Effective mass and band nonparabolicity in remote doped Si/Si0.8Ge0.2 quantum wells

The effective masses in remote doped Si/Si0.8Ge0.2/Si quantum wells having sheet densities, Ns in the range 2 × 1011–1.1 × 1012 cm – 2 have been determined from the temperature dependencies of the Shubnikov–de Haas oscillations. The values obtained increase with magnetic field and Ns. This behavior is taken as evidence for the nonparabolicity of the valence band and accounts for the discrepancies in previously reported masses. Self-consistent band structure calculations for a triangular confinement of the carriers have also been carried out and provide confirmation of the increase in mass with Ns. Theory and experiment give extrapolated Gamma point effective masses of 0.21 and 0.20 of the free-electron mass, respectively

Effects of Epigeic Earthworms, Eisenia fetida on Carbon and Nitrogen during Vermicomposting of Fresh Bio-waste

This study was carried out as an experiment using the following procedure: A plastic containers were prepared for vermicomposting, with the control without earthworms and the trials with earthworms (Eisenia fetida), within we used four types of beds (leaves, soil, vermiculite, and vermicompost), samples were taken for chemical analysis of total carbon, total nitrogen, ammonium, nitrate, and dissolved organic carbon contents. The results during 100 days of vermicomposting showed an increase of, ammonium, nitrate, and dissolved organic carbon contents, a depletion of total carbon and an increase of total nitrogen. The effect of earthworms on nutrients was significant in some reactors and not significant in others, which implies the effect of vermibed used on the process of decomposition by earthworms

Electrocardiographic left ventricular hypertrophy is not associated with increased in-hospital adverse events in patients experiencing first non-ST segment elevation myocardial infarction: A single center study

Background: There is conflicting data about prognostic implication of electrocardiographic (ECG) left ventricular hypertrophy (LVH) in patients with first non- ST-segment elevation myocardial infarction (NSTEMI). We aimed to examine the association of left ventricular hypertrophy (LVH) on admission electrocardiogram with adverse outcomes in patients with NSTEMI. Methods: In the present study, 460 patients (77.5 males with mean age of 65.44±13.15 years) with first NSTEMI were evaluated. ECG left ventricular hypertrophy (LVH) was diagnosed based on Sokolow-Lyon voltage criteria. Baseline laboratory and clinical results, angiographic data, as well as in- hospital adverse events were compared between the patients with and without LVH. Results: Electrocardiographic LVH was observed in 74 (16.1) patients. Patients with LVH had higher admission systolic blood pressure (132.91±21.08 vs 125.80±21.78; P=0.01) and higher peak troponin (6.42±1.03 vs 4.41±0.28; P=0.004), but less likely to undergo coronary angiography (54.1 vs 66.8; P=0.03) .Patients with electrocardiographic LVH had similar in-hospital mortality (5.4 vs 3.6, P=0.5) and heart failure/ pulmonary edema (2.7 vs 2.07, P=0.6) compared to patients without LVH. Conclusion: The present study showed that among the patients with first NSTEMI, electrocardiographic LVH was not associated with increased in-hospital adverse events

CD28null CD4 T-cell expansions in autoimmune disease suggest a link with cytomegalovirus infection

Immunosenescence is thought to contribute to the increase of autoimmune diseases in older people. Immunosenescence is often associated with the presence of an expanded population of CD4 T cells lacking expression of CD28 (CD28null). These highly cytotoxic CD4 T cells were isolated from disease-affected tissues in patients with rheumatoid arthritis, systemic lupus erythematosus, multiple sclerosis, or other chronic inflammatory diseases and their numbers appeared to be linked to disease severity. However, we recently demonstrated that the common herpes virus, cytomegalovirus (CMV), not ageing, is the major driver of this subset of cytotoxic T cells. In this review, we discuss how CMV might potentiate and exacerbate autoimmune disease through the expansion of CD28null CD4 T cells

Valence band engineering in semiconductor lasers

SIGLEAvailable from British Library Document Supply Centre- DSC:DX92207 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Valence band engineering in semiconductor lasers.

This thesis is concerned with the improvement of semiconductor laser characteristics using valence band engineering. We first show that the combination of strain and quantum confinement can confer considerable advantages to long wavelength lasers. With sufficient built-in strain, the highest hole subband has a low effective mass and is well separated from the lower bands. The low effective mass reduces the carrier density needed for population inversion and leads to the virtual elimination of two important loss mechanisms: Auger recombination and intervalence band absorption. We propose a specific strained-layer 1.55mum structure that can reduce the threshold current density and its temperature dependence and increase the luminescent efficiency. The presence of strain can also lead to an enhancement of the relaxation oscillation frequency due to the higher differential gain when compared to lattice-matched structures. The linewidth enhancement factor is also predicted to be reduced. Such strained-layer lasers could be of major significance for long distance optical communication. However, the long term stability of these structures, although promising, has still to be fully assessed. In view of this, we suggest that (111) growth of unstrained structures could provide the light-hole cap to the valence band needed for laser operation. We find that the threshold current density in thin (111) lasers could be reduced while the polarisation selection of TE modes could be improved compared to equivalent (001) lasers. Finally, we consider the effects of crystal orientation and of strain on the exciton binding energy