Magnon Heat Transport in (Sr,La)_14Cu_24O_41

We have measured the thermal heat conductivity kappa of the compounds Sr_14Cu_24O_41 and Ca_9La_5Cu_24O_41 containing doped and undoped spin ladders, respectively. We find a huge anisotropy of both, the size and the temperature dependence of kappa which we interpret in terms of a very large heat conductivity due to the magnetic excitations of the one-dimensional spin ladders. This magnon heat conductivity decreases with increasing hole doping of the ladders. The magnon heat transport is analyzed theoretically using a simple kinetic model. From this analysis we determine the spin gap and the temperature dependent mean free path of the magnons which ranges by several thousand angstroms at low temperature. The relevance of several scattering channels for the magnon transport is discussed.Comment: 6 pages, 5 figures, submitted to Phys. Rev.

Peptide mimics selected from immune sera using phage display technology can replace native antigens in the diagnosis of Epstein–Barr virus infection

There is an expanding area of small molecule discovery, especially in the area of peptide mimetics. Peptide sequences can be used to substitute for the entire native antigen for use in diagnostic assays. Our approach is to select peptides that mimic epitopes of the natural immune response to Epstein–Barr virus (EBV) that may be recognised by antibodies typically produced after infection with EBV. We screened a random peptide library on sera from rabbits immunised with a crude preparation of EBV and serum antibodies from a patient with a high titer of EBV antibodies. We selected four peptides (Eb1–4) with the highest relative binding affinity with immune rabbit sera and a single peptide with high affinity to human serum antibodies. The peptides were coupled to the carrier molecule BSA and the recognition of the peptides by IgM antibodies in clinical samples after infection with EBV was measured. The sensitivities were Eb1 94%, Eb2, 3, 4 88%, H1 81% and all had 100% specificity. This study illustrates that the phage display approach to select epitope mimics can be applied to polyclonal antibodies and peptides that represent several diagnostically important epitopes can be selected simultaneously. This panel of EBV peptides representing a wide coverage of immunodominant epitopes could replace crude antigen preparations currently used for capture in commercial diagnostic tests for EBV

Phonon thermal conductivity in doped La2CuO4\rm\bf La_2CuO_4: Relevant scattering mechanisms

Results of in-plane and out-of-plane thermal conductivity measurements on $\rm La_{1.8-x}Eu_{0.2}Sr_xCuO_4$ ($0\leq x\leq0.2$) single crystals are presented. The most characteristic features of the temperature dependence are a pronounced phonon peak at low temperatures and a steplike anomaly at $T_{LT}$, i.e., at the transition to the low temperature tetragonal phase (LTT-phase), which gradually decrease with increasing Sr-content. Comparison of these findings with the thermal conductivity of $\rm La_{2-x}Sr_xCuO_4$ and $\rm La_2NiO_4$ clearly reveals that in $\rm La_{2-x}Sr_xCuO_4$ the most effective mechanism for phonon scattering is impurity-scattering (dopants), as well as scattering by soft phonons that are associated with the lattice instability in the low temperature orthorhombic phase (LTO-phase). There is no evidence that stripe correlations play a major role in suppressing the phonon peak in the thermal conductivity of $\rm La_{2-x}Sr_xCuO_4$.Comment: 7 pages, 4 figure

Rheological Chaos in a Scalar Shear-Thickening Model

We study a simple scalar constitutive equation for a shear-thickening material at zero Reynolds number, in which the shear stress \sigma is driven at a constant shear rate \dot\gamma and relaxes by two parallel decay processes: a nonlinear decay at a nonmonotonic rate R(\sigma_1) and a linear decay at rate \lambda\sigma_2. Here \sigma_{1,2}(t) = \tau_{1,2}^{-1}\int_0^t\sigma(t')\exp[-(t-t')/\tau_{1,2}] {\rm d}t' are two retarded stresses. For suitable parameters, the steady state flow curve is monotonic but unstable; this arises when \tau_2>\tau_1 and 0>R'(\sigma)>-\lambda so that monotonicity is restored only through the strongly retarded term (which might model a slow evolution of material structure under stress). Within the unstable region we find a period-doubling sequence leading to chaos. Instability, but not chaos, persists even for the case \tau_1\to 0. A similar generic mechanism might also arise in shear thinning systems and in some banded flows.Comment: Reference added; typos corrected. To appear in PRE Rap. Com

Nernst Effect of stripe ordering La1.8−x_{1.8-x}Eu0.2_{0.2}Srx_xCuO4_4

We investigate the transport properties of La$_{1.8-x}$Eu$_{0.2}$Sr$_x$CuO$_4$ ($x=0.04$, 0.08, 0.125, 0.15, 0.2) with a special focus on the Nernst effect in the normal state. Various anomalous features are present in the data. For $x=0.125$ and 0.15 a kink-like anomaly is present in the vicinity of the onset of charge stripe order in the LTT phase, suggestive of enhanced positive quasiparticle Nernst response in the stripe ordered phase. At higher temperature, all doping levels except $x=0.2$ exhibit a further kink anomaly in the LTO phase which cannot unambiguously be related to stripe order. Moreover, a direct comparison between the Nernst coefficients of stripe ordering La$_{1.8-x}$Eu$_{0.2}$Sr$_x$CuO$_4$ and superconducting La$_{2-x}$Sr$_x$CuO$_4$ at the doping levels $x=0.125$ and $x=0.15$ reveals only weak differences. Our findings make high demands on any scenario interpreting the Nernst response in hole-doped cuprates

Conservative Constraints on Dark Matter from the Fermi-LAT Isotropic Diffuse Gamma-Ray Background Spectrum

We examine the constraints on final state radiation from Weakly Interacting Massive Particle (WIMP) dark matter candidates annihilating into various standard model final states, as imposed by the measurement of the isotropic diffuse gamma-ray background by the Large Area Telescope aboard the Fermi Gamma-Ray Space Telescope. The expected isotropic diffuse signal from dark matter annihilation has contributions from the local Milky Way (MW) as well as from extragalactic dark matter. The signal from the MW is very insensitive to the adopted dark matter profile of the halos, and dominates the signal from extragalactic halos, which is sensitive to the low mass cut-off of the halo mass function. We adopt a conservative model for both the low halo mass survival cut-off and the substructure boost factor of the Galactic and extragalactic components, and only consider the primary final state radiation. This provides robust constraints which reach the thermal production cross-section for low mass WIMPs annihilating into hadronic modes. We also reanalyze limits from HESS observations of the Galactic Ridge region using a conservative model for the dark matter halo profile. When combined with the HESS constraint, the isotropic diffuse spectrum rules out all interpretations of the PAMELA positron excess based on dark matter annihilation into two lepton final states. Annihilation into four leptons through new intermediate states, although constrained by the data, is not excluded.Comment: 11 pages, 5 figures. v3: minor revisions, matches version to appear in JCA

Rapid And Durable Responses With The Syk/Jak Inhibitor Cerdulatinib In A Phase 2 Study In Relapsed/Refractory Follicular Lymphoma—Alone Or In Combination With Rituximab

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/149541/1/hon30_2629.pd

An exact expression to calculate the derivatives of position-dependent observables in molecular simulations with flexible constraints

In this work, we introduce an algorithm to compute the derivatives of physical observables along the constrained subspace when flexible constraints are imposed on the system (i.e., constraints in which the hard coordinates are fixed to configuration-dependent values). The presented scheme is exact, it does not contain any tunable parameter, and it only requires the calculation and inversion of a sub-block of the Hessian matrix of second derivatives of the function through which the constraints are defined. We also present a practical application to the case in which the sought observables are the Euclidean coordinates of complex molecular systems, and the function whose minimization defines the constraints is the potential energy. Finally, and in order to validate the method, which, as far as we are aware, is the first of its kind in the literature, we compare it to the natural and straightforward finite-differences approach in three molecules of biological relevance: methanol, N-methyl-acetamide and a tri-glycine peptideComment: 13 pages, 8 figures, published versio

Vortex structure in d-density wave scenario of pseudogap

We investigate the vortex structure assuming the d-density wave scenario of the pseudogap. We discuss the profiles of the order parameters in the vicinity of the vortex, effective vortex charge and the local density of states. We find a pronounced modification of these quantities when compared to a purely superconducting case. Results have been obtained for a clean system as well as in the presence of a nonmagnetic impurity. We show that the competition between superconductivity and the density wave may explain some experimental data recently obtained for high-temperature superconductors. In particular, we show that the d-density wave scenario explains the asymmetry of the gap observed in the vicinity of the vortex core.Comment: 8 pages, 10 figure

Social capital in Russian agricultural production co-operatives

When the Soviet kolkhozy and sovkhozy were converted, a large number of agricultural production co-operatives was created. Most of these co-operatives still exist in Russia and some of them have a strong market position, accounting for almost one-third of the aggregate volume produced by large farms. This study explores whether social capital might be the explanation for this relative success, i.e. that members support their co-operative because they trust their fellow members as well as the leadership. Interviews with co-operative members resulted in 1401 usable answers. The results from an ordered logit model indicate that social capital plays a partial role. Members who consider co-operatives to be an efficient business form value social ties to other members, even though the leadership does not enjoy much social capital