Orbital order in bilayer graphene at filling factor ν=−1\nu =-1

In a graphene bilayer with Bernal stacking both $n=0$ and $n=1$ orbital Landau levels have zero kinetic energy. An electronic state in the N=0 Landau level consequently has three quantum numbers in addition to its guiding center label: its spin, its valley index $K$ or $K^{\prime}$, and an orbital quantum number $n=0,1.$ The two-dimensional electron gas (2DEG) in the bilayer supports a wide variety of broken-symmetry states in which the pseudospins associated these three quantum numbers order in a manner that is dependent on both filling factor $\nu$ and the electric potential difference between the layers. In this paper, we study the case of $\nu =-1$ in an external field strong enough to freeze electronic spins. We show that an electric potential difference between layers drives a series of transitions, starting from interlayer-coherent states (ICS) at small potentials and leading to orbitally coherent states (OCS) that are polarized in a single layer. Orbital pseudospins carry electric dipoles with orientations that are ordered in the OCS and have Dzyaloshinskii-Moriya interactions that can lead to spiral instabilities. We show that the microwave absorption spectra of ICSs, OCSs, and the mixed states that occur at intermediate potentials are sharply distinct.Comment: 21 pages, 14 figure

Orbital and interlayer Skyrmions crystals in bilayer graphene

A graphene bilayer in a transverse magnetic field has a set of Landau levels with energies $E=\pm \sqrt{N(N+1)}\hslash \omega_{c}^{\ast}$ where $\omega_{c}^{\ast}$ is the effective cyclotron frequency and $$ All Landau levels but N=0 are four times degenerate counting spin and valley degrees of freedom. The Landau level N=0 has an extra degeneracy due to the fact that orbitals $n=0$ and $n=1$ both have zero kinetic energies. At integer filling factors, Coulomb interactions produce a set of broken-symmetry states with partial or full alignement in space of the valley and orbital pseudospins. These quantum Hall pseudo-ferromagnetic states support topological charged excitations in the form of orbital and valley Skyrmions. Away from integer fillings, these topological excitations can condense to form a rich variety of Skyrme crystals with interesting properties. We study in this paper different crystal phases that occur when an electric field is applied between the layers. We show that orbital Skyrmions, in analogy with spin Skyrmions, have a texture of electrical dipoles that can be controlled by an in-plane electric field. Moreover, the modulation of electronic density in the crystalline phases are experimentally accessible through a measurement of their local density of statesComment: 18 pages with 13 figure

The Role of Electron-electron Interactions in Graphene ARPES Spectra

We report on a theoretical study of the influence of electron-electron interactions on ARPES spectra in graphene that is based on the random-phase-approximation and on graphene's massless Dirac equation continuum model. We find that level repulsion between quasiparticle and plasmaron resonances gives rise to a gap-like feature at small k. ARPES spectra are sensitive to the electron-electron interaction coupling strength $\alpha_{\rm gr}$ and might enable an experimental determination of this material parameter.Comment: 5 Pages, 4 Figures, Submitte

Still Quarrelling over the Quran Five Interventions

In this article, Barlas joins the debates on the right and authority of Muslim women to interpret the Quran.1 As a way to move the conversation beyond simply asserting or refuting the right of this or that person to read the Quran on this or that condition, she distinguishes between different types of interpretations and authority. Simultaneously, she attempts to come to grips with the tensions between an individual believer’s reading of the Quran and that of the community

A STUDY ON THE IDENTIFICATION OF FIRE HAZARDS ON BOARD: A CASE STUDY

The RoRo ship MS UND ADRIYATIK was wrecked in February 2008 by a catastrophic fire. The causes of the accident included a combination of human, technical and organizational factors. In this study, the authors describe the accident, its chronology, and the dependencies involved. They then examine some of the erroneous series of human’s operations, design and technical errors that led to the disaster and their organizational roots at the time of the accident. Risk-reduction measures can be costly, though; priorities must be set based on costs and benefits. This research suggests ways to support fire prevention efforts. Nine possible reasons were determined to perform a survey suitable for AHP technique. The purpose of this survey is to determine the order of possible explanations for this fire accident and possible provisions and precautions to be taken

Incidence of epizootic ulcerative syndrome (EUS) in freshwater fishes in the endemic area of Punjab, Pakistan

Incidence of Epizootic Ulcerative Syndrome (EUS) has been recorded for the first time in freshwater fishes in the endemic area of Punjab, Pakistan. Survey of private fish farms, hatchery and natural water bodies was conducted in a radius of 14 Km from around river Ravi near Lahore (Punjab Province) Pakistan. Out Of 1628 fishes belonging to 18 genera, 517 fishes of 10 genera were found affected with EUS. The incidence of EUS in culturable fishes was higher in Cirrhina mrigala (15.4%) moderate in Catla cat/a (13.3%) and lower in Labeo rohita (5.0%). Exotic fish, Chinese carp Ctenoparyngodon idella and Hypophthalmicthys molitrix were not affected with EUS. In non-culturable fishes the incidence of EUS was highest in Channa punctatus (72.8%) moderate in by C. straitus (65.45%) and comparatively lower Puntius ticto (43.7%). A slow growing temperature sensitive Saprolegnia spp. was isolated from all of EUS infected fish species. Aeromonas spp. and Pseudomonas spp. were isolated from the diseased fishes. Ectoparasites viz. Lernaea, Argulus and Triclwdina spp. were also isolated from the skin and gills of infected fish species. The disease was more severe in water having low alkalinity (70 mg/1), hardness (75 mg/1) and low temperature of 10-12 °C

Stability of the k=3 Read-Rezayi state in chiral two-dimensional systems with tunable interactions

The k=3 Read-Rezayi (RR) parafermion quantum Hall state hosts non-Abelian excitations which provide a platform for the universal topological quantum computation. Although the RR state may be realized at the filling factor \nu=12/5 in GaAs-based two-dimensional electron systems, the corresponding quantum Hall state is weak and at present nearly impossible to study experimentally. Here we argue that the RR state can alternatively be realized in a class of chiral materials with massless and massive Dirac-like band structure. This family of materials encompasses monolayer and bilayer graphene, as well as topological insulators. We show that, compared to GaAs, these systems provide several important advantages in realizing and studying the RR state. Most importantly, the effective interactions can be tuned {\it in situ} by varying the external magnetic field, and by designing the dielectric environment of the sample. This tunability enables the realization of RR state with controllable energy gaps in different Landau levels. It also allows one to probe the quantum phase transitions to other compressible and incompressible phases.Comment: 12 pages, 5 figures; to appear in New Journal of Physics, Focus on Topological Quantum Computatio

Prevention of occupational diseases in Turkey : deriving lessons from journey of surveillance

Introduction: To prevent and manage the societal and economic burden of occupational diseases (ODs), countries should develop strong prevention policies, health surveillance and registry systems. This study aims to contribute to the improvement of OD surveillance at national level as well as to identify priority actions in Turkey. Methods: The history and current status of occupational health studies were considered from the perspective of OD surveillance. Interpretative research was done through literature review on occupational health at national, regional and international level. Analyses were focused on countries' experiences in policy development and practice, roles and responsibilities of institutions, multidisciplinary and intersectoral collaboration. OD surveillance models of Turkey, Belgium and the Netherlands were examined through exchange visits. Face-to-face interviews were conducted to explore the peculiarities of legislative and institutional structures, the best and worst practices, and approach principles. Results: Some countries are more focused on exploring OD trends through effective and cost-efficient researches, with particular attention to new and emerging ODs. Other countries try to reach every single case of OD for compensation and rehabilitation. Each practice has advantages and shortcomings, but they are not mutually exclusive, and thus an effective combination is possible. Conclusion: Effective surveillance and registry approaches play a key role in the prevention of ODs. A well-designed system enables monitoring and assessment of OD prevalence and trends, and adoption of preventive measures while improving the effectiveness of redressing and compensation. A robust surveillance does not only provide protection of workers' health but also advances prevention of economic losses