598 research outputs found
Differential approximation for Kelvin-wave turbulence
I present a nonlinear differential equation model (DAM) for the spectrum of
Kelvin waves on a thin vortex filament. This model preserves the original
scaling of the six-wave kinetic equation, its direct and inverse cascade
solutions, as well as the thermodynamic equilibrium spectra. Further, I extend
DAM to include the effect of sound radiation by Kelvin waves. I show that,
because of the phonon radiation, the turbulence spectrum ends at a maximum
frequency where
is the total energy injection rate, is the speed of sound and
is the quantum of circulation.Comment: Prepared of publication in JETP Letter
Biexciton oscillator strength
Our goal is to provide a physical understanding of the elementary coupling
between photon and biexciton and to derive the physical characteristics of the
biexciton oscillator strength, following the procedure we used for trion.
Instead of the more standard two-photon absorption, this work concentrates on
molecular biexciton created by photon absorption in an exciton gas. We first
determine the appropriate set of coordinates in real and momentum spaces to
describe one biexciton as two interacting excitons. We then turn to second
quantization and introduce the "Fourier transform in the exciton sense" of the
biexciton wave function which is the relevant quantity for oscillator strength.
We find that, like for trion, the oscillator strength for the formation of one
biexciton out of one photon plus a \emph{single} exciton is extremely small: it
is one biexciton volume divided by one sample volume smaller than the exciton
oscillator strength. However, due to their quantum nature, trion and biexciton
have absorption lines which behave quite differently. Electrons and trions are
fermionic particles impossible to pile up all at the same energy. This would
make the weak trion line spread with electron density, the peak structure only
coming from singular many-body effects. By contrast, the bosonic nature of
exciton and biexciton makes the biexciton peak mainly rise with exciton
density, this rise being simply linear if we forget many-body effects between
the photocreated exciton and the excitons present in the sample
Pion and Sigma Polarizabilities and Radiative Transitions
Fermilab E781 plans measurements of gamma-Sigma and -pion
interactions using a 600 GeV beam of Sigmas and pions, and a virtual photon
target. Pion polarizabilities and radiative transitions will be measured in
this experiment. The former can test a precise prediction of chiral symmetry;
the latter for a_1(1260) ----> pi + gamma is important for understanding the
polarizability. The experiment also measures polarizabilities and radiative
transitions for Sigma hyperons. The polarizabilities can test predictions of
baryon chiral perturbation theory. The radiative transitions to the
Sigma*(1385) provide a measure of the magnetic moment of the s-quark. Previous
experimental and theoretical results for gamma-pi and gamma-Sigma interactions
are given. The E781 experiment is described.Comment: 13 pages text (tex), Tel Aviv U. Preprint TAUP 2204-94, uses
Springer-Verlag TEX macro package lecproc.cmm (appended at end of tex file,
following \byebye), which requires extracting lecproc.cmm and putting this
file in your directory in addition to the tex file (mmcd.tex) before tex
processing. lecproc.cmm should be used following instructions and guidelines
available from Springer-Verlag. Submitted to the Proceedings of Workshop on
Chiral Dynamics, Massachusetts Institute of Technology, July 1994, Eds. A.
Bernstein, B. Holstein. Replaced Oct. 4 to add TAUP preprint number. Replaced
Oct. 12 to correct Pb target thickness from 1.3% interaction to 0.3
Energy spectra of the ocean's internal wave field: theory and observations
The high-frequency limit of the Garrett and Munk spectrum of internal waves
in the ocean and the observed deviations from it are shown to form a pattern
consistent with the predictions of wave turbulence theory. In particular, the
high frequency limit of the Garrett and Munk spectrum constitutes an {\it
exact} steady state solution of the corresponding kinetic equation.Comment: 4 pages, one color figur
Manufacture of optical ceramics based on two solid solutions of the AgBr - (TlBr0.46I0.54) system
This work is devoted to the synthesis and the optical properties study of a new multicomponent heterophase ceramic based on two solid solutions of the AgBr - (TlBr0.46I0.54) system. Ceramics are transparent in the infrared range from 1.0 to 40.0 ÷ 50.0 μm, non-hygroscopic, are photo- and radiation-resistant, flexible, as a result of which various optical products are made from it by hot embossing. © Published under licence by IOP Publishing Ltd.This work was supported by the Russian Science Foundation under grant No. 18-73-10063
Kolmogorov turbulence, Anderson localization and KAM integrability
The conditions for emergence of Kolmogorov turbulence, and related weak wave
turbulence, in finite size systems are analyzed by analytical methods and
numerical simulations of simple models. The analogy between Kolmogorov energy
flow from large to small spacial scales and conductivity in disordered solid
state systems is proposed. It is argued that the Anderson localization can stop
such an energy flow. The effects of nonlinear wave interactions on such a
localization are analyzed. The results obtained for finite size system models
show the existence of an effective chaos border between the
Kolmogorov-Arnold-Moser (KAM) integrability at weak nonlinearity, when energy
does not flow to small scales, and developed chaos regime emerging above this
border with the Kolmogorov turbulent energy flow from large to small scales.Comment: 8 pages, 6 figs, EPJB style
Highly Transparent Ceramics for the Spectral Range from 1.0 to 60.0 μm Based on Solid Solutions of the System AgBr-AgI-TlI-TlBr
The article is devoted to the technology for obtaining optical ceramics of AgBr-TlI and AgBr-TlBr0.46I0.54 systems and manufacturing samples with different compositions. The new heterophase crystal ceramics are transparent without absorption windows in the spectral range from 1.0 to 60.0 μm. In the ceramics' transparency spectra based on the AgBr-TlI and AgBr-TlBr0.46I0.54 systems fusibility diagrams, with an increase in the thallium halides mass fraction, as well as the replacement of the bromine ion with iodine, the maximum transparency shifts to a long infrared region. © 2021 Chinese Optics Letters.This work was supported by the Russian Science Foundation (No. 18-73-10063)
Fluorescence and cytotoxicity of cadmium sulfide quantum dots stabilized on clay nanotubes
© 2018 by the authors. Licensee MDPI, Basel, Switzerland. Quantum dots (QD) are widely used for cellular labeling due to enhanced brightness, resistance to photobleaching, and multicolor light emissions. CdS and CdxZn1−xS nanoparticles with sizes of 6–8 nm were synthesized via a ligand assisted technique inside and outside of 50 nm diameter halloysite clay nanotubes (QD were immobilized on the tube’s surface). The halloysite– QD composites were tested by labeling human skin fibroblasts and prostate cancer cells. In human cell cultures, halloysite–QD systems were internalized by living cells, and demonstrated intense and stable fluorescence combined with pronounced nanotube light scattering. The best signal stability was observed for QD that were synthesized externally on the amino-grafted halloysite. The best cell viability was observed for CdxZn1−xS QD immobilized onto the azine-grafted halloysite. The possibility to use QD clay nanotube core-shell nanoarchitectures for the intracellular labeling was demonstrated. A pronounced scattering and fluorescence by halloysite–QD systems allows for their promising usage as markers for biomedical applications
Isolation of two strains of West Nile virus during an outbreak in southern Russia, 1999.
From July to September 1999, a widespread outbreak of meningoencephalitis associated with West Nile virus (Flavivirus, Flaviviridae) occurred in southern Russia, with hundreds of cases and dozens of deaths. Two strains of West Nile virus isolated from patient serum and brain-tissue samples reacted in hemagglutination-inhibition and neutralization tests with patients' convalescent-phase sera and immune ascites fluid from other strains of West Nile virus
Enhanced antibacterial activity of silver nanoparticles/halloysite nanotubes/graphene nanocomposites with sandwich-like structure
A sandwich-like antibacterial reagent (Ag/HNTs/rGO) was constructed through the direct growth of silver nanoparticles on the surface graphene-based HNTs nanosheets. Herein, various nanomaterials were combined by adhesion effect of DOPA after self-polymerization. Ag/HNTs/rGO posses enhanced antibacterial ability against E. coli and S. aureus compared with individual silver nanoparticles, rGO nanosheets or their nanocomposites
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