826 resultados para causal representation


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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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We investigate the causal structure of general nonlinear electrodynamics and determine which Lagrangians generate an effective metric conformal to Minkowski. We also prove that there is only one analytic nonlinear electrodynamics not presenting birefringence.

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We show that the parametrized Wave-Packet Phase Space representation, which has been studied earlier by one of the authors, is equivalent to a Squeezed States Phase Space Representation of quantum mechanics. © 1988.

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A mapping scheme is presented which takes quantum operators associated to bosonic degrees of freedom into complex phase space integral kernel representatives. The procedure consists of using the Schrödinger squeezed state as the starting point for the construction of the integral mapping kernel which, due to its inherent structure, is suited for the description of second quantized operators. Products and commutators of operators have their representatives explicitly written which reveal new details when compared to the usual q-p phase space description. The classical limit of the equations of motion for the canonical pair q-p is discussed in connection with the effect of squeezing the quantum phase space cellular structure. © 1993.

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Four cases of suggestive inflammatory aneurysms in patients with neurocysticercosis have been described. We report a case of a 49-year-old woman who presented with subarachnoid haemorrhage from a right middle cerebral artery bifurcation aneurysm and had a casual relationship with neurocysticercosis. At surgery, a viable cysticercus without signs of inflammation or thickened leptomeninges was found in the distal position of the aneurysm. Postoperatively, the patient received albendazole and dextrochlorpheniramine. In the subsequent three years, the patient was asymptomatic and took drugs to prevent convulsion and arterial hypertension. The relationship between NCC and the presence of cerebral aneurysm is discussed.

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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A transmission line is characterized by the fact that its parameters are distributed along its length. This fact makes the voltages and currents along the line to behave like waves and these are described by differential equations. In general, the differential equations mentioned are difficult to solve in the time domain, due to the convolution integral, but in the frequency domain these equations become simpler and their solutions are known. The transmission line can be represented by a cascade of π circuits. This model has the advantage of being developed directly in the time domain, but there is a need to apply numerical integration methods. In this work a comparison of the model that considers the fact that the parameters are distributed (Universal Line Model) and the fact that the parameters considered concentrated along the line (π circuit model) using the trapezoidal integration method, and Simpson's rule Runge-Kutta in a single-phase transmission line length of 100 km subjected to an operation power. © 2003-2012 IEEE.

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Pós-graduação em Física - IFT

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The objective of the present work was to verify the behavior of yellow passion fruit, Afruvec variety, in relation to a population of Fusarium solani, obtained from this crop. The experimental delineation was random blocks, containing 10 treatments [9 isolates and 1 control treatment], with 4 repetitions, each plot being represented by a vase containing a plant. A disk of culture medium colonized by each isolate of the fungus was inoculated in the wounded collar region of the plants of the Afruvec variety two months after sowing. The appraised parameters were: the pathogenicity, the incidence (number of dead plants) and the severity of the disease (length of the lesion in the collar region), until 60 days after inoculation. The Afruvec variety was susceptible to the fungus and also presented variability as to the severity of the disease and incidence in relation to the different isolates. The population of the fungus showed variability in regard to aggressiveness. In light of the evidence of genetic diversity in the F. solani population, it is also suggested, in the tests of selection of materials to the pathogen, that these materials should be evaluated in different places with a history of the disease or inoculation with a pool of isolates of the fungus, in order to know the wide resistance of the genotype to the pathogen.

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With the “social turn” of language in the past decade within English studies, ethnographic and teacher research methods increasingly have acquired legitimacy as a means of studying student literacy. And with this legitimacy, graduate students specializing in literacy and composition studies increasingly are being encouraged to use ethnographic and teacher research methods to study student literacy within classrooms. Yet few of the narratives produced from these studies discuss the problems that frequently arise when participant observers enter the classroom. Recently, some researchers have begun to interrogate the extent to which ethnographic and teacher research methods are able to construct and disseminate knowledge in empowering ways (Anderson & Irvine, 1993; Bishop, 1993; Fine, 1994; Fleischer. 1994; McLaren, 1992). While ethnographic and teacher research methods have oftentimes been touted as being more democratic and nonhierarchical than quantitative methods—-which oftentimes erase individuals lived experiences with numbers and statistical formulas—-researchers are just beginning to probe the ways that ethnographic and teacher research models can also be silencing, unreflective, and oppressive. Those who have begun to question the ethics of conducting, writing about, and disseminating knowledge in education have coined the term “critical” research, a rather vague and loose term that proposes a position of reflexivity and self-critique for all research methods, not just ethnography or teacher research. Drawing upon theories of feminist consciousness-raising, liberatory praxis, and community-action research, theories of critical research aim to involve researchers and participants in a highly participatory framework for constructing knowledge, an inquiry that seeks to question, disrupt, or intervene in the conditions under study for some socially transformative end. While critical research methods are always contingent upon the context being studied, in general they are undergirded by principles of non-hierarchical relations, participatory collaboration, problem-posing, dialogic inquiry, and multiple and multi-voiced interpretations. In distinguishing between critical and traditional ethnographic processes, for instance, Peter McLaren says that critical ethnography asks questions such as “[u]nder what conditions and to what ends do we. as educational researchers, enter into relations of cooperation. mutuality, and reciprocity with those who we research?” (p. 78) and “what social effects do you want your evaluations and understandings to have?” (p. 83). In»the same vein, Michelle Fine suggests that critical researchers must move beyond notions of the etic/emic dichotomy of researcher positionality in order to “probe how we are in relation with the contexts we study and with our informants, understanding that we are all multiple in those relations” (p. 72). Researchers in composition and literacy stud¬ies who endorse critical research methods, then, aim to enact some sort of positive transformative change in keeping with the needs and interests of the participants with whom they work.

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We examine Weddell Sea deep water mass distributions with respect to the results from three different model runs using the oceanic component of the National Center for Atmospheric Research Community Climate System Model (NCAR-CCSM). One run is inter-annually forced by corrected NCAR/NCEP fluxes, while the other two are forced with the annual cycle obtained from the same climatology. One of the latter runs includes an interactive sea-ice model. Optimum Multiparameter analysis is applied to separate the deep water masses in the Greenwich Meridian section (into the Weddell Sea only) to measure the degree of realism obtained in the simulations. First, we describe the distribution of the simulated deep water masses using observed water type indices. Since the observed indices do not provide an acceptable representation of the Weddell Sea deep water masses as expected, they are specifically adjusted for each simulation. Differences among the water masses` representations in the three simulations are quantified through their root-mean-square differences. Results point out the need for better representation (and inclusion) of ice-related processes in order to improve the oceanic characteristics and variability of dense Southern Ocean water masses in the outputs of the NCAR-CCSM model, and probably in other ocean and climate models.

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ACID-BASE REACTIONS: CONCEPT, REPRESENTATION AND GENERALIZATION FROM THE ENERGY INVOLVED IN TRANSFORMATIONS. Undergraduate students on the first year of Chemistry Courses are unfamiliar with the representation of acid-base reactions using the ionic equation H+ + OH- -> H2O. A chemistry class was proposed about acid-base reactions using theory and experimental evaluation of neutralization heat to discuss the energy involved when water is formed from H+ and OH- ions. The experiment is suggested using different strong acids and strong base pairs. The presentation of the theme within a chemistry class for high school teachers increased the number of individuals that saw the acid-base reaction from this perspective.

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Background: In the analysis of effects by cell treatment such as drug dosing, identifying changes on gene network structures between normal and treated cells is a key task. A possible way for identifying the changes is to compare structures of networks estimated from data on normal and treated cells separately. However, this approach usually fails to estimate accurate gene networks due to the limited length of time series data and measurement noise. Thus, approaches that identify changes on regulations by using time series data on both conditions in an efficient manner are demanded. Methods: We propose a new statistical approach that is based on the state space representation of the vector autoregressive model and estimates gene networks on two different conditions in order to identify changes on regulations between the conditions. In the mathematical model of our approach, hidden binary variables are newly introduced to indicate the presence of regulations on each condition. The use of the hidden binary variables enables an efficient data usage; data on both conditions are used for commonly existing regulations, while for condition specific regulations corresponding data are only applied. Also, the similarity of networks on two conditions is automatically considered from the design of the potential function for the hidden binary variables. For the estimation of the hidden binary variables, we derive a new variational annealing method that searches the configuration of the binary variables maximizing the marginal likelihood. Results: For the performance evaluation, we use time series data from two topologically similar synthetic networks, and confirm that our proposed approach estimates commonly existing regulations as well as changes on regulations with higher coverage and precision than other existing approaches in almost all the experimental settings. For a real data application, our proposed approach is applied to time series data from normal Human lung cells and Human lung cells treated by stimulating EGF-receptors and dosing an anticancer drug termed Gefitinib. In the treated lung cells, a cancer cell condition is simulated by the stimulation of EGF-receptors, but the effect would be counteracted due to the selective inhibition of EGF-receptors by Gefitinib. However, gene expression profiles are actually different between the conditions, and the genes related to the identified changes are considered as possible off-targets of Gefitinib. Conclusions: From the synthetically generated time series data, our proposed approach can identify changes on regulations more accurately than existing methods. By applying the proposed approach to the time series data on normal and treated Human lung cells, candidates of off-target genes of Gefitinib are found. According to the published clinical information, one of the genes can be related to a factor of interstitial pneumonia, which is known as a side effect of Gefitinib.