Theory of correlations in strongly interacting fluids of two-dimensional dipolar bosons

Ground-state properties of a two-dimensional fluid of bosons with repulsive dipole-dipole interactions are studied by means of the Euler-Lagrange hypernetted-chain approximation. We present a self-consistent semi-analytical theory of the pair distribution function $g(r)$ and ground-state energy of this system. Our approach is based on the solution of a zero-energy scattering Schr\"{o}dinger equation for the "pair amplitude" $\sqrt{g(r)}$ with an effective potential from Jastrow-Feenberg correlations. We find excellent agreement with quantum Monte Carlo results over a wide range of coupling strength, nearly up to the critical coupling for the liquid-to-crystal quantum phase transition. We also calculate the one-body density matrix and related quantities, such as the momentum distribution function and the condensate fraction.Comment: 8 pages, 8 figures, submitte

The investigation of limiting factors of earnings management for companies’ listed Tehran stock exchange

The current study was to examine the limiting factors of earnings management for companies’ listed Tehran stock exchange. The study was a kind of applied, descriptive- correlative research. All listed companies in Tehran stock exchange were selected as  statistical population during 2009 to 2013. So, data was gathered by library method  and collected by systematic eliminated sampling method. The results show that there is  a significant inverse relationship between board size and earnings management in companies’ listed Tehran stock exchange. The result doesn’t show any significant relationship between dividend and earnings management in companies’ listed Tehran stock exchange.Keywords: real earnings management; accrual earnings management; discretionary accruals; non-discretionary accruals; intensive factor

Topological electric current from time-dependent elastic deformations in graphene

We show the possibility of inducing an edge charge current by applying time-dependent strain in gapped graphene samples preserving time reversal symmetry. We demonstrate that this edge current has the same origin as the valley Hall response known to exist in the system.Comment: 5 pages, 3 figures, Accepted for publication in Phys. Rev.

Electron-electron interactions in decoupled graphene layers

Multi-layer graphene on the carbon face of silicon carbide is an intriguing electronic system which typically consists of a stack of ten or more layers. Rotational stacking faults in this system dramatically reduce inter-layer coherence. In this article we report on the influence of inter-layer interactions, which remain strong even when coherence is negligible, on the Fermi liquid properties of charged graphene layers. We find that inter-layer interactions increase the magnitudes of correlation energies and decrease quasiparticle velocities, even when remote-layer carrier densities are small, and that they lessen the influence of exchange and correlation on the distribution of carriers across layers.Comment: 8 pages, 4 figures, submitte

Irreversibility in response to forces acting on graphene sheets

The amount of rippling in graphene sheets is related to the interactions with the substrate or with the suspending structure. Here, we report on an irreversibility in the response to forces that act on suspended graphene sheets. This may explain why one always observes a ripple structure on suspended graphene. We show that a compression-relaxation mechanism produces static ripples on graphene sheets and determine a peculiar temperature $T_c$, such that for $T<T_c$ the free-energy of the rippled graphene is smaller than that of roughened graphene. We also show that $T_c$ depends on the structural parameters and increases with increasing sample size.Comment: 4 pages, 4 Figure

Effects of Neurosurgical Treatment and Severity of Head Injury on Cognitive Functioning, General Health and Incidence of Mental Disorders in Patients With Traumatic Brain Injury

Background: Neurosurgical treatment and the severity of head injury (HI) can have remarkable effect on patients’ neuropsychiatric outcomes. Objectives: This research aimed to study the effect of these factors on cognitive functioning, general health and incidence of mental disorders in patients with a traumatic brain injury (TBI). Patients and Methods: In this descriptive, longitudinal study, 206 TBI patients entered the study by consecutive sampling; they were then compared according to neurosurgery status and severity of their HI. Both groups underwent neurosurgical and psychological examinations. The mini mental state examination (MMSE) and general health questionnaire–28 items (GHQ-28) were administered to the study participants. At follow-up, four months later, the groups underwent a structured clinical interview by a psychiatrist based on the diagnostic and statistical manual of mental disorders, fourth edition (DSM-IV) diagnostic criteria regarding the presence of mental disorders. Results: Analysis of covariance (ANCOVA) and multivariate analysis of covariance (MANCOVA) were performed and adjusted for the effect of confounding variables (age, gender, Glasgow outcome scale (GOS) , and level of education). The severity of HI had the most significant effect for the following variables; cognitive functioning and physical symptoms (P < 0.05). The effect of the neurosurgical treatment factor was not significant; however, the interaction effect of the two variables on social dysfunction, and total score of the GHQ-28 questionnaire appeared to be significant (P < 0.05). Fisher\'s exact test indicated that after a four month follow-up period, no significant differences were seen between the two groups (with or without neurosurgery) in the incidence of mental disorders, while x2 Test showed that having a more severe HI is significantly correlated with the incidence of mental disorders (P < 0.01). Conclusions: The implications of this study should be discussed with an emphasis on negative, effective factors on the cognitive – behavioral and neuropsychiatric outcomes of a TBI

Iranian version of speech, spatial, and qualities of hearing scale: A psychometric study

Evaluation of communication abilities in the elderly is crucial for activities which will be performed to improve their quality of life. A valid and reliable questionnaire is needed for assessing communication abilities. We aimed to translate and validate the speech, spatial, and qualities of hearing scale (SSQ) in Iran. The forward-backward procedure was applied to translate the questionnaire from English into Persian. After linguistic validation and pilot study, a cross-sectional study was carried out, and psychometric properties of the Iranian version of the SSQ were tested. Number of 333 elderly individuals with impaired hearing completed the questionnaire. Number 48.3 were hearing aid users and 51.7 was not. Reliability was assessed by internal consistency (Cronbach's alpha) and test-retest analysis. Exploratory factor analysis was performed for extracting factor structure of the Persian version of SSQ. Confirmatory factor analysis was performed to compare different models of factor loadings. The Mean age of participants was 62.00 years (SD=9.58 years), and the mean SSQ score was 5.1 (SD=1.2, ranged: 3.17-6.27). Reliability evaluation revealed high internal consistency and good test- retest reliability. Cronbach's alpha coefficient was 0.96 and the Pierson Correlation at test-retest analysis was 0.73 for Quality of hearing factor, 0.88 for Spatial and o.73 for Speech understanding factor. The results of exploratory factor analysis (EFA) indicated a four-factor solution for P-SSQ that jointly accounted for 52.40 of the variance observed. Confirmatory factor analysis approved the three factor solution but proposed a possible fourth factor. The Iranian version of the SSQ has acceptable psychometric properties, and it will be helpful for assessing different kinds of communication abilities in the Iranian elderly population. © 2016 Tehran University of Medical Sciences. All rights reserved