1000 resultados para Transições de fases estruturais
Resumo:
A transição da escola elementar para a Escola Básica traz consigo maus momentos para muitos alunos. No momento em que as mudanças da adolescência a nível físico, emocional e social começam, as crianças encontram-se num ambiente escolar radicalmente diferente daquele a que estavam habituadas. Para alguns alunos esta mudança marca o começo de uma descida em espiral em relação ao rendimento académico, desistência escolar e outros problemas sérios. No nosso país, cerca de 41.1 por cento dos adolescentes desistem da escola antes de completarem o ensino secundário. Portugal é o país da União Europeia com a mais elevada taxa de abandono escolar precoce. A percentagem de crianças/jovens até aos 15 anos que não completam a escolaridade básica é de 2.7 por cento (17.874). De acordo com o estudo “Insucesso e Abandono Escolar” elaborado pelo Ministério da Educação em 2003, as taxas de abandono escolar são insignificantes no 1º ciclo, revelando-se crescentes nos ciclos seguintes e acentuam-se de forma marcante nos anos seguintes à passagem de ciclo (5º, 7º e 10º). Segundo o mesmo estudo, o abandono escolar tem muito mais a ver com a idade do que com o ano de escolaridade que se frequenta e é geralmente precedido de histórias de insucesso repetido. Os anos de escolaridade críticos para a retenção dos alunos são os que se seguem à mudança de ciclo. O referido estudo chama a atenção para o excesso de transferências de escola a que os alunos estão sujeitos. No grupo dos pré adolescentes é comum verem-se descidas de níveis académicos, descida de auto estima e declínio de motivação. Resultados de investigações sugerem que a transição de ciclo quando envolve mudança de escolas não é um factor benigno. A maneira como o ambiente e contexto da nova escola satisfaz as necessidades dos prés adolescentes tem um papel importante nos seus percursos académicos e nas suas vidas. Nesta comunicação, faremos o resumo de algumas investigações sobre os efeitos de transição de ciclo e escola, analisaremos as perspectivas de todos os alunos do 5º ano duma Escola Básica e Secundária que passaram por essa transição e apresentaremos sugestões práticas para uma suave transição entre o 1º e o 2º ciclo.
Resumo:
Quando nasce um indivíduo com uma incapacidade ou a adquire ao longo do percurso de vida, a família lida de uma determinada forma com essa nova e indesejada notícia. O presente estudo teve como intuito verificar que impacto tem a presença de filhos portadores de incapacidade no ciclo vital da família. Pretende-se compreender a perda e o processo de luto inerente a estas famílias, nomeadamente os sentimentos e reações face à incapacidade dos filhos, mudanças na vida dos pais, momentos mais difíceis e relacionamento que os pais têm com os filhos com necessidades educativas especiais. Para a realização da investigação, recorreu-se às entrevistas semiestruturadas a 13 pais, 12 do género feminino e 1 do género masculino com idades compreendidas entre os 30 e 63 anos, com escolaridade desde a 4ª classe até o Doutoramento. Recorreu-se à Grounded Theory com o intuito de encontrar as categorias principais relacionadas com o impacto da presença de necessidades educativas especiais na família. As quatro categorias identificadas demonstram que o diagnóstico é um fator importante para o processo de aceitação do indivíduo com NEE. Os pais relatam sentimentos negativos perante a incapacidade do filho, falta de informação, falta de diversos apoios, nomeadamente o social, monetário, terapêutico, médico e psicológico. Falam também dos preconceitos existentes na sociedade e a falta de recursos para a inclusão do indivíduo com NEE. Os pais demonstram preocupação em relação às transições intrínsecas ao próprio ciclo de vida dos indivíduos com NEE, à inclusão na sociedade e à incerteza do futuro. Estas preocupações podem afetar a funcionalidade da família, constituindo as causas para diversas mudanças e reajustes no seio familiar, manifestando-se maioritariamente na mudança de rotinas. Podendo também ocorrer mudanças estruturais na família, como sendo o divórcio. A relação dos pais com os filhos pode ser considerada como boa, caracterizada por sentimentos positivos e amor incondicional.
Resumo:
This dissertation examines the organizational innovation as a nonlinear process, which occurs in a social and political context and, therefore, socially immersed. Examines the case of shrimp in the state of RN, starting from the following problem: although the norteriograndense shrimp occupies the largest producer of farmed shrimp from Brazil, has a series of bottlenecks concerning the generation of industry innovation, concerning the social relationships and policies between the various actors in the network, whether private or public, and its consequences in terms of opportunity and limits generated for the innovative dynamics. The objective of the research is to understand how the social embeddedness of political actors affects norteriograndense shrimp within the context of structural relations, the industry generation of innovation, throughout its technological trajectory . The approach of social embeddedness balances atomised perspectives, undersocialized and oversocialized, of economic action, considering both the human capacity to act as sources of constraint, whose mechanisms are analyzed the structural and political. In methodological terms this is a case study, analyzed from the research literature, documentary and experimental. Primary data were collected through semi-structured interviews and analyzed in depth by the technique of content analysis. Was adopted a longitudinal approach, seeking to understand the phenomenon from the perspective of the subjects, describing it in an inductive process of investigation. After characterizing the sector and defining their technological trajectory, the analysis of the results followed its four stages: (1) Introduction of Technology: 1973-1980, (2) Intensification of Research: 1981-1991, (3) Technological Adaptation, 1992 -2003, (4) Technological Crisis: 2004-2009. A cross-sectional analysis along the evolutionary trajectory revealed the character of structural changes and policies over time, and implications on the generating process of innovation. Note that, the technological limit to which the sector reached requires changes in technology standards, but is more likely that the potiguar shrimp is entering a new phase of his career in technology rather than a new technological paradigm
Resumo:
This is a study concerning in the structure of non governmental organizations, based on the institutional theory. It aims to understand the relation among structure, social projects and environmental influences, analyzing if there is coherence with project social or expresses adaptation to the institutional pressures of the environment. It introduces as theoretical support for the themes, studies about institutional theory and social structure. The research is descriptive and exploratory; it also applies to a study of case, based on the technical procedures. From the research universe, that was compound by non governmental organizations from Natal, RN, Brasil, it was chosen the Casa Renascer, a non governmental organization that works with the combat to the violence and sexual exploration of children and teenagers. The data collection process employed includes documental research, observations and semi structured research devices, guided by the organizational process proposed by Serva (1996) and by the institutional theory. The collected data were qualitatively treated. The analysis was divided into three parts, following the research matters. The social project characterization demonstrated that the organization went by three main phases. The first one, characterized by focus in women and girls education and health; the second shows the emphasis on girls in social risk situation, with preventive approach; and the last one, characterized by victims assistance of violence and sexual exploration. From the analysis using the institutional theory mechanisms, the results showed that exists coherence between structure and environmental influences, but a weak coherence between structure and social projects. It indicates as main determinant of the structure, an aspect forgotten by the institutional theory, the power. It was observed the presence from normative, coercive and mimetic mechanisms, highlighting normative influences
Resumo:
The exopolysaccharides are extracellular compounds produced by some species of fungi and bacteria. It is suggested that these molecules, even when in the form of complex polysaccharide-peptide, are the main bioactive molecules of many fungus. Some of the biological activities displayed by these compounds can be accentuated and others may arise when you add chemically polar or nonpolar groups to polysaccharides. The fruiting body of Pleurotus sajor-caju produces a heteropolysaccharide with antineoplastic and antimicrobial activity, but other biological activities of this polymer have not been evaluated. In this work the exopolysaccharide of Pleurotus sajor-caju was sulfated chemically and structurally characterized. We also evaluated the antiproliferative, antioxidant and anticoagulant activities from native exopolysaccharide (PN) and its sulfated derivated (PS). Polyacrylamide gel electrophoresis, infrared spectroscopy and nuclear magnetic resonance (¹³C) proved successful in sulfation of PN to obtain PS. Analysis by gas chromatography-mass spectroscopy showed that PN and PS are composed of mannose, galactose, 3-O-methyl-galactose and glucose in proportion percentage of 44,9:16,3:19,8:19 and 49, 7:14,4:17,7:18,2, respectively. The percentage of sulfate found in PS was 22.5%. Antioxidants assays revealed that the sulfation procedure affects differently the activities of exopolysaccharides, while the total antioxidant capacity, the scavenging activity of superoxide radical and ferric chelating were not affected by sulfation, on the other hand the chemical modification of PN enhanced the scavenging activity of hydroxyl radical and reducing power. PS also showed anticoagulant activity in a dose-dependent manner and clotting time was 3.0 times higher than the baseline value in APTT at 2 mg/mL. The exopolysaccharide not presented antiproliferative activity against HeLa tumor cells, but PS affects the cellular proliferation in a time-dependent manner. After 72 h, the inhibition rate of PS (2.0 mg/mL) on HeLa cells was about 60%. The results showed that PN sulfation increase some of their activities.
Resumo:
The present study examines the chemical composition and their effects on free radicals, inflammation, angiogenesis, coagulation, VEGF effects and cellular proliferation of a polysaccharides from alga Sargassum vulgare. The sulfated polysaccharide was extracted from brown seaweed by proteolysis with enzymes maxataze. The presence of proteins and sugars were observed in crude polysaccharides. Fractionation of this crude extract was made with growing concentration of acetone (0.3-1.5 v) and produced four groups of polysaccharides. Anionic polysaccharides from brown seaweed Sargassum vulgare, SV1and PSV1 were fractionated (SV1) and purified (PSV1), and displayed with high total sugars and sulfate content and very low level of protein. This fucan SV1 contains low levels of protein and high carbohydrate and sulfate content. This polysaccharides prolonged activated partial thromboplastin time (aPTT) at 50 μg (>240 s). SV1 was found to have no effect on prothrombin time (PT), corresponding to the extrinsic pathway of coagulation. SV1 exhibits high antithrombotic action in vivo, with a concentration ten times higher than heparin. Polysaccharides from S. vulgare promoted direct inhibition enzymatic activity of thrombin and stimulated enzymatic activity of FXa. SV1 showed optimal inhibitory activity of thrombin (50.2±0.28%) at a concentration of 25 μg/mL. Its antioxidant action on scavenging radicals by DPPH was (22%), indicating the polymer has no cytotoxic action (hemolytic) on ABO and Rh blood types in different erythrocyte groups and displays strong anti-inflammatory action on all concentrations tested in the carrageenan-induced paw edema model, demonstrated by reduced edema and cellular infiltration. Angiogenesis is a dynamic process of proliferation and differentiation. It requires endothelial proliferation, migration, and tube formation. In this context, endothelial cells are a preferred target for several studies and therapies. The antiangiogenic efficacy of polysaccharides was examined in vivo in the chick chorioallantoic membrane (CAM) model by using fertilized eggs. Decreases in the density of the capillaries were assessed and scored. The results showed that SV1 and PSV1 have an inhibitory effect on angiogenesis. These results were also confirmed by inhibition tubulogenesis in rabbit aorta endothelial cell (RAEC) in matrigel. These compounds were assessed in Apoptosis assay (Annexin V - FITC / PI) and cell viability by MTT assay of RAEC. These polysaccharides do not affect the viability and do not have apoptotic or necrotic action. RAEC cell when incubated with SV1 and PSV1showed inhibition of VEGF secretion, observed when compounds were incubated at 25, 50 and 100 μg/μL. The VEGF secretion with the RAEC cell line for 24 h, was more effective for PSV1 at 50 μg/μL(71.4%) than SV1 100 μg/μL (75.9%). SV1 and PSV1 had an antiproliferative action (47%) against tumor cell line HeLa. Our results indicate that these sulfated polysaccharides have antiangiogenic and antitumoral actions
Resumo:
There are ores of clay in Piauí State that are used for red structural ceramics, which are naturally contaminated with calcareous vein. This is one thing that impedes its exploration in an adequate way, especially for tile production. The present work aims at verifying the influence of the calcareous contents in the technological structural ceramics area, seeking to determine a maximum permissible calcareous proportion/contents in the ceramic mass using the patterns of the local industry production. For the consecution of this paper, it was characterized the clay and calcareous material by FRX, DRX, TGA and DTA. It was also configurated by extrusion and burnt in the temperatures of 850°C, 900°C, 950°C and 1000°C pieces of the corpus with 0, 5, 10, 15 e 20% of calcareous proportion. After that, it was carried out technological samples of linear retraction, water absortion, apparent porosity, specific apparent mass and mechanic resistance. The results showed the possibility of using calcareous in the ceramic mass and in some cases the technological properties got better
Resumo:
The development and study of detectors sensitive to flammable combustible and toxic gases at low cost is a crucial technology challenge to enable marketable versions to the market in general. Solid state sensors are attractive for commercial purposes by the strength and lifetime, because it isn t consumed in the reaction with the gas. In parallel, the use of synthesis techniques more viable for the applicability on an industrial scale are more attractive to produce commercial products. In this context ceramics with spinel structure were obtained by microwave-assisted combustion for application to flammable fuel gas detectors. Additionally, alternatives organic-reducers were employed to study the influence of those in the synthesis process and the differences in performance and properties of the powders obtained. The organic- reducers were characterized by Thermogravimetry (TG) and Derivative Thermogravimetry (DTG). After synthesis, the samples were heat treated and characterized by Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), analysis by specific area by BET Method and Scanning Electron Microscopy (SEM). Quantification of phases and structural parameters were carried through Rietveld method. The methodology was effective to obtain Ni-Mn mixed oxides. The fuels influenced in obtaining spinel phase and morphology of the samples, however samples calcined at 950 °C there is just the spinel phase in the material regardless of the organic-reducer. Therefore, differences in performance are expected in technological applications when sample equal in phase but with different morphologies are tested
Resumo:
This dissertation presents a hybrid ceramic block the use of which reside in the buildings executed with walls. Initially, we conducted a survey on the requirements and / or norms prevailing in Brazil about structural ceramic blocks, making use of the experiences in other countries. This work seeks new materials and / or products in order to maintain or increase the compressive strength of the ceramic blocks, without neglecting the other properties. Then was collected materials (clay and crushed powder) and an approach on the characterization, through fluorescence, Mineralogy, vitrification curve and characterization of these materials used in the manufacture of the blocks by Ray Diffraction "X" and SEM. Subsequently it was made, numbered and measured dimensions of about 150 bodies of the test piece (hybrid ceramic blocks in small sizes) with varying percentages of 0%, 5%, 10% and 15% substitution of crushed clay powder. After sintering of the bodies of the test piece at temperatures of 900oC, 1000oC 1100oC and with a heating rate of 5oC/minuto and level of 1 hour, the samples were submitted to the tests (compressive strength and water absorption) and calculated their retractions, which were subsequently carried out the analysis of the results according to the criteria and parameters required by Brazilian legislation and standards in force
Resumo:
The cobalt-chromium alloy is extensively used in the Odontology for the confection of metallic scaffolding in partial removable denture. During the last few years, it has been reported an increasing number of premature imperfections, with a few months of prosthesis use. The manufacture of these components is made in prosthetic laboratories and normally involves recasting, using parts of casting alloy and parts of virgin alloy. Therefore, the objective of the present study was to analyze the mechanical properties of a commercial cobalt-chromium alloy of odontological use after successive recasting, searching information to guide the dental prosthesis laboratories in the correct manipulation of the cobalt-chromium alloy in the process of casting and the possible limits of recasting in the mechanical properties of this material. Seven sample groups were confectioned, each one containing five test bodies, divided in the following way: G1: casting only with virgin alloy; G2: casting with 50% of the alloy of the G1 + 50% of virgin alloy; G3: casting with 50% of the alloy of the G2 + 50% of virgin alloy; G4: casting with 50% of the alloy of the G3 + 50% of virgin alloy; G5: 50% of alloy of the G4 + 50% of virgin alloy; G6: 50% of alloy of the G5 + 50% of virgin alloy and finally the G7, only with recasting alloy. The modifications in the mechanical behavior of the alloy were evaluated. Moreover, it was carried the micro structural characterization of the material by optic and electronic scanning microscopy, and X ray diffraction.and fluorescence looking into the correlatation of the mechanical alterations with structural modifications of the material caused by successive recasting process. Generally the results showed alterations in the fracture energy of the alloy after successive recasting, resulting mainly of the increasing presence of pores and large voids, characteristic of the casting material. Thus, the interpretation of the results showed that the material did not reveal significant differences with respect to the tensile strength or elastic limit, as a function of successive recasting. The elastic modulus increased from the third recasting cycle on, indicating that the material can be recast only twice. The fracture energy of the material decreased, as the number of recasting cycles increased. With respect to the microhardness, the statistical analyses showedno significant differences. Electronic scanning microscopy revealed the presence of imperfections and defects, resulting of the recasting process. X ray diffraction and fluorescence did not show alterations in the composition of the alloy or the formation of crystalline phases between the analyzed groups. The optical micrographs showed an increasing number of voids and porosity as the material was recast. Therefore, the general conclusion of this study is that the successive recasting of of Co-Cr alloys affects the mechanical properties of the material, consequently leading to the failure of the prosthetic work. Based on the results, the best recommendadition is that the use of the material should be limited to two recasting cycles
Resumo:
Different types of heterogeneous catalysts of the silicoaluminophosphate type, (SAPO-5, SAPO-11, SAPO-31, SAPO-34 and SAPO-41), molecular sieves with a: AFI, AEL, ATO, CHA and AFO structure, respectively, were synthesized through the hydrothermal method. Using sources such as hydrated alumina (pseudobohemita), phosphoric acid, silica gel, water, as well as, different types of organic structural templates, such as: cetyltrimethylammonium bromide (CTMABr), di-isopropylamine (DIPA), di-n- propylamine (DNPA) and tetraethylammonium hydroxide (TEOS), for the respective samples. During the preparation of the silicoaluminophosphates, the crystallization process of the samples occurred at a temperature of approximately 200 ° C, ranging through periods of 18-72 h, when it was possible to obtain pure phases for the SAPOs. The materials were furthermore washed with deionized water, dried and calcined to remove the molecules of the templates. Subsequently the samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), absorption spectroscopy in the infrared region (FT-IR), specific surface area and thermal analysis via TG/DTG. The acidic properties were determined using adsorption of n-butylamine followed by programmed termodessorption. These methods revealed that the SAPO samples showed a typically weak to moderate acidity. However, a small amount of strong acid sites was also detected. The deactivation of the catalysts was conducted by artificially coking the samples, followed by n-hexane cracking reactions in a fixed bed with a continuous flow micro-reactor coupled on line to a gas chromatograph. The main products obtained were: ethane, propane, isobutene, n-butane, n-pentane and isopentane. The Vyazovkin (model-free) kinetics method was used to determine the catalysts regeneration and removal of the coke