Magnetoresistance in granular magnetic tunnel junctions with Fe nanoparticles embedded in ZnSe semiconducting epilayer

We have investigated transport properties of iron (Fe) nanoparticles embedded in zinc selenide (ZnSe) semiconducting epilayers prepared by molecular beam epitaxy. Both positive and negative tunneling magnetoresistances (TMRs) were measured depending on the applied voltage biases and on the temperature. A slow reduction of the TMR magnitude with temperature was detected and it could be explained in terms of a crossover between direct/resonant tunneling and variable range hopping. The temperature behavior of the magnetoresistance is a clear signature of tunneling and hopping mechanisms mediated by the ZnSe barrier localized states. (C) 2008 American Institute of Physics.1031

Hepatitis C Virus Infection in Guinea-Bissau: A Sexually Transmitted Genotype 2 with Parenteral Amplification?

BACKGROUND: Sub-Saharan Africa is the continent with the highest prevalence of Hepatitis C virus (HCV) infection. Genotype 2 HCV is thought to have originated from West Africa several hundred years ago. Mechanisms of transmission remain poorly understood. METHODOLOGY/PRINCIPAL FINDINGS: To delineate mechanisms for HCV transmission in West Africa, we conducted a cross-sectional survey of individuals aged ≥50 years in Bissau, Guinea-Bissau. Dried blood spots were obtained for HCV serology and PCR amplification. Prevalence of HCV was 4.4% (47/1066) among women and 5.0% (27/544) among men. In multivariate analysis, the independent risk factors for HCV infection were age (baseline: 50–59 y; 60–69 y, adjusted odds ratio [AOR]: 1.67, 95% CI: 0.91–3.06; ≥70 y, AOR: 3.47, 95% CI: 1.89–6.39), belonging to the Papel, Mancanha, Balanta or Mandjako ethnic groups (AOR: 2.45, 95% CI:1.32–4.53), originating from the Biombo, Cacheu or Oio regions north of Bissau (AOR: 4.16, 95% CI: 1.18–14.73) and having bought or sold sexual services (AOR: 3.60, 95% CI: 1.88–6.89). Of 57 isolates that could be genotyped, 56 were genotype 2. CONCLUSIONS: Our results suggest that transmission of HCV genotype 2 in West Africa occurs through sexual intercourse. In specific locations and subpopulations, medical interventions may have amplified transmission parenterally

Differential Regional Immune Response in Chagas Disease

Following infection, lymphocytes expand exponentially and differentiate into effector cells to control infection and coordinate the multiple effector arms of the immune response. Soon after this expansion, the majority of antigen-specific lymphocytes die, thus keeping homeostasis, and a small pool of memory cells develops, providing long-term immunity to subsequent reinfection. The extent of infection and rate of pathogen clearance are thought to determine both the magnitude of cell expansion and the homeostatic contraction to a stable number of memory cells. This straight correlation between the kinetics of T cell response and the dynamics of lymphoid tissue cell numbers is a constant feature in acute infections yielded by pathogens that are cleared during the course of response. However, the regional dynamics of the immune response mounted against pathogens that are able to establish a persistent infection remain poorly understood. Herein we discuss the differential lymphocyte dynamics in distinct central and peripheral lymphoid organs following acute infection by Trypanosoma cruzi, the causative agent of Chagas disease. While the thymus and mesenteric lymph nodes undergo a severe atrophy with massive lymphocyte depletion, the spleen and subcutaneous lymph nodes expand due to T and B cell activation/proliferation. These events are regulated by cytokines, as well as parasite-derived moieties. In this regard, identifying the molecular mechanisms underlying regional lymphocyte dynamics secondary to T. cruzi infection may hopefully contribute to the design of novel immune intervention strategies to control pathology in this infection

Observation of associated near-side and away-side long-range correlations in √sNN=5.02 TeV proton-lead collisions with the ATLAS detector

Two-particle correlations in relative azimuthal angle (Δϕ) and pseudorapidity (Δη) are measured in √sNN=5.02  TeV p+Pb collisions using the ATLAS detector at the LHC. The measurements are performed using approximately 1  μb-1 of data as a function of transverse momentum (pT) and the transverse energy (ΣETPb) summed over 3.1<η<4.9 in the direction of the Pb beam. The correlation function, constructed from charged particles, exhibits a long-range (2<|Δη|<5) “near-side” (Δϕ∼0) correlation that grows rapidly with increasing ΣETPb. A long-range “away-side” (Δϕ∼π) correlation, obtained by subtracting the expected contributions from recoiling dijets and other sources estimated using events with small ΣETPb, is found to match the near-side correlation in magnitude, shape (in Δη and Δϕ) and ΣETPb dependence. The resultant Δϕ correlation is approximately symmetric about π/2, and is consistent with a dominant cos⁡2Δϕ modulation for all ΣETPb ranges and particle pT

Search for the neutral Higgs bosons of the minimal supersymmetric standard model in pp collisions at root s=7 TeV with the ATLAS detector

A search for neutral Higgs bosons of the Minimal Supersymmetric Standard Model (MSSM) is reported. The analysis is based on a sample of proton-proton collisions at a centre-of-mass energy of 7TeV recorded with the ATLAS detector at the Large Hadron Collider. The data were recorded in 2011 and correspond to an integrated luminosity of 4.7 fb-1 to 4.8 fb-1. Higgs boson decays into oppositely-charged muon or τ lepton pairs are considered for final states requiring either the presence or absence of b-jets. No statistically significant excess over the expected background is observed and exclusion limits at the 95% confidence level are derived. The exclusion limits are for the production cross-section of a generic neutral Higgs boson, φ, as a function of the Higgs boson mass and for h/A/H production in the MSSM as a function of the parameters mA and tan β in the mhmax scenario for mA in the range of 90GeV to 500 GeV. Copyright CERN

Search for R-parity-violating supersymmetry in events with four or more leptons in sqrt(s) =7 TeV pp collisions with the ATLAS detector

A search for new phenomena in final states with four or more leptons (electrons or muons) is presented. The analysis is based on 4.7 fb−1 of $\sqrt{s}=7\;\mathrm{TeV}$ proton-proton collisions delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with Standard Model expectations in two signal regions: one that requires moderate values of missing transverse momentum and another that requires large effective mass. The results are interpreted in a simplified model of R-parity-violating supersymmetry in which a 95% CL exclusion region is set for charged wino masses up to 540 GeV. In an R-parity-violating MSUGRA/CMSSM model, values of m 1/2 up to 820 GeV are excluded for 10 < tan β < 40

Search for high-mass resonances decaying to dilepton final states in pp collisions at s√=7 TeV with the ATLAS detector

The ATLAS detector at the Large Hadron Collider is used to search for high-mass resonances decaying to an electron-positron pair or a muon-antimuon pair. The search is sensitive to heavy neutral Z′ gauge bosons, Randall-Sundrum gravitons, Z * bosons, techni-mesons, Kaluza-Klein Z/γ bosons, and bosons predicted by Torsion models. Results are presented based on an analysis of pp collisions at a center-of-mass energy of 7 TeV corresponding to an integrated luminosity of 4.9 fb−1 in the e + e − channel and 5.0 fb−1 in the μ + μ −channel. A Z ′ boson with Standard Model-like couplings is excluded at 95 % confidence level for masses below 2.22 TeV. A Randall-Sundrum graviton with coupling k/MPl=0.1 is excluded at 95 % confidence level for masses below 2.16 TeV. Limits on the other models are also presented, including Technicolor and Minimal Z′ Models