Simultaneous determination of60Co,131I and137Cs in model radioactive waste water by reverse radiometric flow injection analysis with the aid of a multichannel analyzer

Reverse radiometric flow injection analysis was used for the simultaneous determination of⁶⁰Co,¹³¹I and¹³⁷Cs in model radioactive waste water. A NaI (Tl) scintillation detector coupled to a Canberra MCA was used for measuring the activity of¹³⁷Cs at 662 keV,⁶⁰Co at 1173 keV and 1332 keV, and¹³¹I at 364 keV.     

How Strain Affects the Reactivity of Surface Metal Oxide Catalysts

Highly dispersed molybdenum oxide supported on mesoporous silica SBA‐15 has been prepared by anion exchange resulting in a series of catalysts with changing Mo densities (0.2–2.5 Mo atoms nm^?2). X‐ray absorption, UV/Vis, Raman, and IR spectroscopy indicate that doubly anchored tetrahedral dioxo MoO₄ units are the major surface species at all loadings. Higher reducibility at loadings close to the monolayer measured by temperature‐programmed reduction and a steep increase in the catalytic activity observed in metathesis of propene and oxidative dehydrogenation of propane at 8 % of Mo loading are attributed to frustration of Mo oxide surface species and lateral interactions. Based on DFT calculations, NEXAFS spectra at the O‐K‐edge at high Mo loadings are explained by distorted MoO₄ complexes. Limited availability of anchor silanol groups at high loadings forces the MoO₄ groups to form more strained configurations. The occurrence of strain is linked to the increase in reactivity.     

Complex dynamic behavior of fluctuating smectic- A films as studied by scattering with coherent X-rays

Coherent dynamic x-ray scattering has been used to study the thermally excited layer fluctuations in freely suspended smectic films of the compound 4O.8. Using 8-keV x rays and films with a thickness around 0.3 &mgr;m we resolve relaxation times down to a few &mgr;s. A combination of damped and oscillatory behavior is observed for the layer undulations, which can be attributed to inertial effects. These are due to the surface contribution to the free energy which cannot be disregarded for thin films.     

Anomaly in the Spectrum of Galactic Cosmic Ray Nuclei in Olivine Crystals from Meteorites

Physics of Atomic Nuclei - An anomaly in the spectra of galactic cosmic ray nuclei in olivine crystals from meteorites that arises in the charge spectra upon studying crystals situated near the...     

Determination of eddy transport coefficients in thermo-lattice Boltzmann modeling of two-dimensional turbulence

Thermal Lattice Boltzmann (TLBE) techniques are used to consider the time evolution of free-decaying two dimensional (2D) turbulence induced by a double velocity shear layer. In particular, we consider the effect of this turbulence at a Reynolds number of 2555 on a strong temperature gradient. Since all structures are resolved on the 1024×1024 grid, the Smagorinsky model is employed to compute directly the eddy viscosity and eddy diffusivity. These transport coefficients play an integral part in large eddy simulations at very high Reynolds numbers where a direct simulation cannot resolve all excited scales. TLBE codes have the virtue of being readily extended to 3D, can readily handle nonperiodic geometries, and are ideally suited for multi-parallel computer architectures.This work was supported by a joint US-Czech DoE Grant #93066. Computations were performed under the auspices of the SPP (Special Parallel Processing) on the C90 at NERSC.     

Circulation flow patterns in the Faraday waves in the presence of damper plates

The effect of transverse damper plates on the restructurization of a suspension with originally homogeneous concentration in the field of standing surface waves in a vertically oscillating rectangular reservoir is for the first time experimentally investigated. The flow pattern evolution and the formation of the fine flow structure are traced in reservoirs with smooth walls, with one vertical deflecting plate, and with two plates mounted in parallel or antiparallel at the center of the larger side. The symmetry of the surface wave flow is determined by the plate configuration.     

Wave attenuation in a vessel equipped with damper plates

The effect of vertical damper plates mounted at the center of a rectangular vessel normal or at an angle to a wave flow is experimentally investigated for the first mode of the standing surface waves excited at the parametric resonance. The variation of the resonance curves and the wave attenuation degree are discussed. The fluid depth effect on the wave motion damping is evaluated.     

Estimation of the Fragmentation Effect in the Registration of Superheavy Nuclei of Galactic Cosmic Rays in Pallasites

Journal of Experimental and Theoretical Physics - We report on the results of model calculations for estimating the fragmentation effect in the registration of heavy and superheavy nuclei of...     

Investigation of Dynamics of Heat Propagation in Meteorite Matter and Its Influence on Geometric Features of Tracks of Nuclei in Olivine Crystals from Meteorites

Physics of Atomic Nuclei - The dynamics of heating of a meteorite that travels through the Earth’s atmosphere is studied. The heating of its matter over the meteorite fall time is estimated...