Search results for "Quartz"
showing 10 items of 239 documents
STOP 6: Morphology, internal structure and texture of inland dunes at the Smilškalni site, Middle Gauja Lowland
2014
Mylonites Derived From Parent Rocks Other Than Granites and Gneisses
2009
Most mylonites shown in this atlas are derived from granites and gneisses. This is not a coincidence; the mineralogy of these rocks favours the formation of mylonites because of the contrasting behaviour of quartz and biotite on the one hand (forming matrix) and feldspar and muscovite on the other hand (forming porphyroclasts). Another group of rocks that readily forms mylonites are impure quartzites in which resistant minerals tend to form fish-like structures, again, by strong contrast in rheological behaviour.
Quartz Crystal Microbalance And Electrical Impedance Characterization Of Nickel Dissolution Process.
2005
Abstract. The anodic nickel dissolution in acid media is analysed by means of EQCM and EIS techniques. The experimental impedance spectra have been fitted to the equivalent circuit which corresponds to two consecutive electron transfers followed by a Ni(II) desorption. That way rate constants and surface concentrations of the Ni(0) and Ni(I) species are obtained. EQCM also provides information about the mechanism of deposition and passivation of nickel as well as the hydrogen evolution.
Analysis of Roman and other archaeological glasses by 12 MeV proton activation analysis
2020
Abstract 14 elements were determined, at trace level, in Roman and other archaeological glasses by 12 MeV proton activation analysis. The results show that the natural glass from Mongolia and Brazilian quartz are the purest of all the samples analysed with detection limits at 1 ppm level for Ti, V, Cr, As, Sr, Y and Zr. In several cut pieces of one variety of Roman glass, using the concentration of Ca, Ti, Fe, Sr and Sb as markers, the homogeneity of glass production and their potential use in provenance studies were discussed.
Design and construction of the fast photon detection system for COMPASS RICH-1
2010
International audience; New photon detectors, based on the use of multi-anode photo-multiplier tubes coupled to individual lens telescopes and read out with a dedicated read-out electronics system, equip the central region of the Cherenkov imaging counter RICH-1 of the COMPASS experiment at CERN SPS. They are characterised by high photon yield, fast response and high rate capability and are successfully in operation since the 2006 COMPASS data taking. The photon detection system fully matches the expected performance. The design and construction of the photon detectors are described in detail.
MODELING OF A TiO2-COATED QUARTZ -WOOL PACKED-BED PHOTOCATALYTIC REACTOR
2010
A fixed-bed, photocatalytic laboratory reactor aimed to degrade pollutants from water streams was designed and built. Quartz wool coated with a thin film of TiO2 was employed as the reactor filling. The photocatalyst was placed in the reactor forming a loose packing to guarantee the intimate contact among reactants, photons, and the photocatalytic surface. This reactor was employed to study the photocatalytic decomposition of a model pollutant (formic acid). A reactor–radiation–reaction model was developed, which was comprised of the reactor mass balance, radiation model, and kinetic model for the degradation of formic acid. The local superficial rate of photon absorption, which was necessa…
Radiation model of a TiO2-coated, quartz wool, packed-bed photocatalytic reactor
2010
The radiation field of a packed-bed photocatalytic reactor filled with quartz wool coated with titanium dioxide was modeled using the Monte Carlo technique and the following information: the radiation flux emitted by the lamps, the diameter size distribution of the quartz fiber cloth, the mass of quartz fibers and of TiO2 that was immobilized on the fiber surface as well as the refractive index and the spectral absorption coefficient of the materials of the system. Modeling predictions were validated with radiometer measurements of the transmitted radiation through the reactor, the root mean square error being < 9.7%. Finally, by means of a parametric study, the validated model was used to …
Growth of passive layers on nickel during their voltammetric anodic dissolution in a weakly acid medium
2006
Abstract Quartz crystal microbalance in combination with voltammetry has been used for studying the electrochemical oxidation behaviour of a nickel deposit in a weakly acid medium. The instantaneous mass/charge ratio (Fdm/dQ) analysis allows to obtain the fraction of charge consumed in the passivation process, and, that way, the experimental kinetic equation of the passive layer growth. This experimental law has been fitted to the theoretical equation derived from the point defect model theory under voltammetric conditions.
Identification of high-affinity phage-displayed VH fragments by use of a quartz crystal microbalance with dissipation monitoring
2021
10 Pág. Departamento de Tecnología de Alimentos
Irreversibility of the pressure-induced phase transition of quartz and the relation between three hypothetical post-quartz phases
2004
Our atomistic computer simulations mainly based on classical force fields suggest that the pressure-induced transition from $\ensuremath{\alpha}$ quartz to quartz II at $21\phantom{\rule{0.3em}{0ex}}\mathrm{GPa}$ is irreversible. While quartz II is ferroelastic in principle, the transition itself is coelastic, as the shape of the newly formed crystal is determined by the handedness of $\ensuremath{\alpha}$-quartz. Upon releasing the pressure, our model quartz II remains stable down to $5\phantom{\rule{0.3em}{0ex}}\mathrm{GPa}$, where it undergoes an isosymmetric transformation into a less dense polymorph. If the classical force field model of quartz II is compressed quickly to $50\phantom{\…