Materials Literature
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The tensor of elastic constants of MnAs in the ferromagnetic and paramagnetic states is evaluated from bending vibrations of straight and helical MnAs whiskers. The isotropic compressibility, predicted by the Bean-Rodbell model to be 4.6 × 10−12 dyn−1 cm2 and the same in both phases, is found experimentally to be (4.3…
The far infrared spectra of crystalline polytetrafluoroethylene has been obtained at temperatures above and below the 19°C phase transition. These measurements have shown, for the first time, the appearance of four lattice modes below 19°C at 42, 46, 55, and 84 cm−1. Upon cooling the lines become more intense and shif…
The lattice thermal conductivity between 1.7 and 270 K is reported for single crystals of mercury selenide having conduction electron concentrations from 2.1\ifmmode\times\else\texttimes\fi{}${10}^{17}$ to 6.7\ifmmode\times\else\texttimes\fi{}${10}^{18}$ ${\mathrm{cm}}^{\ensuremath{-}3}$. The most striking feature of…
Lattice vibrations of the hexagonal graphite crystal are analyzed using two-body carbon-carbon interaction potentials. The potential parameters are obtained from estimates of the long-wavelength frequencies of graphite and a knowledge of the nitrogen-nitrogen potential parameters. The dispersion relations along high-s…
The deformation potentials and $g$ values of the ground state of the boron acceptor in silicon have been determined from a study of the stress and Zeeman splitting of the electronic Raman scattering in this material. The stress splitting of the Raman line results from a twofold splitting of the ${\ensuremath{\Gamma}}_…
Stretching modes of several uranium oxide species vaporized from tungsten and iridium Knudsen cells and deposited in argon and krypton matrices have been observed in the 700–-900 cm−1 region of the infrared. Studies of the spectra as a function of temperature and composition of the condensed urania together with norma…
Experiment, plus critical discussion of previous work, suggests the following. Conductivity is primarily due to the migration of L defects (proton vacancies), the enthalpy for L-defect mobility being 0.53 eV in KDP and 0.46 eV in ADP. Such L defects are produced by impurities, but there is an additional tendency towar…
A study has been made to determine the nature of the acceptor center in laboratory-grown semiconducting diamonds. Analyses for nitrogen, aluminum, boron, and uncompensated-acceptor content of aluminum and boron-doped crystals have shown that (i) the aluminum content of inclusion-free crystals is very low, (ii) there i…
A mechanism is proposed for the observed mechanical instability of monodomain smectic A and cholesteric liquid crystals subjected to uniaxial dilative stress. The threshold conditions for the instability are derived, and the possible roles of dislocations in controlling the instability and in producing large plastic d…
1. The enzymes beta-ketothiolase, acetoacetyl-CoA reductase, acetoacetate-succinate CoA-transferase (;thiophorase') and d(-)-3-hydroxybutyrate dehydrogenase have been partially purified from crude extracts of glucose-grown nitrogen-fixing batch cultures of Azotobacter beijerinckii. The condensation of acetyl-CoA to ac…
Generally contracted Gaussian basis functions are defined as those for which each contracted function may have a nonzero contribution from each primitive Gaussian. Alternatives for choice of such bases are tested and guidelines proposed. The basis is compared with standard methods in current use and is shown to be sup…
A general theory of stochastic transport in disordered systems has been developed. The theory is based on a generalization of the Montroll-Weiss continuous-time random walk (CTRW) on a lattice. Starting from a general mobility formalism, specialized $\stackrel{\mathrm{\ifmmode\acute\else\textasciiacute\fi{}}}{\mathrm{…
The formation of collagen cross-links is attributable to the presence of two aldehyde-containing amino acids which react with other amino acids in collagen to generate difunctional, trifunctional, and tetrafunctional cross-links. A necessary prerequisite for the development of these cross-links is that the collagen mo…
For pt. I see abstr. A37362 of 1971. In an interacting spin-phonon system, coherences in the phonon scattering from different ions lead to coupled spin-phonon modes and the thermal resistance arises from the finite lifetime of the coupled excitations. The phonon Green function is derived here by means of a diagrammati…
We have studied the nonlinear optical absorption in silicon at 1.06 \ensuremath{\mu}m using picosecond pulses. By measuring the time dependence of the induced absorption we are able to separate the effects of indirect simultaneous two-photon absorption and stepwise absorption processes. Values of the two-photon absorp…
Abstract Beim Abkühlen einer Schmelze aus Polybuten‐1 kristallisiert zunächst die tetragonale Modifikation II aus. Die Modifikation II ist instabil und wandelt sich langsam in die stabile hexagonale Kristallform I um. Unter dem Einfluß mechanischer Spannungen kann die Umwandlungsgeschwindigkeit II nach I beträchtlich…
Abstract Die Struktur und Eigenschaften verschiedener PVF‐ und PVF 2 ‐Handels‐ und Versuchsprodukte wurden unter anderem durch NMR‐Spektroskopie, Gelchromatographie (GPC), Röntgenbeugung, Differentialthermoanalyse (DTA) und Torsionsschwingungsmessung untersucht. Durch 19 F‐Resonanzmessung konnte gezeigt werden, daß be…
Abstract A series of polysulfone/poly(dimethylsiloxane) (AB) n block copolymers have been synthesized over a wide composition range by varying the molecular weights of the polysulfone and poly(dimethylsiloxane) blocks. The properties vary from a rigid material at high polysulfone content (>65% polysulfone) to an el…
Abstract This paper reviews several types of thermoplastic polyurethane elastomers, and the unique properties these polymers have. In discussing the hydrolysis stability of thermoplastic polyurethane elastomers the suitability of these polymers for such study was pointed out. A relationship between poly(ester‐urethane…
Abstract Die Verzunderungsgeschwindigkeit wird durch den Transport des oxidierendes Gases zur Feststoffoberfläche bestimmt. Dieser Stofftransport kann mit Hilfe der für strömende Medien geltenden Übergangsgesetze beschrieben werden, So daß es möglich ist, ein mathematisches Modell der Verzunderung in Abhängigkeit von…