988 resultados para massive infestation


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Using the Langevin approach for stochastic processes, we study the renormalizability of the massive Thirring model. At finite fictitious time, we prove the absence of induced quadrilinear counterterms by verifying the cancellation of the divergencies of graphs with four external lines. This implies that the vanishing of the renormalization group beta function already occurs at finite times.

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The role of dermal mast cells (DMC) in the host resistance to ticks has been studied but it is not totally explained yet. Studies have proposed that zebuine cattle breeds, known as highly resistant to ticks, have more DMC than taurine breeds. In the present study, we compared the number of adult female ticks Boophilus microplus and the mast cells' countings in the skin of F-2 crossbred Gir x Holstein cattle, before and after tick infestation. F-2 crossbred cattle (n = 148) were divided into seven groups and artificially infested with 1.0 x 10(4) B. nticroplus larvae and, 21 days afterwards, adult female-fed ticks attached to the skin were counted. Skin biopsies were taken and examined under light microscopy with a square-lined ocular reticulum in a total area of 0.0625 mm(2) in both the superficial and deep dermis. Results demonstrated that infested F-2 crossbred cattle acquired resistance against the cattle-tick B. microplus probably associated to an increase in the dermal mast cell number. It is concluded that the tick infestation may lead to an environmental modification in the dermis of parasitized hosts due to the massive migration of mast cells or their local proliferation.

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Starting from general properties of a spin-2 field, we construct helicity wave functions in the framework of the Weyl-van der Waerden spinor formalism. We discuss here the cases of massless and massive spin-2 particles.

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Cytomorphologic characteristics of smears from fine-needle aspirates (FNA) of three cases of sinus histiocytosis with massive lymphadenopathy (SHML) (Rosai-Dorfman disease) are described. All aspirates showed mature lymphocytes, plasma cells, and large pale histiocytes with well-preserved lymphocytes within the cytoplasm (lymphocytophagocytosis). The cases were confirmed by surgical biopsy, and the immunohistochemical findings suggested a macrophage origin for this lesion. The value of FNA analysis as an aid to diagnosis of SHML is discussed.

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The effects of massive lesions of the telencephalon on the behavioral repertoire of captive pigeons were investigated. The behavior of four birds with an intact telencephalon was compared to that of four birds submitted to ablation of telencephalic structures. Behavioral audio recording was done according to previously defined categories in three daily sessions for fifteen days. Experimental birds were followed up for one month. Immediately after the lesion, operated birds showed decreases in the occurrence of different behaviors such as coordinated movements, feeding, interaction, preening, maintenance, exploration and vocalization and increases in locomotion and discrete movements of the body when compared to the control birds (P < 0.05). Recovery of exploration (P < 0.05), feeding and localization was observed during the follow-up period. These data are interpreted as suggestive of a functional role of the telencephalon in the organization of behavior and a long-term recovery of behavior after detelencephalation.

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The objective of this work was to evaluated the infestion of the whitefly Bemisia tabaci (Genn.) B biotype and thrips Caliothrips phaseoli (Hood) in fifteen beans genotypes in field condition. The genotypes IAPAR 31, Rosinha G2, Jalo precoce, Perola, IAC Harmonia, Gen 99TGR110, Gen 99TG2868, Gen 99TGR3416, Gen 99TG3450, Gen 99TG823, Gen 99TGR609, IAC Jaragua, Gen 95A10061531, Gen 99TGR3114 e Gen 96A1473153V2 was used. The experiment was conducted from May to July 2006. The statistical design was randomized blocks, totalizing 15 treatments and four replications. Evaluation was realized weekly, totalizing seven samplings. The evaluations were accomplished on a weekly basis by counting B. tabaci biotype B eggs and nymphs and nymphs of C. phaseoli in 10 leaflets per plot. The less oviposition genotypes by B. tabaci biotype B were IAC Harmonia, Perola, Gen TG3114 e Gen 95A10061531, while the most oviposited were IAC Jaragua and Gen 99TG3450. The less presence of nymphs of whitefly were observed on Perola and IAC Harmonia and the most at IAC Jaragua. It was observed a negative and non significant linear correlation between average temperature versus number of silverleaf whitefly and temperature versus number of thrips was verified.

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This study examined salivary glands of unfed, partially engorged, and engorged females of the tick Amblyomma cajennense on rabbits at first infestation using histological and histochemical techniques. In type I acini, no significant changes were observed among the three feeding conditions. In type II acini of unfed females, c1, c2, and c4 cells were described for the first time in this species. In a comparison among the three feeding conditions, an increase in this acinus was observed, due to the increase in secretion in c1, c2, and c4 cells and the appearance of c3 cells. In engorged females, some cells were still active. Type III acini presented cells d, e, and f containing secretion in unfed females. In partially engorged females, these cells were devoid of secretion. In engorged females, type III acini exhibited a reduced lumen. After engorgement, all acini underwent a degenerative process, as observed in females after two to five days post-engorgement.

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The three larval stages of Dermatobia hominis (Linnaeus) have been evaluated for their immunogenicity by ELISA and immunodiffusion (ID) using sera from experimentally infested rabbits. During a primary infestation, first instar D. hominis were found to cause most reaction and allowed the earliest diagnosis by ELISA. An inhibition of the antibody response against second and third instars was observed. The inhibition disappeared after departure of the larvae from the host. In experimentally immunized hosts the antibody response, following challenge, was highest against second and third instar antigens. Antibody remained elevated during the infestation but fell immediately after the larvae had left the host.

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In this work, the behaviour of the system with N massive parallel rigid wires is analysed. The aim is to explore its resemblance to a system of multiple cosmic strings. Assuming that it behaves like a 'gas' of massive rigid wires, we use a thermodynamics approach to describe this system. We obtain a constraint relating the linear mass density of the massive wires, the number of the massive wires in the system and the dispersion velocity of the system. © 1996 IOP Publishing Ltd.

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The main characteristics of 55 nests of Protopolybia exigua exigua were periodically evaluated in Ribeirão Preto, southeastern Brazil. Although the queens' life-span can eventually reach one year, nests barely thrive for six months because most of them are periodically invaded by the scavenger phorid fly, Megaselia aff. picta. Under heavy infestation the adult wasp population partially closes the nest entrance, migrates and constructs a new nest in the neighborhood. Afterwards the old-nest's entrance can be completely closed by the wasps which results in blocking the parasitoid flies inside. In the tropics, predation by ants is considered the main selective pressure which shaped most of the bionomic characteristics of Polistinae wasps. It is suggested that Megaselia can easily overcome the usual wasps defensive tactics just because they are so specialized against ants. Aerial raids, fast erratic-jerking movements, rapid and efficient oviposition behavior, etc. can eventually turn Megaselia into a very important enemy of some social wasps.

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In the weak field approximation of higher order gravity theory a gravitational potential is described by a Newtonian plus a Yukawa-like term. This new term is used to explain some aspects of galactic dynamics, without considering dark matter. Its presence modifies the scattering probability of a massive intruder star and relaxation time of the stellar system.

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Using the manifestly spacetime supersymmetric description of the four-dimensional open superstring, we construct the vertex operator in superspace for the first massive state. This construction provides an N = 1 D = 4 superspace representation of the massive spin-2 multiplet. © 1997 Published by Elsevier Science B.V.

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A one parameter model of a confined-gluon propagator has been formulated by Frank and Roberts recently, which has a great success explaining π - and p - meson observables. We show, computing few chiral parameters, that a small variation of this model considering an infrared finite gluon propagator with a dynamically generated gluon mass, can also fit data related to the chiral symmetry breaking. This allows a direct interpretation for the unique parameter involved in the model as the gluon mass scale. © 1998 Elsevier Science B.V. All rights reserved.

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Using the manifestly spacetime-supersymmetric version of open superstring field theory, we construct the free action for the first massive states of the open superstring compactified to four dimensions. This action is in N = 1 D = 4 superspace and describes a massive spin-2 multiplet coupled to two massive scalar multiplets. © 1999 Published by Elsevier Science B.V. All rights reserved.