921 research outputs found
Geometrically induced singular behavior of entanglement
We show that the geometry of the set of quantum states plays a crucial role
in the behavior of entanglement in different physical systems. More
specifically it is shown that singular points at the border of the set of
unentangled states appear as singularities in the dynamics of entanglement of
smoothly varying quantum states. We illustrate this result by implementing a
photonic parametric down conversion experiment. Moreover, this effect is
connected to recently discovered singularities in condensed matter models.Comment: v2: 4 pags, 4 figs. A discussion before the proof of Proposition 1
and tomographic results were included, Propostion 2 was removed and the
references were fixe
Orbital Magnetism in Ensembles of Parabolic Potentials
We study the magnetic susceptibility of an ensemble of non-interacting
electrons confined by parabolic potentials and subjected to a perpendicular
magnetic field at finite temperatures. We show that the behavior of the average
susceptibility is qualitatively different from that of billiards. When averaged
over the Fermi energy the susceptibility exhibits a large paramagnetic response
only at certain special field values, corresponding to comensurate classical
frequencies, being negligible elsewhere. We derive approximate analytical
formulae for the susceptibility and compare the results with numerical
calculations.Comment: 4 pages, 4 figures, REVTE
Soil characterization and drainage effects in a savanna palm swamp (vereda) of an agricultural area from Central Brazil.
Brazilian palm swamps (veredas) are fundamentals in the hydrological balance of watercourses in the Brazilian savanna (Cerrado). The "sponge effect" of their soils is the main factor controlling local hydrology, storing rainwater, and functioning as headwaters. The restricted knowledge of these tropical ecosystems has led to increased losses, poor preservation, and reduction in their ecosystem services. Veredas have become refuges surrounded by croplands, often drained and inappropriately managed. This study shows the impacts of anthropization on soil processes and properties of a vereda in an agricultural area. Two soil profiles were selected and characterized as preserved and anthropized, respectively upstream and downstream of the studied vereda. Morphological, physical, chemical and microbiological properties were analyzed. Principal Components Analysis (PCA) was applied to synthesize the data and provide evidence of the main properties and underlying processes that most responded to the degradation action. The arrangement of this analysis shows three main distinguish drivers: one joining the properties related to the humification of organic matter and relative accumulation of mineral matter versus accumulation of organic matter; the second with properties related to soil chemical reactivity; and the third reflecting the mineralization of organic matter. Our results suggest that the anthropic action has strongly caused the organic carbon reduction (~22 %). After 20 years, the anthropized soil presents not only a great decline in carbon stock (~14 kg m-2), but also strong impacts on several other ecologic functions, such as water holding capacity. Veredas are complex and fragile environments, and they should be fully protected to maintain their ecosystem services
Pleural tuberculosis: is radiological evidence of pulmonary-associated disease related to the exacerbation of the inflammatory response?
OBJECTIVE: Pleural tuberculosis is the most frequently occurring form of extra pulmonary disease in adults. In up to 40% of cases, the lung parenchyma is concomitantly involved, which can have an epidemiological impact. This study aims to evaluate the pleural and systemic inflammatory response of patients with pleural or pleuropulmonary tuberculosis. METHODS: A prospective study of 39 patients with confirmed pleural tuberculosis. After thoracentesis, a high resolution chest tomography was performed to evaluate the pulmonary involvement. Of the 39 patients, 20 exhibited only pleural effusion, and high resolution chest tomography revealed active associated-pulmonary disease in 19 patients. The total protein, lactic dehydrogenase, adenosine deaminase, vascular endothelial growth factor, interleukin-8, tumor necrosis factor-α, and transforming growth factor-β1 levels were quantified in the patient serum and pleural fluid. RESULTS: All of the effusions were exudates with high levels of adenosine deaminase. The levels of vascular endothelial growth factor and transforming growth factor-β1 were increased in the blood and pleural fluid of all of the patients with pleural tuberculosis, with no differences between the two forms of tuberculosis. The tumor necrosis factor-α levels were significantly higher in the pleural fluid of the patients with the pleuropulmonary form of tuberculosis. The interleukin-8 levels were high in the pleural fluid of all of the patients, without any differences between the forms of tuberculosis. CONCLUSION: Tumor necrosis factor-α was the single cytokine that significantly increased in the pleural fluid of the patients with pulmonary involvement. However, an overlap in the results does not permit us to suggest that cytokine is a biological marker of concomitant parenchymal involvement. Although high resolution chest tomography can be useful in identifying these patients, the investigation of fast acid bacilli and cultures for M. tuberculosis in the sputum is recommended for all patients who are diagnosed with pleural tuberculosis
Optimal transfers from Moon to halo orbit of the Earth-Moon system
In this paper, we seek optimal solutions for a transfer from a parking orbit
around the Moon to a halo orbit around of the Earth-Moon system, by
applying a single maneuver and exploiting the stable invariant manifold of the
hyperbolic parking solution at arrival. For that, we propose an optimization
problem considering as variables both the orbital characteristics of a parking
solution around the Moon, (namely, its Keplerian elements) and the
characteristics of a transfer trajectory guided by the stable manifold of the
arrival Halo orbit. The problem is solved by a nonlinear programming method
(NLP), aiming to minimize the cost of to perform a single maneuver
transfer, within the framework of the Earth-Moon system of the circular
restricted three-body problem. Results with low and suitable time of
flight show the feasibility of this kind of transfer for a Cubesat
Numerical investigations of the orbital dynamics around a synchronous binary system of asteroids
In this article, equilibrium points and families of periodic orbits in the
vicinity of the collinear equilibrium points of a binary asteroid system are
investigated with respect to the angular velocity of the secondary body, the
mass ratio of the system and the size of the secondary. We assume that the
gravitational fields of the bodies are modeled assuming the primary as a mass
point and the secondary as a rotating mass dipole. This model allows to compute
families of planar and halo periodic orbits that emanate from the equilibrium
points and . The stability and bifurcations of these families are
analyzed and the results are compared with the results obtained with the
Restricted Three-Body Problem (RTBP). The results provide an overview of the
dynamical behavior in the vicinity of a binary asteroid system
Informes da avaliação de genótipos de girassol 2008/2009 e 2009.
bitstream/item/40374/1/Doc320VE.pd
Informes da avaliação de genótipos de girassol 2008/2009 e 2009.
Esta publicação apresenta os resultados das avaliações da Rede de Ensaios de Avaliação de Genótipos de Girassol, realizadas em diferentes regiões edafoclimáticas do País.bitstream/CPAF-RO-2010/14590/1/Doc320VE.pd
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