1,497 research outputs found
GRID PRICING FOR FED CATTLE: AN EMPIRICAL ANALYSIS
Weekly grid premium and discount price date for fed cattle have been collected over a 3-year period. The grid price data are combined with carcass data (2590 South Dakota slaughter steers) to investigate the variability in the average weekly carcass premium is affected by changes in packer-determined grid premiums and discounts on a weekly basis. The three-stage recursive model is then estimated using an autoregressive procedure. The results of the empirical analysis indicated that among all grid premiums and discounts, it is the choice-select discount that plays the dominant role in determining weekly changes in the average weekly carcass premium (discount).slaughter cattle, grid pricing, average pricing, value-based-marketing, Marketing,
Effect of pressure on the Raman modes of antimony
The effect of pressure on the zone-center optical phonon modes of antimony in
the A7 structure has been investigated by Raman spectroscopy. The A_g and E_g
frequencies exhibit a pronounced softening with increasing pressure, the effect
being related to a gradual suppression of the Peierls-like distortion of the A7
phase relative to a cubic primitive lattice. Also, both Raman modes broaden
significantly under pressure. Spectra taken at low temperature indicate that
the broadening is at least partly caused by phonon-phonon interactions. We also
report results of ab initio frozen-phonon calculations of the A_g and E_g mode
frequencies. Presence of strong anharmonicity is clearly apparent in calculated
total energy versus atom displacement relations. Pronounced nonlinearities in
the force versus displacement relations are observed. Structural instabilities
of the Sb-A7 phase are briefly addressed in the Appendix.Comment: 10 pages, 8 figure
Assembling the puzzle of superconducting elements: A Review
Superconductivity in the simple elements is of both technological relevance
and fundamental scientific interest in the investigation of superconductivity
phenomena. Recent advances in the instrumentation of physics under pressure
have enabled the observation of superconductivity in many elements not
previously known to superconduct, and at steadily increasing temperatures. This
article offers a review of the state of the art in the superconductivity of
elements, highlighting underlying correlations and general trends.Comment: Review, 10 pages, 11 figures, 97 references; to appear in Superc.
Sci. Techno
Chiral Lagrangian Parameters for Scalar and Pseudoscalar Mesons
The results of a high-statistics study of scalar and pseudoscalar meson
propagators in quenched lattice QCD are presented. For two values of lattice
spacing, ( fm) and 5.9 ( fm), we
probe the light quark mass region using clover improved Wilson fermions with
the MQA pole-shifting ansatz to treat the exceptional configuration problem.
The quenched chiral loop parameters and are determined
from a study of the pseudoscalar hairpin correlator. From a global fit to the
meson correlators, estimates are obtained for the relevant chiral Lagrangian
parameters, including the Leutwyler parameters and . Using the
parameters obtained from the singlet and nonsinglet pseudoscalar correlators,
the quenched chiral loop effect in the nonsinglet scalar meson correlator is
studied. By removing this QCL effect from the lattice correlator, we obtain the
mass and decay constant of the ground state scalar, isovector meson .Comment: 36 pages, 12 figures, LaTe
Low-energy couplings of QCD from current correlators near the chiral limit
We investigate a new numerical procedure to compute fermionic correlation
functions at very small quark masses. Large statistical fluctuations, due to
the presence of local ``bumps'' in the wave functions associated with the
low-lying eigenmodes of the Dirac operator, are reduced by an exact low-mode
averaging. To demonstrate the feasibility of the technique, we compute the
two-point correlator of the left-handed vector current with Neuberger fermions
in the quenched approximation, for lattices with a linear extent of L~1.5 fm, a
lattice spacing a~0.09 fm, and quark masses down to the epsilon-regime. By
matching the results with the corresponding (quenched) chiral perturbation
theory expressions, an estimate of (quenched) low-energy constants can be
obtained. We find agreement between the quenched values of F extrapolated from
the p-regime and extracted in the epsilon-regime.Comment: 20 pages, 5 figure
Defining Failure of Passive Transfer in South Dakota Beef Calves
Failure of calves to ingest and absorb immunoglobulin from colostrum is a risk factor for illness and decreased performance. Blood samples were taken from 752 calves at three SDSU research units. Total protein in blood, closely correlated to colostral immunoglobulin absorption, was determined and calf health records were collected. Using this data, a classification table of sensitivity and specificity was constructed to determine the relationship between total protein and calf illness and to classify calves as having adequate colostral absorption or inadequate colostral absorption (failure of passive transfer). Along with sensitivity and specificity, positive and negative likelihood ratios were calculated to identify a suitable cutoff point to separate calves that would become ill from those that would remain healthy. The cutoff point selected was a serum total protein level of 5.5 g/dL, which produced a sensitivity of 30% and specificity of 87%. Calves with total protein levels below 5.5 g1dL were 3.07 (95% CI 1.73-5.43, p=0.0002) times as likely to become ill as calves with total protein levels above 5.5 g/dL. In beef production situations similar to those in these herds, producers should be able to limit disease if calves\u27 total protein at 24 hours following birth is equal to or greater than 5.5 g/dL
Tunable Electron Multibunch Production in Plasma Wakefield Accelerators
Synchronized, independently tunable and focused J-class laser pulses are
used to release multiple electron populations via photo-ionization inside an
electron-beam driven plasma wave. By varying the laser foci in the laboratory
frame and the position of the underdense photocathodes in the co-moving frame,
the delays between the produced bunches and their energies are adjusted. The
resulting multibunches have ultra-high quality and brightness, allowing for
hitherto impossible bunch configurations such as spatially overlapping bunch
populations with strictly separated energies, which opens up a new regime for
light sources such as free-electron-lasers
Low-energy couplings of QCD from topological zero-mode wave functions
By matching 1/m^2 divergences in finite-volume two-point correlation
functions of the scalar or pseudoscalar densities with those obtained in chiral
perturbation theory, we derive a relation between the Dirac operator zero-mode
eigenfunctions at fixed non-trivial topology and the low-energy constants of
QCD. We investigate the feasibility of using this relation to extract the pion
decay constant, by computing the zero-mode correlation functions on the lattice
in the quenched approximation and comparing them with the corresponding
expressions in quenched chiral perturbation theory.Comment: 31 pages. v2: references and a small clarification added; published
versio
Superconductivity in the YIr2Si2 and LaIr2Si2 Polymorphs
We report on existence of superconductivity in YIr2Si2 and LaIr2Si2 compounds
in relation to crystal structure. The two compounds crystallize in two
structural polymorphs, both tetragonal. The high temperature polymorph (HTP)
adopts the CaBe2Ge2-structure type (space group P4/nmm) while the low
temperature polymorph (LTP) is of the ThCr2Si2 type (I4/mmm). By studying
polycrystals prepared by arc melting we have observed that the rapidly cooled
samples retain the HTP even at room temperature (RT) and below. Annealing such
samples at 900C followed by slow cooling to RT provides the LTP. Both, the HTP
and LTP were subsequently studied with respect to magnetism and
superconductivity by electrical resistivity, magnetization, AC susceptibility
and specific heat measurements. The HTP and LTP of both compounds respectively,
behave as Pauli paramagnets. Superconductivity has been found exclusively in
the HTP of both compounds below Tsc (= 2.52 K in YIr2Si2 and 1.24 K in
LaIr2Si2). The relations of magnetism and superconductivity with the electronic
and crystal structure are discussed with comparing experimental data with the
results of first principles electronic structure calculations
Leptonic Decays of Heavy Quarks on the Lattice
The status of lattice calculations of heavy-light decay constants and of the
parameter is reviewed. After describing the lattice approach to heavy
quark systems, the main results are discussed, with special emphasis on the
systematic errors in present lattice calculations. A detailed analysis of the
continuum limit for decay constants is performed. The implications of lattice
results on studies of CP violation in the Standard Model are discussed.Comment: Invited review to be published in Int. J. Mod. Phys. A, 63 pages,
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