101 research outputs found
Caractérisation de l'egalisabilité spatio-temporelle : cas d'un canal variant dans le temps
Nous étudions l'influence des variations temporelles d'un canal sur la difficulté à égaliser correctement dans le cadre de la diversité spatio-temporelle et indépendamment d'un algorithme en particulier. Pour cela, nous définissons un degré de non-égalisabilité (DNE) qui permet d'évaluer cette difficulté de manière quantitative et uniquement en fonction de la variation du canal. Cependant, le DNE ne suffit pas à expliquer le comportement d'un algorithme tel que le LMS. Nous montrons qu'il dépend essentiellement de la disparité du canal à chaque instant
Analytical solutions for semiconductor luminescence including Coulomb correlations with applications to dilute bismides
In this paper we introduce analytical solutions of interband polarization, which is the self-energy of the Dyson equation for the photon Green’s functions, and apply them to studying photoluminescence of Coulomb-correlated semiconductor materials. The accuracy of the easily programmable solutions is proven by consistently demonstrating the low-temperature s-shape of the luminescence peak of dilute bismide semiconductors. The different roles of homogeneous versus inhomogeneous broadening at low and high temperatures are described, as well as the importance of many body effects, which are in very good agreement with experiments
Elastic Nd scattering at intermediate energies as a tool for probing the short-range deuteron structure
A calculation of the deuteron polarization observables , ,
, and the differential cross-section for elastic
nucleon-deuteron scattering at incident deuteron energies 270 and 880 MeV in
lab is presented. A comparison of the calculations with two different deuteron
wave-functions derived from the Bonn-CD -potential model and the dressed
bag quark model is carried out. A model-independent approach, based on an
optical potential framework, is used in which a nucleon-nucleon -matrix is
assumed to be local and taken on the energy shell, but still depends on the
internal nucleon momentum in a deuteron.Comment: 15 pages, 4 figure
Thermal Properties of an Inflationary Universe
An energetic justification of a thermal component during inflation is given.
The thermal component can act as a heat reservoir which induces thermal
fluctuations on the inflaton field system. We showed previously that such
thermal fluctuations could dominate quantum fluctuations in producing the
initial seeds of density perturbations. A Langevin-like rate equation is
derived from quantum field theory which describes the production of
fluctuations in the inflaton field when acted upon by a simple modeled heat
reservoir. In a certain limit this equation is shown to reduce to the standard
Langevin equation, which we used to construct "Warm Inflation" scenarios in
previous work. A particle physics interpretation of our system-reservoir model
is offered.Comment: 28 pages, 0 figures, In Press Physical Review D 199
Deuteron-Proton Elastic Scattering at Intermediate Energies
The deuteron-proton elastic scattering has been studied in the multiple
scattering expansion formalism. The essential attention has been given to such
relativistic problem as a deuteron wave function in a moving frame and
transformation of spin states due to Wigner rotation. Parameterization of the
nucleon-nucleon -matrix has been used to take the off-energy shell effects
into account. The vector, and tensor, , analyzing powers of the
deuteron have been calculated at two deuteron kinetic energies: 395 MeV and
1200 MeV. The obtained results are compared with the experimental data
Parity nonconservation in deuteron photoreactions
We calculate the asymmetries in parity nonconserving deuteron
photodisintegration due to circularly polarized photons gamma+d to n+p with the
photon laboratory energy ranging from the threshold up to 10 MeV and the
radiative capture of thermal polarized neutrons by protons n+p to gamma+d. We
use the leading order electromagnetic Hamiltonian neglecting the smaller
nuclear exchange currents. Comparative calculations are done by using the
Reid93 and Argonne v18 potentials for the strong interaction and the DDH and
FCDH "best" values for the weak couplings in a weak one-meson exchange
potential. A weak NDelta transition potential is used to incorporate also the
Delta(1232)-isobar excitation in the coupled-channels formalism.Comment: 14 pages, 13 figures (18 eps files), LaTeX2
Fifty years of the Glauber diffraction theory
In this minireview a historical excursus in theoretical studies related to
the Glauber diffraction theory has been presented with an accent on the recent
developments in this subject.Comment: 22 pages, 4 figures, in russian;v2: an atempt to improve hyphenatio
Epitaxial growth of silicon and germanium on (100)-oriented crystalline substrates by RF PECVD at 175 °C
Raman scattering reveals strong LO-phonon-hole-plasmon coupling in nominally undoped GaAsBi: optical determination of carrier concentration
We report room-temperature Raman scattering studies of nominally undoped (100) GaAs1−xBix epitaxial layers exhibiting Biinduced (p-type) longitudinal-optical-plasmon coupled (LOPC) modes for 0.018≤x≤0.048. Redshifts in the GaAs-like optical modes due to alloying are evaluated and are paralleled by strong damping of the LOPC. The relative integrated Raman intensities of LO(Γ) and LOPC ALO/ALOPC are characteristic of heavily doped p-GaAs, with a remarkable near total screening of the LO(Γ) phonon (ALO/ALOPC →0) for larger Bi concentrations. A method of spectral analysis is set out which yields estimates of hole concentrations in excess of 5 × 1017 cm−3 and correlates with the Bi molar fraction. These findings are in general agreement with recent electrical transport measurements performed on the alloy, and while the absolute size of the hole concentrations differ, likely origins for the discrepancy are discussed. We conclude that the damped LO-phonon-hole-plasmon coupling phenomena plays a dominant role in Raman scattering from unpassivated nominally undoped GaAsBi
Vaccination against SARS-CoV-2 in pregnancy during the Omicron wave: the prospective cohort study of the Italian obstetric surveillance system
Objectives: Evidence on the effects of the SARS-CoV-2 Omicron variant on vaccinated and unvaccinated pregnant women is sparse. This study aimed to compare maternal and perinatal outcomes of women infected with SARS-CoV-2 during the Omicron wave in Italy, according to their vaccine protection.Methods: This national prospective cohort study enrolled pregnant women with a positive SARS-CoV-2 nasopharyngeal swab within 7 days of hospital admission between 1 January and 31 May, 2022. Women who received at least one dose of vaccine during pregnancy and those who completed the vaccine cycle with the first booster were considered protected against moderate or severe COVID-19 (MSCD). A multivariable logistic regression model evaluated the association between vaccine protection and disease severity. Maternal age, educational level, citizenship, area of birth, previous comorbidities, and obesity were analysed as potential risk factors. Results: MSCD was rare (41/2147, 1.9%; 95% CI, 1.4-2.6), and the odds of developing it were significantly higher among unprotected women (OR, 2.78; 95% CI, 1.39-5.57). Compared with protected women (n = 1069), the unprotected (n = 1078) were more often younger, with lower educational degrees, and foreigners. A higher probability of MSCD was found among women with previous comorbidities (OR, 2.86; 95% CI, 1.34-6.12) and those born in Asian countries (OR, 3.05; 95% CI, 1.23-7.56). The percentage of preterm birth was higher among women with MSCD compared with milder cases (32.0% [8/25] versus 8.4% [161/1917], p < 0.001) as well as the percentage of caesarean section (52.0% [13/25] versus 31.6% [606/1919], p 0.029). Discussion: Although severe maternal and perinatal outcomes were rare, their prevalence was significantly higher among women without vaccine protection. Vaccination during pregnancy has the potential to protect both the mother and the baby, and it is therefore strongly recommended. Edoardo Corsi Decenti, Clin Microbiol Infect 2023;29:772 (c) 2023 European Society of Clinical Microbiology and Infectious Diseases. Published by Elsevier Ltd. All rights reserved
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