Solid State Reactions - Theoretical and Experimental Aspects
(1984). Solid State Reactions - Theoretical and Experimental Aspects. Drug Development and Industrial Pharmacy: Vol. 10, No. 8-9, pp. 1175-1276.
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A quantum-chemical approach to the generation of solid acidity in composite metal oxides
Various microscopic surface structures of silica–alumina and silica–magnesia which can generate Brønsted acidity are discussed via molecular-orbital calculations using cluster models, together with indices for Brønsted acidity. Mechanisms explaining the origin of the Brønsted acidity of the solid surface are proposed…
Multiple isoelectric and molecular weight variants of choline acetyltransferase. Artifact or real?
The existence of isoelectric variants of bovine brain and human placental choline acetyltransferase was confirmed by chromatofocusing. The identification of molecular weight variants (bovine brain, Mr = 68,000 and 63,000; human placental, Mr = 66,000 and 64,000) was also demonstrated using sodium dodecyl sulfate-polya…
Group III ions in sodium silicate glass. Part. 1. X-Ray Photoelectron spectroscopy study
On presente des donnees de spectroscopie de photoelectrons induits par RX sur des verres de compositions 20Na 2 O-x R 2 O 3 -(80-x)SiO 2 et 20Na 2 O-xTlO-(80-x)SiO 2 (x=0-20 mol.%; R=Ga, In, Sc, Y ou La) 2 . Du thallium et des ions trivalents plus gros, In 3+ , Sc 3+ , Y 3+ et La 3+ sont incorpores dans les verres en…
Quantitative electron probe microanalysis of carbon in binary carbides
Introductory investigations performed in order to make quantitative electron-probe microanalysis of very light elements such as boron, carbon, nitrogen or oxygen possible are described. The practical problems encountered in this kind of work are discussed in detail and, where possible, solutions are proposed. It is sh…
The rhombohedral structure of tricalcium silicate at 1200°C
Crystal structure / Phase transition / Tricalcium silicate Abstract. Crystals of tricalcium silicate having a monoclinic superstructure transformed into a rhombohedral structure when they were heated at 1200 °C with gas flame: a=7.135(6) A, c=25.586(15) A, space group R3m, and contents of 9 x Ca2,9sSio,9sAlo,o40s.The…
Principal Component Analysis of Variation in Stephanodiscus rotula and S. niagarae (Bacillariophyceae)
For valves of the same diameter, type material of Stephanodiscus rotula, observed with light and scanning electron microscopy, has more total spines, more central strutted processes, and narrower mantles than does S. niagarae. However, these characters covary with diameter and with one another within each species. Thu…
Effect of Direction of Approach to Temperature on the Delayed Hydrogen Cracking Behavior of Cold-Worked Zr-2.5Nb
The delayed hydrogen cracking behavior of cold-worked Zr-2.5Nb at temperatures above about 423 K depends upon the direction of approach to test temperature. Cooling to the test temperatures results in an increase in crack growth rate, da/dt, with increase in temperature, given by the following Arrhenius relationship d…
Dielectric study of the liquid crystal compound octylcyanobiphenyl (8CB) using time domain spectroscopy
Time domain spectroscopy (TDS) is introduced for the first time to study the complex permittivity of liquid crystals. Measurements have been carried out for octylcyanobiphenyl (8CB) and the results are compared with literature data obtained by conventional steady-state methods in the frequency domain. It is also shown…
Scale formation on reverse-osmosis membranes.
The mechanism of calcium sulfate dihydrate scale formation on reverse-osmosis membranes was studied by the introduction of a theory of crystallization. According to this theory, the values of the growth rate constant and the waiting period before nucleation obtained in long-term runs were reasonable in comparison with…
Grain-boundary structure
Theoretical and experimental work on the atomic structure of grain boundaries in metals and ionic crystals is reviewed critically. The dislocation and O-lattice models are described and their usefulness is assessed with reference to a worked example. The models derived from computer simulations of the atomic structure…
Incommensurate phase of quartz. - II : Brillouin scattering studies
The recently discovered incommensurate phase of quartz close to the α-β transition has been investigated using Brillouin scattering. The frequency and the damping of the longitudinal (LA) and transverse (TA) acoustic modes propagating along the X, Y and Z directions have been measured as a function of the temperature…
Weak anchoring energy and pretilt of a nematic liquid crystal
We extend the wedge technique of Rivière et al. to measure the pretilt angle Φ and the (weak) anchoring energy of a nematic liquid crystal oriented on a suitably treated glass surface. The liquid crystal is placed in a wedge shaped space formed by the plate to be studied and a « standard » plate giving a strong homeot…
Root-exuded oxygen in the aquatic angiosperm Ruppia maritima
The potential impact of oxygen from roots on the source of inorganic nitrogen for Ruppia maritima L. (Potarnogetonales) was investigated in laboratory experiments. Roots released oxygen at a n average rate of 2 to 3 ~g 0, (mg dry wt)-' h-'. A distinctive oxygenated zone with a radius of 0.75 to 1.25mm developed in the…
Kinoshitalite and Mn phlogopites: Trial refinements in subgroup symmetry and further refinement in ideal symmetry.
The crystal structures of two manganoan 1M-phlogopites and kinoshitalite-1M (Ba, Mn brittle mica) have been re-examined to determine if cation ordering patterns in subgroup symmetries exist. In all cases, the X-ray single crystal data are better explained by the ideal symmetry of C2⁄m, which requires only one tetrahed…
Investigations of glasses in the system PbO—PbF2
Glass formation in the system PbO–PbF2 has been investigated. The structure of these glasses has been studied using X-ray diffraction. Densities, heat capacities, glass-transition and crystallization temperatures and Vicker's microhardnesses have been measured. D.c. conductivities of these glasses have also been measu…
Structural defects of a lamellar lyotropic mesophase : a neutron scattering study
Contrarily to previous expectations, the flat geometry is not the configuration of lowest free energy for the bilayers of SDS in the lamellar phase of SDS/water. Indeed, neutron scattering reveals an unusual pattern of diffuse scattering at small angles, in addition to the regular diffraction spots of a layered mesoph…
Structure des deux phases colonnaires d'un ester de triphénylène chiral
Nous avons étudié la structure des deux mésophases d'une molécule discoïde chirale par diffraction des rayons X et par observation optique. La comparaison des deux techniques nous a permis de déterminer quelques-uns des paramètres de la structure. La transition entre les deux mésophases semble être du type ferroélectr…
Oxidation of phenols by molecular oxygen catalysed by transition metal complexes. Comparison between the activity of various cobalt and manganese complexes and the role of peroxy intermediates
The oxidation reactions of hindered phenols by molecular oxygen catalysed by monomeric and polymeric cobalt–Schiff base complexes, cobalt and manganese porphyrins, and (pyridine)cobaloxime are described; the rate and selectivity of these reactions are very dependent on the catalyst and on the solvent.A new product has…
Spin-state relaxation dynamics in iron( II ) complexes: solvent on the activation and reaction and volumes for the 1 A ⇌ 5 T interconversion
Activation and reaction volumes are reported for the interconversion of the 1A and 5T isomers of FeII complexes in several solvents; the reaction volume ΔV° and the activation volume ΔV15‡ are solvent-dependent but ΔV51‡ for the 5T →1A crossover is markedly negative and virtually solvent-dependent and a transition sta…