Preparation, characterization and application of a stationary chromatographic phase from a new (+)-tartaric acid derivative

The preparation, characterization and application of a new stationary phase derived from 1,4-cyclohexanedione and diethyl (+)-tartrate are described. A suitable TADDOL for immobilization has been synthesized and grafted to a γ-mercaptopropylsilylated silica gel. The resulting modified stationary phase has been characterized and its ability to separate enantiomers has been studied. While the free TADDOL in solution was able to resolve a range of enantiomers, the resolving properties were lost on immobilization. Solid state ¹³C CPMAS NMR of the new stationary phase was used to explain the lack of stereoselective recognition.     

Constraints on two-lepton two-quark operators

Physics from beyond the Standard Model, such as leptoquarks, can induce four fermion operators involving a quark, an anti-quark, a lepton and an anti-lepton. We update the (flavour-dependent) constraints on the coefficients of such interactions, arising from collider searches for contact interactions, meson decays and other rare processes. We then make naive estimates for the magnitude of the coefficients, as could arise in texture models or from inverse hierarchies in the kinetic term coefficients. These “expectations” suggest that rare kaon decays could be a good place to look for such operators.     

Mean field loops versus quantum anti-crossing nets in trapped Bose-Einstein condensates

We study a Bose-Einstein condensate trapped in an asymmetric double well potential. Solutions of the time-independent Gross-Pitaevskii equation reveal intrinsic loops in the energy (or chemical potential) level behavior when the shape of the potential is varied. We investigate the corresponding behavior of the quantum (many-body) energy levels. Applying the two-mode approximation to the bosonic field operators, we show that the quantum energy levels create an anti-crossing net inside the region bounded by the loop of the mean field solution. Received 6 March 2002 / Received in final form 19 September 2002 Published online 15 November 2002 RID="a" ID="a"e-mail: smerzi@cnls.lanl.gov     

Accelerator neutrino beams

Neutrino beams at from high-energy proton accelerators have been instrumental discovery tools in particle physics. Neutrino beams are derived from the decays of charged π$\pi$ and K   mesons, which in turn are created from proton beams striking thick nuclear targets. The precise selection and manipulation of the π/K$\pi /K$ beam control the energy spectrum and type of neutrino beam. This article describes the physics of particle production in a target and manipulation of the particles to derive a neutrino beam, as well as numerous innovations achieved at past experimental facilities.     

On the effect of the carbonaceous substrate in the nucleation of Sn nanoparticles for Li-ion anodes: experiments and first principles calculations

The nucleation of Sn nanoparticles by chemical reduction was studied using three different carbonaceous substrates, to obtain Sn/C composites. When used as active materials in anodes for lithium-ion batteries, these composites displayed higher capacities than commercially used graphite, and showed a good cyclability. The differences in morphology, capacity, cyclability, and diffusion between the resulting materials are highlighted. The resulting materials were characterized by charge-discharge cycling, voltammetry, EIS, SEM, and TEM microscopy. It was found that the substrate has a determinant effect on the deposition of Sn. This effect is interpreted in terms of the relative adsorption energies of a single Sn atom obtained from DFT calculations.

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