Materials Literature
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Polarized Raman spectra of tetragonally distorted (Ba1—xSrx)TiO3/MgO ferroelectric films were obtained in special scattering geometries using a micro-Raman set-up. The underdamped E(TO) soft mode was unambiguously observed in the films with x = 0.30 and 0.45. The low-temperature behaviour of the E(TO) soft mode for x…
A two-dimensional model for solidification and secondary phase precipitation in directionally solidified superalloys is presented, which makes use of a shape function approximation for the isothermal cross-section of the primary dendrites. The phase boundary is represented by a diffuse interface on a finite difference…
Despite lack of knowledge on the nucleation process, the bend domain growth is observed as a motion of disclinations, whose velocity can be determined from the energy difference between two states by applying the boundary-layer model and a damping factor. The disclination velocity is proportional to the electric field…
A novel specimen design and testing strategy has been exploited to determine the effect of thermomechanical processing on the microstructural development of the near β titanium alloy, Ti–10V–2Fe–3Al. A double truncated cone test geometry was isothermally deformed at near βtransus (∼795°C) temperatures, to obtain micro…
Co filled carbon nanocapsules, which are formed by a heat treatment of the mixture of Co and diamond nanoparticles, have been studied by in situ transmission electron microscopy (TEM), x-ray diffraction, and Raman spectroscopy. Raman studies show that the heat treatment reduces the surface native oxide (Co3O4) of Co n…
Liquid-crystal single materials with large negative dielectric anisotropies, high clearing temperatures and extremely low rotational viscosities were identified. Using these materials, the rotational viscosities for a broad range of mixture specifications were significantly reduced. Thus, these mixtures are found suit…
Glucose-1-phosphate thymidylyltransferase (RmlA; E.C. 2.7.7.24) is the first of four enzymes involved in the biosynthesis of dTDP-L-rhamnose, the precursor of L-rhamnose, a key component of the cell wall of many pathogenic bacteria. RmlA catalyses the condensation of thymidine triphosphate (dTTP) and alpha-D-glucose-1…
Phase diagrams of some compounds showing optically isotropic mesophases are compared as a function of the number of paraffinic carbon atoms per molecular core. In spite of a wide range of the transition temperatures, the number of paraffinic carbon atoms required for the appearance of the isotropic mesophases is limit…
The perplexing problem of the extremely large activation energy for nucleation Uac∼106 eV, which, as was shown by Landauer, appears in the Merz thermal-fluctuational theory of ferroelectric switching, is examined. Such enormous values of Uac are a result of the combined contribution of the energy of the depolarization…
The classical interpretation of fabric friction is viscoelastic, but its correlation with compression curves is poor. Measurements show that at low pressures, friction essentially depends as much on fabric hairiness as on compression. The limit of compressibility is a function of the yarn arrangement, the yarn structu…
The use of porous silicon (PS) as an efficient surface enlarging carrier matrix for immobilised enzymes is demonstrated. An optimal porous matrix in p-type silicon (10–20 Ωcm) with respect to enzymatic substrate turn-over was obtained when anodising the sample at 100 mA/cm2 for 5 min. An increase in glucose turn-over…
A cellular automaton–finite difference (CAFD) computer model is presented that describes the solidification of multicomponent multiphase alloys at the microscopic level. The objective of the model is to enable the prediction of microsegregation patterns and the appearance of non-equilibrium constituents during non-equ…
Efficient luminescent materials in solution, powder, or thin-film form are made here by combining poly(ethylene glycol) (PEG), terpyridine, and metal cations. Strong green emitters with a luminescence yield as high as 0.63 are reported for terpyridine–metal ion complexes suspended in liquid PEG. Evidence is presented…
Diatoms were sampled from over 200 first to third order Himalayan streams, at altitudes of 350–4700 m asl, between 1992 and 1996. This paper describes two new species, one new variety and Cymbella stuxbergii, providing extensive water chemistry and habitat data for these taxa. Gomphonema chubichuensis occurred at high…
We present ab initio calculations concerning the bond scission rate in a polyethylene chain. The energy barrier for scission is calculated both by using an effective potential scheme based on ab initio data and from the ab initio transition state itself. In the latter case the prefactor for scission is calculated. In…
The experimental conditions for {111} twin formation in BaTiO 3 were investigated. When BaTiO 3 compacts without excess TiO 2 were sintered either in an oxidizing atmosphere (air) or in a reducing atmosphere (95N 2 –5H 2 ), no {111} twins formed within the BaTiO 3 grains and no abnormal grain growth occurred. In contr…
In recent years, the problem of void swelling has been treated within the framework of the production bias model (PBM). The model considers the intracascade clustering of vacancies and self-interstitial atoms (SIAs), their thermal stability and the resulting asymmetry in the production of free and mobile vacancies and…
Synthesis of a new class of triethoxysilane materials for photoinduced orientation of liquid crystals is reported. A feature of these silanes is the incorporation of a photosensitive chromophore in the chemical structure. This leads to the formation of a complete monolayer with smooth surface morphology. The effect of…
Calcium hydroxide (Ca[OH]2) surface films were found to enhance the efficiency of hydrogen absorption over a range of hydrogen overpotentials for cold-worked 99.5% alpha Fe and isothermally transformed 0.8% C pearlitic steel (AISI 1080) during galvanostatic charging. Devanathan/Stachurski permeation experiments were c…
We present a theoretical investigation about the role played by spatial correlation among nuclei in the kinetics of first-order phase transitions. From the cluster expansion of the distribution functions in terms of the m-dots correlation functions, we obtain the equation which describes the kinetics in case of simult…