Vector boson decays of the Higgs boson

We derive the width of the Higgs boson into vector bosons. General formulas are derived both for the on–shell decay as well for the off–shell decays, and , where . For the off-shell decays the width of the decaying vector boson is properly included. The formulas are valid both for the Standard Model as well as for arbitrary extensions. As an example we study in detail the gauge-invariant effective Lagrangian models where we can have sizable enhancements over the Standard Model that could be observed at LEP. Received: 31 July 1998 / Revised version: 23 September 1998 / Published online: 6 November 1998     

Fundamental study on the thermal regeneration stages of exhausted activated carbons: kinetics

In this work the thermal regeneration of activated carbons saturated with p-nitrophenol has been analysed. By thermogravimetry, it was possible to elucidate the different events taking place during the thermal treatment, and relate them to the type of adsorption in the interfacial system. It was found that the mass loss during thermal treatment comprises a complex process in which different stages are involved, such as drying, desorption of physisorbed adsorbate, breaking up of surface functional groups, cracking of products from adsorbate–surface-specific interactions, etc. The analysis of the textural and surface chemistry characteristics of the pristine and regenerated adsorbent confirmed the thermal desorption mechanisms. Moreover, a kinetic study based on temperature-programmed desorption and Suzuki models was performed, using thermogravimetry data at different heating rates (5–20 K min^?1). From this analysis, the values of activation energy involved in each degradation step were estimated.     

Irreversible electrostatic deposition of CdTe quantum dots on glassy carbon electrodes from colloidal solutions

Journal of Solid State Electrochemistry - Cadmium telluride quantum dots (CdTe-QDs) can be deposited from colloidal solutions on glassy carbon (GC) electrodes potentiostatically. The immobilization...     

Homoallylic <Emphasis Type="Italic">o</Emphasis>-halobenzylamines: asymmetric diversity-oriented synthesis of benzo-fused cyclic amines

The presence of a halogen atom in the proximity of a homoallylic amine, obtained by asymmetric addition of allylzinc bromide to the corresponding tert-butyl sulfinimine, makes them versatile building blocks suitable to participate in several palladium-catalyzed processes, such as the intramolecular Heck reaction or the Sonogashira cross-coupling. The thus obtained ortho-alkynyl derivatives display two unsaturated functional groups which may be further modified by means of the intramolecular Pauson–Khand reaction or the ring-closing enyne metathesis. In this way, a variety of benzo-fused amines can be obtained in 2–3 steps from readily available starting materials.     

Engineering Non‐sintered,Metal‐Terminated Tungsten Carbide Nanoparticles for Catalysis

Transition‐metal carbides (TMCs) exhibit catalytic activities similar to platinum group metals (PGMs), yet TMCs are orders of magnitude more abundant and less expensive. However, current TMC synthesis methods lead to sintering, support degradation, and surface impurity deposition, ultimately precluding their wide‐scale use as catalysts. A method is presented for the production of metal‐terminated TMC nanoparticles in the 1–4 nm range with tunable size, composition, and crystal phase. Carbon‐supported tungsten carbide (WC) and molybdenum tungsten carbide (Mo_xW_1?xC) nanoparticles are highly active and stable electrocatalysts. Specifically, activities and capacitances about 100‐fold higher than commercial WC and within an order of magnitude of platinum‐based catalysts are achieved for the hydrogen evolution and methanol electrooxidation reactions. This method opens an attractive avenue to replace PGMs in high energy density applications such as fuel cells and electrolyzers.     

Preparation of hydroxypropyl cellulose microfibers by high-speed rotary spinning and prediction of the fiber-forming properties of hydroxypropyl cellulose gels by texture analysis

Water-soluble, nonionic cellulose-based fibers were prepared from aqueous hydroxypropyl cellulose gels of 5–13-μm diameter by using a high-speed rotary spinning technique. A combination of texture analysis and viscosity measurement was applied to determine the optimum concentration of hydroxypropyl cellulose gels for fiber formation. The examined concentration range of hydroxypropyl cellulose gels was 38–52 % w/w. The textural properties including the adhesiveness of gels of different concentrations were determined based on the load-distance and load-time curves, while the obtained fiber formation was visually observed with an optical microscope. The texture analysis method enabled the determination of the optimum gel concentration from the point of fiber formation. An unequivocal correlation was determined between the adhesiveness of gels and their fiber-forming ability. The adhesiveness has a local minimum where the productivity of the fiber formation process and the micromorphology of the emitted fibers are optimal. Statistical analysis of the distribution of fiber diameters confirmed that in case of the optimum concentration, the distribution approaches normality. Mechanical properties of the prepared fibers were also evaluated using texture analysis, which indicated that the fibers made of gels of the suggested optimum concentration had the most desirable elastic behavior. An optimum concentration range of hydroxypropyl cellulose exists that enables fiber formation with the required characteristics from the point of further pharmaceutical formulation processing.