Tetra­aqua­bis[3-(4-pyrid­yl)benzoato-κN]nickel(II)

The NiII atom in the title compound, [Ni(C12H8NO2)2(H2O)4], exists in an all-trans octa­hedral coordination environment. The 3-(4-pyrid­yl)benzoate ligand binds to Ni atom through the pyridyl N atom; the pyridine and benzene rings are oriented at a dihedral angle of 26.27 (10)°. Adjacent complexes are linked by O—H⋯O hydrogen bonds, forming a three-dimensional network. The metal atom lies on a special position of 2 site symmetry in the crystal structure

Gamma rays and neutrinos from dark matter annihilation in galaxy clusters

The $\gamma$-ray and neutrino emissions from dark matter (DM) annihilation in galaxy clusters are studied. After about one year operation of Fermi-LAT, several nearby clusters are reported with stringent upper limits of GeV $\gamma$-ray emission. We use the Fermi-LAT upper limits of these clusters to constrain the DM model parameters. We find that the DM model distributed with substructures predicted in cold DM (CDM) scenario is strongly constrained by Fermi-LAT $\gamma$-ray data. Especially for the leptonic annihilation scenario which may account for the $e^{\pm}$ excesses discovered by PAMELA/Fermi-LAT/HESS, the constraint on the minimum mass of substructures is of the level $10^2-10^3$ M$_{\odot}$, which is much larger than that expected in CDM picture, but is consistent with a warm DM scenario. We further investigate the sensitivity of neutrino detections of the clusters by IceCube. It is found that neutrino detection is much more difficult than $\gamma$-rays. Only for very heavy DM ($\sim 10$ TeV) together with a considerable branching ratio to line neutrinos the neutrino sensitivity is comparable with that of $\gamma$-rays.Comment: 21 pages, 8 figures and 1 table; extended discussion about the uncertainties of concentration and subhalo models, figures replotted for better read; references updated; accepted for publication by Phys. Rev.

Neuroprotective Effect of a Formula, Moschus Combined with Borneolum Synthcticum, from Traditional Chinese Medicine on Ischemia Stroke in Rats

Moschus compatible with borneolum synthcticum is a well-known herb pair in Traditional Chinese Medicine and the present study aims to assess the neuroprotective effect of a formula composed of this herb pair on ischemia stroke in rats. The middle cerebral artery occlusion model of focal cerebral ischemia in rat was performed by using intraluminal suture method. The behavioral scores, infarct volume, and neuron ultrastructure of model and formula-treated rats were investigated after the 2 h of ischemia and 24 h of reperfusion. Meanwhile the expression levels of caspase-3, caspase-9, Bcl-2, and Bax were measured by western blot analysis. The formula treatment showed obvious neuroprotective effect according to significant decrease of the neurological scores (P<0.01) and the infarct volumes (P<0.05) when compared to the MCAO group. We also observed that this formula had antiapoptosis activity on neuron cell under electron microscope. Furthermore, our result supported the idea that pro- and postadministration of this formula had an antiapoptosis effect by decreasing remarkably the expression of caspase-3 and caspase-9 (P<0.05) as well as increasing significantly the ratio of Bcl-2 to Bax (P<0.01). All evidences demonstrated the neuroprotective effect of this formula on ischemia stroke due to decrease of brain infract volume and modulation of the expression of apoptosis-related proteins

2-Meth­oxy-6-[(Z)-[(5-methyl-2-pyrid­yl)imino­meth­yl]phenol

The title compound, C14H14N2O2, was obtained by a condensation reaction between o-vanillin and 5-methyl­pyridin-2-amine. In the mol­ecule, the dihedral angle between the pyridine and benzene rings is 9.08 (13)°. An intra­molecular hydrogen bond involving the imine N atom and the hydroxyl group may influence the conformation of the mol­ecule. The crystal structure is stabilized by weak C—H⋯O hydrogen bonds

Field Driven Pairing State Phase Transition in d_x^2-y^2+id_xy-Wave Superconductors

Within the framework of the Ginzburg-Landau theory for $d_{x^2-y^2}+id_{xy}$-wave superconductors, we discuss the pairing state phase transition in the absence of the Zeeman coupling between the Cooper pair orbital angular momentum and the magnetic field. We find that above a temperature $T_{\ast}$, the pairing state in a magnetic field is pure $d_{x^{2}-y^{2}}$-wave. However, below $T_{\ast}$, the pairing state is $d_{x^{2}-y^{2}}+id_{xy}$-wave at low fields, and it becomes pure $d_{x^{2}-y^{2}}$-wave at higher fields. Between these pairing states there exists a field driven phase transition . The transition field increases with decreasing temperature. In the field-temperature phase diagram, the phase transition line is obtained theoretically by a combined use of a variational method and the Virial theorem. The analytical result is found to be in good agreement with numerical simulation results of the Gingzburg-Landau equations. The validity of the variational method is discussed. The difference to the case with the Zeeman coupling is discussed, which may be utilized to the detection of the Zeeman coupling.Comment: 5 pages, 2 figures, submitted to PRB Brief Repor

Bound states in d-density-wave phases

We investigate the quasiparticle spectrum near surfaces in a two-dimensional system with d-density-wave order within a mean-field theory. For Fermi surfaces with perfect nesting for the ordering wave vector of the d-density-wave, a zero energy bound state occurs at [110] surfaces, in close analogy with the known effect in d-wave superconducting states or graphite. When the shape of the Fermi surface is changed by doping, the bound state energy moves away from the Fermi level. Furthermore, away from half-filling we find inhomogeneous phases with domain walls of the d-density-wave order parameter. The domain walls also support low energy bound states. These phenomena might provide an experimental test for hidden d-density-wave order in the high-Tc cuprates.Comment: 6 pages, 5 figure