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That is the essence of science: ask an impertinent question, and you are on the way to a pertinent answer.

Jacob Bronowski

Colloquia

Talks start at 12:15 PM
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9
Feb '09
University of California, Riverside
Abraham G. Kofman
Analysis of Bell inequality violation and entanglement in superconducting phase qubits
Abstract:
We obtain optimal conditions for violation of the Bell inequality in the Clauser-Horne-Shimony-Holt form, focusing on the Josephson phase qubits. We start the analysis with the ideal case, and then discuss effects of measurement errors and local decoherence. We also consider the entaglement sudden death due to decoherence and show that the survival time for entanglement is generally much longer than for the Bell violation. Finally, we analyze effects of measurement crosstalk on the Bell violation in phase qubits. In particular, we propose a version of the Bell inequality which is insensitive to the crosstalk.
23
Feb '09
Princeton University
Stephen Lyon
Low-decoherence spin systems for solid state quantum computing
2
Mar '09
Columbia University
Ioannis John Kymissis
Optical and electrical probes for organic field effect transistor performance
Abstract:
Organic field effect transistors (OFETs) have been applied to a number of sensing and actuation systems which can take advantage of their low thermal budget and mechanical flexibility. Characterization of OFETs has been, however, a controversial topic because the conduction and transport models are unlike other well understood systems with accepted transport and device models. We have developed a family of techniques for the analysis and characterization of OFETs using a combination of optical and electrical probe techniques grounded in the physics underlying transport in organic semiconductor thin films. These techniques provide unique insights into device performance and also indicate ways to better fabricate and drive devices in practical circuits. These probes include the use of quasi-static charge metrology techniques, spatially and spectrally resolved photocurrent analysis, and the analysis of switching noise in OFET circuits. The physical basis behind these tools, as well as some analytical results which they have yielded in practical devices, circuits, and deliberately doped systems will be presented. The application of OFETs to a number of sensor systems including additive photodetectors and strain sensing will also be presented, along with what these analytical strategies can tell us about better ways to fabricate and drive these devices.
Notes:
COLLOQUIUM CANCELLED DUE TO SNOWSTORM
9
Mar '09
College of Staten Island, CUNY
Vadim Oganesyan
Many-body localization
23
Mar '09
RIKEN, Japan, and The University of Michigan, Ann Arbor
Anatoly Smirnov
Physics of natural nanodevices: proton pumps and rotary biomotors
Abstract:
In the process of respiration a living cell extracts energy from light or from food and converts it to a proton electrochemical gradient across an inner mitochondrial membrane. Mitochondria are small organelles inside the cell, which serve as efficient power plants. On the next stage of the respiration process protons flow back and rotate ATP synthase - a nanomachine using energy of mechanical rotation to synthesize the energy currency of the cell - the ATP molecules. Cytochrome c oxidase (CcO) is an enzyme, which is able to harness energy of food-stuff electrons and pump protons against the transmembrane voltage gradient. Despite the fact that the crystal structure of this enzyme is known in detail, a mechanism of proton pumping is poorly understood. The physical picture of the torque generation and a proton translocation in the rotary biomotor F0 of ATP synthase remains also unclear. In the present talk we apply the methods of quantum transport theory to the above-mentioned bioenergetic problems and develop a simple kinetic model of CcO proton pump. We also propose a theoretical description of the rotary biomotor F0. For realistic parameters the model of the CcO proton pump works with efficiency 95% and reproduces all four experimentally observed kinetic phases of the proton pumping process. The model of the rotary biomotor includes a stator part and a ring-shaped rotor having twelve proton-binding sites. We show that this system can work in three different regimes found in experiments: at low temperatures the loaded motor shuttles protons without producing any unidirectional rotation, whereas at higher temperatures the motor generates a constant torque with efficiency about 80%. Finally, the system works as a proton pump in the presence of a significant external torque produced by ATP hydrolysis.

References:
1. A. Yu. Smirnov, L. G. Mourokh, and F. Nori, Kinetics of proton pumping in cytochrome c oxidase. arXiv:0812.1785 (2008)
2. A. Yu. Smirnov, S. Savel'ev, L. G. Mourokh, and F. Nori, Proton transport and torque generation in rotary biomotors, Phys. Rev. E 78, 031921 (2008).
27
Mar '09
Department Electrical and Electronic Engineering, Toyohashi University of Technology
Mitsuteru Inoue
Magnetophotonic Crystals
30
Mar '09
Courant Institute, NYU
Gerard Ben Arous
Slow relaxation in random media
6
Apr '09
Stony Brook University
Chris Johnson Jacobsen
X-ray microscopy: new views of the complex world
Download PDF Remsen 105
Abstract:
X-ray microscopes are able to deliver images of micrometers-thick samples at tens of nanometers resolution. I describe new developments which go beyond simple imaging to look at the complexities of real life problems. By analyzing spectroscopic image sequences taken across the carbon absorption edge, one can understand nanoscale heterogeneities in organic chemistry relevant to biofuels materials as well as soil bacteria that act to alter metal toxicity. By combining fluorescence with phase contrast, one can obtain quantitative maps of trace element concentration which provides insights into problems such iron as a limiting factor in CO2 uptake by the oceans. By directly inverting diffraction data one can image cells without the resolution and damage-enhancing inefficiencies of x-ray lenses. These examples illustrate how new capabilities in x-ray microscopy are providing new views of the complex world that complement the capabilities of light and electron microscopy
Notes:
Joint with Chemistry Department
14
Apr '09
University of Central Florida
Mikhail Erementchouk
Semiconductor nonlinear optical response
20
Apr '09
City College of CUNY
Carlos Meriles
Larmor magnetometry as a path to spin sensing at the nanoscale
Notes:
Colloquium cancelled due to unforeseen consequences
27
Apr '09
Ruhr-Bochum University, Germany
Saskia Fischer
Magnetotransport in an asymmetric quantum wire loop
Abstract:
In this talk I will discuss recent results[1] on ballistic transport and quantum interference in a nanoscale quantum wire loop.Nanolithography is applied to fabricated multi-terminal quantum wire structures from GaAs/AlGaAs field-effect heterostructures hosting a high-mobility two-dimensional electron gas. Four-terminal measurements of current and voltage characteristics as a function of top gate voltages show negative bend resistance as a clear signature of ballistic transport. In perpendicular magnetic fields, phase-coherent transport leads to Aharonov-Bohm conductance oscillations, which show equal amplitudes in the local and the nonlocal measurement at a temperature of 1.5 K and above. We attribute this observation to the symmetry of the orthogonal cross junctions connecting the four quantum wire leads with the asymmetric quantum wire ring.
[1] S.S. Buchholz, et al. APL 94, 022107 (2009).
4
May '09
Boston University
Luca Dal Negro
Light in Deterministic Aperiodic Media
Notes:
Colloquium has been cancelled
11
May '09
Rutgers University
Andrew Baker
Molecular gas in high-redshift galaxies
Abstract:
Fully understanding the evolutionary state of a galaxy requires that we characterize its gas reservoir, of which the molecular component represents the mass directly available for star formation.I will discuss radio observations of molecular gas in two populations of star-forming galaxies at high redshift (selected based on their rest-frame ultraviolet and far-infrared emission) and what we can learn from them. I will highlight recent work with the "Zpectrometer" (a new, ultrawide bandwidth spectrometer for the 100m Green Bank Telescope) and prospects for future work with

ALMA (Atacama Large Millimeter/submillimeter Array).
1
Jul '09
CNRS/University of Joseph Fourier
Bart van Tiggelen
Theory and experiment of 3D Anderson localization from elastic waves towards cold atoms
14
Sep '09
Columbia University
Ioannis John Kymissis
Optical and electrical probes for organic field effect transistor performance
Abstract:
Organic field effect transistors (OFETs) have been applied to a number of sensing and actuation systems which can take advantage of their low thermal budget and mechanical flexibility. Characterization of OFETs has been, however, a controversial topic because the conduction and transport models are unlike other well understood systems with accepted transport and device models. We have developed a family of techniques for the analysis and characterization of OFETs using a combination of optical and electrical probe techniques grounded in the physics underlying transport in organic semiconductor thin films. These techniques provide unique insights into device performance and also indicate ways to better fabricate and drive devices in practical circuits. These probes include the use of quasi-static charge metrology techniques, spatially and spectrally resolved photocurrent analysis, and the analysis of switching noise in OFET circuits. The physical basis behind these tools, as well as some analytical results which they have yielded in practical devices, circuits, and deliberately doped systems will be presented. The application of OFETs to a number of sensor systems including additive photodetectors and strain sensing will also be presented, along with what these analytical strategies can tell us about better ways to fabricate and drive these devices.
5
Oct '09
Boston University
Luca Dal Negro
Light in deterministic aperiodic media
19
Oct '09
City College of CUNY
Carlos Meriles
Larmor magnetometry as a path to spin sensing at the nanoscale
22
Oct '09
University of Waterloo
Zoya Leonenko
Scanning probe microscopy in biomedical research
Download PDF @4:00 pm
Abstract:
Scanning Probe Microscopy is a big and growing family of many nanoscale characterization methods which are widely used in many areas including physics, chemistry, biology, biomedical and nano-technology. One of them, Atomic force microscopy (AFM) is a well-known scanning probe microscopy technique which allows imaging and nanomanipulation on a single molecule and nm scale. In this talk I will give introduction to several scanning probe microscopy methods, and focus on Atomic Force Microscopy (AFM), and Kelvin Probe Force Microscopy (KPFM), which we use in my laboratory to investigate complex structure and function of lipid films and lipid-protein interactions. Molecular arrangement of lipids and proteins in monolayer or membrane gives rise to complex film morphology as well as an electrical surface potential or non-uniform charge distribution, which rule many biological processes and diseases. I will give a review of current research projects in my laboratory, such as a) study of structure and function of lung surfactant and how these are affected by cholesterol; b) investigation of amyloid fibril formation which is associated with more than 20 neurodegenerative diseases for which no cure is currently available, for example Alzheimer's and Parkinson's to name a few. We focus on elucidating the role of lipid membrane surfaces in amyloid fibril formation.
26
Oct '09
City College of CUNY
Myriam Sarachik
Molecular magnets: spin reversal by quantum tunneling and avalanches
Abstract:
Molecular Magnets, sometimes referred to as single molecule magnets, are organic materials that contain a very large (Avogadro's) number of molecules that are (nearly) identical nanomagnets, providing ideal laboratories for the study of nanoscale magnetic phenomena. With molecular clusters of large total spin 10, Mn12-acetate and Fe-8 are borderline between classical and quantum magnetism. They are magnetically bistable at low temperatures, they exhibit ``macroscopic quantum tunneling'' between up and down spin orientations, and quantum interference between tunneling paths. Interest in these materials has grown dramatically in the last several years, owing to their possible use for high density storage of information, as well as the possibility that some member of this family of materials could provide qubits for quantum computation.
Following an introductory description of the major features that characterize these interesting materials, this talk will focus on the processes by which the large (S=10) magnetization vector of individual molecules in a Mn12-acetate crystal reverse direction - by classical over-the-barrier spin reversal, quantum tunneling (under-the-barrier), or as a magnetic avalanche propagating at subsonic speed through the crystal in the form a narrow front.
2
Nov '09
Columbia University
Ildar Salakhutdinov
Plasmonics optical circuitry for biomedical applications
9
Nov '09
Wesleyan University
Tsampikos Kottos
Optical structures with anti-linear symmetries: taming absorbtion with amplification
16
Nov '09
Lehman College of CUNY
Christopher Gerry
Quantum sensing and metrology
23
Nov '09
Yale University
A. Douglas Stone
What is a laser, and do we really understand them after forty-five years
Abstract:
Recently invented micro and nano lasers have challenged our understanding of lasers and revealed the absence of a predictive theory. Perhaps most surprising is the existence of random lasers, based on multiple scattering between nanoparticles in the presence of gain. While these lasers behave in most respects like conventional lasers in terms of their emission properties, they have no mirrors or cavity of any kind. and the linear scattering spectrum reveals no long-lived resonances to support lasing. In the absence of long-lived cavity resonances conventional semiclassical laser theory, which assumes such resonances evolve into the laser modes, has no starting point. Recently, we have developed a modern formulation of semiclassical laser theory, which elucidates the nature of lasing modes in cavities of arbitrary complexity and arbitrary leakiness, including the case of random lasers. The theory also treats the strong non-linear interaction between lasing modes to all orders and has been shown to agree with full numerical solutions of the lasing equations with no adjustable parameters. Thus we are in position to understand qualitatively complex and random lasers and in the near future produce a truly predictive theory for many lasers of applied and fundamental interest.
14
Dec '09
Columbia University
Tanya Zelevinsky
Ultracold atoms and molecules and in optical lattices