Magnetocaloric effect and improved relative cooling power in (La0.7Sr0.3MnO3/SrRuO3) superlattices

Magnetic properties of a series of (La0.7Sr0.3MnO3/SrRuO3) superlattices, where the SrRuO3 layer thickness is varying, are examined. A room-temperature magnetocaloric effect is obtained owing to the finite size effect which reduces the TC of La0.7Sr0.3MnO3 layers. While the working temperature ranges are enlarged,, -DeltaSmax values remains similar to the values in polycrystalline La0.7Sr0.3MnO3. Consequently, the relative cooling powers are significantly improved, the microscopic mechanism of which is related to the effect of the interfaces at La0.7Sr0.3MnO3/SrRuO3 and higher nanostructural disorder. This study indicates that artificial oxide superlattices/multilayers might provide an alternative pathway in searching for efficient room-temperature magnetic refrigerators for (nano)microscale systems.Comment: 14^pages, 3 figures, Submitted to J. Phys. Cond. Ma

Kondo temperature of magnetic impurities at surfaces

Based on the experimental observation, that only the close vicinity of a magnetic impurity at metal surfaces determines its Kondo behaviour, we introduce a simple model which explains the Kondo temperatures observed for cobalt adatoms at the (111) and (100) surfaces of Cu, Ag, and Au. Excellent agreement between the model and scanning tunneling spectroscopy (STS) experiments is demonstrated. The Kondo temperature is shown to depend on the occupation of the d-level determined by the hybridization between adatom and substrate with a minimum around single occupancy.Comment: 4 pages, 2 figure

Structure and function of an RNase H domain at the heart of the spliceosome.

Precursor-messenger RNA (pre-mRNA) splicing encompasses two sequential transesterification reactions in distinct active sites of the spliceosome that are transiently established by the interplay of small nuclear (sn) RNAs and spliceosomal proteins. Protein Prp8 is an active site component but the molecular mechanisms, by which it might facilitate splicing catalysis, are unknown. We have determined crystal structures of corresponding portions of yeast and human Prp8 that interact with functional regions of the pre-mRNA, revealing a phylogenetically conserved RNase H fold, augmented by Prp8-specific elements. Comparisons to RNase H–substrate complexes suggested how an RNA encompassing a 5′-splice site (SS) could bind relative to Prp8 residues, which on mutation, suppress splice defects in pre-mRNAs and snRNAs. A truncated RNase H-like active centre lies next to a known contact region of the 5′SS and directed mutagenesis confirmed that this centre is a functional hotspot. These data suggest that Prp8 employs an RNase H domain to help assemble and stabilize the spliceosomal catalytic core, coordinate the activities of other splicing factors and possibly participate in chemical catalysis of splicing

Extraction efficiency of drifting electrons in a two-phase xenon time projection chamber

We present a measurement of the extraction efficiency of quasi-free electrons from the liquid into the gas phase in a two-phase xenon time-projection chamber. The measurements span a range of electric fields from 2.4 to 7.1 kV/cm in the liquid xenon, corresponding to 4.5 to 13.1 kV/cm in the gaseous xenon. Extraction efficiency continues to increase at the highest extraction fields, implying that additional charge signal may be attained in two-phase xenon detectors through careful high-voltage engineering of the gate-anode region