Pseudomorphic SiGe/Si(001) layers synthesized by gas immersion laser doping

We report on the synthesis of SiGe layers on silicon by gas immersion laser doping. GeCl(4) molecules are adsorbed on the surface and further incorporated into the Si top layer by a pulsed laser induced melt/regrowth process. Structural and chemical characterizations of the SiGe layers have been performed by using complementarily Rutherford backscattering spectrometry and x-ray Diffraction which indicate that Ge incorporation in the Si matrix results in a fully strained SiGe layer with gradual Ge concentrations reaching up to 18.5% near the surface. (C) 2008 American Institute of Physics

Optical spectroscopy in (Zn,Cd)Se-ZnSe graded-index separate-confinement heterostructures

International audienceWe report a detailed examination of the electronic structure and of the thermal transport in a graded-index separate-confinement heterostructure based on (Zn,Cd)Se wide-band-gap II-VI semiconductors, and designed in the view of a blue-green light emission device. The band offsets and strain state of the heterostructure are obtained from 2-K photoreflectance measurements. The temperature dependence of the photoluminescence spectra taken both in a resonant in-well excitation condition and in an above-barrier excitation condition has enabled us to quantify the mechanisms responsible for the photoluminescence thermal quenching. This has been done in the context of a sophisticated model that includes several nonradiative processes. In the 10-70 K temperature range, the photoluminescence intensity is found to be ruled by a nonradiative detrapping towards interfacial defects, whilst the thermal escape effect is responsible for the photoluminescence quenching at higher temperatures. In the case of an above barrier excitation condition, the contribution of the carriers diffusion from the barriers to the well leads to an increase of the quantum-well photoluminescence, the intensity of which exhibits a maximum around 50 K

Genomic and Phylogenetic Analysis of Hepatitis C Virus Isolates from Argentine Patients: a Six-Year Retrospective Study

Typing of hepatitis C virus (HCV) isolates from Argentine patients was performed by using different methodologies in a population of 243 patients. HCV subtype was assigned based upon restriction fragment length polymorphism (RFLP). HCV RNA genomes obtained from serum samples were classified as belonging to clade 1 (53.5%), 2 (23.0%), or 3 (8.6%); 14.8% of samples showed HCV mixed infections, more frequently implying different subtypes within the same clade. In addition to RFLP typing, phylogenetic relatedness among sequences from both 5′ untranslated region (n = 50) and nonstructural 5B coding region (n = 15) was established

GB Virus C/Hepatitis G Virus Groups and Subgroups: Classification by a Restriction Fragment Length Polymorphism Method Based on Phylogenetic Analysis of the 5′ Untranslated Region

A phylogenetic tree based on 150 5′ untranslated region sequences deposited in GenBank database allowed segregation of the sequences into three major groups, including two subgroups, i.e., 1, 2a, 2b, and 3, supported by bootstrap analysis. Restriction site analysis of these sequences predicted that HinfI and either AatII or AciI could be used for genomic typing with 99.4% accuracy. cDNA sequencing and subsequent alignment of 21 Argentine GB virus C/hepatitis G virus strains confirmed restriction fragment length polymorphism patterns theoretically predicted. This method may be useful for a rapid screening of samples when either epidemiological or transmission studies of this agent are carried out

In Vitro Detection of Dissimilar Amounts of Hepatitis C Virus (HCV) Subtype-Specific RNA Genomes in Mixes Prepared from Sera of Persons Infected with a Single HCV Genotype

The level of in vitro detection of viral genomes in mixes with two different hepatitis C virus (HCV) subtypes was investigated by artificially mixing previously measured subtype-specific HCV RNA genomes. The RNAs in these mixtures were reverse transcribed and then PCR amplified by using two sets of primers corresponding to the 5′ untranslated region and digested with endonucleases to analyze the restriction fragment length polymorphism patterns. This approach facilitated detection of a wider range of type-specific HCV genomes than originally described, beyond equimolar concentrations of contributing HCV subtypes. Moreover, by using computerized image analysis, this study also demonstrated that the true contribution of each virus type—and consequently of mixed infections—may be underestimated when only visual observation is carried out. These results may be useful for comparing data obtained from this and other currently used methodologies