A one-dimensional model for the growth of CdTe quantum dots on Si substrates

Recent experiments involving CdTe films grown on Si(111) substrates by hot wall epitaxy revealed features not previously observed [S. O. Ferreira \textit{et al.}, J. Appl. Phys. \textbf{93}, 1195 (2003)]. This system, which follows the Volmer-Weber growth mode with nucleation of isolated 3D islands for less than one monolayer of evaporated material, was described by a peculiar behavior of the quantum dot (QD) size distributions. In this work, we proposed a kinetic deposition model to reproduce these new features. The model, which includes thermally activated diffusion and evaporation of CdTe, qualitatively reproduced the experimental QD size distributions. Moreover, the model predicts a transition from Stranski-Krastanow growth mode at lower temperatures to Volmer-Weber growth mode at higher ones characterized through the QD width distributions.Comment: to appear in Physics Letters

Exact Analysis of Level-Crossing Statistics for (d+1)-Dimensional Fluctuating Surfaces

We carry out an exact analysis of the average frequency $\nu_{\alpha x_i}^+$ in the direction $x_i$ of positive-slope crossing of a given level $\alpha$ such that, $h({\bf x},t)-\bar{h}=\alpha$, of growing surfaces in spatial dimension $d$. Here, $h({\bf x},t)$ is the surface height at time $t$, and $\bar{h}$ is its mean value. We analyze the problem when the surface growth dynamics is governed by the Kardar-Parisi-Zhang (KPZ) equation without surface tension, in the time regime prior to appearance of cusp singularities (sharp valleys), as well as in the random deposition (RD) model. The total number $N^+$ of such level-crossings with positive slope in all the directions is then shown to scale with time as $t^{d/2}$ for both the KPZ equation and the RD model.Comment: 22 pages, 3 figure

Beliefs of Health Care Providers, Lay Health Care Providers and Lay Persons in Nigeria Regarding Hypertension. A Systematic Mixed Studies Review

<div><p>Background</p><p>Hypertension is a major health risk factor for mortality globally, resulting in about 13% of deaths worldwide. In Nigeria, the high burden of hypertension remains an issue for urgent attention. The control of hypertension, among other factors, is strongly determined by personal beliefs about the illness and recommended treatment.</p><p>Objective</p><p>The aim of this review is to systematically synthesize available data from all types of studies on beliefs of the Nigerian populace about hypertension</p><p>Methods</p><p>We searched the following electronic databases; Medline, EMBase, PsycInfo, AMED from their inception till date for all relevant articles. A modified Kleinman’s explanatory model for hypertension was used as a framework for extraction of data on beliefs about hypertension.</p><p>Results</p><p>The search yielded a total of 3,794 hits from which 16 relevant studies (2 qualitative, 11 quantitative and 3 mixed methods studies) met the inclusion criteria for the review. Overall, most health care providers (HCPs) believe that stress is a major cause of hypertension. Furthermore, reported cut-off point for uncomplicated hypertension differed widely among HCPs. Lay Health Care Providers such as Patent Medicine Vendors’ beliefs about hypertension seem to be relatively similar to health care professionals in areas of risk factors for hypertension, course of hypertension and methods of treatment. Among Lay persons, misconception about hypertension was quite high. Although some Nigerians believed that life style habits such as alcohol intake, exercise levels, cigarette smoking were risk factors for developing hypertension, there was discordance between belief and practice of control of risk factors. However, beliefs across numerous ethnic groups and settings (urban/rural) in Nigeria have not been explored.</p><p>Conclusion</p><p>In order to achieve control of hypertension in Nigeria, interventions should be informed, among other factors, by adequate knowledge of beliefs regarding hypertension across the numerous ethnic groups in Nigeria, settings (rural/urban), age and sex.</p></div

Is it possible to improve neurodevelopmental abnormalities in Down syndrome?

Down syndrome (DS) is a genetic pathology caused by the triplication of human chromosome 21. Although individuals with DS have various medical problems, intellectual disability is the most invalidating aspect of the pathology. Despite numerous efforts, the mechanisms whereby gene triplication leads to the DS phenotype have not been elucidated and there are, at present, no therapies to rescue brain developmental alterations and mental disability in individuals with DS. In this review, we focused on the major defects of the DS brain, comparing data regarding humans with DS and mouse models for DS, and therapeutic interventions attempted on animal DS models. Based on the promising results of pharmacotherapies in these models, we believe that it is possible to conclude that tools to improve brain development in DS are now almost at hand. We now know that it is possible to rescue and/or improve neurogenesis, neuron maturation, connectivity, neurodegeneration and behavior. We believe that the knowledge gained in DS mouse models provides a rational basis to start new clinical trials in infants, children and adults with DS, exploiting drugs that have proved able to rescue various facets of the DS neurologic phenotype. It is not unreasonable to consider that the results of these trials may provide a positive answer to the question: 'Is it possible to improve brain development in DS?'