FALL SEMINAR 2008-2009

(Organized Professor Raj)

September 26	“Computing with Things Small, Wet, and Random: Design Automation for Nanoscale Technologies and Biological Processes”
	Prof. Marc Riedel University of Minnesota
	Abstract:
	This talk will discuss techniques for analyzing and synthesizing circuits and biological systems that are characterized by uncertainty and randomness in their components, connectivity, and execution. We adopt a novel view of computation: instead of transforming definite inputs into definite outputs, circuits and biological systems transform probability values into probability values. The computation is random at the level of bits or protein-protein reactions; nonetheless, in the aggregate, it becomes exact and robust, since the accuracy depends only on the statistical distributions of the quantities. The methodologyprovides a design strategy for coping with the noise and the glitches that occur as circuit components are scaled down in size to nanometers. In synthetic biology, it allows us to design biochemical pathways with precise and programmable functionality. The talk will present novel circuit constructs, including feedback architectures. Also, it will describe computer-aided design tools that we are developing for biology, including a biochemical "toolkit" consisting of modules for standard arithmetic operations (analogous to those performed by an arithmetic-logic unit in a microprocessor system) as well as regulatory functions (analogous to those performed by control circuitry).
	Bio:
	Marc Riedel has been an Assistant Professor of Electrical and Computer Engineering at the University of Minnesota since 2006. He is also a member of the Graduate Faculty in Biomedical Informatics and Computational Biology. He received his Ph.D. and his M.Sc. in Electrical Engineering at Caltech and his B.Eng. in Electrical Engineering with a Minor in Mathematics at McGill University. His Ph.D. dissertation titled "Cyclic Combinational Circuits" received the Charles H. Wilts Prize for the best doctoral research in Electrical Engineering at Caltech. His paper "The Synthesis of Cyclic Combinational Circuits" received the Best Paper Award at the Design Automation Conference. He has held positions at Marconi Canada, CAE Electronics, Toshiba, and Fujitsu Research Labs.
October 3	“Tunable negative index metamaterials and devices”
	Dr. Alexandre M Bratkovski HP Lab
	Abstract:
	Recently, metamaterials with negative index of refraction have been demonstrated for microwave electromagnetic (EM) radiation. It has been anticipated in 1950-60s by Pafomov and Veselago that negative refraction should occur in homogeneous media with simultaneously negative dielectric permittivity and magnetic permeability, ?<0, ?<0. meaning the medium supports ‘backward waves’. It has been speculated by Pendry (2000) that the ideal Veselago lens can produce and image beyond the limits of geometrical optics, and may open up new possibilities in integrated photonics, imaging, and sensors. We explore these possibilities theoretically and experimentally. Performance of NIM lenses is hindered by losses and imperfect surfaces, so that one has to demonstrate the feasibility of these devices working at optical frequencies, or find ways to mitigate them. We have designed the metamaterial by means of FDTD modeling, which is a stack of metallic films with periodic hole arrays separated by dielectric layers (so-called “fishnet”, FN) to work at IR wavelengths ?=1.5-1.7 ?m, and fabricated a few samples by nanoimprint lithography. The FN transmission and reflectance characteristics showed unambiguously that the FN supports the “backward” waves and have overall negative index of refraction at IR frequencies. We have achieved very fast optical modulation of the effective refractive properties of a “fishnet” metamaterial with a Ag/Si/Ag heterostructure in the near-IR range and the associated fast dynamics was studied by pump-probe method. Photo excitation of the amorphous Silayer at visible wavelength and corresponding modification of its optical parameters is found to be responsible for the observed modulation of negative refractive index in near-IR (with the fast ~1ps relaxation time followed by ~50ps tail). New very interesting possibility is opened up by exploring the binary mixtures of e.g. lossy metallic nanostructure with gain medium, like e.g. PbSe nanoparticles, that may help to overcome loss in a particular frequency window where the refractive index remains /negative/. We have showed that a binary mixture of quantum dots exhibiting gain with silver nanorods makes a lossless negative operation for realistic material structures and parameters feasible. We also explore excellent possibilities provided by plasmonic nanostructures for sensing, in particular Surface Enhanced Raman Scattering (SERS), where we design plasmonic field enhancers as part of high-performance systems capable of one-molecule detection. Some still controversial aspects of SERS will be touched upon.
	Bio:
	Alexander Bratkovsky received his MS degree from Moscow Engineering Physics Institute and PhD from Kurchatov Institute for Atomic Energy in 1979 and 1982, respectively, all in Theoretical Physics. He worked for Kurchatov Institute in Moscow, for Cambridge University and Oxford University in the UK, and joined HP Laboratories, USA, in 1996. His research interests span spintronics, ferroics, strongly correlated systems, metamaterials, photonics, and sensors. He has authored over 130 papers in leading technical journals and elected a Fellow and Division Vice-chair of American Physical Society.
October 10	“Digitally Assisted Data Converters and Sensor Interface Circuits”
	Prof. Boris Murmann Stanford University
	Abstract:
	Low-power data conversion has evolved as a key requirement in manymodern electronic devices. The research presented in the first part ofthis talk targets a new class of low power "digitally assisted" ADCsand DACs. These converters are based on minimalistic, but powerefficient analog sub-circuits and use digital processing forperformance recovery and/or enhancement. The second part of thispresentation outlines our activities in mixed-signal circuit designfor sensor interfaces. Specific examples include bio-medical sensors,MEMS inertial sensors and applications in large-area organic thin-filmelectronics.
	Bio:
	Boris Murmann is an Assistant Professor in the Department of Electrical Engineering, Stanford, CA. He received the Ph.D. degree in electrical engineering from the University of California at Berkeley in 2003. From 1994 to 1997, he was with Neutron Microlektronics, Germany, where he developed low-power and smart-power ASICs in automotive CMOS technology. Dr. Murmann's research interests are in the area of mixed-signal integrated circuit design, with special emphasis on data converters and sensor interfaces. He currently serves as a member of the International Solid-State-Circuits Conference (ISSCC) program committee.
October 17	“Cooperative networks and the growth of wireless infrastructures”
	Prof. Anna Scaglione University of California, Davis
	Abstract:
	Cellular networks and packet switched wireless networks have had remarkable success stories. Today, consumers and Internet providers are hungry for high-speed wireless data services. Wireless communication devices are also becoming omnipresent in all sorts of embedded systems. In spite of the considerably lower cost of the hardware, the cost of the support infrastructure continues to grow. Is it possible to reverse this trend? The new frontier of wireless networking is an infrastructure question. The tutorial will present the basic challenges in scaling wireless communication networks based on the multi-hop model and discuss how using new cooperative models for the transmission of the devices can provide new avenues to overcome such limitations.
	Bio:
	Anna Scaglione received her PhD from the University of Rome "La Sapienza", Rome, Italy in 1999. She was Postdoctoral Research Affiliate at University of Minnesota (Minneapolis, MN) in 1999-2000. She recently joined the Electrical and Computer Engineering Department at UC Davis in July 2008 as Associate Professor. Prior to moving to UC Davis she was on the faculty at Cornell University (Ithaca, NY) where she joined in 2001 and was promoted to Associate Professor in 2006. Her first academic appointment as assistant professor was in 2000, at the University of New Mexico (Albuquerque, NM). She was awarded and is co-recipient of some awards: the 2000 IEEE Signal Processing Transactions Best Paper Award; the NSF Career Award in 2002, the Ellersick Best Paper Award (MILCOM 2005), the 2005 Best paper for Young Authors of the Taiwan IEEE Comsoc/Information theory section. She has served the IEEE Signal Processing and Communication societies in several capacities over the years, she has been Associate Editor for the IEEE Transactions on Wireless Communications (2002 to 2005), Co-Guest Editor of the Communication Magazine Special Issue on Power Line Communications (“Broadband is Power: Internet Access through the Power Line Networks”, May 2003). She has been member of the IEEE Signal Processing for Communication Technical Committee since 2004 and of the IEEE Power Line Communication committee from 2005 to 2006. She was co-general Chair of the VI IEEE Signal Processing Advances in Wireless Communications workshop, held in June 2005 in New York City.
October 24
	Dr. John Camagna Akros Silicon
October 31
	Jared Zerbe Engineering Director Rambus Inc.
November 7
	Prof. Brian Otis University of Washington
	Abstract:
	Emerging applications of wireless sensors require currently-unavailable levels of system integration, functionality, and lifetime. Challenges include the integration of a robust low power wireless link, sensor signal processing, and system miniaturization. We'll discuss circuit design techniques utilizing micro-electromechanical (MEMS) devices to reduce the power consumption and footprint of wireless transceivers. Recent work in low power analog sensor interfaces will be presented. Finally, I'll describe a few applications in the medical community that will benefit from these advancements.
	Bio:
	Brian Otis received the B.S. degree in electrical engineering from the University of Washington and the M.S. and Ph.D. degrees from the University of California at Berkeley. He joined the faculty of the University of Washington as Assistant Professor of Electrical Engineering in August 2005, where he directs the Wireless Sensing Lab. His research interests include ultra-low integrated circuit design for enabling previously impossible sensing and communication paradigms. He has previously held positions at Intel Corporation and Agilent Technologies. Dr. Otis is an Associate Editor of the IEEE Transactions on Circuits and Systems Part II. He was the recipient of the 2003 U.C. Berkeley Seven Rosen Funds award for innovation and was co-recipient of the 2002 ISSCC Jack Raper Award for Outstanding Technology Directions Paper.
November 14
	Prof. David Tse University of California at Berkeley
November 21
	Prof. Ian Blake University of British Columbia
	Abstract:
	The discrete logarithm problem has played a central role in the development of cryptography. Froma simple example of a one-way function in the multiplicativegroup of a finite field, in the paper that defined publickey cryptography over three decades ago, through itsdevelopment in a variety of algebraic structures,it is now part of numerous international security standards. The problem has evolved in many waysand generated a large number of research directionsthat are ongoing today. This talk will give anoverview of many of these developments. It is intended for a general audience.
	Bio:
	Ian F. Blake received his undergraduate education at Queen's University in Kingston, Ontario and his Ph.D. at Princeton University in New Jersey. From 1967 to 1969 he was a Research Associate with the Jet Propulsion Laboratories in Pasadena, California. From 1969 to 1996 he was with the Department of Electrical and Computer Engineering at the University of Waterloo, in Waterloo, Ontario where he was Chairman from 1978 to 1984 and Director of the Institute of Computer Research from 1990 to 1994. He was with HP Labs in Palo Alto, CAfrom 1996 t0 1999 and the Department of Electrical and Computer Engineering at the University of Torontofrom 2000 to 2007. His research interests are in the areas of cryptography, algebraic coding theory, digital communications and spread spectrum systems. He is a Fellow of the IEEE, the CAE and RSC. He was awarded an IEEE Millennium Medal.
December 5
	Prof. Urbashi Mitra USC
April 2	“Organic Semiconductor Devices for Bioelectronics”
	Daniel Bernards, Postdoctoral Scholar University of California, San Francisco
	Abstract:
	Since the discovery of highly conductive polymers, a wide range of polymeric and small molecule semiconductors have been developed for devices including transistors, photovoltaics and light emitting diodes. Organic semiconductors have many attractive properties, such as low cost, ease of processing, synthetically tunable properties, compatibility with a variety of substrates, and covalent integration of chemical and biological functionalities. Sensors have recently emerged as a promising application of organic electronics since they benefit from the advantages of organics (e.g. processing and cost) and are not significantly impacted by the usual drawbacks (e.g. performance and lifetime). Furthermore, increased development of biocompatible organic semiconductors and devices functional in aqueous environments make interfacing organic electronics with biology an attractive application. Distinct from the majority of contemporary electronics, organic semiconductors have the unique ability to sustain mixed conduction of ionic and electronic charge at room temperature. In addition to conventional devices, a subset of organic electronic devices exhibit novel properties due to mixed conduction, such as electrically switchable surface properties, pumping of ions, and release of therapeutic molecules. A prime example of a mixed conductor device is the organic electrochemical transistor, which is analogous to a field-effect transistor with the dielectric replaced by an ionically conducting electrolyte. While its current-voltage characteristics are similar to a depletion mode transistor, these devices are electrochemical in nature unlike the electrostatic behavior of field-effect transistors. Given mixed conduction in these devices, it is natural to incorporate electrochemical or ionic elements for sensing: two examples are enzyme-based sensing and ion channel-based sensing. For enzymatic sensors, sensing is mediated by enzymatic degradation of an analyte (e.g. glucose oxidase for sensing glucose). With appropriate enzyme selection, this class of devices is capable of sensing a variety of analytes over a wide range of concentrations. Combining analytical models from electrochemistry and device physics, it is possible to model these enzymatic sensors and consequently optimize device design. A second sensor type utilizes lipid bilayers and ion channels, where device response is dictated by the behavior of the incorporated ion channels. This sensing mechanism has tremendous potential and is limited only by the stability of the lipid bilayer and the type of ion channels utilized. Interfacing organic electronics and biology has been established through biosensor development and is at the forefront of an effort to integrate electronics and biology. Future applications of organic semiconductors in bioelectronics, from fundamental tools to advanced therapeutic devices, will be discussed.
	Bio:
	Daniel Bernards is currently a postdoctoral scholar at the University of California at San Francisco working in the research group of Tejal Desai with projects focused on nanostructured materials for drug delivery. He did his doctoral work in the Department of Materials Science and Engineering at Cornell University in the research group of George Malliaras. His graduate research focused on the interplay between ionic and electronic charge in a variety of organic semiconductor devices, including light emitting devices, photovoltaics, electrochemical transistors, and biosensors. He is the recipient of a National Defense Science and Engineering Graduate Fellowship.
April 14	“Exhaustive Weight Spectrum Analysis of LDPC Codes with Results for some well known Codes”
	Professor Martin Tomlinson Fixed and Mobile Communications Research University of Plymouth, UK
	Abstract:
	The indicative performance of an LDPC code may be determined from exhaustive analysis of the low weight spectral terms of the code’s stopping sets which by definition includes the low weight codewords. In a landmark paper in 2007, Rosnes and Ytrehus showed that exhaustive, low weight stopping set analysis of codes whose parity check matrix is sparse is feasible using a bounded tree search over the length of the code with no distinction between information and parity bits. For an (n, k) code the potential total search space is of size 2n but a good choice of bound dramatically reduces this search space to a practical size. Indeed the choice of bound is critical to the success of the algorithm. It is shown that an improved algorithm can be obtained if the bounded tree search is applied to a set of k information bits since the potential total search space is initially reduced to size 2k. Since such a restriction will only find codewords and not all stopping sets a class of bits is defined as unsolved parity bits and these are also searched as appended bits in order to find all low weight stopping sets. Weight spectrum results are presented for commonly used WiMax LDPC codes plus some other well known LDPC codes.