996 resultados para Proteção contra corrosão


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Aquest article té dos objectius bàsics. En primer lloc, mostrar la capacitat analítica d'un estudi de cas a l'hora d'estudiar l'expressió de la identitat i dels rols assumits pels participants en la comunicació, posant-la en relació amb els marcs participatius d'Erwing Goffman (1981), d'una banda, i amb la dixi de persona i les seves manifestacions gramaticals (Levinson 1983; Nogué 2008), de l'altra. I en segon lloc, mostrar com l'estructura gramatical pot proporcionar indicadors lingüístics que donen informació sobre la identitat i els rols assumits, posant l'èmfasi en una circumstància concreta: la manera com es reflecteix lingüísticament la col¿lisió entre dos o més rols. Paraules clau: dixi de persona, identitat, rol participatiu, marc participatiu. This article has two main purposes. In the first place, to show how a case study can provide interesting information about the expression of identity and of the different roles assumed by the communication participants. On the one hand, this information is related to the participation frameworks proposed by Erwing Goffman (1981); on the other hand, to person deixis and its grammatical manifestations (Levinson 1983; Nogué 2008). And in the second place, to show how grammatical structure can provide linguistic cues about identity and roles, putting the emphasis on a specific circumstance: the linguistic signs of the collision between two or more of these roles. Key words: person deixis, identity, participation role, participation framework.

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Sialic acids are nine-carbon carbohydrates that occur widely in nature and occupy the terminal portions of some glycoproteins and glycolipids of cell membranes. These carbohydrates are closely involved in cell-cell interactions and in processes such as microbial infection, inflammation, etc. Studies on the participation of sialic acids in biological processes have provided comprehension about their role in the infection by the influenza virus, the causal agent of flu. In this article, we present an overview of the importance of sialic acids in the influenza virus infection and how the knowledge of their involvement in this process has allowed the development of selective and efficient drugs against the virus.

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Very often hydrochloric acid is employed in acidification operations aiming to dissolve the mineral matrix in petroleum wheel operations, which always require intense use of corrosion inhibitors. This work presents an evaluation of common indicators, phenolfthaleine, fluorescein, methylene blue, alizarine S and methyl orange, as corrosion inhibitors for carbon steel in HCl 15% w/v at temperatures of 26, 40 and 60 ºC. Fluorescein and methyl orange show excelent corrosion inhibition efficiencies at 26 ºC; however at 60 ºC only fluorescein shows good corrosion inhibition when employed with alcohol and/or formaldehyde. For the fluorescein 1% w/v + formaldehyde 0.6% w/v mixture we present polarization and impedance curves and adsorption isotherms.

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In this paper a water quality index is developed to subsidize management actions in the Atibaia River for upon protection of aquatic organisms. This index is composed of two measurable environmental parameters normaly, ammonia and dissolved oxygen, the latter representing the contribution of organic matter. Concentrations of these two variables were normalized on a scale from 0 to 100 and translated into statements of quality (excellent, good, regular, bad and very bad). The index was applied to three monitoring points in the Atibaia River and compared to other indices used by the State of São Paulo Environmental Agency (CETESB). The results showed that the degradation in this watershed follows the urban population density. The developed index is more restricted than the other ones routinely used to infer water quality.

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Transcripció del col·loqui amb Laura Mora, Marco Deriu, Núria Beitia i Clara Jourdan sobre les ponències del Seminari 'La democràcia igualitària i la violència contra les dones'

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Aquest any al seminari que organitzem al Centre de Recerca en Estudis de les Dones Duoda de la Universitat de Barcelona, ens hem proposat interrogar-nos, una vegada més, sobre una de les realitats humanes i polítiques mes crues en què es concreta el desordre que causa en alguns homes, en el present, el que anomenem el "final del patriarcat": la violència contra les dones. Aquesta violència, que ha existit des que va sorgir el patriarcat per a intentar apoderar-se de la paraula i del sentit del ser dona en el món, és ja expressable per a moltes dones a Occident i també a Orient

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A study on optimization of bath parameters for electrodeposition of Fe-W-B alloys from plating baths containing ammonia and citrate is reported. A 2³ full factorial design was successfully employed for experimental design analysis of the results. The corrosion resistance and amorphous character were evaluated. The bath conditions obtained for depositing the alloy with good corrosion resistance were: 0.01 M iron sulfate, 0.10 M sodium tungstate and 0.60 M ammonium citrate. The alloy was deposited at 12% current efficiency. The alloy obtained had Ecorr -0.841 V and Rp 1.463 x 10(4) Ohm cm². The deposit obtained under these conditions had an amorphous character and no microcracks were observed on its surface. Besides this, the bath conditions obtained for depositing the alloy with the highest deposition efficiency were: 0.09 M iron sulfate, 0.30 M sodium tungstate and 0.50 M ammonium citrate. The alloy was deposited at 50% current efficiency, with an average composition of 34 wt% W, 66 wt% Fe and traces of boron. The alloy obtained had Ecorr -0.800 V and Rp 1.895 x 10³ Ohm cm². Electrochemical corrosion tests verified that the Fe-W-B alloy deposited under both conditions had better corrosion resistance than Fe-Mo-B.

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Fundamental aspects of the conception and applications of ecomaterials, in particular porous materials in the perspective of green chemistry are discussed in this paper. General recommendations for description and classification of porous materials are reviewed briefly. By way of illustration, some case studies of materials design and applications in pollution detection and remediation are described. It is shown here how different materials developed by our groups, such as porous glasses, ecomaterials from biomass and anionic clays were programmed to perform specific functions. A discussion of the present and future of ecomaterials in green chemistry is presented along with important key goals.

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The effectiveness of microemulsions (ME) of saponified coconut oil (OCS-ME) and diphenylcarbazide (DC-ME) on a carbon steel corrosion inhibition process was evaluated using an electrochemical method of polarization resistance. The ME was prepared with OCS, butanol, kerosene and saline solutions. OCS-ME and DC-ME showed highest inhibitions effects (77% and 92%, respectively) at lower concentrations (0.5% and 0.48 - 0.50%, respectively). The surfactant OCS (in H2O) showed lower efficiency (63% at 0.20 - 0.25% concentration). The greatest inhibitory effect of DC-ME could be correlated with the chemical structure and the rich O/W ME system, which are very important for adsorption phenomena in interfacial ME systems.

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In order to ascertain the impact of agricultural activities on water quality of the Ribeira de Iguape River Basin in the state of São Paulo, surface water areas for catchment and drinking water have been characterized. The sampling period covered March/2002 - February/2003 and January/2004 at 10 different catchment points. SPE-LC-UV/Vis was used to monitor various pesticide classes such as carbamates, triazines and nitroanilines. The results revealed that water quality is associated with seasonal variation. Of 152 samples analyzed, only 24% showed the presence of pesticides, particulary during the wet season. High variability in pH, turbidity and color were observed.

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A commercial corrosion inhibitor used in petroleum production was characterized by means of infrared spectroscopy and energy dispersive spectroscopy (EDS). Predicting the adsorption behavior of corrosion inhibitor onto steel, sandstone and esmectite is the key to improve working conditions. In this study, the adsorption kinetics of inhibitor formulations in HCl 15% or in Mud Acid (HCl 13,5% and ammonium bifluoride) onto steel, sandstone and esmectite was determined by means of spectrophotometry. Kinetic parameters indicated that adsorption of inhibitor in the presence of bifluoride was favored. Moreover, the adsorption constant rate was the largest when the substrate was esmectite.

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Dedicatio: Petrus Brahe.

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Fuels and biofuels have a major importance in the transportation sector of any country, contributing to their economic development. The utilization of these fuels implies their closer contact to metallic materials, which comprise vehicle, storage, and transportation systems. Thus, metallic corrosion could be related to fuels and biofuels utilization. Specially, the corrosion associated to gasoline, ethanol, diesel, biodiesel, and their mixtures is discussed in this article. Briefly, the ethanol is the most corrosive and gasoline the least. Few investigations about the effect of biodiesel indicate that the corrosion is associated to their unsaturation degree and the corrosion of diesel is related to its acidity.

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Invocatio: I.N.J.

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The present work provides an overview of patent protection for second medical use of known chemical compounds, in Brazil and other countries, through the approach of the main controversies related to this theme. That issues encompass aspects related to the legality of the protection granted by the patent, the general requirements of patenteability, the ethic and social concepts and the politic and economic factors involved. This work also introduces the diverging views of the two Brazilian government agencies involved in the procedure for granting patent in the pharmaceutical area, INPI and ANVISA.