Structural and optical properties of Zn0.9 Mn0.1 O/ZnO core-shell nanowires designed by pulsed laser deposition

Partilhar documento na coleção da comunidade Laboratório Associado I3NCore-shell ZnO/ZnMnO nanowires on a-Al2O3 and GaN (buffer layer)/Si (111) substrates were fabricated by pulsed laser deposition using a Au catalyst. Two ZnO targets with a Mn content of 10% were sintered at 1150 and 550 °C in order to achieve the domination in them of paramagnetic MnO2 and ferromagnetic Mn2O3 phases, respectively. Cluster mechanism of laser ablation as a source of possible incorporation of secondary phases to the wire shell is discussed. Raman spectroscopy under excitation by an Ar+ laser revealed a broad peak related to the Mn-induced disorder and a redshift in the A1-LO phonon. Resonant Raman measurements revealed an increase in the multiphonon scattering caused by disorder in ZnO upon doping by Mn. Besides the UV emission, a vibronic green emission band assisted by a ∼ 71 meV LO phonon is also observed in the photoluminescence spectra. Core-shell structures with smooth shells show a high exciton to green band intensity ratio ( ∼ 10) even at room temperature. © 2009 American Institute of PhysicsSANDiE Network of Excellence of the EUFCT-PTDC/FIS/72843/200

First Record Of Sclerocarpus Africanus Jacq. (asteraceae, Heliantheae) For South America

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Sclerocarpus, a genus belonging to subtribe Helianthinae (Asteraceae, Heliantheae), is recognized by the pales surrounding its ovary and sometimes part of the corolla and becoming thickened and hardened at maturity, usually developing tubercles on the surface. The genus comprises eight species from which seven are American mainly distributed in Mexico and Central America. This work provides the first register of the genus for South America, by recording Sclerocarpus africanus in the Bahia state, northeast of Brazil. The results include description and illustration for the species. © 2016 Check List and Authors.126CNPq, Conselho Nacional de Desenvolvimento Científico e TecnológicoBOL0565/2015, FAPESB, Fundação de Amparo à Pesquisa do Estado da BahiaConselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Simulated Tempering: A New Monte Carlo Scheme

We propose a new global optimization method ({\em Simulated Tempering}) for simulating effectively a system with a rough free energy landscape (i.e. many coexisting states) at finite non-zero temperature. This method is related to simulated annealing, but here the temperature becomes a dynamic variable, and the system is always kept at equilibrium. We analyze the method on the Random Field Ising Model, and we find a dramatic improvement over conventional Metropolis and cluster methods. We analyze and discuss the conditions under which the method has optimal performances.Comment: 12 pages, very simple LaTeX file, figures are not included, sorr

Optimized cross-slot flow geometry for microfluidic extension rheometry

A precision-machined cross-slot flow geometry with a shape that has been optimized by numerical simulation of the fluid kinematics is fabricated and used to measure the extensional viscosity of a dilute polymer solution. Full-field birefringence microscopy is used to monitor the evolution and growth of macromolecular anisotropy along the stagnation point streamline, and we observe the formation of a strong and uniform birefringent strand when the dimensionless flow strength exceeds a critical Weissenberg number Wicrit 0:5. Birefringence and bulk pressure drop measurements provide self consistent estimates of the planar extensional viscosity of the fluid over a wide range of deformation rates (26 s1 "_ 435 s1) and are also in close agreement with numerical simulations performed by using a finitely extensible nonlinear elastic dumbbell model

Adubação verde e plantio direto: alternativas de manejo agroecológico para a produção agrícola familiar sustentável.

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BRS Carimbó: a nova cultivar de cupuaçuzeiro da Embrapa Amazônia Oriental.

bitstream/item/55594/1/COM-232.pd