Materials Literature
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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…
Heat treatment was performed on β‐SiC with different sintering additives in the temperature range 1873–2073 K, in both argon and nitrogen‐gas atmospheres. In the case of the specimens heat‐treated at 2073 K in argon, the weight loss was more than the total weight of the sintering additives, except for B,C‐doped β‐SiC.…
The coexistence of ferromagnetism and metallic conduction in doped manganites has long been explained by a double exchange model (ferromagnetic Kondo-lattice model) in which the ferromagnetic exchange arises from the carrier hopping. We evaluate the zero-temperature spin stiffness $D(0)$ and the Curie temperature ${T}…
The polaron-ordered structure of ${\mathrm{La}}_{1\ensuremath{-}x}{\mathrm{Sr}}_{x}{\mathrm{MnO}}_{3} (x\ensuremath{\cong}\frac{1}{8})$ has been reinvestigated to verify the previously proposed models. We found satellite reflections on the ${(0,k,l)}_{\mathrm{ortho}}$ and ${(1,k,l)}_{\mathrm{ortho}}$ reciprocal planes…
The characterization of ink jet dyes and inks printed onto paper surfaces is of importance for the development of ink jet ink formulations and for use in forensic science. Raman spectroscopy is an effective and informative probe for this purpose if problems associated with fluorescence are overcome. A comparison is ma…
Organic conductors based on the bis(ethylenedithio)tetraselenafulvalene(BETS) are of interest because they display not only superconducting and magnetic transitions but also, as recently reported, unprecedented superconductor to insulator transitions. Here is presented the electrical and magnetic properties for two se…
Abstract Diarylperfluorocyclopentenes having 2-isopropyl-5-phenylthiophene and 2-isopropyl-1-benzothiophene aryl groups underwent thermally reversible photochromism in solution. The photogenerated colored closed-ring isomers returned to the initial colorless open-ring isomers above 60 °C. The activation energies of th…
Abstract A unique catalyst, Au core and Pd shell bimetallic nanoparticles immobilized on porous silica exhibiting a considerable high activity for the hydrogenation of cyclohexene, was prepared via two steps composed of the sonochemical reduction method and the sol–gel process under a low temperature condition.
A range of 5,15-diphenylporphyrins with symmetric and unsymmetric substitution patterns were subjected to osmium tetroxide-mediated dihydroxylations. The resulting chlorins and bacteriochlorins present an important group of compounds for studying structure-activity relationships of photodynamic sensitizers. The regios…