Materials Literature
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A quasi-isothermal method of operating an absorbed-dose graphite calorimeter is described in theory and practice. In contrast with the well-known quasi-adiabatic operation, which entails temperature increases during measurements, in the quasi-isothermal mode the temperatures of the different graphite bodies remain con…
A brief general description of differential scanning calorimetry is followed by a more detailed treatment of the quantitative aspects of three applications that have widespread usage in the polymer industry: (1) the glass transition; (2) heats of reaction (curing); and (3) crystallinity. Emphasis is placed on the true…
The template condensation of 2,6-pyridinedicarbaldehyde with ethylenediamine in the presence of Sm(NO3)3 gave a complex formulated as [Sm(C18H20N6O)(NO3)3]. The complex was recrystallised from water and the X-ray crystal structure determined by the heavy-atom method and refined by least squares to a final R value of 0…
Abstract Some features of the crystal structure of Cu(II) oxalate, which are relevant for the interpretation of unusual magnetic properties of the substance, are discussed. EXAFS and X‐ray powder diffraction results described by different authors are compared. The results of both the analytical methods complement each…
The synthesis and characterisation of some asymmetrical meso-substituted porphyrins, for studies in solar energy conversion, are described. Isomeric porphyrins (5) and (6) could be cleanly separated and distinguished by the number of 13C n.m.r. resonances for the pyrrole α-carbon atoms. Similarly, 13C and 1H n.m.r. sp…
The magnetic behavior of ${\mathrm{Y}}_{6}$${\mathrm{Mn}}_{23}$ is dramatically altered upon hydrogenation (or deuteration). In this study it has been found, by means of high-resolution powder diffraction and Rietveld refinement techniques, that the crystallographic structure is distorted from face-centered cubic ($\m…
Abstract
π-Radical cations of water-soluble zinc porphyrins have been formed by oxidation with Br˙–2 under pulse-radiolytic conditions. These π-radical cations decay with complex kinetics but the rate of decay was enhanced upon addition of colloidal RuO2·2H2O. For the π-radical cation derived from zinc tetrakis(4-sulphonatophe…
We report a study of the viscoelastic and elastic properties of a nematic liquid crystal as measured by static and dynamic light scattering. Experimental values are reported for the splay/twist/bend elastic and viscoelastic ratio as well as for the Mięsowicz viscosity ratio η1/η3 of APAPA in the nematic region as a fu…
Une néphéline de composition (□0.04K0.48Na0.48)Na3[Al0.99Si1.01O4]4 a été synthétisée à partir d'un mélange d'oxydes dans NaF fondu à 1 000 °C/1 jour. Pour mesurer les intensités avec un diffractomètre X automatique à monocristal, on a choisi un fragment cristallin présentant un rapport I(230):I(320) minimum. Après co…
We have studied the cholesterization of discotic and calamitic lyotropic ferronematics by addition of brucine sulphate. The techniques used are optical microscopy for the textures and X-ray diffraction for the structures. The results concerning the pitch and the rotatory power of oriented samples containing or not fer…
The first monoarene complexes of gallium(I) were obtained by reaction of Ga2X4 (X = Cl, Br), suspended in toluene, with hexamethylbenzene. In 1b, C-1 and C-4 of the arena ligand are shifted towards the GaI; 1b can thus be regarded both as a π-complex as well as nido-cluster.
The previous X-ray-crystallographic determination of the relative configuration of P-1894B, a potent prolyl hydroxylase inhibitor isolated from the culture broth of Streptomyces albogriseolus, was extended by means of chemical and spectral studies. The absolute configuration of P-1894B (1) was established from the abs…
Indium-tin-oxide single crystals with 0–9 atomic% of Sn/In are produced by flux method, and their electrical properties are measured. At about 2 atomic% of Sn/In, the resistivity is 2×10 -4 Ω-cm and the electron concentration is 3×10 20 /cm 3 at room temperature. Further increase of Sn/In ratio does not change the ele…
Feldspars.- 1. Average Structures of Alkali and Plagioclase Feldspars : Systematics and Applications.- 2. Phase Relations of Plagioclase Feldspars.- 3. The Modulated Structure of the Intermediate Plagioclases and Its Change with Composition.- 4. Spectroscopy of Feldspars.- 5. Thermal Expansion of Alkali Feldspars.- 6.…
Ni/SiO2 catalysts prepared by impregnation and deposition–precipitation have been subjected to cyclic treatments in hydrogen at 500 °C and oxygen at 450 °C to test their resistance to sintering. The activity of the catalysts in benzene hydrogenation was tested after each cycle. The resulting behaviour was found to dep…
A simple test procedure to differentiate between sources of pregelatinized starch NF has been developed. The procedure is based on the swelling characteristics of the materials. Three pregelatinized starch NF products were distinguished by observing their sedimentation volumes. Microscopic differences in the particle…
The Bruggeman optical effective medium theory of the dielectric permeability ε e(ω) of inhomogeneous media is analysed for metal-dielectric compounds in relation to the non metal-metal transition. The influence of the constituent-material parameters (free-electron parameters and bound-state polarization) on both the r…
The vibration spectra of a cylindrical sample of colloidal crystals are studied We indicate the proper choice of the aspect ratio α = R/H which optimizes the quality of resonances. A new experimental set-up allows us to compare the theory with the experimental results and to deduce a precise value of the elastic modul…
Abstract not Available.