A Transport and Microwave Study of Superconducting and Magnetic RuSr2EuCu2O8

We have performed susceptibility, thermopower, dc resistance and microwave measurements on RuSr2EuCu2O8. This compound has recently been shown to display the coexistence of both superconducting and magnetic order. We find clear evidence of changes in the dc and microwave resistance near the magnetic ordering temperature (132 K). The intergranular effects were separated from the intragranular effects by performing microwave measurements on a sintered ceramic sample as well as on a powder sample dispersed in an epoxy resin. We show that the data can be interpreted in terms of the normal-state resistivity being dominated by the CuO2 layers with exchange coupling to the Ru moments in the RuO2 layers. Furthermore, most of the normal-state semiconductor-like upturn in the microwave resistance is found to arise from intergranular transport. The data in the superconducting state can be consistently interpreted in terms of intergranular weak-links and an intragranular spontaneous vortex phase due to the ferromagnetic component of the magnetization arising from the RuO2 planes.Comment: 20 pages including 6 figures in pdf format. To be published in Phys. Rev.

Magneto-superconductivity of 100-atm O2-annealed RuSr2Gd1.5Ce0.5Cu2O10

Studied 100-atm O2-annealed RuSr2Gd1.5Ce0.5Cu2O10 (Ru-1222) compound crystallized in a tetragonal I4/mmm space group crystal structure. Thermo-gravemetric (TG) analysis of the compound showed the release of oxygen and breaking to metallic constituents in two distinct steps at around 350 and 500 0C. The DC magnetization data (M vs. T) revealed magnetic transition at 100 K followed by superconducting transition at 40 K. Low field M vs. H hysteresis loop showed a lower critical field (Hc1) value of around 25 Oe. Ferromagnetic component is evidenced at 5, 10, 20 and 40 K. Near saturation field of above 5 Tesla is observed at 5 K. Zero-field returning moment (Mr) and zero-moment coercive field (Hc) values at 5 K are 0.35mB and 250 Oe. The resistance vs. temperature (R vs. T) behaviour of the sample confirmed superconductivity at around 43 K. Superconductivity transition (Tc) is broadened under magnetic field with strong granularity like steps.Comment: 16 pages including text and six figure

Decoupling of superconducting layers in magnetic superconductor RuSr_{2}GdCu_{2}O_{8}

We propose the model for magnetic properties of the magnetic superconductor RuSr$_{2}$GdCu$_{2}$O$_{8}$, which incorporates the theory of the superconducting/ferromagnetic multilayers. The transition line $T_{d}(h)$, on which the Josephson coupled superconducting planes are decoupled, i.e. $j_{c}(T_{d})=0$, is calculated as a function of the exchange energy $h$. As the result of this decoupling a nonmonotonic behavior of magnetic properties, like the lower critical field $H_{c1}$, Josephson plasma frequency, etc. is realized near (or by crossing) the $T_{d}(h)$ line. The obtained results are used in analyzing the newly discovered antiferromagnetic ruthenocuprate RuSr$_{2}$GdCu$_{2}$O$_{8}$ with possible weak ferromagnetic order in the RuO planes.Comment: 12 pages, 3 figs embede

Decoupled CuO_2 and RuO_2 layers in superconducting and magnetically ordered RuSr_2GdCu_2O_8

Comprehensive measurements of dc and ac susceptibility, dc resistance, magnetoresistance, Hall resistivity, and microwave absorption and dispersion in fields up to 8 T have been carried out on RuSr_2GdCu_2O_8 with the aim to establish the properties of RuO_2 and CuO_2 planes. At ~130 K, where the magnetic order develops in the RuO_2 planes, one observes a change in the slope of dc resistance, change in the sign of magnetoresistance, and the appearance of an extraordinary Hall effect. These features indicate that the RuO_2 planes are conducting. A detailed analysis of the ac susceptibility and microwave data on both, ceramic and powder samples show that the penetration depth remains frequency dependent and larger than the London penetration depth even at low temperatures. We conclude that the conductivity in the RuO_2 planes remains normal even when superconducting order is developed in the CuO_2 planes below \~45 K. Thus, experimental evidence is provided in support of theoretical models which base the coexistence of superconductivity and magnetic order on decoupled CuO_2 and RuO_2 planes.Comment: 11 pages, 11 figures, submitted to PR

Anomalous lattice expansion of RuSr2Eu1.5Ce0.5Cu2O10(Ru-1222) magneto superconductor: A low temperature X-ray diffraction study

This is the first report of the observation of the onset of excess volume and also of the strain along the a-axis near the magnetic ordering temperature in Ru-1222 superconductor, and indicates a coupling between the lattice and the magnetism in this system. Magnetization, magneto transport and thermoelectric power measurements being carried out on the same sample are also reported.Comment: 15 Pages Text Plus Figs. Physica C (2006) accepte

Evolutionary divergence of gene and protein expression in the brains of humans and chimpanzees

Although transcriptomic profiling has become the standard approach for exploring molecular differences in the primate brain, very little is known about how the expression levels of gene transcripts relate to downstream protein abundance. Moreover, it is unknown whether the relationship changes depending on the brain region or species under investigation. We performed high-throughput transcriptomic (RNA-Seq) and proteomic (liquid chromatography coupled with tandem mass spectrometry) analyses on two regions of the human and chimpanzee brain: The anterior cingulate cortex and caudate nucleus. In both brain regions, we found a lower correlation between mRNA and protein expression levels in humans and chimpanzees than has been reported for other tissues and cell types, suggesting that the brain may engage extensive tissue-specific regulation affecting protein abundance. In both species, only a few categories of biological function exhibited strong correlations between mRNA and protein expression levels. These categories included oxidative metabolism and protein synthesis and modification, indicating that the expression levels of mRNA transcripts supporting these biological functions are more predictive of protein expression compared with other functional categories. More generally, however, the two measures of molecular expression provided strikingly divergent perspectives into differential expression between human and chimpanzee brains: mRNA comparisons revealed significant differences in neuronal communication, ion transport, and regulatory processes, whereas protein comparisons indicated differences in perception and cognition, metabolic processes, and organization of the cytoskeleton. Our results highlight the importance of examining protein expression in evolutionary analyses and call for a more thorough understanding of tissue-specific protein expression levels

High Rate of Mobilization for blaCTX-Ms

The blaCTX-Ms have been mobilized to plasmids more frequently than other class A β-lactamases

Elevation and cholera: an epidemiological spatial analysis of the cholera epidemic in Harare, Zimbabwe, 2008-2009

BACKGROUND: In highly populated African urban areas where access to clean water is a challenge, water source contamination is one of the most cited risk factors in a cholera epidemic. During the rainy season, where there is either no sewage disposal or working sewer system, runoff of rains follows the slopes and gets into the lower parts of towns where shallow wells could easily become contaminated by excretes. In cholera endemic areas, spatial information about topographical elevation could help to guide preventive interventions. This study aims to analyze the association between topographic elevation and the distribution of cholera cases in Harare during the cholera epidemic in 2008 and 2009. METHODS: We developed an ecological study using secondary data. First, we described attack rates by suburb and then calculated rate ratios using whole Harare as reference. We illustrated the average elevation and cholera cases by suburbs using geographical information. Finally, we estimated a generalized linear mixed model (under the assumption of a Poisson distribution) with an Empirical Bayesian approach to model the relation between the risk of cholera and the elevation in meters in Harare. We used a random intercept to allow for spatial correlation of neighboring suburbs. RESULTS: This study identifies a spatial pattern of the distribution of cholera cases in the Harare epidemic, characterized by a lower cholera risk in the highest elevation suburbs of Harare. The generalized linear mixed model showed that for each 100 meters of increase in the topographical elevation, the cholera risk was 30% lower with a rate ratio of 0.70 (95% confidence interval=0.66-0.76). Sensitivity analysis confirmed the risk reduction with an overall estimate of the rate ratio between 20% and 40%. CONCLUSION: This study highlights the importance of considering topographical elevation as a geographical and environmental risk factor in order to plan cholera preventive activities linked with water and sanitation in endemic areas. Furthermore, elevation information, among other risk factors, could help to spatially orientate cholera control interventions during an epidemic

Magneto-Transport Properties of Doped RuSr2_2GdCu2_2O8_8

RuSr$_2$GdCu$_2$O$_8$, in which magnetic order and superconductivity coexist with $T_{Magnetic}$$\gg$$T_c$, is a complex material which poses new and important questions to our understanding of the interplay between magnetic and superconducting (SC) order. Resistivity, Hall effect and thermopower measurements on sintered ceramic RuSr$_2$GdCu$_2$O$_8$ are presented, together with results on a broad range of substituted analogues. The Hall effect and thermopower both show anomalous decreases below $T_{Magnetic}$ which may be explained within a simple two-band model by a transition from localized to more itinerant behavior in the RuO$_2$ layer at $T_{Magnetic}$.Comment: 10 pages, 7 figures, submitted to Phys. Rev. B., correspondence to [email protected]