Rotational correlation and dynamic heterogeneity in a kinetically constrained lattice gas

We study dynamical heterogeneity and glassy dynamics in a kinetically constrained lattice gas model which has both translational and rotational degrees of freedom. We find that the rotational diffusion constant tracks the structural relaxation time as density is increased whereas the translational diffusion constant exhibits a strong decoupling. We investigate distributions of exchange and persistence times for both the rotational and translational degrees of freedom and compare our results on the distributions of rotational exchange times to recent single molecule studies.Comment: 7 pages, 5 figure

Space station operating system study

The current phase of the Space Station Operating System study is based on the analysis, evaluation, and comparison of the operating systems implemented on the computer systems and workstations in the software development laboratory. Primary emphasis has been placed on the DEC MicroVMS operating system as implemented on the MicroVax II computer, with comparative analysis of the SUN UNIX system on the SUN 3/260 workstation computer, and to a limited extent, the IBM PC/AT microcomputer running PC-DOS. Some benchmark development and testing was also done for the Motorola MC68010 (VM03 system) before the system was taken from the laboratory. These systems were studied with the objective of determining their capability to support Space Station software development requirements, specifically for multi-tasking and real-time applications. The methodology utilized consisted of development, execution, and analysis of benchmark programs and test software, and the experimentation and analysis of specific features of the system or compilers in the study

The low-mass population of the Rho Ophiuchi molecular cloud

Star formation theories are currently divergent regarding the fundamental physical processes that dominate the substellar regime. Observations of nearby young open clusters allow the brown dwarf (BD) population to be characterised down to the planetary mass regime, which ultimately must be accommodated by a successful theory. We hope to uncover the low-mass population of the Rho Ophiuchi molecular cloud and investigate the properties of the newly found brown dwarfs. We use near-IR deep images (reaching completeness limits of approximately 20.5 mag in J, and 18.9 mag in H and Ks) taken with the Wide Field IR Camera (WIRCam) at the Canada France Hawaii Telescope (CFHT) to identify candidate members of Rho Oph in the substellar regime. A spectroscopic follow-up of a small sample of the candidates allows us to assess their spectral type, and subsequently their temperature and membership. We select 110 candidate members of the Rho Ophiuchi molecular cloud, from which 80 have not previously been associated with the cloud. We observed a small sample of these and spectroscopically confirm six new brown dwarfs with spectral types ranging from M6.5 to M8.25

Results from the LSND Neutrino Oscillation Search

The Liquid Scintillator Neutrino Detector (LSND) at the Los Alamos Meson Physics Facility sets bounds on neutrino oscillations in the appearance channel nu_mu_bar --> nu_e_bar by searching for the signature of the reaction nu_e_bar p --> e^+ n: an e$^+$ followed by a 2.2MeV gamma ray from neutron capture. Five e^{+/-} -- gamma coincidences are observed in time with the LAMPF beam, with an estimated background of 6.2 events. The 90\% confidence limits obtained are: Delta (m^2) < 0.07eV^2 for sin^2 (2theta) = 1, and sin^2(2theta) < 6 10^{-3} for Delta (m^2) > 20 eV^2.Comment: 10 pages, uses REVTeX and epsf macro

Avalanche-Induced Current Enhancement in Semiconducting Carbon Nanotubes

Semiconducting carbon nanotubes under high electric field stress (~10 V/um) display a striking, exponential current increase due to avalanche generation of free electrons and holes. Unlike in other materials, the avalanche process in such 1D quantum wires involves access to the third sub-band, is insensitive to temperature, but strongly dependent on diameter ~exp(-1/d^2). Comparison with a theoretical model yields a novel approach to obtain the inelastic optical phonon emission length, L_OP,ems ~ 15d nm. The combined results underscore the importance of multi-band transport in 1D molecular wires

Gaussian Approximation Potentials: the accuracy of quantum mechanics, without the electrons

We introduce a class of interatomic potential models that can be automatically generated from data consisting of the energies and forces experienced by atoms, derived from quantum mechanical calculations. The resulting model does not have a fixed functional form and hence is capable of modeling complex potential energy landscapes. It is systematically improvable with more data. We apply the method to bulk carbon, silicon and germanium and test it by calculating properties of the crystals at high temperatures. Using the interatomic potential to generate the long molecular dynamics trajectories required for such calculations saves orders of magnitude in computational cost.Comment: v3-4: added new material and reference

Instantaneous current prediction for Naval Operations

OCEANS2005, MTS/IEEE Conference Proceedings, DVD-ROMNaval operations depend highly upon environmental conditions that can either adversely affect successful completion or hinder the safety of personnel. Each warfare community has defined environmental thresholds and operating limits that restrict the execution of any intended maneuver. As the warfare environment continues to shift from the open ocean to the littoral, prediction of the shallow water environment is an urgent need in order to support these operations. The value-aided of using a hydrodynamic model (WQMAP) for the mission planning of the naval operations in San Diego Bay is demonstrated in this study. A new model verification procedure (i.e., compatibility verification) is proposed for the tidal dominated littoral basin prediction