Thermal activation energy of 3D vortex matter in NaFe1-xCoxAs (x=0.01, 0.03 and 0.07) single crystals

We report on the thermally activated flux flow dependency on the doping dependent mixed state in NaFe1-xCoxAs (x=0.01, 0.03, and 0.07) crystals using the magnetoresistivity in the case of B//c-axis and B//ab-plane. It was found clearly that irrespective of the doping ratio, magnetoresistivity showed a distinct tail just above the Tc, offset associated with the thermally activated flux flow (TAFF) in our crystals. Furthermore, in TAFF region the temperature dependence of the activation energy follows the relation U(T, B)=U_0 (B) (1-T/T_c )^q with q=1.5 in all studied crystals. The magnetic field dependence of the activation energy follows a power law of U_0 (B)~B^(-{\alpha}) where the exponent {\alpha} is changed from a low value to a high value at a crossover field of B=~2T, indicating the transition from collective to plastic pinning in the crystals. Finally, it is suggested that the 3D vortex phase is the dominant phase in the low-temperature region as compared to the TAFF region in our series samples

Pacific Ocean Forcing and Atmospheric Variability are the Dominant Causes of Spatially Widespread Droughts in the Contiguous United States

The contributions of oceanic and atmospheric variability to spatially widespread summer droughts in the contiguous United States (hereafter, pan-CONUS droughts) are investigated using 16-member ensembles of the Community Climate Model version 3 (CCM3) forced with observed sea surface temperatures (SSTs) from 1856 to 2012. The employed SST forcing fields are either (i) global or restricted to the (ii) tropical Pacific or (iii) tropical Atlantic to isolate the impacts of these two ocean regions on pan-CONUS droughts. Model results show that SST forcing of pan-CONUS droughts originates almost entirely from the tropical Pacific because of atmospheric highs from the northern Pacific to eastern North America established by La Nia conditions, with little contribution from the tropical Atlantic. Notably, in all three model configurations, internal atmospheric variability influences pan-CONUS drought occurrence by as much or more than the ocean forcing and can alone cause pan-CONUS droughts by establishing a dominant high centered over the US montane West. Similar results are found for the Community Atmosphere Model version 5 (CAM5). Model results are compared to the observational record, which supports model-inferred contributions to pan-CONUS droughts from La Nias and internal atmospheric variability. While there may be an additional association with warm Atlantic SSTs in the observational record, this association is ambiguous due to the limited number of observed pan-CONUS. The ambiguity thus opens the possibility that the observational results are limited by sampling over the 20th-century and not at odds with the suggested dominance of Pacific Ocean forcing in the model ensembles

Ab initio studies of structural and electronic properties of the crystalline Ge(2)Sb(2)Te(5)

We study the atomic structure and the electronic and optical properties of Ge(2)Sb(2)Te(5) in two different crystalline states of cubic and hexagonal structures with the use of ab initio pseudopotential density functional method. It is found that electronic and atomic structures are very sensitive to the layer sequence in the two phases. The proximity of vacancy layer to Ge layer leads to the splitting of Ge-Te bond length, which, in turn, affects the electronic and optical properties. The effect of Te d orbitals is also investigated with respect to structural propertiesopen181

An effective thermodynamic potential from the instanton with Polyakov-loop contributions

We derive an effective thermodynamic potential (Omega_eff) at finite temperature (T>0) and zero quark-chemical potential (mu_R=0), using the singular-gauge instanton solution and Matsubara formula for N_c=3 and N_f=2 in the chiral limit. The momentum-dependent constituent-quark mass is also obtained as a function of T, employing the Harrington-Shepard caloron solution in the large-N_c limit. In addition, we take into account the imaginary quark chemical potential mu_I = A_4, translated as the traced Polayakov-loop (Phi) as an order parameter for the Z(N_c) symmsetry, characterizing the confinement (intact) and deconfinement (spontaneously broken) phases. As a result, we observe the crossover of the chiral (chi) order parameter sigma^2 and Phi. It also turns out that the critical temperature for the deconfinment phase transition, T^Z_c is lowered by about (5-10)% in comparison to the case with a constant constituent-quark mass. This behavior can be understood by considerable effects from the partial chiral restoration and nontrivial QCD vacuum on Phi. Numerical calculations show that the crossover transitions occur at (T^chi_c,T^Z_c) ~ (216,227) MeV.Comment: 15 pages, 7 figure

Curvature-induced spin-orbit coupling and spin relaxation in a chemically clean single-layer graphene

The study of spin-related phenomena in materials requires knowledge on the precise form of effective spin-orbit coupling of conducting carriers in the solid-states systems. We demonstrate theoretically that curvature induced by corrugations or periodic ripples in single-layer graphenes generates two types of effective spin-orbit coupling. In addition to the spin-orbit coupling reported previously that couples with sublattice pseudospin and corresponds to the Rashba-type spin-orbit coupling in a corrugated single-layer graphene, there is an additional spin-orbit coupling that does not couple with the pseudospin, which can not be obtained from the extension of the curvature-induced spin-orbit coupling of carbon nanotubes. Via numerical calculation we show that both types of the curvature-induced spin-orbit coupling make the same order of contribution to spin relaxation in chemically clean single-layer graphene with nanoscale corrugation. The spin relaxation dependence on the corrugation roughness is also studied.Comment: 8 pages, 4 figure

Topological insulating behaviour in conducting property of crystalline Ge-Sb-Te

We report a discovery, through first-principles calculations, that crystalline Ge-Sb-Te (GST) phase-change materials exhibit the topological insulating property. Our calculations show that the materials become topological insulator or develop conducting surface-like interface states depending on the layer stacking sequence. It is shown that the conducting interface states originate from topological insulating Sb2Te3 layers in GSTs and can be crucial to the electronic property of the compounds. These interface states are found to be quite resilient to atomic disorders but sensitive to the uniaxial strains. We presented the mechanisms that destroy the topological insulating order in GSTs and investigated the role of Ge migration that is believed to be responsible for the amorphorization of GSTs.Comment: 13 pages, 4 figure

Exploring changes in open defecation prevalence in sub-Saharan Africa based on national level indices

Background In sub-Saharan Africa, it is estimated that 215 million people continue to engage in open defecation. This practice facilitates the transmission of diarrheal diseases – one of the leading causes of mortality in children under 5 in sub-Saharan Africa. The main purpose of this study is to: estimate changes in open defecation prevalence between 2005 and 2010 across countries in sub-Saharan Africa; examine the association between national level indices and changes in open defecation prevalence; and assess how many countries can achieve ‘open defecation free status’ by 2015. Methods After applying selection criteria, this study analyzed country-level data for 34 sub-Saharan African countries. Seven country-level indices were collected: 1) presence of a national sanitation policy; 2) budget line for sanitation; 3) budget allocated to sanitation; 4) annual per capita GDP; 5) GDP growth; 6) implementation of total sanitation approaches; and 7) per capita aid disbursement for water supply and sanitation. The relationships between these country-level indices and the change in open defecation from 2005 to 2010 were investigated using Wilcoxon Signed-Rank test and Spearman\u27s rank correlation test. Results Only 3 countries (i.e. Ethiopia, Angola and Sao Tome and Principe) decreased open defecation by 10% or more between 2005 and 2010. No significant associations were observed between the change in open defecation prevalence and all of national level indices except per capita aid disbursement. Per capita aid disbursement for water and sanitation was positively associated with a reduction in open defecation (p-value = 0.02) for a subset of 29 low-income countries from 2005 to 2010. Only one country in our analysis, Angola, is on track to end open defecation by 2015 based on their performance between 2000 and 2010. Conclusions Most of the national level indices, including a country’s economic status, were not associated with the change in the open defecation prevalence. Based on current trends, the goal of ending open defecation in the majority of sub-Saharan African countries by 2015 will not be achieved. Our findings may be limited by the exploratory nature of this analysis, and future research is required to identify and characterize national level factors specific to reducing open defecation in sub-Saharan Africa

Phosphorylation of the RB C-terminus regulates condensin II release from chromatin

The retinoblastoma tumor suppressor protein (RB) plays an important role in biological processes such as cell cycle control, DNA damage repair, epigenetic regulation, and genome stability. The canonical model of RB regulation is that cyclin-CDKs phosphorylate and render RB inactive in late G1/S, promoting entry into S phase. Recently, monophosphorylated RB species were described to have distinct cell-cycle-independent functions, suggesting that a phosphorylation code dictates diversity of RB function. However, a biologically relevant, functional role of RB phosphorylation at non-CDK sites has remained elusive. Here, we investigated S838/T841 dual phosphorylation, its upstream stimulus, and downstream functional output. We found that mimicking T-cell receptor activation in Jurkat leukemia cells induced sequential activation of downstream kinases including p38 MAPK and RB S838/ T841 phosphorylation. This signaling pathway disrupts RB and condensin II interaction with chromatin. Using cells expressing a WT or S838A/T841A mutant RB fragment, we present evidence that deficiency for this phosphorylation event prevents condensin II release from chromatin