Telematics applications in a laboratory cluster

 The laboratories of six hospitals in the Canton of Wallis in Switzerland have been connected to one central laboratory, using the same database, the same software applications for the laboratory, pathology and pharmacy, and the same office and administration software. Some instruments in "Point of Care" sites are online for result transmission and for telemaintenance. The physicians may order drugs, material for sampling, analyses for specified patients and may consult knowledge bases, the patient data base, results and reports in different formats (ASCII, HTML, PDF, JPG, GIF, ...) using browsers like Netscape or MS-Explorer. To guarantee privacy, the access is restricted and protected by user-name, password and firewall. This report describes conditions for a successful introduction and usage of quality management through laboratory telematics. Received: 15 April 2000 · Accepted: 15 April 2000     

Oxygen reduction on a platinum cluster

The reaction Pt₅O₂(ads)+H⁺(aq)+e⁻→Pt₅–OOH is analyzed on the basis of density functional theory calculations. It is found that the electron transfer process takes place gradually as the hydronium ion gets close to the adsorbed oxygen. At a certain small O_ads–H⋯O_water distance, the barrier for proton and electron transfer becomes negligible. The effect of an electric field on the reaction is studied by charging the metal/adsorbate complex, and that of a solvation shell on the proton transfer process is explored by using the H₃O⁺(H₂O)₂ ion cluster to model the hydrated proton.     

Trapping a pseudo-Hofmann rearrangement on a ruthenium cluster

In the clusters [Ru3(micro(3)-NPPh(3))(micro(3)-OSiMe(3))(micro-X)(micro(C,O)-OC[double bond]NPPh(3))(micro-CO)(CO)6] (X = NCO, 2; X = Cl, 3), which were prepared by a pyrolytic reaction of Ph(3)PNSiMe(3) with Ru(3)(CO)12, the ligands result from a cluster-mediated pseudo-Hofmann rearrangement involving the micro-NCO, micro(C,O)-Ph(3)P[double bond]N-CO and micro(3)-NPPh(3) fragments.     

Gold cluster formation on a fullerene surface

The growth of Au clusters on a fullerene thin film was investigated by in situ photoelectron spectroscopy in the ultraviolet (UPS) and x-ray (XPS) regime. Due to its highly corrugated surface fullerene films provide a wide range of bonding sites which could be exploited as molecular templates and serve to create a cluster superstructure. To gain insight into the fullerene-Au interaction two types of experiments were performed: (i) the deposition of Au on a fullerene surface, and (ii) the deposition of fullerenes on a Au surface. In both experiments an island growth mode is observed. The deposition of submonolayer amounts of C60 onto a gold film showed that the main interaction of the two species is due to chemisorption of the first C60 monolayer. In addition a constant band bending in the fullerene film is detected, but the UPS valence-band spectra show that there is no charge transfer from the Au to the C60 lowest unoccupied molecular orbital. In the reverse experiment, the cluster growth of Au on the corrugated C60 surface, the analysis of the Au core level does not reveal a specific bonding or nucleation site for Au atoms and clusters. This is in contrast to observations with Si clusters, which prefer to reside in the troughs between the fullerene molecules. The Au clusters grow continually from a size of about 55 atoms for the early stages of growth up to 150 atoms for the deposition of a nominal coverage of 1.5 nm. These data are derived from an analysis of the d-band splitting and the Au 4f core-level shift due to delayed photohole relaxation. The thermal stability of the Au-clusters-covered fullerene film was investigated by annealing in situ up to temperatures of 650 degrees C. For temperatures up to 450 degrees C a continuous growth of the clusters is detected, which is accompanied by a slight drop in Au concentration in the range of XPS for annealing temperatures higher than 350 degrees C. This may be due to a ripening of the clusters. The presence of Au apparently delays fullerene sublimation. The film shows a very good thermal stability and even after annealing at 650 degrees C there is still a fullerene film detectable in the photoelectron spectroscopy spectra.     

Hydrogen tautomerism in a rhenium cluster compound

The hydrogen tautomerism in the hydrido carbonyl cluster compound of rhenium [H₄Re₄(CO)₁₅](NEt₄)₂ has been studied by analysis of the PMR spectra at different temperatures.     

Dodecanuclear water cluster in bowl: microwave-assisted synthesis of a heptanuclear cobalt(II) cluster

A heptanuclear double-bowl-like cluster [Co₇(mmp)₆(OH)₆]₂·(ClO₄)₂·12H₂O (1·12H₂O, Hmmp is 2-methoxy-6-methyliminomethyl-phenol) has been synthesized through the microwave-assisted reaction of Co(ClO₄)₂·6H₂O with 2-hydroxy-3-methoxy-benzaldehyde (Hhmb) and methylamine in mixed solvent (acetonitrile : distilled water = 9 : 1) for 29 min. 1·12H₂O was heated until 180 °C and it formed a non-water complex [Co₇(mmp)₆(OH)₆]₂·(ClO₄)₂ (1). The core of 1·12H₂O can be described as a double bowl, while the dodecanuclear water cluster stands on the bowl. Magnetic investigations show that 1·12H₂O and 1 display ferromagnetic interaction between cobalt ions. Moreover, 1 shows single molecular magnet behavior under 2 K. Magnetic studies indicate that hydrogen bond plays a vital role in transferring magnetic exchange effects.     

Infrared spectroscopy of niobium oxide cluster cations in a molecular beam: identifying the cluster structures

Infrared spectra of niobium oxide cluster cations are measured via IR multiple photon dissociation spectroscopy in the 400-1650 cm(-1) region. The cluster cations are obtained directly from a laser vaporization source and irradiated with the infrared light emitted by a free electron laser. For those oxide clusters that fragment after excitation, the IR spectra are recorded by measuring the cluster intensity changes as a function of the IR wavelength. The spectra of all examined oxide clusters exhibit two main absorption features that can be assigned to vibrations of terminal (Nb=O) or bridging (Nb-O-Nb) oxide groups. For selected clusters DFT calculations at the B3LYP/LACVP* level have been performed and the calculated vibrational spectra are compared to the experimental data to identify the gas phase structures of the clusters.     

What size cluster is like a surface?

The sizes for which the surface free energy, enthalpy and entropy of a cluster approach those of the bulk planar surface to any desired extent can be obtained from the relations given. Sizes are shown for a non-polar substance, for a polar substance (water), and for bare clusters of metal atoms.     

Electron attachment to molecules in a cluster environment

Low-energy dissociative electron attachment (DEA) to the CF(2)Cl(2) and CF(3)Cl molecules in a water cluster environment is investigated theoretically. Calculations are performed for the water trimer and water hexamer. It is shown that the DEA cross section is strongly enhanced when the attaching molecule is embedded in a water cluster, and that this cross section grows as the number of water molecules in the cluster increases. This growth is explained by a trapping effect that is due to multiple scattering by water molecules while the electron is trapped in the cluster environment. The trapping increases the resonance lifetime and the negative ion survival probability. This confirms qualitatively existing experiments on electron attachment to the CF(2)Cl(2) molecule placed on the surface of H(2)O ice. The DEA cross sections are shown to be very sensitive to the position of the attaching molecule within the cluster and the orientation of the electron beam relative to the cluster.