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Search Results: 1 - 10 of 226467 matches for " Gabriela C; Barreto "
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Home range of marsh rats, holochilus sciureus, a rodent pest in rice fields of Venezuela
Eiris,Gabriela C; Barreto,Guillermo R;
Interciencia , 2009,
Abstract: radio tracking techniques were used to determine the home range of marsh rats holochilus sciureus in rice fields of the guárico river irrigation system, venezuela, in order to study movement patterns of tropical rodents and provide information for the management of this agricultural pest. after being captured using tomahawk traps, ten adult rats were equipped with radio-transmitters and tracked during the 2004 dry season between 18:00 and 6:00. home ranges were estimated based on four methods: minimum convex polygon, harmonic mean contours, fixed kernel and adaptive kernel. home ranges of males and females ranged between 0.6 and 1.3ha depending on the method of estimation. male-female range overlap and possible agonistic interactions between males, suggest male territoriality and a polygynic mating system. males showed greater motility than females. the results also reveal relationships between these rodent movements and environmental changes produced within rice plantations. ecological studies provide information for an integrated pest control program.
Decoherence and localization in the double well model
Gabriela Barreto Lemos,M. F. Santos,J. G. Peixoto de Faria,M. O. Terra Cunha,M. C. Nemes
Physics , 2005,
Abstract: We use a spin-1/2 model to analyze tunnelling in a double well system coupled to an external reservoir. We consider different noise sources such as fluctuations on the height and central position of the barrier and propose an experiment to observe these effects in trapped ions or atoms.
The role of chaos in quantum communication through a dynamical dephasing channel
Gabriela Barreto Lemos,Giuliano Benenti
Physics , 2010, DOI: 10.1103/PhysRevA.81.062331
Abstract: In this article we treat the subject of chaotic environments with few degrees of freedom in quantum communication by investigating a conservative dynamical map as a model of a dephasing quantum channel. When the channel's dynamics is chaotic, we investigate the model's semi-classical limit and show that the entropy exchange grows at a constant rate which depends on a single parameter (the interaction strength), analogous to stochastic models of dephasing channels. We analyze memory effects in the channel and present strong physical arguments to support that the present model is forgetful in the chaotic regime while memory effects in general cannot be ignored when channel dynamics is regular. In order to render the non-chaotic channel forgetful, it becomes necessary to apply a reset to the channel and this reset can efficiently be modeled by application of a chaotic map. We may then refer to encoding theorems (valid in the case of forgetful channels) to present evidence of a transition from noiseless to noisy channel due to the environment's transition from regular to chaotic dynamics.
Decoherence, entanglement decay, and equilibration produced by chaotic environments
Gabriela Barreto Lemos,Fabricio Toscano
Physics , 2011, DOI: 10.1103/PhysRevE.84.016220
Abstract: We investigate decoherence in quantum systems coupled via dephasing-type interactions to an arbitrary environment with chaotic underlying classical dynamics. The coherences of the reduced state of the central system written in the preferential energy eigenbasis are quantum Loschmidt echoes, which in the strong coupling regime are characterized at long times scales by fluctuations around a constant mean value. We show that due to the chaotic dynamics of the environment, the mean value and the width of the Loschmidt echo fluctuations are inversely proportional to the quantity we define as the effective Hilbert space dimension of the environment, which in general is smaller than the dimension of the entire available Hilbert space. Nevertheless, in the semiclassical regime this effective Hilbert space dimension is in general large, in which case even a chaotic environment with few degrees of freedom produces decoherence without revivals. Moreover we show that in this regime the environment leads the central system to equilibrate to the time average of its reduced density matrix, which corresponds to a diagonal state in the preferential energy eigenbasis. For the case of two uncoupled, initially entangled central systems that interact with identical local quantum environments with chaotic underlying classical dynamics, we show that in the semiclassical limit the equilibration state is arbitrarily close to a separable state. We confirm our results with numerical simulations in which the environment is modeled by the quantum kicked rotor in the chaotic regime.
Evaluation of anti-estrogenic or estrogenic activities of aqueous root extracts of Gunnera manicata L.
Mariotti, Kristiane de Cássia;Schmitt, Gabriela Cristina;Barreto, Fabiano;Fortunato, Rodrigo E.;Singer, Rodrigo B.;Dallegrave, Eliane;Leal, Mirna Bainy;Limberger, Renata Pereira;
Brazilian Journal of Pharmaceutical Sciences , 2011, DOI: 10.1590/S1984-82502011000300018
Abstract: gunnera perpensa (gunneraceae) is an african plant widely used in traditional medicine. this species is known for its activity involving the female reproductive system, such as inducing or increasing labor, treating female infertility, expelling the placenta and/or preventing post-partum hemorrhage. these properties are probably due to (z)-venusol, a majoritary compound, and its action in conjunction with substances in the whole extract and other natural products. in southern brazil, a native species gunnera manicata l. that also belongs to gunneraceae can be found. in spite of the traditional use of g. perpensa, there is no pharmacological and phytochemical information regarding the south american gunnera species. therefore, the aim of this study was to investigate the activity of brazilian g. manicata aqueous extracts on the reproductive system of immature female wistar rats through a uterotrophic assay and to verify the presence of (z)-venusol by liquid chromatography coupled with tandem mass spectrometry (lc-ms/ms). data were analyzed by analysis of variance (anova) and bonferroni′s post-hoc test (p< 0.01). results obtained shown that g. manicata extracts did not present in vivo anti or estrogenic activity. furthermore, (z)-venusol compound was not found. this study represents the first preliminary screening done on the south american g. manicata species.
Study of acute toxicity and investigation of the presence of β-N-methylamino-L-alanine in the Gunnera manicata L. a species native to Southern Brazil
Mariotti, Kristiane de Cássia;Barreto, Fabiano;Schmitt, Gabriela Cristina;Zancanaro, Ivomar;Dallegrave, Eliane;Singer, Rodrigo Bustos;Leal, Mirna Bainy;Limberger, Renata Pereira;
Brazilian Journal of Pharmaceutical Sciences , 2011, DOI: 10.1590/S1984-82502011000300021
Abstract: gunnera (gunneraceae) forms a complex association with the cyanobacterium nostoc puctiforme l. gunnera-nostoc symbiosis is the only one reported involving a flowering plant, and results in the formation of the neurotoxic amino acid β-n-methylamino-l-alanine (bmaa). the species gunnera manicata l., for which phytochemical, pharmacological and toxicological studies are lacking, is found in southern brazil. therefore, acute toxicity and the presence of neurotoxic amino acid were investigated in aqueous extracts of g. manicata. the acute toxicity test was conducted by administering aqueous root extract of g. manicata at a concentration of 2000 mg/kg in a single dose orally to wistar rats. lethality was monitored daily for 14 days after treatment. the relative mass of organs was analyzed by one-way anova and macroscopic changes were investigated. the analysis of bmaa, a procedure performed by gc/ms, involved a preliminary derivatization step. the esi-ms/ms analysis was done by direct infusion. the present study demonstrated absence of neurotoxin in the samples of g. manicata analyzed and absence of acute toxicity in aqueous root extracts. these data confirm that extracts from the roots of g. manicata have a high margin of drug safety.
Efeito da temperatura na estrutura e na estabilidade de ligas Fe - 18 Cr - (0 a 60) Ni
Bubani, Franco de Castro;Decarli, Célia Cristina Moretti;Brollo, Gabriela Lujan;Barreto, Edison Henrique;Diniz, Anselmo Eduardo;Mei, Paulo Roberto;
Rem: Revista Escola de Minas , 2010, DOI: 10.1590/S0370-44672010000100008
Abstract: the material studied consists of a series of alloys with a basic composition (weight %): 18cr - 0.01 c - 0.2 si - 0.4 mn, and levels of nickel varying from zero to 60%. alloys in the annealed condition and after deformation at room temperature, 350 and 700°c to simulate the high temperatures achieved during machining were observed by optical microscopy. equilibrium diagrams were generated by computational thermodynamics (thermocalc) to predict the behavior of these alloys in a wide range of temperatures. the theoretical thermodynamic equilibrium conditions of the system were compared to the observed microstructures, indicating that the cfc phase in alloys with nickel content between 10% and 30% is, in fact, in a metastable condition at room temperature. martensitic transformation induced by cold work in the alloy with 10% ni was observed, validating the computer calculations.
Dissatisfaction with the Health Service and Non-Adherence to Antihypertensive Medication Treatment in Brazil*  [PDF]
Mayckel da Silva Barreto, Gabriela Schiavon Ganassin, Laura Misue Matsuda, Sonia Silva Marcon
Open Journal of Nursing (OJN) , 2015, DOI: 10.4236/ojn.2015.51006
Abstract: Purpose: Possibly the dissatisfaction with health services influences the non-adherence to medication treatment process. However, such association needs further investigation to extrapolate its results to different groups, for instance, those using only public health services. The aim of the study was to investigate the association between dissatisfaction with the public health service and non-adherence to antihypertensive pharmacotherapy. Methods: Cross-sectional descriptive study. 392 patients with hypertension participated; these were undergoing outpatient treatment at Primary Health Care, in a city of Brazil. Data collection occurred between December 2011 and March 2012 through home visits with the application of semi-structured questionnaire. Results: The majority of the interviewed were satisfied with the care received. However, it was found that there was association between non-adherence to pharmacotherapy and dissatisfaction with the reception service, scheduling appointment, care received from the health team, solvability of health problems, group activities, and physician professional. Conclusion: When health professionals do not aim for a service of quality that promotes user’s satisfaction with the health service, it cannot reach good levels of adherence to therapy.
Ferrroelectric phase transitions and the Ising model
Barreto, F. C. Sá;
Brazilian Journal of Physics , 2000, DOI: 10.1590/S0103-97332000000400027
Abstract: the ising model has been an important theoretical tool in the understanding of phase transitions in ferroelectric materials. we first review how it relates to the underlying physics of order-disorder phase transitions in these systems, as well as mean-field results for the spontaneous polarization and the dielectric constant near the critical temperature. for hydrogen-bonded ferroelectrics, a term of interaction with an external transverse field is necessary to account for proton tunneling between the two minima of a double-well potential. finally, we discuss both experimental and theoretical results for the problems of proton-lattice interactions, central peak dynamics, dynamical behavior of pseudo-one-dimensional ferroelectrics and pressure effects on hydrogen bonded ferroelectrics.
Ferrroelectric phase transitions and the Ising model
Barreto F. C. Sá
Brazilian Journal of Physics , 2000,
Abstract: The Ising model has been an important theoretical tool in the understanding of phase transitions in ferroelectric materials. We first review how it relates to the underlying physics of order-disorder phase transitions in these systems, as well as mean-field results for the spontaneous polarization and the dielectric constant near the critical temperature. For hydrogen-bonded ferroelectrics, a term of interaction with an external transverse field is necessary to account for proton tunneling between the two minima of a double-well potential. Finally, we discuss both experimental and theoretical results for the problems of proton-lattice interactions, central peak dynamics, dynamical behavior of pseudo-one-dimensional ferroelectrics and pressure effects on hydrogen bonded ferroelectrics.
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