1,710 research outputs found
Whiterock Conservancy baseline data project
Baseline surveys of pasture diversity and bird populations were conducted and will be used to help inform conservation-based land management decisions at the Whiterock Conservancy in southwest Iowa
Thermodynamic evolution of cosmological baryonic gas: I. Influence of non-equipartition processes
Using N-body/hydrodynamic simulations, the influence of non-equipartition
processes on the thermal and dynamical properties of cosmological baryonic gas
is investigated. We focus on a possible departure from equilibrium between
electrons, ions and neutral atoms in low temperature (10^4-10^6 K) and weakly
ionized regions of the intergalactic medium. The simulations compute the energy
exchanges between ions, neutrals and electrons, without assuming thermal
equilibrium. They include gravitation, shock heating and cooling processes, and
follow self-consistently the chemical evolution of a primordial composition
hydrogen-helium plasma without assuming collisional ionization equilibrium. At
high redshift, a significant fraction of the intergalactic medium is found to
be warmer and weakly ionized in simulations with non-equipartition processes
than in simulations in which the cosmological plasma is considered to be in
thermodynamic equilibrium. With a semi-analytical study of the out of
equilibrium regions we show that, during the formation of cosmic structures,
departure from equilibrium in accreted plasma results from the competition
between the atomic cooling processes and the elastic processes between heavy
particles and electrons. Our numerical results are in agreement with this
semi-analytical model. Therefore, since baryonic matter with temperatures
around 10^4 K is a reservoir for galaxy formation, non-equipartition processes
are expected to modify the properties of the objects formed.Comment: 15 pages, 16 figures. Accepted for publication in A&A. For a version
with high-resolution figures, see
http://www.raunvis.hi.is/~courty/series.htm
Lead Poisoning in Bald Eagles Admitted to Wildlife Rehabilitation Facilities in Iowa, 2004–2014
Eleven years (2004–2014) of bald eagle Haliaeetus leucocephalus data from four independent, state and federally permitted wildlife rehabilitators in Iowa were assessed for the prevalence of elevated lead levels in blood or tissue samples. The relationship between blood lead concentrations and recorded information (age, season, radiographs, and clinical outcome) was investigated. Adult birds had higher blood lead concentrations than immature and juvenile birds. Highest blood lead levels were found during October–January. Bald eagles with positive radiographs for metallic opacities in the digestive tract had higher blood and tissue lead concentrations than those with negative results or those on which no radiograph was performed. Metallic opacities were identified through necropsy. Bald eagles with elevated levels of lead were associated with poor clinical outcomes, indicating that blood lead concentrations could be used as a predictor of clinical outcome
Coalitions in the quantum Minority game: classical cheats and quantum bullies
In a one-off Minority game, when a group of players agree to collaborate they
gain an advantage over the remaining players. We consider the advantage
obtained in a quantum Minority game by a coalition sharing an initially
entangled state versus that obtained by a coalition that uses classical
communication to arrive at an optimal group strategy. In a model of the quantum
Minority game where the final measurement basis is randomized, quantum
coalitions outperform classical ones when carried out by up to four players,
but an unrestricted amount of classical communication is better for larger
coalition sizes.Comment: 12 pages, 1 figur
Dynamics in Stationary, Non-Globally Hyperbolic Spacetimes
Classically, the dynamics in a non-globally hyperbolic spacetime is ill
posed. Previously, a prescription was given for defining dynamics in static
spacetimes in terms of a second order operator acting on a Hilbert space
defined on static slices. The present work extends this result by giving a
similar prescription for defining dynamics in stationary spacetimes obeying
certain mild assumptions. The prescription is defined in terms of a first order
operator acting on a different Hilbert space from the one used in the static
prescription. It preserves the important properties of the earlier one: the
formal solution agrees with the Cauchy evolution within the domain of
dependence, and smooth data of compact support always give rise to smooth
solutions. In the static case, the first order formalism agrees with second
order formalism (using specifically the Friedrichs extension). Applications to
field quantization are also discussed.Comment: 18 pages, 1 figure, AMSLaTeX; v2: expanded discussion of field
quantization, new Proposition 3.1, revised Theorem 4.2, corrected typos, and
updated reference
Quantum singularity of Levi-Civita spacetimes
Quantum singularities in general relativistic spacetimes are determined by
the behavior of quantum test particles. A static spacetime is quantum
mechanically singular if the spatial portion of the wave operator is not
essentially self-adjoint. Here Weyl's limit point-limit circle criterion is
used to determine whether a wave operator is essentially self-adjoint. This
test is then applied to scalar wave packets in Levi-Civita spacetimes to help
elucidate the physical properties of the spacetimes in terms of their metric
parameters
Effects of deletion of the receptor CrlA on <i>Dictyostelium </i>aggregation and MPBD mediated responses are strain-dependent and not evident in strain Ax2
The primate-specific peptide Y-P30 regulates morphological maturation of neocortical dendritic spines
The 30-amino acid peptide Y-P30 corresponds to the N-terminus of the primate-specific, sweat gland-derived dermcidin prepropeptide. Previous work has revealed that Y-P30 enhances the interaction of pleiotrophin and syndecans-2/3, and thus represents a natural ligand to study this signaling pathway. In immature neurons, Y-P30 activates the c-Src and p42/44 ERK kinase pathway, increases the amount of F-actin in axonal growth cones, and promotes neuronal survival, cell migration and axonal elongation. The action of Y-P30 on axonal growth requires syndecan-3 and heparan sulfate side chains. Whether Y-P30 has the potential to influence dendrites and dendritic protrusions has not been explored. The latter is suggested by the observations that syndecan-2 expression increases during postnatal development, that syndecan-2 becomes enriched in dendritic spines, and that overexpression of syndecan-2 in immature neurons results in a premature morphological maturation of dendritic spines. Here, analysing rat cortical pyramidal and non-pyramidal neurons in organotypic cultures, we show that Y-P30 does not alter the development of the dendritic arborization patterns. However, Y-P30 treatment decreases the density of apical, but not basal dendritic protrusions at the expense of the filopodia. Analysis of spine morphology revealed an unchanged mushroom/stubby-to-thin spine ratio and a shortening of the longest decile of dendritic protrusions. Whole-cell recordings from cortical principal neurons in dissociated cultures grown in the presence of Y-P30 demonstrated a decrease in the frequency of glutamatergic mEPSCs. Despite these differences in protrusion morphology and synaptic transmission, the latter likely attributable to presynaptic effects, calcium event rate and amplitude recorded in pyramidal neurons in organotypic cultures were not altered by Y-P30 treatment. Together, our data suggest that Y-P30 has the capacity to decelerate spinogenesis and to promote morphological, but not synaptic, maturation of dendritic protrusions.Peer reviewe
Mining metrics for buried treasure
The same but different: That might describe two metrics. On the surface
CLASSI may show two metrics are locally equivalent, but buried beneath one may
be a wealth of further structure. This was beautifully described in a paper by
M.A.H. MacCallum in 1998. Here I will illustrate the effect with two flat
metrics -- one describing ordinary Minkowski spacetime and the other describing
a three-parameter family of Gal'tsov-Letelier-Tod spacetimes. I will dig out
the beautiful hidden classical singularity structure of the latter (a structure
first noticed by Tod in 1994) and then show how quantum considerations can
illuminate the riches. I will then discuss how quantum structure can help us
understand classical singularities and metric parameters in a variety of exact
solutions mined from the Exact Solutions book.Comment: 16 pages, no figures, minor grammatical changes, submitted to
Proceedings of the Malcolm@60 Conference (London, July 2004
Segmentation of the C57BL/6J mouse cerebellum in magnetic resonance images
The C57BL mouse is the centerpiece of efforts to use gene-targeting technology to understand cerebellar pathology, thus creating a need for a detailed magnetic resonance imaging (MRI) atlas of the cerebellum of this strain. In this study we present a methodology for systematic delineation of the vermal and hemispheric lobules of the C57BL/6J mouse cerebellum in magnetic resonance images. We have successfully delineated 38 cerebellar and cerebellar-related structures. The higher signal-to-noise ratio achieved by group averaging facilitated the identification of anatomical structures. In addition, we have calculated average region volumes and created probabilistic maps for each structure. The segmentation method and the probabilistic maps we have created will provide a foundation for future studies of cerebellar disorders using transgenic mouse models
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