1,391 research outputs found
Comparative efficacy of two Ivermectin Pour-on anthelmintics in beef steers in a commercial feedyard
Generic products generally have a cost advantage for beef producers over brand-name products. Recently, many beef producers have debated whether to utilize generic anthelmintics in cow/calf herds and feeder cattle. If generics are to be justified, the products must be proven to have efficacy similar to the brand-name product. Previous studies have indicated that generic macrocyclic lactones are less effective in controlling gastrointestinal parasites of cattle than the original brand-name products. The objective of this study was to compare the efficacy of Vetrimec (Norbrook Laboratories Limited, Newry, Co. Down, Northern Ireland) pour-on and Ivomec (Merial Animal Health, Duluth, GA) pour-on by utilizing the fecal egg reduction test in newly arrived feedlot steers
Heavy Quark Solitons in the Nambu--Jona-Lasinio Model
The Nambu--Jona-Lasinio model (NJL) is extended to incorporate heavy quark
spin-symmetry. In this model baryons containing one heavy quark are analyzed as
bound-states of light baryons, represented as chiral solitons, and mesons
containing one heavy quark. From related studies in Skyrme type models, the
ground-state heavy baryon is known to arise for the heavy meson in a P--wave
configuration. In the limit of an infinitely large quark mass the heavy meson
wave-function is sharply peaked at the center of the chiral soliton. Therefore
the bound state equation reduces to an eigenvalue problem for the coefficients
of the operators contained in the most general P-wave {\it ansatz} for the
heavy meson. Within the NJL model a novel feature arises from the coupling of
the heavy meson to the various light quark states. In this respect conceptual
differences to Skyrme model calculations are discovered: The strongest bound
state is given by a heavy meson configuration which is completely decoupled
from the grand spin zero channel of the light quarks.Comment: 16 pages REVTEX, one postscript figure, to appear in Phys. Rev.
On Size and Shape of the Average Meson Fields in the Semibosonized Nambu & Jona-Lasinio Model
We consider a two-flavor Nambu \& Jona-Lasinio model in Hartree approximation
involving scalar-isoscalar and pseudoscalar-isovector quark-quark interactions.
Average meson fields are defined by minimizing the effective Euklidean action.
The fermionic part of the action, which contains the full Dirac sea, is
regularized within Schwinger's proper-time scheme. The meson fields are
restricted to the chiral circle and to hedgehog configurations. The only
parameter of the model is the constituent quark mass which simultaneously
controls the regularization. We evaluate meson and quark fields
self-consistently in dependence on the constituent quark mass. It is shown that
the self-consistent fields do practically not depend on the constituent quark
mass. This allows us to define a properly parameterized reference field which
for physically relevant constituent masses can be used as a good approximation
to the exactly calculated one. The reference field is chosen to have correct
behaviour for small and large radii. To test the agreement between
self-consistent and reference fields we calculate several observables like
nucleon energy, mean square radius, axial-vector constant and delta-nucleon
mass splitting in dependence on the constituent quark mass. The agreement is
found to be very well. Figures available on request.Comment: 12 pages (LATEX), 3 figures available on request, report FZR 93-1
Cattle handling technique can induce fatigued cattle syndrome in cattle not fed a beta adrenergic agonist
Citation: Frese, D. A., Reinhardt, C. D., Bartle, S. J., Rethorst, D. N., Hutcheson, J. P., Nichols, W. T., . . . Thomson, D. U. (2016). Cattle handling technique can induce fatigued cattle syndrome in cattle not fed a beta adrenergic agonist. Journal of Animal Science, 94(2), 581-591. doi:10.2527/jas2015-9824Angus crossbred steers (n = 40; 563 +/- 44 kg) were used to examine the effects of handling method and fat thickness on the blood chemistry and physiology of market steers. Steers were blocked by backfat (BF) thickness and were randomly assigned to treatment groups: low-stress handling (LSH) and aggressive handling (AH). Cattle were then ran-domly assigned to one of 5 blocks containing 4 steers from the LSH and AH treatments. Steers in the LSH treatment were walked and AH cattle were run through a course of 1,540 m. Blood samples were obtained via jugular venipuncture before handling (BASE), at 770 m (LAP1), at 1,540 m (LAP2), and at1 h (1H) and 2 h (2H) after finishing the course. Blood samples were analyzed for plasma lactate (LAC), creatinine kinase (CK), base excess (BE), blood pH (pH), serum cortisol (CORT) concentrations, and venous carbon dioxide (PvCO2) and oxygen (PvO2) pressures. Heart rate (HR), respiratory rate (RR), and rectal temperature (TEMP) were measured at the same intervals. Cattle in the AH treatment had greater (P 0.14). Blood pH in AH cattle was decreased compared with that in LSH cattle (P 0.13) at BASE, 1H, or 2H. Heart rate and TEMP were increased in AH cattle compared to LSH (P > 0.01). Serum cortisol was increased (P < 0.05) in AH compared to that in LSH cattle at LAP1 (87.5 vs. 58.9 nmol/ L), LAP2 (144.4 vs. 93.1 nmol/ L), and 1H (113.5 vs. 53.1 nmol/ L). Although RR was not differ-ent between LSH and AH, PvCO2 was decreased in AH compared to that in LSH (P < 0.05) at LAP2 (30.6 vs. 39.3 mmHg) and PvO2 was increased at LAP1 (42.7 vs. 33.5 mmHg) and at LAP2 (51.5 vs. 36.6 mmHg). Lactate was increased in AH cattle in the thicker BF group at 1H (P < 0.05), and blood pH was decreased at LAP1, LAP2, and 1H (P < 0.05) compared to the thinner BF cohorts. Four AH steers became exhausted (EXH) and did not complete the course. Increased CK, decreased PvCO2, and muscle tremors occurred in EXH steers compared to non-exhausted AH cohorts. Results of this study show that AH causes physiologic and blood chemistry changes in steers, which can be potentially detrimental to cattle, emphasizing the need for lowstress handling practices
Slavnov-Taylor identities in Coulomb gauge Yang-Mills theory
The Slavnov-Taylor identities of Coulomb gauge Yang-Mills theory are derived
from the (standard, second order) functional formalism. It is shown how these
identities form closed sets from which one can in principle fully determine the
Green's functions involving the temporal component of the gauge field without
approximation, given appropriate input.Comment: 20 pages, no figure
Chiral quark-soliton model in the Wigner-Seitz approximation
In this paper we study the modification of the properties of the nucleon in
the nucleus within the quark-soliton model. This is a covariant, dynamical
model, which provides a non-linear representation of the spontaneously broken
SU(2)_L X SU(2)_R symmetry of QCD. The effects of the nuclear medium are
accounted for by using the Wigner-Seitz approximation and therefore reducing
the complex many-body problem to a simpler single-particle problem. We find a
minimum in the binding energy at finite density, a change in the isoscalar
nucleon radius and a reduction of the in-medium pion decay constant. The latter
is consistent with a partial restoration of chiral symmetry at finite density,
which is predicted by other models.Comment: 30 pages, 13 figures; uses REVTeX and epsfi
On the problem of interactions in quantum theory
The structure of representations describing systems of free particles in the
theory with the invariance group SO(1,4) is investigated. The property of the
particles to be free means as usual that the representation describing a
many-particle system is the tensor product of the corresponding single-particle
representations (i.e. no interaction is introduced). It is shown that the mass
operator contains only continuous spectrum in the interval
and such representations are unitarily equivalent to ones describing
interactions (gravitational, electromagnetic etc.). This means that there are
no bound states in the theory and the Hilbert space of the many-particle system
contains a subspace of states with the following property: the action of free
representation operators on these states is manifested in the form of different
interactions. Possible consequences of the results are discussed.Comment: 35 pages, Late
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