402 research outputs found
FRW barotropic zero modes: Dynamical systems observability
The dynamical systems observability properties of barotropic bosonic and
fermionic FRW cosmological oscillators are investigated. Nonlinear techniques
for dynamical analysis have been recently developed in many engineering areas
but their application has not been extended beyond their standard field. This
paper is a small contribution to an extension of this type of dynamical systems
analysis to FRW barotropic cosmologies. We find that determining the Hubble
parameter of barotropic FRW universes does not allow the observability, i.e.,
the determination of neither the barotropic FRW zero mode nor of its derivative
as dynamical cosmological states. Only knowing the latter ones correspond to a
rigorous dynamical observability in barotropic cosmologyComment: 10 pages, 0 figure
Supersymmetry of FRW barotropic cosmologies
Barotropic FRW cosmologies are presented from the standpoint of
nonrelativistic supersymmetry. First, we reduce the barotropic FRW system of
differential equations to simple harmonic oscillator differential equations.
Employing the factorization procedure, the solutions of the latter equations
are divided into the two classes of bosonic (nonsingular) and fermionic
(singular) cosmological solutions. We next introduce a coupling parameter
denoted by K between the two classes of solutions and obtain barotropic
cosmologies with dissipative features acting on the scale factors and spatial
curvature of the universe. The K-extended FRW equations in comoving time are
presented in explicit form in the low coupling regime. The standard barotropic
FRW cosmologies correspond to the dissipationless limit K =0Comment: 6 page
Spectral parameter power series representation for Hill's discriminant
We establish a series representation of the Hill discriminant based on the
spectral parameter power series (SPPS) recently introduced by V. Kravchenko. We
also show the invariance of the Hill discriminant under a Darboux
transformation and employing the Mathieu case the feasibility of this type of
series for numerical calculations of the eigenspectrumComment: 13 pages, 2 figures, 19 references with titles, a few minor changes
in the tex
Supersymmetric free-damped oscillators: Adaptive observer estimation of the Riccati parameter
A supersymmetric class of free damped oscillators with three parameters has
been obtained in 1998 by Rosu and Reyes through the factorization of the Newton
equation. The supplementary parameter is the integration constant of the
general Riccati solution. The estimation of the latter parameter is performed
here by employing the recent adaptive observer scheme of Besancon et al., but
applied in a nonstandard form in which a time-varying quantity containing the
unknown Riccati parameter is estimated first. Results of computer simulations
are presented to illustrate the good feasibility of this approach for a case in
which the estimation is not easily accomplished by other meansComment: 8 pages, 6 figure
Supersymmetric Fokker-Planck strict isospectrality
I report a study of the nonstationary one-dimensional Fokker-Planck solutions
by means of the strictly isospectral method of supesymmetric quantum mechanics.
The main conclusion is that this technique can lead to a space-dependent
(modulational) damping of the spatial part of the nonstationary Fokker-Planck
solutions, which I call strictly isospectral damping. At the same time, using
an additive decomposition of the nonstationary solutions suggested by the
strictly isospectral procedure and by an argument of Englefield [J. Stat. Phys.
52, 369 (1988)], they can be normalized and thus turned into physical
solutions, i.e., Fokker-Planck probability densities. There might be
applications to many physical processes during their transient periodComment: revised version, scheduled for PRE 56 (1 August 1997) as a B
Gene expression profiling of Mycobacterium avium subsp. paratuberculosis in simulated multi-stress conditions and within THP-1 cells reveals a new kind of interactive intramacrophage behaviour
Recent studies have identified in Mycobacterium avium subsp. paratuberculosis (MAP), already known as a pathogen in ruminants, a potential zoonotic agent of some autoimmune diseases in humans. Therefore, considering the possible risk for public health, it is necessary a thorough understanding of MAP's gene expression during infection of human host as well as the identification of its immunogenic and/or virulence factors for the development of appropriate diagnostic and therapeutic tools.In order to characterize MAP's transcriptome during macrophage infection, we analyzed for the first time the whole gene expression of a human derived strain of MAP in simulated intraphagosomal conditions and after intracellular infection of the human macrophage cell line THP-1 by using the DNA-microarray technology. Results showed that MAP shifts its transcriptome to an adaptive metabolism for an anoxic environment and nutrient starvation. It up-regulates several response factors to oxidative stress or intracellular conditions and allows, in terms of transcription, a passive surface peptidoglycan spoliation within the macrophage along with an intensification of the anabolic activity for lipidic membrane structures.These results indicate a possible interactive system between MAP and its host cell based on the internal mimicry unlike other intracellular pathogens, bringing new hypothesis in the virulence and pathogenicity of MAP and its importance in human health
An amplitude-phase (Ermakov-Lewis) approach for the Jackiw-Pi model of bilayer graphene
In the context of bilayer graphene we use the simple gauge model of Jackiw
and Pi to construct its numerical solutions in powers of the bias potential V
according to a general scheme due to Kravchenko. Next, using this numerical
solutions, we develop the Ermakov-Lewis approach for the same model. This leads
us to numerical calculations of the Lewis-Riesenfeld phases that could be of
forthcoming experimental interest for bilayer graphene. We also present a
generalization of the Ioffe-Korsch nonlinear Darboux transformationComment: FTC, 11 pp, 5 figure
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