Materials Literature
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Abstract Nylon 66 films exhibiting form I melting behavior show the γ mechanical relaxation at −140°C. Samples which have form II melting behavior do not show this relaxation. The γ relaxation disappears when material having form I behavior is converted to material having form II behavior by annealing or by cold drawi…
A theory of the macroscopic twist which is a characteristic feature of the cholesteric liquid crystal phase is proposed. This is based on the presence of anharmonicity in the forces resisting the relative twist of neighboring planes of molecules and views the macroscopic twist as the rotational analog of thermal expan…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTCrystal structure of Na2O.MgO.5Al2O3 [sodium oxide-magnesia-alumina] with reference to Na2O.5Al2O3 and other isotypal compoundsMax Bettman and Charles Richard PetersCite this: J. Phys. Chem. 1969, 73, 6, 1774–1780Publication Date (Print):June 1, 1969Publication History Publi…
A number of well-characterized silicate minerals and metal oxides have been analysed by the electron-probe technique in two different instruments with a range of accelerating potentials. Simple oxides and minerals have been used as standards for the elements Na to Ca and pure metals for the elements Ti to Ni. Factors…
Negative magneto-resistance is observed in poorly graphitized carbons at liquid nitrogen temperature or even higher. This peculiar phenomenon has been studied on pyrolytic graphite, as a model material. It is concluded that the negative magneto-resistance is a quantum phenomenon caused by a change of the carrier conce…
Measurements of the electrocaloric effect from 78 to 130 K were made on crystalline KH2PO4and are discussed in terms of the phenomenological theory of Devonshire and others. The predicted quadratic dependence of the electrocaloric effect upon applied field (and polarization) in the paraelectric phase was shown to occu…
Abstract Many derivatives of 1,3,3-trimethylspiro[indoline-2,2′-benzopyran] (1) exhibit photoreversible color changes in organic solvents. One of the derivatives 1,3,3-trimethylspiro[indoline-2,2′-benzopyran]-8′-carboxylic acid (2) shows “reverse photochromism” in polar solvents. The compound 2 exhibits a deep color i…
From a consideration of pit formation chemistry, equations have been derived that correspond to empirical equations developed by the NBS corrosion group. The theoretical equations' derivations show how soil resistivity and pH affect corrosion rates.
The mechanical properties, dislocation configurations and densities have been investigated in single crystals of copper deformed in the strain-rate range 10−4 to 104 sec−1. It was found that the flow stress of copper exhibits two regions of strain-rate sensitivity. Below strain rates of 103 sec−1 the flow stress was r…
The relative contributions of the dicarboxylic acid and the tricarboxylic acid cycles to the oxidative catabolism of glyoxylate in Escherichia coli K-12 were deduced by analysis of mutant strains that were blocked in the formation of glyoxylate carboligase and of malate synthase G (the "glycolate form" of malate synth…
Molecules or ions of the form BOx−n lack a center of symmetry whenever the B atom has a nonbonded pair of electrons. The problem of generating an acentric crystal can be approached by using these acentric oxygen polyhedrons as building blocks. A very high incidence of acentricity is found in compounds based on distort…
We describe continuum theory now being used to describe macroscopic behavior of liquid crystals of nematic type. Two types of predictions are discussed. The first concerns the propagation of orientation waves. The second area is viseometry, including effects of simple electromagnetic fields. We discuss some unusual si…
Cotton linters were swollen to an increasing extent by means of phosphoric acid of increasing concentration. Using a number of simple sugars plus a series of dextran molecules ranging in M.W. from 180 to 2.4 X 10 7 and diameter from 8 to 1600 A. it was possible to measure the pore volume and calculate the surface area…
new electro-optic effect based on guest-host interactions in nematic liquid crystals is described. The cooperative alignment of a nematic liquid crystal in an electric field is used to orient “guest” pleochroic dye molecules (molecules whose absorption spectrum is a function of the molecular orientation with respect t…
The effects of electric fields on the molecular alignment in the liquid crystal p-(anisalamino)-phenyl acetate are discussed. The behavior of this material is similar to that of p-azoxyanisole in that the ordering which is normally observed shows an alignment with the molecular axis preferring a direction parallel to…
A procedure was developed for the determination of the locations of shoulders and singularities of polycrystalline nuclear magnetic resonance (NMR) powder patterns in the presence of both nuclear quadrupole and anisotropic magnetic shift interactions. This determination was performed for both the satellites and the ce…
The elastomers investigated are cross-linked partly by primary and partly by secondary valencies, i.e., by allophanate, biuret, and cyanurate bonds, on the one hand, and by hydrogen bridges and other intermoiecular interactions, on the other. The so-called physical cross-linking effected by secondary valencies is asso…
Some models for the molecular structures of liquid crystals including a ferroelectric liquid are discussed. It is shown that a smectic liquid with a layered structure, in which the preferred orientation of the molecular axis is inclined against the layers, has some similarities with a nematic liquid. Such a tilted sme…
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