Excitonic photoluminescence in symmetric coupled double quantum wells subject to an external electric field

The effect of an external electric field F on the excitonic photoluminescence (PL) spectra of a symmetric coupled double quantum well (DQW) is investigated both theoretically and experimentally. We show that the variational method in a two-particle electron-hole wave function approximation gives a good agreement with measurements of PL on a narrow DQW in a wide interval of F including flat-band regime. The experimental data are presented for an MBE-grown DQW consisting of two 5 nm wide GaAs wells, separated by a 4 monolayers (MLs) wide pure AlAs central barrier, and sandwiched between Ga_{0.7}Al_{0.3}As layers. The bias voltage is applied along the growth direction. Spatially direct and indirect excitonic transitions are identified, and the radius of the exciton and squeezing of the exciton in the growth direction are evaluated variationally. The excitonic binding energies, recombination energies, oscillator strengths, and relative intensities of the transitions as functions of the applied field are calculated. Our analysis demonstrates that this simple model is applicable in case of narrow DQWs not just for a qualitative description of the PL peak positions but also for the estimation of their individual shapes and intensities.Comment: 5 pages, 4 figures (accepted in Phys. Rev. B

MAGNETO - OPTICAL EFFECTS IN THE IMPURITY SPECTRAL REGION OF CdCr2Se4

Nous avons mesuré l'absorption optique et le dichroïsme circulaire magnétique sur les monocristaux de CdCr2Se4. On compare l'effet des traitements thermiques soit dans le vide soit dans la vapeur de sélénium avec celui qu'on observe dans les spectres des cristaux dopés à l'argent ou irradiés par les deuterons.Optical absorption and magnetic circular dichroïsm measurements in CdCr2Se4 single crystals are reported. We compare the samples annealed in vacuum or in selenium vapour with the silver doped ones and with the samples irradiated by deuterons

A Comparison of the Incidence of Early Postoperative Infections between Patients Using Synthetic Mesh and Those Undergoing Traditional Pelvic Reconstructive Surgical Procedures

New mesh-related complications such as erosion, etc., can result from abnormal postoperative healing due to surgical site infection. The aim of our study was to compare systemic inflammatory responses and the incidence of early infectious complications after reconstructive surgery using synthetic mesh and after traditional vaginal wall repair. In this prospective observational study 99 women with symptomatic pelvic organ prolapse were included; 55 women underwent traditional repair and 44 repair using mesh. After the procedure infectious complications were monitored. The patients who underwent reconstructive surgery using mesh material were more likely to have febrile morbidity in the postoperative period than the patients who had been treated with traditional repair (p=0.031); there was a higher incidence of combination febrile morbidity with elevated C-reactive protein (CRP) > 50 mg/l; p=0.046, and a higher incidence of CRP increase over 30 mg/l; p=0.005. Reconstructive procedures using synthetic mesh are accompanied by a higher incidence of early post-operative infectious complications