Hydrodynamics within the electric double layer on slipping surfaces

We show, using extensive molecular dynamics simulations, that the dynamics of the electric double layer (EDL) is very much dependent on the wettability of the charged surface on which the EDL develops. For a wetting surface, the dynamics, characterized by the so-called zeta potential, is mainly controlled by the electric properties of the surface, and our work provides a clear interpretation for the traditionally introduced immobile Stern layer. In contrast, the immobile layer disappears for nonwetting surfaces, and the zeta potential deduced from electrokinetic effects is considerably amplified by the existence of a slippage at the solid substrate.     

Spectroscopic study of the ν1 band of SO2 using a continuous-wave DFB QCL at 9.1 μm

We report results of spectroscopic measurements with a continuous-wave distributed-feedback quantum-cascade laser (DFB QCL). Line intensities and self-broadening coefficients were measured in the ₁ band of SO₂ between 1088 and 1090 cm^-1. The self-broadening coefficients in this paper confirm the typical decrease of _self with increasing rotational quantum number K_a . The line intensities determined here are smaller than those in the HITRAN 2000 database. Several lines found in this study were not present in the database. PACS 07.57.Ty; 33.20.Ea     

Optimization of a compact photoacoustic quantum cascade laser spectrometer for atmospheric flux measurements: application to the detection of methane and nitrous oxide

Room temperature (RT) quantum cascade lasers (QCL) are now available even in continuous wave (cw) mode, which is very promising for in situ gas detectors. Ambient air monitoring requires high sensitivity with robust and simple apparatus. For that purpose, a compact photoacoustic setup was combined with two cw QCLs to measure ambient methane and nitrous oxide in the 8 μm range. The first laser had already been used to calibrate the sensitivity of the photoacoustic cell and a detection limit of 3 ppb of CH₄ with a 1s integration time per point was demonstrated. In situ monitoring with this laser was difficult because of liquid nitrogen cooling. The second laser is a new RT cw QCL with lower power, which enabled one to reach a detection limit of 34 ppb of methane in flow. The loss in sensitivity is mainly due to the weaker power as photoacoustic signal is proportional to light power. The calibration for methane detection leads to an estimated detection limit of 14 ppb for N₂O flux measurements. Various ways of modulation have been tested. The possibility to monitor ambient air CH₄ and N₂O at ground level with this PA spectrometer was demonstrated in flux with these QCLs. PACS 07.88; 92.60.Sz     

Comparison of strange baryon production at LEP with various models

The strange baryon production rates measured at LEP are compared to several models: isospin, LPHD, QCM, Jetset, Herwig and MOPS. In particular, the parameters of the new MOPS model are adjusted in an attempt to reproduce the spin and strangeness dependence of the observed rates. Received: 8 April 1998 / Revised version: 27 August 1998 / Published online: 19 November 1998     

TPD and ITPD study of materials used as chemoresistive gas sensors

Temperature-programmed desorption (TPD) and a differential form of it, called intermittent temperature-programmed desorption (ITPD), turned out to be powerful characterising techniques for chemoresistive materials applied to gas sensing. We investigated samples of SnO₂, TiO₂ and solid solutions of them (Ti_xSn_1 ? xO₂). TPD and ITPD experiments were carried out in vacuum, with samples previously treated in pure O₂ (100 Torr, 500 °C, 30 min). Amounts of desorbed O₂ corresponded for all Ti-containing samples to less than 10% of a compact monolayer of ions O^2?. Corresponding values of the apparent activation energy of desorption (E_app) were calculated directly from the Arrhenius plots for each partial TPD and ranged from about 100 to 330 kJ mol^? 1 (1.16 to 3.82 eV).     

4‐Benzoyl‐3,4‐dihydro‐2H‐1,4‐benzoxazine‐2‐carbonitrile: refinement using a multipolar atom model

The structural model for the title compound, C₁₆H₁₂N₂O₂, was refined using a multipolar atom model transferred from an experimental electron‐density database. The refinement showed some improvements of crystallographic statistical indices when compared with a conventional spherical neutral‐atom refinement. The title compound adopts a half‐chair conformation. The amide N atom lies almost in the plane defined by the three neighbouring C atoms. In the crystal structure, molecules are linked by weak intermolecular C—H...O and C—H...π hydrogen bonds.     

Experimental determination of the helicoidal electric field inside a twisted mesophase, in the selective reflection band

We consider the interface between a twisted birefringent mesophase and an isotropic medium. In the selective reflection band, when illuminated at normal incidence, the interface creates a coupling between the located dielectric reflection and the spread selective reflection. This coupling enables experimental measurement of the standing electric field orientation inside the liquid crystal.     

Verbesserungen von Wagen

Ohne Zusammenfassung     

Ground state of the quasi-1D compound BaVS3 resolved by resonant magnetic x-ray scattering

Resonant magnetic x-ray scattering near the vanadium L2,3-absorption edges has been used to investigate the low temperature magnetic structure of high quality BaVS3 single crystals. Below T(N)=31 K, the strong resonance revealed a triple-incommensurate magnetic ordering at the wave vector (0.226 0.226 ξ) in hexagonal notation, with ξ=0.033. The azimuthal-angle dependence of the scattering signal and time-dependent density functional theory simulations indicate an antiferromagnetic order within the ab plane with the spins polarized along a in the monoclinic structure.