Evolution of Non-Equilibrium Profile in Adsorbate Layer under Compressive Strain

We investigate the time evolution of an initial step profile separating a bare substrate region from the rest of the compressively strained adsorbate layer near a commensurate to incommensurate transition. The rate of profile evolution as a function of the mismatch, coverage and the strength of the substrate potential are determined by Brownian molecular dynamics simulations. We find that the results are qualitatively similar to those observed for the Pb/Si(111) system. The anomalously fast time evolution and sharpness of the non-equilibrium profile can be understood through the domain wall creation at the boundary and its subsequent diffusion into the interior of the adsorbate layer.Comment: 6 pages, 7 figures, Tribology Letter

Dual paths node-disjoint routing for data salvation in mobile ad hoc

The operational patterns of multifarious backup strategies on AODV-based (Ad-hoc On-Demand Vector) routing protocols are elaborated in this article. To have a broader picture on relevant routing protocols together, variants of AODV-based backup routing protocols are formulated by corresponding algorithms, and also each of them are simulated to obtain the necessary performance metrics for comparisons in terms of packet delivery ratio, average latency delay, and the normalized routing load. Then to make the process of data salvation more efficiently in case of link failure, we explore the possibility of combining the AODV backup routing strategy and on-demand node-disjoint multipath routing protocols. This article proposes an improved approach named DPNR (Dual Paths Node-disjoint Routing) for data salvation, a routing protocol that maintains the only two shortest backup paths in the source and destination nodes. The DPNR scheme can alleviate the redundancy-frames overhead during the process of data salvation by the neighboring intermediate nodes. Our simulation results have demonstrated that DPNR scheme delivers good data delivery performance while restricting the impacts of transmission collision and channel contention. The mathematical rationale for our proposed approach is stated as well

Lifetime elongation for wireless sensor network using queue-based approaches

A wireless sensor network (WSN) is envisioned as a cluster of tiny power-constrained devices with functions of sensing and communications. Sensors closer to a sink node have a larger forwarding traffic burden and consume more energy than nodes further away from the sink. The whole lifetime of WSN is deteriorated because of such an uneven node power consumption patterns, leading to what is known as an energy hole problem (EHP). From open literatures, most research works have focused on how to optimally increase the probability of sleeping states using various wake-up strategies. In this article, we propose a novel power-saving scheme to alleviate the EHP based on the N-policy M/M/1 queuing theory. With little or no extra management cost, the proposed queue-based power-saving technique can be applied to prolong the lifetime of the WSN economically and effectively. A mathematical analysis on the optimal control parameter has been made in detail. Focusing on many-to-one WSN, numerical and network simulation results validate that the proposed approach indeed provides a feasibly cost-effective approach for lifetime elongation of WSN

Temperature-Dependent Anomalies in the Structure of the (001) Surface of LiCu2O2

Surface corrugation functions, derived from elastic helium atom scattering (HAS) diffraction patterns at different temperatures, reveal that the Cu2+ rows in the (001) surface of LiCu2O2 undergo an outward displacement of about 0.15 {\AA} as the surface was cooled down to 140 K. This is probably the first time that isolated one-dimensional magnetic ion arrays were realized, which qualifies the Li1+Cu2+O2-2 surface as a candidate to study one-dimensional magnetism. The rising Cu2+ rows induce a surface incommensurate structural transition along the a-direction. Surface equilibrium analysis showed that the surface Cu2+ ions at bulk-like positions experience a net outward force along the surface normal which is relieved by the displacement. Temperature-dependent changes of the surface phonon dispersions obtained with the aid of inelastic HAS measurements combined with surface lattice dynamical calculations are also reported.Comment: 4 pages, 7 figure

Exact soliton solution and inelastic two-soliton collision in spin chain driven by a time-dependent magnetic field

We investigate dynamics of exact N-soliton trains in spin chain driven by a time-dependent magnetic field by means of an inverse scattering transformation. The one-soliton solution indicates obviously the spin precession around the magnetic field and periodic shape-variation induced by the time varying field as well. In terms of the general soliton solutions N-soliton interaction and particularly various two-soliton collisions are analyzed. The inelastic collision by which we mean the soliton shape change before and after collision appears generally due to the time varying field. We, moreover, show that complete inelastic collisions can be achieved by adjusting spectrum and field parameters. This may lead a potential technique of shape control of soliton.Comment: 5 pages, 5 figure

Pannexin 1 regulates adipose stromal cell differentiation and fat accumulation

Pannexin 1 (Panx1) is a channel-forming glycoprotein important in paracrine signaling and cellular development. In this study, we discovered that mice globally lacking Panx1 (KO) have significantly greater total fat mass and reduced lean mass compared to wild type (WT) mice under a normal diet. Despite having higher fat content, Panx1 KO mice on a high fat diet exhibited no differences in weight gain and blood markers of obesity as compared to WT controls, except for an increase in glucose and insulin levels. However, metabolic cage data revealed that these Panx1 KO mice display significantly increased activity levels, higher ambulatory activity, and reduced sleep duration relative to their WT littermates on a high-fat diet. To uncover the cellular mechanism responsible for the increased fat content in the KO, we isolated primary cultures of adipose-derived stromal cells (ASCs) from WT and KO fat pads. In WT ASCs we observed that Panx1 protein levels increase upon induction into an adipogenic lineage. ASCs isolated from Panx1 KO mice proliferate less but demonstrate enhanced adipogenic differentiation with increased intracellular lipid accumulation, glycerol-3-phosphate dehydrogenase (GPDH) enzyme activity, and adipokine secretion, as compared to WT ASCs. This was consistent with the increased adipocyte size and decreased adipocyte numbers observed in subcutaneous fat of the Panx1 KO mice compared to WT. We concluded that Panx1 plays a key role in adipose stromal cells during the early stages of adipogenic proliferation and differentiation, regulating fat accumulation in vivo

Pairing, Charge, and Spin Correlations in the Three-Band Hubbard Model

Using the Constrained Path Monte Carlo (CPMC) method, we simulated the two-dimensional, three-band Hubbard model to study pairing, charge, and spin correlations as a function of electron and hole doping and the Coulomb repulsion $V_{pd}$ between charges on neighboring Cu and O lattice sites. As a function of distance, both the $d_{x^2 - y^2}$-wave and extended s-wave pairing correlations decayed quickly. In the charge-transfer regime, increasing $V_{pd}$ decreased the long-range part of the correlation functions in both channels, while in the mixed-valent regime, it increased the long-range part of the s-wave behavior but decreased that of the d-wave behavior. Still the d-wave behavior dominated. At a given doping, increasing $V_{pd}$ increased the spin-spin correlations in the charge-transfer regime but decreased them in the mixed-valent regime. Also increasing $V_{pd}$ suppressed the charge-charge correlations between neighboring Cu and O sites. Electron and hole doping away from half-filling was accompanied by a rapid suppression of anti-ferromagnetic correlations.Comment: Revtex, 8 pages with 15 figure

Spacetime Noncommutativity and Antisymmetric Tensor Dynamics in the Early Universe

This paper investigates the possible cosmological implications of the presence of an antisymmetric tensor field related to a lack of commutatitivity of spacetime coordinates at the Planck era. For this purpose, such a field is promoted to a dynamical variable, inspired by tensor formalism. By working to quadratic order in the antisymmetric tensor, we study the field equations in a Bianchi I universe in two models: an antisymmetric tensor plus scalar field coupled to gravity, or a cosmological constant and a free massless antisymmetric tensor. In the first scenario, numerical integration shows that, in the very early universe, the effects of the antisymmetric tensor can prevail on the scalar field, while at late times the former approaches zero and the latter drives the isotropization of the universe. In the second model, an approximate solution is obtained of a nonlinear ordinary differential equation which shows how the mean Hubble parameter and the difference between longitudinal and orthogonal Hubble parameter evolve in the early universe.Comment: 25 pages, Revtex file, 4 figures in attachmen

Striped antiferromagnetic order and electronic properties of stoichiometric LiFeAs from first-principles calculations

We investigate the structural, electronic, and magnetic properties of stoichiometric LiFeAs by using state-of-the-arts first-principles method. We find the magnetic ground-state by comparing the total energies among all the possible magnetic orders. Our calculated internal positions of Li and As are in good agreement with experiment. Our results show that stoichiometric LiFeAs has almost the same striped antiferromagnetic spin order as other FeAs-based parent compounds and tetragonal FeSe do, and the experimental fact that no magnetic phase transition has been observed at finite temperature is attributed to the tiny inter-layer spin coupling

Anomalous c-axis charge dynamics in copper oxide materials

Within the t-J model, the c-axis charge dynamics of the copper oxide materials in the underdoped and optimally doped regimes is studied by considering the incoherent interlayer hopping. It is shown that the c-axis charge dynamics is mainly governed by the scattering from the in-plane fluctuation. In the optimally doped regime, the c-axis resistivity is a linear in temperatures, and shows the metallic-like behavior for all temperatures, while the c-axis resistivity in the underdoped regime is characterized by a crossover from the high temperature metallic-like behavior to the low temperature semiconducting-like behavior, which are consistent with experiments and numerical simulations.Comment: 6 pages, Latex, Three figures are adde