Materials Literature
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The crystal structures of NH 4 SCN are determined in the tetragonal phase I (122°C) and the orthorhombic phase II (100°C, 110°C and 115°C) from X-ray diffraction data. In phase I, SCN - ion is in disordered state taking two equivalent configurations. In phase II, the ordering of SCN - ion correlates to the spontaneous…
Cristallisation dans P2 1 /c avec a=5,767, b=10,574, c=6,835 A, β=105,04 o , z=4; affinement jusqu'a R0,062. L'arrangement atomique est identique a celui de NaBUO 5 orthorhombique, sauf en ce qui concerne l'ion alcalin. Les ions lithium sont, en effet, situes dans les sites tetraedriques, tandis que les ions sodium se…
Cristallisation dans Pbcn avec a=5,683, b=4,784, c=14,648 A, z=4; affinement jusqu'a R=0,063. Cette structure, differente de celle du Li 2 Si 2 O 5 stable, est au contraire similaire a celle du Na 2 Si 2 O 5 -α. Elle consiste en feuillets infinis de silicate, composes de tetraedres de SiO 4 se partageant les sommets,…
The 19F n.m.r. spectrum of 3-fluoro-3-deoxy-D-glucose (3FG) in a red-cell suspension was observed to contain separate resonances from the intra- and extra-cellular populations of both the alpha- and beta-anomers. This phenomenon was used with an n.m.r. spin-transfer procedure to measure the rate of exchange of the ano…
The revised Enskog kinetic theory (RET) is used to describe transport in a hard sphere crystal. The connection between the RET and the exact density functional theory (DFT) description of the solid state is established. The RET is used to derive the dissipative linear equations of elasticity. The elastic moduli in the…
Time-resolved light scattering was employed to elucidate the dynamics of phase separation in mixtures of polycarbonate (PC) and polymethyl methacrylate (PMMA). Blends of PC and PMMA of moderately low molecular weight reveal the coexistence of an upper critical solution temperature (UCST) and a lower critical solution…
The band structure and the interband optical conductivity of a ${\mathrm{LiB}}_{3}$${\mathrm{O}}_{5}$ crystal with excellent nonlinear optical properties are studied by means of a first-principles method. The electronic structure is characterized by highly localized bands with a direct gap of 7.37 eV at \ensuremath{\G…
Rate constants for OH(X 2Πi, v=1–3) vibrational relaxation induced by nonreactive collision with O2 have been measured. OH(v) is created by the H+O3 →OH(v≤9)+O2 reaction in an electron-irradiated O3, H2, Ar mixture. OH(v) fundamental and first overtone IR emission is observed using time-resolved Fourier spectroscopy.…
Calcium aluminate glasses melted in graphite crucibles were found to show photochromism. Upon exposure to ultraviolet radiation, broad absorptions with an apparent peak of around 2 eV and a shoulder around 3.5 eV were induced, and after interruption of the light illumination both bands faded at room temperature. A dis…
We report measurements on the electrical- and thermal-transport properties of fluorine-intercalated vapor-grown carbon fibers ${\mathrm{C}}_{\mathit{x}}$F with the carbon-to-fluorine-atom ratio x between 4.1 and 5.8. The electrical resistivity is found to be very sensitive to the fluorine concentration. Indeed, while…
A general theoretical approach to the modeling of several different process steps in fabrication of ion-exchanged channel waveguides is presented. All of the commonly used fabrication processes are included, and the nature of the ion source and the effect of external electric voltage are taken into account. The model…
Dichloromuconate cycloisomerase from Alcaligenes eutrophus JMP 134 was purified to homogeneity. The enzyme has an Mr of about 270,000 as determined by gel filtration and consists of six to eight subunits of identical Mr 40,000 as determined by SDS/PAGE. Mn2+ ions as well as thiol groups are required for activity. A hi…
Diamond crystals and thin films were prepared by thermal decomposition of methane and hydrogen, in the presence of a hot tungsten filament. Raman microspectroscopy investigations were carried out and correlated to scanning-electron-microscopy observations of the crystallization. It is shown that the diamond Raman sign…
A multiple-scattering analysis of low-energy electron-diffraction intensities has been made for the Cu(110)2\ifmmode\times\else\texttimes\fi{}1-O surface structure, a system for which different techniques have recently been providing very different conclusions regarding both the nature of the reconstruction of the cop…
The optical properties of a sample containing several GaAs quantum wells of different widths separated by relatively thick but leaky ${\mathrm{Al}}_{0.3}$${\mathrm{Ga}}_{0.7}$As barriers are investigated at temperatures up to 150 K. Electrical bias, applied using a Schottky gate, tilts the energy bands and results in…
Elastic and inelastic He-atom scattering has been used to measure the surface structure and surface dynamics of the layered transition-metal dichalcogenide 2H-${\mathrm{TaSe}}_{2}$(001) crystal. The results cover temperatures from 60 to 140 K. Below ${\mathit{T}}_{0}$=122 K an incommensurate charge-density wave (CDW)…
CsHSO 4 cristallise dans P2 1 /c avec a=8,214, b=5,809, c=10,984 A, β=119,39 o , z=4; affinement jusqu'a R=0,057 a 296 K (phase basse temperature). La structure est legerement differente de celle etudiee precedemment avec le groupe d'espace P2 1 /m et z=2. La maille est constituee de 2 pseudo-mailles. Deux sortes de c…
Electrochromic, crystalline WO3 films have been deposited on glass substrates at ambient temperature by an oxygen-ion-assisted technique using oxygen ion energies ≥300 eV and oxygen ion to vapor molecule (WO3) ratios, γ≥2.5. After lithiation, the resulting LixWO3 films exhibited >50% reflectivity in the near in…
We report the first full band-structure calculation of the linear optical properties of strained (Si${)}_{\mathit{n}}$/(Ge${)}_{\mathit{n}}$ superlattices on Si(001) substrates for n=2,3,4. We use a semi--ab initio minimal basis orthogonalized linear combination of Gaussian orbitals technique, in conjunction with a li…
The ${\mathrm{Tm}}^{3+}$\ensuremath{\rightarrow}${\mathrm{Tm}}^{3+}$ and ${\mathrm{Tm}}^{3+}$\ensuremath{\rightleftarrows}${\mathrm{Ho}}^{3+}$ energy transfers have been studied in both Tm-doped and (Tm,Ho)-doped indium-based fluoride glasses over a wide temperature range for several dopant concentrations. The regime…