Materials Literature
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New homologous symmetric dimers are presented in which two-ring monomers are connected by a flexible spacer and perfluorinated chains are introduced in terminal positions. The mesophase behaviour depends on the length and structure of the spacer and on the length of the terminal chains. The most interesting finding is…
Abstract Theoretical expressions based on Ohm's law for field theory were derived to measure surface resistivity of high‐resistance polymer films using parallel plate and concentric circular electrodes. Experimental measurements of resistivity were compared to experimental measurements using conventional expressions b…
We studied the collective elastic interaction in a system of many macroparticles embedded in a nematic liquid crystal. A theoretical approach to the interaction of macroparticles via deformation of the director field [1] is developed. It is found that the director field distortion induced by many particles leads to th…
The aim of this experiment is to grow a thin silicon layer (<50μm) by Liquid Phase Epitaxy (LPE) onto porous silicon. This one acts as a sacrificial layer in order to transfer the 50 μm epitaxial layer onto foreign substrates like ceramics. After transfer, the silicon wafer is then re-usable. In this work, we used the…
We demonstrated a method for measuring the quantum efficiency of deep UV emission using the two-step excitation and the difference of the integrated spectral intensities in Pr3+-doped CaAl4O7 and SrAl4O7 crystals. The quantum efficiencies of the emission from the lowest 4f5d state in the two systems have been estimate…
This is the second part of our study on needle heating in heavy industrial sewing. In this part, a finite element analysis (FEA) model is presented. Using a commercial FEA software system, ANSYS, the needle is modeled by a number of 3D bar elements and the sewing process is modeled by a series of time and space depend…
We describe an innovative yet straightforward method to obtain high quality thin sections of diatom exoskeletons for observation by scanning electron microscopy (SEM). The use of this new technique allows for clear observations of some ultrastructural valve features, including the raphe, which are generally difficult…
Dy3+-doped chalcogenide glasses are potential candidates for 1.3-µm optical-fiber amplifiers. We describe spectroscopic characterization of Dy3+-doped gallium lanthanum sulphide glasses with low and high oxide content. The spectroscopic investigations show that small amounts of oxide (∼1%) in low-oxide-content sulphid…
Polymer dispersed liquid crystal (PDLC) films consist of microdroplets of a liquid crystal dispersed in a polymer matrix. Their applications are based on the electrically controllable light scattering properties of the liquid crystal droplets. The effects of temperature on the electro-optical properties of PDLC films…
The strength of nearly all metallic and ceramic polycrystalline materials drops off rapidly with increases in temperature. Here we have developed a strong and tough oxide composite reinforced with a ductile phase at 1873 K with a different kind of microstructure, made by unidirectional solidification of an Al2O3-Y3Al5…
X-ray scattering evidence for macroscopic strong pinning centers in the sliding CDW state of NbSe3 , D. Rideau, P. Monceau, R. Currat, H. Requardt, F. Nad, J. E. Lorenzo, S. Brazovskii, C. Detlefs, G. Grübel
The toughness of amorphous precursor‐derived ceramics in the Si‐C‐N system is investigated. Crack‐growth data are obtained from DCB specimens, whereas the crack‐tip toughness is determined from the crack‐tip profile of indentation cracks. For amorphous Si‐C‐N ceramics that have been fabricated via the powder route, an…
The first results regarding the crystallization kinetics of the pure semisynthetic β-lactam antibiotic (SSA) ampicillin in water are presented. The experimentally obtained results at pH = 5 and T = 298 K are described well by the population-based crystallization model presented in this paper. The nucleation rate J (#…
The synthesis of new metal-free and zinc(II), cobalt(II) phthalocyanines substituted with four 4-(2-N'-cyanoethyl)aminoethylsulfanyl groups is described. The new compounds have been characterized by elemental analysis and IR, 1 H NMR and UV-vis spectroscopy.
Stereocomplexation between two enantiomeric polymers such as D-PLA and L-PLA have been described in the literature. No reports up till now have been published on the complexation between two non-identical complementary polymers. Stereocomplexes between poly(lactide) enantiomers and a representative peptide, LHRH, was…
Photodynamic therapy consists of the uptake of a photosensitizing dye, often a porphyrin, by tumor tissue and subsequent irradiation of the tumor with visible light of an appropriate wavelength matched to the absorption spectrum of the photosensitizing dye. This class of molecules produces reactive oxygen species when…
Diffractive optical element design is an important problem for many applications and is usually achieved by the Gerchberg-Saxton or the Yang-Gu algorithm. These algorithms are formulated on the basis of monochromatic wave propagation and the far-field assumption, because the Fourier transform is used to model the wave…
By using polarizing microscopy analysis we have found that several achiral homologues of the 4-n-alkyloxybenzoic acids, displaying only the nematic phase, exhibit the optical properties of a chiral liquid crystal system. These acids possess a mesophase due to the formation of dimers via hydrogen bonding. The microtext…
The present report presents results obtained from an interlaboratory test. 28 participants, mainly from industry and research institutes, measured glass transition temperatures (Tg) by differential scanning calorimetry (DSC) on four different polymers. The materials used were poly(methyl methacrylate) (PMMA), polycarb…
Nanometer-sized Si dot multilayers have been prepared by repeating a sequence of low-pressure chemical vapor deposition for dot formation and thermal oxidation for dot isolation. For the multilayer with Si dots in the range of 3–5 nm, the onset of photoconductivity is observable at a photon energy of 2 eV, correspondi…