Materials Literature
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We have used solution small-angle X-ray scattering to characterize bovine brain calmodulin in the presence and absence of calcium. In the presence of calcium, calmodulin exists in solution as an elongated molecule with a radius of gyration of 21.5 A and a maximum vector length of approximately 62 A. These values are c…
The existence of large-sized satellite faces on crystals of the mineral calaverite (${\mathrm{Au}}_{1\ensuremath{-}x}{\mathrm{Ag}}_{x}{\mathrm{Te}}_{2}$) is reported. These anomalous high-index faces can be related directly to the wave vector q of the displacive incommensurate modulation recently found in the crystal…
The effect of high magnetic fields on the electronic structure of very anisotropic systems with charge- or spin-density waves is examined. In materials where there is lack of perfect nesting at the Fermi surface the density wave produces small electron and hole pockets. Calculations show that the presence of a high ma…
Diffuse low-energy-electron diffraction measurements at 46 eV for a disordered O/W(100) surface at 120 K have been interpreted by theory to give the local geometry of the oxygen atoms. This first application of the technique shows that phonon scattering does not prevent interpretation of data, and demonstrates sensiti…
We observe for the first time the transformation of glassy alloys (${\mathrm{Pd}}_{100\ensuremath{-}x\ensuremath{-}y}{\mathrm{U}}_{x}{\mathrm{Si}}_{y}$, $x\ensuremath{\simeq}y\ensuremath{\simeq}20$ at.%) into a metastable icosahedral phase with quasicrystalline order upon annealing. The icosahedral symmetry of the lat…
Experimental results are given on the incommensurate phase and on related phasetransitions in barium sodium niobate obtained by means of electron diffraction and electron microscopy. Evidence is found for discommensurations (DC) in the quasicommensurate phase of barium sodium niobate with detailed observations. A crys…
The changes in the dielectric constant ( ε ) of a single crystal of KTaO 3 and of a ceramic plate of SrTiO 3 were measured at 4.2 and 20.4 K in magnetic fields up to 15 T to examine recent vibronic-theory predictions. It is found that these changes are orders of magnitude smaller than predicted and are of opposite sig…
Oxidation studies of copper films at room temperature have been carried out by measuring the ATR spectra involving information about surface plasmon polariton characteristics. Oxidation is initially rapid, but after 10 to 20 minutes, drops to a negligible value, a stable film being formed ∼2.7 nm thick. It has been fu…
We report the first lattice-dynamical study of ${\mathrm{V}}_{2}$${\mathrm{O}}_{3}$ and (${\mathrm{V}}_{0.985}$${\mathrm{Cr}}_{0.015}$${)}_{2}$O $_{3}$ in the long-wavelength limit using a rigid-ion model with an effective ionic charge and various short-range interactions. The parameters of the model were determined f…
A multiple-scattering calculation of the neutron refractive index is performed by an extension of the Fermi-Huygens technique. The extension involves projecting the problem into a one-dimensional walk by integrating out the transverse coordinate in a semi-infinite medium and then partially summing parts of the walk to…
A new class of crystalline structures for group-IV materials is proposed. The basic building block for all the new structures is a two-dimensionally ordered slab of atoms which can be stacked together in several distinct ways. The most stable structure obtained in this way has a 20-atom orthorhombic unit cell. For Si,…
A digitonin-solubilized cellulose synthase was prepared from Acetobacter xylinum. When this enzyme was incubated under conditions known to lead to active synthesis of 1,4-beta-D-glucan polymer (cellulose), electron microscopy revealed that clusters of fibrils were assembled within minutes. Individual fibrils are 17 +/…
We consider the propagation of bulk and surface plasmons in a finite superlattice structure composed of alternating layers of materials A and B, with the whole structure resting on a substrate. An implicit dispersion relation is derived allowing the dielectric constant of each material to be a function of frequency. W…
Perturbation calculations are performed for 〈R2〉, 〈S2〉, 〈RH〉, A2, and A3 for polymers near the theta point using a continuous curve representation of the three-parameter theory of Yamakawa. Both dimensional regularization and cut-off schemes are employed, but only the latter method is shown to be in accord with observ…
The band gap and quasiparticle energies in LiCl are calculated by evaluation of the electron self-energy operator including the effects of local fields and dynamic screening from first principles. Good agreement with available experimental data is obtained. In particular, the calculated band gap for bulk transitions (…
The 0.875-eV (Ga1) photoluminescence defect spectrum in gallium-doped irradiated silicon is studied in high resolution and in uniaxial stress and homogeneous magnetic fields. The spectrum exhibits one- and two-phonon Stokes satellites of the no-phonon Ga1 line due to the coupling of quasilocalized vibrational modes of…
Magnesium self-diffusion in MgO crystals has been studied over the temperature range 1100--1250 K with the use of the nuclear reaction $^{18}(\mathit{p}$,\ensuremath{\alpha})${}^{15}$N. Magnesium drift due to an electric field was determined, and from the buildup of Mg $^{18}$O at the cathode, diffusion coefficients a…
fl l-V2H: M r = 102.89, tetragonal, I4~/amd, a = 6.0349 (4), c = 6.8716 (3)/k, V = 250.3 A 3, D x = 5 . 4 6 M g m -3, Z = 8 , 2 (MoKa)=0 .7107 /k , /~= 13.65 mm -1, F(000)= 376.0, room temperature, final R-0 .031 for 154 independent reflections; fl-V2D: M r = 103.9, monoclinic, Cm, a = 4 . 4 5 5 4 ( 7 ) , b = 3.0090 (…
Decay curves and spectral shapes of the singlet-exciton luminescence in anthracene crystals have been studied at room temperature and found to depend on the experimental geometry and on the penetration depth of the exciting light. The well-known wavelength-dependent decay time and time-dependent spectrum occur only wh…
We have developed a theory of low-temperature thermal expansion of glasses explaining a number of existing experimental data. We assume that thermal expansion, like many other low-temperature properties of glasses, is determined by associated two-level systems (TLS's); this concept has been introduced to explain these…