The Nature of Electronic States in Atomically Thin MoS2 Field-Effect Transistors

We present low temperature electrical transport experiments in five field effect transistor devices consisting of monolayer, bilayer and trilayer MoS2 films, mechanically exfoliated onto Si/SiO2 substrate. Our experiments reveal that the electronic states in all films are localized well up to the room temperature over the experimentally accessible range of gate voltage. This manifests in two dimensional (2D) variable range hopping (VRH) at high temperatures, while below \sim 30 K the conductivity displays oscillatory structures in gate voltage arising from resonant tunneling at the localized sites. From the correlation energy (T0) of VRH and gate voltage dependence of conductivity, we suggest that Coulomb potential from trapped charges in the substrate are the dominant source of disorder in MoS2 field effect devices, which leads to carrier localization as well.Comment: 10 pages, 5 figures; ACS Nano (2011

Hysteretic Optimization

We propose a new optimization method based on a demagnetization procedure well known in magnetism. We show how this procedure can be applied as a general tool to search for optimal solutions in any system where the configuration space is endowed with a suitable `distance'. We test the new algorithm on frustrated magnetic models and the traveling salesman problem. We find that the new method successfully competes with similar basic algorithms such as simulated annealing.Comment: 5 pages, 5 figure

Hydrodynamics of Suspensions of Passive and Active Rigid Particles: A Rigid Multiblob Approach

We develop a rigid multiblob method for numerically solving the mobility problem for suspensions of passive and active rigid particles of complex shape in Stokes flow in unconfined, partially confined, and fully confined geometries. As in a number of existing methods, we discretize rigid bodies using a collection of minimally-resolved spherical blobs constrained to move as a rigid body, to arrive at a potentially large linear system of equations for the unknown Lagrange multipliers and rigid-body motions. Here we develop a block-diagonal preconditioner for this linear system and show that a standard Krylov solver converges in a modest number of iterations that is essentially independent of the number of particles. For unbounded suspensions and suspensions sedimented against a single no-slip boundary, we rely on existing analytical expressions for the Rotne-Prager tensor combined with a fast multipole method or a direct summation on a Graphical Processing Unit to obtain an simple yet efficient and scalable implementation. For fully confined domains, such as periodic suspensions or suspensions confined in slit and square channels, we extend a recently-developed rigid-body immersed boundary method to suspensions of freely-moving passive or active rigid particles at zero Reynolds number. We demonstrate that the iterative solver for the coupled fluid and rigid body equations converges in a bounded number of iterations regardless of the system size. We optimize a number of parameters in the iterative solvers and apply our method to a variety of benchmark problems to carefully assess the accuracy of the rigid multiblob approach as a function of the resolution. We also model the dynamics of colloidal particles studied in recent experiments, such as passive boomerangs in a slit channel, as well as a pair of non-Brownian active nanorods sedimented against a wall.Comment: Under revision in CAMCOS, Nov 201

Bliss v. Attorney General of Canada: From Legal Defeat to Political Victory

This article rests on the distinction between the legal and political meanings of a judicial decision. Cases that are resolved in legal terms may have unpredictable political consequences. Bliss v. Attorney General of Canada (1978) demonstrates this brilliantly: Stella Bliss\u27s argument that Canadian Unemployment Insurance maternity benefits violated the equality provisions of the Bill of Rights was soundly defeated in the court& Ultimately, however, a loose coalition of feminist and civil liberties groups took Bliss into the political process and succeeded in forcing a revision of Unemployment Insurance along with a dramatic expansion of the scope of section 15 of the Canadian Charter of Rights and Freedoms. The article traces the complex transition from personal case to political cause, demonstrating that Supreme Court decisions have a specious finality: disputes may only be conclusively resolved by a broader political process wherein organizational strength, not legal principle, prevails

Problem Solving Approach

Problem is something that we can never get rid of, how much we try and howmany anticipatory actions we take. Therefore, to deal with problems in our everyday life, every project implementation is to solve the problem as and when required. In this article we will try and study about problems and the techniques and methods by which we can solve it or mitigate the situation. Again it is worthy to mention as a prelude and also to conclude that problem solving is an individual skill and it therefore varies from person to person and from situation to situation and there exist no thumb rule to redress ay problem as a generalized rule. By the end of this article, we will try and develop certain tools by which we may approach a problematic situation before redressing the problem

Supermetallic conductivity in bromine-intercalated graphite

Exposure of highly oriented pyrolytic graphite to bromine vapor gives rise to in-plane charge conductivities which increase monotonically with intercalation time toward values (for ~6 at% Br) that are significantly higher than Cu at temperatures down to 5 K. Magnetotransport, optical reflectivity and magnetic susceptibility measurements confirm that the Br dopes the graphene sheets with holes while simultaneously increasing the interplanar separation. The increase of mobility (~ 5E4 cm^2/Vs at T=300 K) and resistance anisotropy together with the reduced diamagnetic susceptibility of the intercalated samples suggests that the observed supermetallic conductivity derives from a parallel combination of weakly-coupled hole-doped graphene sheets.Comment: 5 pages, 4 figure

Tripartite thermal correlations in an inhomogeneous spin-star system

We exploit the tripartite negativity to study the thermal correlations in a tripartite system, that is the three outer spins interacting with the central one in a spin-star system. We analyze the dependence of such correlations on the homogeneity of the interactions, starting from the case where central-outer spin interactions are identical and then focusing on the case where the three coupling constants are different. We single out some important differences between the negativity and the concurrence.Comment: 8 pages, 9 figure

Gravitational coupling of neutrinos in a medium

In a medium that contains electrons but not the other charged leptons, such as normal matter, the gravitational interactions of neutrinos are not the same for all the neutrino flavors. We calculate the leading order matter-induced corrections to the neutrino gravitational interactions in such a medium and consider some of their physical implications.Comment: 21 pages, Latex, uses axodraw.sty (typos corrected; two references added. To appear in Phys. Rev. D

Minimal extended flavor groups, matter fields chiral representations, and the flavor question

We show the specific unusual features on chiral gauge anomalies cancellation in the minimal, necessarily 3-3-1, and the largest 3-4-1 weak isospin chiral gauge semisimple group leptoquark-bilepton extensions of the 3-2-1 conventional standard model of nuclear and electromagnetic interactions. In such models a natural explanation for the fundamental question of fermion generation replication arises from the self-consistency of a local gauge quantum field theory, which constrains the number of the QFD fermion families to the QCD color charges.Comment: 10 pages. <[email protected]

A comparison of severe pre-eclampsia/eclampsia in patients with and without HELLP syndrome

Background: The relationship of Haemolysis, Elevated Liver Enzymes and Low Platelets (HELLP) syndrome with maternal and perinatal health and its presentation in Pakistani population is not known.Purpose: To determine the mode of presentation along with maternal and perinatal outcome of patients with HELLP syndrome.Methods: Case records of patients with severe hypertension in pregnancy who delivered between January 1, 1989 and December 31, 1994 at The Aga Khan University Hospital, Karachi. Out of 120 cases of severe pre-eclampsia/eclampsia, there were 36 cases of HELLP syndrome (Group-A). These were then compared with cases without HELLP syndrome (Group B) for their mode of presentation along with maternal and perinatal morbidity and mortality.Results: The overall incidence of HELLP syndrome was 0.4%. In the antepartum factors; unbooked status (66% vs 30%; p \u3c 0.05), diastolic B.P. \u3e 120 mmHg (61% vs 16%; p \u3c 0.05) DIC (13% vs 2%; p = 0.03), seizures (40% vs 16%, p = 0.01) and ARF (11% vs 1%, p = 0.07) were significantly raised. In the intrapartum factors there were no significant differences between the two groups in mode of delivery and complications of delivery. Neonatal outcomes did not differ significantly in the two groups.Conclusions: Women with severe hypertension in pregnancy manifesting with HELLP syndrome show a significantly greater frequency of developing DIC, seizures and acute renal failure. Therefore, their care necessitates intensive monitoring to preclude development of these complications