40,123 research outputs found
The Polarization of Drifting Subpulses
Using new techniques based on the polarimetric fluctuation spectrum, the
fluctuation behaviour of the polarization of individual pulses is examined in
three pulsars that show drifting subpulses, allowing various aspects of the
fluctuations to be quantified for the first time. Of the three pulsars studied,
only PSR B0809+74 shows behaviour completely consistent with the superposition
of orthogonal polarization modes (OPMs), and this only at 328 MHz and in
superposition with an apparently randomly polarized component. The observed
periodic pattern is decomposed into the sum of two orthogonally polarized,
out-of-phase drift patterns, one of which shows a dramatic jump in subpulse
phase near the leading edge of the pulse window. For PSR B0320+39 and PSR
B081813, considerable periodic fluctuations away from OPM orientations are
seen, a condition that also occurs in the trailing half of the pulse in PSR
B0809+74 at 1380 MHz. In some cases the deviation is so strong that the
periodic locus of the polarization vector in the Poincar\'{e} sphere is almost
circular, in contrast to the strictly colinear states of superposed OPMs.
Several possibilities are discussed for the physical origin of these patterns.
The similarity between the subpulse patterns in one of the OPMs of PSR B0809+74
at 328 MHz to that of the total intensity signal at 1380 MHz supports a picture
of superposed, out of phase drift patterns. To explain the full range of
behaviour seen in the three pulsars, it must be possible to produce at least
three arbitrarily polarized superposed patterns. While the data do not suggest
a particular approach for the empirical decomposition of patterns into
non-orthogonally polarized components, the specific, quantitative nature of the
results should provide strong constraints for theoretically driven modelling.Comment: 11 pages, 6 figures (1 colour), accepted for publication in A&A.
Abstract abridge
Effect of Land Application of Poultry Waste on Pesticide Loss
The poultry industry in Arkansas is a large, concentrated, growing industry that produces a high volume of fecal waste. Most of this waste is surface applied as pasture fertilizer. Pesticides are commonly used in the poultry industry for fly and litter beetle contro land are often a component of the surface-applied poultry waste. No information exists in the scientific literature regarding the transport of this pesticide component to nearby water supplies.Our research focused on cyromazine, a feed-through larvicide used to control flies in caged-layer hen houses. Tetrachlorvinphos and carbaryl are also used in poultry waste, but these pesticides have a relatively low solubility in water and rapid decomposition rate. Cyromazine, however, is highly soluble and stable in water. Since it may be readily washed from the pasture by heavy rainfall and may persist in surface and soil water, cyromazine appears to be potentially a much greater long-term threat to water quality than either carbaryl or tetrachlorvinphos. Therefore, the objective of this investigation was to examine the extent of cyromazine loss as a result of land application of caged layer manure. To quantify cyromazine loss from pasture plots treated with caged layer manure,research was conducted at the University of Arkansas Agricultural Experiment Station at Fayetteville. Plots of uniform slope were bordered to isolate surface runoff, fitted with runoff collectors, and established in fescue pasture. Suction lysimeters were placed at the 60 cm depth to sample soil water in the unsaturated zone. Caged layer manure was analyzed for cyromazine concentration and applied to the plots at three different rates. Rainfall was applied by simulator at two intensities. Surface runoff and lysimeter samples were measured and analyzed for cyromazine concentration. A solid phase extraction procedure was used to separate the cyromazine from the water samples and analysis was done by high performance liquid chromatography (HPLC). Results showed that a heavier manure application increased both the runoff and cyromazine concentration. Higher rainfall intensity also increased total cyromazine loss in the runoff, but provided enough runoff volume to decrease the cyromazine concentration. Soil water from the unsaturated zone was monitored for a year following the manure application, but neither cyromazine nor its metabolite, melamine, were detected
Evaluation of the Water Quality Impacts of Land Application of Poultry Litter
Evaluating the effect of land application of animal waste on water quality is fraught with inherent variability due to differing infiltration rates, slope, rainfall intensity and etc . Simulated rainfall technology has been used in erosion research for decades. Generally, this technology is used on plots of sufficient size (25 x 5 m) to develop rill and interrill erosion. The object of this investigation was to adapt and modify existing rainfall simulation technology used in soil erosion research for use in evaluating water quality impacts of land application of animal waste, and to test, evaluate and demonstrate it\u27s scientific validity. State of the art simulation technology was obtained from the National Soil Erosion Research Laboratory located on the campus of Purdue University. The technology was scaled (2 x 6 m) and modified to fit into field research programs having several treatments and rep 1 i cated p 1 ots . The technology was shown to meet specification needed to produce the required raindrop size and velocity, flexibility in storm intensity, while maintaining uniformity(\u3e 0.8). Equally important, the unit is portable and fits well into labor intensive runoff work requiring replication of a variety of treatments
Approach to the Continuum Limit of the Quenched Hermitian Wilson-Dirac Operator
We investigate the approach to the continuum limit of the spectrum of the
Hermitian Wilson-Dirac operator in the supercritical mass region for pure gauge
SU(2) and SU(3) backgrounds. For this we study the spectral flow of the
Hermitian Wilson-Dirac operator in the range . We find that the
spectrum has a gap for and that the spectral density at zero,
, is non-zero for . We find that and, for
(exponential in the lattice spacing) as one goes to
the continuum limit. We also compute the topological susceptibility and the
size distribution of the zero modes. The topological susceptibility scales well
in the lattice spacing for both SU(2) and SU(3). The size distribution of the
zero modes does not appear to show a peak at a physical scale.Comment: 19 pages revtex with 9 postscript figures included by eps
Filtering device
An electrical filter for removing noise from a voice communications signal is reported; seven sample values of the signal are obtained continuously, updated and subjected to filtering. Filtering is accomplished by adding balanced, with respect to a mid-point sample, spaced pairs of the sampled values, and then multiplying each pair by a selected filter constant. The signal products thus obtained are summed to provide a filtered version of the original signal
Two-dimensional convolute integers for optical image data processing and surface fitting
An approach toward low-pass, high-pass and band-pass filtering is presented. Convolution coefficients possessing the filtering speed associated with a moving smoothing average without suffering a loss of resolution are discussed. Resolution was retained because the coefficients represented the equivalance of applying high order two-dimensional regression calculations to an image without considering the time-consuming summations associated with the usual normal equations. The smoothing (low-pass) and roughing (high-pass) aspects of the filters are a result of being derived from regression theory. The coefficients are universal integer valves completely described by filter size and surface order, and possess a number of symmetry properties. Double convolution lead to a single set of coefficients with an expanded mask which can yield band-pass filtering and the surface normal. For low order surfaces (0,1), the two-dimensional convolute integers were equivalent to a moving smoothing average
Scaling Properties of Paths on Graphs
Let be a directed graph on finitely many vertices and edges, and assign a
positive weight to each edge on . Fix vertices and and consider the
set of paths that start at and end at , self-intersecting in any number
of places along the way. For each path, sum the weights of its edges, and then
list the path weights in increasing order. The asymptotic behaviour of this
sequence is described, in terms of the structure and type of strongly connected
components on the graph. As a special case, for a Markov chain the asymptotic
probability of paths obeys either a power law scaling or a weaker type of
scaling, depending on the structure of the transition matrix. This generalizes
previous work by Mandelbrot and others, who established asymptotic power law
scaling for special classes of Markov chains.Comment: 23 pages, 2 figure
Bayesian Model Comparison and Analysis of the Galactic Disk Population of Gamma-Ray Millisecond Pulsars
Pulsed emission from almost one hundred millisecond pulsars (MSPs) has been
detected in -rays by the Fermi Large-Area Telescope. The global
properties of this population remain relatively unconstrained despite many
attempts to model their spatial and luminosity distributions. We perform here a
self-consistent Bayesian analysis of both the spatial distribution and
luminosity function simultaneously. Distance uncertainties, arising from errors
in the parallax measurement or Galactic electron-density model, are
marginalized over. We provide a public Python package for calculating distance
uncertainties to pulsars derived using the dispersion measure by accounting for
the uncertainties in Galactic electron-density model YMW16. Finally, we use
multiple parameterizations for the MSP population and perform Bayesian model
comparison, finding that a broken power law luminosity function with Lorimer
spatial profile are preferred over multiple other parameterizations used in the
past. The best-fit spatial distribution and number of -ray MSPs is
consistent with results for the radio population of MSPs.Comment: 13 pages, 8 figures, 3 tables + Appendix. Public code and source list
available from http://github.com/tedwards2412/MSPDis
A deductive statistical mechanics approach for granular matter
We introduce a deductive statistical mechanics approach for granular
materials which is formally built from few realistic physical assumptions. The
main finding is an universal behavior for the distribution of the density
fluctuations. Such a distribution is the equivalent of the Maxwell-Boltzmann's
distribution in the kinetic theory of gasses. The comparison with a very
extensive set of experimental and simulation data for packings of monosized
spherical grains, reveals a remarkably good quantitative agreement with the
theoretical predictions for the density fluctuations both at the grain level
and at the global system level. Such agreement is robust over a broad range of
packing fractions and it is observed in several distinct systems prepared by
using different methods. The equilibrium distributions are characterized by
only one parameter () which is a quantity very sensitive to changes in the
structural organization. The thermodynamical equivalent of and its relation
with the `granular temperature' are also discussed.Comment: 15 pages, 6 figure
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