Effect of clustering of precipitates on grain growth

The present work shows that clustering of particles promotes deviation in the classical mathematical expressions describing the grain growth control by second-phase particles. On the basis of experimental results and theoretical laws, a semiempirical expression to predict the limiting grain size is presented. The latter expression takes account of agglomeration phenomena and can be extended to large volume fractions of particles, conditions under which classical theories clearly fail. The equation remains valid as far as the nucleation of precipitates takes place at random. From a practical point of view, it is shown that volume fractions larger than 0.12 cannot significatively control the grain size because of the increased probability for clustering.     

Performance assessment through bootstrap

A new performance evaluation paradigm for computer vision systems is proposed. In real situation, the complexity of the input data and/or of the computational procedure can make traditional error propagation methods infeasible. The new approach exploits a resampling technique recently introduced in statistics, the bootstrap. Distributions for the output variables are obtained by perturbing the nuisance properties of the input, i.e., properties with no relevance for the output under ideal conditions. From these bootstrap distributions, the confidence in the adequacy of the assumptions embedded into the computational procedure for the given input is derived. As an example, the new paradigm is applied to the task of edge detection. The performance of several edge detection methods is compared both for synthetic data and real images. The confidence in the output can be used to obtain an edgemap independent of the gradient magnitude     

Interventricular communication in the neonatal period]

Fe(II)-tetrakis-N,N,N',N'(2-pyridylmethyl) ethylenediamine (Fe-TPEN) catalyzes the dismutation of superoxide, and blocks the toxic effect of paraquat on Escherichia coli growth and survival. We examined antioxidative effects of Fe-TPEN on lipid peroxidation and t-butyl hydroperoxide induced cell damage. Fe-TPEN inhibited the FeSO4/H2O2 induced lipid peroxidation in the rat liver homogenates with an IC50 value of 30.2 microM, and protected Ac2F cell damage by t-butyl hydroperoxide in a dose-dependent manner (EC50 value is 2.6 microM). Also, hepatoprotective effect of Fe-TPEN (5 mg/kg, i.p.) was investigated using CCl4 induced liver injury in rats. This complex inhibited the elevation of serum alanine aminotransferase (AST) and aspartate aminotransferase (ALT) levels in CCl4 induced liver injuries, and improved submassive necrosis and fatty degeneration of the hepatocytes. Fe-TPEN also prevented the loss of total and nonprotein SH contents, glutathione peroxidase and glutathione-S-transferase activity in cytosol of rat liver. Although the exact mechanism of action is not clear, antioxidative properties as well as attenuation of hepatocellular defense systems by Fe-TPEN seem to be important on its potent hepatoprotective effect in CCl4-intoxicated rat.     

Thermal Stress Analysis in Particulate Composite Components

Abstract: Thermal stresses resulting from flow of hot and cold water were obtained in sinks manufactured with acrylic casting dispersions by both experimental and numerical analysis. The experimental work was performed in two poly(methyl methacrylate) (PMMA) -silica based particulate composites, compositions of which are different by the volume fraction of filler and the particle size. The thermal stresses in sinks were obtained using strain gauges. The alternate flow of cold and hot water using a mixed tap, results in the formation of thermal gradients, leading to the occurrence of thermal stresses . The experimental results were compared with the numerical results obtained with a commercial finite element software. For this analysis, some thermal parameters such as the convective heat transfer coefficient, the density, the thermal conductivity and the specific heat were experimentally obtained. In general, a good agreement between experimental and numerical results was observed. The results of this study, together with the results of fatigue and fracture tests, will be used in a tolerance analysis of defects in the products manufactured with these composites.     

Addition of cashew tree gum to maltodextrin-based carriers for spray drying of cashew apple juice

This study involved an attempt to totally or partially replace maltodextrin DE10 (MD10) by cashew tree gum (CTG) as a drying aid agent in spray drying of cashew apple juice. The objective was to evaluate the impact of drying aid/cashew apple juice dry weight ratio (D/C, ranging from 3 to 5) and degree of replacement of MD10 with CTG (CTG_R, ranging from 0% to 100%) on ascorbic acid retention (AAR), hygroscopicity, flowability and water solubility of spray dried cashew apple juice powder. AAR was increased from 72.90% to 95.46% by increasing D/C from 3 to 5. CTG was shown as a promising maltodextrin replacer, being more effective than the latter to decrease powder hygroscopicity. The most adequate drying conditions (D/C = 5, CTG_R≥50%) resulted in more than 90% of AAR, and produced a powder with good flowing properties and water solubility.     

Magnetite nanoparticles: Electrochemical synthesis and characterization

Magnetite (Fe₃O₄) nanoparticles (NP) with sizes between 20 and 30 nm have been obtained by Fe electrooxidation in the presence of an amine surfactant, which acted as a supporting electrolyte and coating agent, controlling particle size and aggregation during the synthesis. The effect of different parameters on the nature and size of the particles as well as the mechanism of formation of the particles have been studied by different techniques. It was concluded that, under the electrochemical conditions used in this work, the NP mean size was found to be constant at around 20 nm when the electrooxidation current density is increased from 10 to 200 mA cm⁻². However, when the potential is over 6 V, particle size decreases from 30 to 20 nm and metallic iron appears as an impurity. The mechanism of particles formation has being clarified and the critical effect of the distance between electrodes for obtaining magnetic iron oxide nanoparticles has been understood. Finally, the presence of an electrostatic adsorbed surfactant coating the particles allows the functionalization of the particles easily by exchange reaction with biomolecules of interest, which makes this material very promising for future application in biotechnology.     

Precision area measurements determine fundamental physical constants

We describe an experiment now underway to measure the ratio of the atomic constants h/m (Planck's constant divided by the electron mass). It is based on several remarkable properties of rotating superconducting rings. Accuracies approaching one part per million or better are made possible by recent technological advances in superconductive devices and dimensional metrology. The crucial cross-sectional area measurements presented in this paper will make possible the observation of relativistic electron mass corrections for the first time in a solid state physics measurement     

West's syndrome associated with inversion duplication of chromosome 15

We describe a five year old boy with inversion duplication of chromosome 15 (inv dup (15)) who, at the age of six months had started to develop West's syndrome. He later developed cryptogenic myoclonic epilepsy which was resistant to medication. On examination there was dysmorphia, overall hypotonia and diffuse pyramidalism. On starting ACTH the crises of flexion spasms were reduced but these were soon followed by myoclonic crises, both tonic and atonic, which did not respond to the various anticonvulsive treatments given. We comment on the changes in chromosome 15 linked to convulsions, and particularly the phenotypes of the inv dup (15) which depend on the size and genetic composition of the anomaly. This is the third case described in the literature of a patient with West's syndrome associated with supernumerary inversion duplication of chromosome 15. It is suggested that the karyotype be included when studying convulsive encephalopathies and cryptogenic refractory epilepsy, especially in infantile spasms.     

Effect of immediate and delayed post preparation on apical dye leakage using two different sealers

Eighty freshly extracted teeth were endodontically prepared and filled with gutta-percha and either a zinc oxide-eugenol-based sealer or AH26 to determine what effect these sealers, with widely differing properties, would have on apical microleakage after either immediate or delayed dowel space preparation. The teeth were randomly assigned to 1 of 4 groups, and the post space was made either immediately after filling or after being stored in 100% humidity for 1 wk. They were then immersed in a 2% methylene blue solution under vacuum, washed, and split longitudinally. The extent of dye penetration was read by five independent observers and the results analyzed. The only significant difference was in the delayed preparation group with zinc oxide-eugenol sealer, which showed greater leakage than the other groups.