Materials Literature
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Abstract Amorphous silk fibroin with random coil conformation shows endothermic and exothermic peaks and endothermic shift on the DSC (differential scanning calorimetry) curve. The endothermic shift observed at 175°C was due to the glass transition. The exothermic peak at 212°C is recognized to be the crystallization,…
The Bragg condition λ = 2d sin θ is presented as a necessary condition for perfect (100%) blazing of infinite, perfectly conducting diffraction gratings that produce only a single diffracted order, n = −1. As an illustration, the rectangular-profile grating is analyzed. Design blaze curves, showing the required depth…
A model for the conduction mechanism in polymer insulating materials based on a classical concept is described; the application may possibly be extended beyond polymers. By means of this model, a formula expressing the field dependence of conductivity is derived. The values given by this formula have been checked agai…
Abstract XPS techniques were used to clarify the state of supported cobalt catalysts. In order to characterize Co2+ and Co3+, the spin-orbit splitting of the 2p level, which is considered to be affected by the exchange interaction between the unpaired 3d electrons and 2p electrons, was found to be very useful. The int…
Reflection behavior is examined for an interface having periodic height variation. Upon employing the Bloch theorem, in conjunction with the extended boundary condition, exact matrix equations are obtained for surface fields, as well as transmitted and reflected wave amplitudes. Tunneling considerations then lead to n…
The program comprises a main program for inspection and correction of the intensity data, and a number of subroutines covering specific operations. These subroutines can be called upon in any desired sequence.
Abstract The synthesis of six unsymmetrically substituted tetraarylporphyrins is reported. The compounds prepared are 5‐(R),10,15,20‐tritolylporphyrins, where R = 2‐pyridyl, 3‐pyridyl, 4‐acet‐amido, and 2,3 or 4‐hydroxyphenyl. Four new tetrasubstituted tetraarylporphyrins (5,10,15,20‐tetra‐(R)‐porphyrin) are also repo…
The internal friction and dynamic modulus of W single crystals were measured after neutron irradiation near liquid-helium temperature. The results on dislocation pinning and the associated relaxation peaks suggest that in W the $〈110〉$ split interstitials perform a free migration at \ensuremath{\sim} 15 K (substage ${…
Abstract The infrared and photoelectron spectra of some substituted acetylacetones have been measured, and interpreted in terms of enolic and ketonic structures. Ionization potentials from specific orbitals have been assigned. With different substituents, the proportion of the two forms varies considerably. From measu…
X-ray photoemission spectra of W core levels in metallic sodium tungsten bronzes, ${\mathrm{Na}}_{x}\mathrm{W}{\mathrm{O}}_{3}$, clearly show asymmetries due to many-body effects. Na and O core levels show only the expected plasmon satellite, demonstrating the importance of the local density of states in the screening…
Neutron-scattering studies of $2H$-Nb${\mathrm{Se}}_{2}$ and $2H$-Ta${\mathrm{Se}}_{2}$ reveal the strong Kohn anomalies and incommensurate superlattice characteristic of charge-density-wave instabilities. Whereas the Nb${\mathrm{Se}}_{2}$ superlattice (${T}_{0}=33.5$ K) remains incommensurate to 5 K, Ta${\mathrm{Se}}…
Normal modes of vibration in vitreous SiO 2 , GeO 2 and BeF 2 are discussed from the point of view of the relative phase of motion of neighbouring atoms in the system. The notion of a phase quotient is introduced, as a criterion for determining the extent to which modes are acoustic or optical in character. Use of the…
The elastic properties of the four scheelite structure crystals CaMoO 4 , SrMoO 4 , PbMoO 4 and CaWO 4 are compared. Attention is given to the orientation dependence of the elastic behaviour and to how this is related to the atomic arrangement. With respect to the conventional definition of the XYZ axial set employed…
The lineshape of the A band in KBr:In+ and KCl:In+ has been measured as a function of temperature from about 16K to room temperature. The shape of the A band is well accounted for at low temperatures by a model that allows for spin-orbit coupling, vibrational coupling of the mod A), mod B) and mod C) states, and the d…
The atom positions in antiferromagnetic and ferroelectric BiFeO 3 have been obtained by profile analysis of powder neutron diffraction data collected ant 4.2K and 293K. The sublattice magnetization also determined at 4.2K, has been used to obtain a covalency parameter sum, A sigma 2 +2A pi 2 +A s 2 =13.4+or-0.5%. An e…
Sm–Co alloys close to the composition SmCo5 were investigated by metallographic, thermomagnetic, and X-ray diffraction methods. The effect due to evaporation losses of Sm on the equilibrium state of the Sm–Co alloys was studied. The results obtained do not support the suggestion of many workers for a unique stability…
A method for measuring and interpreting the Seebeck coefficient in high resistivity (≧ 105 Ωcm) materials is discussed; the technique is applied to pure V2O3 between 50 and 300 K. The results indicate that the low temperature phase of V2O3 is a band-type semiconductor.
The elastic moduli of a number of semiconducting phosphate glasses have been measured by ultrasonic techniques at 12 MHz. The dependence of elastic stiffness on glass composition is given for glasses of the MoO3–P2O5 and V2O5–P2O5 systems. The Debye temperatures of the phosphate glasses are in the range 300 to 450 K.
A model is developed for the green-yellow emitting centre in PbMoO4 and PbWO4 in terms of an excited state which can be visualized as Pb3+-XO3−4, i.e. an electron localized at XO and an electron-hole at one of the surrounding Pb2+ ions. The different levels of the triplet excited state arise from splitting due to the…
Ultraviolet spectroscopy confirms the findings of solubility studies that Sb(III) in 3–12 M hydrochloric acid solutions is present as an equilibrium mixture of SbCl 4 − and SbCl 6 3− ions. In the presence of H 2 SO 4 a further equilibrium with the SbCl 3 (HSO 4 ) − ion is found. The spectrum of the SbCl 6 3− ion in so…