Observation of decays B0-->Ds(*)+ pi- and B0-->Ds(*)- K+

We report the observation of decays B{0}-->D{s}{(*)+}pi- and B{0}-->D{s}{(*)-}K+ in a sample of 230 x 10(6) Upsilon(4S)-->BB[over] events recorded with the BABAR detector at the SLAC PEP-II asymmetric-energy e+ e- storage ring. We measure the branching fractions B(B{0}-->D{s}{+}pi-)=(1.3+/-0.3(stat)+/-0.2(syst))x10(-5), B(B{0}-->D{s}{-} K+)=(2.5+/-0.4(stat)+/-0.4(syst))x10(-5), B(B{0}-->D{s}{*+}pi-)=(2.8+/-0.6(stat)+/-0.5(syst))x10(-5), and B(B{0}-->D{s}{*-}K+)=(2.0+/-0.5(stat)+/-0.4(syst))x10(-5). The significances of the measurements to differ from zero are 5, 9, 6, and 5 standard deviations, respectively. This is the first observation of B{0}-->D{s}{+}pi-, B{0}-->D{s}{*+}pi-, and B{0}-->D{s}{*-}K+ decays.     

How solvent controls electronic energy transfer and light harvesting: toward a quantum-mechanical description of reaction field and screening effects

This paper presents a quantum-mechanical study of electronic energy transfer (EET) coupling on over 100 pairs of chromophores taken from photosynthetic light-harvesting antenna proteins. Solvation effects due to the protein, intrinsic waters, and surrounding medium are analyzed in terms of screening and reaction field contributions using a model developed recently that combines a linear response approach with the polarizable continuum model (PCM). We find that the screening of EET interactions is quite insensitive to the quantum-mechanical treatment adopted. In contrast, it is greatly dependent on the geometrical details (distance, shape, and orientation) of the chromophore pair considered. We demonstrate that implicit (reaction field) as well as screening effects are dictated mainly by the optical dielectric properties of the host medium, while the effect of the static properties is substantially less important. The empirical distance-dependent screening function we proposed in a recent letter (Scholes, G. D.; Curutchet, C.; Mennucci, B.; Cammi, R.; Tomasi, J. J. Phys. Chem. B 2007, 111, 6978-6982) is analyzed and compared to other commonly used screening factors. In addition, we show that implicit medium effects on the coupling, resulting from changes in the transition densities upon solvation, are strongly dependent on the particular system considered, thus preventing the possibility of defining a general empirical expression for such an effect.     

Measurement of the Time-Dependent CP Asymmetry in B;{0}-->D_{CP};{(*)}h;{0} Decays

We report a measurement of the time-dependent CP-asymmetry parameters S and C in color-suppressed B{0}-->D{(*)0}h{0} decays, where h{0} is a pi{0}, eta, or omega meson, and the decays to one of the CP eigenstates K+K-, K{S}{0}pi{0}, or K{S}{0}omega. The data sample consists of 383 x 10{6} Upsilon(4S)-->BB decays collected with the BABAR detector at the PEP-II asymmetric-energy B factory at SLAC. The results are S=-0.56+/-0.23+/-0.05 and C=-0.23+/-0.16+/-0.04, where the first error is statistical and the second is systematic.     

Measurement of CP-violating asymmetries in B0-->D*(+/-)D(-/+)

We present updated measurements of CP-violating asymmetries in the decays B0-->D*(+/-)D(-/+) and B0-->D+D- using (383+/-4) x 10(6)B(B) pairs collected by the BABAR detector at the SLAC PEP-II B factory. We determine the time-integrated CP asymmetry A(D*(+/-)D(-/+))=0.12+/-0.06+/-0.02, and the time-dependent asymmetry parameters to be C(D*+D-)=0.18+/-0.15+/-0.04, S(D*+D-)=-0.79+/-0.21+/-0.06, C(D*-D+)=0.23+/-0.15+/-0.04, S(D*-D+)=-0.44+/-0.22+/-0.06, C(D+D-)=0.11+/-0.22+/-0.07, and S(D+D-)=-0.54+/-0.34+/-0.06, where the first uncertainty is statistical and the second is systematic.     

Proportional share analysis

The purpose of this paper is to generalize the theory of “equal share analysis”, developed by Selten in 1972, to the one in which every player has a positive weight. We show that for any positive vector of weights, α∈R ₊₊ ^N , it is always possible to find a coalition structure and a payoff vector forming a proportional regular configuration.     

Excitation spectrum of TTF-TCNQ: a finite temperature calculation

In this paper we study the excitation spectrum of the organic conductor tetrathiafulvalene-tetracyanoquinodimethane (TTF-TCNQ) using finite temperature calculations. The effect of electronelectron interaction is considered within the random phase approximation (RPA). Our results show the temperature dependent plasmon and dipolar mode corresponding qualitatively to the modes obtained previously using zero temperature formalism assigned to the observed excitations at 10 meV and 0.75 eV. These modes have an essential influence on the energy-loss function. The obtained results are in good qualitative agreement with the optical and EELS data of TTF-TCNQ.     

Copper-free intramolecular alkyne-azide cycloadditions leading to seven-membered heterocycles

Treatment of alk-2-ynyl derivatives of enantiopure phenylglycidol with NaN(3) triggers a cascade reaction consisting of stereospecific and regioselective epoxide ring opening followed by intramolecular azide-alkyne cycloaddition under strictly metal-free conditions. This simple one-pot procedure allows a fast buildup of molecular complexity, generating a wide array of triazolooxazepinols, triazolodiazepinols, and triazolothiazepinols.     

Towards the computational modelling of polyoxoanions on metal surfaces: IR spectrum characterisation of [SiW12O40](4-) on Ag(111)

The adsorption of a polyoxometalate (POM) on a metal surface has been studied by means of a periodic plane wave DFT based method for the first time. In particular, we have analysed the most favourable adsorption sites of anion [SiW(12)O(40)](4-) on the Ag(111) surface and computed the infrared spectrum. Despite the intrinsic complexity of the system we have been able to fairly reproduce the observed IR spectrum and unambiguously discern the signal corresponding to W-O-Ag symmetric stretching, which appears at around 800 cm(-1).     

Reactivity of stoichiometric titanium oxide cations

We present the results of a reactivity study of titanium cationic clusters towards CO, C(2)H(2), C(2)H(4) and C(3)H(6) based on guided-ion-beam mass spectrometry and DFT calculations. We identified Ti(2)O(4)(+) and to a lesser extent TiO(2)(+) species which preferentially undergo oxidation reactions. An oxygen centered radical of Ti(2)O(4)(+) is responsible for selective oxidation. Energy profiles and MD simulations reveal the mechanisms of the reactions. Regeneration of the oxygen centered radical was achieved experimentally and theoretically through the reaction of N(2)O with Ti(2)O(3)(+).