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Ricci, Ricardo Pedroso - One of the best experts on this subject based on the ideXlab platform.
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Desenvolvimento de critérios para seleção de adesivos utilizados na fabricação de pás de turbinas eólicas
Universidade Estadual Paulista (UNESP), 2012Co-Authors: Ricci, Ricardo PedrosoAbstract:O processo de fabricação das pás de turbinas eólicas envolve a colagem de estruturas fabricadas em plásticos reforçados com fibra de vidro. Neste trabalho foram analisadas os três principais tipos de adesivos estruturais utilizados pelos fabricante de pás (epóxi, poliuretano e metil-metacrilato), com o objetivo de desenvolver critérios que auxiliem na seleção de adesivos e de tratamentos superficiais aplicados às estrutuaras a serem coladas. A caracterização dos adesivos envolveu dois tipos de ensaios mecânicos: o cisalhamento de juntas de sobreposição simples e a clivagem de juntas adesivas. Dois tipos de tratamento das superfícies dos aderentes foram utilizados: camada de sacrifício removível (peel-ply) e abrasão. Também foi realizada a análise dos modos de falha das juntas ensaiadas como auxílio de compatibilidade entre adesivo e substrato. Os resultados mostram que o tratamento via peel-ply foi o mais eficiente para as juntas coladas com epóxi e Testadas em cisalhamento, ao apresentar um aumento de 28% na resistência em relação às superfícies sem tratamento. Imagens de microscopia eletrônica de varredura sugerem que esse tratamento gerou uma área maior de contato em relação à superfície não tratada e que causou menos danos à superfície do aderente do que o método abrasivo. Os grupos colados com adesivo metil metacrilato, independentemente do tipo de tratamento, obtiveram os maiores valores nos ensaios de clivagem, cerca de 170% superiores aos demais grupos. Para estruturas de pás corretamente projetadas para evitar cargas de peeling em suas juntas adesivas, este trabalho mostra que a melhor opção são aderentes tratados com peel-ply e colados com epóxi. Contudo, um plano de Testes deve ser elaborado sempre que houver a necessidade do emprego de um novo adesivo ou método de preparação superficialThe manufacturing process of wind turbine blades involves the bonding of structures made of glass reinforced plastic. This work analyzes the theree main types of structural adhesives used by blades manufactures (epoxy, polyurethane and methyl methacrylate), with the goal of developing criteria to assist in the selection of adhesives and surface treatments applied to the structures to be bonded. The characterization of the adhesives involved two types of mechanical Tests: single lap shear joints and Cleavage of adhesive joints. Two types of surface treatment of the adherents were used: removable sacrifical layer (peel-ply) and abrasion. The joint failure mode analysis was also carried out as an aid to the study of compatibility between adhesive and substrate. The results show that treatment via peel-ply was the most efficient for epoxy bonded substrates Tested in shear, by presenting a 28% increase in strengh compared to untreated surfaces. Images of scanning electron microscopy suggest that this treatment led to a larger area of contact relative to untreated surfaces and caused less damage to the substrate's surface than the abrasive method. The groups bonded with methyl methacrylate regardless the type of treatment, had the highest values in the Cleavage Test, approximately 170% higher than other groups. For propertly designed blades, that avoid peeling loads in their adhesive joints, this work shows that the best option are substrate treated with peel-ply and bonded with epoxy. However, a Test plan should be prepared whenever there is the necessity of using a new adhesive or method of surface preparationCoordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES
Ricci, Ricardo Pedroso [unesp] - One of the best experts on this subject based on the ideXlab platform.
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Desenvolvimento de critérios para seleção de adesivos utilizados na fabricação de pás de turbinas eólicas
Universidade Estadual Paulista (UNESP), 2012Co-Authors: Ricci, Ricardo Pedroso [unesp]Abstract:O processo de fabricação das pás de turbinas eólicas envolve a colagem de estruturas fabricadas em plásticos reforçados com fibra de vidro. Neste trabalho foram analisadas os três principais tipos de adesivos estruturais utilizados pelos fabricante de pás (epóxi, poliuretano e metil-metacrilato), com o objetivo de desenvolver critérios que auxiliem na seleção de adesivos e de tratamentos superficiais aplicados às estrutuaras a serem coladas. A caracterização dos adesivos envolveu dois tipos de ensaios mecânicos: o cisalhamento de juntas de sobreposição simples e a clivagem de juntas adesivas. Dois tipos de tratamento das superfícies dos aderentes foram utilizados: camada de sacrifício removível (peel-ply) e abrasão. Também foi realizada a análise dos modos de falha das juntas ensaiadas como auxílio de compatibilidade entre adesivo e substrato. Os resultados mostram que o tratamento via peel-ply foi o mais eficiente para as juntas coladas com epóxi e Testadas em cisalhamento, ao apresentar um aumento de 28% na resistência em relação às superfícies sem tratamento. Imagens de microscopia eletrônica de varredura sugerem que esse tratamento gerou uma área maior de contato em relação à superfície não tratada e que causou menos danos à superfície do aderente do que o método abrasivo. Os grupos colados com adesivo metil metacrilato, independentemente do tipo de tratamento, obtiveram os maiores valores nos ensaios de clivagem, cerca de 170% superiores aos demais grupos. Para estruturas de pás corretamente projetadas para evitar cargas de peeling em suas juntas adesivas, este trabalho mostra que a melhor opção são aderentes tratados com peel-ply e colados com epóxi. Contudo, um plano de Testes deve ser elaborado sempre que houver a necessidade do emprego de um novo adesivo ou método de preparação superficialThe manufacturing process of wind turbine blades involves the bonding of structures made of glass reinforced plastic. This work analyzes the theree main types of structural adhesives used by blades manufactures (epoxy, polyurethane and methyl methacrylate), with the goal of developing criteria to assist in the selection of adhesives and surface treatments applied to the structures to be bonded. The characterization of the adhesives involved two types of mechanical Tests: single lap shear joints and Cleavage of adhesive joints. Two types of surface treatment of the adherents were used: removable sacrifical layer (peel-ply) and abrasion. The joint failure mode analysis was also carried out as an aid to the study of compatibility between adhesive and substrate. The results show that treatment via peel-ply was the most efficient for epoxy bonded substrates Tested in shear, by presenting a 28% increase in strengh compared to untreated surfaces. Images of scanning electron microscopy suggest that this treatment led to a larger area of contact relative to untreated surfaces and caused less damage to the substrate's surface than the abrasive method. The groups bonded with methyl methacrylate regardless the type of treatment, had the highest values in the Cleavage Test, approximately 170% higher than other groups. For propertly designed blades, that avoid peeling loads in their adhesive joints, this work shows that the best option are substrate treated with peel-ply and bonded with epoxy. However, a Test plan should be prepared whenever there is the necessity of using a new adhesive or method of surface preparatio
João Paulo Viana Leite - One of the best experts on this subject based on the ideXlab platform.
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antioxidant study indicative of antibacterial and antimutagenic activities of an ellagitannin rich aqueous extract from the leaves of miconia latecrenata
Journal of Ethnopharmacology, 2019Co-Authors: Douglas Costa Gontijo, Luciano Gomes Fietto, Pablo Costa Gontijo, Geraldo Celio Brandao, Marisa Alves Nogueira Diaz, Alaide Braga De Oliveira, João Paulo Viana LeiteAbstract:Ethnopharmacological relevance; Several plant species of Miconia genus are commonly used in Brazilian folk medicine as anti-inflammatory agents and for the treatment of infectious diseases. Infusions and extracts of Miconia species are also reported as analgesic, antimicrobial, antimalarial, antioxidant, anti-inflammatory, antinociceptive, antimutagenic, and antitumoral. Aim of the study; To determine the phytochemical composition of an aqueous extract of Miconia latecrenata leaves and to evaluate its antioxidant, antibacterial, antimutagenic and antigenotoxic activities. Materials and Methods; The following methods were used for the different effects: I) antioxidant - β-carotene/linoleic acid, lipid peroxidation, and DPPH• radical scavenging; II) antibacterial - agar well diffusion and MIC methods); III) antimutagenic assays - Ames Test; and IV) antigenotoxic - Plasmid Cleavage Test. The phytochemical analysis and phenolic quantification were carried out by UPLC-DAD-ESI-MS/MS and colorimetry, respectively. In addition, statistical correlation analysis was performed aiming to evaluate the Pearson correlation between phenolic compounds and biological assays. Results; A high content of tannins was observed and the ellagitannin isomers of 1,2,3,5-tris-galloyl-4,6-HHDP-glucose were identified as the main constituents of the leaves aqueous extract. High antioxidant effect, in different Tests, high antibacterial activity to gram-positive and negative strains, as well as high antimutagenic activity were observed. Statistical analysis showed a high Pearson correlation for the tannin content in relation to the results of the antioxidant and antibacterial Tests. In general, the antioxidant action of the aqueous extract showed low correlation with the antimutagenic activity. Conclusions; The present results confirmed the expectations regarding the pharmacological profile of M. latecrenata supporting its therapeutic potential in relation to ROS/RNS related disorders. Furthermore, the phenolic compounds of M. latecrenata can act, in turn, minimizing or inhibiting the biological macromolecules damage, especially DNA.
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Assessment of the phenolic content, mutagenicity and genotoxicity of ethanolic extracts of stem bark and leaves from Strychnos pseudoquina A. St.-hil
Drug and chemical toxicology, 2018Co-Authors: Douglas Costa Gontijo, Líria Granato Nunes, Letícia Monteiro Farias, Maria Gorette Resende Duarte, André Furtado Carvalho, Luciano Gomes Fietto, João Paulo Viana LeiteAbstract:Strychnos pseudoquina is a plant species whose stem bark is used as bitter tonic beverage. The phytochemical analysis, as well as quantification of phenolic constituents and antioxidant activity of ethanolic extracts from S. pseudoquina stem bark, and leaves were conducted. The extracts were Tested for mutagenicity (Ames Test) and DNA-damaging activity (Plasmid Cleavage Test). Leaves recorded the largest amount of flavonoids. The performed high-performance liquid chromatography (HPLC) showed flavonoids such as isorhamnetin and strychnobiflavone (phytochemical markers of the investigated species) in stem barks, but not in leaves. The proanthocyanidin content and antioxidant activity were significantly higher in stem barks than in leaves. Stem bark and leaf extracts presented mutagenic activity against TA98 and TA100 strains with, and without, metabolic activation (S9). The Plasmid Cleavage Test did not indicate DNA-damaging activity. Our results suggest that extracts deriving from S. pseudoquina should be used with extreme caution, mainly the stem bark extract, which is widely used in folk medicine.
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Bark extract of Bathysa cuspidata attenuates extra‐pulmonary acute lung injury induced by paraquat and reduces mortality in rats
International journal of experimental pathology, 2012Co-Authors: Rômulo Dias Novaes, Reggiani Vilela Gonçalves, Marli Do Carmo Cupertino, Daiane Cristina Santos Marques, Damiana Diniz Rosa, Maria Do Carmo Gouveia Peluzio, Clóvis Andrade Neves, João Paulo Viana LeiteAbstract:The treatment of human diseases using medicinal plants and their derivatives is an ancient practice that is currently gaining popularity worldwide (Farnsworth 1994; Park et al. 2010). At the moment, there is considerable interest in natural plant products, particularly those used in traditional medicine. These products may be used in the development of new drugs and applications, which would include lung diseases induced by toxic agents (Lo et al. 2005; Park et al. 2010). This type of investigation has been shown to represent an effective strategy for selecting medicinal plants for the development of new drugs, as around 80% of the world population uses products derived from plants in their basic healthcare (Farnsworth 1994; Kaur et al. 2005). Paraquat (1, 1′-dimethyl-4, 4′-bipyridinium dichloride) (PQ) is a quaternary nitrogen herbicide, which is used worldwide because of its high efficacy and the low residue of the product left in crops (Sittipunt 2005; Chang et al. 2009). Its high toxicity to humans and animals when absorbed through ingestion, skin contact or inhalation has been extensively demonstrated (Dasta 1978; Suntres 2002; Marrs & Adjei 2003). This herbicide accumulates mainly in the lungs through the highly developed polyamine uptake system, leading to the generation of a superoxide radical () through an oxygen- and NADPH-dependent redox cycle, resulting in acute oxidative stress-related insults (Tsukamoto et al. 2002; Marrs & Adjei 2003; Wang et al. 2006; Chang et al. 2009). PQ-induced extra-pulmonary acute lung injury (ALI) results in alveolar epithelial cell (type I and II pneumocytes) and Clara cell disruption, impairment of surfactant production, haemorrhage, oedema, hypoxaemia and infiltration of inflammatory cells into the interstitial and alveoli spaces (Rocco et al. 2001, 2003; Park et al. 2010; Novaes et al. 2012). The principal cause of death in cases of PQ toxicity is respiratory failure associated with diffuse damage to the alveolar epithelium owing to oxidation of lipids and membrane proteins, which culminates in partial or total loss of cell and lung function (Mustafa et al. 2002; Tsukamoto et al. 2002; Rocco et al. 2004). In view of its reproducibility and simplicity of administration, this herbicide has been widely used as an experimental model in studies on ALI (Rocco et al. 2001, 2003; Chang et al. 2009; Novaes et al. 2012). Moreover, it constitutes an inexpensive model in which effects are rapid (Silva & Saldiva 1998; Rocco et al. 2003), thus ensuring its frequent use when investigating the effects of vegetable extracts on lung disorders (Kim et al. 2006; Park et al. 2010). Bathysa cuspidata (A. St. Hil.) Hook f. belongs to the Rubiaceae family. It is a plant popularly known in South America as ‘quina-do-mato’, and its bark is used in popular medicine for the prevention and treatment of stomach, liver and lung disorders, as well as an anti-inflammatory and healing agent (Novaes et al. 2012). In addition, in toxicity Tests in vitro, the ethanolic extracts of the leaves and bark of this species showed no mutagenic and genotoxic effects in the Ames Test, using TA98 and TA100 strains of Salmonella typhimurium, and plasmid (DNA plasmid pUC 18) Cleavage Test respectively (Nunes 2008). Considering that lung lesions from exposure to PQ occur through the induction of oxidative stress and activation of inflammatory response, compounds with antioxidant and anti-inflammatory action may potentially affect ALI and mortality from this condition (Suntres 2002; Kim et al. 2006). To clarify its relevance, its efficacy and possible mechanism of action, the objective of this study was to investigate the effect of the ethanolic bark extract of B. cuspidata on PQ-induced extra-pulmonary ALI and mortality in Wistar rats.
Michel Degrange - One of the best experts on this subject based on the ideXlab platform.
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Water resistance of resin-bonded joints with time related to alloy surface treatment
Journal of Dentistry, 1999Co-Authors: P Moulin, B. Picard, Michel DegrangeAbstract:Abstract Objectives : This paper attempts to study the resistance of resin-bonded metallic joints to damage in water with time. Methods : Unlike the shear or tensile Test, a Cleavage Test (Double Cantilever Beam Test) allows us to follow the crack propagation in water, according to the fracture mechanics concept. Moreover, it is possible to follow the kinetic degradation of the metal/resin interface because this Test is not totally destructive to the assembly. We have worked on 18 batches according to the nature of the alloys (Pd, Pd–Ag, Au, Co–Cr and Ni–Cr) and the surface treatment (sandblasting, Silicoater MD, Rocatec, V-Primer). The crack length was measured over a period of 20 days. The results are expressed in terms of adherence energy. Results : The adherence energy dramatically decreased with time in water. The slope of the regression straight line appears to be a good criterion for evaluating the durability of the alloy/adhesive interface. We have demonstrated the importance of silica coating and, especially, the effectiveness of the Rocatec system upon the degree of hydrolytic degradation, and have shown how the development of cracks depends upon surface treatment.
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Influence of surface treatment on adherence energy of alloys used in bonded prosthetics
Journal of oral rehabilitation, 1999Co-Authors: P Moulin, Michel Degrange, B. PicardAbstract:Usually, shear or tensile Tests are used to assess bond strengths between resin and metal. In this study, a Cleavage Test, the Double Cantilever Beam Test, was performed to measure the adherence energy in air and in water between a 4-META resin, and five alloys (palladium, palladium-silver, gold, cobalt-chromium and nickel-chromium alloys) whose surfaces have been treated by sandblasting only or by two methods of silica coating (Silicoater MD, Rocatec) or by painting with a primer (V-Primer). Results showed that, after storage in water, it is difficult to divide the studied alloys into a dental base alloys group and a noble alloys group. Therefore, the silica coating has significantly limited the propagation of fissures in water. Higher values of adherence energy were recorded with the Rocatec system except with the palladium alloy which must be treated with the Silicoater MD system. The treatment with V-Primer was sensitive to hydrolytic attack.
William A. Curtin - One of the best experts on this subject based on the ideXlab platform.
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Crack tip blunting and Cleavage under dynamic conditions
Journal of the Mechanics and Physics of Solids, 2016Co-Authors: Varun P. Rajan, William A. CurtinAbstract:Abstract In structural materials with both brittle and ductile phases, cracks often initiate within the brittle phase and propagate dynamically towards the ductile phase. The macroscale, quasistatic toughness of the material thus depends on the outcome of this microscale, dynamic process. Indeed, dynamics has been hypothesized to suppress dislocation emission, which may explain the occurrence of brittle transgranular fracture in mild steels at low temperatures ( Lin et al., 1987 ). Here, crack tip blunting and Cleavage under dynamic conditions are explored using continuum mechanics and molecular dynamics simulations. The focus is on two questions: (1) whether dynamics can affect the energy barriers for dislocation emission and Cleavage, and (2) what happens in the dynamic “overloaded” situation, in which both processes are energetically possible. In either case, dynamics may shift the balance between brittle Cleavage and ductile blunting, thereby affecting the intrinsic ductility of the material. To explore these effects in simulation, a novel interatomic potential is used for which the intrinsic ductility is tunable, and a novel simulation technique is employed, termed as a “dynamic Cleavage Test”, in which cracks can be run dynamically at a prescribed energy release rate into a material. Both theory and simulation reveal, however, that the intrinsic ductility of a material is unaffected by dynamics. The energy barrier to dislocation emission appears to be identical in quasi-static and dynamic conditions, and, in the overloaded situation, ductile crack tip behavior ultimately prevails since a single emission event can blunt and arrest the crack, preventing further Cleavage. Thus, dynamics cannot embrittle a ductile material, and the origin of brittle failure in certain alloys (e.g., mild steels) appears unrelated to dynamic effects at the crack tip.