Finite Conductivity Minimum in Bilayer Graphene without Charge Inhomogeneities

Boltzmann transport theory fails near the linear band-crossing of single-layer graphene and near the quadratic band-crossing of bilayer graphene. We report on a numerical study which assesses the role of inter-band coherence in transport when the Fermi level lies near the band-crossing energy of bilayer graphene. We find that interband coherence enhances conduction, and that it plays an essential role in graphene's minimum conductivity phenomena. This behavior is qualitatively captured by an approximate theory which treats inter-band coherence in a relaxation-time approximation. On the basis of this short-range-disorder model study, we conclude that electron-hole puddle formation is not a necessary condition for finite conductivity in graphene at zero average carrier density.Comment: revised version as published in Phys. Rev.

Numerical simulation of an air-supported structure in the air flow

Wind load is often the critical load for air-supported structures. For example, high wind demolished an air-supported tennis court roof in Zhulebino district of Moscow on May 29, 2017. Aerodynamic instability (buffeting, flutter, etc.) can produce excessive slack regions and extremely large deflections. That is why the coupled analysis should be carried out to understanding aeroelastic behavior of air-supported structures under wind loads. The technique of the nonlinear numerical analysis of air-supported structures including fluidstructural interaction (FSI) has been described in the present paper. Numerical simulation of the tunnel test of large-scale air-supported model has been carried out as an example of using this technique. Wind tunnel study is described in the papers1, 2. Experimental deformed shape, pressure coefficients and aerodynamic forces were compared with the results of presented numerical simulation. Computations were carried out with using of commercial code ANSYS 15.0. Some difficulties appeared during simulation process are discussed. An applicability of the proposed technique to the considered problem was confirmed by a good agreement of the experimental and numerical results. Both methods showed that surface wind loads can increase due to deformation of a structure. These conclusions emphasize the importance of researches on wind interaction with air-supported structures

COVID-19 & Quarantine Measures: A Comparison between India & Russia

The Governments of the different countries are taking a wide range of measures in response to the COVID-19 outbreak. For assessing the rigour of quarantine measures, the Blavatnik School of Government at the University of Oxford has launched the world`'s first COVID-19 government response tracker—the Oxford Coronavirus Government Response Tracker – OxCGRT). This tool aims to track and compare policy responses of governments around the world, rigorously and consistently. According to the COVID-19 Government Response Stringency Index (GRSI) the strictest measures are in India (97.37 points) and less stringent ones are in the Russian Federation (63.89 points). The study compares restrictive measures in India and Russia, analyses their impact on the spread of COVID-19; and estimates mortality rates. Besides, the study also probes population coverage aimed at diagnosing through the use of testing methods and possible economic consequences of quarantine measures

Equilibrium shape and dislocation nucleation in strained epitaxial nanoislands

We study numerically the equilibrium shapes, shape transitions and dislocation nucleation of small strained epitaxial islands with a two-dimensional atomistic model, using simple interatomic pair potentials. We first map out the phase diagram for the equilibrium island shapes as a function of island size (up to N = 105 atoms) and lattice misfit with the substrate and show that nanoscopic islands have four generic equilibrium shapes, in contrast with predictions from the continuum theory of elasticity. For increasing substrate-adsorbate attraction, we find islands that form on top of a finite wetting layer as observed in Stranski-Krastanow growth. We also investigate energy barriers and transition paths for transitions between different shapes of the islands and for dislocation nucleation in initially coherent islands. In particular, we find that dislocations nucleate spontaneously at the edges of the adsorbate-substrate interface above a critical size or lattice misfit.Comment: 4 pages, 3 figures, uses wrapfig.sty and epsfig.st

Quantum transport in a curved one-dimensional quantum wire with spin-orbit interactions

The one-dimensional effective Hamiltonian for a planar curvilinear quantum wire with arbitrary shape is proposed in the presence of the Rashba spin-orbit interaction. Single electron propagation through a device of two straight lines conjugated with an arc has been investigated and the analytic expressions of the reflection and transmission probabilities have been derived. The effects of the device geometry and the spin-orbit coupling strength $\alpha$ on the reflection and transmission probabilities and the conductance are investigated in the case of spin polarized electron incidence. We find that no spin-flip exists in the reflection of the first junction. The reflection probabilities are mainly influenced by the arc angle and the radius, while the transmission probabilities are affected by both spin-orbit coupling and the device geometry. The probabilities and the conductance take the general behavior of oscillation versus the device geometry parameters and $\alpha$. Especially the electron transportation varies periodically versus the arc angle $\theta_{w}$. We also investigate the relationship between the conductance and the electron energy, and find that electron resonant transmission occurs for certain energy. Finally, the electron transmission for the incoming electron with arbitrary state is considered. For the outgoing electron, the polarization ratio is obtained and the effects of the incoming electron state are discussed. We find that the outgoing electron state can be spin polarization and reveal the polarized conditions.Comment: 7 pages, 8 figure

Effects of oil extraction and recreational load on forest bird communities during the post-nesting period

Effects of recreational load and oil extraction on forest bird communities during the post-nesting period are considered in the article. Ornithocomplexes from recreation areas, places of oil extraction and ecosystems with lower anthropogenic press (Nizhnyaya Kama National Park, Republic of Tatarstan, Russia) were compared based on several indices. The lowest values of Shannon's index, Berger-Parker's index, species diversity, total density of population and maximum species density were observed in the forest bird communities of undisturbed areas. The highest values of the above-said indices were found in the forest areas, suffering from active recreation. The places of oil extraction occupy an intermediate position when their values for each of the indices are considered. The evenness index was highest for bird communities, inhabiting undisturbed areas. It was demonstrated that the effect of recreational load and oil extraction on forest ecosystems can be retraced from the basic indices calculated for bird communities during the post-nesting period. © IDOSI Publications, 2013

The Problem of Water and Sanitation on the Example of India and Russia

Despite the efforts of the United Nations General Assembly to promote sustainability as a vehicle of resource management and tackle social inequalities through the 17 Sustainable Development Goals, the challenges remain. Therefore, the need to solve the fundamental problem of life “water-energy-food” (henceforth WEF) creates the basis for an integrated approach to eliminating the obstacles that arise on the path of sustainable life evolution on Earth. The WEF concept based on a socio-ecological systemic approach is a platform for the most rational approach to solving complex problems and adapting to climate change. At the same time it contributes to regional economic development. Taking examples from India and Russia, this commentary aims to highlight the challenges of water and sanitation of the world

Polarization-sensitive absorption of THz radiation by interacting electrons in chirally stacked multilayer graphene

We show that opacity of a clean multilayer graphene flake depends on the helicity of the circular polarized electromagnetic radiation. The effect can be understood in terms of the pseudospin selection rules for the interband optical transitions in the presence of exchange electron-electron interactions which alter the pseudospin texture in momentum space. The interactions described within a semi-analytical Hartree--Fock approach lead to the formation of the topologically different broken--symmetry states characterized by Chern numbers and zero-field anomalous Hall conductivities.Comment: 6 pages, final versio

Development of methodology for detection of ecological maximum permissible concentration of xenobiotics (on the example of pyrethroid insecticides)

The current aquatic legislation in Russia is based on two basic strategies of defense, conservation and improvement of quality of nature reservoirs. Leading direction in the area of experimental and practical ecology is development of methodology for detection of ecological MPC of xenobiotics considering physiological properties of aquatic population since this methodology is not created all over the world yet. Considering the revealed effect of the action of low and ultralow doses of pyrethroid insecticides to aquatic arthropodas, we corrected previous approach for assessment of ecologic MAC for hazardous substances. On the present stage of investigations, the following basic universal principles for detection of aquatic ecologic MAC for xenobiotics were stated. © IDOSI Publications, 2013