Factors controlling Hg levels in two predatory fish species in the Negro river basin, Brazilian Amazon

A number of environmental factors have been shown to influence the dynamics of Hg in aquatic ecosystems. Here we investigate the influence of fish size, pH, dissolved organic carbon (DOC), and the availability of potential methylation sites (floodplain forests and hydromorphic soils) on the concentration of total Hg in two carnivorous fishes: Cichla spp. and Hoplias malabaricus in the Negro River, Brazil. Fish and water samples for chemical analysis were collected from 33 sites in the Negro basin. The percentage of alluvial floodplains and hydromorphic soils (potential methylation sites) in the drainage basin upstream from each sampling point was estimated from radar imagery and existing soil maps with GIS. The average of Hg concentrations were 0.337 ppm (SD = 0.244) in Cichla spp. and 0.350 ppm (SD = 0.250) in H. malabaricus. Although the study area was geographically isolated from most major anthropogenic Hg sources, over 18% of Cichla spp. and 29% of H. malabaricus had Hg concentrations above 0.5 ppm, indicating naturally high background levels of Hg. Hg concentrations increased with size in both Cichla spp. (r² = 0.664, p = 0.000) and H. malabaricus (r² = 0.299, p = 0.000). Hg concentrations in H. malabaricus also increased with percent floodable area (p = 0.006), pH (p = 0.000) and DOC (0,063). In Cichla spp, Hg increased only in relation to percent floodable area (p = 0.000). Hydromorphic soils did not influence fish Hg.     

A conservative nodal variational multiscale method for Lagrangian shock hydrodynamics

A new method based on a continuous, piece-wise linear approximation of the equations for Lagrangian shock hydrodynamics is presented. Numerical instabilities are controlled by a stabilizing operator derived using the paradigm of the variational multiscale analysis. Encouraging numerical comparisons with existing methods in the case of quadrilateral and hexahedral elements indicate that the proposed method is capable of preventing hourglass patterns in the solution, while maintaining accuracy in regions of smooth flow. The proposed approach satisfies Galilean invariance properties and hinges upon the interpretation of the Lagrangian shock hydrodynamics equations as a system of nonlinear wave equations. A specific implementation in terms of a predictor/multi-corrector version of the mid-point time integrator guarantees global conservation of mass, momentum, and total energy for each iterate. Stability and formal order of accuracy are investigated applying the von Neumann analysis to the linearized shock hydrodynamics equations in one dimension. This approach yields tight bounds for stable time-step estimation, formal second-order accuracy of the method in time and space, and valuable indications on the choice of the most appropriate values for the stabilization parameters present in the formulation.     

An Enhanced Vacuum Cure Technique for On-Aircraft Repair of Carbon-Bismaleimide Composites

Carbon/bismaleimide (BMI) composite is increasingly employed in critical load carrying aircraft structures designed to operate at temperatures approaching 180°C. The high post-cure temperature (above 220°C) required to fully react the BMI resin, however, renders existing on-aircraft prepreg or wet layup repair methods invalid. This paper presents a new on-aircraft repair technique for carbon/BMI composites. The composite prepregs are first warm-staged to improve the ability to evacuate entrapped air. Then the patch is cured in the scarf cavity using the vacuum bag technique, followed by off-aircraft post-cure. The fully cured patch then can be bonded using a structural adhesive.     

Bonded repairs for carbon/BMI composite at high operating temperatures

The increased use of carbon reinforced polymer composite structures in civilian and military aircraft has produced new challenges for on-aircraft bonded repairs. Carbon/bismaleimide (BMI) composite structure provides an added complexity associated with the application of adhesively bonded repairs. Commercially available carbon/BMI composite usually requires a post-cure temperature in excess of 220 °C to achieve the high strength properties at elevated operating temperatures. Application of bonded repairs in situ often places an upper limit on the temperatures that can be employed for curing the adhesive at 177 °C. Consequently, the adhesive bond needs to achieve similar mechanical properties to the parent matrix material without the benefit of the high post-cure temperature. The current work examines a range of repair options that can be used to recover strength and the selection of adhesives and processes to successfully apply the repairs using vacuum assisted pressure.     

Stable Inverted Polymer/Fullerene Solar Cells Using a Cationic Polythiophene Modified PEDOT:PSS Cathodic Interface

A cationic and water‐soluble polythiophene [poly[3‐(6‐pyridiniumylhexyl)thiophene bromide] (P3PHT⁺Br^?)] is synthesized and used in combination with anionic poly(3,4‐ethylenedioxythiophene):poly(p‐styrenesulfonate) (PEDOT:PSS)^? to produce hybrid coatings on indium tin oxide (ITO). Two coating strategies are established: i) electrostatic layer‐by‐layer assembly with colloidal suspensions of (PEDOT:PSS)^?, and ii) modification of an electrochemically prepared (PEDOT:PSS)^? film on ITO. The coatings are found to modify the work function of ITO such that it could act as a cathode in inverted 2,5‐diyl‐poly(3‐hexylthiophene) (P3HT)/[6,6]‐phenyl‐C₆₁‐butyric acid methyl ester (PCBM) polymer photovoltaic cells. The interfacial modifier created from the layer‐by‐layer assembly route is used to produce efficient inverted organic photovoltaic devices (power conversion efficiency ～2%) with significant long‐term stability in excess of 500 h.     

Aberrant expression of MUC5AC and MUC6 gastric mucin genes in colorectal polyps

Altered mucin glycosylation and the de novo appearance of gastric mucin antigens have been described in colonic adenomas. The purpose of our study was to determine if expression of the gastric mucin genes MUC5AC and MUC6 occurs in colorectal adenomas and whether this correlates with histopathologic criteria of malignant potential. Immunohistochemical staining using antibodies against MUC5AC and MUC6 tandem repeat synthetic peptides was performed on specimens of normal colon mucosa (n = 26), hyperplastic polyps (n = 9) and adenomatous polyps (n = 111). Mucin mRNA levels were determined using RNase protection assays using riboprobes corresponding to unique non-repetitive sequences. MUC5AC and MUC6 staining were rarely detected and of low intensity in normal colon and hyperplastic polyps. The number of immunoreactive polyps and intensity of MUC5AC and MUC6 staining were greatest in larger adenomas of moderate villous histology and dysplasia. MUC5AC and MUC6 staining tended to decrease in highly villous polyps with severe dysplasia. Increased MUC5AC mRNA levels were found in 26/45 of adenomas tested compared with 0/9 normal colon specimens. MUC6 mRNA levels were found in 20/45 of adenomas compared with 1/9 normal colon specimens. MUC5AC and MUC6 mRNA were present more frequently and at higher levels in polyps with intermediate stages of size, villous histology and dysplasia. We conclude that aberrant expression of MUC5AC and MUC6 mucin genes is likely responsible for an expanded repertoire of mucin antigen expression in colorectal neoplasia.     

Vibrio anguillarum resistance to rainbow trout (Oncorhynchus mykiss) serum: role of O-antigen structure of lipopolysaccharide

The sensitivity of Vibrio anguillarum to the bactericidal effect of rainbow trout serum was investigated with different strains of serogroups O1 and O2a, which are the most frequently found serogroups in clinical outbreaks of vibriosis. All of the V. anguillarum strains were able to activate complement in rainbow trout serum, but smooth strains of V. anguillarum serogroup O1 were resistant to complement-mediated killing in the absence of specific antibodies. In the case of V. anguillarum serogroup O2a strains, 80% of the analyzed strains were resistant to rainbow trout serum even when specific antibodies were present. Analysis of the lipopolysaccharide structures of the tested V. anguillarum strains showed a positive correlation between the O-antigen size of the lipopolysaccharide and resistance to serum killing. The classical complement pathway was responsible for the antibody-dependent serum killing of susceptible V. anguillarum strains. When serum-resistant V. anguillarum serogroup O2a strains were grown in glucose-enriched Lennox L broth, they produced lipopolysaccharide molecules with fewer high-molecular-weight O-antigen units than did strains grown in broth without the addition of glucose. Strains grown in glucose-enriched medium became sensitive to rainbow trout serum killing, indicating that the high-molecular-weight O-antigen side chains prevented the activated complement from damaging the bacterium.     

Pregnancy-associated glycoprotein and decreased polymorphonuclear leukocyte function in early post-partum dairy cows

High density lipoprotein (HDL) cholesterol levels can be used to predict cardiovascular disease risk in women. To better understand variability in HDL cholesterol levels, the authors examined the relation with three domains (body size and type, sex hormone status, and carbohydrate metabolism) in a cross-sectional population-based 1993-1994 study of 402 premenopausal women from Tecumseh, Michigan. They found that these domains explained 27% of the total variation in HDL cholesterol levels; waist-to-hip ratio was the term that explained the highest proportion of variability (6% after fat mass, sex hormone binding globulin, and insulin levels were added to the model). In analyses restricted to women whose body mass index was > or = 32 kg/m2, which constituted 19% of this population, neither body mass index nor fat mass was a significant predictor of variability in HDL cholesterol levels. Significant variables were insulin levels, waist-to-hip ratio, and smoking. This finding suggests that there is a saturation of the relation between increasing fat mass and lower HDL cholesterol levels, as evidenced by the lack of a relation between the two among the heaviest women. Meanwhile, among the heaviest women, increasing insulin levels and a higher waist-to-hip ratio remained predictors of low levels of HDL cholesterol.