The energetics of mercury adsorption on Cu(100)

We have investigated the adsorption of mercury overlayers on Cu(100) by atom beam scattering, low energy electron diffraction and angle resolved photoemission. From our data we have calculated the isosteric heats in the adsorbed Hg layer on Cu(100) and compared these with results obtained for mercury on Fe(100), W(100) and Ni(100). We observe changes in the isosteric heat of adsorption that can be associated with the ordering of a c(2 × 2) Hg overlayer phase and the transition from a c(2 × 2) overlayer to a c(4 × 4) overlayer. The isosteric heat of adsorption is 0.50 ± 0.07 eV/atom (48 ± 7 kJ/mol) at zero coverage and reaches a maximum of 0.73 ± 0.04 eV/atom (70 ± 4 kJ/mol). From a combination of ABS and LEED, the structures of the two equilibrium ordered phases of Hg on Cu(100) have been identified, as well as the structures of several non-equilibrium phases.     

Verschiedene Lebensmittel-Untersuchungsmethoden

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Properties of a two-beam laser diode and focusing characteristics of a two-beam optical head

Dynamic wavelength shifts of a monolithic, two-beam laser diode for a two-beam optical head in optical disk drives were analyzed with a streak camera system. The wavelength shift did not exceed 3 nm for the recording beam which was operated in a series of pulses, and the reproducing beam which was operated continuously showed no shift. The focusing characteristics on the basis of the wavelength shift and specifications of the optical head were also calculated. The dynamic displacement of the focal points caused by the wavelength shifts was so small as compared with the depth of focus in the optical head that the recording and reproducing characteristics were hardly influenced.     

Cell-penetrant, nanomolar O-GlcNAcase inhibitors selective against lysosomal hexosaminidases

Posttranslational modification of metazoan nucleocytoplasmic proteins with N-acetylglucosamine (O-GlcNAc) is essential, dynamic, and inducible and can compete with protein phosphorylation in signal transduction. Inhibitors of O-GlcNAcase, the enzyme removing O-GlcNAc, are useful tools for studying the role of O-GlcNAc in a range of cellular processes. We report the discovery of nanomolar OGA inhibitors that are up to 900,000-fold selective over the related lysosomal hexosaminidases. When applied at nanomolar concentrations on live cells, these cell-penetrant molecules shift the O-GlcNAc equilibrium toward hyper-O-GlcNAcylation with EC?? values down to 3 nM and are thus invaluable tools for the study of O-GlcNAc cell biology.     

Loading a dipole trap from an atomic reservoir

Loading a dipole trap from an atomic reservoir is considered to be an efficient method for the preparation of trapped atoms at high density, which has led to notable results for the case of Rb and Cr atoms. It was also theoretically predicted to provide efficient loading also in the cesium case. In this article, we report on the experimental study of the loading of a single-arm and of a crossed dipole trap for cesium atoms. This study is performed by comparing several types of reservoirs from which the atoms are loaded: a magnetic trap, a Dark-SPOT and a compressed MOT. In all cases the number of atoms is found to decrease shortly after the beginning of the loading process. A few possible phenomena leading to such a behavior, namely the limited reservoir lifetime and/or a possible heating in the reservoir, are discussed. The loading dynamics is fitted by a phenomenological rate equation. From an experimental point of view, the reservoir loading method can be considered efficient in terms of number of transferred atoms for the single arm dipole trap. On the contrary, it does not seem to provide, for the case of cesium atoms in a crossed dipole trap, an attractive alternative in comparison with existing loading methods such as Raman sideband cooling.     

Farbstoffe

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The correlation between strain and electronic structure in monolayer thick films

We explote and empirical relationship between strain (and lattice constant) and the valence electronic structure for mercury, bromine and iron overlayers. These overlayers have a range of lattice constants. For the Hg overlayers, all share a common cubic crystallography. We generally observe that the smaller the overlayer lattice constant, the greater the energy separation betweend-bands (Hg and Fe) orp-bands (Br). These results have important implications in relating electronic structure to fundamental properties such as magnetism. In addition, the film thickness limits for pseudomorphic growth calculated from the bulk properties are consistent with the experimental studies of Hg pseudomorphic growth on Ag (100) at 90 K.