Nonlinear stability of <i>E</i> centers in Si_1-<i>x</i>Ge_<i>x</i>: electronic structure calculations

Electronic structure calculations are used to investigate the binding energies of defect pairs composed of lattice vacancies and phosphorus or arsenic atoms (E centers) in silicon-germanium alloys. To describe the local environment surrounding the E center we have generated special quasirandom structures that represent random silicon-germanium alloys. It is predicted that the stability of E centers does not vary linearly with the composition of the silicon-germanium alloy. Interestingly, we predict that the nonlinear behavior does not depend on the donor atom of the E center but only on the host lattice. The impact on diffusion properties is discussed in view of recent experimental and theoretical results

Engineering the free vacancy and active donor concentrations in phosphorus and arsenic double donor-doped germanium

In germanium, donor atoms migrate or form larger immobile clusters via their interaction with lattice vacancies. By engineering the concentration of free vacancies, it is possible to control the diffusion of the donor atoms and the formation of those larger clusters that lead to the deactivation of a significant proportion of the donor atoms. Electronic structure calculations in conjunction with mass action analysis are used to predict the concentrations of free vacancies and deactivated donor atoms in germanium doped with different proportions of arsenic and phosphorous. We find, for example, that at low temperatures, the concentration of free vacancies is partially suppressed by increasing the proportion of arsenic doping, whereas at high temperatures (above 1000 K), the concentration of free vacancies is relatively constant irrespective of the donor species. It is predicted that the free vacancy and active donor concentrations vary linearly with the arsenic to phosphorous ratio across a wide range of temperatures

Diffusion and defect reactions between donors, C, and vacancies in Ge. II. Atomistic calculations of related complexes

Electronic structure calculations are used to study the stability, concentration, and migration of vacancy-donor (phosphorus, arsenic, and antimony) complexes in germanium, in the presence of carbon. The association of carbon with mobile vacancy-donor pairs can lead to energetically favorable and relatively immobile complexes. It is predicted that the complexes formed between lattice vacancies, carbon, and antimony substitutional atoms are more stable and less mobile compared to complexes composed of vacancies, carbon, and phosphorus or arsenic atoms. Then, with the use of mass action analysis, the relative concentrations of the most important complexes are calculated, which depend also on their relative stability not just their absolute stability. Overall, the theoretical predictions are consistent with experimental results, which determined that the diffusion of vacancy-donor defects is retarded in the presence of carbon, especially in samples with a high concentration of carbon. In addition, the calculations provide information on the structure and the equilibrium concentration of the most important complexes and details of their association energies

Clinical improvements following bilateral anterior capsulotomy in treatment-resistant depression

The purpose of this study was to evaluate a programme of lesion surgery carried out on patients with treatment-resistant depression (TRD). This was a retrospective study looking at clinical and psychometric data from 45 patients with TRD who had undergone bilateral stereotactic anterior capsulotomy surgery over a period of 15 years, with the approval of the Mental Health Act Commission (37 with unipolar depression and eight with bipolar disorder). The Beck Depression Inventory (BDI) before and after surgery was used as the primary outcome measure. The Montgomery–Asberg Depression Rating Scale was administered and cognitive aspects of executive and memory functions were also examined. We carried out a paired-samples t test on the outcome measures to determine any statistically significant change in the group as a consequence of surgery. Patients improved on the clinical measure of depression after surgery by −21.20 points on the BDI with a 52% change. There were no significant cognitive changes post-surgery. Six patients were followed up in 2013 by phone interview and reported a generally positive experience. No major surgical complications occurred. With the limitations of an uncontrolled, observational study, our data suggest that capsulotomy can be an effective treatment for otherwise TRD. Performance on neuropsychological tests did not deteriorate

Intrinsic and extrinsic diffusion of indium in germanium

Diffusion experiments with indium (In) in germanium (Ge) were performed in the temperature range between 550 and 900°C. Intrinsic and extrinsic doping levels were achieved by utilizing various implantation doses. Indium concentration profiles were recorded by means of secondary ion mass spectrometry and spreading resistance profiling. The observed concentration independent diffusion profiles are accurately described based on the vacancy mechanism with a singly negatively charged mobile In-vacancy complex. In accord with the experiment, the diffusion model predicts an effective In diffusion coefficient under extrinsic conditions that is a factor of 2 higher than under intrinsic conditions. The temperature dependence of intrinsic In diffusion yields an activation enthalpy of 3.51 eV and confirms earlier results of Dorner et al. [Z. Metallk. 73, 325 (1982)]. The value clearly exceeds the activation enthalpy of Ge self- diffusion and indicates that the attractive interaction between In and a vacancy does not extend to third nearest neighbor sites which confirms recent theoretical calculations. At low temperatures and high doping levels, the In profiles show an extended tail that could reflect an enhanced diffusion at the beginning of the annealing

Vacancy-mediated dopant diffusion activation enthalpies for germanium

Electronic structure calculations are used to predict the activation enthalpies of diffusion for a range of impurity atoms (aluminium, gallium, indium, silicon, tin, phosphorus, arsenic, and antimony) in germanium. Consistent with experimental studies, all the impurity atoms considered diffuse via their interaction with vacancies. Overall, the calculated diffusion activation enthalpies are in good agreement with the experimental results, with the exception of indium, where the most recent experimental study suggests a significantly higher activation enthalpy. Here, we predict that indium diffuses with an activation enthalpy of 2.79 eV, essentially the same as the value determined by early radiotracer studies

Yerba mate aqueous extract improves the oxidative and inflammatory states of rats with adjuvant-induced arthritis

Healthy and adjuvant-induced arthritic rats were treated for 23 days with daily doses of 400 and 800 mg kg−1 Ilex paraguariensis extract. This treatment (a) diminished the ROS levels in the liver and brain, (b) decreased oxidative protein and lipid damage in liver and brain, (c) increased the plasma antioxidant capacity, (d) increased the GSH levels and the GSH/GSSH ratio in both the liver and the brain, (e) almost restored the enzymatic activities linked to the metabolism of GSH–GSSG, and (f ) reversed the modified activities of xanthine oxidase, superoxide dismutase and catalase. The anti-inflammatory actions (firstly) and the antioxidant actions (in the second place) of the yerba mate constituents (e.g., chlorogenic acid derivatives) are the causes of these beneficial effects. Daily ingestion of traditional yerba mate beverages may be effective in attenuating the symptoms of inflammatory diseases, especially in older adults.This work was financially supported by grants from the Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq-307944/2015-8), Coordenação do Aperfeiçoamento de Pessoal do Ensino Superior (CAPES) and Fundação Araucária. The authors are also indebted to Jailson Araújo Dantas for his technical assistance and to Dr Ciomar A. B. Amado for facilitating access to equipment of the Pharmacology and Therapeutics Department of the State University of Maringá. The authors are also grateful to the Foundation for Science and Technology (FCT, Portugal) and FEDER under Programme PT2020 for financial support to CIMO (UID/AGR/00690/2013) and L. Barros contract.info:eu-repo/semantics/publishedVersio