960 resultados para Transfer processes
Resumo:
This paper addresses one of the issues in contemporary globalisation theory: the extent to which there is ‘one best way’ in which business can be done and organisations managed. It uses Czarniawska’s ‘Travels of Ideas’ model as an organising framework to present and understand how the concept of ‘Quality’, so important in contemporary approaches to manufacturing & services, and their management, travelled to, and impinged on, a newly opened vehicle assembly plant in Poland. The extent to which new meanings were mutually created in the process of translation is discussed, using ethnographic reporting and analysis techniques commonly used in diffusion research. Parallels between the process of translation as an idea becomes embedded into a new cultural location, and the processes which contemporary research has identified as important to organisational learning, are briefly discussed in conclusion.
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This study investigated the physical processes involved in the development of thunderstorms over southwestern Amazon by hypothesizing causalities for the observed cloud-to-ground lightning variability and the local environmental characteristics. Southwestern Amazon experiences every year a large variety of environmental factors, such as the gradual increase in atmospheric moisture, extremely high pollution due to biomass burning, and intense deforestation, which directly affects cloud development by differential surface energy partition. In the end of the dry period it was observed higher percentages of positive cloud-to-ground (+CG) lightning due to a relative increase in +CG dominated thunderstorms (positive thunderstorms). Positive (negative) thunderstorms initiated preferentially over deforested (forest) areas with higher (lower) cloud base heights, shallower (deeper) warm cloud depths, and higher (lower) convective potential available energy. These features characterized the positive (negative) thunderstorms as deeper (relatively shallower) clouds, stronger (relatively weaker) updrafts with enhanced (decreased) mixed and cold vertically integrated liquid. No significant difference between thunderstorms (negative and positive) and nonthunderstorms were observed in terms of atmospheric pollution, once the atmosphere was overwhelmed by pollution leading to an updraft-limited regime. However, in the wet season both negative and positive thunderstorms occurred during periods of relatively higher aerosol concentration and differentiated size distributions, suggesting an aerosol-limited regime where cloud electrification could be dependent on the aerosol concentration to suppress the warm and enhance the ice phase. The suggested causalities are consistent with the invoked hypotheses, but they are not observed facts; they are just hypotheses based on plausible physical mechanisms.
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The role of lateral gene transfer (LGT) in prokaryotes has been shown to rapidly change the genome content, providing new gene tools for environmental adaptation. Features related to pathogenesis and resistance to strong selective conditions have been widely shown to be products of gene transfer between bacteria. The genomes of the gamma-proteobacteria from the genus Xanthomonas, composed mainly of phytopathogens, have potential genomic islands that may represent imprints of such evolutionary processes. In this work, the evolution of genes involved in the pathway responsible for arginine biosynthesis in Xanthomonadales was investigated, and several lines of evidence point to the foreign origin of the arg genes clustered within a potential operon. Their presence inside a potential genomic island, bordered by a tRNA gene, the unusual ranking of sequence similarity, and the atypical phylogenies indicate that the metabolic pathway for arginine biosynthesis was acquired through LGT in the Xanthomonadales group. Moreover, although homologues were also found in Bacteroidetes (Flavobacteria group), for many of the genes analyzed close homologues are detected in different life domains (Eukarya and Archaea), indicating that the source of these arg genes may have been outside the Bacteria clade. The possibility of replacement of a complete primary metabolic pathway by LGT events supports the selfish operon hypothesis and may occur only under very special environmental conditions. Such rare events reveal part of the history of these interesting mosaic Xanthomonadales genomes, disclosing the importance of gene transfer modifying primary metabolism pathways and extending the scenario for bacterial genome evolution.
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We study the mutual interaction between the dark sectors (dark matter and dark energy) of the Universe by resorting to the extended thermodynamics of irreversible processes and constrain the former with supernova type Ia data. As a by-product, the present dark matter temperature results are not extremely small and can meet the independent estimate of the temperature of the gas of sterile neutrinos.
Resumo:
The mechanism and the energy profile of the gas-phase reaction that mimics esterification under acidic conditions have been investigated at different levels of theory. These reactions are known to proceed with rate constants close to the collision limit in the gas-phase and questions have been raised as to whether the typical addition-elimination mechanism via a tetrahedral intermediate can explain the ease of these processes. Because these reactions are common to many organic and biochemical processes it is important to understand the intrinsic reactivity of these systems. Our calculations at different levels of theory reveal that a stepwise mechanism via a tetrahedral species is characterized by energy barriers that are inconsistent with the experimental results. For the thermoneutral exchange between protonated acetic acid and water and the exothermic reaction of protonated acetic acid and methanol our calculations show that these reactions proceed initially by a proton shuttle between the carbonyl oxygen and the hydroxy oxygen of acetic acid mediated by water, or methanol, followed by displacement at the acylium ion center. These findings suggest that the reactions in the gas-phase should be viewed as an acylium ion transfer reaction. (C) 2010 Wiley Periodicals, Inc. Int J Quantum Chem 111: 1596-1606, 2011
Resumo:
The bioelectrochemical behavior of three triphenylmethane (TPM) dyes commonly used as pH indicators, and their application in mediated electron transfer systems for glucose oxidase bioanodes in biofuel cells was investigated. Bromophenol Blue, Bromothymol Blue, Bromocresol Green were compared bio-electrochemically against two widely used mediators, benzoquinone and ferrocene carboxy aldehyde. Biochemical studies were performed in terms of enzymatic oxidation, enzyme affinity, catalytic efficiency and co-factor regeneration. The different features of the TPM dyes as mediators are determined by the characteristics in the oxidation/reduction processes studied electrochemically. The reversibility of the oxidation/reduction processes was also established through the dependence of the voltammetric peaks with the sweep rates. All three dyes showed good performances compared to the FA and BQ when evaluated in a half enzymatic fuel cell. Potentiodynamic and power response experiments showed maxima power densities of 32.8 mu W cm(-2) for ferrocene carboxy aldehyde followed by similar values obtained for TPM dyes around 30 mu W cm(-2) using glucose and mediator concentrations of 10 mmol L(-1) and 1.0 mmol L(-1), respectively. Since no mediator consumption was observed during the bioelectrochemical process, and also good redox re-cycled processes were achieved, the use of triphenylmethane dyes is considered to be promising compared to other mediated systems used with glucose oxiclase bioanodes and/or biofuel cells. (C) 2011 Elsevier Inc. All rights reserved.
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Polyfluorene end-capped with N-(2-benzothiazole)-1 8-naphthalimide (PF-BNI) is a highly fluorescent material with fluorescence emission modulated by solvent polarity Its low energy excited state is assigned as a mixed configuration state between the singlet S(1) of the fluorene backbone (F) with the charge transfer (CI) of the end group BNI The triexponential fluorescence decays of PF-BNI were associated with fast energy migration to form an intrachain charge-transfer (ICCT) state polyfluorene backbone decay and ICCT deactivation Time-resolved fluorescence anisotropy exhibited biexponential relaxation with a fast component of 12-16 ps in addition to a slow one in the range 0 8-1 4 ns depending on the solvent showing that depolarization occurs from two different processes energy migration to form the ICCT state and slow rotational diffusion motion of end segments at a longer time Results from femtosecond transient absorption measurements agreed with anisotropy decay and showed a decay component of about 16 ps at 605 nm in PF BNI ascribed to the conversion of S(1) to the ICCT excited state From the ratio of asymptotic and initial amplitudes of the transient absorption measurement the efficiency of intrachain ICCT formation is estimated in 0 5 which means that on average, half of the excited state formed in a BNI-(F)(n)-BNI chain with n = 32 is converted to its low energy intrachain charge-transfer (ICCT) state
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By modeling the spectral energy distribution (SED) of the W3 IRS5 high-mass star formation region and matching this model to observed data, we can constrain the physical parameters of the basic system geometry and cloud mass distribution. From these parameters, we hope to add to the understanding of high-mass star formation processes. In particular, we hope to determine if the geometries associated with lowmass star formation carry over into the high-mass regime.
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Drawing upon Brazilian experience, this research explores some of the key issues to be addressed in using e-government technical cooperation designed to enhance service provision of Patent Offices in developing countries. While the development of software applications is often seen merely as a technical engineering exercise, localization and adaptation are context bounded matters that are characterized by many entanglements of human and non-humans. In this work, technical, legal and policy implications of technical cooperation are also discussed in a complex and dynamic implementation environment characterized by the influence of powerful hidden agendas associated with the arena of intellectual property (IP), which are shaped by recent technological, economic and social developments in our current knowledge-based economy. This research employs two different theoretical lenses to examine the same case, which consists of transfer of a Patent Management System (PMS) from the European Patent Office (EPO) to the Brazilian Patent Office that is locally named ‘Instituto Nacional da Propriedade Industrial’ (INPI). Fundamentally, we have opted for a multi-paper thesis comprising an introduction, three scientific articles and a concluding chapter that discusses and compares the insights obtained from each article. The first article is dedicated to present an extensive literature review on e-government and technology transfer. This review allowed the proposition on an integrative meta-model of e-government technology transfer, which is named E-government Transfer Model (ETM). Subsequently, in the second article, we present Actor-Network Theory (ANT) as a framework for understanding the processes of transferring e-government technologies from Patent Offices in developed countries to Patent Offices in developing countries. Overall, ANT is seen as having a potentially wide area of application and being a promising theoretical vehicle in IS research to carry out a social analysis of messy and heterogeneous processes that drive technical change. Drawing particularly on the works of Bruno Latour, Michel Callon and John Law, this work applies this theory to a longitudinal study of the management information systems supporting the Brazilian Patent Office restructuration plan that involved the implementation of a European Patent Management System in Brazil. Based upon the ANT elements, we follow the actors to identify and understand patterns of group formation associated with the technical cooperation between the Brazilian Patent Office (INPI) and the European Patent Office (EPO). Therefore, this research explores the intricate relationships and interactions between human and non-human actors in their attempts to construct various network alliances, thereby demonstrating that technologies embodies compromise. Finally, the third article applies ETM model as a heuristic frame to examine the same case previously studied from an ANT perspective. We have found evidence that ETM has strong heuristic qualities that can guide practitioners who are engaged in the transfer of e-government systems from developed to developing countries. The successful implementation of e-government projects in developing countries is important to stimulate economic growth and, as a result, we need to understand the processes through which such projects are being implemented and succeed. Here, we attempt to improve understanding on the development and stabilization of a complex social-technical system in the arena of intellectual property. Our preliminary findings suggest that e-government technology transfer is an inherently political process and that successful outcomes require continuous incremental actions and improvisations to address the ongoing issues as they emerge.
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This article presents a cooling system for cutting tool in turning based in a toolholder with cooling fluid flowing inside its body being that this fluid must necessarily be able to phase change due to heat generated from machining processes. In this way, the fluid evaporates just under the cutting tool allowing a heat transfer more efficient than if were used a fluid without phase change once the latent heat of evaporation is beneficial for removal heat. Following, the cooling fluid evaporated passes through a condenser located out of the toolholder where it is condensated and returns to the toolholder again and a new cycle is started. In this study, the R-123, a hydrochlorofluorocarbon (HCFC) fluid, was selected for the turning of a Cr-Ni-Nb-Mn-N austenitic steel of hard machinability. The machining tests were carried out under three different machining conditions: dry machining, external cutting fluid (conventional method), and with the toolholder proposed. As result, the developed system allows a surface roughness up to 10% better than dry machining and a tool life close to the conventional method, but 32% superior to dry machining; moreover, there are environmental and economics advantages once the cooling fluid is maintained in a loop circuit.
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The feasibility of using Streptomyces clavuligerus ATCC 27064 bioparticles supported on alginate gel containing alumina to produce clavulanic acid (CA) was investigated. To this end, effectiveness factors for spherical bioparticles, relating respiration rates of immobilised and free cells, were experimentally determined for various dissolved oxygen (DO) levels and bioparticle radii. Monod kinetics was assumed as representative of the oxygen consuming reaction, while internal oxygen diffusion was considered the limiting step. A comparison was made of the results from a tower bioreactor operating under batch, repeated-batch and continuous conditions with immobilised bioparticles. The theoretical curve of the effectiveness factor for the zero-order reaction model, considering an inert nucleus - the dead core model - was very well fitted to the experimental data. The results of the bioprocess indicated that the batch operation was the most efficient and productive, requiring a do concentration in the reactor above 60% of the saturation value. (C) 2007 Elsevier B.V. All rights reserved.
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We report the energy-transfer mechanisms and emission quantum yield measurements of sol-gel-derived Eu3+-based nanohybrids. The matrix of these materials, classified as diureasils and termed U(2000) and U(600), includes urea cross-links between a siliceous backbone and polyether-based segments of two molecular weights, 2000 and 600, respectively. These materials are full-color emitters in which the Eu3+ (5)Do --> F-7(0-4) lines merge with the broad green-blue emission of the nanoscopic matrix's backbone. The excitation spectra show the presence of a large broad band (similar to 27000-29000 cm(-1)) undoubtedly assigned to a ligand-to-metal charge-transfer state. Emission quantum yields range from 2% to 13.0% depending on the polymer molecular weight and Eu3+ concentration. Energy transfer between the hybrid hosts and the cations arises from two different and independent processes: the charge-transfer band and energy transfer from the hybrid's emitting centers. The activation of the latter mechanisms induces a decrease in the emission quantum yields (relative to undoped nanohybrids) and permits a fine-tuning of the emission chromaticity across the Comission Internacionalle d'Eclairage diagram, e.g., (x, y) color coordinates from (0.21, 0.24) to (0.39, 0.36). Moreover, that activation depends noticeably on the ion local coordination. For the diureasils with longer polymer chains, energy transfer occurs as the Eu3+ coordination involves the carbonyl-type oxygen atoms of the urea bridges, which are located near the hybrid's host emitting centers. on the contrary, in the U(600)-based diureasils, the Eu3+ ions are coordinated to the polymer chains, and therefore, the distance between the hybrid's emitting centers and the metal ions is large enough to allow efficient energy-transfer mechanisms.
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The present paper quantifies and develops the kinetic aspects involved in the mechanism of interplay between electron and ions presented elsewhere(1) for KhFek[Fe(CN)(6)](l)center dot mH(2)O (Prussian Blue) host materials. Accordingly, there are three different electrochemical processes involved in the PB host materials: H3O+, K+, and H+ insertion/extraction mechanisms which here were fully kinetically studied by means of the use of combined electronic and mass transfer functions as a tool to separate all the processes. The use of combined electronic and mass transfer functions was very important to validate and confirm the proposed mechanism. This mechanism allows the electrochemical and chemical processes involved in the KhFek[Fe(CN)(6)](l)center dot mH(2)O host and Prussian Blue derivatives to be understood. In addition, a formalism was also developed to consider superficial oxygen reduction. From the analysis of the kinetic processes involved in the model, it was possible to demonstrate that the processes associated with K+ and H+ exchanges are reversible whereas the H3O+ insertion process was shown not to present a reversible pattern. This irreversible pattern is very peculiar and was shown to be related to the catalytic proton reduction reaction. Furthermore, from the model, it was possible to calculate the number density of available sites for each intercalation/deintercalation processes and infer that they are very similar for K+ and H+. Hence, the high prominence of the K+ exchange observed in the voltammetric responses has a kinetic origin and is not related to the amount of sites available for intercalation/deintercalation of the ions.
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The luminescence properties of solid hydrated lanthanide squarates (Ln2(C4O4)3(H2O) x; x = 8 or 13;Ln3+ = Gd, La, Eu, Tb, Pr) are reported for temperatures down to 4.2K. The luminescence of the squarate group is observed for the Gd3+ and La3+ compounds at low temperatures (below 150K). The Pr3+ compound does not show any emission at all, not even at 4.2K. This is ascribed to the quenching of the Pr3+ emission by multiphonon relaxation and/or concentration quenching. The quantum efficiencies of the 5D0 emission of Eu3+ and of the 5D4 emission of Tb3+ in these squarate complexes are strikingly different. Whereas the Tb3+ emission shows a temperature independent quantum efficiency of 50% upon ligand excitation, the Eu3+ emission is strongly quenched, showing a temperature dependent quantum efficiency of 0.8% at 4.2K upon ligand excitation. This quenching is ascribed to the low energy position of the charge-transfer state of Eu3+ in these compounds.
Resumo:
The efficiency of energy transfer (ET) between Pr3+ ions in a fluoroindate glass is determined. ET rates, WET, were determined for dilute samples and the results show a dependence of WET on the Pr3+ concentration. ET processes which contribute to resonance fluorescence and frequency upconversion emission were studied. The origin of the interaction energy among the Pr3+ ions was determined to be dipole - dipole. © 1998 Elsevier Science B.V. All rights reserved.