103,080 research outputs found
On the -Dirac Oscillator revisited
This Letter is based on the -Dirac equation, derived from the
-Poincar\'{e}-Hopf algebra. It is shown that the -Dirac
equation preserves parity while breaks charge conjugation and time reversal
symmetries. Introducing the Dirac oscillator prescription,
, in the -Dirac
equation, one obtains the -Dirac oscillator. Using a decomposition in
terms of spin angular functions, one achieves the deformed radial equations,
with the associated deformed energy eigenvalues and eigenfunctions. The
deformation parameter breaks the infinite degeneracy of the Dirac oscillator.
In the case where , one recovers the energy eigenvalues and
eigenfunctions of the Dirac oscillator.Comment: 5 pages, no figures, accepted for publication in Physics Letters
Effects of quantum deformation on the spin-1/2 Aharonov-Bohm problem
In this letter we study the Aharonov-Bohm problem for a spin-1/2 particle in
the quantum deformed framework generated by the -Poincar\'{e}-Hopf
algebra. We consider the nonrelativistic limit of the -deformed Dirac
equation and use the spin-dependent term to impose an upper bound on the
magnitude of the deformation parameter . By using the self-adjoint
extension approach, we examine the scattering and bound state scenarios. After
obtaining the scattering phase shift and the -matrix, the bound states
energies are obtained by analyzing the pole structure of the latter. Using a
recently developed general regularization prescription [Phys. Rev. D.
\textbf{85}, 041701(R) (2012)], the self-adjoint extension parameter is
determined in terms of the physics of the problem. For last, we analyze the
problem of helicity conservation.Comment: 12 pages, no figures, submitted for publicatio
Remarks on the Aharonov-Casher dynamics in a CPT-odd Lorentz-violating background
The Aharonov-Casher problem in the presence of a Lorentz-violating background
nonminimally coupled to a spinor and a gauge field is examined. Using an
approach based on the self-adjoint extension method, an expression for the
bound state energies is obtained in terms of the physics of the problem by
determining the self-adjoint extension parameter.Comment: Matches published versio
Safety of herbal medicinal products: Echinacea and selected alkylamides do not induce CYP3A4 mRNA expression
Copyright © 2011 Maryam Modarai et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.A major safety concern with the use of herbal medicinal products (HMP) is their interactions with conventional medicines, which are often mediated via the cytochrome P450 (CYP) system. Echinacea is a widely used over-the-counter HMP, with proven immunomodulatory properties. Its increasing use makes research into its safety an urgent concern. Previously, we showed that Echinacea extracts and its alkylamides (thought to be important for Echinacea's immunomodulatory activity) mildly inhibit the enzymatic activity of the main drug metabolising CYP isoforms, but to this date, there is insufficient work on its ability to alter CYP expression levels. We now report for the first time the effect of a commercial Echinacea extract (Echinaforce) and four Echinacea alkylamides on the transcription of the major drug metabolizing enzyme CYP3A4. HepG2 cells were exposed for 96 h to clinically relevant concentrations of Echinaforce (22, 11.6 and 1.16g mL-1) or the alkylamides (1.62 and 44 nM). CYP3A4 mRNA levels were quantified using real-time reverse transcription polymerase chain reaction (RT-PCR). Neither Echinaforce nor the alkylamides produced any significant changes in the steady-state CYP3A4 mRNA levels, under these conditions. In contrast, treatment with 50M rifampicin resulted in a 3.8-fold up-regulation over the vehicle control. We conclude that Echinaforce is unlikely to affect CYP3A4 transcriptional levels, even at concentrations which can inhibit the enzymatic activity of CYP3A4. Overall, our data provides further evidence for the lack of interactions between Echinacea and conventional drugs.Bioforce, Switzerland and the Maplethorpe Trust (University of London)
Thermodynamic Formalism for Topological Markov Chains on Borel Standard Spaces
We develop a Thermodynamic Formalism for bounded continuous potentials
defined on the sequence space , where is a general
Borel standard space. In particular, we introduce meaningful concepts of
entropy and pressure for shifts acting on and obtain the existence of
equilibrium states as additive probability measures for any bounded continuous
potential. Furthermore, we establish convexity and other structural properties
of the set of equilibrium states, prove a version of the
Perron-Frobenius-Ruelle theorem under additional assumptions on the regularity
of the potential and show that the Yosida-Hewitt decomposition of these
equilibrium states do not have a purely additive part.
We then apply our results to the construction of invariant measures of
time-homogeneous Markov chains taking values on a general Borel standard space
and obtain exponential asymptotic stability for a class of Markov operators. We
also construct conformal measures for an infinite collection of interacting
random paths which are associated to a potential depending on infinitely many
coordinates. Under an additional differentiability hypothesis, we show how this
process is related after a proper scaling limit to a certain infinite
dimensional diffusion.Comment: Accepted for publication in Discrete and Continuous Dynamical
Systems. 23 page
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