UNIVERSITY OF CALIFORNIA - DAVIS RESEARCH

Andre Knoesen

Tonya Kuhl

Marjorie L. Longo

Professor, Department of Electrical and Computer Engineering, University of California, Davis, CA (b. 1958). BSEE, 1980, University of Pretoria, South Africa; M.S., 1982, Georgia Institute of Technology; Ph.D. 1987, Georgia Institute of Technology. Professional Memberships: Fellow of the Optical Society of America, Senior Member of IEEE. Phone: (530) 752-8023, Fax: (530) 752-8428, email: knoesen@ece. ucdavis.edu

Professor Knoesen investigates the electronic and optical properties of thin polymer films for applications relevant to electrical engineering. The focus of his research within CPIMA is the development of optical and electrical characterization techniques for polymers and polymer interfaces. Other research activities over the past few years include electro-optic polymer films, the optimization and application of such materials towards specific highspeed applications, for example, high speed opto-electronics components such as large bandwidth modulators used in communication systems and phase-array antennas. The characterization methods available in his laboratory include parametric nonlinear optical techniques, modulated electro-optic techniques, spectroscopic ellipsometry, and microwave electrical measurements (both continuous wave network analyzer measurements and picosecond time domain measurements).

SELECTED PUBLICATIONS

1. Yankelevich, D. R.; Pretre, P.; Knoesen, A.; Taft, G.; Murnane, M. M.; Kapteyn, H. C.; Twieg, R. J. "Molecular Engineering of Polymer Films for Amplitude and Phase Measurements of Ti:Sapphire Femtosecond Pulses". Optics Letters, 21(18), 1487, 1996.
2. Sekkat, Z.; Wood, J.; Knoll, W.; Volksen, W.; Miller, R. D.; Knoesen, A. "Light-induced Orientation in Azo-Polyimide Polymers 325°C Below The Glass Transition Temperature". Journal of the Optical Society of America B, 14(4), 829, 1997.
3. Pretre, P.; Sidick, E.; Wu, L.-M.; Knoesen, A.; Dyer, D.J.; Twieg, R.J. "Optical Dispersion Properties of Tricyanovinlyaniline Polymer Thin Films for Ultrashort Optical Pulse Diagnostics". Organic Thin Films, C.W. Frank, ed., ACS Symposium Series, 695(24), 328, 1998.
4. Pretre, P.; Wu, L. -M.; Knoesen, A.; Swalen, J. D. "Optical Properties of Nonlinear Optical Polymers: A Method of Calculation". Journal of the Optical Society of America B, 15(1), 359, 1998.
5. Pretre, P.; Wu, L. -M.; Hill, R. A.; Knoesen, A. "Characterization of Electro-optic Polymer Films using Decal Deposited Reflection Fabry-Perot Modulators". Journal of the Optical Society of America B, 15(1), 379, 1998.
6. Hamilton, S. A.; Yankelevich, D. R.; Knoesen, A.; Weverka, R. T.; Hill, R. A.; Bjorklund, G. C. "Polymer In-Line Fiber Modulators for Broadband Radio Frequency Optical Links". Journal of the Optical Society of America B, 15(2), 740, 1998.
7. Sekkat, Z.; Pretre, P.; Knoesen, A.; Volksen, W.; Lee, V. Y.; Miller, R. D.; Wood, J.; Knoll, W. "Correlation Between Polymer Architecture and Sub-Glass Transition Temperature Light-Induced Molecular Movement in Azo-Polyimide Polymers: Influence on Linear, Second and Third Order Nonlinear Optical Processes". Journal of the Optical Society of America B, 15(1), 401, 1998.
8. Sekkat, Z.; Knoesen, A.; Lee, V. Y.; Miller, R. D. "Influence of the Polymer Structure on the Achievement of Polar Orientation in High Glass Transition Temperature Nonlinear Optical Polymides by Photo-Assisted Poling". Journal of Polymer Science Part B-Polymer Physics, 12(10), 1669, 1998.
9. Davey, MH; Lee, VY; Wu, LM; Moylan, CR; Volksen, W; Knoesen, A; Miller, RD; Marks, TJ. "Ultrahigh-temperature Polymers for Second-order Nonlinear Optics. Synthesis and Properties of Robust, Processable, Chromophore-embedded Polyimides". Chemistry of Materials, 12 (N6), 1679, 2000.
10. Ge Song; Follonier, S.; Knoesen, A.; Miller, R.D, "Characterization of Thin-film Low-Dielectric Constant Materials in the Microwave Range Using On-wafer Parallel-plate Transmission Lines", IEEE Microwave and Guided Wave Letters,10 (5), 183, 2000.

Tonya Kuhl(top)

Associate Professor, Joe and Essie Smith Professor of Chemical Engineering, NSF Career Award, Department of Chemical Engineering and Materials Science, University of California, Davis, CA; B. A. 1988, Biochemistry-Molecular Biology, University of California, Santa Barbara, CA; Ph.D. 1993, Chemical Engineering, University of California, Santa Barbara, CA; NIH NRSA Postdoctoral Fellow, 1993-1996, Cornell University. Phone: (530) 754-6348, Fax: (530) 752-1031, http://www.chms.ucdavis.edu/research/web/longo/ email mllongo@ucdavis.edu.

In the Longo laboratory, we study the mechanical, barrier, transport, and adsorptive properties of artificial and real cell membranes that lead to macroscopic behaviors of biological membranes. Examples of these behaviors include viral infection, fertilization, action of anesthetics, membrane transport, and drug delivery. The softness of biological interfaces present special experimental problems associated with the fact that the core membrane component, the lipid bilayer, is fluid under physiological conditions. Therefore, we use mild micromanipulation techniques in which the pressure on the membrane can be varied by as little as one millionth of an atmosphere for measuring membrane mechanical properties and adsorption of water soluble species. We softly image the surface of the lipid bilayer using atomic force microscopy and fluorescence microscopy to examine phenomena at a range of length scales from nanometers to micrometers. Finally, for properties that can't be observed experimentally, we develop computer simulations.

SELECTED PUBLICATIONS

1. Zhang, L.; Vidu, R.; Waring, A.; Lehrer, R.; Longo, M. L.; Stroeve, P. "Electrochemical and Surface Properties of Solid-Supported, Mobile Phospholipid Bilayers on a Polyion/Alkylthiol Layer Pair used for Detection of Antimicrobial Peptide Insertion" Langmuir; 18:1318-1331,2002.
   
   
2. Gravano, S.; Borden, M. A.; Werne, T. von;  Doerffler, E.; Salazar, G.; Chen, A.; Kisak, E.; Zasadzinski, J. A.; Patten, T. E.; Longo, M. L. "Block Copolymers of Poly(4-amino methyl styrene)-b-Poly(styrene): Synthesis and Unilamellar Vesicle Formation", Langmuir, 18: 1938-1941, 2002.
   
   
3. Ratto, T. V.; Longo, M. L. "Obstructed Diffusion in Phase-Separated Supported Lipid Bilayers, A Combined AFM and FRAP Approach", Biophysical Journal, 83, 3380, 2002.
   
   
4. Maddox, M. W.; Longo, M. L. "Conformational Partitioning of the Fusion Peptide of HIV-1 gp41 and its Structural Analogs in Bilayer Membranes" Biophysical Journal, 83: 3088-3096, 2002.
   
   
5. Borden, M. A.; Longo, M. L. "Dissolution Behavior of Lipid-Monolayer-Coated, Air-Filled Microbubbles:  Effect of Lipid Hydrophobic Chain Length", Langmuir, 18: 9225, 2002.
   
   
6. Ratto, T. V.; Longo, M. L. "Anomolous Subdiffusion in Heterogeneous Lipid Bilayers"  Special Issue of Langmuir, in press, 2003.