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SUNMONTUEWEDTHUFRISAT
Conferences, Lectures, & Seminars
Events for January
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Generalized ACE codes
Wed, Jan 12, 2005 @ 03:30 PM - 04:30 PM
Ming Hsieh Department of Electrical and Computer Engineering
Conferences, Lectures, & Seminars
SPEAKER: Mr. Aditya Ramamoorthy, EE Dept, UCLAABSTRACT: Low-Density Parity-Check Codes have been the subject of intense research lately because of their linear decoding complexity and near capacity achieving performance. Recent results show that LDPC codes drawn at random from irregular degree distribution ensembles can have significantly better performance asymptotically than regular LDPC codes and in fact provably achieve capacity over the binary erasure channel.At finite block lengths however one can achieve much better performance over randomly chosen codes by a careful construction of the parity check matrix. In this talk I shall explain the Approximate Cycle EMD (ACE) algorithm (Tian et al.) for the construction of LDPC codes for a given block length and degree distribution and discuss a generalization of their approach. I shall discuss the analysis of the expected stopping set spectrum of generalized ACE constrained ensembles which shows their improved performance over the binary erasure channel and the expansion properties of these codes that justifies their improved performance over the AWGN channel. Techniques for improving the performance even further at short block lengths will also be presented.This is joint work with Prof. Richard Wesel.BIO: Aditya Ramamoorthy is a Ph.D. candidate in the Electrical Engineering Department at the University of California, Los Angeles. He received his B. Tech. from the Indian Institute of Technology, Delhi in 1999 and his M.S. from UCLA in 2002. From 1999-2001 he was working as a systems engineer at Biomorphic VLSI Inc. In the summer of 2004 he was an intern at Microsoft Research working on network coding.His research interests include coding theory (in particular LDPC code design and analysis) and network coding.Host: Dr. Keith M. Chugg, x.07294, chugg@usc.edu
Location: Hughes Aircraft Electrical Engineering Center (EEB) - -248
Audiences: Everyone Is Invited
Contact: Mayumi Thrasher
This event is open to all eligible individuals. USC Viterbi operates all of its activities consistent with the University's Notice of Non-Discrimination. Eligibility is not determined based on race, sex, ethnicity, sexual orientation, or any other prohibited factor. -
DISTINGUISHED LECTURER SERIES - DNA: Not Merely the Secret of Life, Prof. Nadrian Seeman, NYU
Thu, Jan 20, 2005 @ 03:00 PM - 04:00 PM
Ming Hsieh Department of Electrical and Computer Engineering
Conferences, Lectures, & Seminars
Abstract:========Our laboratory works in the area of structural DNA nanotechnology. We use the concept of reciprocal exchange between DNA double helices to produce branched DNA motifs, like Holliday junctions, or related structures, such as double crossover (DX), triple crossover (TX), paranemic crossover (PX) and DNA parallelogram motifs. We combine DNA motifs, using sticky-ended cohesion, to produce specific structures. The key strength of sticky-ended cohesion is that it produces predictable adhesion combined with known structure. We have constructed DNA stick-polyhedra, whose edges are double helices, and whose vertices are the branch points of DNA branched junctions. These include a cube, a truncated octahedron, and an irregular graph. Nanorobotics are key to the success of nanotechnology. We have used two DX molecules to construct a DNA nanomechanical device by linking them with a segment that can be switched between left-handed Z-DNA with right-handed B-DNA. PX DNA has been used to produce a robust sequence-dependent device that changes states by varied hybridization topology. The sequence-dependent nature of this device means that a variety of them attached to a motif can all be addressed individually. Recently, we have used this device to make a machine that does chemical translation. A central goal of DNA nanotechnology is the self-assembly of periodic matter. We have constructed micron-sized 2-dimensional DNA arrays from DX, TX, two kinds of parallelogram motifs. We can produce specific designed patterns visible in the AFM from DX and TX molecules. We can change the patterns by changing the components and by modification after assembly. Recently, we have used new motifs to produce honeycomb-shaped arrays. The key structural challenge in the area is the extension of the 2D results obtained so far to 3D systems with a high degree of ordering. Crystals with dimensions as large as a millimeter, ordered to 10 Å resolution (as determined by X-ray diffraction) have been produced. Ultimately, we expect to be able to produce high resolution crystals of DNA host lattices with heterologous guests, leading to well-ordered bio-macromolecular systems amenable to diffraction analysis. Other challenges are to incorporate DNA nanomechanical devices in periodic and aperiodic lattices and to use the lattices to organize nanoelectronic components, such as metallic nanoparticles or carbon nanotubes.Bio:===Nadrian C. Seeman was born in Chicago in 1945. Following a BS in biochemistry from the University of Chicago, he received his Ph.D. in biological crystallography from the University of Pittsburgh in 1970. His postdoctoral training, at Columbia and MIT, emphasized nucleic acid crystallography. He obtained his first independent position at SUNY/Albany, where his frustrations with the macromolecular crystallization experiment and his awareness of the fatal series--no crystals, no crystallography, no crystallographer--led him to the campus pub one day in the fall of 1980. There, he realized that the similarity between 6-arm DNA branched junctions and the flying fish in the periodic array of Escher's 'Depth' might lead to a rational approach to the organization of matter on the nanometer scale, particularly crystallization. Ever since, he has been trying to implement this approach and its spin-offs, such as nanorobotics and the organization of nanoelectronics; since 1988 he has worked at New York University. When told in the mid-1980's that he was doing nanotechnology, his response was similar to that of M. Jourdain, the title character of Moliere's Bourgeois Gentilehomme, who was delighted to discover that he had been speaking prose all his life. Further information is available at http://seemanlab4.chem.nyu.edu.Host: Prof. Urbashi Mitra, x04667 ***A reception will follow the seminar at 4:00p.m.
Location: Ethel Percy Andrus Gerontology Center (GER) - ontology Auditorium (GER-124)
Audiences: Everyone Is Invited
Contact: Rosine Sarafian
This event is open to all eligible individuals. USC Viterbi operates all of its activities consistent with the University's Notice of Non-Discrimination. Eligibility is not determined based on race, sex, ethnicity, sexual orientation, or any other prohibited factor.
