Structural evolution of small gold clusters doped by one and two boron atoms

The potential energy surfaces (PES) of a series of gold–boron clusters with formula Au_nB (n = 1–8) and Au_mB₂ (m = 1–7) have been explored using a modified stochastic search algorithm. Despite the complexity of the PES of these clusters, there are well‐defined growth patterns. The bonding of these clusters is analyzed using the adaptive natural density partitioning and the natural bonding orbital analyses. Reactivity is studied in terms of the molecular electrostatic potential. © 2014 Wiley Periodicals, Inc.     

Liquid chromatographic determination of alcohols in food and beverages with indirect polarimetric detection using a beta-cyclodextrin mobile phase.

An indirect polarimetric detection method for the determination of alcohols has been proposed in liquid chromatography (LC). Optically active mobile-phase additives, such as beta-cyclodextrin (beta-CD), could be used to visualize optically inactive alcohols in reversed-phase LC. The visualization of alcohols is based on a perturbation of the partition of beta-CD caused by the alcohols. The detection limits of the present system at a signal-to-noise ratio of 3 were 0.031, 0.019, 0.018, 0.013, 0.011, 0.008 and 0.008% (v/v) for ethanol, 2-propanol, 1-propanol, 2-methyl-2-propanol, 2-butanol, 2-methyl-1-propanol and 1-butanol, respectively. The method was successfully applied to the determination of ethanol present in food and beverage samples.     

Waveguides and gratings fabrication in zirconium-based organic/inorganic hybrids

Sol–gel derived poly(oxyethylene)/siloxane organic/inorganic di-ureasil hybrids containing different amounts of methacrylic acid (McOH, CH₂=C(CH₃)COOH)) modified zirconium oxo-clusters (Zr-OMc) were processed as thin films deposited in glassy substrates via spin coating and as transparent and shape controlled monoliths. Channel monomode waveguides and diffraction gratings were UV patterned using the Talbot interferometer and the Lloyd mirror interferometer experimental setups. The time dependence of the diffraction gratings efficiency was studied for hybrids containing different amounts of Zr-OMc. Finally, the number of propagating modes and the refractive index gradient within the waveguide region, determined as a Gaussian section located below the patterned channel, was evaluated and modeled, a maximum index contrast of 2.43 × 10^?5 being estimated.     

Particle energization in an expanding magnetized relativistic plasma

Using a 21 / 2-dimensional particle-in-cell (PIC) code to simulate the relativistic expansion of a magnetized collisionless plasma into a vacuum, we report a new mechanism in which the magnetic energy is efficiently converted into the directed kinetic energy of a small fraction of surface particles. We study this mechanism for both electron-positron and electron-ion (m(i)/m(e)=100, m(e) is the electron rest mass) plasmas. For the electron-positron case, the pairs can be accelerated to ultrarelativistic energies. For electron-ion plasmas, most of the energy gain goes to the ions.     

Bifurcation and Lorentz-factor scaling of relativistic magnetized plasma expansion

We report the long-term results of 2 1/2-dimensional particle-in-cell simulations of the relativistic expansion of strongly magnetized electron-positron plasmas. When the simulation is carried to >150 light-crossing time of the initial plasma, the plasma pulse exhibits a number of remarkable properties. These include the repeated bifurcation of the pulse profile, development of a power-law momentum distribution with low-energy cutoff, and a simple scaling law for the peak Lorentz factor.     

An eight-coil high-frequency probehead design for high-throughput nuclear magnetic resonance spectroscopy

In order to increase the throughput of high-resolution nuclear magnetic resonance spectroscopy a multiple-coil probe, which enables the simultaneous analysis of eight different samples, was designed. The probe, consisting of eight identical solenoidal coils, was constructed for operation at 600 MHz. By using four receivers and radiofrequency switches, spectra from eight different chemical solutions were acquired in the time normally required for one. Two-dimensional COSY, gradient COSY, and TOCSY data have been acquired. Intercoil electrical isolation was between 25 and 45 dB, with signal cross-talk between approximately 1 and 5% measured by NMR. The spectral linewidths for the eight coils were between 3 and 6Hz for a single optimized shim setting.     

Microcolumn ion chromatography of inorganic anions using bovine serum albumin stationary phase with indirect photometric detection

Summary Microcolumn ion chromatography of inorganic anions has been studied using bovine serum albumin immobilized on silica gel as a stationary phase. Several mobile phase solutions were examined, involving sodium iodide, potassium hydrogen phthalate, 2,6-anthraquinone disulfonate (2,6-AQDS) and sodium salicylate. 2,6-AQDS achieved better separation of the analytes tested. Chloride, nitrate, iodide, thiocyanate and sulphate could be separated within 8 min. Detection limits were in the range of 0.9–2.9 M, corresponding to mass detection limits of 0.18–0.59 pmol. The system was applied to the determination of inorganic anions in environmental water and biological samples.