1,690 research outputs found
Topological Crystalline Insulators in the SnTe Material Class
Topological crystalline insulators are new states of matter in which the
topological nature of electronic structures arises from crystal symmetries.
Here we predict the first material realization of topological crystalline
insulator in the semiconductor SnTe, by identifying its nonzero topological
index. We predict that as a manifestation of this nontrivial topology, SnTe has
metallic surface states with an even number of Dirac cones on high-symmetry
crystal surfaces such as {001}, {110} and {111}. These surface states form a
new type of high-mobility chiral electron gas, which is robust against disorder
and topologically protected by reflection symmetry of the crystal with respect
to {110} mirror plane. Breaking this mirror symmetry via elastic strain
engineering or applying an in-plane magnetic field can open up a continuously
tunable band gap on the surface, which may lead to wide-ranging applications in
thermoelectrics, infrared detection, and tunable electronics. Closely related
semiconductors PbTe and PbSe also become topological crystalline insulators
after band inversion by pressure, strain and alloying.Comment: submitted on Feb. 10, 2012; to appear in Nature Communications; 5
pages, 4 figure
Application of the ANP to the prioritization of project stakeholders in the context of responsible research and innovation
[EN] This paper presents a methodology to assess the stakeholders¿ influence in a research project within the context of responsible research and innovation. The methodology is based on a combination of the multicriteria decision making technique analytic network process and the key areas of responsible research. The method allows ranking and ordering the project¿s stakeholders based on their influence upon its responsibility. The purpose of such an assessment is to help research teams to more efficiently devote their limited resources to stakeholder management. The procedure is applied to a case study of the Information and Communication Technology business sector. It is an ongoing project at an early phase of development. Influential stakeholders have been identified first, and have been further classified into groups based on their relative importance. The assessment of their influence has been based on up to 16 different criteria, mainly belonging to the framework of responsible research and innovation. In the case study, the most influential criterion was the Capability to promote public engagement, while Developers were found to be the stakeholders most contributing to the research project responsibility. However, as explained, this is a temporary situation, valid for the current project development situation. It may vary over time as criteria vary in weight and stakeholders vary in influence.The authors would like to thank to our anonymous referees for their constructive comments and suggestions that helped us to improve the quality of the paper. Also, to the “Bolívar Gana con Ciencia” program from the Gobernación de Bolívar (Colombia) for the financial support. For the same reason, the authors are grateful to the Spanish Agencia Estatal de Investigación for its support of the project Propuesta de Indicadores para Impulsar el Diseño de Una Política Orientada al Desarrollo de Investigación e Innovación Responsable en España (CSO2016-76828-R)Ligardo-Herrera, I.; Gómez-Navarro, T.; Gonzalez-Urango, H. (2018). Application of the ANP to the prioritization of project stakeholders in the context of responsible research and innovation. Central European Journal of Operations Research. 1-23. https://doi.org/10.1007/s10100-018-0573-4S123Akbari N, Irawan CA, Jones DF, Menachof D (2017) A multi-criteria port suitability assessment for developments in the offshore wind industry. Renew Energy 102:118–133. https://doi.org/10.1016/j.renene.2016.10.035Aragonés-Beltrán P, García-Melón M, Montesinos-Valera J (2017) How to assess stakeholders’ influence in project management? A proposal based on the analytic network process. 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The electric wind of Venus: A global and persistent "polar wind"-like ambipolar electric field sufficient for the direct escape of heavy ionospheric ions
Understanding what processes govern atmospheric escape and the loss of planetary water is of paramount importance for understanding how life in the universe can exist. One mechanism thought to be important at all planets is an “ambipolar” electric field that helps ions overcome gravity. We report the discovery and first quantitative extraterrestrial measurements of such a field at the planet Venus. Unexpectedly, despite comparable gravity, we show the field to be five times stronger than in Earth's similar ionosphere. Contrary to our understanding, Venus would still lose heavy ions (including oxygen and all water-group species) to space, even if there were no stripping by the solar wind. We therefore find that it is possible for planets to lose heavy ions to space entirely through electric forces in their ionospheres and such an “electric wind” must be considered when studying the evolution and potential habitability of any planet in any star system
Midwifery tutors' capacity and willingness to teach contraception, post-abortion care, and legal pregnancy termination in Ghana
<p>Abstract</p> <p>Background</p> <p>Ghana has a high maternal mortality rate of 540 per 100 000. Although abortion complications usually are treatable, the risks of morbidity and death increase when treatment is delayed. Delay in care may occur when women have difficulty accessing treatment because health care providers are not trained, equipped, or willing to treat the complications of abortion. Gaps in the midwifery tutors' knowledge on comprehensive abortion care (CAC) have resulted in most midwives in Ghana not knowing the legal indications under which safe abortion care can be provided, and lacking the skills and competencies for CAC services. The aim of this study is to assess the capacity and willingness of midwifery tutors to teach contraception, post abortion care and legal termination in Ghana.</p> <p>Methods</p> <p>This study focused on all 14 midwifery schools in the country. A total of 74 midwifery tutors were interviewed for this study. Structured self-administered questionnaires were used for data collection. The data were entered and checked for consistencies using Epiinfo 6.04 and analyzed using Stata 8. Descriptive analysis was used and frequencies reported with percentages.</p> <p>Results</p> <p>In total, 74 midwifery tutors were interviewed. Of these, 66 (89.2%) were females. The tutors had mainly been trained as midwives (51.4%) and graduate nurses (33.8%). Respondents were predominantly Christians (97.3%).</p> <p>The study discovered that only 18.9% of the tutors knew all the legal indications under which safe abortion care could be provided. The content of pre-service training of tutors did not include uterine evacuation with manual vacuum aspirator (MVA).</p> <p>The study also highlighted some factors that influence midwifery tutors' willingness to teach comprehensive abortion care. It was also revealed that personal and religious beliefs greatly influence teaching of Comprehensive Abortion Care.</p> <p>Conclusion</p> <p>The findings of this survey suggest that the majority of tutors did not know the abortion law in Ghana as well as the Ghana Health Service Reproductive Health Standards and Protocol. Thus, there is a need to enhance their capacities to teach the present pre-service students the necessary skills to offer CAC after school and to understand related issues such as related legal matters.</p
Global analyses of TetR family transcriptional regulators in mycobacteria indicates conservation across species and diversity in regulated functions
BACKGROUND: Mycobacteria inhabit diverse niches and display high metabolic versatility. They can colonise both humans and animals and are also able to survive in the environment. In order to succeed, response to environmental cues via transcriptional regulation is required. In this study we focused on the TetR family of transcriptional regulators (TFTRs) in mycobacteria. RESULTS: We used InterPro to classify the entire complement of transcriptional regulators in 10 mycobacterial species and these analyses showed that TFTRs are the most abundant family of regulators in all species. We identified those TFTRs that are conserved across all species analysed and those that are unique to the pathogens included in the analysis. We examined genomic contexts of 663 of the conserved TFTRs and observed that the majority of TFTRs are separated by 200 bp or less from divergently oriented genes. Analyses of divergent genes indicated that the TFTRs control diverse biochemical functions not limited to efflux pumps. TFTRs typically bind to palindromic motifs and we identified 11 highly significant novel motifs in the upstream regions of divergently oriented TFTRs. The C-terminal ligand binding domain from the TFTR complement in M. tuberculosis showed great diversity in amino acid sequence but with an overall architecture common to other TFTRs. CONCLUSION: This study suggests that mycobacteria depend on TFTRs for the transcriptional control of a number of metabolic functions yet the physiological role of the majority of these regulators remain unknown. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s12864-015-1696-9) contains supplementary material, which is available to authorized users
A specialized learner for inferring structured cis-regulatory modules
BACKGROUND: The process of transcription is controlled by systems of transcription factors, which bind to specific patterns of binding sites in the transcriptional control regions of genes, called cis-regulatory modules (CRMs). We present an expressive and easily comprehensible CRM representation which is capable of capturing several aspects of a CRM's structure and distinguishing between DNA sequences which do or do not contain it. We also present a learning algorithm tailored for this domain, and a novel method to avoid overfitting by controlling the expressivity of the model. RESULTS: We are able to find statistically significant CRMs more often then a current state-of-the-art approach on the same data sets. We also show experimentally that each aspect of our expressive CRM model space makes a positive contribution to the learned models on yeast and fly data. CONCLUSION: Structural aspects are an important part of CRMs, both in terms of interpreting them biologically and learning them accurately. Source code for our algorithm is available at
Role of Polypyrimidine Tract Binding Protein in Mediating Internal Initiation of Translation of Interferon Regulatory Factor 2 RNA
BACKGROUND: Earlier we have reported translational control of interferon regulatory factor 2 (IRF2) by internal initiation (Dhar et al, Nucleic Acids Res, 2007). The results implied possible role of IRF2 in controlling the intricate balance of cellular gene expression under stress conditions in general. Here we have investigated the secondary structure of the Internal Ribosome Entry Site of IRF2 RNA and demonstrated the role of PTB protein in ribosome assembly to facilitate internal initiation. METHODOLOGY/PRINCIPAL FINDINGS: We have probed the putative secondary structure of the IRF2 5'UTR RNA using various enzymatic and chemical modification agents to constrain the secondary structure predicted from RNA folding algorithm Mfold. The IRES activity was found to be influenced by the interaction of trans-acting factor, polypyrimidine tract binding protein (PTB). Deletion of 25 nts from the 3'terminus of the 5'untranslated region resulted in reduced binding with PTB protein and also showed significant decrease in IRES activity compared to the wild type. We have also demonstrated putative contact points of PTB on the IRF2-5'UTR using primer extension inhibition assay. Majority of the PTB toe-prints were found to be restricted to the 3'end of the IRES. Additionally, Circular Dichroism (CD) spectra analysis suggested change in the conformation of the RNA upon PTB binding. Further, binding studies using S10 extract from HeLa cells, partially silenced for PTB gene expression, resulted in reduced binding by other trans-acting factors. Finally, we have demonstrated that addition of recombinant PTB enhances ribosome assembly on IRF2 IRES suggesting possible role of PTB in mediating internal initiation of translation of IRF2 RNA. CONCLUSION/SIGNIFICANCE: It appears that PTB binding to multiple sites within IRF2 5'UTR leads to a conformational change in the RNA that facilitate binding of other trans-acting factors to mediate internal initiation of translation
Building block libraries and structural considerations in the self-assembly of polyoxometalate and polyoxothiometalate systems
Inorganic metal-oxide clusters form a class of compounds that are unique in their topological and electronic versatility and are becoming increasingly more important in a variety of applications. Namely, Polyoxometalates (POMs) have shown an unmatched range of physical properties and the ability to form structures that can bridge several length scales. The formation of these molecular clusters is often ambiguous and is governed by self-assembly processes that limit our ability to rationally design such molecules. However, recent years have shown that by considering new building block principles the design and discovery of novel complex clusters is aiding our understanding of this process. Now with current progress in thiometalate chemistry, specifically polyoxothiometalates (POTM), the field of inorganic molecular clusters has further diversified allowing for the targeted development of molecules with specific functionality. This chapter discusses the main differences between POM and POTM systems and how this affects synthetic methodologies and reactivities. We will illustrate how careful structural considerations can lead to the generation of novel building blocks and further deepen our understanding of complex systems
Mycobacterium tuberculosis osteomyelitis in a patient with human immunodeficiency virus/acquired immunodeficiency syndrome (HIV/AIDS): a case report
The incidence of tuberculosis is increasing in the United States. Extra-pulmonary involvement is more common in patients with HIV/AIDS. The diagnosis of Tuberculosis osteomyelitis requires a high degree of suspicion for accurate and timely diagnosis
Increased ventral striatal volume in college-aged binge drinkers
BACKGROUND
Binge drinking is a serious public health issue associated with cognitive, physiological, and anatomical differences from healthy individuals. No studies, however, have reported subcortical grey matter differences in this population. To address this, we compared the grey matter volumes of college-age binge drinkers and healthy controls, focusing on the ventral striatum, hippocampus and amygdala.
METHOD
T1-weighted images of 19 binge drinkers and 19 healthy volunteers were analyzed using voxel-based morphometry. Structural data were also covaried with Alcohol Use Disorders Identification Test (AUDIT) scores. Cluster-extent threshold and small volume corrections were both used to analyze imaging data.
RESULTS
Binge drinkers had significantly larger ventral striatal grey matter volumes compared to controls. There were no between group differences in hippocampal or amygdalar volume. Ventral striatal, amygdalar, and hippocampal volumes were also negatively related to AUDIT scores across groups.
CONCLUSIONS
Our findings stand in contrast to the lower ventral striatal volume previously observed in more severe forms of alcohol use disorders, suggesting that college-age binge drinkers may represent a distinct population from those groups. These findings may instead represent early sequelae, compensatory effects of repeated binge and withdrawal, or an endophenotypic risk factor
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