Materials Literature
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Cellulose is synthesized by all higher plants as well as by a wide variety of other organisms. The amount of synthesis is enormous, making cellulose the most abundant biopolymer on earth (1 ) . Most native cellulose is found in cell walls in the form of structural micro - fib rils . Although considerable effort has go…
The crystal structure of perlialite from the Murun Massif, U.S.S.R. was determined and refined using synchrotron X-ray powder data. The framework type of this natural zeolite is the same as synthetic zeolite Linde-L. Extraframework cation and water oxygen position were located, and the locations and occupancies show l…
After cooling below 80 K a considerable amount of diffuse scattering is observed in Li, in addition to 9R and fcc Bragg reflections. The diffuse scattering localized on the [101] line of the 9R reciprocal lattice is modulated along this line indicating a short-range order in the stacking sequence of the close-packed p…
Raman measurements were carried out on Ge quantum dots from 6.1 to 15 nm in size embedded in SiO2 thin films. The samples were prepared by rf co-sputtering and post- annealing. In contrast to the amorphous-like broad spectra previously obtained for gas- evaporated Ge microcrystals of comparable sizes, relatively sharp…
Nanometer-size diamond particles formed on a silicon substrate by the hot-filament chemical vapor deposition method were examined by a high-resolution electron microscope. The particles developed well-faceted cuboctahedral habits. Examination of their morphologies and microstructures provides a wealth of information o…
The ionic polarizabilities in Pb(ZrxTi1−x)O3 compositions are calculated by the Clausius-Mossotti-Lorentz-Lorentz equation. The resultant gap of the polarizability appearing at the morphotropic phase boundary (MPB) composition suggests the phase transition boundary to be due to the electrostatic long-range dipole mome…
The fluorescence spectrum of tripositive americium in a fluorozirconate glass at low temperature has been measured. Six fluorescence lines were observed between 515 to 880 nm and identified as Am3+ transitions. Fluorescence decay measurements at 15 K are reported for transitions that originate from states 5D1′ (∼1.0 m…
X-ray-diffraction patterns, macroscopic compressibility, and crystallization in amorphous Se subject to pressure have been investigated. The material exhibits pressure-induced structural modifications in the glassy state and a phase transformation to the hexagonal phase at 120\ifmmode\pm\else\textpm\fi{}20 kbar. The o…
The polarized memory effect, in which the switching between the on and off states depends on the polarity of the bias voltage, was found in the device including the film of the organic charge-transfer complex, copper-tetracyanoquinodimethane (Cu-TCNQ). The device consists of three layers, Al/Cu-TCNQ/Cu. The dc I-V cha…
A generalization of the well-known Flory and Flory–Huggins mean-field approximations to the equation of state is derived for a three-dimensional lattice model in which a monomer occupies an entire unit cell, and many bond lengths and bond angles are possible. By measuring the probability for particles to be in contact…
The energies of the two energetically lowest dipole-allowed electron-hole-pair states in semiconductor microcrystallites are computed variationally. Details of the quantum confinement conditions, such as the finite value of the quantum confinement potential and the different effective electron-hole masses inside and o…
C 14 H 8 S 4 + •I 3 − (I) cristallise dans C2/m avec a=19,831, b=9,266, c=14,515 A, β=90,03 o , Z=6; affinement jusqu'a R=0,0434. C 14 H 8 S 4 + •Cu(NCS) 2 − (II) cristallise dans P1 avec a=8,390, b=9,667, c=12,699 A, α=95,07, β=108,25, γ=112,50 o , Z=2; affinement jusqu'a R=0,142. Dans (I), les ions dibenzotetrafulva…
The magnetic permeability of stoichiometric or non-stoichiometric magnetite (Fe 3- y O 4 ) at high pressures has been measured in a piston-cylinder apparatus. The Verwey transition temperature decrease with pressure at rates of 2.7±0.1 KGPa -1 for y =0.000, 2.49±0.07 for y =0.0051, 2.3±0.1 for y =0.0063, 2.55±0.03 for…
The softening of elastic moduli associated with sliding of a charge-density wave is analyzed in the weak-pinning framework of Lee and Rice. The difference in stiffness between the stationary and sliding states is attributed to the difference in energy between phase configurations that have had time to adjust to the ap…
We present a derivation, based on Green's theorem, of the exact dispersion relation for the electrostatic modes guided by a channel of finite width cut into the otherwise planar surface of a solid in contact with vacuum. The solid, which can be either a metal or a polar dielectric medium, is characterized by a real, i…
First-principles calculations of the surface stress tensor of the aluminum (111) surface are presented that indicate the presence of a tensile stress. We compare our results for aluminum with those for jellium and investigate the origins of the surface stress. At high electron densities, such as that of aluminum, the…
Hole mobilities of binary solid solutions of tri-p-tolylamine and bisphenol-A-polycarbonate have been measured as functions of electric field and temperature for concentrations between 6% and 50% tri-p-tolylamine. The mobilities can be described by an exponential dependence on the square root of the electric field and…
High-quality diamond with good crystallinity has been successfully synthesized on a substrate using an oxy-acetylene combustion flame in the atmosphere. The crystal grains under some conditions have good optical transparency. The deposition rate of transparent diamond depended strongly on substrate temperatures and th…
A numerical model of the filament-assisted diamond growth environment has been developed and used to calculate temperature, velocity, and species concentration profiles, accounting both for transport and detailed chemical kinetics. The computed hydrocarbon concentrations agree well with previously measured values, whe…
We present measurements of the photoexcited states of poly(p-phenylene vinylene), PPV, and a model oligomer, trans,trans-distyrylbenzene, probed by detection of photoluminescence and photoinduced absorption. Photoluminescence is strong in both materials and due to radiative recombination of the singlet exciton. Triple…