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Bicrystals of Al2 O3 were fabricated to study the effects of thermal expansion anisotropy on fracture in a model system containing one grain boundary. Fractures occurred perpendicular to the directions of maximum tensile stress in bicrystals with thermal expansion coefficient differences as low as 0.31×10−60 C−1 and originated at the boundary, probably in areas of high residual stress associated with pores. Numerical stress analysis of two-dimensional model bicrystal configurations showed that stresses induced by thermal expansion anisotropy are maximal in a region localized along the bicrystal boundary. 相似文献
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RICARDO J. GRAU MARÍA I. CABRERA ALBERTO E. CASSANO 《Chemical Engineering Communications》2013,200(1):229-257
Design equations for non-isothermal Laminar Flow Tubular Reactors (LFTRs) with homogeneous and heterogeneous - at the reactor wall - reactions with arbitrary kinetic equations have been satisfactorily treated transforming the original P.D.E. problem into a system of integral equations. The kernels of the integral operators are related to an eigenvalue problem which does not depend on the kinetic equations; this avoids repetitive computational effort in the treating of different reaction kinetics. To render a more efficient numerical treatment and according to the governing reaction rate regime, modified expressions of the general solution were obtained was follows: (i) a solution with kernels depending only on the diffusion and convective times was obtained for a low reaction regime; (ii) another solution with kernels including the reaction lime, besides the diffusion and convective ones, was necessary for a fast reaction regime and (iii) the local quasi-steady-state approximation was obtained as limiting case of solution (ii) for a instantaneous reaction regime. 相似文献
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ÁNGEL ALEGRÍA MARÍA ELENA FERNÁNDEZ SUSANA DELGADO BALTASAR MAYO 《International Journal of Dairy Technology》2010,63(3):423-430
This work reports the microbial characterisation of a farmhouse natural fermented milk (NFM) with good sensorial properties produced in Spain. Culturing and denaturing gradient gel electrophoresis (DGGE) analyses showed thatLactococcus lactissubsp.lactis and L. lactissubsp.cremoris(approximate levels of 109 cfu/mL) were dominant in this NFM, whileLactobacillus plantarumappeared at a lower level (106–107 cfu/mL). Repetitive extragenic palindromic (REP)‐PCR typing of the isolates identified single strains each ofLc. lactissubsp.lactis, Lc. lactissubsp.cremorisandLb. plantarum. These three strains formed a stable microbial association which has been maintained for at least some decades. 相似文献
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The widespread Mexican apple snail Pomacea flagellata (Say 1827) and the strictly endemic
"tegogolo" P. patula catemacensis (Baker 1922) (restricted to Lake Catemaco), are the only known American
Ampullariidae that have haploid complements n=13. Pomacea patula catemacensis has suffered a critical
reduction in abundance due to immoderate fishing for human consumption. Chromosome slides were obtained from colchicine-injected Pomacea snails collected from nine locations along the coastal zone of the
Gulf of Mexico, including Lake Catemaco, for use in principal component analysis (PCA). Total proteins in
foot homogenates were analyzed through isoelectric focusing (IEF) and native-PAGE electrophoresis on polyacrylamide gels. The chromosome number 2n=26 was confirmed for snails from all locations, with a uniform
9 m + 4 sm formula. However, P. patula catemacensis showed significantly larger chromosomes (absolute
size) than any population of P. flagellata. Pomacea patula catemacensis also differed from all populations of
P. flagellata in a PCA with standardized data, i.e., independently of the absolute size difference between
species. Proteins with an acid isoelectric point were dominant in the foot of both species. The electrophoresis
analysis showed that P. flagellata has 17 protein bands, with an upper bound at IEF=7.6, while P. patula
catemacensis has only 15 bands, with an upper bound at IEF=7 and a more evenly spaced band pattern.
Molecular weights ranged from 40 to approximately 130 kDa in both species. Proteins with high values (>94
kDa) were the most abundant. Pomacea patula catemacensis showed a band of 93 kDa, which was absent
from all specimens of P. flagellata. Samples of P. flagellata did not cluster according to any geographical
pattern in the statistical analyses, nor did they show any taxonomically useful differences in their electrophoretic patterns that merit sub-specific discrimination. 相似文献