13,747 research outputs found
System Level Economic Analysis of Swine Diet Modifications
Experimental data from low nitrogen and phosphorus diets (Carter et al, 1999, 2000, 2003) are being used to validate and/or modify the NRC swine growth model. A profit maximizing daily growth model that considers feed costs, excretion, waste management costs, and length of feeding period is being developed.Livestock Production/Industries,
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Fractal scattering dynamics of the three-dimensional HOCl molecule
We compare the 2D and 3D classical fractal scattering dynamics of Cl and HO for energies just above dissociation of the HOCl molecule, using a realistic potential energy surface for the HOCl molecule and techniques developed to analyze 3D chaotic scattering processes. For parameter regimes where the HO dimer initially has small vibrational energy, only small intervals of initial conditions show fractal scattering behavior and the scattering process is well described by a 2D model. For parameter regimes where the HO dimer initially has large vibrational energy, the scattering process is fully 3D and is dominated by fractal behavior.Robert A. Welch Foundation F-1051CONACyT 79988DGAPA IN110110Physic
Superfluid shells for trapped fermions with mass and population imbalance
We map out the phase diagram of strongly interacting fermions in a potential
trap with mass and population imbalance between the two spin components. As a
unique feature distinctively different from the equal-mass case, we show that
the superfluid here forms a shell structure which is not simply connected in
space. Different types of normal states occupy the trap regions inside and
outside this superfluid shell. We calculate the atomic density profiles, which
provide an experimental signature for the superfluid shell structure.Comment: 4 pages, 3 figure
Signal of Bose condensation in an optical lattice at finite temperature
We discuss the experimental signal for the Bose condensation of cold atoms in
an optical lattice at finite temperature. Instead of using the visibility of
the interference pattern via the time-of-flight imaging, we show that the
momentum space density profile in the first Brillouin zone, in particular its
bimodal distribution, provides an unambiguous signal for the Bose condensation.
We confirm this point with detailed calculation of the change in the atomic
momentum distribution across the condensation phase transition, taking into
account both the global trapping potential and the atomic interaction effects.Comment: 4 pages, 2 figures, replaced with the published versio
Tunneling into Multiwalled Carbon Nanotubes: Coulomb Blockade and Fano Resonance
Tunneling spectroscopy measurements of single tunnel junctions formed between
multiwalled carbon nanotubes (MWNTs) and a normal metal are reported. Intrinsic
Coulomb interactions in the MWNTs give rise to a strong zero-bias suppression
of a tunneling density of states (TDOS) that can be fitted numerically to the
environmental quantum-fluctuation (EQF) theory. An asymmetric conductance
anomaly near zero bias is found at low temperatures and interpreted as Fano
resonance in the strong tunneling regime.Comment: 4 pages, 4 figure
Interaction induced ferro-electricity in the rotational states of polar molecules
We show that a ferro-electric quantum phase transition can be driven by the
dipolar interaction of polar molecules in the presence a micro-wave field. The
obtained ferro-electricity crucially depends on the harmonic confinement
potential, and the resulting dipole moment persists even when the external
field is turned off adiabatically. The transition is shown to be second order
for fermions and for bosons of a smaller permanent dipole moment, but is first
order for bosons of a larger moment. Our results suggest the possibility of
manipulating the microscopic rotational state of polar molecules by tuning the
trap's aspect ratio (and other mesoscopic parameters), even though the later's
energy scale is smaller than the former's by six orders of magnitude.Comment: 4 pages and 4 figure
The role of Rayleigh-Taylor instabilities in filament threads
Many solar filaments and prominences show short-lived horizontal threads
lying parallel to the photosphere. In this work the possible link between
Rayleigh-Taylor instabilities and thread lifetimes is investigated. This is
done by calculating the eigenmodes of a thread modelled as a Cartesian slab
under the presence of gravity. An analytical dispersion relation is derived
using the incompressible assumption for the magnetohydrodynamic (MHD)
perturbations. The system allows a mode that is always stable, independently of
the value of the Alfv\'en speed in the thread. The character of this mode
varies from being localised at the upper interface of the slab when the
magnetic field is weak, to having a global nature and resembling the transverse
kink mode when the magnetic field is strong. On the contrary, the slab model
permits another mode that is unstable and localised at the lower interface when
the magnetic field is weak. The growth rates of this mode can be very short, of
the order of minutes for typical thread conditions. This Rayleigh-Taylor
unstable mode becomes stable when the magnetic field is increased, and in the
limit of strong magnetic field it is essentially a sausage magnetic mode. The
gravity force might have a strong effect on the modes of oscillation of
threads, depending on the value of the Alfv\'en speed. In the case of threads
in quiescent filaments, where the Alfv\'en speed is presumably low, very short
lifetimes are expected according to the slab model. In active region
prominences, the stabilising effect of the magnetic tension might be enough to
suppress the Rayleigh-Taylor instability for a wide range of wavelengths
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