Materials Literature
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After x-ray irradiation at 20 K, an intrinsic O - centre was identified by ESR and ENDOR spectroscopy as the self-trapped hole centre in ZnWO 4 . Observation of one Zn and two strong W superhyperfine interactions allows us to distinguish between two possible trapping sites: the hole resides at the B-type oxygen positi…
Alternate polyelectrolyte multilayers composed of poly(L-lysine) (PLL) in the alpha-helical state and poly(maleic acid-co-alpha-methylstyrene) (PMA-MS) were deposited by consecutively adsorbing from aqueous solutions on both unmodified and unidirectionally scratched silicon substrates. Thereby, the alpha-helical PLL r…
A library of inorganic complexes with reversible redox chemistry and/or the ability to catalyze homogeneous oxidations by peroxides, including but not limited to combinations of polyoxometalate anions and redox-active cations, was constructed. Evaluation of library members for the ability to catalyze aerobic sulfoxida…
The axial reactivity of peripherally octasubstituted soluble silicon(IV) phthalocyanines (SiPcZ 8, Z = OC 5 H 11 or Z = C 5 H 11 ) was studied in order to explore new synthetic routes for preparing axially functionalized SiPc monomers and dimers. Self-exchange of the axial methoxide in methylmethoxy SiPcZ 8 was about…
Chemical modification and blending of polymers in an extruder reactor are discussed. Relationships between the parameters affecting the reaction kinetics, viz., mixing time, duration of a chemical reaction and the residence time of the system in the extruder reactor, and the structure of the materials produced are ana…
Triplet excitation transport occurring in the columnar liquid crystalline phase of a triphenylene derivative at room temperature is studied by transient absorption spectroscopy with nanosecond resolution. The properties of the triplet excitons are evidenced by doping the mesophase with different concentrations of 2,4,…
The kinetics and mechanism of formate synthesis by hydrogenation of CO 2 (CO 2 + 1/2H 2 → HCOO a ) and the formate decomposition into CO 2 and H 2 (HCOO a → CO 2 + 1/2H 2 ) over Cu(111) and Cu(110) surfaces were studied by in-situ infrared reflection−absorption spectroscopy (IRAS) using a high-pressure reactor (∼1 atm…
Microbially prepared polypentapeptides were cross-linked by two chemical methods. In one chemical approach, (GVGIP)(260) where G = glycine, V = valine, I = isoleucine, and P = proline with no functional groups in its side chains, was cross-linked using dicumyl peroxide, and reaction conditions were systematically exam…
The synthesis of silicon nanoclusters and their characterization by multinuclear solid-state nuclear magnetic resonance (NMR) is presented. A combination of 23 Na, 29 Si, and 13 C magic angle spinning with and without cross polarization to 1 H nuclei have been used to investigate the reaction of sodium silicide (NaSi)…
We report the results of {11}B nuclear magnetic resonance (NMR) measurements of SrB_{6} and Ca_{0.995}La_{0.05}B_{6} below room temperature. Although the electrical resistivities of these two materials differ substantially, their {11}B-NMR responses exhibit some strikingly common features. Both materials exhibit ferro…
The results of large-scale simulations investigating the dynamics of magnetization reversal in arrays of single-domain nanomagnets after a rapid reversal of the applied field at nonzero temperature are presented. The numerical micromagnetic approach uses the Landau-Lifshitz-Gilbert equation including contributions fro…
ZnO typifies a class of materials that can be doped via native defects in only one way: either n type or p type. We explain this asymmetry in ZnO via a study of its intrinsic defect physics, including ${\mathrm{Zn}}_{\mathrm{O}},$ ${\mathrm{Zn}}_{i},$ ${\mathrm{V}}_{\mathrm{O}},$ ${\mathrm{O}}_{i},$ and ${V}_{\mathrm{…
Polyvinyl alcohol was treated by different weights of sodium acetylacetonate Na (acac) ranging from 5 to 20% wt/wt. Thin films of pure and treated polyvinyl alcohol were prepared by casting. The structure of pure PVA was affected by the treatment process (to form polymer metal complex) and additional peaks were observ…
Abstract In recent years, a number of new HT/HP reservoirs have been developed in the North Sea. The Shearwater reservoir is a gas condensate producer located in Block 22/30 in the North Sea. This reservoir has very harsh downhole conditions as follows: T ~ 370°F, P > 13,000 psi, brine TDS > 250,000 mg/l…
Abstract When scale problems occur into the tubings, without hardly affecting the well productivity, it can be interesting to find new downhole injection means, representing an alternative to classical squeezes. On some wells of block 3 in Angola, the squeezes turned out difficult because of the reservoir heterogeneit…
Abstract This paper presents the methodology for characterisation (sampling and analysis) of formation water and scale prediction in the waterflooding project of a deep-water field, from Campos Basin, Brazil. A subsea well A, representative from an oil-producing sandstone reservoir of this field was selected for sampl…
We studied the decay of self-trapped excitons (STE's) in ${\mathrm{BaF}}_{2},$ ${\mathrm{SrF}}_{2},$ and ${\mathrm{CaF}}_{2}$ excited at room temperature by two-photon absorption of femtosecond laser pulses by recording time-resolved triplet-luminescence spectra. For ${\mathrm{BaF}}_{2}$ we detected significant spectr…
Abstract Calcium carbonate is a commonly occurring oilfield scale which proves to be difficult to manage. Carbonate scale prediction can be improved by considering the kinetic chemistry in addition to the conventional thermodynamics based predictive techniques. To improve the performance of a predictive model, a thoro…
Abstract Precipitation of mineral scales causes many problems in oil and gas production operations: formation damage, production losses, increased workovers in both producers and injectors, poor injection water quality, and equipment failures due to under-deposit corrosion. The most common mineral scales are sulfate a…
The metallic state in conjugated polymers and single-walled carbon nanotubes is studied by dielectric spectroscopy (8--600 GHz). We have found an intriguing correlation between scattering time $(\ensuremath{\tau})$ and plasma frequency $({\ensuremath{\omega}}_{p}):\ensuremath{\tau}\ensuremath{\propto}{\ensuremath{\ome…