Study of Ni and Zn doped CeOFeAs: Effect on the structural transition and specific heat capacity

We have systematically studied the substitution of nonmagnetic Zn and magnetic Ni at iron sites in Ce based oxypnictide. The parent compound (CeOFeAs) shows an anomaly in resistivity around 150 K due to structural transition from tetragonal (space group: P4/nmm) to orthorhombic structure (space group: Cmma). Substitution of Zn suppresses this anomaly to lower temperature (~130 K) but Ni substitution does not show any anomaly around this temperature and the compound behaves like a metal. Further, we find that non magnetic (Zn) doping leads to higher impurity scattering as compared to magnetic Ni doping. Similar to the resistivity measurement, the specific heat shows another jump near 4 K for CeOFeAs. This is attributed to the ordering of Ce3+ moments. This peak shifts to 3.8 K for Zn substituted compound and there is no change in the ordering temperature in the Ni substituted CeOFeAs. These peaks are broadened in applied magnetic field (5 T) and the calculated magnetic entropy tends to saturate at the same value for 0 T and 5 T external magnetic field.Comment: 16 pages Text+Fig

Ivermectin in the treatment of Bancroftian filariasis infection in Orissa, India

Ivermectin treatment has evaluated for its efficacy and side reactions in sixty patients of Orissa with Bancroftian filarial infection and microfilaremia. Ivermectin was administered as a single oral dose at four dosage levels (20, 50. 100 and 200 μg/kg), and both microfilarial clearance and associated side reactions were monitored in a double blind fashion. Blood microfilariae were cleared in all patients at all dosages within 1 to 14 days. In most patients microfilariae reappeared by third month. The microfilaria appearance by third and sixth month averaged 12.2 to 44 percent of pretreatment values in the fourstudy groups. Side reactions were encountered in almost all patients, the commonest being fever. headache, weakness, myalgia and cough which occured most prominently 12 to 72 hours after treatment. Side reactions were more frequent and severe in patients with high microfilaria counts. Clinical reaction scores for each group were independent of the dose administered. The 200 μg dose group showed significantly more rapid microfilariae clearance and its delayed reappearance as compared with the other dosage groups and without inducing significantly greater clinical reaction scores

Upper critical field, superconducting energy gaps, and Seebeck coefficient in La0.8Th0.2OFeAs

We report the synthesis and characterization of a new electron-doped La-oxypnictide superconductor by partial substitution of lanthanum by thorium. The superconducting transition temperature at about 30.3 K was observed in La0.8Th0.2OFeAs which is the highest in La-based oxypnictide superconductors synthesized at ambient pressure. We find that the decrease in lattice parameters with Th doping in LaOFeAs is more drastic as compared to that obtained by high pressure (6 GPa) synthesis of oxygen deficient LaOFeAs. The resistivity and magnetic susceptibility measurements yield an upper critical field Hc2 (0) of 47 T. Partial substitution of Th in place of La induces electron doping as evidenced by negative Seebeck coefficient. The temperature dependent magnetic penetration depth data provides strong evidence for a nodeless low energy gap of 1.4 meV

The 3-53 keV Spectrum of the Quasar 1508+5714: X-rays from z = 4.3

We present a high-quality X-ray spectrum in the 3--53 keV rest-frame band of the radio-loud quasar 1508+5714, by far the brightest known X-ray source at z > 4. A simple power-law model with an absorption column density equal to the Galactic value in the direction of the source provides an excellent and fully adequate fit to the data; the measured power-law photon index Gamma = 1.42 (+0.13,-0.10). Upper limits to Fe K alpha line emission and Compton-reflection components are derived. We offer evidence for both X-ray and radio variability in this object and provide the first contemporaneous radio spectrum (alpha = -0.25). The data are all consistent with a picture in which the emission from this source is dominated by a relativistically beamed component in both the X-ray and radio bands.Comment: 8 pages, TeX, 2 postscript figures; to appear in ApJ Letter