3,233 research outputs found
Quantum-classical transition of the escape rate of uniaxial antiferromagnetic particles in an arbitrarily directed field
Quantum-classical escape rate transition has been studied for uniaxial
antiferromagnetic particles with an arbitrarily directed magnetic field. In the
case that the transverse and longitudinal fileds coexist, we calculate the
phase boundary line between first- and second-order transitions, from which
phase diagrams can be obtained. It is shown that the effects of the applied
longitudinal magnetic field on quantum-classical transition vary greatly for
different relative magnitudes of the non-compensation.Comment: to be appeared in Phys. Rev.
Functions holomorphic along holomorphic vector fields
The main result of the paper is the following generalization of Forelli's
theorem: Suppose F is a holomorphic vector field with singular point at p, such
that F is linearizable at p and the matrix is diagonalizable with the
eigenvalues whose ratios are positive reals. Then any function that has
an asymptotic Taylor expansion at p and is holomorphic along the complex
integral curves of F is holomorphic in a neighborhood of p.
We also present an example to show that the requirement for ratios of the
eigenvalues to be positive reals is necessary
Hadronic Charmed Meson Decays Involving Tensor Mesons
Charmed meson decays into a pseudoscalar meson P and a tensor meson T are
studied. The charm to tensor meson transition form factors are evaluated in the
Isgur-Scora-Grinstein-Wise (ISGW) quark model. It is shown that the
Cabibbo-allowed decay is dominated by the
W-annihilation contribution and has the largest branching ratio in
decays. We argue that the Cabibbo-suppressed mode
should be suppressed by one order of magnitude relative to . When the finite width effect of the tensor resonances is taken
into account, the decay rate of is generally enhanced by a factor of
. Except for , the predicted branching ratios
of decays are in general too small by one to two orders of magnitude
compared to experiment. However, it is very unlikely that the
transition form factors can be enhanced by a factor of within the
ISGW quark model to account for the discrepancy between theory and experiment.
As many of the current data are still preliminary and lack sufficient statistic
significance, more accurate measurements are needed to pin down the issue.Comment: 11 page
Issues in forest restoration: Forest restoration treatments: Their effect on wildland fire suppression costs
We modeled the effects of proposed forest restoration treatments in Arizona's Four Forest Restoration Initiative (4FRI) on fire behavior characteristics and fire suppression costs. We found two significant factors that help explain total wildfire suppression costs: 1) distance from the wildfire to the wildland-urban interface and 2) the proportion of fires with high burn severity. Given our results, we estimate a range for wildland suppression costs at 825 per acre for the current conditions of the 4FRI landscape. After the proposed forest restoration treatments, the suppression costs should be reduced to 327 per acre for the same size fire
Quantum nucleation in ferromagnets with tetragonal and hexagonal symmetries
The phenomenon of quantum nucleation is studied in a ferromagnet in the
presence of a magnetic field at an arbitrary angle. We consider the
magnetocrystalline anisotropy with tetragonal symmetry and that with hexagonal
symmetry, respectively. By applying the instanton method in the
spin-coherent-state path-integral representation, we calculate the dependence
of the rate of quantum nucleation and the crossover temperature on the
orientation and strength of the field for a thin film and for a bulk solid. Our
results show that the rate of quantum nucleation and the crossover temperature
depend on the orientation of the external magnetic field distinctly, which
provides a possible experimental test for quantum nucleation in nanometer-scale
ferromagnets.Comment: 19 pages and 3 figures, Final version and accepted by Phys. Rev. B
(Feb. B1 2001
Dynamics of FitzHugh-Nagumo excitable systems with delayed coupling
Small lattices of nearest neighbor coupled excitable FitzHugh-Nagumo
systems, with time-delayed coupling are studied, and compared with systems of
FitzHugh-Nagumo oscillators with the same delayed coupling. Bifurcations of
equilibria in N=2 case are studied analytically, and it is then numerically
confirmed that the same bifurcations are relevant for the dynamics in the case
. Bifurcations found include inverse and direct Hopf and fold limit cycle
bifurcations. Typical dynamics for different small time-lags and coupling
intensities could be excitable with a single globally stable equilibrium,
asymptotic oscillatory with symmetric limit cycle, bi-stable with stable
equilibrium and a symmetric limit cycle, and again coherent oscillatory but
non-symmetric and phase-shifted. For an intermediate range of time-lags inverse
sub-critical Hopf and fold limit cycle bifurcations lead to the phenomenon of
oscillator death. The phenomenon does not occur in the case of FitzHugh-Nagumo
oscillators with the same type of coupling.Comment: accepted by Phys.Rev.
Gauged Lifshitz scalar field theories in two dimensions
We present two-dimensional gauged Lifshitz scalar field theories by
considering the duality relation between the source current and the Noether
current. Requiring the duality partially, we obtain a gauged model which
recovers the bosonized Schwinger model for the IR limit. For the exact duality,
however, the source current is not conserved, which means that the resulting
theory is anomalous, so that the number of degrees of freedom is increased. The
second model is consistently formulated by adding the Wess-Zumino type action
to maintain the gauge invariance.Comment: 11 page
Semi-supervised prediction of protein interaction sentences exploiting semantically encoded metrics
Protein-protein interaction (PPI) identification is an integral component of many biomedical research and database curation tools. Automation of this task through classification is one of the key goals of text mining (TM). However, labelled PPI corpora required to train classifiers are generally small. In order to overcome this sparsity in the training data, we propose a novel method of integrating corpora that do not contain relevance judgements. Our approach uses a semantic language model to gather word similarity from a large unlabelled corpus. This additional information is integrated into the sentence classification process using kernel transformations and has a re-weighting effect on the training features that leads to an 8% improvement in F-score over the baseline results. Furthermore, we discover that some words which are generally considered indicative of interactions are actually neutralised by this process
The in vitro effects of dehydroepiandrosterone on human osteoarthritic chondrocytes
AbstractObjective: To investigate the in vitro effects of dehydroepiandrosterone (DHEA) on human osteoarthritic chondrocytes.Design: Chondrocytes isolated from human osteoarthritic knee cartilage were three-dimensionally cultured in alginate beads, except for cell proliferation experiment. Cells were treated with DHEA in the presence or absence of IL-1β. The effects on chondrocytes were analyzed using a 3-(4,5-dimethylthiazol-2yl)-5-(3-carboxymethoxy-phenyl)-2-(4-sulfophenyl)-2H-tetrazolium inner salt (MTS) assay (for chondrocyte proliferation), a dimethylmethylene blue (DMB) assay (for glycosaminoglycan (GAG) synthesis), and an indole assay (for DNA amount). Gene expressions of type I and II collagen, metalloproteinase-1 and -3 (MMP-1 and -3), and tissue inhibitor of metalloproteinase-1 (TIMP-1) as well as the IL-1β-induced gene expressions of MMP-1 and -3 were analyzed by reverse transcription-polymerase chain reaction (RT-PCR). The protein synthesis of MMP-1 and -3 and TIMP-1 was determined by Western blotting.Results: The treatment of chondrocytes with DHEA did not affect chondrocyte proliferation or GAG synthesis up to 100μM of concentration. The gene expression of type II collagen increased in a dose-dependent manner, while that of type I decreased. DHEA suppressed the expression of MMP-1 significantly at concentrations exceeding 50μM. The gene expression of MMP-3 was also suppressed, but this was without statistical significance. The expression of TIMP-1 was significantly increased by DHEA at concentrations exceeding 10μM. The effects of DHEA on the gene expressions of MMP-1 and -3 were more prominent in the presence of IL-1β, in which DHEA suppressed not only MMP-1, but also MMP-3 at the lower concentrations, 10 and 50μM, respectively. Western blotting results were in agreement with RT-PCR, which indicates that DHEA acts at the gene transcription level.Conclusions: Our study demonstrates that DHEA has no toxic effect on chondrocytes up to 100μM of concentration and has an ability to modulate the imbalance between MMPs and TIMP-1 during OA at the transcription level, which suggest that it has a protective role against articular cartilage loss
A magnetization equation for non-equilibrium spin systems
A magnetization equation for a system of spins evolving non-adiabatically and
out of equilibrium is derived without specifying the internal interactions. For
relaxation processes, this equation provides a general form of magnetization
damping. A special case of the spin-spin exchange interaction is considered.Comment: 9 pages, LATEX file; talk given at Theory Canada III, June 13-16,
2007, University of Alberta, Edmonton; to appear in Canadian Journal of
Physic
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