325 research outputs found
Rotating vortex dipoles in ferromagnets
Vortex-antivortex pairs are localized excitations and have been found to be
spontaneously created in magnetic elements. In the case that the vortex and the
antivortex have opposite polarities the pair has a nonzero topological charge,
and it behaves as a rotating vortex dipole. We find theoretically, and confirm
numerically, the form of the energy as a function of the angular momentum of
the system and the associated rotation frequencies. We discuss the process of
annihilation of the pair which changes the topological charge of the system by
unity while its energy is monotonically decreasing. Such a change in the
topological charge affects profoundly the dynamics in the magnetic system. We
finally discuss the connection of our results with Bloch Points (BP) and the
implications for BP dynamics.Comment: 6 pages, 2 figure
Disorder-driven superconductor-normal metal phase transition in quasi-one-dimensional organic conductors
Effects of non-magnetic disorder on the critical temperature T_c and on
diamagnetism of quasi-one-dimensional superconductors are reported. The energy
of Josephson-coupling between wires is considered to be random, which is
typical for dirty organic superconductors. We show that this randomness
destroys phase coherence between wires and that T_c vanishes discontinuously at
a critical disorder-strength. The parallel and transverse components of the
penetration-depth are evaluated. They diverge at different critical
temperatures T_c^{(1)} and T_c, which correspond to pair-breaking and
phase-coherence breaking respectively. The interplay between disorder and
quantum phase fluctuations is shown to result in quantum critical behavior at
T=0, which manifests itself as a superconducting-normal metal phase transition
of first-order at a critical disorder strength.Comment: 12 pages, 3 figure
Fermion Analogy for Layered Superconducting Films in Parallel Magnetic Field
The equivalence between the Lawrence-Doniach model for films of extreme
type-II layered superconductors and a generalization of the back-scattering
model for spin-1/2 electrons in one dimension is demonstrated. This fermion
analogy is then exploited to obtain an anomalous tail for
the parallel equilibrium magnetization of the minimal double layer case in the
limit of high parallel magnetic fields for temperatures in the
critical regime.Comment: 11 pages of plain TeX, 1 postscript figur
Spin-Torque-Induced Rotational Dynamics of a Magnetic Vortex Dipole
We study, both experimentally and by numerical modeling, the magnetic
dynamics that can be excited in a magnetic thin-film nanopillar device using
the spin torque from a spatially localized current injected via a
10s-of-nm-diameter aperture. The current-driven magnetic dynamics can produce
large amplitude microwave emission at zero magnetic field, with a frequency
well below that of the uniform ferromagnetic resonance mode. Micromagnetic
simulations indicate that the physical origin of this efficient microwave
nano-oscillator is the nucleation and subsequent steady-state rotational
dynamics of a magnetic vortex dipole driven by the localized spin torque. These
results show this novel implementation of a spintronic nano-oscillator is a
promising candidate for microwave technology applications.Comment: 19 pages, 4 figures
Classical and relativistic dynamics of supersolids: variational principle
We present a phenomenological Lagrangian and Poisson brackets for obtaining
nondissipative hydrodynamic theory of supersolids. A Lagrangian is constructed
on the basis of unification of the principles of non-equilibrium thermodynamics
and classical field theory. The Poisson brackets, governing the dynamics of
supersolids, are uniquely determined by the invariance requirement of the
kinematic part of the found Lagrangian. The generalization of Lagrangian is
discussed to include the dynamics of vortices. The obtained equations of motion
do not account for any dynamic symmetry associated with Galilean or Lorentz
invariance. They can be reduced to the original Andreev-Lifshitz equations if
to require Galilean invariance. We also present a relativistic-invariant
supersolid hydrodynamics, which might be useful in astrophysical applications.Comment: 22 pages, changed title and content, added reference
Pharmacokinetic studies of new antiparkinsonian drug Rapitalam
The aim of this study was to investigate the pharmacokinetic parameters of the mGluR4 receptor blocker Rapitalam on rabbits. There was developed the method of the quantitative determination of Rapitalam in the blood plasma of rabbits using high performance liquid chromatography with tandem mass spectrometric detection. The study was performed on 12 rabbits (males, weighing between 3,300 to 3,500 g). In intragastric dosing of the substance was administered using a gastric tube in the form of suspension in water 0.9 mg/ml, 9 mg/ml, and 90 mg/ml at a dose of 0.3 mg/kg, 3 mg/kg and 30 mg/kg. The main pharmacokinetic parameters of the substance was established on rabbits that allow you to optimize the future use of it's as a potential drug for the treatment of Parkinson's diseas
The 3d-to-4s-by-2p highway to superconductivity in cuprates
High-temperature superconductors are nowadays found in great variety and hold
technological promise. It is still an unsolved mystery that the critical
temperature T_c of the basic cuprates is so high. The answer might well be
hidden in a conventional corner of theoretical physics, overlooked in the
recent hunt for exotic explanations of new effects in these materials. A
forgotten intra-atomic s-d two-electron exchange in the Cu atom is found to
provide a strong (~eV) electron pairing interaction. A
Bardeen-Cooper-Schrieffer approach can explain the main experimental
observations and predict the correct d_{x^2-y^2} symmetry of the gap.Comment: 4 pages, 3 figures, LaTeX2
Development and validation of methods of quantitative determination of the new antidiabetic drug in the blood plasma of rats by high performance liquid chromatography with mass spectrometric detection
We developed a method of quantification of the new antidiabetic drug 3-(1h-benzimidazole-2-yl)-1,2,2-trimethyl-cyclopentane-carbonic acid (c7070) in the blood plasma of rats by high-performance liquid chromatography with mass-spectrometric detectio
Study of dose-dependent effect of 2-ethyl-6-methyl-3 hydroxypyridine succinate on the contractile function of isolated rat heat
In experiments on the isolated rat heart there were studied the effects of different doses (21.43 mg/kg/day and 85 . 72 mg/kg/day) 2-ethyl-6-methyl-3 hydroxypy ridine succinate ("EkoPharmInvest", Russia), on the contractile function of isolated hearts subjected to prior doxorubicin model (20 mg/kg, intraperitoneal) of pathology. The dynamic of the power mechanisms of ion transport was evaluated by imposing high h eart rate (480 BPM) and increase concentration of Са2+ to 5 mmol in perfusat
Reflection of light and heavy holes from a linear potential barrier
In this paper we study reflection of holes in direct-band semiconductors from
the linear potential barrier. It is shown that light-heavy hole transformation
matrix is universal. It depends only on a dimensionless product of the light
hole longitudinal momentum and the characteristic length determined by the
slope of the potential and doesn't depend on the ratio of light and heavy hole
masses, provided this ratio is small. It is shown that the transformation
coefficient goes to zero both in the limit of small and large longitudinal
momenta, however the phase of a reflected hole is different in these limits. An
approximate analytical expression for the light-heavy hole transformation
coefficient is found.Comment: 6 pages, 2 figure
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