Selective Allylic oxidation of Cyclohexene by a Magnetically Recoverable Cobalt Oxide Catalyst

In this work, we prepared a new magnetically recoverable CoO catalyst through the deposition of the catalytic active metal nanoparticles of 2-3 nm on silica-coated magnetite nanoparticles to facilitate the solid separation from liquid media. The catalyst was fully characterized and presented interesting properties in the oxidation of cyclohexene, as for example, selectivity to the allylic oxidation product. It was also observed that CoO is the most active species when compared to Co(2+), Co(3)O(4) and Fe(3)O(4) in the catalytic conditions studied.

Interactions of Electrons and Rydberg Atoms in Ultra-Cold Plasmas

This thesis discusses an experimental technique for investigating electron temperature control by Rydberg atoms in ultra-cold plasmas. The objective we set ourselves was twofold. Firstly, we sought to gain an insight into the processes whereby the creation of Rydberg atoms within the plasma lengthens the lifetime of the plasma. To this end, we created the plasma using a Littman dye laser and subsequently, at a variable time delay, we excited neutral atoms in the plasma to specific Rydberg states using a narrow bandwidth pulsed dye laser. Secondly, we employed radio-frequency (rf) electric fields to excite electron oscillations within the plasma in order to infer such information as plasma density and electron temperature. Although we found that the introduction of high angular momentum Rydberg states did lengthen the plasma lifetime we were not able to differentiate between the temperature moderation effect due to the Rydberg atoms cooling the plasma, and the binding effect due to an increased positive space charge within the plasma.

Ondas e instabilidades em plasmas com inomogeneidades suaves na densidade e no campo magnético de equilíbrio

No presente trabalho, estudamos a absorção e amplificação de ondas eletromagnéticas que se propagam em plasmas com densidade e temperatura fracamente inomogêneas, imersos em um campo magnético também inomogêneo, tendo como base a teoria cinética, dentro do contexto da aproximação local. Esse estudo se dá efetivamente a partir da obtenção do tensor dielétrico do plasma, que deve ser empregado na relação de dispersão. Iniciamos com uma revisão dos conceitos básicos sobre plasmas homogêneos e inomogêneos. Os fundamentos da teoria cinética também foram abordados. Apresentamos uma revisão de trabalhos anteriores que enfocam o mesmo tema, embora descrevendo separadamente os dois tipos de inomogeneidades. A partir desses trabalhos, obtivemos um tensor dielétrico geral, que descreve de forma simultânea as inomogeneidades do campo magnético de equilíbrio e da função distribuição de equilíbrio.Tal tensor foi obtido a partir de um sólido desenvolvimento teórico, que garante a correta descrição da troca de energia entre as ondas e as partículas do plasma. Abordamos os aspectos gerais das instabilidades de deriva, direcionando o estudo à faixa de frequência das ondas híbridas inferiores, e às instabilidades LHDI e MTSI (IWI). Utilizamos perfis lineares de inomogeneidades de campo magnêtico ambiente e densidade para modelar a região da magnetosfera conhecida como neutral sheet. Particularizamos o tensor dielétrico para o estudo específico das instabilidades LHDI e MTSI (IWI), para o tipo de perfil citado acima. Apresentamos uma nova rela»c~ao de dispers~ao para plasmas inomogêneos, que incorpora explicitamente as derivadas espaciais do tensor dielétrico do plasma. Usamos o tensor que unifica os tratamentos das inomogeneidades do campo e densidade nessa relação de dispersão, e obtivemos uma descrição unificada das instabilidades LHDI e MTSI (IWI).

Intake and performance of confined crossbred heifers fed different lipid sources

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

Qualitative characteristics of meat from confined crossbred heifers fed with lipid sources

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

Use of repellents for honeybees (Apis mellifera L.) in vitro in the yellow passion-fruit (Passiflora edulis Deg) crop and in confined beef cattle feeders

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

Teoria cinética não extensiva: efeitos físicos em gases e plasmas

The standard kinetic theory for a nonrelativistic diluted gas is generalized in the spirit of the nonextensive statistic distribution introduced by Tsallis. The new formalism depends on an arbitrary q parameter measuring the degree of nonextensivity. In the limit q = 1, the extensive Maxwell-Boltzmann theory is recovered. Starting from a purely kinetic deduction of the velocity q-distribution function, the Boltzmann H-teorem is generalized for including the possibility of nonextensive out of equilibrium effects. Based on this investigation, it is proved that Tsallis' distribution is the necessary and sufficient condition defining a thermodynamic equilibrium state in the nonextensive context. This result follows naturally from the generalized transport equation and also from the extended H-theorem. Two physical applications of the nonextensive effects have been considered. Closed analytic expressions were obtained for the Doppler broadening of spectral lines from an excited gas, as well as, for the dispersion relations describing the eletrostatic oscillations in a diluted electronic plasma. In the later case, a comparison with the experimental results strongly suggests a Tsallis distribution with the q parameter smaller than unity. A complementary study is related to the thermodynamic behavior of a relativistic imperfect simple fluid. Using nonequilibrium thermodynamics, we show how the basic primary variables, namely: the energy momentum tensor, the particle and entropy fluxes depend on the several dissipative processes present in the fluid. The temperature variation law for this moving imperfect fluid is also obtained, and the Eckart and Landau-Lifshitz formulations are recovered as particular cases

A new oxovanadium(IV)-cucurbit[6]uril complex: Properties and potential for confined heterogeneous catalytic oxidation reactions

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Optical and electrical properties of polymerizing plasmas and their correlation with DLC film properties

Diamond-like carbon (DLC) films were grown from radiofrequency plasmas of acetylene-argon mixtures, at different excitation powers, P. The effects of this parameter on the plasma potential, electron density, electron temperature, and plasma activity were investigated using a Langmuir probe. The mean electron temperature increased from about 0.5 to about 7.0 eV while the mean electron density decreased from about 1.2x10(9) to about 0.2x10(9) cm(-3) as P was increased from 25 to 150 W. Both the plasma potential and the plasma activity were found to increase with increasing P. Through actinometric optical emission spectrometry, the relative concentrations of CH, [CH], and H, [H], in the discharge were mapped as a function of the applied power. A rise in [H] and a fall in [CH] with increasing P were observed and are discussed in relation to the plasma characteristics and the subimplantation model. The optical properties of the films were calculated from ultraviolet-visible spectroscopic data; the surface resistivity was measured by the two-point probe method. The optical gap, E(G), and the surface resistivity, rho(s), fall with increasing P. E(G) and rho(s) are in the ranges of about 2.0-1.3 eV and 10(14)-10(16) Omega/square, respectively. The plasma power also influences the film self-bias, V(b), via a linear dependence, and the effect of V(b) on ion bombardment during growth is addressed together with variation in the relative densities of sp(2) and sp(3) bonds in the films as determined by Raman spectroscopy.

Optical and electrical diagnostics measurements of plasmas generated in aromatic compounds

Plasmas generated in de discharges in aromatic compounds have been used for several years in polymerization processes. The chemical kinetics developed in such a plasma environment are extremely complicated. Therefore it is extremely important to set up optical and electrical diagnostics in order to establish the kinetics of the film growth, In this work we studied de plasmas generated ill low-pressure atmospheres of benzene for different values of gas pressure and power coupled to the discharge. The pressure range varied from 0.2 to 1.0 mbar for electric power running from 4 to 25 W, the main chemical species observed within the discharge were CH, H and C. It was observed that the CH relative concentration increases continuously with the power in the range investigated. The electron temperature varied from 0.5 to 2.0 eV with the increase of the power, for a fixed value of gas pressure. The relative dielectric constant of the plasma polymerized benzene was kept around 4.8 from 100 Hz to 10 kHz, presenting a resonance near 25 kHz. This electric behaviour of the film was the same fur different conditions of polymeric film deposition, (C) 1997 Elsevier B.V. S.A.