9,988 research outputs found
DSIF station schedules
System manages Deep Space Instrumentation Facilities /DSIF/ equipment construction and modification planning. Versatile program applies to such tasks as employee time and task schedules, pay schedules, operations schedules, and plant and equipment procurement, construction, modification or service
InSb charge coupled infrared imaging device: The 20 element linear imager
The design and fabrication of the 8585 InSb charge coupled infrared imaging device (CCIRID) chip are reported. The InSb material characteristics are described along with mask and process modifications. Test results for the 2- and 20-element CCIRID's are discussed, including gate oxide characteristics, charge transfer efficiency, optical mode of operation, and development of the surface potential diagram
Two Suns in The Sky: Stellar Multiplicity in Exoplanet Systems
We present results of a reconnaissance for stellar companions to all 131
radial-velocity-detected candidate extrasolar planetary systems known as of
July 1, 2005. CPM companions were investigated using the multi-epoch DSS
images, and confirmed by matching the trigonometric parallax distances of the
primaries to companion distances estimated photometrically. We also attempt to
confirm or refute companions listed in the Washington Double Star Catalog, the
Catalogs of Nearby Stars, in Hipparcos results, and in Duquennoy & Mayor
(1991).
Our findings indicate that a lower limit of 30 (23%) of the 131 exoplanet
systems have stellar companions. We report new stellar companions to HD 38529
and HD 188015, and a new candidate companion to HD 169830. We confirm many
previously reported stellar companions, including six stars in five systems
that are recognized for the first time as companions to exoplanet hosts. We
have found evidence that 20 entries in the Washington Double Star Catalog are
not gravitationally bound companions. At least three, and possibly five, of the
exoplanet systems reside in triple star systems. Three exoplanet systems have
potentially close-in stellar companions ~ 20 AU away from the primary. Finally,
two of the exoplanet systems contain white dwarf companions. This comprehensive
assessment of exoplanet systems indicates that solar systems are found in a
variety of stellar multiplicity environments - singles, binaries, and triples;
and that planets survive the post-main-sequence evolution of companion stars.Comment: 52 pages, 7 figures, Accepted for publication in Ap
Open-source development experiences in scientific software: the HANDE quantum Monte Carlo project
The HANDE quantum Monte Carlo project offers accessible stochastic algorithms
for general use for scientists in the field of quantum chemistry. HANDE is an
ambitious and general high-performance code developed by a
geographically-dispersed team with a variety of backgrounds in computational
science. In the course of preparing a public, open-source release, we have
taken this opportunity to step back and look at what we have done and what we
hope to do in the future. We pay particular attention to development processes,
the approach taken to train students joining the project, and how a flat
hierarchical structure aids communicationComment: 6 pages. Submission to WSSSPE
Universal Mandelbrot Set as a Model of Phase Transition Theory
The study of Mandelbrot Sets (MS) is a promising new approach to the phase
transition theory. We suggest two improvements which drastically simplify the
construction of MS. They could be used to modify the existing computer programs
so that they start building MS properly not only for the simplest families.
This allows us to add one more parameter to the base function of MS and
demonstrate that this is not enough to make the phase diagram connectedComment: 5 pages, 3 figure
Catastrophic regime shifts in model ecological communities are true phase transitions
Ecosystems often undergo abrupt regime shifts in response to gradual external
changes. These shifts are theoretically understood as a regime switch between
alternative stable states of the ecosystem dynamical response to smooth changes
in external conditions. Usual models introduce nonlinearities in the
macroscopic dynamics of the ecosystem that lead to different stable attractors
among which the shift takes place. Here we propose an alternative explanation
of catastrophic regime shifts based on a recent model that pictures ecological
communities as systems in continuous fluctuation, according to certain
transition probabilities, between different micro-states in the phase space of
viable communities. We introduce a spontaneous extinction rate that accounts
for gradual changes in external conditions, and upon variations on this control
parameter the system undergoes a regime shift with similar features to those
previously reported. Under our microscopic viewpoint we recover the main
results obtained in previous theoretical and empirical work (anomalous
variance, hysteresis cycles, trophic cascades). The model predicts a gradual
loss of species in trophic levels from bottom to top near the transition. But
more importantly, the spectral analysis of the transition probability matrix
allows us to rigorously establish that we are observing the fingerprints, in a
finite size system, of a true phase transition driven by background
extinctions.Comment: 19 pages, 11 figures, revised versio
Milk Production from Cows Grazing Perennial Ryegrass Pastures Infected with Wild or AR1 Endophyte in New Zealand
Most perennial ryegrass (Lolium perenne) cultivars in New Zealand are available with either the natural wild endophyte (Neotyphodium lolii); the AR1 novel endophyte (no lolitrem B or ergovaline production); or endophyte-free. Although wild endophyte protects ryegrass against insect attack, improving pasture persistence, it can also cause ryegrass staggers and reduced animal performance. Endophyte AR1 does not cause ryegrass staggers but still protects against insect pests such as Argentine stem weevil (Listronotus bonariensis). A 3-year farmlet experiment was carried out to evaluate the effects of AR1 and wild endophyte-infected ryegrass on pasture performance, milk production and cow health
Metastable Quantum Phase Transitions in a Periodic One-dimensional Bose Gas: Mean-Field and Bogoliubov Analyses
We generalize the concept of quantum phase transitions, which is
conventionally defined for a ground state and usually applied in the
thermodynamic limit, to one for \emph{metastable states} in \emph{finite size
systems}. In particular, we treat the one-dimensional Bose gas on a ring in the
presence of both interactions and rotation. To support our study, we bring to
bear mean-field theory, i.e., the nonlinear Schr\"odinger equation, and linear
perturbation or Bogoliubov-de Gennes theory. Both methods give a consistent
result in the weakly interacting regime: there exist \emph{two topologically
distinct quantum phases}. The first is the typical picture of superfluidity in
a Bose-Einstein condensate on a ring: average angular momentum is quantized and
the superflow is uniform. The second is new: one or more dark solitons appear
as stationary states, breaking the symmetry, the average angular momentum
becomes a continuous quantity, and the phase of the condensate can be
continuously wound and unwound
The Large, Oxygen-Rich Halos of Star-Forming Galaxies Are A Major Reservoir of Galactic Metals
The circumgalactic medium (CGM) is fed by galaxy outflows and accretion of
intergalactic gas, but its mass, heavy element enrichment, and relation to
galaxy properties are poorly constrained by observations. In a survey of the
outskirts of 42 galaxies with the Cosmic Origins Spectrograph onboard the
Hubble Space Telescope, we detected ubiquitous, large (150 kiloparsec) halos of
ionized oxygen surrounding star-forming galaxies, but we find much less ionized
oxygen around galaxies with little or no star formation. This ionized CGM
contains a substantial mass of heavy elements and gas, perhaps far exceeding
the reservoirs of gas in the galaxies themselves. It is a basic component of
nearly all star-forming galaxies that is removed or transformed during the
quenching of star formation and the transition to passive evolution.Comment: This paper is part of a set of three papers on circumgalactic gas
observed with the Cosmic Origins Spectrograph on HST, to be published in
Science, together with related papers by Tripp et al. and Lehner & Howk, in
the November 18, 2011 edition. This version has not undergone final
copyediting. Please see Science online for the final printed versio
Solid Livestock Waste Regulatory Requirements
Proper management and utilization of livestock waste can be a significant contribution to the economic well being of a livestock enterprise, since the wastes have considerable economic value if properly utilized. When returned to the soil as fertilize or soil conditioner, the value as a nutrient source has been will established. More recently, processed livestock wastes have been utilized as a high protein feed additives. Livestock waste should be considered a resource to be utilized rather than a disposal problem
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