Electronic structure and superconductivity of BiS2-based compounds LaO1-xFxBiS2

Using the density-functional perturbation theory with structural optimization, we investigate the electronic structure, phonon spectra, and superconductivity of BiS2-based layered compounds LaO1-xFxBiS2. For LaO0.5F0.5BiS2, the calculated electron-phonon coupling constant is equal to lambda = 0.8, and obtained Tc = 9.1 K is very close to its experimental value, indicating that it is a conventional electron-phonon superconductor

Limits from Weak Gravity Conjecture on Dark Energy Models

The weak gravity conjecture has been proposed as a criterion to distinguish the landscape from the swampland in string theory. As an application in cosmology of this conjecture, we use it to impose theoretical constraint on parameters of two types of dark energy models. Our analysis indicates that the Chaplygin-gas-type models realized in quintessence field are in the swampland, whereas the $a$ power-low decay model of the variable cosmological constant can be viable but the parameters are tightly constrained by the conjecture.Comment: Revtex4, 8 pages, 5 figures; References, minor corrections in content, and acknowledgement adde

Plant polyadenylation factors: conservation and variety in the polyadenylation complex in plants

BACKGROUND: Polyadenylation, an essential step in eukaryotic gene expression, requires both cis-elements and a plethora of trans-acting polyadenylation factors. The polyadenylation factors are largely conserved across mammals and fungi. The conservation seems also extended to plants based on the analyses of Arabidopsis polyadenylation factors. To extend this observation, we systemically identified the orthologs of yeast and human polyadenylation factors from 10 plant species chosen based on both the availability of their genome sequences and their positions in the evolutionary tree, which render them representatives of different plant lineages. RESULTS: The evolutionary trajectories revealed several interesting features of plant polyadenylation factors. First, the number of genes encoding plant polyadenylation factors was clearly increased from lower to higher plants. Second, the gene expansion in higher plants was biased to some polyadenylation factors, particularly those involved in RNA binding. Finally, while there are clear commonalities, the differences in the polyadenylation apparatus were obvious across different species, suggesting an ongoing process of evolutionary change. These features lead to a model in which the plant polyadenylation complex consists of a conserved core, which is rather rigid in terms of evolutionary conservation, and a panoply of peripheral subunits, which are less conserved and associated with the core in various combinations, forming a collection of somewhat distinct complex assemblies. CONCLUSIONS: The multiple forms of plant polyadenylation complex, together with the diversified polyA signals may explain the intensive alternative polyadenylation (APA) and its regulatory role in biological functions of higher plants

Conical emission, pulse splitting and X-wave parametric amplification in nonlinear dynamics of ultrashort light pulses

The precise observation of the angle-frequency spectrum of light filaments in water reveals a scenario incompatible with current models of conical emission (CE). Its description in terms of linear X-wave modes leads us to understand filamentation dynamics requiring a phase- and group-matched, Kerr-driven four-wave-mixing process that involves two highly localized pumps and two X-waves. CE and temporal splitting arise naturally as two manifestations of this process

Can the Lepton Flavor Mixing Matrix Be Symmetric?

Current neutrino oscillation data indicate that the 3x3 lepton flavor mixing matrix V is likely to be symmetric about its V_{e3}-V_{\mu 2}-V_{\tau 1} axis. This off-diagonal symmetry corresponds to three pairs of {\it congruent} unitarity triangles in the complex plane. Terrestrial matter effects can substantially modify the genuine CP-violating parameter and off-diagonal asymmetries of V in realistic long-baseline experiments of neutrino oscillations.Comment: RexTex 14 pages (4 PS figures). More discussions adde

Generalized Spring Tensor Model: A New Improved Load Balancing Method in Cloud Computing

Significant characteristics of cloud computing such as elasticity, scalability and payment model attract businesses to replace their legacy infrastructure with the newly offered cloud technologies. As the number of the cloud users is growing rapidly, extensive load volume will affect performance and operation of the cloud. Therefore, it is essential to develop smarter load management methods to ensure effective task scheduling and efficient management of resources. In order to reach these goals, varieties of algorithms have been explored and tested by many researchers. But so far, not many operational load balancing algorithms have been proposed that are capable of forecasting the future load patterns in cloud-based systems. The aim of this research is to design an effective load management tool, characterized by collective behavior of the workflow tasks and jobs that is able to predict various dynamic load patterns occurring in cloud networks. The results show that the proposed new load balancing algorithm can visualize the network load by projecting the existing relationships among submitted tasks and jobs. The visualization can be particularly useful in terms of monitoring the robustness and stability of the cloud systems. © Springer International Publishing Switzerland 2015