A parameter for quantitative analysis of plasticity induced crack closure

Numerical models have been successfully developed to predict plasticity induced crack closure (PICC). However, despite the large research effort a full understanding of the links between physical parameters, residual plastic wake and PICC has not been achieved yet. The plastic extension of material behind crack tip, Δyp, obtained by the integration of vertical plastic deformation perpendicularly to crack flank, is proposed here to quantify the residual plastic field. The values of Δyp and PICC were obtained numerically in a M(T) specimen using the finite element method. An excellent correlation was found between PICC and Δyp which indicates that this parameter controls the phenomenon, and can be used to quantify the effect of physical parameters. An empirical model was developed to predict PICC assuming that the residual plastic field is a set of vertical plastic wedges, that the linear superposition principle applies and that the influence of a particular wedge exponentially decreases with distance to crack tip. The model was applied successfully to predict PICC for different residual plastic fields which provided an additional validation of Δyp as the parameter controlling PICC

Benzo[a]pyrene and beta-naphthoflavone mutagenic activation by European eel (Anguilla anguilla L.) S9 liver fraction

Is Anguilla anguilla L. (eel) liver ethoxyresorufin O-deethylase (EROD) induction absolutely necessary in order to convert promutagens as benzo[a]pyrene (BaP) into a mutagenic compound? Eels were exposed for 8 h to clean (control) and 0.3 microM beta-naphthoflavone (BNF)-contaminated water. The 8-h exposure to 0.3 microM BNF brought about a very high EROD induction (10 pmol/min/mg protein) compared to control animals (1 pmol/min/mg protein). The Ames test (Maron and Ames, 1983) was carried out with Salmonella typhimurium TA 98 strain (TA98 His-) and eel isolated S9 liver fraction was used as a metabolic BaP activator. The BaP and BNF dose range concentrations tested were 0 (blank), 0.015, 0.08, 0.15, 0.38, 0.75, 1.5, 3.8, and 7.5 microM/plate and 0 (blank), 0.412, 1.235, 3.704, 11.1, 33.0, and 100 nM BNF, respectively. A dose-response relationship between BaP concentration and mutagenic activity was observed in the presence of S9 fractions in control and 0.3 microM BNF-exposed eels. Significant positive results, as TA98 His+ revertants, were observed at 0.38, 0.75, 1.5, 3.8, and 7.5 microM BaP/plate induced by BNF S9 fractions. Significant BaP mutagenic activation by liver control S9 was detected only at 1.5, 3.8, and 7.5 microM/plate. The BaP 1.5, 3.8, and 7.5 microM/plate mutagenic activation by BNF S9 and control S9 were not significantly different. Relative to BNF activation, it was only possible to detect His+ reversion at 11.1 nM BNF concentration with 0.3 microM BNF-induced S9. The above results demonstrate that the eel S9 liver fraction has the capacity to biotransform high BaP concentrations and convert it into a mutagenic compound with or without previous liver BNF biotransformation induction. The same does not apply to low BaP concentrations, where liver S9 induction by BNF is necessary to promote mutagenesis.publishe

Genotoxic and biochemical responses in caged eel (Anguilla anguilla L.) after short-term exposure to harbour waters

European eel (Anguilla anguilla L.) were caged and exposed in situ for 8 and 48 h to the Aveiro offward fishing harbour water (HW) and to clean seawater under laboratory conditions (Control). Eel liver biotransformation (Phase I) was measured as ethoxyresorufin-O-deethylase (EROD) activity, cytochrome P450 (P450) and glutathione S-transferase (GST) activity (Phase II). Genotoxic responses were determined as blood, liver and kidney DNA strand breaks as well as erythrocytic nuclear abnormalities (ENAs). HW failed to significant increase liver EROD, GST activities and ENA frequency. Nevertheless, P450 content was significantly increased after 8 and 48 h exposure. Genotoxicity measured as DNA integrity decrease was found in blood after 8 and 48 h exposure to HW, whereas in liver and kidney, it was observed after 48 h exposure to HW. Blood, kidney and liver genotoxicity may be due to the presence of polycyclic aromatic hydrocarbons (PAHs) which are genotoxic compounds and the main HW organic contaminants.publishe

Heartwood formation and durability of the wood of plantation grown tree species of the central Amazon.

In this study the heartwood formation and the durability of seven years old plantation grown mogno, andiroba, cedro, cumaru, and jatoba was compared with wood from primary growth, in Manaus-AM (Brasil). The results are discussed with special regard to wood quality of plantation grown trees compared to primary growth

Espectrometría de rayos gamma: Aplicaciones a las facies orgánicas carbonatadas del Sinemuriense–Pliensbachiense de la Cuenca Lusitánica (Portugal)

This work provides detailed information of outcrop gamma-ray logging from the Sinemurian–Pliensbachian organic-rich units (Água de Madeiros and Vale das Fontes formations) of the Lusitanian Basin, which are recognized as one of the most important potential oil source rocks interval of Portugal. The study included total and spectral gamma-ray measurements in outcrop and laboratory, Total Organic Carbon (TOC) content and whole-rock mineralogical characterization by X-ray diffraction, carried out in the two most important outcrop areas of the Western Lusitanian Basin (S. Pedro de Moel and Peniche). The outcrop data was compared with subsurface information. The results show high variability of the gamma radiation (26 to 210 cps) and radioactive elements associated with the lithological, mineralogical and geochemical differences. The TOC data yielded the organic matter enrichment of both formations, where the highest values are observed in the Água de Madeiros Formation (maximum=20.4%). The highest U concentration (11 ppm) is consistent with the highest Total Organic Carbon peak mainly supported by the precipitation of authigenic U (10 ppm). The majority of the analysed samples show an obvious authigenic U enrichment, especially in the Água de Madeiros Formation where it represents the main component of the total U content. A highly significant U/TOC correlation (r up to 0.87) with a low ratio (0.3–0.7 ppm/wt.%TOC) was obtained, confirming that U content can be used as a proxy for organic richness in the studied depositional system. The gamma-ray tool was also useful in the identification of 2nd order Transgressive–Regressive facies cycles (and maximum flooding surfaces) and in the correlation between outcrop and subsurface data.Este trabajo proporciona información detallada de espectrometría de rayos gamma de las unidades ricas en materia orgánica del Sinemuriense–Pliensbachiense de la Cuenca Lusitánica, reconocidas como los depósitos con más potencial para generar petróleo en Portugal. El estudio incluye mediciones de espectrometría de rayos gamma en afloramiento y laboratorio, cuantificación del carbono orgánico total (COT) y caracterización mineralógica por difracción de rayos X, llevada a cabo en dos áreas de la Cuenca Lusitánica (S. Pedro de Moel y Peniche). Los datos de afloramiento se han comparado con información de pozos. Los resultados muestran una alta variabilidad de la radiación gamma (26 a 210 cps), de los elementos radioactivos asociados a las distintas litologias, y de las características mineralógicas y geoquímicas. Los datos de COT evidencian un enriquecimiento en materia orgánica de toda la secuencia estudiada, en particular de la Formación de Água de Madeiros (máximo=20.4%). La concentración más elevada de U (11 ppm) es consistente con el pico principal de COT causado por la precipitación de U autigénico (10 ppm). La mayoría de las muestras analizadas presentan un marcado enriquecimiento en U autigénico, especialmente en la Formación de Água de Madeiros que representa el principal componente del contenido total de U. Se ha obtenido una correlación U/COT muy significativa (que alcanza valores de r=0.87) con una proporción baja (0.3 a 0.7 ppm/%COT), lo que confirma que el valor de la concentración de U puede ser utilizado para calcular el contenido en materia orgánica en el sistema deposicional estudiado. La técnica de rayos gamma también ha sido útil en la identificación de ciclos Transgressivo-Regressivos de 2º orden, de superficies de máxima inundación y en la correlación de datos de superficie con datos de pozos

Percolative phase transition on ferromagnetic insulator manganites: uncorrelated to correlated polaron clusters

In this work, we report an atomic scale study on the ferromagnetic insulator manganite LaMnO$_{3.12}$ using $\gamma-\gamma$ PAC spectroscopy. Data analysis reveals a nanoscopic transition from an undistorted to a Jahn-Teller-distorted local environment upon cooling. The percolation thresholds of the two local environments enclose a macroscopic structural transition (Rhombohedric-Orthorhombic). Two distinct regimes of JT-distortions were found: a high temperature regime where uncorrelated polaron clusters with severe distortions of the Mn$^{3+}$O$_{6}$ octahedra survive up to $T \approx 800 K$ and a low temperature regime where correlated regions have a weaker JT-distorted symmetry.Comment: 4 pages, 4 Figures, submitted to PRL, new version with more data, text reformulate

Contribuição do colmo principal na qualidade de grãos de duas cultivares de arroz (Oryza sativa L.), em comparação aos perfilhos.

Este trabalho teve como objetivo avaliar a contribuição do colmo principal na qualidade de grãos, de duas cultivares de arroz, em comparação aos perfilhos

Phytosociological surveys: tools for weed science?

Made available in DSpace on 2014-03-07T23:23:12Z (GMT). No. of bitstreams: 1 germaniplanta.pdf: 1437590 bytes, checksum: 2518af349217cec531443f69ffd935f2 (MD5) Previous issue date: 2013-11-08201

Fatores que diferenciam os resultados economicos dos colonos: o caso do perimetro irrigado de Bebedouro.

O Submedio Sao Francisco vem conhecendo, nos ultimos vinte anos, um desenvolvimento consideravel gracas, principalmente, a agricultura irrigada. Nas areas de irrigacao publica onde foram assentados um grande numero de familias de baixa renda, esse desenvolvimento nao tem se dado de forma uniforme para todos os colonos e as razoes apresentadas sao diversas. No Perimetro Irrigado de Bebedouro, primeiro perimetro publico a ser instalado nessa regiao, a despeito de um numero de colonos apresentarem um bom desempenho economico, uma parcela significativa daqueles produtores nao tem evoluido como se esperava. Buscando conhecer as principais razoes que diferenciam esses dois grupos fez-se entrevistaa, com 108 (85,71%) dos 126 colonos ali existentes e atraves de analise estatistica, usando o teste "t" de Student, foram avaliadas as variaveis que mais diferiam estatisticamente onde se destacaram: tamanho da area irrigada, tamanho da area com cultivos perenes, area plantada com videira, produtividade da videira, quantidade de rebanho bovino, experiencia com agricultura irrigada, treinamento recebido e capacidade gerencial