Materials Literature
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A new homologous series of achiral banana-shaped mesogens ('Cn') has been synthesized and studied by classical techniques (optical microscopy, differential scanning calorimetry, X-ray diffraction and electro-optic investigations). Complete miscibility with compounds of the n-OPIMB series shows that the short homologue…
The behaviour of a liquid crystalline azobenzene material possessing a nematic phase was studied under UV illumination. It was found that a uniformly aligned planar sample of the azobenzene undergoes a reversible orientation transition to homeotropic; this can be interpreted as an anchoring transition caused by the ph…
Raman scattering measurements were carried out in self-organized Ge quantum dot superlattices. The samples consisted of 25 periods of Ge quantum dots with different dot sizes sandwiched by 20 nm Si spacers, and were grown using solid-source molecular-beam epitaxy. Optical phonon modes were found to be around 300 cm−1,…
Porous poly(L-lactide) (PLLA) films were prepared by water extraction of poly(ethylene oxide) (PEO) from solution-cast PLLA and PEO blend films. The dependence of blend ratio and molecular weight of PEO on the porosity and pore size of films was investigated by gravimetry and scanning electron microscopy. The film por…
A chemically cross-linked and water-swollen poly(3-thiopheneacetic acid) (P3TAA) gel was synthesized, and its swelling and spectral changes associated with its ionization were studied. The gel undergoes an abrupt red shift in the electronic spectra at a certain pH, suggesting that a conformational transition due to io…
The most important methods of synthesis and purification of carbon nanotubes, a new form of material, are described. The prospects for increasing the scale of preparation processes and for more extensive application of nanotubes are evaluated. The bibliography includes 282 references.
Rheological and morphological studies were performed on polymer blends of ethylene-octene copolymer [polyethylene elastomer (PEE)] and polypropylene (PP). The viscosities of PEE, PP, and PEE/PP blends were analyzed using an Instron capillary rheometer and a Rheometrics Dynamic Stress Rheometer, SR 200. A non-Newtonian…
X-ray diffraction was used to monitor the structure of 45 A diameter CdSe nanocrystals as they transformed repeatedly between fourfold and sixfold coordinated crystal structures. Simulations of the diffraction patterns reveal that a shape change occurs as the crystals transform. They also show that stacking faults are…
Precise control of composition and microstructure is critical for the production of (BaxSr1−x)Ti1+yO3+z (BST) dielectric thin films with the large dependence of permittivity on electric field, low losses, and high electrical breakdown fields that are required for successful integration of BST into tunable high-frequen…
Boomerang-shaped liquid crystals based on 2,5-bis(p-hydroxyphenyl)-1,3,4-oxadiazole (ODBP) having a ~ 134° bend in the mesogenic cores were synthesized and their properties investigated by optical microscopy and differential scanning calorimetry. Substituting the nonlinear ODBP mesogenic core with p-dodecyloxyphenyl t…
A numerical investigation of grain-boundary grooving by means of a Level Set method is carried out. An idealized polygranular interconnect which consists of grains separated by parallel grain boundaries aligned normal to the average orientation of the surface is considered. The surface diffusion is the only physical m…
Spin-polarized band calculations for LaSr_7B_{48} show a weak ferro-magnetic state. This is despite a low density-of-states (DOS) and a low Stoner factor. The reason for the magnetic state is found to be associated with a gain in potential energy in addition to the exchange energy, as a spin-splitting is imposed. An i…
Approaches to the preparation of organic–inorganic nanocomposites are considered from a unified viewpoint for the first time. The major problems in the development of this new line of research in materials technology, which has arisen on the border of the science of polymers, colloid chemistry and physical chemistry o…
A stable wurtzite phase of ZnO is commonly observed. In this letter, we report the growth and characterization of zinc-blende ZnO on GaAs(001) substrates. The ZnO films grown on GaAs(001) substrates using microwave-plasma-assisted metalorganic molecular-beam epitaxy were characterized by reflection high-energy electro…
By introducing a thin MgO buffer, layer-by-layer growth of ZnO epilayers on Al2O3(0001) substrates is achieved by plasma-assisted molecular beam epitaxy. The MgO buffer is very effective on the improvement of surface morphology during the initial growth stage, which eventually leads to an atomically flat surface. As a…
The segmental dynamics of 1.5-2.0 nm polymer films confined between parallel solid surfaces is investigated with dielectric spectroscopy in polymer/silicate intercalated nanocomposites. The confinement effect is evident by the observation of a mode, much faster than the bulk-polymer alpha relaxation and exhibiting muc…
The phonon thermal conductivity of a multilayer is calculated for transport perpendicular to the layers. There is a crossover between particle transport for thick layers to wave transport for thin layers. The calculations show that the conductivity has a minimum value for a layer thickness somewhat smaller then the me…
A short review of the experimental findings concerning the stabilization of emulsions by solid particles is given. We then describe the preparation and properties of water-in-oil (w/o) emulsions stabilized by nanometer-sized hydrophobic silica particles alone. Emulsions of median diameter equal to 0.6 μm are completel…
A new geographical locality for Extubocellulus spinifer is reported. The species was isolated during 1980 from a temperate ‘slikke’ (intertidal mudflat) in North Brittany and grown in batch culture for several years in F/2 medium under constant temperature and light conditions. No teratological modifications were obse…
Genes encoding the mitochondrial (SHM1) and cytosolic (SHM2) serine hydroxymethyltransferases, and the L-threonine aldolase gene (GLY1) from Candida albicans were cloned and sequenced. All three genes are involved in glycine metabolism. The C. albicans Shm1 protein is 82% identical to that from Saccharomyces cerevisia…