Magnetic, magnetocaloric and magnetotransport properties of RSn_{1+x}Ge_{1-x} compounds (R=Gd, Tb, Er; x=0.1)

We have studied the magnetic, magnetocaloric and magnetotransport properties of RSn1+xGe1-x(R=Gd, Tb, Er; x=0.1) series by means of magnetization, heat capacity and resistivity measurements. It has been found that all the compounds crystallize in the orthorhombic crystal structure described by the centrosymmetric space group Cmcm (No. 63). The magnetic susceptibility and heat capacity data suggest that all the compounds are antiferromagnetic. Large negative values of {\theta}p in case of GdSn1.1Ge0.9 and TbSn1.1Ge0.9 indicate that strong antiferromagnetic interactions are involved, which is also reflected in the magnetization isotherms. On the other hand ErSn1.1Ge0.9 shows weak antiferromagnetic interaction. The heat capacity data have been analyzed by fitting the temperature dependence and the values of {\theta}D and {\gamma} have been estimated. Among these three compounds, ErSn1.1Ge0.9 shows considerable magnetic entropy change of 9.5 J/kg K and an adiabatic temperature change of 3.2 K for a field of 50 kOe. The resistivity data in different temperature regimes have been analyzed and the dominant contributions have been identified. All the compounds show small but positive magnetoresistance.Comment: 23 pages,11 figure

Fluctuating diamagnetism in underdoped high temperature superconductors

The fluctuation induced diamagnetism of underdoped high temperature superconductors is studied in the framework of the Lawrence-Doniach model. By taking into account the fluctuations of the phase of the order parameter only, the latter reduces to a layered XY-model describing a liquid of vortices which can be either thermally excited or induced by the external magnetic field. The diamagnetic response is given by a current-current correlation function which is evaluated using the Coulomb gas analogy. Our results are then applied to recent measurements of fluctuation diamagnetism in underdoped YBCO. They allow to understand both the observed anomalous temperature dependence of the zero-field susceptibility and the two distinct regimes appearing in the magnetic field dependence of the magnetization.Comment: 12 pages, 4 figures included, accepted for publication in PR

Adiabatic perturbation theory: from Landau-Zener problem to quenching through a quantum critical point

We discuss the application of the adiabatic perturbation theory to analyze the dynamics in various systems in the limit of slow parametric changes of the Hamiltonian. We first consider a two-level system and give an elementary derivation of the asymptotics of the transition probability when the tuning parameter slowly changes in the finite range. Then we apply this perturbation theory to many-particle systems with low energy spectrum characterized by quasiparticle excitations. Within this approach we derive the scaling of various quantities such as the density of generated defects, entropy and energy. We discuss the applications of this approach to a specific situation where the system crosses a quantum critical point. We also show the connection between adiabatic and sudden quenches near a quantum phase transitions and discuss the effects of quasiparticle statistics on slow and sudden quenches at finite temperatures.Comment: 20 pages, 3 figures, contribution to "Quantum Quenching, Annealing and Computation", Eds. A. Das, A. Chandra and B. K. Chakrabarti, Lect. Notes in Phys., Springer, Heidelberg (2009, to be published), reference correcte

Bond graph modelling of chemoelectrical energy transduction

Energy-based bond graph modelling of biomolecular systems is extended to include chemoelectrical transduction thus enabling integrated thermodynamically-compliant modelling of chemoelectrical systems in general and excitable membranes in particular. Our general approach is illustrated by recreating a well-known model of an excitable membrane. This model is used to investigate the energy consumed during a membrane action potential thus contributing to the current debate on the trade-off between the speed of an action potential event and energy consumption. The influx of Na+ is often taken as a proxy for energy consumption; in contrast, this paper presents an energy based model of action potentials. As the energy based approach avoids the assumptions underlying the proxy approach it can be directly used to compute energy consumption in both healthy and diseased neurons. These results are illustrated by comparing the energy consumption of healthy and degenerative retinal ganglion cells using both simulated and in vitro data

Nonequilibrium Evolution of Correlation Functions: A Canonical Approach

We study nonequilibrium evolution in a self-interacting quantum field theory invariant under space translation only by using a canonical approach based on the recently developed Liouville-von Neumann formalism. The method is first used to obtain the correlation functions both in and beyond the Hartree approximation, for the quantum mechanical analog of the $\phi^{4}$ model. The technique involves representing the Hamiltonian in a Fock basis of annihilation and creation operators. By separating it into a solvable Gaussian part involving quadratic terms and a perturbation of quartic terms, it is possible to find the improved vacuum state to any desired order. The correlation functions for the field theory are then investigated in the Hartree approximation and those beyond the Hartree approximation are obtained by finding the improved vacuum state corrected up to ${\cal O}(\lambda^2)$. These correlation functions take into account next-to-leading and next-to-next-to-leading order effects in the coupling constant. We also use the Heisenberg formalism to obtain the time evolution equations for the equal-time, connected correlation functions beyond the leading order. These equations are derived by including the connected 4-point functions in the hierarchy. The resulting coupled set of equations form a part of infinite hierarchy of coupled equations relating the various connected n-point functions. The connection with other approaches based on the path integral formalism is established and the physical implications of the set of equations are discussed with particular emphasis on thermalization.Comment: Revtex, 32 pages; substantial new material dealing with non-equilibrium evolution beyond Hartree approx. based on the LvN formalism, has been adde

Safety of elvitegravir, cobicistat, emtricitabine, and tenofovir alafenamide in HIV-1-infected adults with end-stage renal disease on chronic haemodialysis: an open-label, single-arm, multicentre, phase 3b trial

Background: Current treatment for HIV-infected individuals with renal failure on haemodialysis frequently requires complex regimens with multiple pills. A daily single-tablet regimen of coformulated elvitegravir, cobicistat, emtricitabine, and tenofovir alafenamide is approved in Europe, the USA, and in other regions for use in HIV-1-infected individuals with mild-to-moderate chronic kidney disease (creatinine clearance 30–69 mL/min). We aimed to assess the safety, efficacy, and pharmacokinetics of this regimen in HIV-infected adults with end-stage renal disease on chronic haemodialysis. Methods: We did an open-label, single-arm, multicentre, phase 3b trial at 26 outpatient clinics in Austria, France, Germany, and the USA. Participants were HIV-1-infected adults with end-stage renal disease (creatinine clearance <15 mL/min), on chronic haemodialysis for at least 6 months before screening. Virological suppression (ie, plasma HIV-1 RNA <50 copies per mL) on a stable antiretroviral regimen was required for at least 6 months before screening with a CD4 count of at least 200 cells per μL. We switched all participants to coformulated elvitegravir 150 mg, cobicistat 150 mg, emtricitabine 200 mg, and tenofovir alafenamide 10 mg once daily, taken after haemodialysis for up to 96 weeks. We did assessments at study visits at weeks 2, 4, 8, 12, 24, 36, and 48, and every 12 weeks thereafter up to 96 weeks. The primary endpoint was the incidence of treatment-emergent adverse events of grade 3 or higher up to week 48. All participants who received at least one dose of study drug were included in the primary analysis. This study is registered with ClinicalTrials.gov (NCT02600819) and is closed to new participants. Findings: Between Feb 1, and Nov 3, 2016, 55 participants were enrolled and received at least one dose of study drug. Through week 48, 18 of 55 participants (33%, 95% CI 20–45) had an adverse event of grade 3 or higher on study treatment. Treatment-emergent grade 3 or higher adverse events that occurred in more than one participant included anaemia, osteomyelitis, prolonged electrocardiogram QT, fluid overload, hyperkalaemia, hypertension, and hypotension (all n=2). No adverse event of grade 3 or higher was considered by the site investigators to be treatment related. Three participants (5%, 95% CI 0–11) discontinued treatment because of adverse events; one of these (grade 1 allergic pruritus) was considered treatment related. Treatment-related adverse events were reported for six individuals (11%, 95% CI 3–19), the most common of which was nausea (in four individuals [7%]); all treatment-related adverse events were grade 1 or 2 in severity. Interpretation: At 48 weeks, switching to the single-tablet regimen of elvitegravir, cobicistat, emtricitabine, and tenofovir alafenamide was well tolerated. This regimen might provide a tolerable and convenient option for ongoing treatment of HIV-1 infection in adults with end-stage renal disease on chronic haemodialysis. Funding: Gilead Sciences

Search for a W' boson decaying to a bottom quark and a top quark in pp collisions at sqrt(s) = 7 TeV

Results are presented from a search for a W' boson using a dataset corresponding to 5.0 inverse femtobarns of integrated luminosity collected during 2011 by the CMS experiment at the LHC in pp collisions at sqrt(s)=7 TeV. The W' boson is modeled as a heavy W boson, but different scenarios for the couplings to fermions are considered, involving both left-handed and right-handed chiral projections of the fermions, as well as an arbitrary mixture of the two. The search is performed in the decay channel W' to t b, leading to a final state signature with a single lepton (e, mu), missing transverse energy, and jets, at least one of which is tagged as a b-jet. A W' boson that couples to fermions with the same coupling constant as the W, but to the right-handed rather than left-handed chiral projections, is excluded for masses below 1.85 TeV at the 95% confidence level. For the first time using LHC data, constraints on the W' gauge coupling for a set of left- and right-handed coupling combinations have been placed. These results represent a significant improvement over previously published limits.Comment: Submitted to Physics Letters B. Replaced with version publishe

Search for the standard model Higgs boson decaying into two photons in pp collisions at sqrt(s)=7 TeV

A search for a Higgs boson decaying into two photons is described. The analysis is performed using a dataset recorded by the CMS experiment at the LHC from pp collisions at a centre-of-mass energy of 7 TeV, which corresponds to an integrated luminosity of 4.8 inverse femtobarns. Limits are set on the cross section of the standard model Higgs boson decaying to two photons. The expected exclusion limit at 95% confidence level is between 1.4 and 2.4 times the standard model cross section in the mass range between 110 and 150 GeV. The analysis of the data excludes, at 95% confidence level, the standard model Higgs boson decaying into two photons in the mass range 128 to 132 GeV. The largest excess of events above the expected standard model background is observed for a Higgs boson mass hypothesis of 124 GeV with a local significance of 3.1 sigma. The global significance of observing an excess with a local significance greater than 3.1 sigma anywhere in the search range 110-150 GeV is estimated to be 1.8 sigma. More data are required to ascertain the origin of this excess.Comment: Submitted to Physics Letters