Past Seminars
Friday, December 8, 2006, 11:00 a.m., B. H. Snell Hall, Room 177
Phase transitions, clusters, and geometry from spectral analysis
Prof. Lawrence Schulman, Physics Department, Clarkson University
A central object in stochastic dynamics is the matrix of transition probabilities. Spectral properties of this matrix encode a great deal of information about a system's behavior. I will show how this code can reveal the presence of phase transitions, how it can be used to provide a natural metric on the space (from which clusters and network properties can be obtained) and how, without reference to outside information, it can reveal the geometry of an underlying space on which a stochastic process is defined.
Monday, December 4, 2006, 9:30 a.m., Barben A in Cheel
Recent developments on field-effect-based chemical and biological sensors
Prof. Dr. Michael J. Schöning, University of Applied Sciences Aachen (Juelich Campus), Laboratory for Chemical Sensors and Biosensors and Research Centre Juelich, Institute of Bio- and Nanosystems (IBN-II)
The rapid development of semiconductor-based micro- and nano-technologies has stimulated the creation of new sensor concepts that combine both chemical and biological recognition processes together with silicon chip manufacturing technologies. Typical examples are array-based set-ups such as “lab on a chip” devices, µTAS (micro total analysis systems) or electronic tongues. In spite of these high-sophisticated multi-parameter sensor systems, the chemical sensors or biosensors as part of these set-ups, play a key role with regard to their analytical behaviour. Among the multitude of concepts and different types of chemical sensors and biosensors, discussed in literature, the strategy to integrate chemical or biological recognition elements together with semiconductor-type field-effect devices, is one of the most attractive approaches. In this context, typical examples are represented by the capacitive EIS (electrolyte-insulator- semiconductor) sensor, the LAPS (light-addressable potentiometric sensor) and the ISFET (ion-sensitive field-effect transistor). These three kinds of devices are currently being the basic structural element in a new generation of chemical and biological microsensors, fabricated by means of silicon planar technology. Moreover, these devices provide a lot of potential advantages over conventional approaches such as the small size and weight, the fast response time, the possibility of an on-chip integration of sensor arrays, the high robustness, the possibility of low-cost fabrication, etc. This talk gives an overview on different examples of silicon-based field-effect (bio-)chemical sensors that have been developed in our laboratory: thin dielectric materials in the nm-scale for ion-selective sensing, strategies to immobilise different enzymes and biomolecules onto field-effect structures for specific analytical purposes, three-dimensionally structured porous Si field-effect devices for improved chemical sensor and biosensor applications towards miniaturised micro-analysis systems, a “high order” hybrid FET module for the simultaneous (bio-)chemical and physical sensing of up to eight different parameters, and the development of biohybrid sensors by immobilising intact chemoreceptors. In addition, the possibility to realise miniaturised field-effect structures in the nm-scale by using conventional photolithography together with a layer-expansion technique, and challenging label-free DNA sensors by field-effect devices will be presented.
Friday, December 1, 2006, 11:00 a.m., B. H. Snell Hall, Room 177
Mechanisms of the Formation of Uniform Particles with Well-Defined Size and Shape
Igor Sevonkaev, Physics Department, Clarkson University
In current project, we proposed a combinational mechanism of the shape control particle growth as a computational approach, and analyzed the mechanism of formation of neighborite cubic particles, at the experimental part. In the numerical simulation part, we assumed that the aggregation consists of two main processes: deposition and rearrangement. Numerical simulation analysis was used as a tool for studying the parameters of the shape maintained growth of the initial particles. In our model the Gaussian Distribution Function (GDF) was proposed as the main deposition rule for the arriving building blocks. And Uniform Distribution Function (UDF) was suggested as the main mechanism for their rearrangement. In the experimental part we studied the parameters that influence the formation of neighborite (NaMgF3) particles. We found some physical and chemical quantities that are responsible for shape and size control in our system. Also a series of experiments was assigned which provides strong evidences for the formation of neighborite cubic particles from ions in solution as a two stage process. During the first stage, primary crystal units of MgF2 are formed, which are then transformed, in the second stage, into primary subunits of NaMgF3. The primary subunits of NaMgF3 grow and aggregate into the fine product of polycrystalline neighborite particles with cubic shape.
Friday, November 17, 2006, 11:00 a.m., B. H. Snell Hall, Room 177
Uniform metallic nanoparticles: Preparation, mechanism of formation, and applications
Prof. Dan V. Goia, Center for Advanced Materials Processing, Clarkson University
The significant importance of metallic nanoparticles in many well-established technological fields such as electronics, catalysis, pigments, as well as in a myriad of new applications in medicine, biology, optics, photonics, and magnetic storage is nowadays widely recognized. As they continuously evolve, these applications are increasingly relying on uniform particles with well-controlled size, size distribution, morphology, composition, internal structure, and surface characteristics. Consequently, there has been a significant amount of research lately focused on the development of preparation methods capable of generating materials with the stringent properties imposed by such specific needs. Among many other possible synthetic routes, the chemical precipitation in solutions stands out as one of the oldest, simplest and, at the same time, most versatile methods for preparing highly dispersed metals. The presentation will review briefly the basic concepts behind this approach and will illustrate its ability to tailor the properties of the metallic particles through a proper design and manipulation of the experimental conditions. The mechanisms involved in the formation of uniform metal colloids in homogeneous solutions and their implications for the design and practical implementation of the precipitation processes will be discussed in detail. In this context, a new mechanism for the nucleation of the metal phase will be proposed. It will be shown that, in the particular case of metals, the conventional theory of nucleation in homogeneous solutions needs to be revised to account for a transition that needs to occur in order to convert the 'amorphous' entities, formed early during the rapid build up of the metal atoms, into stable nuclei that display the crystalline structure of the bulk metal.
Friday, November 3, 2006, 11:00 a.m., B. H. Snell Hall, Room 177
Analysis of Current Transients for Pulse Modulated Electrochemical Mechanical Planarization (ECMP) of Cu and Observation of Current Oscillations in Voltemetric ECMP of Ta
Chris Sulyma, Physics Department, Clarkson University
The voltage pulse modulation technique is useful for controlling electrochemical removal of surface layers in abrasive-free ECMP of Cu. In this approach, surface reactions can be maintained in the kinetically controlled regime (avoiding pattern-sensitive effects of mass transfer reactions), and at the same time the resulting current transient can be analyzed to probe signature features of competitive or combined surface reactions. The present work focuses on the latter (analytical) aspect of pulse modulated Cu-ECMP using an abrasive-free solution of Oxalic Acid and H2O2 in the absence of mechanical polishing. In addition to the work on Cu, there was cyclic voltammetry data obtained pertaining to ECMP of an electrochemical Ta interface. The system studied was a Ta coupon in an electrolyte of KNO3. Induced current oscillations were observed, in the latter case, when the external voltage applied exceeded a threshold value.
Friday, October 27, 2006, 11:00 a.m., B. H. Snell Hall, Room 177
Two-Dimensional Crystal Growth From Undersaturated Solutions
Dr. Srinivas Manne, Department of Physics, University of Arizona, Tucson
The solubility of a substance is commonly understood as the minimum concentration necessary for the condensation of a solid phase from solution. Here we report the nucleation and growth of ionic compounds from aqueous concentrations of order 0.1 times the solubility. The condensation is catalyzed by a foreign substrate, and the new phase grows as a crystalline monolayer. Undersaturated growth is observed only in cases where the dissolved compound is isomorphic with the substrate and the interaction strength between a dissolved-ion/substrate-ion pair exceeds that between the two dissolved ions. These results are consistent with a simple model in which favorable ion-surface interactions lead to ion enrichment and supersaturation in the 2D interfacial zone. The detection of 2D gas and liquid-crystalline phases usually requires extending atomic force microscopy (AFM) to include the mapping of lateral or “soft contact” forces.
Wednesday, October 11, 2006, 4:00 p.m., Science Center 354
Controlled Interactions, Quantum Noise and Entanglement in Systems for Quantum Information Processing
Dmitry Solenov, Clarkson University
The development of quantum computing requires the use of many interesting techniques to deal with noise-induced errors in quantum algorithms. All of these techniques rely on keeping the noise introduced due to the inevitable interactions of a quantum computing system with its environment below a certain threshold level. We study the development of non-coherent processes for different realizations of quantum bits (qubits), as well as qubit-gate systems. We also analyze of coherence vs. noise effects in two-qubit systems subject to a common environment, using the example of a two spin system in a bosonic heat bath. We identify the time scales for which the spins develop entanglement for various spatial separations. For more complex quantum systems, it turns out that some decoherence can actually be beneficial, e.g., in quantum walks on cycles (and hyper-cycles). We investigate this effect in a realistic physical model of the graph, on which the quantum walk occur, where decoherence is induced by continuous monitoring of each graph vertex (quantum dot) with a nearby quantum point contact. We derive an analytical expression for the probability distribution along the cycle and calculate bounds for the mixing time. We also demonstrate that in larger qubit systems entanglement can be viewed as an order parameter. Multi-qubit systems interacting with a common bosonic field (Dicke model) experience a quantum phase transition as one alters the coupling strength. Such systems are generally not integrable (without the rotating-wave assumption). We derive an exact solution in the limit of a large number of atoms, where the integrability is restored. Critical exponents are calculated.
Monday, October 9, 2006, 11:00 a.m., B. H. Snell Hall, Room 129
Equilibration of a Dissipative Quantum Oscillator
Prof. Vinay Ambegaokar, Cornell University
A straightforward and explicit demonstration will be given of a harmonic oscillator being driven to the equilibrium of a corresponding interacting system by coupling it to a harmonic thermal bath. This will be done using elementary quantum statistics, and also via a two-time quantum kinetic equation. The latter method will be advocated for dealing with time dependent dissipative problems.
Friday, October 6, 2006, 11:00 a.m., B. H. Snell Hall, Room 129
Quantum-Dot Computing and Decoherence
Dr. L. Fedichkin, Center for Quantum Device Technology, Department of Physics, Clarkson University
We consider the use of quantum bits (qubits)—semiconductor quantum dots containing one electron and each consisting of two tunnel-connected parts—as basic elements of the quantum computer. Qubit interacting with its environment is continuously monitored by a detector represented by a quantum point contact. The dynamics of electron tunneling in a system of coupled quantum dots are considered in the presence of decoherence. We demonstrate that in these structures the realization of a full set of basic logic operations, which are necessary for fulfillment of quantum computations, is possible. Analysis of decoherence rates due to interaction with phonons shows the proposed qubit to be coherent enough to work continuously. As the level of quantum noise and the resulting decoherence increase, we observe a crossover from a quantum-coherent oscillatory dynamics to a diffusive classical motion.
Friday, September 29, 2006, 11:00 a.m., B. H. Snell Hall, Room 177
Coherent control as springboard for quantum gate operations
Dr. Vladimir S. Malinovsky, MagiQ Technologies, Inc., New York
One of the DiVincenzo requirements for quantum computer is selective addressing of single qubits in a quantum register. Here we present some new results related to fast single-qubit gates and discuss interplay between individual addressing of qubits, ultrafast spectroscopy and coherent control.
Friday, September 22, 2006, 11:00 a.m., B. H. Snell Hall, Room 177
Evolution on a Chip
Dr. Robert H. Austin, Department of Physics, Princeton University
Is Darwin right? That's an explosive question, but actually there has been very little quantitative evolution experiments done at the level a physicist would like. We have constructed a linear array of coupled, microscale, patches of habitat in which we can study the adaptation and evolution of bacteria in complex, heterogeneous environments. When bacteria are inoculated into this habitat landscape, a metapopulation emerges. Our results illustrate the potential laying at the interface between nanoscale biophysics and landscape evolutionary ecology.
Friday, September 15, 2006, 11:00 a.m., B. H. Snell Hall, Room 214
Tri-Modal Self-Assembly Monosulfide Nanodome, Nanodot and Nanowire Arrays and Their Field Emission Properties
Prof. M. Cahay, Department of Engineering & Computer Engineering, University of Cincinnati
We will describe the first tri-modal self assembly where three distinct types of nanostructures –nanodomes, nanodots and nanowires – have been self assembled by pulsed laser deposition (PLD) of lanthanum monosulfide (LaS) on nanoporous anodic alumina films containing hexagonal arrays of cylindrical pores that are ~ 50 nm wide and ~ 500 nm deep. The nanodomes grow on the boundaries separating regions of the alumina film that have near perfect pore ordering, and their density is ~ 109/cm2. The nanodome diameter (at the base) is about 100 nm and the aspect ratio (height/diameter at the base) is between 1 and 3. Nanodots, on the other hand, nucleate on top of the alumina islands between adjacent pores. These are sites of minimal strain. The dots have a diameter of ~ 50 nm, a density equal to the pore density (1010/cm2) and an aspect ratio less than 1. Finally, LaS nanowires grow and completely fill the pores with a density of 1010/cm2. The nanodomes have turned out to be excellent field emitters, which have important commercial and military applications.
Friday, September 8, 2006, 11:00 a.m., B. H. Snell Hall, Room 177
Evidence for a dynamic phase transition in Ising-like [Co/Pt]3 magnetic multilayers
Dr. Daniel Robb, Colloid and Nanoparticle Research Group, Clarkson University
A dynamic phase transition (DPT) can be defined in general as a qualitative change in the behavior of a non-equilibrium system as a system parameter is varied. Just as equilibrium phase transitions structure our understanding of equilibrium thermodynamic systems, the presence of a DPT can serve as a useful reference point in our understanding of a non-equilibrium system. In computer simulations of the two-dimensional kinetic Ising model of a ferromagnet, a DPT with respect to the period P of an applied alternating magnetic field has been observed previously [1], which exhibits the same critical scaling as the second-order equilibrium phase transition in the two-dimensional Ising model [2].
Our collaboration has established the first convincing evidence for an experimental observation of this DPT, in an ultra-thin [Co(0.4nm)/Pt(0.7nm)]3 magnetic multilayer system. For several values of P and a ‘bias magnetic field’ Hb, the magnetization of the multilayer was measured for 50 cycles of an applied alternating field. The behavior of the dynamic order parameter, identified in simulations as the magnetization averaged over the ith field cycle, Qi, in the multilayer system is compared to the behavior of the dynamic order parameter in Monte Carlo simulations of the two-dimensional kinetic Ising model. The strong similarity in the behavior of the dynamic order parameter and its fluctuations, as a function of P and Hb, strongly suggests the presence of the DPT in the experimental system. In addition, an experimental image of the domain reversal pattern of the multilayer confirms the presence of the multi-droplet reversal process associated with the DPT in the kinetic Ising model. Following discussion of these results, further directions suggested by this research will be indicated.
[1] T. Tomé and M.J. de Oliveira, Phys. Rev. A 41, 4251 (1990).
[2] S.W. Sides, P.A. Rikvold, and M.A. Novotny, Phys. Rev E 59, 2710 (1999); Phys. Rev. Lett. 81, 834 (1998).
Friday, September 8, 2006, 11:00 a.m., B. H. Snell Hall, Room 177
Novel Micellar Cubic Structures, QL, from GMO/Water/Cosolvent Ternary Mixtures
Prof. Nissim Garti, Casali Institute of Applied Chemistry, The Hebrew University of Jerusalem
Polar lipid molecules such as glycerol monooleate (GMO) and polar solvent (usually water) can spontaneously organize in high order at the long-range distances while in the short-range, at atomic distances, they are disordered.
Liquid crystalline mesophases with a long-range order in one dimension are lamellar phases (Lα) while those showing two dimensional long-range order are known as hexagonal phases (HI and H2 for normal and reverse hexagonal) and those with three dimension long-range orders are lyotropic cubic phase (C). Hydrophobic effect with a variety of intra- and intermolecular interactions, in combination with a number of geometric packing constraints, are responsible for the degree of order.
In our recent studies we have discovered that ternary blends of GMO, water and cosolvent can form unique structures. The focus of this presentation is on a new mesophase that was formed as a result of phase transformations. The new structure was eluted from lamellar, cubic, and hexagonal isotropic liquid phases in ternary systems. The new phase, termed by us the QL mesophase, is very unique since it is transparent liquid phase with long-range order. The QL phase was studied by small-angle X-ray scattering (SAXS), cryo-transmission electron microscopy (cryo-TEM), self-diffusion NMR, DSC and conductivity methods. The unique rheological properties of a system totally fluid and yet non Newtonian will be discussed in view of the suggested structure of micellar discontinuous cubic phase.
Microstructure data as well as solubilization data of several nutraceuticals molecules and their bioavailability advantages will be presented.
Friday, April 28, 2006, 4:00 p.m., Bertrand H. Snell Hall, Room 214
Stirring up trouble: Multi-scale measures of mixing for steady scalar sources
Prof. Charles Doering, Department of Mathematics and Michigan Center for Theoretical Physics, University of Michigan, Ann Arbor
We study the evolution of passive scalar fields maintained by steady but spatially inhomogeneous sources and sinks and stirred by statistically stationary, homogeneous and isotropic incompressible flows, including “familiar” turbulence. The effectiveness of a flow field to enhance mixing over molecular diffusion is measured by the suppression of the space-time averaged scalar variance, the gradient variance (stressing small scales), and the inverse gradient variance (focusing on large scale fluctuations). Ratios of these variances without stirring to the corresponding variances with stirring provide non-dimensional measures of the “mixing efficiency” of the flow on different scales. In this work we derive rigorous estimates on these multi-scale mixing efficiencies for a variety of source distributions with general stirring flows including statistically homogeneous and isotropic velocity fields, and compare them with conventional (eddy diffusion) theory, direct numerical simulations and exact calculations for sample problems.
Friday, April 14, 2006, 4:00 p.m., Bertrand H. Snell Hall, Room 214
Electrochemical and Opto-Electrochemical Techniques for Characterization of Surface-Engineered Materials
Prof. Dipankar Roy, Department of Physics, Clarkson University
We have set up a multi-technique framework that allows for detailed examination of the mechanisms and kinetics of various complex reactions at different types of material interfaces.1 This experimental approach is based on the utilization of a relatively unique combination of a number of recently developed as well as traditional methods of electrochemistry. Often these measurements also are strategically coupled with certain in situ surface sensitive techniques of linear and nonlinear optics. Currently the capabilities of these combined electrochemical and opto-electrochemical procedures are being extended further to new fundamental studies of various surface-engineered materials. These latter systems include self-assembled nano-structured films of tailored surface functionalities, electrodeposited metallic multilayers, controlled corrosion tribo-chemical interfaces and surface-modified electrocatalysts. Apart from their utility in material characterization, the electrochemical measurements based on our newly developed time resolved technique of Fourier transform impedance spectroscopy are also found to be useful for studying the efficiencies and mechanisms of certain processes of surface engineering such as chemical/electrochemical mechanical planarization (CMP/ECMP)2 and corrosion preventive surface treatments. A selected set of results of our recent experiments will be discussed focusing primarily on a number of systems that are relevant for electrochemical and opto-electrochemical sensor technologies. Experimental results will also be presented for particular systems with potential applications in ECMP of wiring metals.
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1 http://people.clarkson.edu/~samoy/cr_projects.htm
2 http://people.clarkson.edu/~surop/fteis.htm
Monday, April 3, 2006, 4:00 p.m., Science Center Room 356
The germanate “anomaly” and the structure of germanate glasses
Prof. Grant S. Henderson, Geology Department, University of Toronto
Glasses have important technological uses, and the role their structure plays in determining physical properties and behaviour, remains a central issue in glass science. Alkali containing germanate glasses exhibit maxima or minima in several physical properties upon the addition of alkali-oxide. This behaviour is termed the germanate anomaly and is the physical mechanism which makes germanate glasses useful as self focussing optical fibres. Traditional explanations for this behaviour have revolved around coordination changes of Ge. Two principal models have been proposed. The original and most widely accepted explanation invokes the formation of Ge in 6-fold coordination ([6]Ge) while the second involves small ring formation without the need for the presence of [6]Ge. More recently, it has been suggested that 5-fold coordinated germanium ([5]Ge) may play a role in the anomaly. Determining germanium coordination is difficult but recently O K-edge XANES spectroscopy has proven useful and indicates that [5]Ge does indeed form but only at the anomaly maximum. However, Raman spectroscopy of Germanophosphate glasses that also exhibit the anomaly, indicates that even though a higher coordinated germanium species exists in the glass, it does not play a significant role in the anomalous behaviour.
Friday, March 31, 2006, 4:00 p.m., Bertrand H. Snell Hall, Room 214
Quantum Dots: Paving the Way to Fully Coupled Models
Prof. Roderick Melnik, Mathematical Modelling and Computational Science, Wilfrid Laurier University, Canada
Low-dimensional semiconductor nanostructures (LDSNs) are receiving increasing attention as key components of semiconductor lasers, semiconductor optical amplifiers, and other optoelectronic devices. Quantum dots (QDs) - LDSNs in which the motion of electrons is confined from all three spatial dimensions - can be used as biological tags in clinical research and DNA analysis, while the idea of using a spin confined to a QD as a qubit promises imminent breakthrough in quantum information processing. Despite a wide range of current and potential applications, optoelectromechanical properties of QDs are still frequently analyzed with simplistic mathematical models, incapable to account correctly for strain, piezoelectric coupling, and other important effects. In this talk I will provide a survey of the existing models for bandstructure calculations focusing on coupled and nonlinear effects and their incorporation in new models developed in our group for the analysis of properties of QDs. Several numerical examples will be given to illustrate the theory.
Friday, March 24, 2006, 4:00 p.m., Bertrand H. Snell Hall, Room 214
On the Crossroad of Nano -Physics, -Chemistry, and -Biology
Prof. Igor Sokolov, Department of Physics, CAMP, Clarkson University
Prof. Sokolov will present research activity of his group for the last two years which is related to nanoscale Physics, Chemistry, and Biology. The talk will consist of three parts: NanoBio Chemistry/Physics; Advanced NanoMaterials; Atomic Force Microscopy. NanoBioChemistry/Physics: Novel methods of studying human cells to study cell aging, cancerous cells; a new approach to investigate various skin care products; novel “anti-aging” cream. Advanced NanoMaterials: Electrospinning technique to produce submicron carbon fibers; novel functional/protective coatings; controlled slow drug release; synthesis of nanoporous colloids; synthesis of ultra bright fluorescent particles; self-healing materials. Atomic Force Microscopy: Mechanics of structural fibers at nanoscale; structural changes and mechanics of glucose receptor molecules; direct measurements of interaction between single nanoparticle and various surfaces.
Friday, March 10, 2006, 4:00 p.m. BH Snell Hall, Room 214
Coherence Out of Noise?
Dmitry Solenov, Department of Physics
The results of the recent investigation on decoherence processes in quantum computing systems are presented. We develop two positivity-preserving techniques of evaluating decoherence suitable to handle essentially time-dependent quantum gates. The effect of the latter on decoherence is analyzed. Coherent interaction between qubits (e.g., spins) due to common thermal bosonic environment (e.g., phonons) and noise estimates are obtained. We analyze the time scales and distances for which the interaction stays coherent and entanglement is developed.
Monday, February 27, 2006, 4:00 p.m. Science Center, Room 356
Biomechanics across scales: from the subcellular to the organismal
Prof. G. Forgacs, George H. Vineyard Professor, Department of Physics and Biology University of Missouri at Columbia
The present talk is a short overview of biomechanics, the discipline that deals with the viscoelastic properties of biological materials. The usefulness of biomechanics will be illustrated through specific applications and techniques at the intracellular, cellular, multicellular and organismal level. Special emphasis will be put on relevance of the garnered knowledge to solve biologically relevant issues. Thus, at the intracellular level, the viscoelastic properties of the cytoskeleton will be explored by magnetic tweezers and used to improve on present techniques to cryopreserve oocytes. At the cellular level AFM-based force probe and the magnetic tweezers will be employed to learn about the extravasation of leukocytes and tumor cells through blood vessel walls in the course of inflammatory responses and metastatic transformations. At the multicellular or tissue level special tensiometry will be introduced to study cell adhesion. Finally, on the organismal level it will be discussed how biomechanics can be used to construct, via bioprinting, three-dimensional living structures or organ modules of specific geometry and functionality.
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Friday, February 17, 2006, 4:00 p.m. BH Snell Hall, Room 214
Modeling of Self-Assembling Nano-Structures in Thin Constrained Layers
Prof. Andrei Artemev, Department of Mechanical & Aerospace Engineering, Carlton University, Ottawa
The formation of patterns produced by misfitting coherent domains in thin constrained layers was studied using the phase-field method based on microelasticity theory. Simulation was performed for (i) multi-variant systems in which misfit strain can be accommodated by assembling domains of different orientation variants and (ii) for mono-variant systems. Different types of regular patterns were obtained including columnar, striped, labyrinth, and lattice patterns. The effects of thickness of polydomain layer, misfit between domains, and misfit with monodomain constraining layer on the patterns were studied. The structure maps illustrating conditions at which different types of structure can be obtained were produced. The results of computer simulation are compared with simplified analytical models of domain structures in constrained layer.
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Friday, February 10, 2006, 4:00 p.m. BH Snell Hall, Room 214
The Influence of Decoherence on Electron Transport in Quantum Dots Nanostructures
Prof. Leonid Fedichkin, Center for Quantum Device Technology
The dynamics of electron tunneling in a system of coupled quantum dots are considered in the presence of decoherence. The behavior of electron transport is strongly affected by interaction with quantum point contacts placed nearby. The evolution of the electron density matrix is derived. As the level of quantum noise and the resulting decoherence increase, we observe a crossover from a quantum-coherent oscillatory dynamics to a diffusive classical motion.
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Friday, January 27, 2006, 4:00 p.m. BH Snell Hall, Room 214
Diffusion-Limited Annihilation and Coalescence on the Bethe Lattice
Prof. Daniel ben-Avraham
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Friday, January 13, 2006, 4:00 p.m. BH Snell Hall, Room 214
The Faradaic Efficiency of Material Removal in Voltage Pulse Modulated Electrochemical Mechanical Planarization of Copper
Pubudu Goonetilleke, Department of Physics
The technique of electrochemical mechanical planarization (ECMP) allows for low-pressure processing of copper interconnects containing mechanically fragile low permittivity dielectrics. Removal of surface layers from protrusion regions of Cu in this approach is controlled with externally applied anodic voltages, and the faradaic efficiency (thickness of Cu layer dissolved per unit charge) of this process is dictated by the electrolyte composition, as well as by the temporal profile and magnitude of the activation voltage. The present work investigates the experimental factors that affect the faradaic efficiency of Cu ECMP in the absence of mechanical polishing in an electrolyte of citric acid (complexing agent) and H2O2 (oxidizer). The voltage activation scheme here involves rectangular pulse-modulation using both stationary and rotating Cu (coupon and disc) electrodes. The underlying theoretical framework of this method is discussed, the corrosion parameters are analyzed and the experimental considerations for designing the electrochemical control variables for ECMP are explained. The electrochemical rates and faradaic efficiencies of Cu removal are measured as functions of voltage pulse widths and sample rotation rates. Contributions of faradaic and nonfaradaic reactions to Cu removal under electrochemical control are discussed, and possible chemical roles of citric acid in determining the voltage-activated current profiles are examined.
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Friday, November 18, 2005, 4:00 p.m. Bertrand H. Snell Hall, Room 212
Late Transition Metal-Containing Nanostructures
Prof. Hong Yang, University of Rochester
Late transition metals, their oxides, alloys and intermetallics are important materials because of their electronic, magnetic and catalytic properties. Our group has focused on the non-hydrolytic synthesis and property of nanostructured materials containing Pt, Rh, Fe, Co, and Ni. We have tested the applications of such nanomaterials as low-temperature fuel cell catalysts for direct methanol oxidation and as building blocks for the generation of magnetic nanocomposites. In this presentation I will discuss our recent developments in the following aspects: 1) synthesis of uniform low-dimensional nanostructures, such as nanorods, and branched nanostructures. Focus will be placed on the uniform platinum planar multipods, iron-containing nanostructures and their assembly. The potential benefits of using imidazolium ionic liquids as solvents in the synthesis of nanomaterials will be discussed; 2) strategy for controlling the chemical composition and crystalline phase of alloy and intermetallic nanostructures through core-shell configuration and co-reduction process; 3) electrocatalytic and magnetic properties of Pt-based alloys, intermetallics and nanocomposites (Pt and PtRu), and 4) magnetic properties of FePt-based nanocomposites.
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Friday, November 11, 2005, 4:00 p.m. Bertrand H. Snell Hall, Room 212
Dynamic Self-Consistent Field Theory of Inhomogeneous Polymer Fluids: Achievements and Challenges
Prof. Yitzhak Shnidman, City University of New York
At high concentrations, flexible polymer chains in a homogeneous fluid at equilibrium are ideal (noninteracting), with conformations generated by finite Wiener random walks. In an inhomogeneous fluid, interactions of a polymer's Kuhn segment with other fluid components can be approximated by an external potential represented by a self-consistent field (SCF), and chain conformations are generated by random walks in this potential. We have developed a dynamic self-consistent field (DSCF) theory [M. Mihajlovic, T. S. Lo and Y. Shnidman, Phys. Rev. E 72, 041801 (2005)], where the effect of flow on chain conformations is modeled with elastic dumbbells and related to the stepping probabilities in a random walk. Our DSCF theory couples the time evolution of chain conformation statistics with Markovian transport equations for local volume fractions and momentum densities, based on conservation laws formulated on the Kuhn length scale. I will present applications of this theory to unentangled polymer melts and blends that are sheared in a planar channel, and compare the results to a molecular dynamics study of the same systems [T. S. Lo et al., Phys. Rev. E 72, 040801R (2005)]. We will conclude with a discussion of some obstacles hindering the application of the DSCF approach across disparate time and length scales in entangled inhomogeneous polymer fluids under shear, along with ideas for overcoming them that are based on quantum mechanical analogies and stochastic models for generating chain conformations and fractal segmental transport transcending the Markovian and Wiener assumptions.
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Friday, November 4, 2005, 4:00 p.m. Bertrand H. Snell Hall, Room 212
Mechanism of Growth of Monodispersed Colloids by Nucleation and Aggregation of Nanosize Subunits
Igor Sevonkaev, Clarkson University
The importance of well-defined dispersions of particles of different shapes, ranging in sizes from nanometer to colloidal, has been widely recognized in applications and in basic studies of advanced materials. Our program endeavors to advance understanding of formation of uniform particles of simple and composite structure, with focus on synthesis involving nanosize particles and their new unique properties for dimensions smaller than the typical submicron-size colloid scales. Presently, there is convincing experimental evidence that many monodispersed colloids of various shapes, obtained by precipitation in solutions, are formed by aggregation of such nanosize units. Our recent theoretical explanation of this process expands the classical model of uniform particles' formation, by LaMer, and offers an interesting link between nanosize and micrometer size particles. It explains many properties of the latter which could not be previously understood. Thus, the colloid and nanoscale particle dispersions are actually closely related. Our recent experimental work has verified the model for synthesis of monodispersed Au and CdS colloid particles, and we presently study MgF2 colloids. Our future theoretical work will be focused on understanding the shape selection.
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Friday, October 28, 2005, 4:00 p.m. Bertrand H. Snell Hall, Room 212
Statistical Physics of Citations
Prof. Sidney Redner, Boston University
This talk will begin with basic empirical facts about the network of scientific citations, based on the entire corpus of Physical Review publications from the past 110 years. Intriguingly, the evolution of citations appears to be described by linear preferential attachment. A master equation approach will be developed to characterize this and related popularity-driven networks. One basic characterization is the citation distribution of the network, namely, the probability that a publication has a given number of citations. The conditions that give rise to exponential, power-law, or more singular citation distributions will be elucidated for general classes of networks. Comparison between the theory and the citation data of Physical Review will be made.
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Friday, October 21, 2005, 3:30 p.m. Bertrand H. Snell Hall, Room 212
Synthesis and Electrochemical Behavior of Some Transition Metal Oxides and Phosphates
Prof. M. Stanley Whittingham, State University of New York at Binghamton
There has been much interest in the electrochemical redox behavior of oxides and phosphates in an attempt to replace the expensive and relatively scarce cobalt containing oxides. Although a number of oxides can be readily synthesized, their structural stability is often insufficient to allow the extended insertion and removal of lithium without major structural change or degradation. At the same time, the precise positions of the cations in the lattice have a major impact on both the structure retention and on the diffusion of lithium ions. The mixed metal oxides, Li(MnNiCo)O2, vanadium oxides with various morphologies, and the iron and vanadium phosphates will be used as examples of the critical role synthesis, structure and atomic ordering play in the electro-chemical properties of these compounds.
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Friday, September 23, 2005, 4:00 p.m. Bertrand H. Snell Hall, Room 212
How can superfluidity occur in a crystalline solid?
Dr. N. Prokofiev, University of Massachusetts at Amherst
We prove that the necessary condition for a solid to be also a superfluid is to have gapless (zero-point) vacancies, or interstitial atoms, or both, as an integral part of the ground state. As a consequence, in the absence of symmetry between vacancies and interstitials, superfluidity has zero probability to occur in an ideal, commensurate solid which breaks continuous translation symmetry. We discuss recent 4He experiments by Kim and Chan in the context of this theorem, question its bulk supersolid interpretation, and offer an alternative explanation in terms of superfluid interfaces between helium microcrystallites. Model simulations of lattice bosonic solids show that superfluid solid-solid interfaces and recrystallization waves are possible in a wide parameter range. Such key features in the experimental data on helium-4 as the superfluid fraction dependence on temperature and the effect of small helium-3 concentration can be understood qualitatively within the interface network model.
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Friday, September 16, 2005, 4:00 p.m. Bertrand H. Snell Hall, Room 212
Entanglement Sudden Death: How is a Bipartite Quantum State Affected by Environmental Noise?
Dr. Ting Yu, University of Rochester
Our physical world, in the form of fluctuations and dissipation, inevitably intervenes in the dynamics of quantum systems. As a result, while atomic coherence decreases exponentially, quantum entanglement (nonlocal coherence) may completely decay to zero in just a finite time, i.e., it may experience "entanglement sudden death." In this talk, we show that entanglement sudden death is a generic feature of even the simplest bipartite quantum system interacting with phase and amplitude damping noises. Moreover, we have found that when two or more noises are active at the same time, the effects of the combined noises may be rather peculiar.
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Friday, July 29, 2005, 10:30 a.m. Science Center, Room 356
Building Extension to the Atomic Force Microscope to Study Electronic Properties of Nanosize Objects
Michael McGuire, Clarkson University
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Monday, July 11, 2005, 1:00 p.m. Bertrand H. Snell Hall, Room 214
Kinetics of electrochemically controlled surface reactions on bulk and thin film metals studied with Fourier transform impedance spectroscopy and surface plasmon resonance techniques
Kankoe A. Assiongbon, Clarkson University
A wide variety of electrochemical reactions occurring at metal/liquid interfaces were investigated on bulk and thin film electrodes in various aqueous environments using Fourier transform electrochemical impedance spectroscopy (FT-EIS) and surface plasmon resonance (SPR) techniques. These reactions include electrodeposition of metals and anions (relevant for thin film fabrication), oxidation and dissolution reactions (relevant for chemical mechanical planarization) and electrocatalysis (relevant for fuel cell applications).
A brief summary of the FT-EIS and SPR techniques and their working principles will be presented. Specific advantages of these techniques for kinetic surface studies will be noted.
A specific problem involving catalysis of methanol on a thin film Au (~ 40 nm) in alkaline medium will be used in this presentation to illustrate the applications of the different techniques used. The FT-EIS data provided detailed kinetic parameters that characterize electro-oxidation of methanol. This led to a quantitative understanding of the mechanism of the probed surface reactions. At the same time, the SPR data provided with high accuracy the optical parameters and electronic characteristics of the thin film Au. The two techniques provided a complete understanding of the observed surface reactions, and showed consistency in data.
June 12-15, 2005
79th ACS Colloid and Surface Science Symposium
Organized by: ACS Division of Colloid and Surface Chemistry
Hosted by:
Clarkson University and
Center for Advanced Materials Processing (CAMP), Potsdam, NY
April 1, 2005 — 4 p.m.
Bertrand H. Snell Hall, Room 214
Direct Scaling Properties of Korean Stock-Market Index
Professor Jae Woo Lee — Department of Physics, Inha University, Korea, and School of Computational Science, Florida State University
We apply methods of statistical physics to analyze the Korean stock-market index. We consider the return and volatility of the stock-index. We observe some stylized facts in the stock index. The probability distribution of the return deviates from Gaussian and shows fat tails. The autocorrelation functions of the return and volatility follow a power-law in the restricted range. We also observe the power-law behavior in the waiting-time distribution of the return. Fluctuations of the stock index show multifractal behaviors. To clarify the origin of the multifractality, we smooth the time series through convolution with Gaussian function. After convolution we observe that the multifractality disappears in the short-time scaling regime, but remains in the long-time scaling regime.
We generate network structure by the cross correlation between the indexes of the individual company. The network shows the properties of scale-free and small-world network.
March 25, 2005 — 4 p.m.
Bertrand H. Snell Hall, Room 214
Evaluation of Decoherence for Quantum Control and Computing
Arkady Fedorov — Clarkson University
Different approaches in quantifying environmentally-induced decoherence are considered. We identify a measure of decoherence, derived from the density matrix of the system of interest, that quantifies the environmentally induced error, i.e., deviation from the ideal isolated-system dynamics. This measure can be shown to have several useful features. Its behavior as a function of time has no dependence on the initial conditions, and is expected to be insensitive to the internal dynamical time scales of the system, thus only probing the decoherence-related time dependence. As a demonstration, the decoherence of an electron in double quantum dot due to the interaction with acoustic phonons is considered. For the case of many-particle collective decoherence the property of additivity is established: in the regime of the onset of decoherence, the sum of the individual qubit error measures provides an estimate of the error for a several-qubit system, even if the qubits are entangled, as expected in quantum-computing applications. The problem of dipole-dipole decoherence of nuclear spins is studied for strongly entangled spin cluster. Our theory is consistent with previous theoretical findings and recent experiment reported in decoherence of correlated spin clusters.
March 11, 2005 — 4 p.m.
Bertrand H. Snell Hall, Room 214
Measurement of electrochemical differential capacitance under potentiodynamic conditions
Chris Pettit — Clarkson University
The differential capacitance technique is widely used for the study of reactions occurring at a metal-liquid interface. Cyclic voltammetry (a potentiodynamic technique) is used to examine the voltage dependant kinetics of charge transfer reactions occurring at this interface. The measurements of these kinetic parameters are typically performed using single (low) frequency AC voltammetry techniques with phase sensitive measurement equipment. The work to be presented will use a multi frequency time resolved Fourier transform electrochemical impedance spectroscopy (FT-EIS) technique that provides us with voltage dependant and time resolved data simultaneously to examine these kinetic parameters. The FT-EIS technique will be used to illustrate the constraints of the single frequency techniques. In order to study these kinetic parameters we examine surface reactions of I adsorption on a polycrystalline copper sample in acidic (HClO4) and alkaline (KOH) solutions.
March 4, 2005 — 4 p.m.
Bertrand H. Snell Hall, Room 214
Direct Study of Interaction of a Single Nanoparticle with Surfaces by the AFM
Ong Khac Quy — Clarkson University
Study of interactions of nanoparticles with various surfaces is of great interest for modern nanotechnology. In this talk we will present a new method to measure such interactions directly. We report the first successful method on gluing nanosize particles to the tip of atomic force microscopy (AFM) and subsequent measurement of the particle interaction with various surfaces. Specifically, we will focus on ceria nanoparticles and either silica or polyurethane surfaces. Application to Chemical-Mechanical planarization (CMP) will be described.
Secondly, we will discuss the interaction between silica nanoparticles and silica plane wafer to address the fundamental issue, connection between adhesion and long-range forces. We measure both types of forces by means of the AFM in aqueous solutions of various acidity. A simple theory explaining the observed behavior will be outlined.
February 25, 2005 — 4 p.m.
Bertrand H. Snell Hall, Room 214
New quantum device opportunities in ultrathin silicon-on-insulator
Prof. A. Zaslavsky — Brown University
Silicon-on-insulator (SOI) transistors built in thin fully-depleted Si channels on top of an insulating buried oxide are predicted to take over from bulk Si CMOS devices because of their superior scaling properties. The continuing miniaturization of SOI devices, with available Si channel and gate insulator thickness dropping to the nanoscale, as well as integration of ultrathin SOI with novel dielectrics and gate materials, is opening the door to Si-compatible quantum effect devices. This is important because a great many quantum effect devices demonstrated in bandgap-engineered III-V hetero-structures have not been used in mainstream technology, which is dominated by Si.
Here we will present some proof-of-concept structures that appear suitable for exploitation in the SOI world: lateral interband tunneling transistor (LITT), vertical tunneling transistor (VTT), VTT-based intersubband laser, and real-space transfer transistors. All of these devices have been envisaged in III-V heterostructures, but SOI implementations offer both compatibility and functional advantages. To become useful, these devices need fabrication advances beyond the current state of the art. Still, the point is that novel devices and functionalities can still be grafted onto the rapidly growing SOI technology — an opportunity that device physicists should not miss.
February 11, 2005 — 4 p.m.
Bertrand H. Snell Hall, Room 214
AFM Study of Mechanical Properties of Glucose/Galactose Receptor Films: Towards Development of a New Family of Biosensors
Venkatesh SubbaRao — Clarkson University
Recently a periplasmic glucose/galactose binding protein, GGRQ26C, immobilized on gold surface has been used as an active part of a glucose biosensor based on quartz microbalance technique (QCM). However the nature of the glucose detection was not clear. Recently we have found that the receptor protein film immobilized on the gold surface increases its rigidity when glucose is added, which explains the unexpected detection signal. To study the rigidity change, we developed a new fast and simple method based on using atomic force microscopy (AFM) in tapping mode. The method was verified by explicit measurements of the Young's modulus of the protein film by conventional AFM methods. Since there are a host of receptors that undergo structural change when activated by ligand, AFM can play a key role in the development and/or optimization of biosensors based on rigidity changes in biomolecules. In this talk both the theory of the developed method and the experimental results obtained will be presented.
February 4, 2005 — 4 p.m.
Bertrand H. Snell Hall, Room 214
ECMP of Copper for Microchip Fabrication
Pubudu Goonetilleke — Clarkson University
Chemical-mechanical planarization (CMP) of copper is an essential component of materials processing in the fabrication of integrated circuits. CMP requires the application of a considerable down-force in its polishing step, and hence is unsuitable for systems containing mechanically weak dielectric layers under the Cu lines. Recently, electrochemical-mechanical planarization (ECMP) has emerged as a possible extension of CMP, where through voltage-induced removal of Cu surface layers, one can substantially minimize the down-force necessary for mechanical polishing. However, the detailed electrochemical factors that are central to designing efficient polishing slurries for ECMP are not clearly understood at the present time. In this presentation, we study the relative electrochemical effects of different chemical additives in a peroxide-based electrolyte containing glycine. We show that unlike the case of CMP, H2O2 (an oxidizer) in ECMP of Cu does not provide any measurable advantages, and may actually have a negative effect on voltage-controlled removal of Cu layers.
Further information is found at: http://people.clarkson.edu/~samoy/ECMP.htm
January 28, 2005 — 4 p.m.
Bertrand H. Snell Hall, Room 214
Why Chemical Mechanical Planarization (CMP) remains a challenge?
Prof. S.V. Babu — Clarkson University
January 21, 2005 — 4 p.m.
Bertrand H. Snell Hall, Room 214
Nanosensors with mesoscopic number of quasiparticles:
Next generation detectors, photon counters, and calorimeters
Professor V. Mitin — SUNY Buffalo
The steady and impressive progress in nanotechnologies of semiconducting and superconducting structures leads to new intriguing possibilities for sensors of electromagnetic radiation. Novel approaches to detection of low-energy (submillimeter and infrared) photons are based on implementation of nanostructures with small number of quasiparticles. In general, quantum sensors work as photomultipliers. An incoming photon generates a photoelectron, which initiates a large of low energy quasiparticles. Finally, this cascade leads to a measurable current pulse or change of material parameters. Straightforward implementation of this method for low-energy quanta hindered, because these photons are a thousand times less energetic than the optical ones, and the number of generated electrons is insufficient to overpower the detector noise. While numerous technical problems can be solved, the fundamental limitation of the detector sensitivity is determined by fluctuations of the number of quasiparticle excitations. Thus, a small number of quasiparticles in a sensor is the key issue for high performance which imposes the use of nanostructures.
In this talk, I review novel nanosensors based on quantum dots and superconducting nanowires. With controllable electron relaxation, such sensors can be employed as relatively slow ultra-sensitive detectors or fast (picosecond) photon counters. I discuss electron kinetics in nanostructures, recent experiments in this field, and new ideas in design of photon counters, detectors, and calorimeters. Nanosensors are expected to deliver the unique performance: the noise equivalent power of the order 10 20 W/ Hz and the energy resolution of 10-21-10-23 J. The counter can resolve submillimeter and terahertz photons with the counting rate of 1011 count/s. These sensors are of great interest for single-molecule spectroscopy, submillimeter astronomy, and nanoscale thermophysics and chemistry.
The talk is based on the works made in collaboration with A. Sergeev, B.C. Karasik, M.E. Gershenson, V. Ryzhii, V. Pipa, and M. Stroscio.
November 19, 2004 — 4 p.m.
Bertrand H. Snell Hall, Room 214
Designer Nets from Local Strategies
Hernan Rozenfeld — Clarkson University
Recently much effort has been devoted to the study of large networks that surround us in everyday life, such as the Internet and the World Wide Web or social networks of collaborations. A majority of these networks share a characteristic property: a scale-free degree distribution.
Most growth models that produce scale-free networks rely on global properties of the network. Those algorithms require global knowledge of the degree of all present nodes. While global algorithms have contributed immensely to our understanding of how scale-free degree distributions might emerge, in most common situations it is more likely that networks evolve by a set of local rules.
We propose a local strategy for constructing scale-free networks, based on the redirection technique of Krapivsky and Redner (KR). Our method includes a set of external parameters that enable fine tuning of the network properties, while guaranteeing a scale-free tail with a given degree distribution exponent.
November 5, 2004 — 4 p.m.
Bertrand H. Snell Hall, Room 214
Mechanism-Driven Synthesis and Manipulation
of High Quality Nanocrystals
Prof. Xiaogang Peng — University of Arkansas
To exploit their size dependent properties, colloidal nanocrystals must be made to be nearly monodisperse, which is a challenge in the field of nanomaterials. Growth mechanisms of colloidal nanocrystals have been studied systematically, and the resulting knowledge was found to be extremely valuable for the design of "environmentally benign and user friendly" synthetic schemes for nanocrystals with a variety of compositions and complex structures. For most applications, the processibility of the nanocrystals must be improved after synthesis. The results will show that processing of nanocrystals depends on the knowledge of surface chemistry and ligand chemistry of colloidal nanocrystals. Optimal design of the ligands for nanocrystals will be discussed.
October 29, 2004 — 4 p.m.
Bertrand H. Snell Hall, Room 214
Aharonov-Bohm effects in entangled molecules
Prof. H. L. Frisch — SUNY Albany
Molecules which are magnetic and conducting, if suitably entangled (e.g., catenanes, knots) could exhibit Aharonov-Bohm effects which can be viewed as particular examples of a Berry phase. The corrections to the quantum energy levels reflect the entangled geometry of the molecules and, while small (they are proportional to the square of the fine structure constant) may be observable. We illustrate these corrections for a number of catenated and knotted structures. For couplings between the components of a catenane (link), the Aharonov-Bohm corrections are determined by integer-valued linking numbers. For knots, the Aharonov-Bohm correction is proportional to the geometric writhe of the knot.
October 22, 2004 — 4 p.m.
Bertrand H. Snell Hall, Room 214
Quantum State Retrodiction
Prof. P. K. Aravind — Worcester Polytechnic Institute
In quantum state retrodiction, the object is to predict the outcome of a measurement made on a quantum system as a result of measurements made on it before and after that time. In an early illustration of this technique, Vaidman, Aharanov and Albert showed how to use suitable pre- and post-selected measurements on a spin-half particle to correctly predict its spin eigenvalue along any of three orthogonal directions at an intermediate time, in apparent violation of the basic tenet of quantum mechanics that prohibits the existence of sharp eigenvalues for all of a set of noncommuting observables. This talk will introduce the problem, discuss its history, review the various generalizations of it that have been solved to date, and also mention a recent experimental realization of the original version of it. A particular variant of the problem solved by the speaker will be presented in greater detail. Finally, a discussion will be given of the relationship of the retrodiction problem to two other problems of great current interest: the construction of mutually unbiased sets of bases in arbitrary dimension, and the determination of the Wigner function of a discrete quantum system via the technique of "quantum tomography." An attempt will be made to identify unsolved problems and emerging themes in this still unfolding area of activity.
October 8, 2004 — 4 p.m.
Bertrand H. Snell Hall, Room 214
Oxidation of methanol on gold for fuel cell applications: Investigation of surface reactions using surface plasmon resonance and electrochemical impedance techniques
Kankoé Assiongbon — Clarkson University
Electro-oxidation of methanol has been extensively studied, mainly for the purpose of its attractive interest in direct methanol fuel cell (DMFC). DMFC has potential promises in developing portable power sources, electric vehicles, etc. However, a challenging problem in its development is to find an electrocatalyst electrode in an appropriate supporting electrolyte that can effectively enhance the kinetics of methanol oxidation. Pt and Pt-based alloys are widely used in acidic medium, however, electro-oxidation of methanol on them occurs with CO poisoning effects, leading to a considerable decrease in the catalytic activity of these metals.
The catalytic activity of Au toward methanol oxidation in alkaline medium, has given efficient results in DMFC applications. In the present work, we study electro-oxidation of methanol on a thin film Au (~ 40 nm) in alkaline medium. Optical technique of angle resolved surface plasmon resonance (SPR), under potentiodynamic conditions, in the Kretschmann geometry for attenuated total reflection and electrochemical techniques of cyclic voltammetry (CV) and time resolved Fourier transform electrochemical impedance spectroscopy (FT-EIS), are used to carry out this study.
Even though electro-oxidation of methanol is widely studied, its mechanism is still not well established. The SPR data analyses, based on Maxwell equations and Fresnel complex reflection coefficients, provide with high accuracy the optical parameters of the thin film Au, and quantified understanding of the observed surface reactions. At the same time, the FT-EIS data analyses provide quantified parameters of kinetics of Au catalytic activity toward methanol oxidation. Based on the experimental results of the two techniques used in this work, we proposed a model for surface reactions on Au.
October 1, 2004 — 4 p.m.
Bertrand H. Snell Hall, Room 214
Multiscale Modeling in Nanoscale: Physical and Biological Systems
Professor S. K. Nayak — Rensselaer Polytechnic Institute
This talk will present an overview of our recent multiscale modeling work in nanostructured materials.* The systems include carbon nanotube for sensing applications [1], molecular wires for spintronics applications [2], catalytic properties of oxide and metal clusters [3], and surfactant mediated magnetic quantum dots. We will also present our recent work on biological systems such as in Intein protein and Subtilisin enzyme.
[1] Appl. Phys. Lett. 81, 2638 (2002).
[2] Phys. Rev. B 68, R100407 (2003).
[3] Phys. Rev. B Rapid Comm. (2003).
*Work done in collaboration with A. Selloni (Princeton University), P. M. Ajayan, S. Kumar, S. Garde, G. Belfort (RPI)
September 24, 2004 — 4 p.m.
Bertrand H. Snell Hall, Room 214
Closed-Loop Feedback Control of the Turbulent Flow over a Wing
Professor Mark Glauser — Syracuse University
The flow over a NACA-4412 airfoil is experimentally used as a means for demonstrating a practical closed-loop feedback control based on low dimensional representations of the flow. The aim is to delay the separation of the flow and therefore the stall of the wing using input from surface pressure measurements only, as the angle of attack is increased using a smart, cost-efficient and autonomous actuation. Proper Orthogonal Decomposition (POD) lets us reduce the order of the complex turbulent system and extract from the flow only the most energetic features fundamental for control. Estimated measurements of the state of the flow are taken through the modified Linear Stochastic Measurement (mLSM) using the multiple pressure measurements along the chord only. The amplitude of the leading edge zero net-mass flow actuation is controlled by the flow itself: as the angle of attack increases, the structures convected over the wing grow larger, the estimated POD/mLSM coefficients increase along with the actuation amplitude accordingly. Initial exciting results from such a simple feedback control will be presented. The next step for a more elaborate control involves the development of a model or plant for our system. To do so, we are developing a set of ODEs for the POD coefficients. The form of the ODEs is guided by a Galerkin projection of the NS equations. In this case however, we train this system with experimental data in order to get the final form of the time-evolution equations for the POD coefficients. In this talk, the early results of the dynamical system will also be presented and some ideas on how to incorporate such a system into feedback flow control discussed.
September 17, 2004 — 4 p.m.
Bertrand H. Snell Hall, Room 214
Electrochemical Methods in Microelectronics, Nanotechnology, and Biosensing
Professor Ian Suni — Clarkson University
Ongoing research from Ian Suni's laboratory (chemical engineering department) will be described in the following areas:
Cu electropolishing for planarization of ULSI devices
Pulse reverese electrodepositon of metallic nanoparticles
Electrochemical deposition of metallic nanowires (with Prof. Sokolov)
Electrochemical impedance methods for biosensing (with Prof. Luck)
September 10, 2004 — 4 p.m.
Bertrand H. Snell Hall, Room 214
Self-Assembled Nanoporous Silica: Synthesis, Morphogenesis, and Applications
Yaroslav Kievsky — Clarkson University
We study the process of self-assembly of nano(meso)porous silica particles via surfactant templating. The enormous area of this material potential use attracts growing interest to its synthesis. To control the assembly of the silica shapes, we need to know details of the shaping mechanism. Process of creation of the mesoporous silica includes two stages: 1) growth of the liquid crystalline template, and 2) solidification of this template via polymerization of silica precursor (TEOS). Material obtained as a result of cationic surfactant templating (MCM-41, hexagonal nanostructured silica) features nanosize highly uniform porosity, and a large variety of shapes and their sizes.
Recently suggested Origami-type mechanism for synthesizing a rich family of nanoporous silica shapes, such as cones, tubes, and hollow helixes (Origami shapes) is also analyzed. The nanoporous shapes can reach hundreds of microns in size. These shapes can possibly serve as templates for various electronic and optical applications.
New conditions of self-assembly were found to form monoshaped nanoporous fibers, which are rather prospective as the hosts of lasing dye. Adding the laser dye to the synthesis of nanoporous crystals can potentially create the new class of dye lasers. The lasing dye will be sealed inside of silica pores preventing dye from oxidation. The surfactant molecules, which exist in the assembling solution, separate the dye molecules preventing their dimerization. Higher concentrations of dye, and consequently, higher lasing power can be achieved. It also leads to the decrease of the lasing threshold more than 10 times.
Other application of mesoporous silica is the coating of optical fibers by low refractive index films. For this purpose we created a nanoporous uniform film with a good adhesion to a glass fiber. It has not only lower refractive index but also can serve as a host, for example, for laser dye or quantum dots.
Shape details and their evolution were analyzed also by means of XRD, SEM, TEM, AFM, and optical microscopy techniques.
August 25, 2004 — 3:30 p.m.
Science Center, Room 307
The Design, Development, and Assessment of Advanced Modeling Based Project in Introductory Physics
Michael W. Ramsdell — Clarkson University
The results of Physics Education Research (PER) have provided much insight into developing more effective learning environments in introductory physics courses. In this dissertation we discuss the design, development, and implementation of two advanced Modeling Based Projects (MBP) that have evolved through research-based criteria. The projects serve as an alternative to the traditional laboratory portion of the introductory calculus-based courses taught at Clarkson University for undergraduate science and engineering majors. Each project has gone through several research-redevelopment cycles, through which the experimental apparatuses and pedagogical approaches have been improved. Details of each projects' pedagogical structure and implementation are presented and discussed within the context of recommendations established through PER. We present a detailed assessment of their effectiveness in terms of students' conceptual learning via the Force Concepts Inventory (FCI) and the Conceptual Survey of Electricity and Magnetism (CSEM), course performance via exam scores, and attitudes via the Maryland Physics Expectations Survey (MPEX). The results show that students who participate in MBP at Clarkson University achieve significant gains over students taught elsewhere with a traditional approach and similar gains to those achieved by others using well tested, research motivated curricula reforms. An internal evaluation was performed to compare students participating in MBP with a control group of statistically comparable students who attended traditional laboratories. The results reveal that students who participated in MBP obtain statistically significant gains over similar students taught with the traditional approach for both courses within the introductory sequence.