Capacitive effects and memristive switching in three terminal multilayered MoS<inf>2</inf>devices

We report on the electrical properties of gated two-terminal multilayered molybdenum disulfide (MoS2) memristor devices having a planar architecture. The approach based on highly dispersed MoS2 flakes drop cast onto a bottom gated Si/SiO2 (100nm) wafer containing metal Pd contact electrodes yields devices that exhibit a number of complex properties including memristive and capacitive effects as well as multiple non-zero-crossing current-voltage hysteresis effects. The devices also show a reaction to a varying gate bias. An increasingly positive gate led to the devices displaying a linear ohmic I-V response while an increasingly negative gate bias drove the system to behave more memristive with a widening hysteresis loop

Psychological flourishing and Self-esteem as predictors of adjustment to university life among a sample of Qatar university students

يهدف البحث إلى الكشف عن العلاقة بين الازدهار النفسي وتقدير الذات والتوافق مع الحياة الجامعية لدى عينة من الطلاب في جامعة قطر، كما يهدف إلى تعرف الفروق بين عينة الدراسة في ضوء النوع والفرقة الدراسية والحالة الاجتماعية والتفاعل بينهم في تلك المتغيرات، وإمكانية التنبؤ بالتوافق مع الحياة الجامعية من خلال الازدهار النفسي وتقدير الذات. تكونت عينة الدراسة من 329 طالبًا وطالبة من طلاب جامعة قطر، طبق عليهم الباحثان مقياس الازدهار النفسي (Diener et al., 2009) ومقياس تقدير الذات (Rosenberg, 1965) ومقياس التوافق مع الحياة الجامعية (Baker &amp; Siryk, 1989). وتشير نتائج الدراسة إلى وجود علاقة ارتباطية دالة إحصائيا بين الازدهار النفسي وتقدير الذات والتوافق مع الحياة الجامعية لدى عينة الدراسة. كما أشارت النتائج إلى وجود فروق ذات دلالة إحصائية تعزى للنوع على بعد التوافق الشخصي الانفعالي والازدهار لصالح الذكور، كما ظهرت فروق تعزى للحالة الاجتماعية على التوافق الأكاديمي، والتعلق، والدرجة الكلية، وتقدير الذات والازدهار النفسي لصالح المتزوجين. وأخيرا، أظهرت النتائج أنه يمكن التنبؤ بالتوافق مع الحياة الجامعية وأبعاده الفرعية من خلال الازدهار النفسي وتقدير الذات

Relating Superembeddings and Non-linear Realisations

We discuss the relation between the superembedding method for deriving worldvolume actions for D-branes and the method of Partially Broken Global Supersymmetry based upon linear and non-linear realisations of SUSY. We give the explicit relation for the cases of space filling branes in 3 and 4 dimensions and show that the standard F-constraint of the superembedding method is the source of the required covariant non-linear constraints for the PBGS method.Comment: 19 pages. Improved spelling, references adde

The Self-Dual String and Anomalies in the M5-brane

We study the anomalies of a charge $Q_2$ self-dual string solution in the Coulomb branch of $Q_5$ M5-branes. Cancellation of these anomalies allows us to determine the anomaly of the zero-modes on the self-dual string and their scaling with $Q_2$ and $Q_5$. The dimensional reduction of the five-brane anomalous couplings then lead to certain anomalous couplings for D-branes.Comment: 13 pages, Harvmac, refs adde

U-duality covariant membranes

We outline a formulation of membrane dynamics in D=8 which is fully covariant under the U-duality group SL(2,Z) x SL(3,Z), and encodes all interactions to fields in the eight-dimensional supergravity, which is constructed through Kaluza-Klein reduction on T^3. Among the membrane degrees of freedom is an SL(2,R) doublet of world-volume 2-form potentials, whose quantised electric fluxes determine the membrane charges, and are conjectured to provide an interpretation of the variables occurring in the minimal representation of E_{6(6)} which appears in the context of automorphic membranes. We solve the relevant equations for the action for a restricted class of supergravity backgrounds. Some comments are made on supersymmetry and lower dimensions.Comment: LaTeX, 21 pages. v2: Minor changes in text, correction of a sign. v3: some changes in text, a sign convention changed; version to appear in JHE

Density functional theory for the crystallization of two-dimensional dipolar colloidal alloys

Two-dimensional mixtures of dipolar colloidal particles with different dipole moments exhibit extremely rich self-assembly behaviour and are relevant to a wide range of experimental systems, including charged and super-paramagnetic colloids at liquid interfaces. However, there is a gap in our understanding of the crystallization of these systems because existing theories such as integral equation theory and lattice sum methods can only be used to study the high temperature fluid phase and the zero-temperature crystal phase, respectively. In this paper we bridge this gap by developing a density functional theory (DFT), valid at intermediate temperatures, in order to study the crystallization of one and two-component dipolar colloidal monolayers. The theory employs a series expansion of the excess Helmholtz free energy functional, truncated at second order in the density, and taking as input highly accurate bulk fluid direct correlation functions from simulation. Although truncating the free energy at second order means that we cannot determine the freezing point accurately, our approach allows us to calculate \emph{ab initio} both the density profiles of the different species and the symmetry of the final crystal structures. Our DFT predicts hexagonal crystal structures for one-component systems, and a variety of superlattice structures for two-component systems, including those with hexagonal and square symmetry, in excellent agreement with known results for these systems. The theory also provides new insights into the structure of two-component systems in the intermediate temperature regime where the small particles remain molten but the large particles are frozen on a regular lattice

Methylphenidate improves executive functions in patients with traumatic brain injuries : a feasibility trial via the idiographic approach

Background: Road traffic accidents are known to be the main cause of traumatic brain injury (TBI). TBI is also a leading cause of death and disability. This study, by means of the idiographic approach (single-case experimental designs using multiple-baseline designs), has examined whether methylphenidate (MPH - trade name Ritalin) had a differential effect on cognitive measures among patients with TBI with the sequel of acute and chronic post-concussion syndromes. The effect on gender was also explored. Methods: In comparison with healthy controls, patients with TBI (acute and chronic) and accompanying mild cognitive impairment (MCI) were screened for their integrity of executive functioning. Twenty-four patients exhibiting executive dysfunction (ED) were then instituted with the pharmacological intervention methylphenidate (MPH). The methylphenidate was administered using an uncontrolled, open label design. Results: The administration of methylphenidate impacted ED in the TBI group but had no effect on mood. Attenuation of ED was more apparent in the chronic phases of TBI. The effect on gender was not statistically significant with regard to the observed changes. Conclusions: To our knowledge, this is the first feasibility trial from the Arabian Gulf to report the performance of a TBI population with mild cognitive impairment according to the IQCODE Arabic version. This investigation confirms anecdotal observations of methylphenidate having the potential to attenuate cognitive impairment; particularly those functions that are critically involved in the integrity of executive functioning. The present feasibility trial should be followed by nomothetic studies such as those that adhere to the protocol of the randomized controlled trial. This evidence-based research is the foundation for intervention and future resource allocation by policy- or public health decision-makers

On the equivalence of bound state solutions

In this paper we show the equivalence of various (non-threshold) bound state solutions of branes, or equivalently branes in background potentials, in ten- and eleven-dimensional supergravity. We compare solutions obtained in two very different ways. One method uses a zero mode analysis to make an Ansatz which makes it possible to solve the full non-linear supergravity equations. The other method utilises T-duality techniques to turn on the fields on the brane. To be specific, in eleven dimensions we show the equivalence for the (M2,M5) bound state, or equivalently an M5-brane in a C_3 field, where we also consider the (MW,M2,M2',M5) solution, which can be obtained from the (M2,M5) bound state by a boost. In ten dimensions we show the equivalence for the ((F,D1),D3) bound state as well as the bound states of (p,q) 5-branes with lower dimensional branes in type IIB, corresponding to D3-branes in B_2 and C_2 fields and (p,q) 5-branes in B_2, C_2 and C_4 fields. We also comment on the recently proposed V-duality related to infinitesimally boosted solutions.Comment: 19 pages, LaTe

Burnout Syndrome Among Primary Care Physicians in Oman

Objectives: Medical professionals are exposed to many job stressors everyday, which can lead to psychological disturbances as well as burnout syndrome. We sought to assess the level of burnout among primary care physicians (PCPs) in Oman and explore risk factors for its development. Methods: We conducted a cross-sectional, analytical study among a random cluster sample of 190 PCP working in Muscat, Oman. Indices of burnout (emotional exhaustion (EE), depersonalization (DP) and personal accomplishment (PA)) were noted using the Maslach Burnout Inventory-Human Services Survey (MBIHSS). We also used a questionnaire to obtain sociodemographic and job characteristics data. We used a binary logistic regression model and both unadjusted and adjusted odds ratios for statistical analysis. Results: The prevalence of burnout in all three dimensions was 6.3%. High levels of MBI-HSS subscales were reported on EE, DP and PA with 17.8%, 38.2%, and 21.5%, respectively. Logistic regression analysis revealed that working over 40 hours per week was the most important risk factor for burnout among PCPs. Conclusions: A total of 6.3% of PCPs working in urban areas in Oman suffered burnout. Long working hours was strongly associated with high occupational burnout. Solutions to eliminate or decrease the rate of burnout involve institutional changes, primarily respecting weekly working hours, and in more severe cases psychotherapy help is very important