Materials Literature
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The heat contents of the alkali silicate glasses and crystals have been measured from 25°C to melting temperature with a continuous high-temperature calorimeter.The entropy in the above temperature range is determined for the glasses and crystals of the composition R2O⋅2SiO2 (R=Li, Na, K). The free-energy change is ca…
The quantitative reliability of theoretical expressions for Hall and thermoelectric effects has been tested under thermal equilibrium conditions in high-conductivity, nondegenerate, and degenerate CdS single crystals, and under nonequilibrium steady-state and transient conditions in low-conductivity photosensitive CdS…
The crystal and molecular structure of the title compound have been determined by single-crystal X-ray analysis All non-hydrogen atoms conform to space group P2/c with a= 6·536 ± 0·007, b= 7·768 ± 0·008, c= 17·194 ± 0·017 Å, β= 108·8 ± 0·1°. Z= 2. The structure has been determined from diffractometer data by Patterson…
Les textures en éventails sont très communes entre lame et lamelle, dans les cristaux liquides cholestériques, proches de la transition isotrope. Ces textures renferment un bon nombre de disinclinaisons + π et — π arrangées selon certains motifs aisément reconnaissables. Dans une dislocation-coin, une disinclinaison +…
Interest has recently been shown in the possibility of using amorphous materials such as glasses in electronic switching devices. The theory underlying the operation of these devices is still not fully understood, but some lines of approach have proved promising.
A discussion of how to carry out a direct perturbation expansion for the one-electron Green's function is given using an electron–plasmon model for the conduction electron correlations. A crucial feature of the method is the consistent extraction of energy shifts. Numerical results for the spectral function and the de…
Self-irradiation damage due to alpha particle and recoil atom bombardment has been studied in 238PuO2. In a well-annealed sample, the room temperature damage ingrowth follows a simple exponential function to the saturation damage level. In incompletely annealed samples, the damage ingrowth curve is discontinuous and e…
L-Arginine dihydrate, C6H14N4O2,2H2O, crystallizes in the orthorhombic space group P212121 with a= 5·638(6), b= 11·85(1), c= 15·68(1)Å, and Z= 4. The structure has been refined to R 0·034 (1364 reflections) by neutron diffraction techniques, and all hydrogen atoms located precisely. The arginine molecule is a zwitteri…
The normal modes of vibration propagating along the unique c axis of stretch-oriented polytetrafluoroethylene at −11, 25, and 40°C have been studied by means of coherent neutron inelastic scattering methods. No significant effects associated with the 19 and 30°C phase transitions have been definitely observed. The res…
There has been a marked change in the soil testing procedures used in the United States by state soil testing laboratories since the early 1950's. In the Coastal Plain states of the south and east, the Double Acid extraction procedure is used for P, K, Ca, and Mg determinations. Bray P1 is the most frequently used met…
In a nematic medium, as a result of the anisotropic distribution of the molecules, the average local electric field is of the form E+ γP, where E is the applied field, P the polarization, and γ is a factor which is different for the directions parallel and perpendicular to the optic axis. For the nematic medium, the N…
X-Ray photoelectron spectroscopy has been used to study the oxidation of uranium metal. The results indicate that even at 1073 K in a residual oxygen partial pressure of less than 1 × 10–8 N m–2 the interdiffusion of pure uranium and the surface oxide film is not sufficiently rapid to produce a completely pure uranium…
Investigations of tris- and tetrakis-hexafluoroacetylacetonato- and trifluoroacetylacetonato-terbium(III) complexes have established that the temperature-dependence of the 5D4 lifetime is caused by thermal depopulation of the ion level to a ligand triplet state. Ligand triplet to ground state deactivation rates, A, ha…
Far infrared reflectivity of Sb2S3, Bi2S3 and Sb2Se3 single crystals in the spectral region 25-400 cm-1 and temperature region 100-400°K were measured in polarized light. The reflectivity spectra were subjected to the Kramers-Kronig analysis to obtain dielectric response functions. The far infrared dispersion is of a…
Salts of the heteropolyanions PCoIIW11O40H25–, AsCoIIW11O40H25–, BCoIIW11O40H27–, BCoIIIW11O40H26–, and PZnW11O40H25– have been prepared. In the case of the first four and of PNiIIW11O40H25– there is spectroscopic evidence that the constitutional water is present as an actual water molecule and is replaceable by, e.g.…
M\"ossbauer absorption spectra have been observed for ${\mathrm{Fe}}_{2}$B from 290 to 1175 \ifmmode^\circ\else\textdegree\fi{}K. A change in the electric quadrupole interaction was observed from 460 to 480 \ifmmode^\circ\else\textdegree\fi{}K and interpreted as a result of the rotation of the easy axis of magnetizati…
Magnetization and magnetic torque measurements were made on single crystals of ErFe2 from 77°K to 329°K. From these measurements the magnetocrystalline anisotropy constants were deduced. At room temperature K1 = −3.3 × 106 ergs/cm3; at 77°K, −K1 > 108 ergs/cm3. Huge magnetic anisotropies are predicted for TbFe2 and Dy…
-We study the hydrodynamic motion induced by the rotation of the molecular axis in a nematic liquid crystal (backflow). This effect can reduce strongly some effective viscosity coefficients.
A dynamic TGA method was used to study the effect of the molecular weight of well-defined polystyrene samples as well as the effect of heating rate and sample weight on the kinetic parameters of the thermal decomposition. It is shown that the maximum rate, the average specific rate, and the activation energy of the de…
Abstract Temperature dependent infrared studies have been carried out on three series of poly‐urethanes previously synthesized and characterized. The repeat units of the three series may be schematically represented as follows: magnified image In each case n varies from 2 to 10. The H and DP series are partially cryst…