315 research outputs found
Bistability and chaos at low-level of quanta
We study nonlinear phenomena of bistability and chaos at a level of few
quanta. For this purpose we consider a single-mode dissipative oscillator with
strong Kerr nonlinearity with respect to dissipation rate driven by a
monochromatic force as well as by a train of Gaussian pulses. The quantum
effects and decoherence in oscillatory mode are investigated on the framework
of the purity of states and the Wigner functions calculated from the master
equation. We demonstrate the quantum chaotic regime by means of a comparison
between the contour plots of the Wigner functions and the strange attractors on
the classical Poincar\'e section. Considering bistability at low-limit of
quanta, we analyze what is the minimal level of excitation numbers at which the
bistable regime of the system is displayed? We also discuss the formation of
oscillatory chaotic regime by varying oscillatory excitation numbers at ranges
of few quanta. We demonstrate quantum-interference phenomena that are assisted
hysteresis-cycle behavior and quantum chaos for the oscillator driven by the
train of Gaussian pulses as well as we establish the border of
classical-quantum correspondence for chaotic regimes in the case of strong
nonlinearities.Comment: 10 pages, 14 figure
Dissipative Chaos in Quantum Distributions
We discuss some problems of dissipative chaos for open quantum systems in the
framework of semiclassical and quantum distributions. For this goal, we propose
a driven nonlinear oscillator with time-dependent coefficients, i.e. with
time-dependent Kerr-nonlinearity and time-modulated driving field. This model
showing both regular and chaotic dynamics in the classical limit is realized in
several experimental schemes. Quantum dissipative chaos is analyzed on the base
of numerical method of quantum trajectories. Three quantities are studied: the
Wigner function of oscillatory mode from the point of view of quantum-assemble
theory and both semiclassical Poincare section and quantum Poincare section
calculated on a single quantum trajectory. The comparatively analysis of these
distributions for various operational chaotic regimes of the models is
performed, as well as scaling invariance in dissipative chaos and quantum
interference effects assisted by chaos are discussed.Comment: 17 pages, 3 figures, proceeding of Modern Optics And Photonic
Electrical conductivity of warm neutron star crust in magnetic fields: Neutron-drip regime
We compute the anisotropic electrical conductivity tensor of the inner crust
of a compact star at non-zero temperature by extending a previous work on the
conductivity of the outer crust. The physical scenarios, where such crust is
formed, involve proto-neutron stars born in supernova explosions, binary
neutron star mergers and accreting neutron stars. The temperature-density range
studied covers the transition from a non-degenerate to a highly degenerate
electron gas and assumes that the nuclei form a liquid, i.e., the temperature
is above the melting temperature of the lattice of nuclei. The electronic
transition probabilities include (a) the dynamical screening of electron-ion
interaction in the hard-thermal-loop approximation for the QED plasma, (b) the
correlations of the ionic component in a one-component plasma, and (c) finite
nuclear size effects. The conductivity tensor is obtained from the Boltzmann
kinetic equation in relaxation time approximation accounting for the
anisotropies introduced by a magnetic field. The sensitivity of the results
towards the matter composition of the inner crust is explored by using several
compositions of the inner crust which were obtained using different nuclear
interactions and methods of solving the many-body problem. The standard
deviation of relaxation time and components of the conductivity tensor from the
average are below except close to crust-core transition, where
non-spherical nuclear structures are expected. Our results can be used in
dissipative magneto-hydrodynamics (MHD) simulations of warm compact stars
Quantum interference and sub-Poissonian statistics for time-modulated driven dissipative nonlinear oscillator
We show that quantum-interference phenomena can be realized for the
dissipative nonlinear systems exhibiting hysteresis-cycle behavior and quantum
chaos. Such results are obtained for a driven dissipative nonlinear oscillator
with time-dependent parameters and take place for the regimes of long time
intervals exceeding dissipation time and for macroscopic levels of oscillatory
excitation numbers. Two schemas of time modulation: (i) periodic variation of
the strength of the {\chi}(3) nonlinearity; (ii) periodic modulation of the
amplitude of the driving force, are considered. These effects are obtained
within the framework of phase-space quantum distributions. It is demonstrated
that the Wigner functions of oscillatory mode in both bistable and chaotic
regimes acquire negative values and interference patterns in parts of
phase-space due to appropriately time-modulation of the oscillatory nonlinear
dynamics. It is also shown that the time-modulation of the oscillatory
parameters essentially improves the degree of sub-Poissonian statistics of
excitation numbers
Three-photon states in nonlinear crystal superlattices
It has been a longstanding goal in quantum optics to realize controllable
sources generating joint multiphoton states, particularly, photon triplet with
arbitrary spectral characteristics. We demonstrate that such sources can be
realized via cascaded parametric down-conversion (PDC) in superlattice
structures of nonlinear and linear segments. We consider scheme that involves
two parametric processes: ,
under pulsed pump and investigate
spontaneous creation of photon triplet as well as generation of high-intensity
mode in intracavity three-photon splitting. We show preparation of
Greenberger-Horne-Zeilinger polarization entangled states in cascaded type-II
and type-I PDC in framework of consideration dual-grid structure that involves
two periodically-poled crystals. We demonstrate the method of compensation of
the dispersive effects in non-linear segments by appropriately chosen linear
dispersive segments of superlattice for preparation heralded joint states of
two polarized photons. In the case of intracavity three-photon splitting, we
concentrate on investigation of photon-number distributions, third-order
photon-number correlation function as well as the Wigner functions. These
quantities are observed both for short interaction time intervals and in over
transient regime, when dissipative effects are essential.Comment: 15 pages, 6 figure
The composition of peripheral immunocompetent cell subpopulations and cytokine content in the brain structures of mutant Disc1-Q31L mice
The DISC1 (disrupted in sсhizophrenia 1) gene is associated with brain dysfunctions, which are involved in a variety of mental disorders, such as schizophrenia, depression and bipolar disorder. This is the first study to examine the immune parameters in Disc1-Q31L mice with a point mutation in the second exon of the DISC1 gene compared to mice of the C57BL/6NCrl strain (WT, wild type). A flow cytometry assay has shown that intact Disc1-Q31L mice differ from the WT strain by an increase in the percentage of CD3+ T cells, CD3+CD4+ Т helper cells and CD3+CD4+CD25+ T regulatory cells and a decrease in CD3+CD8+ T cytotoxic/suppressor cells in the peripheral blood. A multiplex analysis revealed differences in the content of cytokines in the brain structures of Disc1-Q31L mice compared to WT mice. The content of pro-inflammatory cytokines was increased in the frontal cortex (IL-6, IL- 17 and IFNγ) and striatum (IFNγ), and decreased in the hippocampus and hypothalamus. At the same time, the levels of IL-1β were decreased in all structures being examined. In addition, the content of anti-inflammatory cytokines IL-4 was increased in the frontal cortex, while IL-10 amount was decreased in the hippocampus. Immune response to sheep red blood cells analyzed by the number of antibody-forming cells in the spleen was higher in Disc1-Q31L mice at the peak of the reaction than in WT mice. Thus, Disc1-Q31L mice are characterized by changes in the pattern of cytokines in the brain structures, an amplification of the peripheral T-cell link with an increase in the content of the subpopulations of CD3+CD4+ T helpers and CD3+CD4+CD25+ T regulatory cells, as well as elevated immune reactivity to antigen in the spleen
BioProject and BioSample databases at NCBI: facilitating capture and organization of metadata
As the volume and complexity of data sets archived at NCBI grow rapidly, so does the need to gather and organize the associated metadata. Although metadata has been collected for some archival databases, previously, there was no centralized approach at NCBI for collecting this information and using it across databases. The BioProject database was recently established to facilitate organization and classification of project data submitted to NCBI, EBI and DDBJ databases. It captures descriptive information about research projects that result in high volume submissions to archival databases, ties together related data across multiple archives and serves as a central portal by which to inform users of data availability. Concomitantly, the BioSample database is being developed to capture descriptive information about the biological samples investigated in projects. BioProject and BioSample records link to corresponding data stored in archival repositories. Submissions are supported by a web-based Submission Portal that guides users through a series of forms for input of rich metadata describing their projects and samples. Together, these databases offer improved ways for users to query, locate, integrate and interpret the masses of data held in NCBI's archival repositories. The BioProject and BioSample databases are available at http://www.ncbi.nlm.nih.gov/bioproject and http://www.ncbi.nlm.nih.gov/biosample, respectively
- …