354 research outputs found
An integrable discretization of KdV at large times
An "exact discretization" of the Schroedinger operator is considered and its
direct and inverse scattering problems are solved. It is shown that a
differential-difference nonlinear evolution equation depending on two arbitrary
constants can be solved by using this spectral transform and that for a special
choice of the constants it can be considered an integrable discretization of
the KdV equation at large times. An integrable difference-difference equation
is also obtained.Comment: 12 page
A discrete Schrodinger spectral problem and associated evolution equations
A recently proposed discrete version of the Schrodinger spectral problem is
considered. The whole hierarchy of differential-difference nonlinear evolution
equations associated to this spectral problem is derived. It is shown that a
discrete version of the KdV, sine-Gordon and Liouville equations are included
and that the so called `inverse' class in the hierarchy is local. The whole
class of related Darboux and Backlund transformations is also exhibited.Comment: 14 pages, LaTeX2
Surgical Treatment of Giant Cavernous Hemangioma Liver
In the past five years, 16 adults (10 females, age 25–61 years, mean 48) with giant cavernous
hemangioma of the liver measuring 15–31 cm (mean-19) underwent surgery in a single Institution.
Diagnosis was made with the help of multimodal investigations– ultrasound (US), computed tomography
(CT), hepatic angiography, hepatic scintigraphy and fine needle biopsy. Ultrasound and CT had
sensitivities of 69% and 82% respectively. Fourteen had preoperative selective hepatic artery embolization
to study its effect on operative blood loss. Indication for surgery in all cases was a large abdominal
mass with varying severity of pain. In addition, 5 had hemetological and/or coagulation abnormalities,
hemobilia in and pyrexia in 1. Seven left lobectomies, 3 left lateral segmentectomies, 2 right
lobectomies, 2 right trisegmentectomies and 4 non-anatomical resections of to 3 segments were
performed. Postoperative complications developed in 25% with no operative mortality. Preoperative
selective hepatic artery embolization helped to decrease the operative hemorrhage in 13 (mean blood
loss– 1146 ml). In two cases severe bleeding required use of Cell-saver and massive donor blood
transfusion. Our results suggest use of preoperative selective hepatic artery embolization and Cell-saver
as an adjunct to the liver resection for these vascular tumors
Scattering Theory for Jacobi Operators with Steplike Quasi-Periodic Background
We develop direct and inverse scattering theory for Jacobi operators with
steplike quasi-periodic finite-gap background in the same isospectral class. We
derive the corresponding Gel'fand-Levitan-Marchenko equation and find minimal
scattering data which determine the perturbed operator uniquely. In addition,
we show how the transmission coefficients can be reconstructed from the
eigenvalues and one of the reflection coefficients.Comment: 14 page
Mimicking diffuse supernova antineutrinos with the Sun as a source
Measuring the electron antineutrino component of the cosmic diffuse supernova
neutrino background (DSNB) is the next ambitious goal for low-energy neutrino
astronomy. The largest flux is expected in the lowest accessible energy bin.
However, for E < 15 MeV a possible signal can be mimicked by a solar electron
antineutrino flux that originates from the usual 8B neutrinos by spin-flavor
oscillations. We show that such an interpretation is possible within the
allowed range of neutrino electromagnetic transition moments and solar
turbulent field strengths and distributions. Therefore, an unambiguous
detection of the DSNB requires a significant number of events at E > 15 MeV.Comment: 4 pages, 1 figur
Models of coherent exciton condensation
That excitons in solids might condense into a phase-coherent ground state was
proposed about 40 years ago, and has been attracting experimental and
theoretical attention ever since. Although experimental confirmation has been
hard to come by, the concepts released by this phenomenon have been widely
influential. This tutorial review discusses general aspects of the theory of
exciton and polariton condensates, focussing on the reasons for coherence in
the ground state wavefunction, the BCS to Bose crossover(s) for excitons and
for polaritons, and the relationship of the coherent condensates to standard
lasers.Comment: 27 pages, 6 figures. Submitted for a special issue of J. Phys. Cond.
Matt. associated with the EU network "Photon-mediated phenomena in
semiconductor nanostructures
К решению экологических вопросов энергетических систем
The paper analyses a possibility to minimize damage due to operation of power systems using fossil fuels. Technological schemes of purification processes ensuring efficient solution of the ecological problem, particularly, in the case of power station operating on natural gas and fuel oil are proposed in the paper. The paper contains an analysis of the mechanism in respect of processes occurring in the proposed methods for gas and liquid purification against detrimental impurities. Проанализированы возможности сведения к минимуму ущерба, возникающего в результате работающих на ископаемом топливе энергетических систем. Предложены технологические схемы очистительных процессов, обеспечивающих эффективное решение экологической проблемы, в частности в случае электрической станции, работающей на природном газе и мазуте. Проанализирован механизм процессов, происходящих в предложенных методах очистки газов и жидкостей от вредных примесей
The Relation Between the Surface Brightness and the Diameter for Galactic Supernova Remnants
In this work, we have constructed a relation between the surface brightness
() and diameter (D) of Galactic C- and S-type supernova remnants
(SNRs). In order to calibrate the -D dependence, we have carefully
examined some intrinsic (e.g. explosion energy) and extrinsic (e.g. density of
the ambient medium) properties of the remnants and, taking into account also
the distance values given in the literature, we have adopted distances for some
of the SNRs which have relatively more reliable distance values. These
calibrator SNRs are all C- and S-type SNRs, i.e. F-type SNRs (and S-type SNR
Cas A which has an exceptionally high surface brightness) are excluded. The
Sigma-D relation has 2 slopes with a turning point at D=36.5 pc: (at 1
GHz)=8.4 D
WmHzster (for
WmHzster and D36.5 pc) and (at 1
GHz)=2.7 10 D
WmHzster (for
WmHzster and D36.5 pc). We discussed the theoretical
basis for the -D dependence and particularly the reasons for the change
in slope of the relation were stated. Added to this, we have shown the
dependence between the radio luminosity and the diameter which seems to have a
slope close to zero up to about D=36.5 pc. We have also adopted distance and
diameter values for all of the observed Galactic SNRs by examining all the
available distance values presented in the literature together with the
distances found from our -D relation.Comment: 45 pages, 2 figures, accepted for publication in Astronomical and
Astrophysical Transaction
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