23 research outputs found
Dimensional Crossover in the Effective Second Harmonic Generation of Films of Random Dielectrics
The effective nonlinear response of films of random composites consisting of
a binary composite with nonlinear particles randomly embedded in a linear host
is theoretically and numerically studied. A theoretical expression for the
effective second harmonic generation susceptibility, incorporating the
thickness of the film, is obtained by combining a modified effective-medium
approximation with the general expression for the effective second harmonic
generation susceptibility in a composite. The validity of the thoretical
results is tested against results obtained by numerical simulations on random
resistor networks. Numerical results are found to be well described by our
theory. The result implies that the effective-medium approximation provides a
convenient way for the estimation of the nonlinear response in films of random
dielectrics.Comment: 9 pages, 2 figures; accepted for publication in Phys. Rev.
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On the embrittlement of Zircaloy-4 under RIA-relevant conditions.
The extended use of Zircaloy cladding in light water reactors degrades its mechanical properties by a combination of irradiation embrittlement, coolant-side oxidation, hydrogen pickup, and hydride formation. The hydrides are usually concentrated in the form of a dense layer or rim near the cooler outer surface of the cladding. Utilizing plane-strain ring-stretch tests to approximate the loading path in a reactivity-initiated accident (RIA) transient, we examined the influence of a hydride rim on the fracture behavior of unirradiated Zircaloy-4 cladding at room temperature and 300 C. Failure is sensitive to hydride-rim thickness such that cladding tubes with a hydride-rim thickness >100 {micro}m ({approx}700 wppm total hydrogen) exhibit brittle behavior, while those with a thickness <90 {micro}m ({approx}600 wppm) remain ductile. The mechanism of failure is identified as strain-induced crack initiation within the hydride rim and failure within the uncracked ligament due to either a shear instability or damage-induced fracture. We also report some preliminary results of the uniaxial tensile behavior of low-Sn Zircaloy-4 cladding tubes in a cold-worked, stress-relieved condition in the transverse (hoop) direction at strain rates of 0.001/s and 0.2/s and temperatures of 26-400 C
Lavagem traqueobrônquica por sondagem nasotraqueal em bezerros Tracheobronchial lavage in calves using a nasotracheal technique
Avaliou-se a técnica de lavagem traqueobrônquica por sondagem nasotraqueal e caracterizou-se a população celular em 10 bezerros clinicamente sadios. Após a contenção dos animais em decúbito lateral e auxÃlio de sonda guia, foi introduzida uma sonda de menor diâmetro até a bifurcação da traquéia, para produzir tosse e obter o lavado traqueobrônquico. A média de células totais nas amostras de lavado foi de 133.750 células/ml. À citologia, foram observados na contagem diferencial: 77,2% macrófagos, 14,9% células epiteliais cilÃndricas, 6,0% neutrófilos e 1,8% linfócitos. Das células epiteliais cilÃndricas, 79,0% eram do tipo ciliadas e 21,0% não-ciliadas. A média de contagem de macrófagos binucleados foi de 78,5 células/lâmina, a de macrófagos trinucleados de 20,5/lâmina e a de células gigantes 28,5/lâmina. Concluiu-se que o método de colheita por sondagem nasotraqueal é eficiente para caracterizar a citologia do lavado traqueobrônquico de bezerros clinicamente sadios.<br>Tracheobronchial lavage through nasotracheal via was performed in 10 clinically health calves. They were maintained in lateral recumbence to perform the procedure. A small tube inserted into a guide tube was introduced until the tracheal bifurcation, producing cough, facilitating the collection of the lavage fluid. The mean number of total cells present in the samples was 133,750 cells/ml. The differential counting was represented by 77.2% of macrophages, 14.9% of cylindrical epithelial cells, 6.0% of neutrophils, 1.8% of lymphocytes. The cylindrical ciliated cells represented 79.0% of the sample and the nonciliated cells represented 21.0%. The mean number of macrophages was 78.5 of binucleated cells, 20.5 of trinucleated cells, and 28.5 of giant cells per smear. The tracheobronchial lavage obtained by this technique was an efficient method to characterize the cytological population of the lungs of clinically health calves