Superconductivity Phase Diagram of Na(x)CoO(2).1.3H(2)O

Although the microscopic origin of the superconductivity in high Tc copper oxides remains the subject of active inquiry, several of their electronic characteristics are well established as universal to all the known materials, forming the experimental foundation that all theories must address. The most fundamental of those characteristics is the dependence of the superconducting transition temperature on the degree of electronic band filling. Since the discovery of cuprate superconductivity in 1986 (1), the search for other families of superconductors that might help shed light on the superconducting mechanism of the cuprates has been of great interest. The recent report of superconductivity near 4K in the triangular lattice, layered sodium cobalt oxyhydrate, Na0.35CoO2.1.3H2O, is the best indication that superconductors related to the cuprates may be found (2). Here we show that the superconducting transition temperature of this compound displays the same kind of band-filling behavior that is observed in the cuprates. Specifically, that the optimal superconducting Tc occurs in a narrow range of band filling, and decreases for both underdoped and overdoped materials, in dramatic analogy to the phase diagram of the cuprate superconductors. Our results suggest that characterization of the detailed electronic and magnetic behavior of these new materials may help establish which of the many special characteristics of the cuprates is fundamental to their high Tc superconductivity.Comment: revised, publication information adde

Fermi surface in BaNi2_2P2_2

We report measurements of the de Haas-van Alphen (dHvA) oscillation and a band structure calculation for the pnictide superconductor BaNi$_2$P$_2$, which is isostructural to BaFe$_2$As$_2$, the mother compound of the iron-pnictide high-$T_c$ superconductor (Ba$_{1-x}$K$_x$)Fe$_2$As$_2$. Six dHvA-frequency branches with frequencies up to $\sim$8 kT were observed, and they are in excellent agreement with results of the band-structure calculation. The determined Fermi surface is large, enclosing about one electron and hole per formula unit, and three-dimensional. This is in contrast to the small two-dimensional Fermi surface expected for the iron-pnictide high-$T_c$ superconductors. The mass enhancement is about two.Comment: To appear in J. Phys. Soc. Jpn., Vol. 78, No.

Dimensional crossover and anomalous magnetoresistivity in single crystals NaxCoO2Na_xCoO_2

The in-plane ($\rho_{ab}$) and c-axis ($\rho_c$) resistivities, and the magnetoresistivity of single crystals $Na_xCoO_2$ with x = 0.7, 0.5 and 0.3 were studied systematically. $\rho_{ab}(T)$ shows similar temperature dependence between $Na_{0.3}CoO_2$ and $Na_{0.7}CoO_2$, while $\rho_c(T)$ is quite different. A dimensional crossover from two to three occurs with decreasing Na concentration from 0.7 to 0.3. The angular dependence of in-plane magnetoresistivity for 0.5 sample shows a \emph{"d-wave-like"} symmetry at 2K, while the \emph{"p-wave-like"} symmetry at 20 K. These results give an evidence for existence of a \emph{spin ordering orientation} below 20 K turned by external field, like the stripes in cuprates.Comment: 4 pages, 3 figure

Crystal chemistry aspects of the magnetically induced ferroelectricity in TbMn2O5 and BiMn2O5

The origin of magnetic frustration was stated and the ions whose shift is accompanied by emerging magnetic ordering and ferroelectricity in TbMn2O5 and BiMn2O5 were determined on the basis of calculation of magnetic coupling parameters by using the structural data. The displacements accompanying the magnetic ordering are not polar, they just induce changes of bond valence (charge disordering) of Mn1 and Mn2, thus creating instability of the crystal structure. To approximate again the bond valence to the initial value (charge ordering) under magnetic ordering conditions is possible only due to polar displacement of Mn2 (or O1) and O4 ions along the b axis that is the cause of ferroelectric transition.Comment: 17 pages, 3 figures, 5 table

Hepatocyte Growth Factor Receptor c-Met Instructs T Cell Cardiotropism and Promotes T Cell Migration to the Heart via Autocrine Chemokine Release

© 2015 The Authors. Published by Elsevier Inc. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/)This study was funded by the British Heart Foundation (RG/09/002/2642 to F.M.M.-B.) and the Medical Research Council of the UK (G0901084 to F.M.M.-B.). ImageStream X was funded by the Wellcome Trust (101604/Z/13/Z). This work forms part of the research themes contributing to the translational research portfolio of Barts and the London Cardiovascular Biomedical Research Unit, which is supported and funded by the National Institute of Health Research

Two-dimensional gapless spin liquids in frustrated SU(N) quantum magnets

A class of the symmetrically frustrated SU(N) models is constructed for quantum magnets based on the generators of SU(N) group. The total Hamiltonian lacks SU(N) symmtry. A mean field theory in the quasi-particle representation is developed for spin liquid states. Numerical solutions in two dimension indicate that the ground states are gapless and the quasi-particles are Dirac particles. The mechanism may be helpful in exploring the spin liquid phases in the spin-1 bilinear-biquadratic model and the spin-orbital model in higher dimensions.Comment: 9 pages, 3 figures, to appear in New Journal of Physic

Hydrophobic residues at position 10 of α-conotoxin PnIA influence subtype selectivity between α7 and α3β2 neuronal nicotinic acetylcholine receptors

Neuronal nicotinic acetylcholine receptors (nAChRs) are a diverse class of ligand-gated ion channels involved in neurological conditions such as neuropathic pain and Alzheimer's disease. α-Conotoxin [A10L]PnIA is a potent and selective antagonist of the mammalian α7 nAChR with a key binding interaction at position 10. We now describe a molecular analysis of the receptor-ligand interactions that determine the role of position 10 in determining potency and selectivity for the α7 and α3β2 nAChR subtypes. Using electrophysiological and radioligand binding methods on a suite of [A10L]PnIA analogs we observed that hydrophobic residues in position 10 maintained potency at both subtypes whereas charged or polar residues abolished α7 binding. Molecular docking revealed dominant hydrophobic interactions with several α7 and α3β2 receptor residues via a hydrophobic funnel. Incorporation of norleucine (Nle) caused the largest (8-fold) increase in affinity for the α7 subtype (Ki = 44 nM) though selectivity reverted to α3β2 (IC50 = 0.7 nM). It appears that the placement of a single methyl group determines selectivity between α7 and α3β2 nAChRs via different molecular determinants

Modelling Li+ Ion Battery Electrode Properties

We formulated two detailed models for an electrolytic cell with particulate electrodes based on a lithium atom concentration dependent Butler-Volmer condition at the interface between electrode particles and the electrolyte. The first was based on a dilute-ion assumption for the electrolyte, while the second assumed that Li ions are present in excess. For the first, we used the method of multiple scales to homogenize this model over the microstructure, formed by the small lithium particles in the electrodes. For the second, we gave rigorous bounds for the effective electrochemical conductivity for a linearized case. We expect similar results and bounds for the "full nonlinear problem" because variational results are generally not adversely affected by a sinh term. Finally we used the asymptotic methods, based on parameters estimated from the literature, to attain a greatly simplified one-dimensional version of the original homogenized model. This simplified model accounts for the fact that diffusion of lithium atoms within individual electrode particles is relatively much faster than that of lithium ions across the whole cell so that lithium ion diffusion is what limits the performance of the battery. However, since most of the potential drop occurs across the Debye layers surrounding each electrode particle, lithium ion diffusion only significantly affects cell performance if there is more or less complete depletion of lithium ions in some region of the electrolyte which causes a break in the current flowing across the cell. This causes catastrophic failure. Providing such failure does not occur the potential drop across the cell is determined by the concentration of lithium atoms in the electrode particles. Within each electrode lithium atom concentration is, to leading order, a function of time only and not of position within the electrode. The depletion of electrode lithium atom concentration is directly proportional to the current being drawn off the cell. This leads one to expect that the potential of the cell gradually drops as current is drawn of it. We would like to emphasize that all the homogenization methods employed in this work give a systematic approach for investigating the effect that changes in the microstructure have on the behaviour of the battery. However, due to lack of time, we have not used this method to investigate particular particle geometries

Relational Particle Models. II. Use as toy models for quantum geometrodynamics

Relational particle models are employed as toy models for the study of the Problem of Time in quantum geometrodynamics. These models' analogue of the thin sandwich is resolved. It is argued that the relative configuration space and shape space of these models are close analogues from various perspectives of superspace and conformal superspace respectively. The geometry of these spaces and quantization thereupon is presented. A quantity that is frozen in the scale invariant relational particle model is demonstrated to be an internal time in a certain portion of the relational particle reformulation of Newtonian mechanics. The semiclassical approach for these models is studied as an emergent time resolution for these models, as are consistent records approaches.Comment: Replaced with published version. Minor changes only; 1 reference correcte

Macrodimers: ultralong range Rydberg molecules

We study long range interactions between two Rydberg atoms and predict the existence of ultralong range Rydberg dimers with equilibrium distances of many thousand Bohr radii. We calculate the dispersion coefficients $C_{5}$, $C_{6}$ and $C_{8}$ for two rubidium atoms in the same excited level $np$, and find that they scale like $n^{8}$, $n^{11}$ and $n^{15}$, respectively. We show that for certain molecular symmetries, these coefficients lead to long range potential wells that can support molecular bound levels. Such macrodimers would be very sensitive to their environment, and could probe weak interactions. We suggest experiments to detect these macrodimers.Comment: 4 pages, submitted to PR