Effect of Early Weaning on Feedlot Performance and Carcass Characteristics of High Growth Potential Feeder Calves

Steer and heifer calves produced at Ft. Meade were used to evaluate early weaning and accelerated feeding as a management tool when retaining ownership of calves. Calves were weaned at 5 1/2 (EM) or 7 mo (NW) of age and started immediately on a 60% grain feeding program. Slaughter dates represented mean calf ages of 385 or 425 days and days on feed ranged from 179 to 257 days. Range conditions were good and early weaning had little effect on calf weight at any point in the feeding period. Feeding high grain diets to EW calves did not have any detrimental effects on feedlot performance when compared to NW. Early weaned calves produced carcasses that were 5 lb. heavier (P\u3c.05) than carcasses from NW cattle but had no other effects on carcass traits. Days on feed affected marbling scores independently of calf age or weaning group. EW appears to be a useful tool for reducing marketing interval for retained ownership cattle and for improving marbling scores of cattle at young ages

Description of Equilibrium Chemistry During Soil-Water Transport

Description of soluble salt leaching through soils and into groundwaters has been the focus of several research studies in recent years (Tanji et al. 1972; Dutt at al. 1972; Oster and Rhoades 1975: Melamed et al. 1977; Jury at al. 1978). The simulation models produced by these investigators have involved various levels of sophistication in the description of the con-comitant processes of soil water transport and chemical reaction of solutes. Mechanistic water flow models (Melamed et al. 1977) often include empirical description of chemistry, while more complete soil chemistry description (Tanji et al. 1972; Dutt et al. 1972) has often been accompanied by a simple water flow model. The result of these facts has been the development of models limited in their transferability to other experimental cases, or models that sometimes produce questionable results when applied to situations for which they were not developed. With these considerations in mind, a detailed simulation model has been developed describing the one—dimensional soil water transport of several ionic species in the presence of chemical precipitation and dissolution and cation exchange. This paper describes the theoretical approaches taken, gives several examples of model validation, and then presents two hypothetical simulation cases that demonstrate model application. The specifics of structure, operation, and validation of this model with experimental data are explained elsewhere (Robbins 1979; Robbins et al. 1980a, b)

Calculating Cation Exchange in a Salt Transport Model

A cation exchange subroutine that can be expanded to include any number of cations was developed and interfaced with a water flow-salt transport model that also contained a lime and gypsum precipitation-dissolution chemistry subroutine. The exchange subroutine was required by the complete model to satisfactorily predict EC, SAR, and specific ion concentration changes with time and depth for a gypsiferous and a nongypsiferous soil irrigated with waters containing three different CaSO? concentrations at two leaching fractions. In his sudy, exchangeable Ca, Mg, Na, and K were considered. Exchangeable K was included for me with high exchangeable and soluble K soils and high K irrigation waters. The additional cation exchange coefficient values needed for K exchange and a method for their calculation is given

A Combined Salt Transport-Chemical Equilibrium Model for Calcareous and Gypsiferous Soils

Chemical precipitation-dissolution and cation exchange subroutines were interfaced with an existing water movement-salt transport model. Three model options available for testing the prediction of salt transport and storage were (i) individual ion transport without soil interaction, (ii) precipitation and dissolution of lime and gypsum during transport, and (iii) cation exchange in addition to the precipitation-dissolution reactions. The transport model also predicts relative crop growth and water uptake as affected by soil moisture and salinity. The chemical subroutine used by the second and third options calculated ionic activities, corrected for ionic strength and ion pair formation, and was used to calculate lime and gypsum precipitation and dissolution. Cation activities were also used to calculate Ca, Mg, Na, and K exchange equilibria by a method that allows for addition of any number of exchangeable cations. Values predicted by the three options for EC, SAR and Ca, Mg, Na, A, Cl, SO? and HCO? concentrations were compared to experimental data obtained from a lysimeter study and were only satisfactorily predicted when both chemical precipitations and cation exchange were considered for a gypsiferous and a nongypsiferous soil irrigated with a high, medium, and low CaSO? water at two leaching fractions

Optimal Energy Dissipation in Sliding Friction Simulations

Non-equilibrium molecular dynamics simulations, of crucial importance in sliding friction, are hampered by arbitrariness and uncertainties in the removal of the frictionally generated Joule heat. Building upon general pre-existing formulation, we implement a fully microscopic dissipation approach which, based on a parameter-free, non-Markovian, stochastic dynamics, absorbs Joule heat equivalently to a semi-infinite solid and harmonic substrate. As a test case, we investigate the stick-slip friction of a slider over a two-dimensional Lennard-Jones solid, comparing our virtually exact frictional results with approximate ones from commonly adopted dissipation schemes. Remarkably, the exact results can be closely reproduced by a standard Langevin dissipation scheme, once its parameters are determined according to a general and self-standing variational procedure

Schur Polynomials and the Yang-Baxter equation

We show that within the six-vertex model there is a parametrized Yang-Baxter equation with nonabelian parameter group GL(2)xGL(1) at the center of the disordered regime. As an application we rederive deformations of the Weyl character formule of Tokuyama and of Hamel and King.Comment: Revised introduction; slightly changed reference

Half-metallic antiferromagnets in thiospinels

We have theoretically designed the half-metallic (HM) antiferromagnets (AFMs) in thiospinel systems, $\rm Mn(CrV)S_{4}$ and $\rm Fe_{0.5}Cu_{0.5}(V_{0.5}Ti_{1.5})S_{4}$, based on the electronic structure studies in the local-spin-density approximation (LSDA). We have also explored electronic and magnetic properties of parent spinel compounds of the above systems; $\rm CuV_{2}S_{4}$ and $\rm CuTi_{2}S_{4}$ are found to be HM ferromagnets in their cubic spinel structures, while $\rm MnCr_{2}S_{4}$ is a ferrimagnetic insulator. We have discussed the feasibility of material synthesis of HM-AFM thiospinel systems.Comment: 4 pages, 5 figure

Wetting films on chemically heterogeneous substrates

Based on a microscopic density functional theory we investigate the morphology of thin liquidlike wetting films adsorbed on substrates endowed with well-defined chemical heterogeneities. As paradigmatic cases we focus on a single chemical step and on a single stripe. In view of applications in microfluidics the accuracy of guiding liquids by chemical microchannels is discussed. Finally we give a general prescription of how to investigate theoretically the wetting properties of substrates with arbitrary chemical structures.Comment: 56 pages, RevTeX, 20 Figure

Quantum mechanics on space with SU(2) fuzziness

Quantum mechanics of models is considered which are constructed in spaces with Lie algebra type commutation relations between spatial coordinates. The case is specialized to that of the group SU(2), for which the formulation of the problem via the Euler parameterization is also presented. SU(2)-invariant systems are discussed, and the corresponding eigenvalue problem for the Hamiltonian is reduced to an ordinary differential equation, as it is the case with such models on commutative spaces.Comment: 12 pages, no figs, LaTe