26,287 research outputs found
Investigation of solid state traveling-wave- amplifier techniques for future satellite applications Quarterly progress report no. 4, 1 Mar. - 30 Jun. 1965
Solid state traveling wave amplifier techniques for satellite application
Investigation of solid state traveling-wave amplifier techniques for future satellite applications monthly progress report no. 5, 1 - 31 jan. 1965
Solid state traveling wave amplifier techniques for satellite application
Anisotropic Sliding Dynamics, Peak Effect, and Metastability in Stripe Systems
A variety of soft and hard condensed matter systems are known to form stripe
patterns. Here we use numerical simulations to analyze how such stripe states
depin and slide when interacting with a random substrate and with driving in
different directions with respect to the orientation of the stripes. Depending
on the strength and density of the substrate disorder, we find that there can
be pronounced anisotropy in the transport produced by different dynamical flow
phases. We also find a disorder-induced "peak effect" similar to that observed
for superconducting vortex systems, which is marked by a transition from
elastic depinning to a state where the stripe structure fragments or partially
disorders at depinning. Under the sudden application of a driving force, we
observe pronounced metastability effects similar to those found near the
order-disorder transition associated with the peak effect regime for
three-dimensional superconducting vortices. The characteristic transient time
required for the system to reach a steady state diverges in the region where
the flow changes from elastic to disordered. We also find that anisotropy of
the flow persists in the presence of thermal disorder when thermally-induced
particle hopping along the stripes dominates. The thermal effects can wash out
the effects of the quenched disorder, leading to a thermally-induced stripe
state. We map out the dynamical phase diagram for this system, and discuss how
our results could be explored in electron liquid crystal systems, type-1.5
superconductors, and pattern-forming colloidal assemblies.Comment: 18 pages, 22 postscript figure
CELSS Transportation Analysis
Regenerative life support systems based on the use of biological material was considered for inclusion in manned spacecraft. Biological life support systems are developed in the controlled ecological life support system (CELSS) program. Because of the progress achieved in the CELSS program, it is determined which space missions may profit from use of the developing technology. Potential transportation cost savings by using CELSS technology for selected future manned space missions was evaluated. Six representative missions were selected which ranged from a low Earth orbit mission to those associated with asteroids and a Mars sortie. The crew sizes considered varied from four persons to five thousand. Other study parameters included mission duration and life support closure percentages, with the latter ranging from complete resupply of consumable life support materials to 97% closure of the life support system. The analytical study approach and the missions and systems considered, together with the benefits derived from CELSS when applicable are described
Structural Transitions, Melting, and Intermediate Phases for Stripe and Clump Forming Systems
We numerically examine the properties of a two-dimensional system of
particles which have competing long range repulsive and short range attractive
interactions as a function of density and temperature. For increasing density,
there are well defined transitions between a low density clump phase, an
intermediate stripe phase, an anticlump phase, and a high density uniform
phase. To characterize the transitions between these phases we propose several
measures which take into account the different length scales in the system. For
increasing temperature, we find an intermediate phase that is liquid-like on
the short length scale of interparticle spacing but solid-like on the larger
length scale of the clump, stripe, or anticlump pattern. This intermediate
phase persists over the widest temperature range in the stripe state when the
local particle lattice within an individual stripe melts well below the
temperature at which the entire stripe structure breaks down, and is
characterized by intra-stripe diffusion of particles without inter-stripe
diffusion. This is followed at higher temperatures by the onset of inter-stripe
diffusion in an anisotropic diffusion phase, and then by breakup of the stripe
structure. We identify the transitions between these regimes through diffusion,
specific heat, and energy fluctuation measurements, and find that within the
intra-stripe liquid regime, the excess entropy goes into disordering the
particle arrangements within the stripe rather than affecting the stripe
structure itself. The clump and anticlump phases also show multiple
temperature-induced diffusive regimes which are not as pronounced as those of
the stripe phase.Comment: 13 pages, 17 postscript figure
The Attack-and-Defense Group Contests: Best-shot versus Weakest-link
This study analyzes a group contest in which one group (defenders) follows a weakest-link whereas the other group (attackers) follows a best-shot impact function. We fully characterize the Nash and coalition-proof equilibria and show that with symmetric valuation the coalition-proof equilibrium is unique up to the permutation of the identity of the active player in the attacker group. With asymmetric valuation it is always an equilibrium for one of the highest valuation players to be active; it may also be the case that the highest valuation players in the attacker group free-ride completely on a group-member with a lower valuation. However, in any equilibrium, only one player in the attacker group is active, whereas all the players in the defender group are active and exert the same effort. We also characterize the Nash and coalition-proof equilibria for the case in which one group follows either a best-shot or a weakest-link but the other group follows an additive impact function
The DOE/NASA wind turbine data acquisition system. Part 3: Unattended power performance monitor
Software documentation, operational procedures, and diagnostic instructions for development version of an unattended wind turbine performance monitoring system is provided. Designed to be used for off line intelligent data acquisition in conjunction with the central host computer
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Inhibition of histone deacetylase as a treatment for cardiac hypertrophy
The present invention provides for methods of treating and preventing cardiac hypertrophy. Class II HDACs, which are known to participate in regulation of chromatin structure and gene expression, have been shown to have beneficial effects on cardiac hypertrophy. Surprisingly, the present invention demonstrates that HDAC inhibitors inhibit cardiac hypertrophy by inhibiting fetal cardiac gene expression and interfering with sarcomeric organization.Board of Regents, University of Texas Syste
Realizing Colloidal Artificial Ice on Arrays of Optical Traps
We demonstrate how a colloidal version of artificial ice can be realized on
optical trap lattices. Using numerical simulations, we show that this system
obeys the ice rules and that for strong colloid-colloid interactions, an
ordered ground state appears. We show that the ice rule ordering can occur for
systems with as few as twenty-four traps and that the ordering transition can
be observed at constant temperature by varying the barrier strength of the
traps.Comment: 4 pages, 3 postscript figures; version to appear in Phys. Rev. Let
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