloquium
Prof. Judith Klein-Seetharaman
Department of Structural Biology
University of Pittsburgh School of Medicine
will speak on: Mechanisms of allosteric communication in protein structures
Abstract: Protein structures can be viewed as networks of atoms interacting in three-dimensional space. Allostery is a biochemical term that refers to the ability to achieve action at a distance in an atomic network structure through a small, localized perturbation. This allows proteins to communicate the perturbation signal to distant sites such as other ligand binding sites and protein-protein interaction interfaces. Here, we present current models for the fundamental physical and biological principles underlying allostery. Understanding such principles can be measured by our ability to successfully predict sites of allosteric control and paths of communication connecting such sites, validated by experimental findings. Two case-studies will be presented: (1) allosteric communication across the membrane spanning domains of the pharmacologically important G protein coupled receptors connecting distant ligand binding pockets and (2) modulation of protein-protein interaction interfaces in the HIV-1 capsid protein through ligand binding at distant sites. In both cases, statistical protein sequence analysis was used to reveal pairwise interactions between amino acids. Pairwise correlations imply allosteric interaction if the amino acids are distant in primary sequence as well as three-dimensional structure. Through computational docking, ligand binding sites were predicted, and experimentally validated by a combination of biophysical approaches and studies of biological function such as viral infectivity in the case of the HIV-1 capsid protein and modulation of signaling in the case of G protein coupled receptors. Furthermore, prediction of protein dynamics was used to develop hypotheses on putative mechanisms of allosteric communication. A better understanding of these mechanisms can be useful to improve allosteric drugs and potentially design allosteric proteins, which has diverse application areas such as Biocomputing and extensions of the principle of allostery to other networks.
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Physics Department Colloquium (Past)
Wednesday, August 25, 2010
11 a.m.
B.H. Snell Hall, Room 169
Dr. Roberto Irizarry, DuPont Electronic Technologies, talk title: "On the Dynamics of Metal Particle Formation: Model Development from Plasmonic Kinetic Data and Fast Monte Carlo Solutions"
In the first part of this presentation, a model for metal spherical particle formation is proposed, guided by optical kinetic data of monodisperse metal colloid synthesis. The dynamic optical response of these systems is characterized by broad bands, making their analysis difficult to interpret in terms of particles sizes. To overcome this problem, the data is analyzed in terms a new strategy called simulated dynamic optical response. Using this strategy, it was found that autocatalytic formation of primary particles followed by a zone of very fast aggregation mechanism can describe the dominant dynamics during early stages. In later stages, the dominant mechanism switches to slower aggregation modulated by a stability factor.
In the second part of this presentation, new algorithms for fast Monte Carlo solution of population balance models are presented. In particular, new strategies are proposed for the case where some species are away from the thermodynamic limit (very dilute or finite systems) and other species can be considered deterministic (high concentration). This type of problems often results in a stochastic system that contains both stochastic and continuous variables with timescales spanning orders of magnitude.
Physics Graduate Student Seminar(Past)
Friday, September 3, 2010
11 a.m.
B.H. Snell Hall, Room 177
John Garland Clarkson University, will speak on "Mott-Schottky Analysis of the Temperature Dependent Transition Layer Capacitance of a Si Solar Cell
Standard terrestrial testing (ASTM/ IEC) of photovoltaic (PV) cells requires that the device be characterized at a temperature of 298 oK using 1 Sun (AM 1.5) illumination. Unless this temperature is externally controlled, the cell temperature can significantly vary above this specified value due to photo-thermal effects. Therefore, to adequately analyze the performance of a PV cell, it is necessary to understand how the characteristic parameters of the cell change with temperature variations. The present work focuses on Mott-Schottky analysis of the transition layer capacitance, CT, of a crystalline Si solar cell. This analysis yields information about the acceptor doping in the p-base of the cell's n+-p junction. In addition, understanding the behavior of CT during transient operations of the cell is critical to designing charge regulators for solar panels. CT depends on the bias voltage, V, varying as V-1/2, and has non-explicit temperature dependence. Our experimental results show that the temperature dependence of CT comes through that of the built-in potential, Vbi, of the n+-p junction. This temperature dependence of Vbi represents an important aspect of solar cell performance, because Vbi affects the actual operating voltage of the cell. The results obtained in this work demonstrate how this information can be obtained through rigorous Mott-Schottky analysis of CT under temperature controlled conditions.
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Date: Friday, March 6, 2009
Time: 11 a.m.
Location: B.H. Snell Hall, Room 177
Qiaohui Zhang will speak on "Fabrication of Crosslinked Porous Film in Strain Transducer -- Demonstration of a Plastic-Friendly Process for Flexible Electronics."
Abstract: In the past few decades, flexible (or plastic) electronics have been attracting significant attentions due to potential applications in the foldable solar panel, RFID tag, and electronic newspaper. However, the development is constantly impeded by the lack of appropriate materials and processes. Finding materials that are electrically functional and mechanically robust when flexed is one of the critical issues in this area. In addition, conventional semiconductor processes require high temperature and high-energy plasma, which tend to deform or blur the plastic substrates. This presentation demonstrates a new low-temperature process which appears to be promising to the fabrication of flexible electronics, and is applicable to plastic substrate and many other delicate electronic materials. In particular, as a proof-of-concept, a flexion sensor fabricated by this process is illustrated. Such sensor involves a porous dielectric layer (nanospring) which contributes to the sensitivity to the strain. It is also shown that the porous film can be thermally crosslinked to obtain a satisfactory cyclic response. The crosslinked porous film acts as an “artificial rubber” at nanoscale. Both simulation and experimental data show that the bending of the sample results in the deformation of the porous film and increasing of the current. It is hypothesized that the electric conduction is a combination of tunneling and ionic currents through the thin polymeric film. Compare to the commercial products, the transducer consumes zero power in idle situation and makes pixel sensing possible.
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Date: Friday, February 27, 2009
Time: 11 a.m.
Location: B.H. Snell Hall, Room 177
Ionel Halaciuga will speak on "Coated Polymer Particles for Electronic Packaging."
Abstract: Miniaturization and robustness are key factors in today’s electronics industry when considering manufacturing new devices. Anisotropic conductive adhesives (ACA) that conduct electricity along only one direction are widely used to provide electrical connection in electronic packages. Using such adhesives instead of soldering and other traditional methods provides for a more efficient use of the boards and for more flexible and reliable connections. Typically, the ACA consists of electrically conductive particles and an insulating binder. Using polymer spheres coated with a metal film as electrically conductive particles provides a lower cost and a higher bonding area between components due to the elasticity of the polymer particles. The metal film consists in general of an inner layer of nickel and an outer layer of gold. Nickel is used to improve connection between gold and the polymer particles’ surface, and gold is used for its high electrical conductivity and corrosion resistance. Experimentally, the ultimate goal of this research is to prepare well dispersed metal coated polymer particles of various sizes having a relatively smooth surface to satisfy the demands of the current electronic materials market. A novel method was developed to coat polymer spheres with metal film and the parameters that influence the plating were studied. We found that by varying certain experimental parameters the coating can be improved and applied successfully to different size polymer spheres with various surface functionalities.***********************************************************************
Date: Friday, February 20, 2009
Time: 11 a.m.
Location: B.H. Snell Hall, Room 177
Irina Dokukina will speak on "Fibroblast Motility on Substrates with Different Rigidities."
Abstract: Cell motility is extremely important for many aspects of life from embryonic development and immunity response to wound healing and diseases. It is not fully understood how cells coordinate overall motility, but it is well known that cell ability to sense environment is crucial to cell functioning. Mechanosensitivity of cell to extracellular matrix is one of many mechanisms that direct cell behavior. It was identified experimentally that given a choice between 'soft' and 'stiff' substrates, a cell prefers to crawl over 'stiff' substrate, turning away from the boundary that separates two substrates. We develop a discrete model for cell locomotion on substrates with different rigidities. The model allows us to understand the relationship between cell-substrate sensing and cell internal function. Our model exhibits experimentally observed cell rigidity sensing and allows us to make additional insights into cell mechanosensitivity. We consider only the role of cell mechanics in cell-substrate rigidity sensing, however, it is also sharpened by the chemical signaling inside the cell.
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Date: Friday, January 30, 2009
Time: 11 a.m.
Location: B.H. Snell Hall, Room 177
Alexey Nikolaev will speak on "Simple Model for Controlled DNA Translocation through a Nanopore."
Abstract: The goal of this research is to study the effect of the layered semiconductor membrane on DNA translocation through a nanopore. Previously calculated electrostatic potentials of thin electrically tunable membranes composed of two layers of n-type and p-type semiconductor materials are used to study distinct electrostatic potential landscapes. The membrane-DNA system is immersed in an electrolyte solution under bias to induce DNA translocation. A simple charges-and-springs model is used to model the DNA molecule. We compare electrostatic potential landscapes in the nanopore with one and more potential extrema and show how the landscape can be used to alter the dynamics of the molecule translocation. In particular, we specify different conditions under which DNA nucleotides can translocate through the nanopore in one by one fashion in both directions as well as be paused in the nanopore.
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Date: Friday, January 23, 2009
Time: 11 a.m.
Location: B.H. Snell Hall, Room 177
Oleksandr Gromenko will speak on "Random Sequential Adsorption: Modern Status"
Abstract: Random sequential adsorption (RSA) model has attracted a lot of attention and has a long history. Applications can be found in many fields, ranging from surface science to polymers, biology, device physics, and physical chemistry. Traditionally, the RSA model assumed that particles are transported to a substrate, which is a continuous surface or a lattice. Modern status and recent theoretical development in the RSA will be discussed.
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Date: Friday, January 9, 2009
Time: 11 a.m.
Location: B.H. Snell Hall, Room 177
Igor Sevonkaev will speak on "Investigation of NaMgF3 and MgF2 Nanoparticle Growth on Short Time Scales"
Abstract: Over the past several decades a large number of dispersions, consisting of uniform particles of simple and composite nature, have been reported in the literature. In principle, the most versatile method to produce such dispersions is by precipitation in solutions. The latter process may involve different mechanisms of formation, such as polymerization of solutes in liquid media, diffusional growth following the nucleation stage, or aggregation of preformed nanosize precursors. In this study we investigated initial stages of particles growth prepared by precipitation. Specifically, the stopped-flow and continued-flow methods were developed for observations of particle synthesis kinetics at short time scales. We also utilized TEM and laser diffraction techniques to obtain broader characterization details. Our results yield novel data for theoretical models, in the regime of behavior not probed by earlier experiments.
