Materials Literature
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Ultraviolet-light excitation of thermochemically reduced ${\mathrm{MgAl}}_{2}$${\mathrm{O}}_{4}$ single crystals below room temperature produces a luminescence band with a peak at 2.69 eV. The excitation spectrum of the 2.69-eV band coincides with the broad F-center absorption band at 5.30 eV. The 2.69-eV band is also…
The band structures and density of states of all polycrystalline forms of ${\mathrm{SiO}}_{2}$ with known crystal structures are calculated using a first-principles orthogonalized linear combination of atomic orbitals method. These include 4:2-coordinated polymorphs of \ensuremath{\alpha}-quartz, \ensuremath{\beta}-qu…
The spontaneous decay rates of LA phonons are calculated in terms of the second- and third-order elastic constants in the isotropic model. It is shown that the dominant decay channel is LA\ensuremath{\rightarrow}TA+TA but not LA\ensuremath{\rightarrow}LA+TA and total decay rates at 1-THz frequency range from ${10}^{5}…
Thermal coupling and etch rate measurements are reported for polyethylene terephthalate and polyimide films irradiated at excimer laser wavelengths of 193, 248, and 308 nm. Thermal energy balance is observed up to a threshold fluence but above this the energy absorbed remains approximately constant, the excess energy…
Neutron and X-ray diffraction studies and magnetization measurements were carried out on single crystals of (Ba 1- x Sr x ) 2 Zn 2 Fe 12 O 22 . The substitution of Ba by Sr produces two effects on the crystal structure: a lattice deformation around the Sr ions and a redistribution of the Zn and Fe ions in the tetrahed…
Self-consistent, spin-polarized energy-band calculations have been performed for MnSb, for both ferromagnetic and antiferromagnetic spin alignments. For ferromagnetic MnSb we find a 3${d}^{5.5}$ configuration on the Mn atom, with a magnetic moment of 3.3${\ensuremath{\mu}}_{B}$ on the Mn sites, and -0.06${\ensuremath{…
The crystal structure of low cristobalite (SiO2) was refined at 10, 293, and 473 K from time-of-flight neutron powder diffraction data. One of the Si-O distances and one Si-O-Si angle change considerably: 10 K, 1.602(1) and 1.617(1) Å, 144.7(1)°; 473 K, 1.605(2) and 1.590(2) Å, 148.4(1)°. The angular distortion of the…
Luminescence yields and decay lifetimes were measured on some metalloporphyrins including the complexes of the IIIb metal group. The S2 emission was observed for AlClTPP (TPP: tetraphenylporphin), GaClTPP, and InClTPP as well as some other TPP metal complexes, ZnP (P:porphin) and H4P2+ (diacid), while it was not detec…
Ion-beam sputter deposition of tantalum oxide films was investigated for possible optical coating applications. Optical properties of such films were found to be a sensitive function of oxygen-to-argon ratio in the ion beam. Refractive index and absorption coefficient were determined in the 250–2000-nm wavelength rang…
Any arbitrary generalized gradient-index interference coating (including homogeneous and inhomogeneous layers) possesses a digital configuration (sequence of thin high- or low-index layers), which is spectrally equivalent at all wavelengths. Such digital configurations are found directly from arbitrary-index profiles…
The ${\mathrm{Ni}}_{80}$${\mathrm{P}}_{20}$ alloy system has been investigated in both liquid and amorphous solid forms using molecular-dynamics computer simulation. Atomic interactions were modeled by central pair potentials selected to represent roughly the atomic sizes and relative bond strengths. Self-diffusion co…
The feasibility of producing erbium-doped silicon light-emitting diodes by molecular beam epitaxy is demonstrated. The p-n junctions are formed by growing an erbium-doped p-type epitaxial silicon layer on an n-type silicon substrate. When the diodes are biased in the forward direction at 77 K they show an intense shar…
The depolarised Rayleigh scattering temperature dependence of the seventh, eighth, ninth and tenth homologues of 4,n-alkyloxybenzoic acid was investigated. A sharp increase of the scattered light intensity upon cooling was observed in the middle of the nematic phase. Polarised microscopic investigations confirmed the…
Single crystal E.P.R. spectra of Fe(III) doped in hexaimidazole zinc(II) dichloride tetrahydrate have been investigated. The spectra are characteristic of Fe(III) occupying a substitutional zinc site and where it is under the influence of a strong tetragonal crystal field from the six imidazole ring nitrogens: superpo…
A high-pressure X-ray scattering study has revealed that the compressible molecular crystal SnI 4 gradually transforms from the crystalline to the amorphous state, this process being accompanied by a remarkable decrease in electrical resistivity induced by the pressure. Taken together with the Raman scattering study d…
The electronic band structure of black phosphorus has been studied by angle-resolved ultraviolet photoelectron (ARUPS). The experimental valence band structure has been successfully obtained by the use of the He I and Ne I resonance lines. The binding energies of some special points with almost no interlayer energy di…
Coherent inelastic neutron scattering provides detailed information about the correlated atomic displacements in the vibrational modes of a glass. As an example, we show the wave-vector dependence of the scattering function of vitreous Si${\mathrm{O}}_{2}$ corresponding to different peaks in the one-phonon density of…
A procedure for preparing titanium alloys is described. The procedure includes activation in a solution of chromic and hydrofluoric acids and perferentially dissolves the baser phase of the titanium alloys. Titanium alloys can then be plated, obtaining good adhesion. Adhesion ranges from 70-120 N/mm2. Only during chro…
Procedures for recording the proportion of coarse fibers in greasy wool sale lots were compared. The percentage of fibers greater than 1.5 times the mean provided an estimate of the coarse edge that was precise and not particularly sensitive to outliers; however, due to the high multiple correlation of this statistic…
The effects of amides and detergents on collagen to gelatin transition have been studied at neutral pH. Simple amides denature the protein. The substitution of H-atoms by the alkyl groups at the nonpolar end of amide increases the effectiveness of the compounds in destabilizing the collagen structure whereas substitut…