977 resultados para scientific and technological contexts
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The characterization and identification of proteolytic bacteria from the gut of the velvetbean caterpillar (Anticarsia gemmatalis) were the objectives of this study. Twelve aerobic and anaerobic isolates of proteolytic bacteria were obtained from the caterpillar gut in calcium caseinate agar. The number of colony forming units (CFUs) of proteolytic bacteria was higher when the bacteria were extracted from caterpillars reared on artificial diet rather than on soybean leaves (1.73 +/- 0.35 X 10(3) and 0.55 +/- 0.22 X 10(3) CFU/mg gut, respectively). The isolated bacteria were divided into five distinct groups, according to their polymerase chain reaction restriction fragment-length polymorphism profiles. After molecular analysis, biochemical tests and fatty acid profile determination, the bacteria were identified as Bacillus subtilis, Bacillus cereus, Enterococcus gallinarum, Enterococcus mundtii, and Staphylococcus xylosus. Bacterial proteolytic activity was assessed through in vitro colorimetric assays for (general) proteases, serine proteases, and cysteine proteases. The isolated bacteria were able of hydrolyzing all tested substrates, except Staphylococcus xylosus, which did not exhibit serine protease activity. This study provides support for the hypothesis that gut proteases from velvetbean caterpillar are not exclusively secreted by the insect cells but also by their symbiotic gut bacteria. The proteolytic activity from gut symbionts of the velvetbean caterpillar is suggestive of their potential role minimizing the potentially harmful consequences of protease inhibitors from some of this insect host plants, such as soybean, with implications for the management of this insect pest species.
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Kraft pulp is currently bleached largely by the elemental chlorine free (ECF) technology with oxygen, chlorine dioxide, and hydrogen as active agents. This technology brought about significant environmental improvements in relation to standard processes based on chlorine gas and hypochlorite, but there is still need for further improvements. This study presents a novel environmentally friendly bleaching stage - the so-called `hydrogen peroxide in supercritical carbon dioxide`, P((SC-CO2)) - that can be adapted to current ECF bleaching processes, with preference in cases where hydrogen peroxide is already used. In this study, the P((SC-CO2)) stage was evaluated as a replacement to the last peroxide stage of the D(EP)DP bleaching sequence and to the first peroxide stage of the D(EP)DP sequence, for an oxygen delignified eucalypt kraft-O(2) pulp. The P((SC-CO2)) stage was run with 0.5% hydrogen peroxide, at 15% consistency, 70 degrees C, and 73 bar. The reaction time was 30 min. The performances of regular P stages and the new P((SC-CO2)) stage were compared. Promising results were observed with the DEP((SC-CO2))DP sequence; the P((SC-CO2)) decreased kappa number from 2.7 to 2.1, and the hexenuronic acid groups from 17.0 to 12.4 mmol kg(-1). The P((SC-CO2)) stage showed poor performance when applied in the D(EP)DP((SC-CO2)) sequence. It is concluded that the process presents potential but requires further optimization to improve selectivity and efficiency.
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In recent times, increasing attention has been paid to the use of renewable resources particularly of plant origin keeping in view the ecological concerns, renewability and many governments passing laws for the use of such materials. On the other hand, despite abundant availability of lignocellulosic materials in Brazil, very few attempts have been made about their utilization, probably due to lack of sufficient structure/property data. Systematic studies to know their properties and morphology may bridge this gap while leading to value addition to these natural materials. Chemical composition, X-ray powder diffraction, and morphological studies and thermal behavior aspects in respect of banana, sugarcane bagasse sponge gourd fibers of Brazilian origin are presented. Chemical compositions of the three fibers are found to be different than those reported earlier. X-ray diffraction patterns of these three fibers exhibit mainly cellulose type I structure with the crystallinity indices of 39%, 48% and 50% respectively for these fibers. Morphological studies of the fibers revealed different sizes and arrangement of cells. Thermal stability of all the fibers is found to be around 200 degrees C. Decomposition of both cellulose and hemicelluloses in the fibers takes place at 300 degrees C and above, while the degradation of fibers takes place above 400 degrees C. These data may help finding new uses for these fibers. (C) 2009 Elsevier B.V. All rights reserved.
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We employed the Density Functional Theory along with small basis sets, B3LYP/LANL2DZ, for the study of FeTIM complexes with different pairs of axial ligands (CO, H(2)O, NH(3), imidazole and CH(3)CN). These calculations did not result in relevant changes of molecular quantities as bond lengths, vibrational frequencies and electronic populations supporting any significant back-donation to the carbonyl or acetonitrile axial ligands. Moreover, a back-donation mechanism to the macrocycle cannot be used to explain the observed changes in molecular properties along these complexes with CO or CH(3)CN. This work also indicates that complexes with CO show smaller binding energies and are less stable than complexes with CH(3)CN. Further, the electronic band with the largest intensity in the visible region (or close to this region) is associated to the transition from an occupied 3d orbital on iron to an empty pi* orbital located at the macrocycle. The energy of this Metal-to-Ligand Charge Transfer (MLCT) transition shows a linear relation to the total charge of the macrocycle in these complexes as given by Mulliken or Natural Population Analysis (NPA) formalisms. Finally, the macrocycle total charge seems to be influenced by the field induced by the axial ligands. (C) 2011 Elsevier Ltd. All rights reserved.
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Countries differ in terms of technological capabilities and complexity of production structures. According to that, countries may follow different development strategies: one based on extracting rents from abundant endowments, such as labor or natural resources, and the other focused on creating rents through intangibles, basically innovation and knowledge accumulation. The present article studies international convergence and divergence, linking structural change with trade and growth through a North South Ricardian model. The analysis focuses on the asymmetries between Latin America and mature and catching up economies. Empirical evidence supports that a shift in the composition of the production structure in favor of R&D intensive sectors allows achieving higher rates of growth in the long term and increases the capacity to respond to demand changes. A virtuous export-led growth requires laggard countries to reduce the technological gap with respect to more advanced ones. Hence, abundance of factor endowments requires to be matched with technological capabilities development for countries to converge in the long term.
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A presente pesquisa foi conduzida na forma de um estudo de caso de duas instituições culturais no contexto francês e brasileiro. O Centro Pompidou é um projeto presidencial de museu financiado pelo Estado, com a missão de tornar a arte moderna em todas as suas expressões acessíveis ao público em geral. O Sesc Pompeia é um centro multidisciplinar de cultura e esporte - financiado pelo dinheiro dos impostos e administrado pela Federação do Comércio . O Sesc Pompéia é dedicado à oferta de educação informal através do cultivo da mente e do corpo. O estudo examina se as teorias de dependência de recursos e de poder podem ser utilizadas para conceituar a relação que o Centro Pompidou e do Sesc Pompéia tem com seus stakeholders financeiros. Mais especificamente, será discutido em que medida o grau de dependência influencia a estratégia de gestão das instituições. O objetivo é de responder a pergunta seguinte: quais são as estratégias que as instituições adotam para reduzir sua dependência com relação a seus principais stakeholders financeiros? Finalmente algumas implicações práticas de gestão serão elaboradas a partir do paralelo entre as estratégias das duas instituições.
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
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Currently the achievements of technology have not been enough to overcome the misery, in which are numerous human groups. Relegated to its background, the human being sees those scenarios, which brings out discussions about its formation, in which values are regarded as the scientific and technological aspects. The educational research inspired by this framework involving the theme of human development, update and re-frame concepts related to the linkage between interactivity and interaction, two important features presented in the process of Distance Education (DE). The research inquired about how these features have been articulated. It conducted a field study in which two professors were interviewed. The results showed that the integration between interactivity and interaction, involving aspects such as autonomy, critical awareness, relationships among students, the sharing of values and worldviews, is at the base of the educational processes of the DE. They also showed that, on these processes, there are shortcomings regarding the development of values and having to be thought the tutor training strategies from an interdisciplinary view.
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Organic agriculture is a sustainable cultivation ecologically, economically and socially. Several researches in organic agriculture have been made from technical perspectives, economic traits or related to ecological aspects. There are practically no investigations into the nature of the technology used in organic agriculture, especially from an ergonomic perspective. From the activity analysis, this study aimed to map the technology used in the production of organic vegetables. Properties producing organic vegetables were selected representing the State of São Paulo. It was applied an instrument (questionnaire and semi-structured interview) with their managers and it was made visual records to identify adaptations, innovations and technological demands that simultaneously minimize the workload and the difficulties in performing the tasks and increase work productivity. For some of the technological innovations a digital scanner was used to generate a virtual solid model to facilitate its redesign and virtual prototyping. The main results show that organic farmers have little technology in product form. The main innovations that enable competitive advantage or allow higher labor productivity occur in the form of processes, organization and marketing.
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
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The present review describes mainly the history of SnO2-based voltage-dependent resistors, discusses the main characteristics of these polycrystalline semiconductor systems and includes a direct comparison with traditional ZnO-based voltage-dependent resistor systems to establish the differences and similarities, giving details of the basic physical principles involved with the non-ohmic properties in both polycrystalline systems. As an overview, the text also undertakes the main difficulties involved in processing SnO2- and ZnO-based non-ohmic systems, with an evaluation of the contribution of the dopants to the electronic properties and to the final microstructure and consequently to the system's non-ohmic behavior. However, since there are at least two review texts regarding ZnO-based systems [Levinson, L. M., and Philipp, H. R. Ceramic Bulletin 1985;64:639; Clarke, D. R. Journal of American Ceramic Society 1999;82:485], the main focus of the present text is dedicated to the SnO2-based varistor systems, although the basic physical principles described in the text are universally useful in the context of dense polycrystalline devices. However, the readers must be careful of how the microstructure heterogeneity and grain-boundary chemistry are capable to interfere in the global electrical response for particular systems. New perspectives for applications, commercialization and degradation studies involving SnO2-based polycrystalline non-ohmic systems are also outlined, including recent technological developments. Finally, at the end of this review a brief section is particularly dedicated to the presentation and discussions about others emerging non-ohmic polycrystalline ceramic devices (particularly based on perovskite ceramics) which must be deeply studied in the years to come, specially because some of these systems present combined high dielectric and non-ohmic properties. From both scientific and technological point of view these perovskite systems are quite interesting. (c) 2007 Elsevier Ltd. All rights reserved.
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Tin oxide has wakened up great scientific and technological interest for its potential use in varistors production and as gas sensor. In order to improve the microstructural and electrical properties in SnO2 varistor ceramics, the influence of differents dopants used, like TiO2 and Al2O3, is under research. The effect of TiO2 and Al2O3 on the properties of Sn-Co-Nb varistor systems obtained by the Pechini method has been investigated in this work. Characterization of synthesized raw material was performed by X-Ray Diffraction (XRD) and Scanning Electronic Microscopy (SEM). The microstructural and electrical characterization of sintered samples show that the TiO2 favors the grain growth and the Al2O3 contributes to the decrease it, effect that is manifested in the Sn-Co-Nb varistor systems. Breakdown field increase up to 6300V/cm with increasing Al2O3 content and non-linear coefficients with alpha=22 were obtained.
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Nowadays, power system operation becomes more complex because of the critical operating conditions resulting from the requirements of a market-driven operation. In this context, efficient methods for optimisation of power system operation and planning become critical to satisfy the operational (technical), financial and economic demands. Therefore, the detailed analysis of modern optimisation techniques as well as their application to the power system problems represent a relevant issue from the scientific and technological points of view. This paper presents a brief overview of the developments on modern mathematical optimisation methods applied to power system operation and planning. Copyright © 2007 Inderscience Enterprises Ltd.
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Includes bibliography