Fórmulas estadísticas de resistencia al flujo para hidráulica fluvial

El empleo en hidráulica en lámina libre de las ecuaciones de resistencia al flujo de Gauckler-Manning o Darcy-Weisbach requiere la determinación de un coeficiente de resistencia; determinación que si bien es suficientemente precisa con un reducido esfuerzo y coste en cauces artificiales, resulta mucho más difícil y cara en ríos. Con objeto de eliminar la necesidad de una estimación independiente del coeficiente de resistencia se han desarrollado estadísticamente una serie de ecuaciones para flujo permanente y uniforme en ríos, en las que se prescinde de dicho coeficiente. El presente artículo pretende ser una revisión de las fórmulas de este último tipo más difundidas en la práctica de la hidráulica fluvial.

Flujo de energía en el ecosistema fluvial : análisis del metabolismo

Capítol 20 del llibre 'Conceptos y técnicas en ecología fluvial' que es refereix al metabolisme fluvial

Uso de ríos artificiales en ecología fluvial

Capítol 21 del llibre 'Conceptos y técnicas en ecología fluvial' que es refereix a la utilització dels rius artificials en ecologia fluvial

Relaciones tróficas en el ecosistema fluvial

Capítol 19 del llibre 'Conceptos y técnicas en ecología fluvial' que es refereix a les relacions tròfiques en l'ecosistema fluvial

Catalase in fluvial biofilms: a comparison between different extraction methods and example of application in a metal-polluted river

Antioxidant enzymes are involved in important processes of cell detoxification during oxidative stress and have, therefore, been used as biomarkers in algae. Nevertheless, their limited use in fluvial biofilms may be due to the complexity of such communities. Here, a comparison between different extraction methods was performed to obtain a reliable method for catalase extraction from fluvial biofilms. Homogenization followed by glass bead disruption appeared to be the best compromise for catalase extraction. This method was then applied to a field study in a metal-polluted stream (Riou Mort, France). The most polluted sites were characterized by a catalase activity 4–6 times lower than in the low-polluted site. Results of the comparison process and its application are promising for the use of catalase activity as an early warning biomarker of toxicity using biofilms in the laboratory and in the field

Fluvial biofilms: a pertinent tool to assess β-blockers toxicity

Among increasingly used pharmaceutical products, β-blockers have been commonly reported at low concentrations in rivers and littoral waters of Europe and North America. Little is known about the toxicity of these chemicals in freshwater ecosystems while their presence may lead to chronic pollution. Hence, in this study the acute toxicity of 3 β-blockers: metoprolol, propranolol and atenolol on fluvial biofilms was assessed by using several biomarkers. Some were indicative of potential alterations in biofilm algae (photosynthetic efficiency), and others in biofilm bacteria (peptidase activity, bacterial mortality). Propranolol was the most toxic β-blocker, mostly affecting the algal photosynthetic process. The exposure to 531 μg/L of propranolol caused 85% of inhibition of photosynthesis after 24 h. Metoprolol was particularly toxic for bacteria. Though estimated No-Effect Concentrations (NEC) were similar to environmental concentrations, higher concentrations of the toxic (503 μg/L metoprolol) caused an increase of 50% in bacterial mortality. Atenolol was the least toxic of the three tested β-blockers. Effects superior to 50% were only observed at very high concentration (707 mg/L). Higher toxicity of metoprolol and propranolol might be due to better absorption within biofilms of these two chemicals. Since β-blockers are mainly found in mixtures in rivers, their differential toxicity could have potential relevant consequences on the interactions between algae and bacteria within river biofilms

Capacidade de oxidação como índice de estabilidade da matéria orgânica de sedimentos de acordo com gradiente fluvial-estuarino do rio Paraíba do Sul

The hummus composition and it redox properties have been used to evaluate the organic matter quality from natural systems. The objectives of this study were the fractionation of the organic matter and the determination of the oxidation capacity of humic acids to evaluate the organic matter quality of sediments from a gradient fluvial-estuarine in the Brazilian Southeast. The carbon/nitrogen and humic acid/fulvic acid relationships of the organic matter and of the oxidation capacity of humic acids were positively correlated and followed the order: estuarine bordered mangroves ≅ fluvial bordered urban center and pasture > estuarine bordered pasture ≅ marine.

DISCRIMINAÇÃO PRIVADA E O SEGUNDO PRINCÍPIO DA JUSTIÇA DE RAWLS

RESUMO O artigo examina se há alguma incompatibilidade entre práticas de discriminação privada (por exemplo, a discriminação no emprego e em associações, como clubes) e as duas partes do segundo princípio da justiça de Rawls, o princípio da equitativa igualdade de oportunidades (PEIO) e o princípio da diferença (PD). Argumento que a discriminação no trabalho e em outras áreas importantes para o desenvolvimento das aptidões inatas (como a educação e a saúde) somente atenta contra o PEIO quando tem como efeito geral o de tornar substancialmente desiguais as chances de cidadãos com similares aptidões inatas e motivação exercerem determinadas ocupações. Comento também algumas dificuldades para considerar vedados pelo PEIO dois casos comuns de discriminação, a discriminação baseada em qualidade de reação e a discriminação por indicadores. Em relação ao PD, defendo que a proibição à discriminação privada se relaciona ao bem primário das bases sociais do autorrespeito e está circunscrita aos casos de discriminação degradante, como tal entendida, de acordo com Hellman (2008), aquela cujo sentido expressivo é o de negar o igual status moral das pessoas pertencentes a um certo grupo.

Justiça e desenvolvimento no pensamento de Amartya Sen

This article aims to present an overview of Amartya Sen's thought, relating to his writings on political philosophy and his contributions to the field of development economics. This paper shows how justice and development are highly related in Sen's approach based on the concept of capability. Along with this paper, we will present some debates between Sen and John Rawls, beside other critics. This is done to explain the complex theoretical system elaborated by him. In concluding, the paper shows that the objective of Sen is to find a satisfactory concept of development that is explicit in its ethical presumptions.