Graphene-Dielectric Composite Metamaterials: Evolution from Elliptic to Hyperbolic Wavevector Dispersion and The Transverse Epsilon-Near-Zero Condition

We investigated a multilayer graphene-dielectric composite material, comprising graphene sheets separated by subwavelength-thick dielectric spacer, and found it to exhibit hyperbolic isofrequency wavevector dispersion at far- and mid-infrared frequencies allowing propagation of waves that would be otherwise evanescent in a dielectric. Electrostatic biasing was considered for tunable and controllable transition from hyperbolic to elliptic dispersion. We explored the validity and limitation of the effective medium approximation (EMA) for modeling wave propagation and cutoff of the propagating spatial spectrum due to the Brillouin zone edge. We found that EMA is capable of predicting the transition of the isofrequency dispersion diagram under certain conditions. The graphene-based composite material allows propagation of backward waves under the hyperbolic dispersion regime and of forward waves under the elliptic regime. Transition from hyperbolic to elliptic dispersion regimes is governed by the transverse epsilon-near-zero (TENZ) condition, which implies a flatter and wider propagating spectrum with higher attenuation, when compared to the hyperbolic regime. We also investigate the tunable transparency of the multilayer at that condition in contrast to other materials exhibiting ENZ phenomena.Comment: to be published in Journal of Nanophotonic

Determinants and characteristics of voluntary Internet disclosures in GCC countries

The purpose of this paper is to examine the determinants and characteristics of voluntary Internet disclosures by listed companies in three Gulf Cooperation Council countries. This paper uses archival data from 192 listed companies in Qatar Stock Exchange, Muscat Securities Market, and Bahrain Bourse. Binary Logistic Regression analysis is used to examine the determinants of Internet financial reporting. Kruskal-Wallis test is used to examine the differences in disclosure characteristics among the three countries. The results reveal that firm size is the major influencing factor that impacts Internet financial reporting in the GCC. A number of disclosure characteristics differ significantly between the three countries. The paper provides insights into corporate Internet disclosure in the GCC that will benefit all stakeholders with an interest in corporate reporting in this important region of the world. The results are consistent with previous literature that corporate size is a major determinant of Internet financial reporting

14-Bromo-12-chloro-2,16-dioxapentacyclohenicosa-3(8),10,12,14-tetraene-7,20-dione

In the title compound, C19H16BrClO4, both the fused xanthene rings and one of the cyclohexane rings adopt envelope conformations, while the other cyclohexane ring is in a chair conformation. In the crystal, molecules are linked by C-H...O hydrogen bonds, forming infinite chains running along [10-1] incorporating R22(16) ring motifs. In addition, C-H...[pi] interactions and weak [pi]-[pi] stacking interactions [centroid-centroid distance = 3.768 (3) Å] help to consolidate the packing

Virtual integration platform for computational fluid dynamics

Computational Fluid Dynamics (CFD) tools used in shipbuilding industry involve multiple disciplines, such as resistance, manoeuvring, and cavitation. Traditionally, the analysis was performed separately and sequentially in each discipline, which often resulted in conflict and inconsistency of hydrodynamic prediction. In an effort to solve such problems for future CFD computations, a Virtual Integration Platform (VIP) has been developed in the University of Strathclyde within two EU FP6 projects - VIRTUE and SAFEDOR1. The VIP provides a holistic collaborative environment for designers with features such as Project/Process Management, Distributed Tools Integration, Global Optimisation, Version Management, and Knowledge Management. These features enhance collaboration among customers, ship design companies, shipyards, and consultancies not least because they bring together the best expertise and resources around the world. The platform has been tested in seven European ship design companies including consultancies. Its main functionalities along with advances are presented in this paper with two industrial applications

International ownership and firm performance in Arab economies

This paper aims at filling existing research by examining the impact of corporate governance and ownership structure on firm performance using cross-sectional data from companies in the MENA region for the years 2009-2013. The results indicate that higher ownership concentration is associated with higher returns. Furthermore, firms with higher international ownership share tend to perform better than those with only local private and/or state ownership. The results suggest some prevalent features with respect to ownership and performance of firms in the MENA region. Due to the volatile social and business environment, these firms operate in, they may be particularly dependent on effective ownership structures and support which may be provided by international, institutional, and large shareholders