Determination of f(s)/f(d) for 7 TeV pp collisions and measurement of the B0→D-K+ branching fraction

The relative abundance of the three decay modes B(0)→D(-)K(+), B(0)→D(-)π(+), and B(s)(0)→D(s)(-)π(+) produced in 7 TeV pp collisions at the LHC is determined from data corresponding to an integrated luminosity of 35 pb(-1). The branching fraction of B(0)→D(-)K(+) is found to be B(B(0)→D(-)K(+)) = (2.01 ± 0.18(stat) ± 0.14(syst)) × 10(-4). The ratio of fragmentation fractions f(s)/f(d) is determined through the relative abundance of B(s)(0)→D(s)(-)π(+) to B(0)→D(-)K(+) and B(0)→D(-)π(+), leading to f(s)/f(d) = 0.253 ± 0.017 ± 0.017 ± 0.020, where the uncertainties are statistical, systematic, and theoretical, respectively.     

Substituent effects upon the catalytic activity of aromatic cyclic seleninate esters and spirodioxyselenuranes that act as glutathione peroxidase mimetics

Substituent effects were studied in a series of aromatic cyclic seleninate esters and spirodioxyselenuranes that function as mimetics of the antioxidant selenoenzyme glutathione peroxidase. The methoxy-substituted selenurane proved the most efficacious catalyst for the reduction of hydrogen peroxide with benzyl thiol, and the reaction rates were enhanced for both classes by electron-donating substituents. Hammett plots indicated rho = -0.45 and -3.1 for the seleninates and selenuranes, respectively, suggesting that oxidation at Se is the rate-determining step in their catalytic cycles.     

Synthesis and X‐ray Structural Characterization of the Polymeric Cluster Compound [Hg3(O2SePh)(SePh)5]n

Two synthetic routes to prepare [Hg₃(O₂SePh)(SePh)₅]_n and its structural characterization are presented in this paper. This compound results either from the partial oxidation of mercury phenylselenolate clusters or from a mixture of its components with defined stoichiometry. This compound was observed in almost all of our reactions as a by‐product, during the development of the synthesis of new mercury selenolate clusters. It was now characterized by single‐crystal X‐ray diffractometry, elemental analysis, and infrared spectroscopy.     

Energy dependence of directed flow over a wide range of pseudorapidity in Au + Au collisions at the BNL Relativistic Heavy Ion Collider

We report on measurements of directed flow as a function of pseudorapidity in Au + Au collisions at energies of square root of SNN = 19.6, 62.4, 130 and 200 GeV as measured by the PHOBOS detector at the BNL Relativistic Heavy Ion Collider. These results are particularly valuable because of the extensive, continuous pseudorapidity coverage of the PHOBOS detector. There is no significant indication of structure near midrapidity and the data surprisingly exhibit extended longitudinal scaling similar to that seen for elliptic flow and charged particle pseudorapidity density.     

Recent results from PHOBOS

The PHOBOS Collaboration has measured charged particles emitted over the range ?5.4<η<5.4 for Au+Au collisions at energies of $\sqrt {s_{NN} } = 19.6$ , 62.4, 130 and 200 GeV. In this contribution I will present recent results on the pseudorapidity distributions, total charged-particle production, and collective flow of particles obtained from these measurements.     

pH-dependent electron-transport properties of carbon nanotubes

Carbon nanotube electrochemical transistors integrated with microfluidic channels are utilized to examine the effects of aqueous electrolyte solutions on the electron-transport properties of single isolated carbon nanotubes. In particular, pH and concentration of supporting inert electrolytes are examined. A systematic threshold voltage shift with pH is observed while the transconductance and subthreshold swing remain independent of pH and concentration. Decreasing pH leads to a negative shift of the threshold voltage, indicating that protonation does not lead to hole doping. Changing the type of contact metal does not alter the observed pH response. The pH-dependent charging of SiO2 substrate is ruled out as the origin based on measurements with suspended nanotube transistors. Increasing the ionic strength leads to reduced pH response. Contributions from possible surface chargeable chemical groups are considered.     

Hydrogen sorption on palladium-doped sepiolite-derived carbon nanofibers

The hydrogen sorption behavior of novel Pd-doped sepiolite-derived carbon nanofibers (SDCNs) was investigated. Two chemical doping methods of ethanol/toluene reduction and a polyol process were applied to control Pd(0) formation in the SDCNs at different Pd doping levels. Hydrogen storage capacity was observed to vary depending on the Pd particle size and doping amount as the Pd particle surface area and the carbon Brunauer-Emmett-Teller (BET) surface area change with them, suggesting the existence of an optimum Pd doping level at each doping method for the best hydrogen storage capacity. Among the samples prepared using the polyol method at different Pd amounts, the maximum hydrogen uptake of about 0.41 wt % was obtained at 298 K and 90 bar for the 5 wt % Pd-doped SDCN that has a relatively high Pd particle surface area and carbon BET surface area. Samples prepared using the ethanol/toluene reduction method exhibited a higher hydrogen uptake of about 0.59 wt % at lower Pd doping levels (3 wt % Pd) due to a smaller Pd particle size and relatively high carbon BET surface area. The hydrogen desorption behavior investigated by differential scanning calorimeter exhibited that a higher amount of hydrogen desorbed at around 860 K from the Pd-doped SDCNs compared to that from the undoped SDCN. Fourier transform infrared (FTIR) spectroscopic analysis suggested that some of the weak chemisorbed hydrogen changes to a normal covalent bond during the heating and effuses at around 860 K.     

A Relation Between Closure Operators on a Small Category and Its Category of Presheaves

In this paper we show that each factorization structure on a small category , satisfying certain conditions, yields a presheaf on and a morphism of presheaves . We then give connections, and set up one to one correspondences, between subclasses of the following classes: (a) closure operators on (b) subobjects of (c) morphisms from to (d) weak Lawvere–Tierney topologies (e) weak Grothendieck topologies (f) closure operators on .     

Evidence for CP violation in time-integrated D0→h(-)h(+) decay rates

A search for time-integrated CP violation in D(0)→h(-)h(+) (h=K, π) decays is presented using 0.62 fb(-1) of data collected by LHCb in 2011. The flavor of the charm meson is determined by the charge of the slow pion in the D(*+)→D(0)π(+) and D(*-)→D[over ˉ](0)π(-) decay chains. The difference in CP asymmetry between D(0)→K(-)K(+) and D(0)→π(-)π(+), ΔA(CP)≡A(CP)(K(-)K(+))-A(CP)(π(-)π(+)), is measured to be [-0.82±0.21(stat)±0.11(syst)]%. This differs from the hypothesis of CP conservation by 3.5 standard deviations.