Materials Literature
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Two orthogonally aligned liquid crystal lenses with spherical Fresnel zone plate electrode configurations have been demonstrated to focus an unpolarised broadband object with resulting good quality images. Switch on times of 15ms are reported along with modulation depths of 91.5%.
The sphinx is a non-periodic tiling of the plane made of one type of tile. In order to characterise the type of order found in this tiling, the computation of its diffraction spectrum is considered. The spectrum contains a discrete component, with Bragg peaks located at the vertices of triangular lattices with lattice…
Abstract The thermolysis of vinyl methylterephthalate has been studied as a model of poly(ethylene terephthalate) (PET) thermolysis. Based upon this reaction, a potential mechanism for PET flame retardation is proposed. The assumption is made, based upon firm experimental evidence, that the initial step in PET degrada…
The dynamical behaviour of the alkyl chains in dicopper tetrapalmitate is investigated in the columnar liquid crystal phase, using incoherent quasielastic neutron scattering by several selectively deuterated derivatives. A mathematical model is developed for the evaluation of the scattering function which yields the f…
Lead monohydrogen phosphate (PbHPO 4 ) undergoes a ferroelectric phase transition at T c =310 K at atmospheric pressure. T c falls to room temperature at a pressure of about 0.125 GPa. The crystal structure of PbHPO 4 has been determined by X-ray diffraction at 2.0 and 2.3 GPa and the lattice parameters have been meas…
For the crystallization of proteins under microgravity conditions, a Chinese re‐entry system was used, in which 101 experiments of 25 different biological macromolecules were accommodated. From the results obtained we conclude that under microgravity conditions crystal growth can only be expected under those crystalli…
We present experimental evidence of the smectic-A (${S}_{A}$) phase in colloidal solutions of tobacco mosaic virus. The smectic-A phase is determined by the observation of a layered structure along the virus alignment direction and a liquidlike order within layers. In our samples, we also observed the characteristic $…
We have measured Raman spectra of diamond films prepared by a hot-filament method and found that diamond layers on Si substrates are under compressive strain. The degree of the strain is found to increase with increasing nondiamond component in the diamond films. It is shown that Raman spectroscopy is a powerful metho…
For pt.I see ibid., vol.21, p.1423 (1988). Several transition-metal compounds show a transition from the low-spin to the high-spin electronic state with increasing temperature. The cooperative nature of the transition in the solid state is attributed to the elastic interaction between the spin-changing ions as a resul…
The temperature dependence of x-ray peak intensities of icosahedral AlCuFe is studied in detail. Above 670 \ifmmode^\circ\else\textdegree\fi{}C, measurements of the Debye-Waller factor suggest the presence of dynamical phasons. Softening of the phason modes drives a structural transition at \ensuremath{\sim}670 \ifmmo…
We report light-scattering measurements of powder diffraction patterns of crystals of essentially hard colloidal spheres. These are consistent with structures formed by stacking close-packed planes of particles in a sequence of permitted lateral positions, A,B,C, which shows a high degree of randomness. Crystals grown…
For single-phase polycrystalline materials the relation is discussed between the elastic strain ϵ(ψ, φ) obtained from X-ray diffraction experiments and the polynomial expansion of the stress components σφ(σ) and σφ+90(z) with respect to the distance z from the external surface of the specimen. A universal plot is prop…
The charge-transfer (CT) interactions in electroactive polymeric complexes formed by nonconjugated polymers: poly-2-vinylpyridine, poly-4-vinylpyridine, and various halobenzoquinone electron acceptors such as: o-chloranil, p-chloranil, o-bromanil, and p-fluoranil have been investigated by means of x-ray photoelectron…
The fully oxidized form of polyaniline, pernigraniline, is studied in the framework of a Su-Schrieffer-Heeger-like Hamiltonian. The protonation process of a long oligomer is investigated. Protonation is modeled by a change in site energies around the protonated site. The results of the calculataions indicate that a ph…
Recently M. Tokunaga has published two interesting papers (J. Phys. Soc. Jpn. 56 (1987) 1653; 57 (1988) 4275) that relate the fluctuating polarizations p c in the paraelectric phases of ferroelectrics (estimated from the Curie constants determining the dielectric susceptibilities) and the spontaneous polarizations P S…
The translational diffusion coefficient D of long enough polymer chains without excluded volume is studied on the basis of the discrete helical worm-like (HW) chain with partially fluctuating (orientation-dependent) hydrodynamic interaction (HI). In order to evaluate D(∞) in the long time limit, which corresponds to d…
We present band-structure calculations of ${\mathrm{SnTaS}}_{2}$, an intercalation compound in which the Sn atoms have a very uncommon linear coordination by two S atoms and an unusual formal valency ${\mathrm{Sn}}^{1+}$. The Sn 5${p}_{x}$ and 5${p}_{y}$ states show strong metal-metal bonding in the intercalant planes…
We report the observation of 1/frequency magnetization noise in toroidal strip-wound cores of amorphous ferromagnetic alloys at liquid-helium temperatures and in the frequency range 0.1 Hz–1 kHz. The materials tested are Co-based alloys, and exhibit very low magnetostriction and good soft magnetic properties. The expe…
Layer Korringa-Kohn-Rostoker (LKKR) approaches that calculate interlayer scattering using a plane-wave basis set cannot treat systems in which the interplanar spacing becomes small. This problem is most acute at band energies at which electronic lifetimes are long and the scattering strong. Taking a face-centered-cubi…
The important role atomic hydrogen plays in the low-temperature and pressure deposition of diamond has renewed interest in the dissociation processes of hydrogen. Following a method originally developed by Langmuir and co-workers, the voltage-current characteristics of refractory filaments in vacuum and reduced-pressu…