1,160 research outputs found
Topological solitons in highly anisotropic two dimensional ferromagnets
e study the solitons, stabilized by spin precession in a classical
two--dimensional lattice model of Heisenberg ferromagnets with non-small
easy--axis anisotropy. The properties of such solitons are treated both
analytically using the continuous model including higher then second powers of
magnetization gradients, and numerically for a discrete set of the spins on a
square lattice. The dependence of the soliton energy on the number of spin
deviations (bound magnons) is calculated. We have shown that the
topological solitons are stable if the number exceeds some critical value
. For and the intermediate values of anisotropy
constant ( is an exchange constant), the soliton
properties are similar to those for continuous model; for example, soliton
energy is increasing and the precession frequency is decreasing
monotonously with growth. For high enough anisotropy we found some fundamentally new soliton features absent for continuous
models incorporating even the higher powers of magnetization gradients. For
high anisotropy, the dependence of soliton energy E(N) on the number of bound
magnons become non-monotonic, with the minima at some "magic" numbers of bound
magnons. Soliton frequency have quite irregular behavior with
step-like jumps and negative values of for some regions of . Near
these regions, stable static soliton states, stabilized by the lattice effects,
exist.Comment: 17 page
Topological phase separation in 2D quantum lattice Bose-Hubbard system away from half-filling
We suppose that the doping of the 2D hard-core boson system away from
half-filling may result in the formation of multi-center topological
inhomogeneity (defect) such as charge order (CO) bubble domain(s) with Bose
superfluid (BS) and extra bosons both localized in domain wall(s), or a {\it
topological} CO+BS {\it phase separation}, rather than an uniform mixed CO+BS
supersolid phase. Starting from the classical model we predict the properties
of the respective quantum system. The long-wavelength behavior of the system is
believed to remind that of granular superconductors, CDW materials, Wigner
crystals, and multi-skyrmion system akin in a quantum Hall ferromagnetic state
of a 2D electron gas. To elucidate the role played by quantum effects and that
of the lattice discreteness we have addressed the simplest nanoscopic
counterpart of the bubble domain in a checkerboard CO phase of 2D hc-BH square
lattice. It is shown that the relative magnitude and symmetry of
multi-component order parameter are mainly determined by the sign of the
and transfer integrals. In general, the topologically inhomogeneous phase
of the hc-BH system away from the half-filling can exhibit the signatures both
of , and symmetry of the off-diagonal order.Comment: 12 pages, 6 figure
Topological phase separation in 2D hard-core Bose-Hubbard system away from half-filling
We suppose that the doping of the 2D hard-core boson system away from
half-filling may result in the formation of multi-center topological defect
such as charge order (CO) bubble domain(s) with Bose superfluid (BS) and extra
bosons both localized in domain wall(s), or a {\it topological} CO+BS {\it
phase separation}, rather than an uniform mixed CO+BS supersolid phase.
Starting from the classical model we predict the properties of the respective
quantum system. The long-wavelength behavior of the system is believed to
remind that of granular superconductors, CDW materials, Wigner crystals, and
multi-skyrmion system akin in a quantum Hall ferromagnetic state of a 2D
electron gas.Comment: 6 pages, 1 figur
Methods and Processes of Developing the Strengthening the Reporting of Observational Studies in Epidemiology – Veterinary (STROBE-Vet) Statement
BACKGROUND
Reporting of observational studies in veterinary research presents challenges that often are not addressed in published reporting guidelines.
OBJECTIVE
To develop an extension of the STROBE (Strengthening the Reporting of Observational Studies in Epidemiology) statement that addresses unique reporting requirements for observational studies in veterinary medicine related to health, production, welfare, and food safety.
DESIGN
Consensus meeting of experts.
SETTING
Mississauga, Canada.
PARTICIPANTS
Seventeen experts from North America, Europe, and Australia.
METHODS
Experts completed a pre-meeting survey about whether items in the STROBE statement should be modified or added to address unique issues related to observational studies in animal species with health, production, welfare, or food safety outcomes. During the meeting, each STROBE item was discussed to determine whether or not rewording was recommended and whether additions were warranted. Anonymous voting was used to determine consensus.
RESULTS
Six items required no modifications or additions. Modifications or additions were made to the STROBE items 1 (title and abstract), 3 (objectives), 5 (setting), 6 (participants), 7 (variables), 8 (data sources/measurement), 9 (bias), 10 (study size), 12 (statistical methods), 13 (participants), 14 (descriptive data), 15 (outcome data), 16 (main results), 17 (other analyses), 19 (limitations), and 22 (funding).
CONCLUSION
The methods and processes used were similar to those used for other extensions of the STROBE statement. The use of this STROBE statement extension should improve reporting of observational studies in veterinary research by recognizing unique features of observational studies involving food-producing and companion animals, products of animal origin, aquaculture, and wildlife
Direct and indirect effects of interspecific competition in a highly partitioned guild of reef fishes
Competitive interactions and resource partitioning facilitate species coexistence in complex ecosystems. However, while pairwise interactions between ecologically similar species have been well studied, multi‐species competitive networks have received less attention. When interference competition between two species results in partitioning of resources, this may have indirect consequences for other species distributed along the same resource gradient. Here, we tested whether interference competition between two territorial damselfish influenced the fine‐scale species distributions of five other territorial damselfish in Kimbe Bay, Papua New Guinea. These species partition habitat across three reef zones—the flat, crest, and slope, with distinct patterns of distribution within these zones. We predicted the two species with similar distributions and microhabitat use, Pomacentrus adelus and Pomacentrus bankanensis, would display the greatest level of aggression toward one another. This was tested through an intruder experiment where stimulus fish were introduced into a resident's territory, which confirmed disproportionately high levels of interspecific aggression between these two species. We also predicted that the fine‐scale differences in the distribution of each species were maintained through multi‐species interference competition among neighboring species, with further indirect effects on species that did not directly interact. To test this, we conducted a large‐scale (22 × 10 m) experimental removal of the most abundant species, Po. adelus, and quantified the abundance and distribution of all territorial damselfish species for 6 months to a 25 cm resolution. The main direct competitor, Po. bankanensis, exhibited a marked increase in abundance and expanded its distribution (+1.33 m) to acquire the space previously occupied by Po. adelus. This competitive release triggered indirect effects on the distribution of other neighboring species further back on the reef flat, with Chrysiptera unimaculata moving into the zone formerly occupied by Po. bankanensis. This study indicates that the distinct distribution patterns among the reef crest species are linked to levels of interspecific agonistic behavior. We argue that the competitive release following the removal of a superior competitor resulted in both direct and indirect effects, with the immediate neighbor shifting into the newly available space, followed by successive shifts in species responding to the change in the distributions of their immediate neighbors
Managing Milk Composition: Maximizing Rumen Function
4 pp., 4 tables, 1 photoFeeding strategies that optimize rumen function also maximize milk production and milk component percentages and yield. This publication offers guidelines for feeding forage, grain protein and ration fiber to enhance rumen function
Inhomogeneity of the intrinsic magnetic field in superconducting YBa2Cu3OX compounds as revealed by rare-earth EPR-probe
X-band electron paramagnetic resonance on doped Er3+ and Yb3+ ions in
Y0.99(Yb,Er)0.01Ba2Cu3OX compounds with different oxygen contents in the wide
temperature range (4-120)K have been made. In the superconducting species, the
strong dependencies of the linewidth and resonance line position from the sweep
direction of the applied magnetic field are revealed at the temperatures
significantly below TC. The possible origins of the observed hysteresis are
analyzed. Applicability of the presented EPR approach to extract information
about the dynamics of the flux-line lattice and critical state parameters
(critical current density, magnetic penetration depth, and characteristic
spatial scale of the inhomogeneity) is discussedComment: 17 pages, 5 Figures. Renewed versio
Managing Milk Composition: Evaluating Herd Potential
4 pp., 4 tables, 2 photosBefore trying to alter and improve milk fat and protein production of a dairy herd, it is important to evaluate the herd's potential to respond to feed management changes. This publication offers some key points that can be used to help determine that potential
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