Search

In this paper we will derive a nonlocal ("integral") equation which transforms a three-dimensional acoustic transmission problem with variable coefficients, nonzero absorption, and mixed boundary conditions to a nonlocal equation on a "skeleton" of the domain Ω ⊂ R³, where "skeleton" stands for the union of the interfaces and boundaries of a Lipschitz partition of Ω. To that end, we introduce and analyze abstract layer potentials as solutions of auxiliary coercive full space variational problems and derive jump conditions across domain interfaces. This allows us to formulate the nonlocal skeleton equation as a direct method for the unknown Cauchy data of the solution of the original partial differential equation. We establish coercivity and continuity of the variational form of the skeleton equation based on auxiliary full space variational problems. Explicit expressions for Green's functions is not required and all our estimates are explicit in the complex wave number. [ABSTRACT FROM AUTHOR]

A viaduct in a high-speed railway line experienced severe heave of its central pillars as a result of deep expansion of an anhydrite rock. Bridge pillars were founded on pile groups that experienced vertical heave displacements as well as lateral displacements and rotations. A semi-analytical solution for the response of a pile group under loading and arbitrary located soil expansion was developed, integrating fundamental solutions for the elastic half-space. The procedure was first validated and then applied to explain the recorded behaviour of the pile groups. The deep expansion was identified from independent surface heave and continuous extensometer readings. Group rotations were well predicted. Observed tensile fissures at the cap- pile contact were explained by the calculated forces and moments on the piles. Key words: pile groups, heave, case history, analytical solutions, anhydritic claystone. Un viaduc situe sur le parcours d'une ligne ferroviaire a grande vitesse a presente un soulevement important des piliers centraux, consequence de l'expansion en profondeur d'une roche riche en anhydrite. Les piliers du pont ont ete construits sur des ensembles de pieux ayant subi des soulevements verticaux ainsi que des deplacements lateraux et des rotations. On a mis au point une methode semi-analytique appliquee a la reponse d'un ensemble de pieux soumis a un chargement et a l'expansion aleatoire et localisee du sol, methode qui integre les solutions fondamentales utilisees dans le cas d'un demi-espace elastique. La procedure a d'abord ete validee, puis appliquee afin d'expliquer le comportement observe des ensembles de pieux. L'expansion en profondeur a ete determinee a partir de soulevements de surface independants et de mesures continues effectuees au moyen d'un extensometre. Les rotations des ensembles de pieux ont ete correctement predites. Les fissures de tension observees a l'interface pieu-tete de pieu ont ete expliquees a l'aide des forces et moments calcules sur les pieux. [Traduit par la Redaction] Mots-cles: ensembles de pieux, soulevement, antecedents, solutions analytiques, argile a anhydrite., Introduction Soon after construction, a railway bridge, whose pillars were founded on 3 x 3 large-diameter (1.65 m) bored piles, experienced a sustained heave of its central spans. The geological [...]

Nuclear receptors (NR) are ligand-activated transcription factors that regulate different metabolic pathways by influencing the expression of target genes. The current study examined mRNA abundance of NR and NR target genes at different sites of the gastrointestinal tract (GIT) and the liver of healthy dogs (Beagles; n = 11). Samples of GIT and liver were collected postmortem and homogenized, total RNA was extracted and reverse transcribed, and gene expression was quantified by real-time reverse-transcription PCR relative to the mean of 3 housekeeping genes ([beta]-actin, glyceraldehyde-3-phosphate dehydrogenase, and ubiquitin). Differences were observed (P [less than or equal to] 0.05) in the mRNA abundance among stomach (St), duodenum (Du), jejunum (Je), ileum (I1), and colon (Col) for NR [pregnane X receptor (Du, Je > I1, Col > St), peroxisome proliferator-associated receptor [gamma] (St, Du, Col > Je, I1), constitutive androstane receptor (Je, Du > I1, Col), and retinoid x receptor a (Du > I1)] and NR target genes [glutathione-S-transferase A3-3 (Du > Je > St, I1; St > Col), phenol-sulfating phenol sulfotransferase 1A1 (Du, Je > I1, St; Col > St), cytochrome P450 3A12 (Du, Je > St, I1, Col), multiple drug resistance gene 1 (Du, Je, I1, Col > St), multiple drug resistance-associated protein 2 (Je, Du > I1 > St, Col), multiple drug resistance-associated protein 3 (Col > St > I1; Du > Je, I1; St > I1), NR corepressor 2 (St > I1, Col), and cytochrome P450 reductase (St, Du, Je > I1, Col)], but not for peroxisome proliferator-associated receptor [alpha]. Differences (P > 0.05) in mRNA abundance in the liver relative to the GIT were also observed. In conclusion, the presence of numerous differences in expression of NR and NR target genes in different parts of the GIT and in liver of healthy dogs may be associated with location-specific functions and regulation of GIT regions. Key words: canine, gastrointestinal tract, liver, nuclear receptor, nuclear receptor target gene, reverse-transcription polymerase chain reaction