Terminal velocity of non-spherical particles falling through a Carreau model liquid

A procedure has been proposed for the estimation of the terminal falling velocity of non-spherical particles moving in a Carreau model fluid in the transition flow region. The procedure is based on a modification of the relationship formerly developed for the fall of spherical particles including the particle dynamic shape factor. The suitability of the proposed procedure has been confirmed by good agreement between experimental and calculated terminal falling velocity data. In the experiments, the terminal falling velocity of short cylinders and rectangular prisms in polymer solutions of different measure of shear thinning and elasticity has been measured.     

The problem of the selection of an a posteriori error indicator based on smoothening techniques

This paper addresses the problem of assessing the quality of an a posteriori error estimate of a finite element solution. An error estimate based on local L2-projections is analysed in the case of translation-invariant meshes. It is shown that for general meshes this technique does not lead to an asymptotically exact estimator. The problem is analysed in detail in the one-dimensional setting. It is shown that an asymptotically exact estimator is not the optimal one when the solution is not sufficiently smooth. An optimal estimator for adaptively constructed meshes is given. Finally, a general mathematical framework for the quality assessment of estimators is introduced.     

Increased production of reactive oxygen species by rat liver mitochondria after chronic ethanol treatment

Rat liver microsomes and, to a lesser extent, nuclei were previously shown to produce reactive oxygen species at elevated rates after chronic ethanol treatment. The ability of intact rat liver mitochondria to interact with iron and either NADH or NADPH, and the effects of ethanol treatment, on production of reactive oxygen intermediates was determined. In the presence of ferric-ATP, NADH or NADPH catalyzed mitochondrial lipid peroxidation. Rates were elevated two- to threefold with mitochondria from ethanol-fed rats with both reductants. Mitochondrial lipid peroxidation was insensitive to superoxide dismutase, catalase, or hydroxyl radical scavengers but was sensitive to GSH and anti-oxidants such as trolox. Mitochondrial generation of hydroxyl radical-like species (assayed by oxidation of chemical scavengers) was increased after chronic ethanol treatment, as was H2O2 production. Modifiers of mitochondrial metabolism such as rotenone, cyanide, or an uncoupling agent, had no effect on mitochondrial production of reactive oxygen intermediates. The membrane-impermeable thiol reagent, p-chloromercuribenzoate, was complete inhibitory with both mitochondrial preparations. The activity of the rotenone-insensitive NADH-cytochrome c reductase, an enzyme of the outer mitochondrial membrane, was increased 40 to 60% by the ethanol treatment. These results suggest that NADH acting via the outer membrane NADH reductase can catalyze an iron-dependent production of oxygen radicals by rat liver mitochondria. The outer mitochondrial membrane fraction, prepared by digitonin fractionation, displayed increased rotenone-insensitive NADH-cytochrome c reductase activity after ethanol treatment and was more reactive in catalyzing scission of pBR322 DNA from the supercoiled form to the open circular forms. Rates of oxygen radical production by mitochondria and the extent of increase produced by chronic ethanol treatment are similar to those previously found with microsomes when NADH is the cofactor. Oxidation of ethanol by alcohol dehydrogenase generates NADH, and NADH-dependent production of reactive oxygen species by various organelles is increased after chronic ethanol treatment. These acute metabolic interactions coupled to induction by chronic ethanol treatment may play an important role in the development of a state of oxidative stress in the liver by ethanol.     

Accumulation of hydrogen and its influence on the microstructure and mechanical properties of Kh18N10T steel

By the methods of thermal-desorption spectrometry and nuclear reactions, we study the processes of trapping, thermal desorption, and evolution of the profiles of distribution of deuterium ionically implanted with an energy of 12 keV into Kh18N10T steel at room temperature. The evolution of the microstructure of steel under the conditions of irradiation of samples with D₂⁺ ions up to doses of 1 · 10¹⁸ D/m²−2 · 10²² D/m² is studied by the method of electron microscopy. The regularities of changes in the mechanical properties of steel after irradiation are determined. __________ Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 43, No. 5, pp. 117–121, September–October, 2007.     

Photopolymerization of N,N‐dimethylaminoethylmethacrylate studied by photocalorimetry

Photopolymerization of dimethylaminoethylmethacrylate (DMAEMA) is studied in bulk and in solutions in the presence of different photoinitiators using differential photocalorimetry (DPC). The rate of DMAEMA photopolymerization is slow compared to that of alkylmethacrylates. Bimodal DPC curves of DMAEMA photopolymerization in bulk are obtained. The type I photoinitiators (IRGACURE® 651 and IRGACURE® 1700), which produce free radicals by homolytic fragmentation of photoexcited molecules, are more effective in promoting photopolymerization of DMAEMA. The type II photoinitiators (benzophenone and IRGACURE® 500), which initiate DMAEMA photopolymerization through an H‐abstraction mechanism involving an amino group from the monomer (polymer), are less efficient and favor the formation of partly crosslinked products. The effects of the photoinitiator concentration, temperature, and solvent on the kinetic data are evaluated and discussed. A scheme of photopolymerization of DMAEMA, including the formation of intermediate DMAEMA based macromonomers, is proposed. The main point of the suggested scheme is a high chain transfer to the DMAEMA monomer. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 579–588, 2002     

Mesh‐independent p‐orthotropic enrichment using the generalized finite element method

This paper is aimed at presenting a simple yet effective procedure to implement a mesh‐independent p‐orthotropic enrichment in the generalized finite element method. The procedure is based on the observation that shape functions used in the GFEM can be constructed from polynomials defined in any co‐ordinate system regardless of the underlying mesh or type of element used. Numerical examples where the solution possesses boundary or internal layers are solved on coarse tetrahedral meshes with isotropic and the proposed p‐orthotropic enrichment. Copyright © 2002 John Wiley & Sons, Ltd.     

Thermodynamic analysis of the refining of technical boron nitride

The efficiency of the process of refining technical boron nitride was assessed based on calculations of the chemical equilibrium in the B-N-O-C-Cl-H system. Three refining mixtures, CCl₄ + H₂, CCl₄ + NH₃ and CHCl₃ + NH₃, were considered. The analysis indicates that the use of ammonia-containing mixtures is more convenient, a lower residual oxygen content, lower contamination of the product by carbon and a better overall boron balance emerging. The calculations of the equilibrium composition of the solid phase enabled suitable technological conditions of the refining process (temperature and starting composition of the gaseous phase) to be established. The calculated results are compared with experimental data, and some observed differences are discussed.