Quantum Critical Points in Quantum Impurity Systems

The numerical renormalization group method is used to investigate zero temperature phase transitions in quantum impurity systems, in particular in the soft-gap Anderson model, where an impurity couples to a non-trivial fermionic bath. In this case, zero temperature phase transitions occur between two different phases whose fixed points can be built up of non-interacting single-particle states. However, the quantum critical point cannot be described by non-interacting fermionic or bosonic excitations.Comment: 2 pages, 3 figures, submitted to SCES'0

Noiseless coding for the Gamma Ray spectrometer

The payload of several future unmanned space missions will include a sophisticated gamma ray spectrometer. Severely constrained data rates during certain portions of these missions could limit the possible science return from this instrument. This report investigates the application of universal noiseless coding techniques to represent gamma ray spectrometer data more efficiently without any loss in data integrity. Performance results demonstrate compression factors from 2.5:1 to 20:1 in comparison to a standard representation. Feasibility was also demonstrated by implementing a microprocessor breadboard coder/decoder using an Intel 8086 processor

High-temperature, long-life polyimide seals for hydraulic actuator rods

Two types of polyimide seals are developed for hydraulic actuator rod in low pressure second stage of two-stage configuration. Each seal melts test objectives of twenty million cycles of operation at 534 K. Analytical and experimental study results are discussed. Potential applications are given

Exciton-exciton interaction and biexciton formation in bilayer systems

We report quantum Monte Carlo calculations of biexciton binding energies in ideal two-dimensional bilayer systems with isotropic electron and hole masses. We have also calculated exciton-exciton interaction potentials, and pair distribution functions for electrons and holes in bound biexcitons. Comparing our data with results obtained in a recent study using a model exciton-exciton potential [C. Schindler and R. Zimmermann, Phys. Rev. B \textbf{78}, 045313 (2008)], we find a somewhat larger range of layer separations at which biexcitons are stable. We find that individual excitons retain their identity in bound biexcitons for large layer separations.Comment: 7 pages, 11 figures, 2 table

The National Marine Fisheries Service’s National Bycatch Strategy

The National Marine Fisheries Service (NMFS) launched its National Bycatch Strategy (NBS) in March 2003 in response to the continued fisheries management challenge posed by fisheries bycatch. NMFS has several strong mandates for fish and protected species bycatch reduction, including the Magnuson-Stevens Fishery Conservation and Management Act, the Endangered Species Act, and the Marine Mammal Protection Act. Despite efforts to address bycatch during the 1990’s, NMFS was petitioned in 2002 to count, cap, and control bycatch. The NBS initiated as part of NMFS’s response to the petition for rulemaking contained six components: 1) assess bycatch progress, 2) develop an approach to standardized bycatch reporting methodology, 3) develop bycatch implementation plans, 4) undertake education and outreach, 5) develop new international approaches to bycatch, and 6) identify new funding requirements. The definition of bycatch for the purposes of the NBS proved to be a contentious issue for NMFS, but steady progress is being made by the agency and its partners to minimize bycatch to the extent practicable

New analytic results for electroweak baryon number violation

Real-time anomalous fermion number violation has been investigated for massless chiral fermions in spherically symmetric SU(2) Yang-Mills gauge field backgrounds which can be weakly dissipative or even nondissipative. Restricting consideration to spherically symmetric fermion fields, a relation has been found between the spectral flow of the Dirac Hamiltonian and two characteristics of the background gauge field. This new result may be relevant to electroweak baryon number violation in the early universe.Comment: 7 pages with jhep3.cls, based on a talk at the International Europhysics Conference on High Energy Physics, Budapest, 200

Case study of sample spacing in planar near-field measurement of high gain antennas

Far field antenna patterns can be reconstructed from planar near field measurements acquired at a sample spacing of lambda/2 or less. For electrically large antennas, sampling at the Nyquist rate may result in errors due to system electronic drift over long acquisition times. The computer capacity may limit the largest size of the near field data set. The requirement to sample at the Nyquist rate is relaxed for high gain antennas which concentrate most of the radiated energy into a small angular region of the far field. The criteria for sample spacing at greater than lambda/e through the use of a priori information of the antenna radiation characteristics are presented. Far field patterns of a 30 GHz dual offset reflector system with a 2.7 m parabolic main reflector are computed from near field data obtained at sample spacings ranging from 0.1 lambda to 10 lambda. The effects of sampling interval and spectrum cutoff on the far field patterns are discussed

Image data compression application to imaging spectrometers

The potential of image data compression techniques to satisfy the anticipated requirements of imaging spectrometer missions is discussed. Noiseless coding, rate controlled compression, cluster compression, and error protection are addressed