Materials Literature
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The influence of anions on the initiation of pitting and the kinetics of pit growth on aluminum alloy Type 7075 has been investigated. The order of reaction ( i.e. , the number of anions per Al surface reaction site) and the energy of activation for pitting initiation have been measured in F − , Cl − , Br − , and I −…
Electron microscope studies of relatively large planar defects having linear dimensions up to some 5 μm, which lie in {100} planes in diamond, and which emit a greenish-yellow cathodoluminescence, are reported. Evidence is presented that such ‘giant’ platelets are of the same species as, and merely much larger example…
An analysis of x-ray scattering from magnetically oriented liquid crystalline solutions of poly-γ-benzyl-L-glutamate (PBLG) in dioxane yields a value for the order parameter S?0.75. At the isotropic–liquid crystal phase transition, the critical order parameter Sc?0.5 appears to agree with predictions of mean-field the…
In contradistinction to all currently available water-soluble contrast media, metrizamide (Amipaque) is not a salt, but a substituted amide and therefore does not dissociate in solution. This unique property results in solutions of high iodine content yet with low osmolality. Metrizamide probably has a lower neurotoxi…
The metallurgical and electronic structure of TiFeH x alloys are probed by 57 Fe Mossbauer effect studies. The results are qualitatively consistent with and support Reilly and Wiswall's conclusions (1974) on the phase diagram. Volume effects and charge flow are both important in the isomer shift.
We study the properties of a Ginzburg-Landau-Wilson Hamiltonian in which an order parameter is associated with each wave vector which points from the origin to one of two rings in reciprocal space. The existence of the order parameter breaks the two-dimensional rotational symmetry about the axis of the rings. The Hami…
In this paper results are given of an electron optical investigation of the cross section of optical single films and multilayers obtained by fracture. Direct observation techniques with scanning microscopy and the surface replica technique with transmission microscopy were used. Scanning microscopy is simple in sampl…
The crystal structure and electronic charge distribution of pyrazine (1,4-diazabenzene) has been determined at 184 K by X-ray methods. The structural results of Wheatley [Acta Cryst. (1957), 10, 182-187] have been confirmed. A clear indication of bonding effects is obtained. Neither positional and thermal parameters n…
The problem of the first- or second-order nature of the nematic-smectic-$A$ phase change is explored. It is found that couplings between various order parameters, especially the first and second translational ones, are important. General Landau theory for coupled orientational and translational order parameters is dev…
The synthesis of a covalent dimer of chlorophyll a which possesses properties strikingly similar to those exhibited by P700 special pair chlorophyll in vivo is described. The covalent dimer is characterized by several spectroscopic techniques. Hydrogen bonding nucleophiles, such as water, primary alcohols, and primary…
Oligocene (approximate age 31-38 m.y. B.P., Berggren, 1972). The lower part of the Oligocene is missing. Using the coccolith and diatom biostratigraphic data, a hiatus must be placed between Samples 26-2 and 26-3. Thus, no further splitting of the Oligocene was done.
It is known that the porphyrin free base (H2P) can be incorporated in an n-octane Shpol'skii matrix. In slowly grown crystals the solute molecules occur in two orientations, which are co-planar and have their N-H … H-N axes at right angles; in the S 1↔S 0 ‘quasi-line’ absorption and fluorescence spectra they can be di…
Abstract The objective of this work was to obtain primary amine groups on the surface of poly(vinyl alcohol) films by means of a reaction with hexamethylene diisocyanate. The reaction was run in such a way as to minimize the internal crosslinking by employing a large excess of hexamethylene diisocyanate in toluene and…
Zusammenfassung Glaukonitglimmer von 10 kretazischen Gesteinen werden mineralogisch und chemisch untersucht. Die von den Glaukonitkòrnern und Glimmern der Kolloidtonfraktion errechneten Strukturformeln der Glaukonitglimmer bestàtigen die Glaukonitglimmer als exakt dioktaedrische Minerale. Die Strukturformeln geben nur…
Abstract Crystals of the squaric acid C 4 H 2 O 4 (H 2 SQ) and C 4 D 2 O 4 (D 2 SQ) exhibit a structural phase transition at T 0H = 370 K and T 0D = 520 K. The phase transition is associated with the ordering of protons, moving above T 0 in the symmetric double well potential of OHO bonds. The statistic of the phase…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTMechanisms of reduction of cobaltic porphyrins with various reducing agentsEverly B. Fleischer and Stephen K. CheungCite this: J. Am. Chem. Soc. 1976, 98, 26, 8381–8387Publication Date (Print):December 1, 1976Publication History Published online1 May 2002Published inissue 1…
Couplings between inter- and intramolecular vibrations have been investigated. In normal-mode calculations a program has been used which allows all possible couplings between molecular and crystal vibrational modes. Several low-frequency molecular modes coupled to lattice vibrations have been isolated. A complete assi…
Abstract Inhaltsübersicht, Die Kristallstruktur von Ag 2 BaSnS 4 ist mit Röntgeneinkristalldaten erstmals bestimmt worden. Die aufgefüllte Tetraedergerüststruktur hat orthorhombische Symmetrie (a = 7,12 7 ; b = 8,11 7 ; c = 6.85 4 Å [1]). Raumgruppe: D 8 2 —I222, Nr. 23. Die kristallchemischen Eigenschaften von Ag + u…
An electron microscope study of copper-bismuth alloys has shown a high incidence of faceting of the grain boundaries. This is not observed in pure copper, suggesting the bismuth has a large effect on the low energy configurations of the boundary plane.
Nuclear magnetic second moment and spin–lattice relaxation time studies have been performed over the temperature range 77–388 K for two ammonium bisulfates; the ferroelectric NH4HSO4 and the antiferroelectric (NH4)3H(SO4)2. The results suggest a rapid general reorientation of the NH4 + ions over the whole temperature…