Spring 2007

February 21, 2007

Dr.  Arik Yochelis
Department of Cardiology,
David Geffen School of Medicine, UCLA

Title: Intertwined by symmetry: spatially localized oscillations in nature

Abstract: We have studied the origin and the properties of a new type of spatially localized oscillations we refer to as standard and reciprocal oscillons. The latter take the form of holes in an oscillating background, and have been observed in both vibrating granular media and optically forced chemical reactions but their origin has remained unclear. Spatially localized structures have been the source of fascination ever since the discovery of solitons. Like solitons the oscillations we study exhibit properties that are independent of the detailed description of the system. However, in contrast to solitons they are dissipative structures, and (generally) do not propagate. Our study is motivated by experimental observations but utilizes a general theoretical framework. We show that the presence of reciprocal oscillons is intimately related to the existence of interfaces with both monotonic and nonmonotonic profiles. We also show that the branches of oscillons and interfaces are intertwined in general, and ultimately collapse together at a single point in the parameter plane. In a neighborhood of this point a large but finite number of coexisting stable localized states of either type is present. Our results not only agree qualitatively with the experiments but the basic scenario described in our research also suggests their relevance to other media such as reaction-diffusion systems.



Feburary 28, 2007

CANCELLED



March 7, 2007




March 14, 2007

Dr. Yu Huang
Materials Science
UCLA

Title: Nanoscale Electronics and Optoelectronics

Abstract: A bottom-up approach, where functional systems are assembled from chemically synthesized, well-defined nanoscale building-blocks, has the potential to go far beyond the limits of top-down technology by defining key nanometer scale metrics through synthesis and subsequent assembly ¾ not by lithography. One-dimensional nanostructures represent the smallest dimension structure that can efficiently transport electrical carriers, and can play an important role as both interconnect and functional device elements in integrated nanosystems. This talk will focus on semiconductor nanowire building blocks. Semiconductor nanowires can be synthesized with precisely controlled chemical composition and physical dimension. They generally demonstrate excellent electronic and optical properties that are comparable or superior to their bulk counterparts. Various hierarchical assembly methods have been developed to organize nanowire building blocks into functional devices and complex architectures. In particular, electrical fields and microfluidic flows have both been explored for the assembly of nanowires with controlled spatial location and directionality, which enables creation of a variety of conceptually new nanoscale electronic and photonic devices. This talk will cover a few examples of nanoscale electronic devices such as crossed nanowire p-n diode, crossed nanowire field-effect transistor (FET) and integrated logic circuits, as well as optoelectronics devices including light emitting diodes (LED), multi-color LED arrays, and integrated LED-FET.

Bio: Dr. Huang is currently an assistant professor at DMSE at UCLA. She received her M.A. and Ph.D degree from Harvard University, and B.S. degree from the University of Science and Technology of China. Dr. Huang is recognized for her work in the field of nanoscale science and technology. She has made profound contribution to the field of nanoelectronics with her work in bottom-up assembly of nanoscale electronic and optical devices and circuits using nanowires as building blocks. The honors Dr. Huang has received include Nantech Brief Nano 50 Award (2006), IUPAC Young Chemist Award (2004), MIT Technology Review TR100 (top-100 young innovator) award (2003), grant prize recipient of the Collegiate Inventors Competition (2002) and the Materials Research Society Graduate Student Award (2002)



March 21, 2007

Dr. Roberto Car
Department of Chemistry
Princeton University

Title: Suprises of water: results from ab-initio molecular dynamics

Abstract: Water is the most important liquid on earth. Its special properties derive from the underlying hydrogen bond network. In this talk I will focus on some aspects that contribute to make water the essential liquid in chemistry and biology, namely its dielectric properties,   hydrophobic-hydrophilic effects,  and the role that these effects play at the interface between water and a hydrophobic substance. The discussion will be based on recent results from ab-initio molecular dynamics simulations, an approach that derives the properties of a liquid from those of its basic consituents, i.e. electrons and nuclei.



March 28, 2007

Dr. Na Deng
CSUN Post Doctoral Fellow

Title: High-Resolution Studies of Solar Active Regions

Abstract: Solar eruptions can impact the Earth environment. Most of them occur in solar active regions. Studying morphology and dynamics of active regions is important for understanding the ultimate origin of solar eruptions. High-resolution observations are necessary to reveal the fundamental structure and dynamics in sunspots. The methods for ground-based high-resolution solar observations, such as adaptive optics and speckle masking imaging, will be briefly introduced. With high quality data, the morphology and flow field, in a simple decaying sunspot and in flare producing complex sunspots, are studied and will be presented in this talk.



April 11, 2007

Dr. Manuel de Llano
Physics Instituto de Investigaciones en Materiales, Mexico

Title: Generalized Bose-Einstein Condensation and Superconductvity

Astract: By acknowledging the vital importance of two-hole Cooper pairs (CPs) in addition to the usual two-electron ones in a strongly-interacting many-electron system, the concept of CPs was re-examined with striking conclusions: namely, gapped and linearly-dispersive CP resonances with a finite lifetime---but only if the ideal-gas Fermi "sea" is replaced by a BCS-correlated unperturbed ground-state. Based on this new zeroeth-order state, Bose-Einstein condensation (BEC) theory is being generalized to include not boson-boson interactions (also absent in BCS theory) but rather boson-fermion interaction vertices reminiscent of the Fröhlich electron-phonon interaction in metals. But instead of phonons, the bosons in the generalized BEC (GBEC) theory are now both particle and hole CPs. In contrast to BCS theory, the GBEC Hamiltonian can be diagonalized exactly. Each kind of CP is responsible for only half the condensation energy. The GBEC theory contains all the old well-known statistical theories as special cases, including the so-called BCS-Bose "crossover" picture. A BCS condensate appears to be a very special instance of a GBE condensate. With feasible Cooper/BCS model interaction parameter values, it yields transition temperatures (including room-temperature superconductivity) substantially higher than a BCS ceiling of around 45K, without relying on non-phonon dynamics involving excitons, plasmons, magnons or otherwise purely-electronic mechanisms.



April 18, 2007

Dr. Jack Thomas
University of Rochester
University Distinguished Speaker

Title: The Intriguing Structure of a Sunspot

Abstract: Sunspots, which have fascinated astronomers since the time of Galileo, mark the locations where strong magnetic fields emerge through the surface of the Sun. They provide the ideal proving ground for the theory of magnetohydrodynamics under astrophysical conditions, for nowhere else in astrophysics is the theory confronted with such a wealth of detailed observations. Recent advances in high-resolution observations have provided us with a new picture of the magnetic structure of a sunspot, especially its outer part (the filamentary penumbra) which involves two components with different magnetic field inclinations. The darker component, with a more nearly horizontal magnetic field, contains `returning' magnetic flux tubes that dive back down below the solar surface near the outer edge of the penumbra. The submergence of these flux tubes, which is surprising in view of their inherent magnetic buoyancy, can be understood to be a consequence of downward pumping of the magnetic flux by turbulent granular convection in the `moat' surrounding the sunspot. The effectiveness of this flux-pumping process is demonstrated in three-dimensional numerical simulations of fully compressible thermal convection. The flux-pumping mechanism turns out to be an important key to understanding not only the curious magnetic structure of the penumbra but also its formation and maintenance.

Additional Information



April 24, 2007

Gordon Emslie
Oklahoma State University
Harlow Shapley Visiting Lectureship

Title: Hard X-Rays Imaging Spectroscopy of Solar Flares

Abstract: Solar flares are the most powerful explosions in the solar system, and they accelerate copious quantities of charged particles, both electrons and ions. Imaging spectroscopy of the hard X-ray emission produced by accelerated electrons provides information on the variation of the electron spectrum throughout the source, and hence on the characteristics of the processes that affect the electrons as they are accelerated and as they interact with the solar atmosphere. The Ramaty High Energy Solar Spectroscopic Imager (RHESSI) instrument, launched in 2002, provides hard X-ray spectra with energy resolution down to 1 keV and spatial resolution down to a few arc seconds. In this seminar I will review the results of various attempts to extract information on the source electron spectra from the RHESSI data, and I will also discuss the first results from an exciting new procedure for imaging spectroscopy analysis, which is optimized for the manner in which imaging information is encoded by RHESSI.



April 25, 2007

Gordon Emslie
Oklahoma State University
Harlow Shapley Visiting Lectureship

Title: Spinning Pliers, The Chaotic Obliquity of Mars, and the Existence of Extraterrestrial Life

Venue: USU Thousand Oaks Room

Abstract: The basic principles of rigid body rotation have been known for over two hundred years; yet the resulting motion is sometimes quite surprising. Videotape from a Space Shuttle mission shows this quite vividly: while the rotation of an astronaut is straightforward (like a spinning ice skater), the motion of a set of pliers is quite fascinating and totally unexpected. I will discuss how these surprising motions come about.

The rotation of planets offers equally surprising behaviors. As a striking example, the tilt angle of Mars undergoes dramatic transitions, so that the seasonal variation of temperature on the Martian surface is quite different now than in the distant past.

Why has the Earth not suffered such dramatic changes in tilt? The surprising answer to this question means that we may have to drastically reduce our estimates for the number of habitable planets in the Galaxy and perhaps explains why a recently-completed five year search, in ten million radio channels, produced not a single example of a signal from our galaxy that is attributable to extraterrestrial life.

Additional Information



May 2, 2007

Ed Rhodes
University of Southern California

Title: Predicting Solar Disturbances by Monitoring the Sun from the Moon

Abstract: The U. S. plans to return astronauts to the lunar surface beginning in 2018. The protection of these astronauts from solar hazards will require constant monitoring of the Sun. Since the solar fares, energetic particle streams, and coronal mass ejections which may be harmful to these astronauts are now thought to be triggered by the motions of magnetic field lines within the shallow convective shear layer which exists just below the solar surface, the constant monitoring of these motions will be essential. As one example, the intensity of solar areas in active regions appears to be correlated to the vorticity beneath these active regions. Monitoring of the sub-surface vorticity using the techniques of local helioseismology will require the continuous acquisition of time series of solar Dopplergrams similar to those which will be obtained by the Helioseismic and Magnetic Imager Experiment which will be launched on NASA's Solar Dynamics Observatory (SDO) Mission in mid-2008. Unfortunately, the SDO Mission is not expected to be operational during any of the manned lunar operations.

In this talk I will describe how the emplacement of a small, solar-pointed instrument package near the top of one of the so-called Peaks of Eternal Sunlight" at one of the lunar poles by the astronauts will provide such continuous solar monitoring. I will describe how the Dopplergrams obtained with such an instrument will be converted into maps of the Solar Subsurface Weather. The resulting subsurface flow maps will then be converted into maps of the subsurface vorticity. These maps will be combined with measurements of the solar magnetic field and with measurements of the solar EUV irradiance to predict potentially-harmful disturbances in near-real-time.



May 9, 2007

Prof. Kieron Burke
University of California, Irvine

Title: Density functional theory: The good, the bad, and the ugly

Abstract: Density functional theory has become very popular for solving problems in solid state physics, chemistry, materials science, and other fields. I will explain how and why it works, and also discuss some limitations and abuses.



May 15, 2007

Dr. Sergey Ustyugov Keldysh
Institute of Applied Mathematics, Moscow, Russia    

Title: Three dimensional numerical simulation of local solar  supergranulation with realistic physics

Abstract: Three-dimensional large eddy simulations of solar surface convection using realistic model physics are conducted. The thermal structure of convective motions into the upper radiative layers of the photosphere, the range of convection cell sizes, and the penetration depths of convection are investigated. A portion of the solar photosphere and the upper layers of the convection zone, a region extending 60×60 Mm horizontally from 0 Mm down to 20 Mm below the visible surface, is considered. The realistic initial model of the Sun with an equation of state and opacities of stellar matter are used. The equations of fully compressible radiation magnetohydrodynamics with dynamical viscosity and gravity are solved. For numerical solution of equations were applied:  1) a high order conservative TVD scheme for the hydrodynamics,2) the diffusion approximation for the radiative transfer,3) dynamical viscosity from subgrid scale modeling. The simulations are conducted on a uniform horizontal grid of 600×600, with 168 nonuniformly spaced vertical grid points, on 144 processors with distributed memory multiprocessors on supercomputer MBC-1500 in the Computational Centre of the Russian Academy of Sciences. The study of the properties of solar acoustic waves ( p-modes,high l) is conducted.

May 16, 2007

Dr. Paul von Allmen
JPL