Forage Quality of Cool Season Pasture Species Under Two Rotational Grazing Height Regimes

To optimize animal and pasture performance in management intensive grazing systems, pasture production and quality often must be compromised. Rotationally-stocking pastures at slightly taller grazing heights can increase pasture productivity, but lower forage quality may limit animal performance. Our objective was to compare the forage quality of common cool season pasture species in the Northeastern U.S., under two rotational grazing regimes defined by slightly different grass heights

Min-oscillations in Escherichia coli induced by interactions of membrane-bound proteins

During division it is of primary importance for a cell to correctly determine the site of cleavage. The bacterium Escherichia coli divides in the center, producing two daughter cells of equal size. Selection of the center as the correct division site is in part achieved by the Min-proteins. They oscillate between the two cell poles and thereby prevent division at these locations. Here, a phenomenological description for these oscillations is presented, where lateral interactions between proteins on the cell membrane play a key role. Solutions to the dynamic equations are compared to experimental findings. In particular, the temporal period of the oscillations is measured as a function of the cell length and found to be compatible with the theoretical prediction.Comment: 17 pages, 5 figures. Submitted to Physical Biolog

Constraints on the Existence of Chiral Fermions in Interacting Lattice Theories

It is shown that an interacting theory, defined on a regular lattice, must have a vector-like spectrum if the following conditions are satisfied: (a)~locality, (b)~relativistic continuum limit without massless bosons, and (c)~pole-free effective vertex functions for conserved currents. The proof exploits the zero frequency inverse retarded propagator of an appropriate set of interpolating fields as an effective quadratic hamiltonian, to which the Nielsen-Ninomiya theorem is applied.Comment: LaTeX, 9 pages, WIS--93/56--JUNE--P

The steady-state of heterogeneous catalysis, studied by first-principles statistical mechanics

The turn-over frequency of the catalytic oxidation of CO at RuO2(110) was calculated as function of temperature and partial pressures using ab initio statistical mechanics. The underlying energetics of the gas-phase molecules, dissociation, adsorption, surface diffusion, surface chemical reactions, and desorption were obtained by all-electron density-functional theory. The resulting CO2 formation rate [in the full (T, p_CO, p_O2)-space], the movies displaying the atomic motion and reactions over times scales from picoseconds to seconds, and the statistical analyses provide insights into the concerted actions ruling heterogeneous catalysis and open thermodynamic systems in general.Comment: 4 pages including 3 figures, Related publications can be found at http://www.fhi-berlin.mpg.de/th/paper.htm

Response to Drought of White Clover Lines Selected for Different Stolon Morphologies

White clover (Trifolium repens L.) lines were selected from within large and small-leaved cultivars of Grasslands Kopu and Grasslands Tahora, respectively, for long or short internodes, and for high or low branching frequency from plants grown in sun and shade (50% full sunlight). Lines were compared for drought tolerance in a perennial ryegrass (Lolium perenne L.) sward in boxes. Prior to imposing drought branching frequency selections did not differ in branching frequency, although the low branching frequency selection had a higher percentage of rooted nodes. After an imposed drought treatment sun-selected lines grew better than shade-selected lines relative to their non-stressed controls suggesting that white clover selected under full-sun may be more drought-tolerant than lines selected in shade. Selections for different stolon morphologies did not differ in stolon and root growth at the end of the drought

Nonlocal lattice fermion models on the 2d torus

Abelian fermion models described by the SLAC action are considered on a finite 2d lattice. It is shown that modification of these models by introducing additional Pauli - Villars regularization supresses nonlocal effects and provides agreement with the continuum results in vectorial U(1) models. In the case of chiral fermions the phase of the determinant differs from the continuum one.Comment: 16 pages, LaTeX, 5 eps figures, uses epsf.sty, rotate.st

Hamiltonian domain wall fermions at strong coupling

We apply strong-coupling perturbation theory to gauge theories containing domain-wall fermions in Shamir's surface version. We construct the effective Hamiltonian for the color-singlet degrees of freedom that constitute the low-lying spectrum at strong coupling. We show that the effective theory is identical to that derived from naive, doubled fermions with a mass term, and hence that domain-wall fermions at strong coupling suffer both doubling and explicit breaking of chiral symmetry. Since we employ a continuous fifth dimension whose extent tends to infinity, our result applies to overlap fermions as well.Comment: Revtex, 21 pp. Some changes in Introduction, dealing with consistency with previous wor

Josephson current through a molecular transistor in a dissipative environment

We study the Josephson coupling between two superconductors through a single correlated molecular level, including Coulomb interaction on the level and coupling to a bosonic environment. All calculations are done to the lowest, i.e., the fourth, order in the tunneling coupling and we find a suppression of the supercurrent due to the combined effect of the Coulomb interaction and the coupling to environmental degrees of freedom. Both analytic and numerical results are presented.Comment: 11 pages, 6 figures, to appear in Phys. Rev. B; v3: several misprints corrected - in particular, sign inconsistencies throughout the paper should be fixe

The Evolution of Cosmic Magnetic Fields: From the Very Early Universe, to Recombination, to the Present

(abridged) A detailed examination of the evolution of stochastic magnetic fields between high cosmic temperatures and the present epoch is presented. A simple analytical model matching the results of the 3D MHD simulations allows for the prediction of present day magnetic field correlation lengths and energy. Our conclusions are multi fold. (a) Initial primordial fields with only a small amount of helicity are evolving into maximally helical fields. (b) There exists a correlation between the strength of the magnetic field, B, at the peak of it's spectrum and the location of the peak, given at the present epoch by: B ~ 5x10^{-12} (L/kpc) Gauss, where L is the correlation length determined by the initial magnetic field. (c) Concerning studies of generation of cosmic microwave background (CMBR) anisotropies due to primordial magnetic fields of B~10^{-9} Gauss on ~ 10 Mpc scales, such fields are not only impossible to generate in early causal magnetogenesis scenarios but also seemingly ruled out by distortions of the CMBR spectrum due to magnetic field dissipation on smaller scales and the overproduction of cluster magnetic fields. (d) The most promising detection possibility of CMBR distortions due to primordial magnetic fields may be on much smaller scales at higher multipoles l~10^6 where the signal is predicted to be the strongest. (e) It seems possible that magnetic fields in clusters of galaxies are entirely of primordial origin, without invoking dynamo amplification. Such fields would be of (pre-collapse) strength 10^{-12} - 10^{-11} Gauss with correlation lengths in the kpc range, and would also exist in voids of galaxies.Comment: 35 pages, 22 figures, revtex style, submitted to PR