Materials Literature
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The sedimentation coefficient for the Kratky—Porod wormlike coil is calculated with the effects of excluded volume taken into account. The statistical length of native DNA is found to be 900 Å. The hydrodynamic diameter of the Watson—Crick helix is 26–27 Å. Sedimentation coefficients are calculated to decrease by abou…
Optical absorption and electron spin resonance (ESR) spectra of a chromium-doped phosphate glass have been studied as a function of Cr2O3 concentration. While the optical spectrum appears to be independent of chromium-ion density, the ESR spectrum exhibits a pronounced concentration dependence. The spectra have been a…
Volumetric and thermal measurements on its undercooled liquid indicate that o-terphenyl undergoes a glass transition in the vicinity of −30°C. This glass temperature is about 60°C higher than that predicted by correlations applicable to simple molecular glass formers. The viscosity of the undercooled liquid was measur…
Detailed studies have been made of the emission and associated excitation and absorption spectra of x-irradiated LiF. By studies of changes in the spectra during periods in the dark and during subsequent reirradiation, and by use of the Mollwo-Ivey relationships, it has been possible to identify optical bands associat…
Measurements of density, optical absorption, resistivity, photoconductivity, and Hall effect have been made on amorphous Ge films ranging in thickness from 1 to 23 \ensuremath{\mu}. The density was found to be 3.9\ifmmode\pm\else\textpm\fi{}0.4g/${\mathrm{cm}}^{3}$. The absorption coefficient (measured at room tempera…
A luminescence system with no-phonon lines at 5.251 and 5.261 eV (at 100\ifmmode^\circ\else\textdegree\fi{}K), observed in the edge luminescence spectra of natural diamonds containing relatively low concentrations of nitrogen in "platelet" form, has been identified with the so-called $N9$ center which is responsible f…
A high-resolution survey of the 0.30-0.37-eV spectra, attributed to transitions at acceptor centers, obtained from several natural $p$-type semiconducting diamonds at 80\ifmmode^\circ\else\textdegree\fi{}K, is presented. Effects on the spectrum of destruction of the normal site symmetry (${T}_{d}$) by uniaxial compres…
Magnetic-susceptibility measurements of the Magn\'eli phases of the Ti-O system show a change from weak covalent bond formation, through antiferromagnetic to paramagnetic-like behavior with increasing oxygen concentration. The reciprocal molar susceptibility plotted versus temperature indicates collective electron eff…
The far infrared reflectivity of KTa${\mathrm{O}}_{3}$ has been studied as a function of temperature from 12 to 463\ifmmode^\circ\else\textdegree\fi{}K. The results have been analyzed by means of a Kramers-Kronig method, and indicate a "soft" mode, lowering its frequency as the temperature is lowered towards the "Curi…
The lattice parameters of KN${\mathrm{O}}_{3}$ were measured in the temperature region of the ferroelectric transition. The changes in the lattice parameters as the crystal undergoes the paraelectric-to-ferroelectric transition have been interpreted as being due to the electrostriction effect. The dielectric constants…
An approximate dispersion curve for the optical branch of the lattice vibration is used to estimate the spin-lattice relaxation time attributed to optical phonons. The relaxation rate is found to be ${{T}_{1}}^{\ensuremath{-}1}\ensuremath{\propto}\mathrm{exp}(\ensuremath{-}\frac{\ensuremath{\hbar}{\ensuremath{\omega}}…
The atom-beam recoil technique has been used to measure absolute total cross sections for the scattering of electrons by atomic and molecular oxygen at 22 energies between 0.5 and 11.3 eV, with additional data obtained up to 100 eV. In this method, a modulated electron beam cross-fires an atom beam, whose attenuation…
The performance characteristics of nonwoven fabrics have been studied as a function of fiber properties, binder properties, and web construction. The particular type of non-woven selected for study was a web of random-laid base fibers in which randomly placed thermoplastic fibers provide the bonds. The responses studi…
Abstract Transmission and diffraction electron micrographs were made of illite and montmorillonite to study the changes that take place as the clays were heated continuously to 1200°C. In both of the clay minerals studied, expulsion of a highly fluid material occurred subsequent to dehydroxylation and prior to the dev…
The self-diffusion coefficient of the lithium ion in cubic lithium sulphate has been measured from 640 to 790°C. From electrical conductivity and electromigration experiments it has been found that several cations are moving in phase and the mean value of the number of ions in each group has been estimated to be about…
"A Modified Formula for Differential Exposure Albedo for Gamma Rays Reflected from Concrete*." Nuclear Science and Engineering, 27(2), pp. 481–482
Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Twitter Facebook Reddit LinkedIn Tools Icon Tools Reprints and Permissions Cite Icon Cite Search Site Citation J. R. Barrett, G. C. Gerhard; Negative Photoconductivity in Gold‐Doped Silicon. Journal of Applie…
The properties of the fcc to hcp transformation in cobalt single-crystal whiskers have been determined. Studies of the crystallographic properties and dislocation structure using optical, standard x-ray diffraction, and high-resolution x-ray diffraction topographic techniques are herein reported. It is shown that the…
The mean-square atomic displacements (u~,) and (u~ z ) are calculated in the range 0-600K from thermodynamic and inelastic neutron-scattering data. Thermodynamic data alone give (2u~ + z u~), which is separated into its components 2(u~) and (u~) with the aid of the lattice-dynamical model of DeWames, Wolfram & Lehman…
The elastic modulus and internal friction of stoichiometric uranium oxide at room temperature were studied using a dynamic method. The elastic modulus of stoichiometric urania at room temperature increases with increasing density. When the volume fraction porosity is less than 0.1, either linear or exponential equatio…