255 research outputs found
Strain-Compensated AlInGaAs-GaAsP Superlattices for Highly-Polarized Electron Emission
Spin-polarized electron emission from the first superlattice photocathodes
developed with strain compensation is investigated. An opposite strain in the
quantum well and barrier layers is complished using an InAlGaAs/GaAsP
superlattice structure. The measured values of maximum polarization and quantum
yield for the structure with a 0.18 um-thick working layer are close to the
best results reported for any strained superlattice photocathode structure,
demonstrating the high potential of strain compensation for future photocathode
applications. An analysis of the photoemission spectra is used to estimate the
parameters responsible for the polarization losses.Comment: 10 pages, 2 figure
Activation of phase boundary and current-generating processes in plasma-electrochemical systems
This paper reviews and presents the principles for implementing
Phase boundary texturing influence on laminated compound durability under local thermal effect
Destruction process modeling has been conducted for a laminated material under a local pointed thermal effect. Temperature field dependence on the coating surface texturing parameters has been studied. A mathematical model of the load distribution in the laminated material with wavy coating surface texturing under thermal effect is presented
Svortices and the fundamental modes of the "snake instability": Possibility of observation in the gaseous Bose-Einstein Condensate
The connection between quantized vortices and dark solitons in a long and
thin, waveguide-like trap geometry is explored in the framework of the
non-linear Schr\"odinger equation. Variation of the transverse confinement
leads from the quasi-1D regime where solitons are stable to 2D (or 3D)
confinement where soliton stripes are subject to a transverse modulational
instability known as the ``snake instability''. We present numerical evidence
of a regime of intermediate confinement where solitons decay into single,
deformed vortices with solitonic properties, also called svortices, rather than
vortex pairs as associated with the ``snake'' metaphor. Further relaxing the
transverse confinement leads to production of 2 and then 3 vortices, which
correlates perfectly with a Bogoliubov-de Gennes stability analysis. The decay
of a stationary dark soliton (or, planar node) into a single svortex is
predicted to be experimentally observable in a 3D harmonically confined dilute
gas Bose-Einstein condensate.Comment: 4 pages, 4 figure
On the motion of a heavy rigid body in an ideal fluid with circulation
Chaplygin's equations describing the planar motion of a rigid body in an
unbounded volume of an ideal fluid involved in a circular flow around the body
are considered. Hamiltonian structures, new integrable cases, and partial
solutions are revealed, and their stability is examined. The problems of
non-integrability of the equations of motion because of a chaotic behavior of
the system are discussed.Comment: 25 pages, 4 figure
Paraneoplastic syndrome in urothelial carcinoma of the kidney: difficulty in diagnosis and deterioration in prognosis
Paraneoplastic syndrome is not a common concomitance of urothelial tumors. The literature describes a few tens of clinical cases in which urothelial cancer has become a cause of marked nonspecific tumor-associated reactions, associated with the presence of the tumor. Bladder tumors are at stake in all cases. The given clinical observation describes paraneoplastic manifestations in high-grade urothelial carcinoma of the kidney. It demonstrates difficulties in differential diagnosis and gives a retrospective estimate of diagnostic and therapeutic tactics
Watching dark solitons decay into vortex rings in a Bose-Einstein condensate
We have created spatial dark solitons in two-component Bose-Einstein
condensates in which the soliton exists in one of the condensate components and
the soliton nodal plane is filled with the second component. The filled
solitons are stable for hundreds of milliseconds. The filling can be
selectively removed, making the soliton more susceptible to dynamical
instabilities. For a condensate in a spherically symmetric potential, these
instabilities cause the dark soliton to decay into stable vortex rings. We have
imaged the resulting vortex rings.Comment: 4 pages, 4 figure
CFT driven cosmology and the DGP/CFT correspondence
We present a dual 5D braneworld picture of a recently suggested model for a
microcanonical description of a 4D cosmology driven by a conformal field theory
with a large number of quantum fields. The 5D side of the duality relation is
represented by a generalized brane induced gravity model in a Schwarzschild-de
Sitter bulk. The values of the bulk cosmological and the induced 4D
cosmological constants are determined by requiring the absence of conical
singularity at the de Sitter horizon of the Euclidean Schwarzschild-de Sitter
bulk. Those values belong to the vicinity of the upper bound of a range of
admissible values for the cosmological constant. This upper bound is enforced
by the 4D CFT and coincides with the natural gravitational cutoff in a theory
with many quantum species. The resulting DGP/CFT duality suggests the
possibility of a new type of {\em background independent} correspondence. A
mechanism for inverting the sign of the effective cosmological constant is
found, which might reconcile a negative value of the primordial cosmological
constant compatible with supersymmetry with the one required by inflationary
cosmology.Comment: LaTeX, 23 pages, 3 figure
Two dimensional modulational instability in photorefractive media
We study theoretically and experimentally the modulational instability of
broad optical beams in photorefractive nonlinear media. We demonstrate the
impact of the anisotropy of the nonlinearity on the growth rate of periodic
perturbations. Our findings are confirmed by experimental measurements in a
strontium barium niobate photorefractive crystal.Comment: 8 figure
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