4,398 research outputs found
Regional and temporal characteristics of bovine tuberculosis of cattle in Great Britain
Bovine tuberculosis (TB) is a chronic disease in cattle that causes a serious
food security challenge to the agricultural industry in terms of dairy and meat
production. In GB, Scotland has had a risk based surveillance testing policy
under which high risk herds are tested frequently, and in Sept 2009 was
officially declared as TB free. Wales have had an annual or more frequent
testing policy for all cattle herds since Jan 2010, while in England several
herds are still tested every 4 years except some high TB prevalence areas where
annual testing is applied. Time series analysis using publicly available data
for total tests on herds, total cattle slaughtered, new herd incidents, and
herds not TB free, were analysed globally for GB and locally for the
constituent regions of Wales, Scotland, West, North, and East England. After
detecting trends over time, underlying regional differences were compared with
the testing policies in the region. Total cattle slaughtered are decreasing in
Wales, Scotland and West England, but increasing in the North and East English
regions. New herd incidents, i.e., disease incidence, are decreasing in Wales,
Scotland, West English region, but increasing in North and East English
regions. Herds not TB free, are increasing in West, North, and East English
regions, while they are decreasing in Wales and Scotland. Total cattle
slaughtered were positively correlated with total tests in the West, North, and
East English regions, with high slopes of regression. There was no correlation
between total cattle slaughtered and total tests on herds in Wales indicating
that herds are tested frequent enough in order to detect all likely cases and
so control TB. The main conclusion of the analysis conducted here is that more
frequent testing is leading to lower TB infections in cattle both in terms of
TB prevalence as well as TB incidence.Comment: (in press) Stochastic Environmental Research and Risk Assessment
(2015
From a microscopic solution to a continuum description of active particles with a recoil interaction in one dimension
We consider a model system of persistent random walkers that can jam, pass
through each other or jump apart (recoil) on contact. In a continuum limit,
where particle motion between stochastic changes in direction becomes
deterministic, we find that the stationary inter-particle distribution
functions are governed by an inhomogeneous fourth-order differential equation.
Our main focus is on determining the boundary conditions that these
distribution functions should satisfy. We find that these do not arise
naturally from physical considerations, but need to be carefully matched to
functional forms that arise from the analysis of an underlying discrete
process. The inter-particle distribution functions, or their first derivatives,
are generically found to be discontinuous at the boundaries.Comment: 16 pages; 5 figures; published in PR
Grazing winter wheat relieves plant water stress and transiently enhances photosynthesis
In order to model the impact of grazing on wheat growth, we measured photosynthesis in the field. Grazing may affect photosynthesis as a consequence of changes to leaf water status, nitrogen content per unit leaf area (Na) or photosynthetic enzyme activity. While light-saturated CO2 assimilation rates (Asat) of field-grown wheat were unchanged during grazing, Asat transiently increased by 33-68% compared to ungrazed leaves over a two-four week period after grazing ended. Grazing reduced leaf mass per unit area, increased stomatal conductance and increased intercellular CO2 concentrations (Ci) by 36-38%, 88-169% and 17-20%, respectively. Grazing did not alter Na. Using a photosynthesis model, we demonstrated that the increase in Asat after grazing required an increase in Rubisco activity of up to 53%, whereas the increase in Ci could only increase Asat by up to 13%. Increased Rubisco activity was associated with a partial alleviation of leaf water stress. We observed a 68% increase in leaf water potential of grazed plants which could be attributed to reduced leaf area index and canopy evaporative demand, as well as increased rainfall infiltration into soil. The grazing of rain-fed grain cereals may be tailored to relieve plant water stress and enhance leaf photosynthesis
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Hydrodynamic loads on fiber-optic micro cables
A Finite Element Model of a deployed Fiber-Optic Micro Cable (FOMC) was performed using the marine cable modeling software, OrcaFlex. The focus of this study was a parametric analysis of a two-part, towed cable array with the FOMC dragged behind a depressor and connected to a drogue chute. Length-to-diameter ratios ranged from 3 x 10â” to 2 x 10â¶. Cable diameter was found to be the most critical parameter because of its influence on buoyancy while the tangential drag coefficient was surprisingly unimportant due to the presence of the drogue. Semi-analytical expressions to predict tension and cable elevation are presented as well as recommendations on equipment required to perform a physical experiment. The results were applied to a modified setup of the physical experiment that will deploy the FOMC from a Remotely Operated Vehicle (ROV) to an anchored mooring line. Recommended peel tensions for the tension controlled winch are provided
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Reaction Bonded Silicon Carbide: SFF, Process Refinement and Applications
Reaction bonded silicon carbide (RBSiC) has a wide variety of industrial applications and
a manufacturing process based on Selective Laser Sintering (SLS) has been demonstrated in
previous research at the University of Texas. That study was directed toward semiconductor
manufacturing applications and was based on prior indirect SLS methods. Several key research
questions were addressed for three main manufacturing phases: preform SLS, binder burnout and
reactive infiltration. The current research is focused on development of material systems and
manufacturing capability and is directed toward a broader set of potential applications. Preform
formation utilizes SiC powder of an appropriate average particle size mixed with a multicomponent binder. The preform or green part is then placed in a vacuum furnace to carbonize
the binder. The details of the binder chemistry must support accurate SFF shapes and acceptable
surface roughness, a strong green part and maintenance of the part shape during the first furnace
operation. Finally, the physics and chemistry of the infiltration process, based on the
microstructure of the initial green preform, determine the viability of the manufacturing process
and the characteristics of the final composite material.
The functionality of metal, polymer and ceramic matrix composites can support the
growing SFF industry desire to move beyond functional prototyping and into manufacturing
arenas. This project is being explored for more general application to matrix composite
materials, especially highly functional systems tailored specifically for SLS. The goal is to
establish the governing principles of binder function, carbonization and infiltration as well as to
understand the interdependence of these phases in terms of manufacturing application. With this
understanding new applications and special SLS composites can support the development of new
products and a greater SFF manufacturing presence.
This paper provides an introduction to the material, a look at basic rapid manufacturing
trends, an overview of the previous work, a review of relevant RBSiC material science issues,
and an outline of the current study.Mechanical Engineerin
A quantitative analysis of objective feather color assessment: Measurements in the laboratory do not reflect true plumage color
© 2016 American Ornithologists' Union.An important driver of the evolution of animal coloration is sexual selection operating on traits that are used to transmit information to rivals and potential mates, which has a major impact on fitness. Reflectance spectrometry has become a standard color-measuring tool, especially after the discovery of tetrachromacy in birds and their ability to detect UV light. Birds' plumage patterns may be invisible to humans, and therefore the establishment of reliable and quantitatively objective ways of assessing coloration not dependent on human vision is a technical need of primary importance. Plumage coloration measurements can be taken directly on live birds in the field, or in the laboratory (e.g., on collected feathers). However, which of these 2 approaches offers a more reliable, repeatable sampling method remains an unsolved question. Using a spectrophotometer, we measured melanin-based coloration in the plumage of Barn Swallows (Hirundo rustica). We assessed the repeatability of measures obtained with both traditional sampling methods to quantitatively determine their reliability. We used an ANOVA-based method for calculating the repeatability of measurements from 2 years separately, and a GLMM-based method to calculate overall adjusted repeatabilities for both years. The results of our study indicate a great disparity between color measurements obtained using both sampling methods and a low comparability across them. Assuming that measurements taken in the field reflect the real or "true" color of plumage, we may conclude that there is a lack of reliability of the laboratory method to reflect this true color in melanin-based plumages. Likewise, we recommend the use of the GLMM-based statistical method for repeatability calculations, as it allows the inclusion of random factors and the calculation of more realistic, adjusted repeatabilities. It also reduces the number of necessary tests, thereby increasing power, and it allows easy calculation of 95% CIs, a measure of the reliability and precision of effect-size calculations.published_or_final_versio
Quantitative Spectroscopy of Blue Supergiants in Metal-Poor Dwarf Galaxy NGC 3109
We present a quantitative analysis of the low-resolution (4.5 A) spectra of
12 late-B and early-A blue supergiants (BSGs) in the metal-poor dwarf galaxy
NGC 3109. A modified method of analysis is presented which does not require use
of the Balmer jump as an independent temperature indicator, as used in previous
studies. We determine stellar effective temperatures, gravities, metallicities,
reddening, and luminosities, and combine our sample with the early-B type BSGs
analyzed by Evans et al. (2007) to derive the distance to NGC 3109 using the
Flux-weighted Gravity-Luminosity Relation (FGLR). Using primarily Fe-group
elements, we find an average metallicity of [Z] = -0.67 +/- 0.13, and no
evidence of a metallicity gradient in the galaxy. Our metallicities are higher
than those found by Evans et al. (2007) based on the oxygen abundances of
early-B supergiants ([Z] = -0.93 +/- 0.07), suggesting a low alpha/Fe ratio for
the galaxy. We adjust the position of NGC 3109 on the BSG-determined galaxy
mass-metallicity relation accordingly and compare it to metallicity studies of
HII regions in star-forming galaxies. We derive an FGLR distance modulus of
25.55 +/- 0.09 (1.27 Mpc) that compares well with Cepheid and tip of the red
giant branch (TRGB) distances. The FGLR itself is consistent with those found
in other galaxies, demonstrating the reliability of this method as a measure of
extragalactic distances.Comment: 50 pages, 23 figures; Accepted for publication in The Astrophysical
Journa
Long Days Enhance Recognition Memory and Increase Insulin-like Growth Factor 2 in the Hippocampus
Light improves cognitive function in humans; however, the neurobiological mechanisms underlying positive effects of light remain unclear. One obstacle is that most rodent models have employed lighting conditions that cause cognitive deficits rather than improvements. Here we have developed a mouse model where light improves cognitive function, which provides insight into mechanisms underlying positive effects of light. To increase light exposure without eliminating daily rhythms, we exposed mice to either a standard photoperiod or a long day photoperiod. Long days enhanced long-term recognition memory, and this effect was abolished by loss of the photopigment melanopsin. Further, long days markedly altered hippocampal clock function and elevated transcription of Insulin-like Growth Factor2 (Igf2). Up-regulation of Igf2 occurred in tandem with suppression of its transcriptional repressor Wilmâs tumor1. Consistent with molecular de-repression of Igf2, IGF2 expression was increased in the hippocampus before and after memory training. Lastly, long days occluded IGF2-induced improvements in recognition memory. Collectively, these results suggest that light changes hippocampal clock function to alter memory, highlighting novel mechanisms that may contribute to the positive effects of light. Furthermore, this study provides insight into how the circadian clock can regulate hippocampus-dependent learning by controlling molecular processes required for memory consolidation
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