217 research outputs found
Programa de control para tuberculosis bovina: aspectos a considerar para su etapa final
Outline:
• Available options for the Bovine TB (BTB) Control Program
• Current measures and status of the USA TB Control Program
• Obstacles to the eradication efforts
• Research findings and their implications in the current eradication efforts • Our laboratory research activities: current and future directionsAcademia Nacional de AgronomÃa y Veterinari
Programa de control para tuberculosis bovina: aspectos a considerar para su etapa final
Outline:
• Available options for the Bovine TB (BTB) Control Program
• Current measures and status of the USA TB Control Program
• Obstacles to the eradication efforts
• Research findings and their implications in the current eradication efforts • Our laboratory research activities: current and future directionsAcademia Nacional de AgronomÃa y Veterinari
Robustness of Cosmological Simulations I: Large Scale Structure
The gravitationally-driven evolution of cold dark matter dominates the
formation of structure in the Universe over a wide range of length scales.
While the longest scales can be treated by perturbation theory, a fully
quantitative understanding of nonlinear effects requires the application of
large-scale particle simulation methods. Additionally, precision predictions
for next-generation observations, such as weak gravitational lensing, can only
be obtained from numerical simulations. In this paper, we compare results from
several N-body codes using test problems and a diverse set of diagnostics,
focusing on a medium resolution regime appropriate for studying many
observationally relevant aspects of structure formation. Our conclusions are
that -- despite the use of different algorithms and error-control methodologies
-- overall, the codes yield consistent results. The agreement over a wide range
of scales for the cosmological tests is test-dependent. In the best cases, it
is at the 5% level or better, however, for other cases it can be significantly
larger than 10%. These include the halo mass function at low masses and the
mass power spectrum at small scales. While there exist explanations for most of
the discrepancies, our results point to the need for significant improvement in
N-body errors and their understanding to match the precision of near-future
observations. The simulation results, including halo catalogs, and initial
conditions used, are publicly available.Comment: 32 pages, 53 figures, data from the simulations is available at
http://t8web.lanl.gov/people/heitmann/arxiv, accepted for publication in
ApJS, several minor revisions, reference added, main conclusions unchange
Comparison of Endocrine Response to Stress Between Captive-Raised and Wild-Caught Bighorn Sheep
Stress hormones in Rocky Mountain bighorn sheep (Ovis canadensis canadensis), produced in response to environmental changes, road development, or high population density, may impact their immune systems to a threshold level that predisposes them to periodic, large-scale mortality. We compared the stress response to a novel environmental situation and repeated handling between bighorn sheep born and raised in captivity (CR) and bighorn sheep born in the wild (WC) and brought into captivity. We measured plasma epinephrine, norepinephrine, cortisol, and fecal glucocorticoid metabolites (FGM). Three weeks after each group’s arrival we used a one-time drop-net event to elicit an acute stress response, and we collected blood samples from each sheep over 35 minutes, as well as one fecal sample. We collected blood and fecal samples from both groups on 7 other occasions over the subsequent 6 months. We also collected fecal samples from the pen at approximately 24-hour intervals for 3 days following every handling event to monitor the stress response to handling. We found that CR sheep had a stronger autonomic nervous system response than WC sheep, as measured by epinephrine and norepinephrine levels, but we found a very similar hypothalamic–pituitary–adrenal axis (HPA) response, measured by cortisol levels, to the acute stress event of a drop-net restraint. We also found that once the WC sheep had acclimated, as indicated by the return to the initial baseline FGM levels within 12 weeks, the CR and WC groups’ HPA responses to sampling events were not significantly different from one another. Fecal samples can provide a noninvasive mechanism for managers to monitor baseline FGM for a given herd. Using long-term monitoring of FGM rather than values from a single point in time may allow managers to correlate these levels to outside influences on the herd and better understand the impacts of management changes, population density, or increased human developments on the health of the sheep population
The Halo Mass Function: High-Redshift Evolution and Universality
We study the formation of dark matter halos in the concordance LCDM model
over a wide range of redshifts, from z=20 to the present. Our primary focus is
the halo mass function, a key probe of cosmology. By performing a large suite
of nested-box N-body simulations with careful convergence and error controls
(60 simulations with box sizes from 4 to 256 Mpc/h, we determine the mass
function and its evolution with excellent statistical and systematic errors,
reaching a few percent over most of the considered redshift and mass range.
Across the studied redshifts, the halo mass is probed over 6 orders of
magnitude (10^7 - 10^13.5 M_sun/h). Historically, there has been considerable
variation in the high redshift mass function as obtained by different groups.
We have made a concerted effort to identify and correct possible systematic
errors in computing the mass function at high redshift and to explain the
discrepancies between some of the previous results. We discuss convergence
criteria for the required force resolution, simulation box size, halo mass
range, initial and final redshift, and time stepping. Because of conservative
cuts on the mass range probed by individual boxes, our results are relatively
insensitive to simulation volume, the remaining sensitivity being consistent
with extended Press-Schechter theory. Previously obtained mass function fits
near z=0, when scaled by linear theory, are in good agreement with our results
at all redshifts, although a mild redshift dependence consistent with that
found by Reed and collaborators exists at low redshifts.Comment: 20 pages, 15 figures. Minor changes to the text and figures; results
and conclusions unchange
Evaluation of antibody response to an adjuvanted hapten-protein vaccine as a potential inhibitor of sexual maturation for farmed Atlantic salmon
An experimental contraceptive vaccine was evaluated in Atlantic salmon (Salmo salar). A peptide derived from the beta subunit of luteinizing hormone (LH) was conjugated to two different carrier proteins, bovine serum albumin (BSA) and keyhole limpet hemocyanin (KLH), and formulated with one of four immunostimulants in a water-in-oil emulsion. Specific antibody responses to the peptide and each carrier protein were evaluated. While the antibody response to KLH was stronger than the response to BSA, both carrier proteins stimulated comparable antibody responses to the LH peptide. The immunostimulant proved to be more important for enhancing the LH peptide antibody response than the carrier protein selection; vaccines containing a combination of Aeromonas salmonicida and Vibrio anguillarum stimulated significantly greater LH peptide antibody production than any of the other three immunostimulants evaluated at 12 weeks post-vaccination. This study provides proof-of-concept for specific antibody production against a hapten-carrier protein antigen in Atlantic salmon and reinforces the importance of vaccine immunostimulant selection
Mass Function Predictions Beyond LCDM
The mass distribution of halos, as specified by the halo mass function, is a
key input for several cosmological probes. The sizes of -body simulations
are now such that, for the most part, results need no longer be
statistics-limited, but are still subject to various systematic uncertainties.
We investigate and discuss some of the reasons for these differences.
Quantifying error sources and compensating for them as appropriate, we carry
out a high-statistics study of dark matter halos from 67 -body simulations
to investigate the mass function and its evolution for a reference CDM
cosmology and for a set of CDM cosmologies. For the reference CDM
cosmology (close to WMAP5), we quantify the breaking of universality in the
form of the mass function as a function of redshift, finding an evolution of as
much as 10% away from the universal form between redshifts and . For
cosmologies very close to this reference we provide a fitting formula to our
results for the (evolving) CDM mass function over a mass range of
M to an estimated accuracy of about
2%. The set of CDM cosmologies is taken from the Coyote Universe simulation
suite. The mass functions from this suite (which includes a CDM
cosmology and others with ) are described by the fitting formula for
the reference CDM case at an accuracy level of 10%, but with clear
systematic deviations. We argue that, as a consequence, fitting formulae based
on a universal form for the mass function may have limited utility in high
precision cosmological applications.Comment: 19 pages; 18 figures; accepted for publication in the Ap
Dark Matter Halo Profiles of Massive Clusters: Theory vs. Observations
Dark matter-dominated cluster-scale halos act as an important cosmological
probe and provide a key testing ground for structure formation theory. Focusing
on their mass profiles, we have carried out (gravity-only) simulations of the
concordance LCDM cosmology, covering a mass range of 2.10^{12}-2.10^{15} solar
mass/h and a redshift range of z=0-2, while satisfying the associated
requirements of resolution and statistical control. When fitting to the
Navarro-Frenk-White profile, our concentration-mass (c-M) relation differs in
normalization and shape in comparison to previous studies that have limited
statistics in the upper end of the mass range. We show that the flattening of
the c-M relation with redshift is naturally expressed if c is viewed as a
function of the peak height parameter, \nu. Unlike the c-M relation, the slope
of the c-\nu relation is effectively constant over the redshift range z=0-2,
while the amplitude varies by ~30% for massive clusters. This relation is,
however, not universal: Using a simulation suite covering the allowed wCDM
parameter space, we show that the c-\nu relation varies by about +/- 20% as
cosmological parameters are varied. At fixed mass, the c(M) distribution is
well-fit by a Gaussian with \sigma_c/c = 0.33, independent of the radius at
which the concentration is defined, the halo dynamical state, and the
underlying cosmology. We compare the LCDM predictions with observations of halo
concentrations from strong lensing, weak lensing, galaxy kinematics, and X-ray
data, finding good agreement for massive clusters (M > 4.10^{14} solar mass/h),
but with some disagreements at lower masses. Because of uncertainty in
observational systematics and modeling of baryonic physics, the significance of
these discrepancies remains unclear.Comment: 18 pages; 13 figures, new observational data included, minor
revisions and extended discussions, improved fitting formula, results
unchange
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