261 research outputs found
Factor Price Disparity in the Feeder Cattle Market and Retained Ownership Decision Making: An Application of Farm-Level Feed-Out Data
This study uses farm-level data from a university feed-out program to evaluate how the value of feeder cattle ultimately realized through finishing and grid pricing differs from their market value at public auction. Results indicate that uncertainty related to feedlot performance, final carcass merits, and fed cattle prices likely contribute to significant risk premiums in the feeder cattle market. This is consistent with the theory of factor price disparity. This result indicates that producers of cattle with known feedlot performance and/or carcass potential may be better off retaining ownership of their calves or marketing them in a way that communicates the information that is known about their potential performance directly to the buyer.Marketing,
Spatial-Temporal Dynamics of High-Resolution Animal Social Networks: What Can We Learn from Domestic Animals?
Recent studies of animal social networks have significantly increased our
understanding of animal behavior, social interactions, and many important
ecological and epidemiological processes. However, most of the studies are at
low temporal and spatial resolution due to the difficulty in recording accurate
contact information. Domestic animals such as cattle have social behavior and
serve as an excellent study system because their position can be explicitly and
continuously tracked, allowing their social networks to be accurately
constructed. We used radio-frequency tags to accurately track cattle position
and analyze high-resolution cattle social networks. We tested the hypothesis of
temporal stationarity and spatial homogeneity in these high-resolution networks
and demonstrated substantial spatial-temporal heterogeneity during different
daily time periods (feeding and non-feeding) and in different areas of the pen
(grain bunk, water trough, hay bunk, and other general pen area). The social
network structure is analyzed using global network characteristics (network
density, exponential random graph model structure), subgroup clustering
(modularity), triadic property (transitivity), and dyadic interactions
(correlation coefficient from a quadratic assignment procedure). Cattle tend to
have the strongest and most consistent contacts with others around the hay bunk
during the feeding time. These results cannot be determined from data at lower
spatial (aggregated at entire pen level) or temporal (aggregated at daily
level) resolution. These results reveal new insights for real-time animal
social network structure dynamics, providing more accurate descriptions that
allow more accurate modeling of multiple (both direct and indirect) disease
transmission pathways.Comment: 4 figure
Temporal-spatial heterogeneity in animal-environment contact: Implications for the exposure and transmission of pathogens
Contact structure, a critical driver of infectious disease transmission, is not completely understood and characterized for environmentally transmitted pathogens. In this study, we assessed the effects of temporal and spatial heterogeneity in animal contact structures on the dynamics of environmentally transmitted pathogens. We used real-time animal position data to describe contact between animals and specific environmental areas used for feeding and watering calves. The generated contact structure varied across days and among animals. We integrated animal and environmental heterogeneity into an agent-based simulation model for Escherichia coli O157 environmental transmission in cattle to simulate four different scenarios with different environmental bacteria concentrations at different areas. The simulation results suggest heterogeneity in environmental contact structure among cattle influences pathogen prevalence and exposure associated with each environment. Our findings suggest that interventions that target environmental areas, even relatively small areas, with high bacterial concentration can result in effective mitigation of environmentally transmitted pathogens.
doi:10.1038/srep0311
Diffuse Galactic antimatter from faint thermonuclear supernovae in old stellar populations
Our Galaxy hosts the annihilation of a few low-energy
positrons every second. Radioactive isotopes capable of supplying such
positrons are synthesised in stars, stellar remnants, and supernovae. For
decades, however, there has been no positive identification of a main stellar
positron source leading to suggestions that many positrons originate from
exotic sources like the Galaxy's central super-massive black hole or dark
matter annihilation. %, but such sources would not explain the
recently-detected positron signal from the extended Galactic disk. Here we show
that a single type of transient source, deriving from stellar populations of
age 3-6 Gyr and yielding ~0.03 of the positron emitter Ti, can
simultaneously explain the strength and morphology of the Galactic positron
annihilation signal and the solar system abundance of the Ti decay
product Ca. This transient is likely the merger of two low-mass white
dwarfs, observed in external galaxies as the sub-luminous, thermonuclear
supernova known as SN1991bg-like.Comment: 28 pages main text with 4 figures in preprint style; 26 pages of
Supplementary Informatio
Origin of Two Distinct Populations in Dwarf Spheroidal Galaxies
We study the chemical and kinematic properties of the first galaxies which
formed at a high redshift, using high resolution cosmological numerical
simulations, and compared them with the recent observational results for the
Sculptor dwarf spheroidal galaxy by Tolstoy et al., who found two distinct
stellar populations: the lower metallicity stars are more spatially extended
and possess a higher velocity dispersion than the higher metallicity stars. Our
calculations reproduce these observations as the result of a steep metallicity
gradient, within a single populations, induced by dissipative collapse of the
gas component. We also predict strong [N/O] enhancements in the lowest
metallicity stars in dwarf spheroidals, due to the preferential retention of
ejected gas from intermediate mass stars, compared to Type II supernovae.Comment: 11 pages, 10 figures, accepted for publication in Ap
The Cognitive Ageing, Nutrition and Neurogenesis trial: Design and progress
Introduction: Cohort studies indicate that long-chain n-3 polyunsaturated fatty acids and flavonoids may improve cognition and reduce dementia risk. The neuroprotective effects of these dietary components indicate that they are likely to be additive and potentially synergistic. Methods: The Cognitive Ageing, Nutrition and Neurogenesis trial hypothesizes that an intervention comprising long-chain n-3 polyunsaturated fatty acids (docosahexaenoic acid and eicosapentaenoic acid) and cocoa flavan-3-ols (n-3 FLAV) will mitigate the cognitive decline anticipated to naturally occur over 1 year in older adults with mild cognitive impairment or subjective memory impairment. A double-blinded, placebo-controlled parallel design is used. Two hundred fifty-nine adults (aged ≥55 years) with mild cognitive impairment or subjective memory impairment were recruited and randomized to a control or n-3 FLAV group (1.5 g docosahexaenoic acid + eicosapentaenoic acid and 500 mg n-3 FLAV daily) for 12 months. Cognitive performance was measured three times over the 1-year intervention, at 0 (baseline), 3, and 12 months. The primary end point is hippocampus-sensitive cognitive function (e.g., number of false-positives on the Picture Recognition Task of the Cognitive Drug Research test battery). Secondary outcomes include additional cognitive measures, brain atrophy and blood flow (assessed by magnetic resonance imaging), vascular function, circulating biomarkers of cardiovascular and cognitive health, gut microflora speciation and metabolism, red blood cell fatty acid status, and urine flavan-3-ol metabolites. The intervention arms were matched for sex and apolipoprotein E4 status to allow retrospective exploratory analysis of the impact of these variables on response to intervention. Results: Screening began in 2015, with all baseline visits completed in March 2017. The intervention was finished in March 2018. Discussion: Cognitive Ageing, Nutrition and Neurogenesis aims to identify an effective diet-based intervention to prevent or delay cognitive impairment in cognitively at-risk individuals, which could ultimately contribute to a reduced population burden of dementia
Disk evolution since z=1 in a CDM Universe
Increasingly large populations of disk galaxies are now being observed at
increasingly high redshifts, providing new constraints on our knowledge of how
such galaxies evolve. Are these observations consistent with a cosmology in
which structures form hierarchically? To probe this question, we employ
SPH/N-body galaxy scale simulations of late-type galaxies. We examine the
evolution of these simulated disk galaxies from redshift 1 to 0, looking at the
mass-size and luminosity-size relations, and the thickness parameter, defined
as the ratio of scale-height to scale-length. The structural parameters of our
simulated disks settle down quickly, and after redshift z=1 the galaxies evolve
to become only slightly flatter. Our present day simulated galaxies are larger,
more massive, less bright, and redder than at z=1. The inside-out nature of the
growth of our simulated galaxies reduces, and perhaps eliminates, expectations
of evolution in the size-mass relation.Comment: accepted version, to appear in ApJ 01 March 2006, v63
Antiviral CD8(+) T Cells Restricted by Human Leukocyte Antigen Class II Exist during Natural HIV Infection and Exhibit Clonal Expansion.
CD8(+) T cell recognition of virus-infected cells is characteristically restricted by major histocompatibility complex (MHC) class I, although rare examples of MHC class II restriction have been reported in Cd4-deficient mice and a macaque SIV vaccine trial using a recombinant cytomegalovirus vector. Here, we demonstrate the presence of human leukocyte antigen (HLA) class II-restricted CD8(+) T cell responses with antiviral properties in a small subset of HIV-infected individuals. In these individuals, T cell receptor β (TCRβ) analysis revealed that class II-restricted CD8(+) T cells underwent clonal expansion and mediated killing of HIV-infected cells. In one case, these cells comprised 12% of circulating CD8(+) T cells, and TCRα analysis revealed two distinct co-expressed TCRα chains, with only one contributing to binding of the class II HLA-peptide complex. These data indicate that class II-restricted CD8(+) T cell responses can exist in a chronic human viral infection, and may contribute to immune control
Identification and Characterization of Antifungal Compounds Using a Saccharomyces cerevisiae Reporter Bioassay
New antifungal drugs are urgently needed due to the currently limited selection, the emergence of drug resistance, and the toxicity of several commonly used drugs. To identify drug leads, we screened small molecules using a Saccharomyces cerevisiae reporter bioassay in which S. cerevisiae heterologously expresses Hik1, a group III hybrid histidine kinase (HHK) from Magnaporthe grisea. Group III HHKs are integral in fungal cell physiology, and highly conserved throughout this kingdom; they are absent in mammals, making them an attractive drug target. Our screen identified compounds 13 and 33, which showed robust activity against numerous fungal genera including Candida spp., Cryptococcus spp. and molds such as Aspergillus fumigatus and Rhizopus oryzae. Drug-resistant Candida albicans from patients were also highly susceptible to compounds 13 and 33. While the compounds do not act directly on HHKs, microarray analysis showed that compound 13 induced transcripts associated with oxidative stress, and compound 33, transcripts linked with heavy metal stress. Both compounds were highly active against C. albicans biofilm, in vitro and in vivo, and exerted synergy with fluconazole, which was inactive alone. Thus, we identified potent, broad-spectrum antifungal drug leads from a small molecule screen using a high-throughput, S. cerevisiae reporter bioassay
Association of rs780094 in GCKR with Metabolic Traits and Incident Diabetes and Cardiovascular Disease: The ARIC Study
The minor T-allele of rs780094 in the glucokinase regulator gene (GCKR) associates with a number of metabolic traits including higher triglyceride levels and improved glycemic regulation in study populations of mostly European ancestry. Using data from the Atherosclerosis Risk in Communities (ARIC) Study, we sought to replicate these findings, examine them in a large population-based sample of African American study participants, and to investigate independent associations with other metabolic traits in order to determine if variation in GKCR contributes to their observed clustering. In addition, we examined the association of rs780094 with incident diabetes, coronary heart disease (CHD), and stroke over up mean follow-up times of 8, 15, and 15 years, respectively.Race-stratified analyses were conducted among 10,929 white and 3,960 black participants aged 45-64 at baseline assuming an additive genetic model and using linear and logistic regression and Cox proportional hazards models.Previous findings replicated among white participants in multivariable adjusted models: the T-allele of rs780094 was associated with lower fasting glucose (p = 10(-7)) and insulin levels (p = 10(-6)), lower insulin resistance (HOMA-IR, p = 10(-9)), less prevalent diabetes (p = 10(-6)), and higher CRP (p = 10(-8)), 2-h postprandial glucose (OGTT, p = 10(-6)), and triglyceride levels (p = 10(-31)). Moreover, the T-allele was independently associated with higher HDL cholesterol levels (p = 0.022), metabolic syndrome prevalence (p = 0.043), and lower beta-cell function measured as HOMA-B (p = 0.011). Among black participants, the T-allele was associated only with higher triglyceride levels (p = 0.004) and lower insulin levels (p = 0.002) and HOMA-IR (p = 0.013). Prospectively, the T-allele was associated with reduced incidence of diabetes (p = 10(-4)) among white participants, but not with incidence of CHD or stroke.Our findings indicate rs780094 has independent associations with multiple metabolic traits as well as incident diabetes, but not incident CHD or stroke. The magnitude of association between the SNP and most traits was of lower magnitude among African American compared to white participants
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