Materials Literature
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Two aerogel systems containing a ferroelectric liquid crystal (FLC) with smectic phases over a wider temperature range are investigated using dielectric spectroscopy. The second order transition from Sm-A to $\mathrm{Sm}\ensuremath{-}{C}^{*}$ is considerably broadened and the collective modes are detected for the FLC…
Visible/near-IR-range radiation hardening of a pair of low-OH/low-Cl silica-core optical fibers has been accomplished by γ-ray preirradiation at 27 C to a dose of 13 MGy(Si) at a dose rate of 1 Gy(Si)/s in the dark. Reirradiation under identical conditions three months later demonstrated a 25-fold decrease in the init…
We report our study of the effect of crystallinity on the magnetoresistance in epitaxial and polycrystalline La2/3Ba1/3MnO3 and La2/3Ca1/3MnO3 thin films. Magnetoresistance in epitaxial films exhibits field dependence and temperature dependence similar to bulk single crystals and sintered bulk ceramics. The polycrysta…
The presence of complex charge ordering (CO) phenomena in ${\mathrm{La}}_{1\ensuremath{-}x}{\mathrm{Sr}}_{x}{\mathrm{FeO}}_{3}$ $(0\ensuremath{\le}x\ensuremath{\le}0.7)$ has been revealed by transmission electron microscopy at low temperatures. In ${\mathrm{La}}_{0.7}{\mathrm{Sr}}_{0.3}{\mathrm{FeO}}_{3}$ $(x\phantom{…
The high-pressure phases of FeO and MnO were studied by the first principles calculations. The present theoretical study predicts that the high-pressure phase of MnO is a metallic normal B8 structure (nB8), while that of FeO should take the inverse B8 structure (iB8). The novel feature of the unique high-pressure phas…
We discuss a method for determining the optimally-localized set of generalized Wannier functions associated with a set of Bloch bands in a crystalline solid. By ``generalized Wannier functions'' we mean a set of localized orthonormal orbitals spanning the same space as the specified set of Bloch bands. Although we min…
We suggest that the commonly accepted core structure of the 90\ifmmode^\circ\else\textdegree\fi{} partial dislocation in Si may not be correct, and propose instead a period-doubled structure. We present local-density approximation, tight-binding, and classical Keating-model calculations, all of which indicate that the…
The response of disordered P(d-S-b-MMA) diblock copolymers to variable strength surface fields has been studied by neutron reflectivity. Surface interactions were controlled by end grafting P(S-r-MMA) random copolymers with various styrene contents onto Si substrates. The degree interfacial segregation of the block co…
We have measured the diffusion of deuterated polystyrene of molecular weight $90\ifmmode\times\else\texttimes\fi{}{10}^{3}$ in various matrices of hydrogenated polystyrene as a function of distance from an attractive interface, oxide-covered silicon. Surprisingly long-range effects are observed. Diffusion rates an ord…
Filters fabricated from metalized polyimide have been specified for a number of x-ray astronomy missions, including the Advanced X-ray Astrophysics Facility (AXAF), the x-ray spectrometer (XRS) on Astro-E, the Advanced Composition Explorer (ACE), and the Geostationary Operational Environmental Satellite (GOES). Polyim…
A numerical method for the evaluation of magnetic iron losses in steel laminations used in electrical machines is described. The magnetodynamic model for the magnetic field strength H, derived from the Maxwell equations, is coupled with the Preisach theory, describing the hysteresis behaviour. The resulting highly non…
The compressional wave velocity in molten iron containing 5 percent nickel and 10 percent sulfur increased with increasing temperature. This anomalous behavior was determined to be attributable to the presence of sulfur, which conditions the formation of large molecular units in the liquid. Temperature-induced breakup…
Blends of polyethylene terephthalate (PET) and polypropylene (PP) at compositions 20/80 and 80/20 were modified with three different styrene–ethylene/butyl–ene-styrene (SEBS) triblock copolymers with the aim of improving the compatibility and in particular the toughness of the blends. The compatibilizers involved an u…
We report first-principles frozen-phonon calculations for the determination of the force-free geometry and the dynamical matrix of the five Raman-active A1g modes in YBa2Cu3O7. To establish the shape of the phonon potentials atomic forces are calculated within the LAPW method. Two different schemes - the local density…
In the present article, chitin from crab shell was systematically deacetylated using a NaOH treatment with control of the reaction time. The degree of deacetylation, monitored using solid-state NMR, revealed that the reaction was pseudo-first order. Based on this, swollen and NaOH-saturated particles are proposed as t…
Small structural perturbations in the enzyme isocitrate dehydrogenase (IDH) were made in order to evaluate the contribution of precise substrate alignment to the catalytic power of an enzyme. The reaction trajectory of IDH was modified (i) after the adenine moiety of nicotinamide adenine dinucleotide phosphate was cha…
Highly polarization-selective diffractive optical elements for use in optical interconnection and routing systems have been fabricated by the wet etching of pairs of calcite substrates and characterized experimentally. We show that when an index-matching polymer is used to fill the gap between the two substrates, subs…
We describe a method of fabricating multilevel diffractive optics by excimer laser ablation. A portion of a chrome mask containing many patterns is illuminated by 193-nm laser light and imaged by an objective lens onto a poly(imide) substrate. Ablation of an entire single pattern is achieved in a single laser pulse. M…
In the work a macroscopic equation of yield stress of steel is showed. We have used a new thermo-elastic and thermo-visco-plastic material. The model takes into account the history of the material and a possibility of phase change in it to occur, with temperature-dependent material properties. An examplary to calculat…
Diffractive optical elements with blazed profiles can, in theory, have 100% relative efficiency. We review several methods for making such elements and compare their advantages and limitations. Our emphasis is on processes to produce elements other than those with approximate, stepped surfaces, such as binary optical…