Observation of sharp resistance anomalies near Tc in granular superconductors

Granular films prepared from well-defined In clusters embedded in Kr (? 10-40 at % Kr) show sharp resistance anomalies very close to the superconducting transition temperature. The observed resistance peak(s), which go(es) above the normal state resistance R_N and which can be as high as ? 1.5 R_N, can be explained by a “mesoscopic” effect: Superconducting percolation aggregates of size ξ_ρ, larger than the superconducting coherence length ξ_S, but smaller than the quasiparticle relaxation length λ_Q*, have a superconducting gap, but are not yet able to carry a supercurrent.     

Regions of stability of high-power gyrotron oscillators

The problem of mode competition in a high-power gyrotron oscillator is considered. The regions of parameter space in which a preexisting large-amplitude mode is able to suppress competing satellites are determined for cases in which the coupling coefficients and cavity quality factors for the operating and satellite modes are different. In addition, the effect of beam quality on the regimes of stable single-mode operation is investigated. Generally speaking, the requirement of stable operation favors devices whose interaction length measured by the parameter μ is not too large. It is found that for μ near 10 the operation is relatively stable and μ near 17 is not     

The use of sulfide cluster-derived catalysts to understand the promotional effect in hydrotreatment catalysis

Sulfide cluster-derived ensembles are promising models of the active sites in commercial hydrotreatment catalysts. A series of sulfide clusters were adsorbed intact onto high-surface-area γ-alumina, magnesium oxide and activated carbon supports, then pretreated to produce highly dispersed catalytic ensembles with sizes similar to those of their precursor clusters. The activities of the bimetallic cluster-derived catalysts were significantly higher than those of the monometallic catalysts. We took this as evidence that direct interactions between molybdenum and the promoter element cause the promotional effect observed in commercial hydrotreatment catalysts. The hydrodesulfurization and hydrodenitrogenation activities correlated with the extent of molybdenum reduction. Our results suggested that the active sites in promoted hydrotreatment catalysts are centered on molecular-scale ensembles containing molybdenum, sulfur and the promoter element.     

Purification and characterization of gamma-enolase from various mammals.

The gamma subunit of enolase (gamma-enolase) was purified from the brain tissues of cow, dog, goat, pig, rabbit, and rat. The purification was achieved in only three steps: ammonium sulfate-precipitation, DE 53 cellulose ion-exchange chromatography, and polyacrylamide gel electrophoresis (PAGE) in a preparative mode. The purification procedure was comparatively more simple than previously reported methods, and the yield of gamma-enolase was sufficient for subsequent structural and immunological analyses. In all mammals, the purified gamma-enolase migrated in sodium dodecyl sulfate-PAGE (SDS-PAGE) with a molecular mass of 46 kilodaltons (kDa), and the immunological cross-reactivity between those gamma-enolases was very strong. The structural homology of these gamma-enolases was examined by peptide mapping using cyanogen bromide cleavage and subsequent two-dimensional electrophoresis. The resulting peptide patterns were highly similar and in cow, dog, and goat, the patterns were almost identical. These results indicate that structural homology, that is, the species non-specificity of gamma-enolase, appears to be very high.     

Creation of multiquantum coherences from equilibrium spin systems

Recently it has been suggested that zero quantum coherence in scalar coupled spin systems at thermal equilibrium can be created by a single non-selective pulse. In this note, it is shown that the proposed effect will be masked as a consequence of the failure of the conventional high-temperature approximation normally applied to the equilibrium spin density operator. For exacting experiments, its appears that the approximation (eq) ≈ 1-H /kT may not suffice.     

Morphological and elemental characterisation with the high-energy ion-nanoprobe LIPSION

This contribution deals with the morphological and elemental characterisation with high-energy (MeV) focused ion beams (in particular protons) with special emphasis on high spatial resolution in the sub-micrometer regime and very low minimum detection limits (sub-ppm) in trace element analysis. The most important methods like particle induced X-ray emission (PIXE), Rutherford backscattering spectrometry (RBS), as well as scanning transmission ion microscopy (STIM) and STIM-tomography will be illustrated by examples from material and life sciences.     

Study of pairing deformations by means of two-particle transfer reactions

The macroscopic approach for two-particle transfer reactions is applied in normal spherical nuclei and pairing deformation parameters β_p are estimated. For Ni isotopes the macroscopic approach works reasonably well while for the lead region strong energy dependence of theβ _p values has been observed. It is shown that alpha-transfer reactions can also be treated within this formalism as couplings of the two-neutron and two-proton channels.