Materials Literature
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In sonochemical processes, the physical and chemical effects are attributed to the phenomenon of cavitation, which is the formation, growth, and collapse of the cavities termed as activity of cavities. Energy analysis of a single cavity has been considered in order to explain, qualitatively, the effects of acoustic pa…
ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTSpeciation and Thermal Transformation in Alumina Sols: Structures of the Polyhydroxyoxoaluminum Cluster [Al30O8(OH)56(H2O)26]18+ and Its δ-Keggin MoietéJ. Rowsell and L. F. NazarView Author Information Department of Chemistry, University of Waterloo Waterloo, Ontario,…
Multilayer mirrors that maintain or increase their reflectivity with increasing incidence angle can be constructed using polymers that exhibit large birefringence in their indices of refraction. The most important feature of these multilayer interference stacks is the index difference in the thickness direction (z axi…
The crystal structure of Ba 3 Co 2 O 6 (CO 3 ) 0.60 has been determined by means of X-ray, neutron and electron diffraction, and high-resolution electron microscopy. This compound has a hexagonal symmetry (space group P 6̄) and lattice parameters a = 0.9683(1) and c = 0.95180(8) nm related to the 2H−ABO 3 by means of…
The symmetry of CaFe x Ti 1- x O 3- x /2 perovskites (0 x 0.40) has been studied by means of room temperature and high temperature x-ray powder diffraction. At room temperature the perovskites undergo at least two displacive phase transitions with increasing Fe content: from the CaTiO 3 Pbnm structure to the tetragona…
The synthesis and isolation of unsymmetrical porphyrazines bearing two, four, and six bis-(dimethylamino) functionalities has been achieved via the base-catalyzed cross-condensation of 1,2-dicyanobenzene 8 and bis(dimethylamino)maleonitrile 7. In addition, the benzo-fused hexaaminoporphyrazine dimer 10 was prepared fr…
Sodium dodecyl sulfate (SDS)-templated sol−gel films formed by the rapid dip-coating method possess highly ordered lamellar phase structure. Thin film morphology allows both the chemistry and the dynamics of the assembly process to be traced in real time because the steps involved in the formation of the mesostructure…
Microcalorimetric and infrared spectroscopic studies of CO adsorption on Pt/SiO 2 were conducted at temperatures from 298 to 673 K. The adsorption of CO on silica-supported Pt is equilibrated at 673 K, and the microcalorimetric and spectroscopic results obtained at this elevated temperature are in agreement with resul…
The structural properties and the band structures of the charge-transfer insulating oxides SrO, MgO and SrTiO 3 are computed both within density functional theory in the local density approximation (LDA) and in Hedin's GW -scheme for self-energy corrections, by using a model dielectric function, which approximately in…
The equations of state at room temperature as well as the energies of crystal structures up to pressures exceeding 100 GPa are calculated for Na and K . It is shown that the allowance for generalized gradient corrections (GGA) in the density functional method provides a precision description of the equation of state f…
We have studied polariton spin dynamics in a GaAs/AlGaAs microcavity by means of polarization- and time-resolved photoluminescence spectroscopy as a function of excitation density and normal mode splitting. The experiments reveal a novel behavior of the degree of polarization of the emission, namely the existence of a…
[formula: see text] A novel, metal-free oxidation system for the catalytic synthesis of aldehydes and ketones--TEMPO/Oxone--has been developed. An optimized reaction protocol proved especially successful for the synthesis of ketones. Additionally, the influence of quarternary ammonium salts on the catalysis was studie…
The redox behavior of Cu/ZSM-5 zeolites prepared by ion exchange from Cu 2+ aqueous solutions has been followed by a variety of spectroscopic techniques to provide a thorough picture of the so-called “self-reduction” of cupric ions, which occurs upon dehydration of the hydrated system at various temperatures, and of t…
We have examined the properties of polypyrrole (PPy) as a model electroactive membrane which can simultaneously serve as a medium sensing, and bioactive molecule releasing, material using optical spectroscopic, potentiometric, and conductometric methods. In particular, PPy membranes can sense hydrazine in aqueous solu…
Descriptions of phase separation in condensed matter have so far been classified into a solid model (model B) and a fluid model (model H). In the former the diffusion is the only transport process, while in the latter material can be transported by both diffusion and hydrodynamic flow. It has recently been found that…
The neutral trinuclear carboxylato-bridged iron(II) complex [Fe3(O2CCH3)3(BPG)3] can, after minor structural rearrangement, bind a fourth iron(II) ion, forming the tetranuclear complex [Fe4(O2CCH3)3(BPG)3](ClO4)2. The triiron(II) complex can thus be considered as a metallacrown host for the fourth iron(II) ion.
Static and dynamic light-scattering experiments on a nematic side-group polymer are described. Using two different scattering geometries, the depolarized scattering due to thermally excited fluctuations of the nematic director was analyzed. The relaxation rates and strengths show the q dependence known from low molar…
To investigate the linkage between enzyme conformation and catalysis, we have determined the effects of temperature on catalytic properties of the tryptophan synthase alpha(2)beta(2) complex and beta(2) subunit in the absence or presence of different monovalent cations (Cs(+), Na(+), and GuH(+)) and of an allosteric l…
Materials belonging to the Ti 1 - x Ru x O 2 system, where 0 ≤ x ≤ 1 (mol), have been synthesized by a polymeric sol−gel route and calcined in air at 1300 °C by rapid firing. The crystalline evolution of the prepared materials has been investigated, as a function of temperature, by means of differential thermal analys…
Blends of bacterial poly(hydroxybutyrate) (PHB) with poly(hydroxyoctanoate) (PHO) were prepared by co-dissolving the two polyesters in chloroform and casting the mixture. To probe the question of blend miscibility, scanning electron microscopy (SEM) observations and differential scanning calorimetry (DSC) spectra were…