88 research outputs found
Housing system, milk production, and zero-grazing effects on lameness and leg injury in dairy cows
The aim of this study was to assess the effect of grazing (G) vs. zero-grazing (ZG), level of milk production,and quality and type of housing system [free stalls (FS)and straw yards (SY)] on the prevalence of lamenessand leg injuries in dairy cows. Observations were madeon 37 commercial dairy farms across Great Britain. Asingle visit of 5 d duration was made to each farm.During this visit, lameness scores and the incidence ofswellings, rubs, and injuries to hocks and knees wererecorded on all the peak- or mid-lactation cows. Aspectsof the quality of housing and management that werelikely to affect foot and leg health were recorded. Therewere more lame cows on ZG farms (39 ± 0.02%) thanon grazing (G) farms (15 ± 0.01%), and lameness scoreswere higher on FS farms compared with SY farms (0.25± 0.01 vs. 0.05 ± 0.01). Cows on SY farms had fewerhock and knee injuries compared with FS farms. The frequency of knee swellings was higher on ZG farms(0.31 ± 0.02) than on G farms (0.15 ± 0.01). Aspects of the free-stall design affected foot and leg health. The number of hock swellings increased with increasing stall gradient (0.16 ± 0.01 with no slope vs. 0.39 ± 0.02at a 0 to 1.5% slope). There was an interaction between the length of the free-stall lunging space and the hip width of the cow, indicating that the incidence of lameness is generally highest on farms with small free stalls and heavy cows. High levels of milk production did not affect lameness or leg injury. The results indicate that housing cows throughout the year potentially has adetrimental effect on foot and leg health. However, good free-stall design may reduce lameness and leg lesion
The evolution of the orbit distance in the double averaged restricted 3-body problem with crossing singularities
We study the long term evolution of the distance between two Keplerian
confocal trajectories in the framework of the averaged restricted 3-body
problem. The bodies may represent the Sun, a solar system planet and an
asteroid. The secular evolution of the orbital elements of the asteroid is
computed by averaging the equations of motion over the mean anomalies of the
asteroid and the planet. When an orbit crossing with the planet occurs the
averaged equations become singular. However, it is possible to define piecewise
differentiable solutions by extending the averaged vector field beyond the
singularity from both sides of the orbit crossing set. In this paper we improve
the previous results, concerning in particular the singularity extraction
technique, and show that the extended vector fields are Lipschitz-continuous.
Moreover, we consider the distance between the Keplerian trajectories of the
small body and of the planet. Apart from exceptional cases, we can select a
sign for this distance so that it becomes an analytic map of the orbital
elements near to crossing configurations. We prove that the evolution of the
'signed' distance along the averaged vector field is more regular than that of
the elements in a neighborhood of crossing times. A comparison between averaged
and non-averaged evolutions and an application of these results are shown using
orbits of near-Earth asteroids.Comment: 29 pages, 8 figure
Fermi surface and order parameter driven vortex lattice structure transitions in twin-free YBa2Cu3O7
We report on small-angle neutron scattering studies of the intrinsic vortex
lattice (VL) structure in detwinned YBa2Cu3O7 at 2 K, and in fields up to 10.8
T. Because of the suppressed pinning to twin-domain boundaries, a new distorted
hexagonal VL structure phase is stabilized at intermediate fields. It is
separated from a low-field hexagonal phase of different orientation and
distortion by a first-order transition at 2.0(2) T that is probably driven by
Fermi surface effects. We argue that another first-order transition at 6.7(2)
T, into a rhombic structure with a distortion of opposite sign, marks a
crossover from a regime where Fermi surface anisotropy is dominant, to one
where the VL structure and distortion is controlled by the order-parameter
anisotropy.Comment: 4 pages, 3 figures (2 color), minor change
Towards a framework for critical citizenship education
Increasingly countries around the world are promoting forms of "critical" citizenship in the planned curricula of schools. However, the intended meaning behind this term varies markedly and can range from a set of creative and technical skills under the label "critical thinking" to a desire to encourage engagement, action and political emancipation, often labelled "critical pedagogy". This paper distinguishes these manifestations of the "critical" and, based on an analysis of the prevailing models of critical pedagogy and citizenship education, develops a conceptual framework for analysing and comparing the nature of critical citizenship
NEOWISE Observations of Near-Earth Objects: Preliminary Results
With the NEOWISE portion of the \emph{Wide-field Infrared Survey Explorer}
(WISE) project, we have carried out a highly uniform survey of the near-Earth
object (NEO) population at thermal infrared wavelengths ranging from 3 to 22
m, allowing us to refine estimates of their numbers, sizes, and albedos.
The NEOWISE survey detected NEOs the same way whether they were previously
known or not, subject to the availability of ground-based follow-up
observations, resulting in the discovery of more than 130 new NEOs. The
survey's uniformity in sensitivity, observing cadence, and image quality have
permitted extrapolation of the 428 near-Earth asteroids (NEAs) detected by
NEOWISE during the fully cryogenic portion of the WISE mission to the larger
population. We find that there are 98119 NEAs larger than 1 km and
20,5003000 NEAs larger than 100 m. We show that the Spaceguard goal of
detecting 90% of all 1 km NEAs has been met, and that the cumulative size
distribution is best represented by a broken power law with a slope of
1.320.14 below 1.5 km. This power law slope produces 1,900
NEAs with 140 m. Although previous studies predict another break in the
cumulative size distribution below 50-100 m, resulting in an increase in
the number of NEOs in this size range and smaller, we did not detect enough
objects to comment on this increase. The overall number for the NEA population
between 100-1000 m are lower than previous estimates. The numbers of near-Earth
comets will be the subject of future work.Comment: Accepted to Ap
WISE/NEOWISE observations of Active Bodies in the Main Belt
We report results based on mid-infrared photometry of 5 active main belt
objects (AMBOs) detected by the Wide-field Infrared Survey Explorer (WISE)
spacecraft. Four of these bodies, P/2010 R2 (La Sagra), 133P/Elst-Pizarro,
(596) Scheila, and 176P/LINEAR, showed no signs of activity at the time of the
observations, allowing the WISE detections to place firm constraints on their
diameters and albedos. Geometric albedos were in the range of a few percent,
and on the order of other measured comet nuclei. P/2010 A2 was observed on
April 2-3, 2010, three months after its peak activity. Photometry of the coma
at 12 and 22 {\mu}m combined with ground-based visible-wavelength measurements
provides constraints on the dust particle mass distribution (PMD), dlogn/dlogm,
yielding power-law slope values of {\alpha} = -0.5 +/- 0.1. This PMD is
considerably more shallow than that found for other comets, in particular
inbound particle fluence during the Stardust encounter of comet 81P/Wild 2. It
is similar to the PMD seen for 9P/Tempel 1 in the immediate aftermath of the
Deep Impact experiment. Upper limits for CO2 & CO production are also provided
for each AMBO and compared with revised production numbers for WISE
observations of 103P/Hartley 2.Comment: 32 Pages, including 5 Figure
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Bioavailability in soils
The consumption of locally-produced vegetables by humans may be an important exposure pathway for soil contaminants in many urban settings and for agricultural land use. Hence, prediction of metal and metalloid uptake by vegetables from contaminated soils is an important part of the Human Health Risk Assessment procedure. The behaviour of metals (cadmium, chromium, cobalt, copper, mercury, molybdenum, nickel, lead and zinc) and metalloids (arsenic, boron and selenium) in contaminated soils depends to a large extent on the intrinsic charge, valence and speciation of the contaminant ion, and soil properties such as pH, redox status and contents of clay and/or organic matter. However, chemistry and behaviour of the contaminant in soil alone cannot predict soil-to-plant transfer. Root uptake, root selectivity, ion interactions, rhizosphere processes, leaf uptake from the atmosphere, and plant partitioning are important processes that ultimately govern the accumulation ofmetals and metalloids in edible vegetable tissues. Mechanistic models to accurately describe all these processes have not yet been developed, let alone validated under field conditions. Hence, to estimate risks by vegetable consumption, empirical models have been used to correlate concentrations of metals and metalloids in contaminated soils, soil physico-chemical characteristics, and concentrations of elements in vegetable tissues. These models should only be used within the bounds of their calibration, and often need to be re-calibrated or validated using local soil and environmental conditions on a regional or site-specific basis.Mike J. McLaughlin, Erik Smolders, Fien Degryse, and Rene Rietr
The Catalina Surveys Periodic Variable Star Catalog
We present ~47,000 periodic variables found during the analysis of 5.4
million variable star candidates within a 20,000 square degree region covered
by the Catalina Surveys Data Release-1 (CSDR1). Combining these variables with
type-ab RR Lyrae from our previous work, we produce an on-line catalog
containing periods, amplitudes, and classifications for ~61,000 periodic
variables. By cross-matching these variables with those from prior surveys, we
find that > 90% of the ~8,000 known periodic variables in the survey region are
recovered. For these sources we find excellent agreement between our catalog
and prior values of luminosity, period and amplitude, as well as
classification.
We investigate the rate of confusion between objects classified as contact
binaries and type-c RR Lyrae (RRc's) based on periods, colours, amplitudes,
metalicities, radial velocities and surface gravities. We find that no more
than few percent of these variables in these classes are misidentified. By
deriving distances for this clean sample of ~5,500 RRc's, we trace the path of
the Sagittarius tidal streams within the Galactic halo. Selecting 146
outer-halo RRc's with SDSS radial velocities, we confirm the presence of a
coherent halo structure that is inconsistent with current N-body simulations of
the Sagittarius tidal stream. We also find numerous long-period variables that
are very likely associated within the Sagittarius tidal streams system.
Based on the examination of 31,000 contact binary light curves we find
evidence for two subgroups exhibiting irregular lightcurves. One subgroup
presents significant variations in mean brightness that are likely due to
chromospheric activity. The other subgroup shows stable modulations over more
than a thousand days and thereby provides evidence that the O'Connell effect is
not due to stellar spots.Comment: Accepted ApJS, 43 pages, 9 tables, 44 figures (some at reduced
resolution
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