866 resultados para field theories in dimensions other than four


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Reader Response Theory remains popular within Children's Literature Criticism. It seems to offer a sensible resolution to the question of whether meaning derives from text or reader. Through a close reading of one example of this criticism, I suggest that its dualisms are constantly collapsing into appeals to singular authority. at various stages the text or the reader is wholly responsible for meaning. I further suggest that the criticism bypasses the question of interpretation through claiming knowledge of a child reader whose opinions and reactions can be unproblematically accessed. We do not have to worry about reading texts, because we can, apparently, know the child's response to them with certainty. Anything other than this claim to certainty is taken to be a failure of responsibility, a wallowing in the subjective, obscure and perverse. My intention is to reinstate reading as the responsibility of criticism.

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This study investigated the effects of increased genetic diversity in winter wheat (Triticum aestivum L.), either from hybridization across genotypes or from physical mixing of lines, on grain yield, grain quality, and yield stability in different cropping environments. Sets of pure lines (no diversity), chosen for high yielding ability or high quality, were compared with line mixtures (intermediate level of diversity), and lines crossed with each other in composite cross populations (CCPn, high diversity). Additional populations containing male sterility genes (CCPms) to increase outcrossing rates were also tested. Grain yield, grain protein content, and protein yield were measured at four sites (two organically-managed and two conventionally-managed) over three years, using seed harvested locally in each preceding year. CCPn and mixtures out-yielded the mean of the parents by 2.4% and 3.6%, respectively. These yield differences were consistent across genetic backgrounds but partly inconsistent across cropping environments and years. Yield stability measured by environmental variance was higher in CCPn and CCPms than the mean of the parents. An index of yield reliability tended to be higher in CCPn, CCPms and mixtures than the mean of the parents. Lin and Binns’ superiority values of yield and protein yield were consistently and significantly lower (i.e. better) in the CCPs than in the mean of the parents, but not different between CCPs and mixtures. However, CCPs showed greater early ground cover and plant height than mixtures. When compared with the (locally non-predictable) best-yielding pure line, CCPs and mixtures exhibited lower mean yield and somewhat lower yield reliability but comparable superiority values. Thus, establishing CCPs from smaller sets of high-performing parent lines might optimize their yielding ability. On the whole, the results demonstrate that using increased within-crop genetic diversity can produce wheat crops with improved yield stability and good yield reliability across variable and unpredictable cropping environments.

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We discuss the generalized eigenvalue problem for computing energies and matrix elements in lattice gauge theory, including effective theories such as HQET. It is analyzed how the extracted effective energies and matrix elements converge when the time separations are made large. This suggests a particularly efficient application of the method for which we can prove that corrections vanish asymptotically as exp(-(E(N+1) - E(n))t). The gap E(N+1) - E(n) can be made large by increasing the number N of interpolating fields in the correlation matrix. We also show how excited state matrix elements can be extracted such that contaminations from all other states disappear exponentially in time. As a demonstration we present numerical results for the extraction of ground state and excited B-meson masses and decay constants in static approximation and to order 1/m(b) in HQET.

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Over the last 40 years there has been a profusion of studies about the ccumulation of technological capacities in firms from developing economies. However, there remain few studies that examine, on a combined basis, the relationship among: the trajectories of technological capacities accumulation; the underlying learning mechanisms; and, the implications of organizational factors for these two variables. Still scarcer are the studies that examine the relationship among these variables along time and based on a comparative case study. This dissertation examines the relationship among the trajectory of accumulation of innovative capacities in complex project management, the learning mechanisms underlying these technological capacities and the intra-organizational factors that influence these learning echanisms. That set of relationships is examined through a comparative and a long-term (1988-2008) case study in a capital goods firm (for the pulp and paper industry) and a pulp mill in Brazil. Based on first-hand quantitative and qualitative empiric evidence, gathered through extensive field research, this dissertation found: 1. Both firms accumulated innovative capacity in project management at the international frontier level (Level 6). However, there was variability between the firms in terms of the nature and speed of accumulation of those capacities. It was also observed that, at this level of innovation, the innovative capacities of both firms are not confined to their organizational boundaries, but they are distributed beyond their boundaries. 2. So that these companies could accumulate those levels of innovative capacities it was necessary to manage several learning mechanisms: leveraging of external knowledge and its internalization in terms of internal apacities of the firm. In other words, as the companies accumulated more innovative levels of capacities for project management, it was necessary to manage different cycles of technological learning. 3. Further, the relationship between the ccumulation of technological capacities and learning was affected positively by intra-organizational factors, such as 'authority disposition', 'mutability of work roles' and 'intensity of internal crises', and negatively by the factor 'singularity of goals'. This dissertation revealed divergent results between firms in two of the four factors studied. These results contribute to advance our understanding of the complexity and variability involved in the process of accumulation of innovative capacities in firms from developing economies. This highlights the growing importance of the organizational and the human resource dimensions of innovation and technological capacity as the company approaches the international frontier. The results suggest to managers that: (i) the good performance in project management in the two firms studied did not occur simply as a result of the pulp and paper Brazilian industry growth, rather as a result of the deliberate construction and accumulation of the capacities through an intensive and coordinated cyclical process of technological learning, (ii) to develop innovative capabilities in project management, besides looking for learning mechanisms they should also look at the organizational factors that influence the learning mechanisms directly, (iii) performance of pulp mill¿s projects is better when projects are implemented together with technology suppliers than when performed only by the mill. This dissertation concludes that capital goods firms have been having a fundamental role for the innovative capabilities accumulation in project management of pulp mills in Brazil (and vice-versa) for a long time. This contradicts some authors' propositions that affirm that: a) equipment suppliers for the pulp and paper industry have been creating little, if any, development of processes or engineering projects in Brazil; b) firms in the pulp and paper industry have little capacity for machinery and equipments projects only taking place in few technological activities, being internal or external to the firm. Finally, some studies are proposed for future research.

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We discuss the Gupta-Bleuler quantization of the free electromagnetic field outside static black holes in the Boulware vacuum. We use a gauge which reduces to the Feynman gauge in Minkowski spacetime. We also discuss its relation with gauges used previously. Then we apply the low-energy sector of this held theory to investigate some low-energy phenomena. First, we discuss the response rate of a static charge outside the Schwarzschild black hole in four dimensions. Next, motivated by string physics, we compute the absorption cross sections of low-energy plane waves for the Schwarzschild and extreme Reissner-Nordstrom black holes in arbitrary dimensions higher than three.

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In this work we study the asymptotic behavior of (2+1)-dimensional quantum electrodynamics in the infrared region. We show that an appropriate redefinition of the fermion current operator leads to an asymptotic evolution operator that contains a divergent Coulomb phase factor and a contribution from the electromagnetic field at large distances, factored from the evolution operator for free fields, and we conclude that the modified scattering operator maps two spaces of coherent states of the electromagnetic field, as in the Kulish-Faddeev model for QED (quantum electrodynamics) in four space-time dimensions.

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We apply the general principles of effective field theories to the construction of effective interactions suitable for few- and many-body calculations in a no-core shell model framework. We calculate the spectrum of systems with three and four two-component fermions in a harmonic trap. In the unitary limit, we find that three-particle results are within 10% of known semianalytical values even in small model spaces. The method is very general, and can be readily extended to other regimes, more particles, different species (e.g., protons and neutrons in nuclear physics), or more-component fermions (as well as bosons). As an illustration, we present calculations of the lowest-energy three-fermion states away from the unitary limit and find a possible inversion of parity in the ground state in the limit of trap size large compared to the scattering length. Furthermore, we investigate the lowest positive-parity states for four fermions, although we are limited by the dimensions we can currently handle in this case.

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We study attractor mechanism in extremal black holes of Einstein-Born-Infeld theories in four dimensions. We look for solutions which are regular near the horizon and show that they exist and enjoy the attractor behavior. The attractor point is determined by extremization of the effective potential at the horizon. This analysis includes the backreaction and supports the validity of non-supersymmetric attractors in the presence of higher derivative interactions in the gauge field part. (C) 2008 Elsevier B.V. All rights reserved.

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O aumento da produção hortícola em cultivo protegido necessita de estudos mais detalhados acerca da ocorrência de resíduos de agrotóxicos, devido às condições ambientais peculiares nesse sistema, no qual pragas de pouca importância no campo assumem relevância. Avaliou-se os resíduos dos inseticidas acefato e de seu metabólito metamidofós em tomate sob cultivo protegido e em campo. Os tratamentos aplicados foram: (a) testemunha; (b) uma aplicação de 75 g i.a. acefato.100 L-1 de água; (c) uma aplicação com 150 g i.a.100 L-1 de água; (d) quatro aplicações na dosagem de 75 g i.a.100 L-1 de água. As amostras foram tomadas a (-1), zero, 1, 3, 7, 14 e 21 dias após a última ou única aplicação. A determinação quantitativa foi feita por técnica de cromatografia em fase gasosa, usando-se detector fotométrico de chama. Os resíduos de acefato e de metamidofós nos frutos de cultivo protegido e de campo, sempre estiveram abaixo dos respectivos limites máximos de resíduos (LMRs) em todo o período de colheita das amostras. Ainda, o metabolismo de acefato a metamidofós foi muito baixo nos frutos, particularmente importante nas folhas, mas não foi bem caracterizado no solo. Os resíduos de acefato foram maiores no cultivo protegido do que no campo, especialmente em folhas e no solo, sendo também estáveis e persistentes, em geral até a amostragem de 7 dias após a aplicação.

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The listing task, a method used in social and behavioral sciences, is frequently used in ethnobotanical research to constructfolk taxonomies and select relevant itemsfor subsequent research. The objective of the present study was to determine whether visual stimuli are associated with responses to the theme plants or if context influences the answers. Interviews were conducted with 400 women in Rio Claro, São Paulo, Brazil, in four different locations: three with a visible presence of plants (a plant store, a supermarket, and a public plaza) and one with no plants (a street corner in the center of the city). The women were asked to name plants. Analysis indicates that visual stimuli influenced responses and that this is more marked in the plant store than in the other locations. The plants cited most often-roses, orchids, ferns, violets, and daisies-were, with little variation, the same in all the locales studied.

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In order to evaluate growth characteristics, adaptability, biomass production, nutrient recycling, nutrient distribution and the ability to regenerate degraded land, a trial using four multipurpose tree species (Leucaena leucocephala, Leucaena diversifolia, Acacia melanoxylon and Mimosa scabrella) was undertaken over two years in a distrophic red yellow latosol (oxisol) following a randomized block experimental design with four replications. At the age of two years, A. melanoxylon and L. diversifolia were the tallest species (5.25 and 4.97 m, respectively) and A. melanoxylon and M. scabrella had the largest diameters at 20 cm from tree base. Mimosa scabrella and A. melanoxylon had the highest dry matter production and quantity of nutrients in the above ground biomass. In all species, the highest nutrient contents were found in the leaves, followed by branches and stems. From all species, the highest Nutrient Utilization Efficiency Indexes were obtained for sulphur, phosphorous, and magnesium; L. diversifolia was the most efficient for nitrogen, potassium, calcium, sulphur, and manganese, while A. melanoxylon was the most efficient for phosphorus, magnesium, boron, iron, and zinc. Litter production levels over a three month period were as follows: M. scabrella > A. melanoxylon > L. diversifolia > L. leucocephala. Litter nutrient content was higher in M. scabrella than in the other species.

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We use ideas on integrability in higher dimensions to define Lorentz invariant field theories with an infinite number of local conserved currents. The models considered have a two-dimensional target space. Requiring the existence of lagrangean and the stability of static solutions singles out a class of models which have an additional conformal symmetry. That is used to explain the existence of an ansatz leading to solutions with non-trivial Hopf charges. © SISSA/ISAS 2002.

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In trickle irrigation systems, the design is based on the pre-established emission uniformity (EU) which is the combined result of the equipment characteristics and its hydraulic configuration. However, this desired value of the EU may not be confirmed by the final project (in field conditions) and neither by the yield uniformity. The hypotheses of this research were: a) the EU of a trickle irrigation system at field conditions is equal to the emission uniformity pre-established in the its design; b) EU has always the lowest value when compared with other indicators of uniformity; c) the discharge variation coefficient (VC) is not equal to production variation coefficient in the operational unit; d) the difference between the discharge variation coefficient and the productivity variation coefficient depends on the water depth applied. This study aimed to evaluate the relationship between EU used in the irrigation system design and the final yield uniformity. The uniformity indicators evaluated were: EU, distribution uniformity (UD) and the index proposed by Barragan & Wu (2005). They were compared estimating the performance of a trickle irrigation system applied in a citrus orchard with dimensions of 400m x 600m. The design of the irrigation system was optimized by a Linear Programming model. The tree rows were leveled in the larger direction and the spacing adopted in the orchard was 7m x 4m. The manifold line was always operating on a slope condition. The sensitivity analysis involved different slopes, 0, 3, 6, 9 and 12%, and different values of emission uniformity, 60, 70, 75, 80, 85, 90 and 94%. The citrus yield uniformity was evaluated by the variation coefficient. The emission uniformity (EU) after design differed from the EU pre-established, more sharply in the initial values lower than 90%. Comparing the uniformity indexes, the EU always generated lower values when compared with the UD and with the index proposed by Barragan. The emitter variation coefficient was always lower than the productivity variation coefficient. To obtain uniformity of production, it is necessary to consider the irrigation system uniformity and mainly the water depth to be applied.

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Includes bibliography

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Based on the hypothesis that alternative substrates should improve the yield of lettuce crops by producing better quality seedlings, the objective of this work was to evaluate the effect of different substrates on the production of seedlings of this species, and their growth in the field. The study was in two stages. The first consisted of the production of lettuce seedlings, and the second assessed their development in the field. Four alternative substrates were tested, obtained by mixing together a sieved vermicompost from which all clumps had been removed, sterilized sand, charred rice husks and basalt powder. The commercial substrate, Plantmax HA®, was also tested. In the first phase, which was conducted in a completely randomised design with four replications, the height, root length, number of leaves, leaf area and dry weight of the seedlings were all evaluated 28 days after sowing. In the second phase, which was carried out in the field in a randomised block design with four replications, the plants were harvested 50 days after transplanting and the head diameter, fresh weight, number of leaves and leaf and stem dry weight were evaluated. The alternative substrates produced larger seedlings in less time than the commercial substrate, resulting in a reduction of 10 days in the total crop cycle. The reduction in the time between sowing and harvesting, together with those aspects relating to sustainability, are the main advantages of the use of alternative substrates, since in the field crop production did not differ between treatments.