Universal temperature scaling of flux line pinning in high-temperature superconducting thin films

Dissipation-free current transport in high-temperature superconductors is one of the most crucial properties of this class of materials which is directly related to the effective inhibition of flux line movement by defect structures. In this respect epitaxially grown thin films of YBa2Cu3O7-d (YBCO) are proving to be the strongest candidates for many widescale applications that are close to realization. We show that the relation between different defect structures and flux line pinning in these films exhibits universal features which are clearly displayed in a detailed analysis of the temperature-dependent behaviour of local critical currents. This allows us to identify different pinning mechanisms at different temperatures to be responsible for the found critical currents. Additionally, the presence of grain boundaries with very low misorientation angles affects the temperature stability of the critical currents which has important consequences for future applications.Comment: 5 pages, 4 figures To be published in Journal of Physics: Condensed matte

Electronic tuneability of a structurally rigid surface intermetallic and Kondo lattice: CePt5_5 / Pt(111)

We present an extensive study of structure, composition, electronic and magnetic properties of Ce--Pt surface intermetallic phases on Pt(111) as a function of their thickness. The sequence of structural phases appearing in low energy electron diffraction (LEED) may invariably be attributed to a single underlying intermetallic atomic lattice. Findings from both microscopic and spectroscopic methods, respectively, prove compatible with CePt$_5$ formation when their characteristic probing depth is adequately taken into account. The intermetallic film thickness serves as an effective tuning parameter which brings about characteristic variations of the Cerium valence and related properties. Soft x-ray absorption (XAS) and magnetic circular dichroism (XMCD) prove well suited to trace the changing Ce valence and to assess relevant aspects of Kondo physics in the CePt$_5$ surface intermetallic. We find characteristic Kondo scales of the order of 10$^2$ K and evidence for considerable magnetic Kondo screening of the local Ce $4f$ moments. CePt$_5$/Pt(111) and related systems therefore appear to be promising candidates for further studies of low-dimensional Kondo lattices at surfaces.Comment: 14 pages, 11 figure

Expanding the Portfolio by a Novel Monomeric Oleate Hydratase from Pediococcus parvulus

Oleate hydratases convert oleic acid into 10-hydroxy stearic acid, a valuable fine chemical, useful in lubricant and surfactant formulations. They are of large interest due to their high expression rates and solubility, however, they differ drastically by their overall stability and pH- and temperature ranges. To expand their portfolio, another oleate hydratase named OhyPp (originating from Pediococcus parvulus) was characterized. It is a close relative of the well-known oleate hydratase OhyRe from Rhodococcus erythropolis. OhyPp is only the second member of the monomeric oleate hydratase family with some surprising catalytic features. A distinct characteristic is OhyPp's higher affinity towards FAD compared to OhyRe's helping to understand and improve FAD binding in the future, which is a current drawback for the industrial application of oleate hydratases

Molecular dynamics study of taxadiene synthase catalysis

Molecular dynamics (MD) simulations have been performed to study the dynamic behavior of noncovalent enzyme carbocation complexes involved in the cyclization of geranylgeranyl diphosphate to taxadiene catalyzed by taxadiene synthase (TXS). Taxadiene and the observed four side products originate from the deprotonation of carbocation intermediates. The MD simulations of the TXS carbocation complexes provide insights into potential deprotonation mechanisms of such carbocations. The MD results do not support a previous hypothesis that carbocation tumbling is a key factor in the deprotonation of the carbocations by pyrophosphate. Instead water bridges are identified which may allow the formation of side products via multiple proton transfer reactions. A novel reaction path for taxadiene formation is proposed on the basis of the simulations

Strain and composition dependence of the orbital polarization in nickelate superlattices

A combined analysis of x-ray absorption and resonant reflectivity data was used to obtain the orbital polarization profiles of superlattices composed of four-unit-cell-thick layers of metallic LaNiO3 and layers of insulating RXO3 (R=La, Gd, Dy and X=Al, Ga, Sc), grown on substrates that impose either compressive or tensile strain. This superlattice geometry allowed us to partly separate the influence of epitaxial strain from interfacial effects controlled by the chemical composition of the insulating blocking layers. Our quantitative analysis reveal orbital polarizations up to 25%. We further show that strain is the most effective control parameter, whereas the influence of the chemical composition of the blocking layers is comparatively small.Comment: 9 pages, 8 figure

Sensory quality of turnip greens and turnip tops grown in northwestern Spain

In Galicia (northwestern Spain), Brassica rapa var. rapa L. includes turnip greens and turnip tops as vegetable products. They are characterized by a particular sulfurous aroma, pungent flavor, and a bitter taste. In this work twelve local varieties grown as turnip greens and turnip tops were evaluated to define the sensory attributes, to relate them with secondary metabolites, and to select those sensorial traits that better describe these crops. Results showed differences in the sensory profiles of B. rapa varieties. Turnip greens were significantly differed for aroma intensity, leaf color, and salty taste, while turnip tops were for color and firmness of leaves, moistness and fibrosity in mouth, sharpness, and bitter taste. Secondary metabolites as glucosinolates in turnip greens and phenolic compounds in turnip tops were highly correlated with texture and flavor. Glucosinolates especially progoitrin (in turnip greens) and gluconapin (in turnip tops) showed correlation with bitter taste and aftertaste persistence. Correlation between sensory traits showed highest values between leaf firmness and stalk firmness (0.94**), leaf firmness and fibrosity (R=0.92**), aftertaste persistence and bitterness (R=0.91**) and between bitterness and moistness (R=-0.89**).Research supported by the Xunta de Galicia (PGIDIT06RAG40302PR) and Excma. Diputación Provincial de Pontevedra.Peer reviewe