Rheology of liquid crystalline polymers
Abstract
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Packing analysis of carbohydrates and polysaccharides. 16. The crystal structures of celluloses IVI and IVII
The crystal structures of cellulose polymorphs IV I and IV II have been determined by X-ray fiber diffraction analysis combined with stereochemical model refinement. Both structures crystallize in a two-chain unit cell of essentially identical parameters. The most probable space group in both cases is P1. The chain co…
Crystal structure of AgTCNQ and contrasting magnetic properties of electrochemically synthesised AgTCNQ and CuTCNQ (7,7,8,8-tetracyanoquinodimethane)
The low resistivity of copper salts of TCNQ and the associated broad e.s.r. signals suggest that the characteristic narrow-band structure of the TCNQ columns may be modified by electronic coupling to metal d bands. Crystalline AgTCNQ and CuTCNQ have been synthesised electrochemically. The crystal structure of AgTCNQ r…
Indentation of Brittle Materials
The use of indentation testing as a method for investigating the deformation and fracture properties of intrinsically brittle materials, glasses, and ceramics is examined. It is argued that the traditional plasticity models of hardness phenomena can be deficient in some important respects, notably in the underlying as…
Liposomes as targetable drug carriers.
The general problem of targeted drug transport is critically reviewed and three principle components of targeted systems are discussed: the target, the vector molecule, and the carrier. Different systems of drug targeting are briefly described: local drug application, chemical modification of the drug molecule, physic…
Tricalcium silicate Ca3O[SiO4]: The monoclinic superstructure
Crystals, free from twinning, of the monoclinic phase of tricalcium silicate exhibiting superstructure reflections have been obtained. Crystal data are: a = 33.083(8), b = 7.027(2), c = 18.499(4) Å, β = 94.12(2)°, Z = 36 × Ca 2.89 Mg 0.11 OSiO 4 , V = 4289 Å 3 . The structure analysis was carried out using 3886 indepe…
Grain‐Growth Kinetics for Alumina in the Absence of a Liquid Phase
The kinetics of grain growth in fully dense Al 2 O 3 with and without MgO solute additions were measured for high‐purity samples containing no liquid phases. The MgO was found to suppress the grain‐boundary migration rate by a factor of 50. Compensating lattice defects are suggested to play a role in grain‐growth inhi…
A very efficient system for alkene epoxidation by hydrogen peroxide: catalysis by manganese-porphyrins in the presence of imidazole
In the presence of imidazole, Mn-(or Fe-) porphyrins catalyse the epoxidation of various alkenes including alk-1-enes by H2O2; with chloromanganese(tetra-2,6-dichlorophenylporphyrin) as a catalyst, alkene conversion by a few equivalents of H2O2 is complete within less than 1 h at 20 °C and epoxide yields are very high…
Anions of the type (RMOH2)3W18P2O689- and [H2OCo]3W18P2O6812-. A reinvestigation of "B,.beta.-W9PO349-"
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTAnions of the type (RMOH2)3W18P2O689- and [H2OCo]3W18P2O6812-. A reinvestigation of "B,.beta.-W9PO349-"W. H. Knoth, P. J. Domaille, and R. D. FarleeCite this: Organometallics 1985, 4, 1, 62–68Publication Date (Print):January 1, 1985Publication History Published online1 May 2…
Tubular mesophases: liquid crystals consisting of macrocyclic molecules
The hexa-(p-n-dodecyloxybenzoyl) derivatives (1b), (2b), and (3b) of the macrocyclic polyamines [18]-N6, [24]-N6O2, and [27]-N6O3 display a liquid crystal phase in which the macrocyclic units are stacked, forming a tubular mesophase.
Bonding-state characterization of the constitutent elements of silicate minerals by X-ray photoelectron spectroscopy
X-ray photoelectron and X-ray-induced Auger electron spectra of silicate minerals have been measured. The systematic shifts of the photoelectron binding energies of Si, O and tetrahedrally coordinated Al ions in the silicate framework suggest that the negative charge on the framework is delocalized over these ions. On…
The genus allium— Part 3
Allium is a genus of some 500 species belonging to the family Liliaceae. However, only a few of these are important as food plants, notably onion, garlic, chive, leek, and rakkyo. Such plants have been used for many centuries for their pungency and flavoring value, for their medicinal properties, and in some parts of…
Soil pH Buffering Revisited
Abstract The buffering relationships of a wide variety of Vermont soils were investigated by adding either acid (H 2 SO 4 ) or base (CaCO 3 ). Soils were found to be very well buffered above pH 7 and below pH 4. When amendment added is expressed on an organic matter (OM) basis [mmol (H + or 1/2 CaCO 3 ) g −1 OM] and t…
Polymorphic Transformation of Some Drugs Under Compression
The existence of various crystalline forms in drugs is a phenomenon frequently encountered (about 40% of the USP XX tablet monographs with dissolution tests are concerned with such compounds). Some studies concerning trituration or grinding of polymorphs have been published; surprisingly little information is availabl…
Materials for nonlinear optics
In this paper we review both photorefractive and nonlinear optical materials for optoelectronic applications. The material requirements for nonlinear optical laser-frequency conversion using the electronic hyperpolarizabilities and optical signal processing using the photorefractive effect will be discussed. Some repr…
Structural studies of calcium aluminosilicate glasses by high resolution solid state 29Si and 27Al magic angle spinning nuclear magnetic resonance
Etude, par spectroscopie RMN de 29 Si et 27 Al dans le systeme CaO-Al 2 O 3 -SiO 2 , d'une serie de 50 verres environ dont les compositions chimiques variaient systematiquement le long de sept lignes selectionnees du diagramme de composition ternaire. Les donnees sont discutees d'apres un modele de structure base sur…
Strength and Fracture Toughness of Isostatically Hot‐Pressed Composites of Al 2 O 3 and Y 2 O 3 ‐Partially‐Stabilized ZrO 2
Composites of Al 2 O 3 and Y 2 O 3 partially‐stabilized ZrO 2 were isostatically hot‐pressed using submicrometer powders as the starting material. The addition of Al 2 O 3 resulted in a large increase in bending strength. The average bending strength for a composite containing 20 wt% Al 2 O 3 was 2400 MPa, and its fra…
Phasmids : a new class of liquid crystals
Two hexa-alkoxy derivatives (7a and 7b) of terephthal-bis-[4-benzoyloxyaniline] are described. They exhibit two new types of mesophase for which the term phasmidic is proposed : one has an hexagonal 2D lattice and the second an oblique 2D lattice.
Controls on the Precipitation of Early Diagenetic Calcite, Dolomite and Siderite Concretions in Complex Depositional Sequences
abstract Carbonate concretions occur commonly in organic-rich clastic sediments of ancient coastal floodplains and deltas. They consist of calcite, dolomite, or siderite or combinations of these. The influence of marine, mixed or non-marine depositional waters is seen in early cements; solute sources from decompositio…
Some recent advances in the mineralogy and geochemistry of Nb and Ta in rare-element granitic pegmatites
On a procédé à l'examen des données existantes sur la composition chimique et les propriétés structurales de columbite-tantalite, ferrotapiolite-manganotapiolite, ixiolite, wodginite, rutile tantalifère et niobifère, cassitérite niobo-tantalifère, et du groupe de pyrochlore. La compréhension de la cristallochimie de c…