2,144 research outputs found
Simulation of a stationary dark soliton in a trapped zero-temperature Bose-Einstein condensate
We discuss a computational mechanism for the generation of a stationary dark
soliton, or black soliton, in a trapped Bose-Einstein condensate using the
Gross-Pitaevskii (GP) equation for both attractive and repulsive interaction.
It is demonstrated that the black soliton with a "notch" in the probability
density with a zero at the minimum is a stationary eigenstate of the GP
equation and can be efficiently generated numerically as a nonlinear
continuation of the first vibrational excitation of the GP equation in both
attractive and repulsive cases in one and three dimensions for pure harmonic as
well as harmonic plus optical-lattice traps. We also demonstrate the stability
of this scheme under different perturbing forces.Comment: 7 pages, 15 ps figures, Final version accepted in J Low Temp Phy
Performance of early weaned calves fed lasalocid
Twenty-two newborn, bull calves were used to determine the effects of
lasalocid on growth and feed intake of early-weaned calves from week 1 to 12.
Calves were assigned to lasalocid or control groups on day 3. Lasalocid-fed group
received lasalocid in milk from day 4 to 7 and in milk and pre-starter from days 7
to 14 and in starter feed from weeks 2 to 12. Lasalocid-fed calves had a
significantly higher feed consumption and greater weight gain than calves that did
not receive lasalocid. The difference became apparent only after 6 wk of age.
Lasalocid appears to be a beneficial feed additive for newborn calves
Performance of early weaned calves fed lasalocid
Twenty-two newborn, bull calves were used to determine the effects of lasalocid on growth and feed intake of early-weaned calves from week 1 to 12. Calves were assigned to lasalocid or control groups on day 3. Lasalocid-fed group received lasalocid in milk from day 4 to 7 and in milk and pre-starter from days 7 to 14 and in starter feed from weeks 2 to 12. Lasalocid-fed calves had a significantly higher feed consumption and greater weight gain than calves that did not receive lasalocid. The difference became apparent only after 6 wk of age. Lasalocid appears to be a beneficial feed additive for newborn calves.; Dairy Day, 1987, Kansas State University, Manhattan, KS, 1987
Effect of ruminal protozoa on performance of early-weaned calves
Twenty newborn bull calves assigned to two groups, protozoa-free or protozoa-inoculated, were used to determine the effects of ruminal protozoa on performance of early weaned calves. Calves in the protozoa group were inoculated via stomach tube with a suspension of ruminal protozoa at weekly intervals until a viable population was established. Calves were evaluated weekly for weight gain and feed intake. Feed intake and weight gain were not significantly different between the groups but tended to be higher in protozoa-inoculated than protozoa-free calves.; Dairy Day, 1987, Kansas State University, Manhattan, KS, 1987
Effect of route of administration of lasalocid on response of young dairy calves
Forty newborn bull calves were assigned to one of four feeding groups. The feeds
either contained lasalocid in milk (M), prestarter (PS), and starter (S); lasalocid in PS and S;
lasalocid in S only; or no lasalocid. Calves were fed M at 8% of birth weight (bw) daily and
offered PS to a maximum of 0.5 lb daily. When 0.5 lb of PS was consumed in one day the
calves were fed M at 4% of bw daily. They were weaned when they consumed dry feed at
the rate of 1.3% of bw. Daily feed intake and weekly weight gains of calves were evaluated.
Blood serum samples were used to evaluate blood metabolites at wk 4, 8, and 12. We
concluded that lasalocid in M, PS, and S supported greater feed efficiency and allowed earlier
weaning with less animal variation than when lasalocid was delivered in PS and S, only in S,
or not at all
Land-sparing agriculture sustains higher levels of avian functional diversity than land sharing
The ecological impacts of meeting rising demands for food production can potentially be mitigated by two competing land-use strategies: off-setting natural habitats through intensification of existing farmland (land sparing), or elevating biodiversity within the agricultural matrix via the integration of 'wildlife-friendly' habitat features (land sharing). However, a key unanswered question is whether sparing or sharing farming would best conserve functional diversity, which can promote ecosystem stability and resilience to future land-use change. Focusing on bird communities in tropical cloud forests of the Colombian Andes, we test the performance of each strategy in conserving functional diversity. We show that multiple components of avian functional diversity in farmland are positively related to the proximity and extent of natural forest. Using landscape and community simulations, we also show that land-sparing agriculture conserves greater functional diversity and predicts higher abundance of species supplying key ecological functions than land sharing, with sharing becoming progressively inferior with increasing isolation from remnant forest. These results suggest low-intensity agriculture is likely to conserve little functional diversity unless large blocks of adjacent natural habitat are protected, consistent with land sparing. To ensure the retention of functionally diverse ecosystems, we urgently need to implement mechanisms for increasing farmland productivity whilst protecting spared land
Wannier functions analysis of the nonlinear Schr\"{o}dinger equation with a periodic potential
In the present Letter we use the Wannier function basis to construct lattice
approximations of the nonlinear Schr\"{o}dinger equation with a periodic
potential. We show that the nonlinear Schr\"{o}dinger equation with a periodic
potential is equivalent to a vector lattice with long-range interactions. For
the case-example of the cosine potential we study the validity of the so-called
tight-binding approximation i.e., the approximation when nearest neighbor
interactions are dominant. The results are relevant to Bose-Einstein condensate
theory as well as to other physical systems like, for example, electromagnetic
wave propagation in nonlinear photonic crystals.Comment: 5 pages, 1 figure, submitted to Phys. Rev.
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Modeling software design diversity
Design diversity has been used for many years now as a means of achieving a degree of fault tolerance in software-based systems. Whilst there is clear evidence that the approach can be expected to deliver some increase in reliability compared with a single version, there is not agreement about the extent of this. More importantly, it remains difficult to evaluate exactly how reliable a particular diverse fault-tolerant system is. This difficulty arises because assumptions of independence of failures between different versions have been shown not to be tenable: assessment of the actual level of dependence present is therefore needed, and this is hard. In this tutorial we survey the modelling issues here, with an emphasis upon the impact these have upon the problem of assessing the reliability of fault tolerant systems. The intended audience is one of designers, assessors and project managers with only a basic knowledge of probabilities, as well as reliability experts without detailed knowledge of software, who seek an introduction to the probabilistic issues in decisions about design diversity
On the equivalence of the Einstein-Hilbert and the Einstein-Palatini formulations of general relativity for an arbitrary connection
In the framework of the Einstein-Palatini formalism, even though the
projective transformation connecting the arbitrary connection with the Levi
Civita connection has been floating in the literature for a long time and
perhaps the result was implicitly known in the affine gravity community, yet as
far as we know Julia and Silva were the first to realise its gauge character.
We rederive this result by using the Rosenfeld-Dirac-Bergmann approach to
constrained Hamiltonian systems and do a comprehensive self contained analysis
establishing the equivalence of the Einstein-Palatini and the metric
formulations without having to impose the gauge choice that the connection is
symmetric. We also make contact with the the Einstein-Cartan theory when the
matter Lagrangian has fermions.Comment: 18 pages. Slight change in the title and wording of some sections to
emphasize the main results. References added. Matches published versio
Vortex Reconnection as the Dissipative Scattering of Dipoles
We propose a phenomenological model of vortex tube reconnection at high
Reynolds numbers. The basic picture is that squeezed vortex lines, formed by
stretching in the region of closest approach between filaments, interact like
dipoles (monopole-antimonopole pairs) of a confining electrostatic theory. The
probability of dipole creation is found from a canonical ensemble spanned by
foldings of the vortex tubes, with temperature parameter estimated from the
typical energy variation taking place in the reconnection process. Vortex line
reshuffling by viscous diffusion is described in terms of directional
transitions of the dipoles. The model is used to fit with reasonable accuracy
experimental data established long ago on the symmetric collision of vortex
rings. We also study along similar lines the asymmetric case, related to the
reconnection of non-parallel vortex tubes.Comment: 8 pages, 3 postscript figure
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