Síntese de nanopartículas de sulfeto de cobre, preparação e estabilidade coloidal de fluidos trocadores de calor em meio aquoso

Pós-graduação em Química - IQ

Stabilization of a (3+1)-dimensional soliton in a Kerr medium by a rapidly oscillating dispersion coefficient

Using the numerical solution of the nonlinear Schrodinger equation and a variational method it is shown that (3 + 1)-dimensional spatiotemporal optical solitons can be stabilized by a rapidly oscillating dispersion coefficient in a Kerr medium with cubic nonlinearity. This has immediate consequence in generating dispersion-managed robust optical soliton in communication as well as possible stabilized Bose-Einstein condensates in periodic optical-lattice potential via an effective-mass formulation. We also critically compare the present stabilization with that obtained by a rapid sinusoidal oscillation of the Kerr nonlinearity parameter.

Analysis of the four wave mixing effect (FWM) in a dispersion decreasing fiber (DDF) for a WDM system

We did a numerical investigation of the propagation of short light pulses in the region of 1.55 mu m and the conversion efficiency (CE) for the four wave mixing generation (FWM) of ordinary and dispersion decreasing fibers for use in wavelength division multiplexing (WDM) systems, Our simulations studies three different profiles, linear, hyperbolic. and constant, One conclude that for all the profiles there is decrease of the conversion efficiency with the increase in the channel separation. The hyperbolic profile present a higher efficiency of around 1000 above in magnitude compared with the others profiles at 0.2 nm of channel separation. We calculate the conversion efficiency versus the fiber length for the three profiles. The conversion efficiency for the hyperbolic profile is higher when compared to the constant and linear profiles. The other interesting point of the hyperbolic profile is that the increase of the CE in the beginning of the fiber does not show my oscillation in the CE value (log eta), which was observed for the constant and linear profiles. For all the profiles there is an increase of the conversion efficiency with the increase of the pump power. The compression factor C-i for the generated FWM signal at omega(3) was measured along the DDF's and the constant profile fibers. One can conclude that with the use of decreasing dispersion profile (DDF) fibers one can have a control of the (CE) conversion efficiency and the compression factor of the four wave mixing (FWM) generation in WDM systems. (c) 2005 Elsevier B.V. All rights reserved.

Rheological Properties of a Sodium Bentonite and Lactose Aqueous Dispersion

Aim of this paper is show the viscosity measure of a sodium bentonite-water-lactose mixture and your rheological behaviour. This analysis showed the formation of tridimensional structure type and formation of stratified silicate/lactose, this occurred due to different concentrations of organic products into mixture and due to a difference of rotation during viscosity measument. Formation of networks is a consequence of the attraction between the silicate layers in water-lactose mixture. In the present work aqueous solutions of lactose with concentration of 7%, 5%, 3%, 1% and 0% (wt %) were used.

Dynamics and Heterogeneity of Pb(II) Binding by SiO2 Nanoparticles in an Aqueous Dispersion

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Dispersion of Seeds of Tree Species by the Leaf-Cutting Ant Acromyrmex subterraneus molestans (Hymenoptera: Formicidae) in Vicosa, Minas Gerais State, Brazil

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Selection of surfactant compounds to enhance the dispersion of Beauveria bassiana

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Use of glass transition temperature for stabilization of board's cracks of Eucalyptus grandis

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

Delays in stabilization or in reforms? The debt crisis

Empirical analyses attributing the 1980s' debt crisis to inconsistent stabilization policies rest on an inappropriate long-run approach. Revising this long-run approach yields opposite results: terms of trade shocks and foreign indebtedness explain this crisis, regardless of domestic stabilization policies. This prompts us to consider a new hypothesis, of delays in trade-policy reforms, with a model in which terms-of-trade variation (under shocks) is endogenous to export structure and efficiency of resource allocation. Evidence from the structural equations model shows that allocation distortions negatively affect changes in terms of trade, which then explain this crisis. A political economy extension demonstrates that income inequality and regional trade policy determine the distortions, which in turn leads to this crisis.

Enhanced stabilization of aerosol-OT surfactant monolayer upon interaction with small amounts of bovine serum albumin at the air-water interface

An investigation is made of the influence from small amounts of the protein bovine serum albumin (BSA) on the lateral organization of low molecular weight surfactant sodium bis-2-ethylhexyl sulfosuccinate (AOT) at the air-water interface. Surface pressure (pi - A), surface potential (DeltaV - A) and Brewster angle microscopy (BAM) experiments were carried out, with particular emphasis on the monolayer stability under successive compression-expansion cycles. AOT monolayer is not stable at the air-water interface, which means that the majority of AOT molecules go into the aqueous subphase as monomers and/or normal micelles. When a waiting time elapses between spreading and compression, the surfactant monolayer tends to reorganize partially at the air-water interface, with a monolayer expansion being observed for waiting times as large as 12 h. The incorporation of very small amount of BSA (10(-9) M) at the interface, also inferred from BAM, increases the monolayer stability as revealed by pi - A and DeltaV - A results. For a waiting time of circa 3 h, the mixed monolayer reaches its maximum stability. This must be related to protein (and/or protein-surfactant complexes) adsorbed onto the AOT monolayer, thus altering the BSA conformation to accommodate its hydrophobic/hydrophilic residues. Furthermore, the effects from such small amounts of BSA in the monolayer formation and stabilization mean that the AOT monolayer responds cooperatively to BSA. (C) 2004 Elsevier B.V. All rights reserved.

Dispersion capacity of Triatoma sherlocki, Triatoma juazeirensis and laboratory-bred hybrids

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Effects of carbon nanotube fillers dispersion on mechanical behavior of phenolic/carbon nanotube nanocomposite

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

Numeric simulation of pollutant dispersion by a control-volume based on finite element method

The dispersion of pollutants in the environment is an issue of great interest as it directly affects air quality, mainly in large cities. Experimental and numerical tools have been used to predict the behavior of pollutant species dispersion in the atmosphere. A software has been developed based on the control-volume based on the finite element method in order to obtain two-dimensional simulations of Navier-Stokes equations and heat or mass transportation in regions with obstacles, varying position of the pollutant source. Numeric results of some applications were obtained and, whenever possible, compared with literature results showing satisfactory accordance. Copyright (C) 2010 John Wiley & Sons, Ltd.

The structure and optical dispersion of the refractive index of tellurite glass

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Modified stabilization method for the tibial tuberosity advancement technique: a biomechanical study

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