Nickel Deposition on ?-Al2O3: Modelling Metal Particle Behaviour at the Support

Recently, surface modifications on a commercial Ni/Al2O3 catalyst during the production of methane from synthesis gas were investigated by quasi in situ X-ray photoelectron spectroscopy (XPS). The effect of the synthesis gas on the surface properties of the catalyst and on its activity under methanation conditions was studied on an atomic level. The conclusion was that the stability of Ni particles on the ?-Al2O3 support can be influencedby cluster growth phenomena, which influence both size and distribution of the metal particles. In this study, Ni deposition and cluster growth on model catalyst samples (10 nm thick, polycrystalline ?-Al2O3 on Si(100)) was investigated by XPS. The molecular structure of the catalyst was investigated using Density Functional Theory calculations (StoBe) with cluster model and non-local functional (RPBE) approach. Al15O40H35 clusterswere selected to represent the ?-Al2O3 (100) surface. Ni clusters of different size were cut from a Ni(100) surface and deposited on the Al15O40H35 cluster in order to validate the deposition model determined by XPS

Modelling Catalyst Surfaces Using DFT Cluster Calculations

We review our recent theoretical DFT cluster studies of a variety of industrially relevant catalysts such as TiO2, γ-Al2O3, V2O5-WO3-TiO2 and Ni/Al2O3. Aspects of the metal oxide surface structure and the stability and structure of metal clusters on the support are discussed as well as the reactivity of surfaces, including their behaviour upon poisoning. It is exemplarily demonstrated how such theoretical considerations can be combined with DRIFT and XPS results from experimental studies

Recent astrophysical and accelerator based results on the Hadronic Equation of State

In astrophysics as well as in hadron physics progress has recently been made on the determination of the hadronic equation of state (EOS) of compressed matter. The results are contradictory, however. Simulations of heavy ion reactions are now sufficiently robust to predict the stiffness of the (EOS) from (i) the energy dependence of the ratio of $K^+$ from Au+Au and C+C collisions and (ii) the centrality dependence of the $K^+$ multiplicities. The data are best described with a compressibility coefficient at normal nuclear matter density $\kappa$ around 200 MeV, a value which is usually called ``soft'' The recent observation of a neutron star with a mass of twice the solar mass is only compatible with theoretical predictions if the EOS is stiff. We review the present situation.Comment: invited talk Strange Quark Matter Conference SQM06 in Los Angele

Additional file 1: of A cross-sectional study assessing the association between online ratings and structural and quality of care measures: results from two German physician rating websites

“The association between online ratings and structural and quality_Bivariate analysis”, PDF format. (PDF 534 kb

Short-time scale coupling between thermohaline and meteorological forcing in the Ría de Pontevedra

12 páginas, 2 tablas, 6 figurasTwo cruises were performed in May-June and October-November 1997 in the Ría de Pontevedra under strong downwelling conditions. Temperature and salinity data were recorded in short sampling periods to describe the changes in thermohaline property distribution in a short time scale. In order to obtain the residual fluxes in the Ría, a bi-dimensional non-stationary salt and thermal-energy weight averaged box-model was applied. Outputs from this kinematic model were compared with Upwelling Index, river flow and density gradient, resulting in a good multiple correlation, which proves the strong coupling between thermohaline properties and meteorological variability. Ekman forcing affects the whole area but mainly controls the dynamics of outer zones. The intensity of its effect on the circulation pattern within the Ría depends on the grade of stratification of the water bodies. River flow is more relevant in inner parts. According to estimated spatially averaged velocities, water residence time is lower than two weeks in outer parts of the Ría, and decreases toward the inner zones.Support for this work came from CICYT project AMB95-1084.Peer reviewe

Assessing noise sources at synchrotron infrared ports

Today, the vast majority of electron storage rings delivering synchrotron radiation for general user operation offer a dedicated infrared port. There is growing interest expressed by various scientific communities to exploit the mid-IR emission in microspectroscopy, as well as the far infrared (also called THz) range for spectroscopy. Compared with a thermal (laboratory-based source), IR synchrotron radiation sources offer enhanced brilliance of about two to three orders of magnitude in the mid-IR energy range, and enhanced flux and brilliance in the far-IR energy range. Synchrotron radiation also has a unique combination of a broad wavelength band together with a well defined time structure. Thermal sources (globar, mercury filament) have excellent stability. Because the sampling rate of a typical IR Fourier-transform spectroscopy experiment is in the kHz range (depending on the bandwidth of the detector), instabilities of various origins present in synchrotron radiation sources play a crucial role. Noise recordings at two different IR ports located at the Swiss Light Source and SOLEIL (France), under conditions relevant to real experiments, are discussed. The lowest electron beam fluctuations detectable in IR spectra have been quantified and are shown to be much smaller than what is routinely recorded by beam-position monitors.ISSN:0909-0495ISSN:1600-577