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Strain and stress build-up in He-implanted UO2 single crystals: an X-ray diffraction study

The strain and stress build-up in 20-keV He-implanted UO₂ single crystals have been determined by means of X-ray diffraction through reciprocal space mapping, with the use of a model dedicated to the analysis of the strain/stress state of ion-irradiated materials. Results indicate that the undamaged part of the crystals exhibits no strain or stress; on the other hand, the implanted layer undergoes a tensile strain directed along the normal to the surface of the crystals and a compressive in-plane stress. The build-up of both strain and stress with He fluence exhibits a two-step process: (i) a progressive increase up to a maximum level of ~1% for the strain and ~−2.8 GPa for the stress, followed by (ii) a dramatic decrease. The origin of the strain and stress build-up is the formation of both self-interstitial defects and small He-vacancy clusters. The strain, and stress relief is tentatively attributed to the formation of extended defects (such as dislocations) that induce a plastic relaxation.     

Surface hydrolysis of postconsumer polyethylene terephthalate to produce adsorbents for cationic contaminants

In this work, the surface hydrolysis of postconsumer polyethylene terephthalate (PET) was used to produce an ion exchange material to adsorb cationic contaminants from water. The PET surface hydrolyses were carried out in neutral, alkaline, and acid media (NaOH or HNO₃ at 7, 10, and 15 mol L^?1) under reflux producing surface carboxylic acid sites (? COOH) characterized by ATR‐IR, pyridine adsorption, titration, TG, and DSC analyses. Acid hydrolysis produced high concentrations of ? COOH (up to 0.5 mmol g^?1_PET), whereas no significant concentration of carboxylic acid sites was obtained by neutral and alkaline hydrolysis. SEM analyses suggest that the acid sites are likely located at the cracks and defects produced on the PET surface by acid hydrolysis. Neutral or alkaline hydrolysis produced a very regular and smooth PET surface with very low acid site concentrations. The adsorption isotherms of Cd⁺² as a model of heavy metal and the dye methylene blue as a model of large organic cationic molecules showed high adsorption capacities for the HNO₃‐hydrolyzed PET, whereas no adsorption takes place on the neutral‐ or alkaline‐hydrolyzed polymer. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 5284–5291, 2006     

Novel regio- and stereoselective O-6-desulfation of the glucosamine moiety of heparin with N-methylpyrrolidinone-water or N,N-dimethylformamide-water mixtures

The degree of completeness and selectivity of the solvolytic O-6-desulfation reactions of the glucosamine moiety adjacent to the 2-O-sulfoiduronic acid group of heparin was systematically studied. Using solutions of various ammonium salts of heparin (salts of tributylamine, quinoline and pyridine) in mixtures of 9:1 aprotic solvents and water (solvents of medium polarity, in order of decreasing polarity: Me2SO > Me2NCHO > Me2NAc > N-methylpyrrolidinone), the influence of different reaction conditions were studied. The ammonium salt of heparin with a strong base (e.g., tributylamine) in Me2SO showed almost no desulfation, while in Me2NCHO a relatively low degree of completeness of O-6-desulfation (30%) with moderate selectivity (15% [I-2(OS)]-desulfation) was observed. Weak bases like quinoline or pyridine in Me2SO-water resulted in nearly complete [A-6(OS)]-desulfation (95 and 94%, respectively) with low selectivity [I-2(OS)]-desulfation (49 and 35%, respectively). The heparin pyridinium salt in Me2NCHO-water showed both a relatively high degree of completeness and high selectivity (72% [A-6(OS)]- and 8% [I-2(OS)]-desulfation). The highest regioselectivity (i.e., a high degree of completeness accompanied by high selectivity) was achieved using an N-methylpyrrolidinone-water mixture (88% [A-6(OS)]-desulfation and 10% [I-2(OS)]-desulfation). A nearly complete O-6-desulfation (95%), accompanied by a lower selectivity (18% [I-2(OS)]-desulfation), was achieved when the reaction was carried out twice. Lower temperature improved selectivity (5% [I-2(OS)]-desulfation) but reduced the completeness of [A-6(OS)]-desulfation (72%). In comparison with the variety of O-6-desulfations reported to date, the novel reactions presented in this article led to remarkable increase in completeness and regioselectivity of the reactions that were investigated.     

Attention and achievement exhibited by middle- and lower-class Black and White elementary school boys.

In-class behaviors of 80 7-8 yr old boys equally divided by race (Black and White) and social class (middle and lower) were recorded. Ss were administered the Peabody Picture Vocabulary Test, the Raven Coloured Progressive Matrices, and the Test of Basic Experience. The 3 observers compiled and used a list of behaviors judged to be all-inclusive of what occurs in normal classroom activity. No differences were found between groups in percentage of time attending. Although there were social class and race differences in achievement and intelligence test scores, no relationship was found between attending and these variables. Finally, there was a significant correlation between the intelligence and achievement test scores but no evidence that the relationship was different for the different groups. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Motor Protection Characteristics of Ambient Insensitive Overload Devices

The performance of thermal overload devices with respect to the effect of ambient sensitivity factors on motor winding insulation temperatures is investigated. It is shown that ambient sensitivity characteristics must be defined in order to optimize output horsepower while maintaining insulation temperatures within design parameters.     

Selection of Materials for Pressure Vessels and Chemical Plants

The selection of materials for pressure vessels and chemical plants depends on a number of factors such as operating pressure, operating temperature, operating medium, regulations in force in the country of the plant user concerned and manufacturing possibilities. The essay clearly explains how the above specified factors individually influence the selection of materials. The article also deals with the ranges of application of certain material groups such as unalloyed and low-alloy steels, fine-grained steels, austenitic chromium-nickel steels, unalloyed ferritic chromium steels and other materials. The article closes with remarks on the operational safety of pressure vessels.