Single valley Dirac fermions in zero-gap HgTe quantum wells

Dirac fermions have been studied intensively in condensed matter physics in recent years. Many theoretical predictions critically depend on the number of valleys where the Dirac fermions are realized. In this work, we report the discovery of a two dimensional system with a single valley Dirac cone. We study the transport properties of HgTe quantum wells grown at the critical thickness separating between the topologically trivial and the quantum spin Hall phases. At high magnetic fields, the quantized Hall plateaus demonstrate the presence of a single valley Dirac point in this system. In addition, we clearly observe the linear dispersion of the zero mode spin levels. Also the conductivity at the Dirac point and its temperature dependence can be understood from single valley Dirac fermion physics.Comment: version 2: supplementary material adde

Gate-tuned normal and superconducting transport at the surface of a topological insulator

Three-dimensional topological insulators are characterized by the presence of a bandgap in their bulk and gapless Dirac fermions at their surfaces. New physical phenomena originating from the presence of the Dirac fermions are predicted to occur, and to be experimentally accessible via transport measurements in suitably designed electronic devices. Here we study transport through superconducting junctions fabricated on thin Bi2Se3 single crystals, equipped with a gate electrode. In the presence of perpendicular magnetic field B, sweeping the gate voltage enables us to observe the filling of the Dirac fermion Landau levels, whose character evolves continuously from electron- to hole-like. When B=0, a supercurrent appears, whose magnitude can be gate tuned, and is minimum at the charge neutrality point determined from the Landau level filling. Our results demonstrate how gated nano-electronic devices give control over normal and superconducting transport of Dirac fermions at an individual surface of a three-dimensional topological insulator.Comment: 28 pages, 5 figure

Brucellosis remains a neglected disease inthe developing world: a call forinterdisciplinary action

Brucellosis places significant burdens on the human healthcare system and limits the economic growth of individuals, communities, and nations where such development is especially important to diminish the prevalence of poverty. The implementation of public policy focused on mitigating the socioeconomic effects of brucellosis in human and animal populations is desperately needed. When developing a plan to mitigate the associated consequences, it is vital to consider both the abstract and quantifiable effects. This requires an interdisciplinary and collaborative, or One Health, approach that consists of public education, the development of an infrastructure for disease surveillance and reporting in both veterinary and medical fields, and campaigns for control in livestock and wildlife species

Primary Retroperitoneal Mucinous Cystadenocarcinoma: A Case Report and Review of the Literature

Primary retroperitoneal mucinous cystadenocarcinoma is a rare tumor. Only about 30 such cases have been reported in the worldwide literature, and a few Korean cases have been reported. The pathogenesis is not clear, and coelomic metaplasia of the retroperitoneal mesothelium has gained wide support. There is no consensus on the appropriate treatment, but surgical exploration is needed for the diagnosis and treatment, and adjuvant chemotherapy may be recommended following complete surgical excision. The long-term prognosis has not been established

Prevalence of childhood and early adolescence mental disorders among children attending primary health care centers in Mosul, Iraq: a cross-sectional study

<p>Abstract</p> <p>Background</p> <p>Children and adolescents are more vulnerable to the affects of war and violence than adults. At the time of initiation of this study, nothing was known about the prevalence of childhood and early adolescence mental disorders. The aim of the present study is to measure the point prevalence of mental disorders among children of 1–15 years age in the city of Mosul, Iraq.</p> <p>Methods</p> <p>A cross-sectional study design was adopted. Four primary health care centers were chosen consecutively as a study setting. The subjects of the present study were mothers who came to the primary health care center for vaccination of their children. The chosen mothers were included by systematic sampling randomization. All children (aged 1–15) that each mother had were considered in the interview and examination.</p> <p>Results</p> <p>Out of 3079 children assessed, 1152 have childhood mental disorders, giving a point prevalence of 37.4%, with a male to female ratio of to 1.22:1. The top 10 disorders among the examined children are post-traumatic stress disorder (10.5%), enuresis (6%), separation anxiety disorder (4.3%), specific phobia (3.3%) stuttering and refusal to attend school (3.2% each), learning and conduct disorders (2.5% each), stereotypic movement (2.3%) and feeding disorder in infancy or early childhood (2.0%). Overall, the highest prevalence of mental disorders was among children 10–15 years old (49.2%) while the lowest was among 1–5 year olds (29.1%). Boys are more affected than girls (40.2% and 33.2%, respectively).</p> <p>Conclusion</p> <p>Childhood mental disorders are a common condition highly prevalent amongst the children and early adolescents in Mosul. Data from the present study mirrors the size of the problem in local community. Several points deserve attention, the most important of which include giving care at the community level, educating the public on mental health, involving communities and families, monitoring community mental health indicators, and providing treatment at primary health care level.</p

Water Contamination Reduces the Tolerance of Coral Larvae to Thermal Stress

Coral reefs are highly susceptible to climate change, with elevated sea surface temperatures (SST) posing one of the main threats to coral survival. Successful recruitment of new colonies is important for the recovery of degraded reefs following mortality events. Coral larvae require relatively uncontaminated substratum on which to metamorphose into sessile polyps, and the increasing pollution of coastal waters therefore constitutes an additional threat to reef resilience. Here we develop and analyse a model of larval metamorphosis success for two common coral species to quantify the interactive effects of water pollution (copper contamination) and SST. We identify thresholds of temperature and pollution that prevent larval metamorphosis, and evaluate synergistic interactions between these stressors. Our analyses show that halving the concentration of Cu can protect corals from the negative effects of a 2–3°C increase in SST. These results demonstrate that effective mitigation of local impacts can reduce negative effects of global stressors

Quantitative Epistasis Analysis and Pathway Inference from Genetic Interaction Data

Inferring regulatory and metabolic network models from quantitative genetic interaction data remains a major challenge in systems biology. Here, we present a novel quantitative model for interpreting epistasis within pathways responding to an external signal. The model provides the basis of an experimental method to determine the architecture of such pathways, and establishes a new set of rules to infer the order of genes within them. The method also allows the extraction of quantitative parameters enabling a new level of information to be added to genetic network models. It is applicable to any system where the impact of combinatorial loss-of-function mutations can be quantified with sufficient accuracy. We test the method by conducting a systematic analysis of a thoroughly characterized eukaryotic gene network, the galactose utilization pathway in Saccharomyces cerevisiae. For this purpose, we quantify the effects of single and double gene deletions on two phenotypic traits, fitness and reporter gene expression. We show that applying our method to fitness traits reveals the order of metabolic enzymes and the effects of accumulating metabolic intermediates. Conversely, the analysis of expression traits reveals the order of transcriptional regulatory genes, secondary regulatory signals and their relative strength. Strikingly, when the analyses of the two traits are combined, the method correctly infers ∼80% of the known relationships without any false positives