Colloquium Spring 2004
Using science to understand the limits of technology: Nanoscale friction and lubrication in disk drives
Hitachi Global Storage Technologies, San Jose Research Center
While many are trying to break into and harness the world of nanotechnology, the disk drive industry has been shipping nanotechnology for some years now: To store bits at ~10^11 per square inch, modern hard disk drives require a slider to travel at speeds up to 100 mph over a rotating disk while maintaining a spacing of a few nanometers! At such a small separation, new nanoscale friction and lubrication phenomena are encountered that are limiting the industry's ability to further increase the areal density stored in disk drives. In this talk, I will discuss our research at understanding friction and lubrication at the atomic and molecular level and how we are using this understanding to determine the limits (and ways around these limits) for future disk drive technologies. Some of the understanding that we are developing: the friction dissipation mechanisms for molecules sliding over surfaces, thermally excited capillary waves on molecular films, and the physics of shearing films at high speeds.
Martin Luther King, Jr. Day, University Holiday
Free Evolution of Superposition States in a Single Cooper Pair Box
Pierre M. Echternach
Jet Propulsion Laboratory
We have fabricated a single Cooper-pair box (SCB) in close proximity to a single electron transistor (SET) operated in the radio-frequency mode (RF-SET) with an inductor and capacitor lithographed directly on chip. The RF-SET was used to measure the charge state of the SCB revealing a 2e periodic charge quantization. We performed spectroscopy measurements to extract the charging energy (EC) and the Josephson coupling energy (EJ). Control of the temporal evolution of the quantum charge state was achieved by applying fast DC pulses to the SCB gate. The dephasing and relaxation times were extracted from these measurements.
We have improved the operation of a Josephson Junction based "phase" qubit by incorporating it into a superconducting loop. This has allowed us to further decouple the qubit from its environment and has eliminated quasiparticle heating effects. A new detection scheme based on an asymmetric d.c. SQUID allows detection of the quantum states with high efficiency and a controllable back action. This new device has revealed previously unknown two state microwave resonators within the qubit Josephson junction itself. Measurements of Rabi oscillations have shown that these spurious resonators strongly decohere the qubit. Recent improvements in the fabrication of the Josephson Junctions show a reduction in the magnitude of the spurious resonators as well as an improvement in the overall performance of the qubit by more than a factor of two. For example, we have seen coherence amplitudes as large as 76% with Rabi oscillation decay times >100 ns. We are currently performing detailed experiments in an effort to understand the various decoherence mechanisms so that we may eventually produce a truly useful solid state qubit.
Presidents Day, University Holiday
The interactions between proteins, DNA, and RNA in living cells constitute molecular networks that govern various cellular functions. To investigate the global dynamical properties and stabilities of such networks, we studied the network regulating the cell division (cell cycle) of the budding yeast. With the use of simple dynamical models, it was demonstrated that the cell-cycle network is extremely stable and robust for its function. The biological stationary state is a global attractor. The biological pathway is a globally attracting trajectory. These properties are largely preserved with respect to small perturbations to the network. These results suggest that cellular regulatory networks are robustly designed for their functions.
Studying Chromosome Dynamics in the Model Eukaryote S. cerevisiae (Baker's yeast)
Molecular and Computational Biology, Department of Biological Sciences, University of Southern California
No Colloquium: March APS Meeting
'Space Climate' - An attempt to understand long-term Solar-Terrestrial Relationships and their implications for the Earth's past climate variability
Department of Earth Sciences, University of Southern California
de Novo Multi-Scale Simulations Applied to Protein Folding, Drug Design, Nanotechnology, Materials Science, and Catalysis
William A. Goddard
Materials and Process Simulation Center, California Institute of Technology
Advances in theoretical and computational chemistry are making it practical to consider fully first principles (de novo) predictions of important systems and processes in the Chemical, Biological, and Materials Sciences. Quantitative models based on theory and computation are starting to become the basis for design and operations in industry, but strategies for linking the time scales from electrons to macroscale are required for the most important applications. We will highlight some recent advances in methodology with applications to protein folding, drug design, nanotechnology, materials science, and catalysis on topics such as: * First principles predicted 3D structures of G Protein Coupled Receptors (GPCRs) * Predictions on drugs for GPCRs (receptors for dopamine, serotonin, histamine, lipids) * nanoelectronic switches, prediction of current/voltage and switching performance * Mechanisms of Catalysts and Nafion membrane for PEM fuel cells * Plasticity and failure in amorphous metal alloys * Multiscale dynamics simulations of complex polysaccharides and polymers * De novo Force Fields (from QM) to describe reactions and phase transitions (ReaxFF).
Exploration and fabrication of novel material forms require understanding and control of complex material processes that take place at surfaces under a wide range of physical conditions. These material forms include stacks of ultrathiln films, organized 3-D nano-structures, and microarrays of biological macromolecules (i.e., bio-chips) that enable parallel detection of tens of thousands biochemical reactions on a functionalized soild surface. Due to the inherently non-intrusive and versatile natures, various forms of optical techniques have been developed and applied to studies of many material processes on hard and soft surfaces. I will describe a special form of optical ellipsometry, oblique-incidence optical reflectivity difference (OI-RD), that we have developed in recent years, and give examples of applications of such a technique in a series of investigation on thin film growth and on label-free detection of biochemical processes on surfaces in a microarray format.