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Publications
2011
de Araujo GR, de Faria KG, de Lima WG, da Padua BC, Rossoni J, Chianca-Junior DA, Silva ME, Pedrosa ML, Chaves MM, Costa DC.
The synthesis and characterization of two-dimensional (2D) molecular crystals composed of long and linear phosphonic acids atop graphene is reported. Using scanning probe microscopy in combination with first-principles calculations, we show that these true 2D crystals are oriented along the graphene armchair direction only, thereby enabling an easy determination of graphene flake orientation. We have also compared the doping level of graphene flakes via Raman spectroscopy. The presence of the molecular crystal atop graphene induces a well-defined shift in the Fermi level, corresponding to hole doping, which is in agreement with our ab initio calculations.
. 1st ed. Ouro Preto-MG: UFOP - Universidade Federal de Ouro Preto; 2011 pp. 106.Abstract
O livro reúne conjunto de análises para a produção de material didático para o curso de Pedagogia, modalidade a distância, do Centro de Educação Aberta e a Distância da Universidade Federal de Ouro Preto.
Tribological, electrochemical and tribo-electrochemical behaviour of bare and nitrided Ti6Al4V alloy was studied. Scanning Electron Microscopy (SEM), X-ray diffraction and microhardness profile were used to characterize the nitrided Ti6Al4V. The anticorrosive properties of nitrided Ti6Al4V in phosphate buffer saline solution (PBS), simulating the body environment, were evaluated by Electrochemical Impedance Spectroscopy (EIS). Nitriding increased the alloy resistance to corrosion and to dry wear. Resistance to tribocorrosion in PBS at the open circuit potential (OCP) for the nitrided alloy was also significantly increased compared to the bare alloy; nevertheless at an anodic potential this influence became less important. (c) 2011 Elsevier Ltd. All rights reserved.
O Problema da Programação de Horários Escolares (PPHE) é classificado como NP-Difícil e heurísticas para sua solução são alvo de diversas pesquisas na área de computação, matemática e pesquisa operacional. Normalmente, o problema é resolvido através de abordagens metaheurísticas como Algoritmos Genéticos, SimulatedAnnealing e GRASP. O presente trabalho propõe uma abordagem alternativa. Pretende-se reduzir do problema ao problema da Satisfazibilidade Proposicional (SAT) e resolvê-lo usando um resolvedor SAT para geração de uma solução inicial. Como não é viável tratar todos os requisitos PPHE através de satisfazibilidade, posteriormente, aplicar-se-á uma Busca Tabu para otimização da solução obtida. A eficiência da abordagem é avaliada comparando-a a abordagens conhecidas na literatura.
This article discusses the organization of collaborative processes in the context of distance learning through digital learning environments. It focuses the issue of the efficiency and effectiveness for such environments do not become spaces in which to work the information without warranty of interaction and development of knowledge. This discussion was organized from digital data collected in one forum in the discipline Knowledge, Technology and Collaborative Processes, specialization in Tutor in Distance Learning, developed by Open and Distance Center, Ouro Preto Federal University. The public is tutor teachers tutors (presential and distance), as well as coordinators of the poles of Open University from Brazil. This work approach education long life and recognize implementation of reflexive practice around context of work and study of participants.
Key-words: digital learning environments – distance learning-inservice teachers training - collaborative processes.
ETHNOPHARMACOLOGICAL RELEVANCE: Baccharis trimera (Less.) (Asteraceae) is a native plant of Brazil. Also known as "carqueja", it has been popularly used to treat liver diseases, diabetes, as well as digestive disorders. Other studies have described the hepatoprotective, antioxidant and anti-inflammatory activities of the species.
AIM OF THE STUDY: The aim of the present study was to investigate the antioxidant properties of Baccharis trimera in the neutrophils of Fisher rats in both in vitro and in vivo experimental models.
MATERIAL AND METHODS: In the in vitro assay, the neutrophils of male rats were isolated and incubated with Baccharis trimera extract at concentrations of 0.5, 5.0 and 50.0 microg/mL. In the in vivo assay, male rats were first treated with crude extract 600 mg/kg body weight of Baccharis trimera or with 50 mg/kg body weight of quercetin (reference substance) and then treated with 835 mg/kg of acetaminophen (APAP) after 24 h.
RESULTS: The hydroethanolic extract of Baccharis trimera reduced the release of reactive oxygen species in the neutrophils in both the in vitro and in vivo experimental models. Therefore confirming its antioxidant effect.
CONCLUSION: The results of this study confirm the antioxidant effect of Baccharis trimera.
Na modalidade de educação à distância os processos de gestão devem oferecer a possibilidade da relação entre os recursos tecnológicos e os recursos humanos para que o processo de aprendizagem possa ocorrer de forma facilitada. Nesta modalidade a dinâmica do processo de aprendizagem é complexa e envolve diferentes atores, como professores, tutores, alunos, técnicos e coordenadores, que estão em diferentes espaços e tempo para o desenvolvimento das atividades. A tecnologia deve oferecer suporte aos diferentes processos envolvidos na organização, planejamento e execução de todas as etapas do processo de ensino e aprendizagem, determinando a necessidade do desenvolvimento de métodos e técnicas. Este trabalho teve como objetivo demonstrar o processo de gestão da tecnologia e dos processos de ensino que auxiliam o desenvolvimento de atividades de um curso de graduação à distância oferecido por uma universidade pública. Serão apresentados os modelos do processo de gestão acadêmico/administrativos e tecnológica, e uma discussão sobre a complexidade da dinâmica da gestão.
Palavras chave: tecnologia, educação à distância, gestão da EaD, aprendizagem.
A widely used mathematical tool in the study of discrete-time systems is the Z-transform. It can be understood as the discrete-equivalent to the Laplace transform, although an intimate connection between Z, Laplace and Fourier transforms exists. Among its advantages, a large class of functions that does not have Fourier transform, for example, have Z-transform. An attempt to make easy the integration of topics concerned with the transform techniques, a historic approach combined with a mathematical view of Z-transform is presented. In addition, techniques of system discretization are described, such as the Tustin transform, and a practical example is presented.
Cooperation has been widely studied when an individual strategy is adopted against all coplayers. In this context, some extra mechanisms, such as punishment, reward, memory, and network reciprocity must be introduced in order to keep cooperators alive. Here, we adopt a different point of view. We study the adoption of different strategies against different opponents instead of adoption of the same strategy against all of them. In the context of the prisoner dilemma, we consider an evolutionary process in which strategies that provide more benefits are imitated and the players replace the strategy used in one of the interactions furnishing the worst payoff. Individuals are set in a well-mixed population, so that network reciprocity effect is excluded and both synchronous and asynchronous updates are analyzed. As a consequence of the replacement rule, we show that mutual cooperation is never destroyed and the initial fraction of mutual cooperation is a lower bound for the level of cooperation. We show by simulation and mean-field analysis that (i) cooperation dominates for synchronous update and (ii) only the initial mutual cooperation is maintained for asynchronous update. As a side effect of the replacement rule, an ``implicit punishment'' mechanism comes up in a way that exploitations are always neutralized providing evolutionary stability for cooperation.
We performed an ab initio study of molecular-doped periodic assemblies of ligand-stabilized Au nanoparticles. We found that the most stable dopant positions are near the nanoparticle surfaces, away from the center of interstitial positions. The dopants provide an effective screening mechanism, strongly reducing the nanoparticles charging energies. We also found a linear dependence of the Fermi level with dopant concentration, consistent with recent experiments, up to a critical concentration. For larger concentrations, a new regime is predicted. These features are well reproduced by a simple, analytical model for the material.
Chagas heart disease (CHD), caused by Trypanosoma cruzi infection, is a significant cause of morbidity and mortality in South and Central America. Enalapril, an angiotensin converting enzyme (ACE) inhibitor, is an important drug used to ameliorate heart functional capacity and its remodelling in individuals presenting CHD. In this study, we evaluated the effects of enalapril on systemic and cardiac immune response during experimental acute CHD. C57BL/6 mice infected with 50 trypomastigote forms of T. cruzi (Colombian strain) were treated daily with enalapril (25 mg/kg) and, after 30 days, a reduction in seric levels of IFN-gamma, TNF-alpha, CCL5/RANTES and nitric oxide, but not in that of IL-10, was detected. This imbalance of cytokines reflects in a reduction of heart mononuclear infiltration and in an increasing of cardiac mast cells. Enalapril also presents a new and interesting in vitro and in vivo anti-T. cruzi activity probably acting on parasite oxidative pathway via cytochrome-P450. Our data show that enalapril exerts an important anti-T. cruzi and anti-inflammatory activity during acute CHD reducing inflammatory cells and, possibly, preventing fibrotic process in the chronic phase. Nevertheless, further studies are still necessary to clarify the mechanisms by which this drug is acting on the parasites and on the immune pathways.
A first-principles formalism is employed to investigate the effects of size and structure on the electronic and electrochemical properties of Au nanoparticles with diameters between 0.8 and 2.0 nm. We find that the behavior of the ionization potentials (IPs) and the electron affinities (EAs) as a function of cluster size can be separated into many-body and single-electron contributions. The many-body part is only (and continuously) dependent on particle size, and can be very well described in terms of the capacitance of classical spherical conductors for clusters with more the 55 atoms. For smaller clusters, molecule-like features lead the capacitance and fundamental gap to differ systematically from those of a classical conductor with decreasing size. The single-electron part fluctuates with particle structure. Upon calculating the neutral chemical potential mu(0) = (IP + EA)/2, the many-body contributions cancel out, resulting in fluctuations of mu(0) around the bulk Au work function, consistent with experimental results. The values of IP and EA changes upon functionalization with thiolated molecules, and the magnitude of the observed changes does not depend on the length of the alkane chain. The functionalization can also lead to a transition from metallic to non-metallic behavior in small nanoparticles, which is consistent with experimental observations.
The effect of temperature on nickel sulfide bioleaching was studied in the presence of mesophile (Acidithiobacillus ferrooxidans) and moderate thermophile (Sulfobacillus thermosulfidooxidans) strains and the results were discussed in terms of sulfide dissolution thermodynamics (Eh–pH diagrams) and kinetics (cyclic voltammetry). It was observed that in the pH range 1.8–2.0 the highest nickel dissolution was achieved which reached 50% for mesophiles and over 80% for moderate thermophiles. External ferrous iron addition had no effect on the metal dissolution at 34 °C, but adversely affected nickel leaching at higher temperatures. The best outcomes were accomplished with low FeSO4 additions (2.5 g/L) at 50 °C. Pyrrhotite dissolution avoided the need for external iron addition, providing Fe2+ concentrations as high as 7 g/L during bioleaching, which supports bacterial growth. Eh–pH diagrams for pentlandite and pyrrhotite show a negligible effect of temperature on the stability field of each sulfide whilst cyclic voltammetry indicated that temperature has the strongest influence on pyrrhotite oxidation. The latter along with a rapid increase in solution potential (Eh) explains the higher and faster extraction observed with S. thermosulfidooxidans.
A first-principles formalism is employed to investigate the interaction of iron oxide (FeO) with a boron nitride (BN) nanotube. The stable structure of the FeO-nanotube has Fe atoms binding N atoms, with bond length of roughly similar to 2.1 angstrom, and binding between O and B atoms, with bond length of 1.55 angstrom. In case of small FeO concentrations, the total magnetic moment is (4 mu(Bohr)) times the number of Fe atoms in the unit cell, and it is energetically favorable to FeO units to aggregate rather than randomly bind to the tube. As a larger FeO concentration case, we study a BN nanotube fully covered by a single layer of FeO. We found that such a structure has a square FeO lattice with Fe-O bond length of 2.11 angstrom, similar to that of FeO bulk, and total magnetic moment of 3.94 mu(Bohr)/Fe atom. Consistent with experimental results, the FeO covered nanotube is a semi-half-metal which can become a half-metal if a small change in the Fermi level is induced. Such a structure may be important in the spintronics context.
The biological oxidation of ferrous iron is an important sub-process in the bioleaching of metal sulfides and other bioprocesses such as the removal of H2S from gases, the desulfurization of coal and the treatment of acid mine drainage (AMD). As a consequence, many Fe(II) oxidation kinetics studies have mostly been carried out with mesophilic microorganisms, but only a few with moderately thermophilic microorganisms. In this work, the ferrous iron oxidation kinetics in the presence of Sulfobacillus thermosulfidooxidans (DSMZ 9293) was studied. The experiments were carried out in batch mode (2L STR) and the effect of the initial ferrous iron concentration (2–20 g L−1) on both the substrate consumption and bacterial growth rate was assessed. The Monod equation was applied to describe the growth kinetics of this microorganism and values of μmax and Ks of 0.242 h−1 and 0.396 g L−1, respectively, were achieved. Due to the higher temperature oxidation, potential benefits on leaching kinetics are forecasted.
The alkaline leaching kinetics of a zinc silicate ore assaying 34.1% Zn, 11.1% Fe and 22.9% SiO2 is studied in sodium hydroxide solutions. Speciation diagrams indicate zinc dissolution as [Zn(OH)4]2− and SEM analysis showed a progressive reduction in particle size during leaching which supports the shrinking particle model. The process is chemically controlled with an activation energy of 67.8 ± 9.0 kJ/mol and reaction order with respect to NaOH determined as 1.44 ± 0.46.
Cosmological N-body simulations indicate that the dark matter haloes of galaxies should be generally triaxial. Yet, the presence of a baryonic disc is believed to alter the shape of the haloes. Here we aim to study how bar formation is affected by halo triaxiality and how, in turn, the presence of the bar influences the shape of the halo. We perform a set of collisionless N-body simulations of disc galaxies with triaxial dark matter haloes, using elliptical discs as initial conditions. Such discs are much closer to equilibrium with their haloes than circular ones, and the ellipticity of the initial disc depends on the ellipticity of the halo gravitational potential. For comparison, we also consider models with initially circular discs, and find that the differences are very important. In all cases, the mass of the disc is grown quasi-adiabatically within the haloes, but the time-scale of growth is not very important. We study models of different halo triaxialities and, to investigate the behaviour of the halo shape in the absence of bar formation, we run models with different disc masses, halo concentrations, disc velocity dispersions and also models where the disc shape is kept artificially axisymmetric. We find that the introduction of a massive disc, even if this is not circular, causes the halo triaxiality to be partially diluted. Once the disc is fully grown, a strong stellar bar develops within the halo that is still non-axisymmetric, causing it to lose its remaining non-axisymmetry. In triaxial haloes in which the parameters of the initial conditions are such that a bar does not form, the halo is able to remain triaxial and the circularization of its shape on the plane of the disc is limited to the period of disc growth. We conclude that part of the circularization of the halo is due to disc growth, but part must be attributed to the formation of a bar. Bars in the halo component, which have already been found in axisymmetric haloes, are also found in triaxial ones. We find that initially circular discs respond excessively to the triaxial potential and become highly elongated. They also lose more angular momentum than the initially elliptical discs and thus form stronger bars. Because of that, the circularization that their bars induce on their haloes is also more rapid. We also analyse halo vertical shapes and observe that their vertical flattenings remain considerable, meaning that the haloes become approximately oblate by the end of the simulations. Finally, we also analyse the kinematics of a subset of halo particles that rotate in disc-like manner. These particles occupy a layer around the plane of the disc and their rotation is more important in the spherical halo than in triaxial ones. We also find that, even though the final shape of the halo is roughly independent of the initial shape, the initially triaxial ones are able to retain the anisotropy of their velocity dispersions.
O presente estudo teve como objetivo investigar quais são as preferências musicais que apresentam estudantes de ensino médio em Vitória, Espírito Santo. Para isso, foi realizada uma pesquisa com 359 alunos (53,2% mulheres e 46,8% homens), com idade entre 14 e 26 anos. Como instrumento de coleta de dados foi empregado uma versão adaptada do Questionário sobre preferência de estilos musicais (LORENZO; HERRERA; CREMADES, 2008). Os resultados mostram que existe uma clara preferência destes estudantes pelos estilos presentes na música popular, bem como uma recusa de estilos da música erudita. Além disso, o aspecto contexto mostrou-se de grande importância, tendo pouca audição aqueles estilos musicais que não faziam parte do cotidiano dos alunos.
In a previous work, chemically modified cellulose (EMC) and sugarcane bagasse (EMMB) were prepared from mercerized cellulose (MC) and twice-mercerized sugarcane bagasse (MMB) using ethylenediaminetetraacetic dianhydride (EDTAD) as modifying agent. In this work we described in detail the modification of these materials in function of reaction time and EDTAD amount in the reaction media. The resistance of ester bond at pH 1, 2, 11, and 12 was also evaluated by FTIR. The results were used to model the hydrolysis process and a kinetic model was proposed. The modified materials (EMMB and EMC) were used to adsorb Ca2+ and Mg2+ ions from aqueous single solutions. The adsorption isotherms were developed at two pH values. These materials showed maximum adsorption capacities for Ca2+ and Mg2+ ions ranging from 15.6 to 54.1 mg/g and 13.5 to 42.6 mg/g, respectively. The modified material from sugarcane bagasse (EMMB) showed larger maximum adsorption capacities than modified material from cellulose (EMC) for both metals.
. Journal of Hazardous Materials. 2010;176(1):856-863.Abstract
This work describes the preparation of a new chelating material derived from wood sawdust, Manilkara sp., and not only the use of a new support, but also a chemically modified sugarcane bagasse synthesized in our previous work to remove Zn2+ from aqueous solutions and electroplating wastewater. The first part describes the chemical modification of wood sawdust and sugarcane bagasse using ethylenediaminetetraacetic dianhydride (EDTAD) as modifying agent in order to introduce carboxylic acid and amine functional groups into these materials. The obtained materials such as the modified sugarcane bagasse, EB, and modified wood sawdust, ES were then characterized by infrared spectroscopy (IR) and CHN. The second part evaluates the adsorption capacity of Zn2+ by EB and ES from aqueous single metal solutions and real electroplating wastewater, which concentration was determined through direct titration with EDTA and inductively coupled plasma (ICP-OES). Adsorption isotherms were developed using Langmuir model. Zn2+ adsorption capacities were found to be 80 mg/g for ES and 105 mg/g for EB whereas for the industrial wastewater these values were found to be 47 mg/g for ES and 45 mg/g for EB. Zn2+ adsorption in the wastewater was found to be lower than in Zn2+ spiked solution due to the competition between other cations and/or interference of other ions, mainly Ca2+ and Cl- that were present in the wastewater.
PINHEIRO CFS, de Mello EVL. Random Resistor Networks and Phase Separation in Superconducting Cuprates, in VII Encontro Regional da Sociedade Brasileira de Física, 2010, Uberlândia - MG. VII Encontro Regional da Sociedade Brasileira de Física, 2010, Uberlândia - MG. Univ. Federal de Uberlândia; 2010:64.
A new class of boron nitride fullerenes, which are stoichiometric and presents homopolar bonds, is proposed in this work. A combined first-principles/elastic-model approach predicts that stoichiometric fullerenes with more than 1000 atoms which present homopolar bonds are energetically more stable than those without homopolar bonds. The HOMO-LUMO gap of stoichiometric fullerenes with homopolar bonds is 1.7 eV smaller than that of fullerenes without homopolar bonds, which may lead to distinct optical and electrochemical properties. The distribution of B-B and N-N in those new fullerenes gives rise to an electric dipole moment which could make possible to separate them from apolar fullerenes. (C) 2010 Elsevier B.V. All rights reserved.
Os sistemas ferroviários têm sido amplamente utilizados para o transporte de passageiros, matérias-primas e produtos industrializados. Diversas vantagens econômicas e sociais podem ser obtidas por meio da utilização do transporte ferroviário. Especificamente, as ferrovias brasileiras têm sido submetidas a um aumento crescente de peso da carga transportada, principalmente devido a demanda das indústrias primárias e secundárias, o que também pode ser notado como uma tendência global. A infraestrutura ferroviária é afetada diretamente pelo aumento de carga, com destaque para as ferrovias de transporte de cargas pesadas (heavy haul), tal como a EFVM (Estrada de Ferro Vitória-Minas) que é utilizada essencialmente no transporte de minério de ferro. No intuito de se manter a confiabilidade e a segurança de tal sistema de transporte, evitando a ocorrência de acidentes, é necessária a realização de um procedimento preciso de manutenção. Este trabalho prop̃oe uma nova abordagem baseada em sinais acústicos medido no ar para o diagnóstico da presença de fissuras microscópicas em dormentes de aço, utilizando-se Redes Neurais Artificiais (RNAs) como ferramentas para classificação. Os resultados obtidos em laboratório forneceram uma taxa de erro de aproximadamente 6%, após a realização de validação cruzada.
A chloride-free Pd(OAc)(2)/Cu(OAc)(2) system catalyzes the oxidation of organic substrates by molecular oxygen in nonacidic methanol solutions. Terminal olefins, i.e., 1-hexene, 1-octene, styrene, and 2-vinylnaphthalene, give the corresponding methyl ketones without a significant double-bond isomerization of long-chain substrates. The catalyst also promotes an unusual allylic oxidation of sterically encumbered trisubstituted internal double bonds in acyclic polyenes able to form eta(2)-eta(2)-chelates with palladium. Linalool and nerolidol, mono- and sesquiterpenic allylic alcohols, give corresponding allylic ethers arising from the exclusive oxidation of the internal double bonds. Monosubstituted terminal double bonds in both substrates remain intact due to the deactivating effect of the allylic hydroxyl group. Dihydromyrcene, a nonfunctionalized monoterpenic diene, gives allylic ether and methyl ketone arising from the oxidation of both trisubstituted and terminal double bonds, respectively. On the other hand, internal double bonds in the substrates without a terminal olefinic bond, such as citronellol, citronellal, nerol, and citral, do not undergo oxidation under similar conditions. A steric possibility for chelation of the terminal and internal double bonds on the same palladium atom seems to be a crucial factor to determine the reactivity of the internal double bonds in these substrates toward oxidation. The presence of the second eta(2)-coordinated double bond in these chelates favors the activation of the allylic C-H bond of the olefin, which results in eta(3)-allyl intermediates and, then, in allylic ethers. Nerol, a primary allylic alcohol, is oxidized to (Z)-citral, although the process is complicated by further nonselective transformations of citral. All oxygenated terpenic derivatives obtained in the present work have a pleasant scent with a flower or fruit tinge and are potentially useful as components of synthetic perfumes.
O objetivo principal deste artigo é analisar quais são os conhecimentos dos alunos de EducaçãoSecundária Obrigatória (ESO) sobre o conceito de estilo musical e os diferentes estilos musicais existentes. Na Espanha, este nível educativo compreende alunos com idades entre 12 e 16 anos.Nesta pesquisa, participaram 667 alunos da cidade espanhola de Melilla (51,6% mulheres e 48,4%homens), pertencentes às quatro séries que formam essa etapa educativa. Em função de sua origem cultural, 55,9% eram de origem berbere, 39,1% de origem europeia e 4,9% mista. Como instrumento de coleta de dados se empregou uma versão adaptada do Questionário sobre conhecimento de estilo musical, de Lorenzo e Herrera (2001). Os resultados mostram que existe uma clara contradição entre as músicas que se trabalham no currículo escolar oficial (música clássica, predominantemente)e o conhecimento sobre os estilos musicais que aparecem majoritariamente na vida cotidiana dos estudantes (pop, rock & roll, hip-hop, rap ou reggaeton).
In this study, thin cobalt films were electrodeposited directly onto n-Si (100) using two different electrodeposition techniques: galvanostatic and potentiostatic. The morphological difference between galvanostatic and potentiostatic deposits was observed by atomic force microscopy (AFM) and X-ray diffraction (XRD). Analysis of the deposits by an alternating gradient field magnetometer (AGFM) showed the influence of the electrodeposition process on the magnetic properties of the film.
Diamond-like carbon films (DLC) were deposited on titanium substrates in acetonitrile and N, N-dimethyl formamide (DMF) liquids by the liquid-phase electrodeposition technique at ambient pressure and temperature. The applied voltage between the electrodes was high ( 1200 V) due to the use of resistive organic liquids. The surface morphology was examined by Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM). Corrosion performance of the coatings was investigated by potentiodynamic polararization tests in phosphate buffer saline solution. Raman spectroscopy analysis of the films revealed two broad bands at approximately 1360 cm(1) and 1580 cm(1), related to D and G-band of DLC, respectively. The coated Ti was tested in a ball-on-plate type wear test machine with Al(2)O(3) balls. The films presented a low friction coefficient ( about 0.1), and the films deposited from DMF presented the best wear resistance. (C) 2008 Elsevier B. V. All rights reserved.
This work describes the synthesis of hydrogels of cellulose acetate (AC), with a nominal degree of substitution DS = 2.5, cross-linked with 3,3’,4,4’ benzophenonetetracarboxylic dianhydride (BTDA). The raw materials were characterized by thermal analysis (TG/DTG) and by Fourier transform infrared spectroscopy (FTIR). DS of cellulose acetate was determined by titration with a known amount of standard NaOH solution. Hydrogels of BTDA were synthesized with 0.5, 0.75 and 1.0 mol of BTDA/mol of AC. FTIR proved to be a suitable method to monitor the course of reactions and the progress of purification. UV-vis spectroscopy and analysis confirmed the esterification of the free hydroxyl groups. Surface modification of AC structure after the cross-linking reaction was analyzed by Scanning Electron Microscope (SEM) and density and porosity of the hydrogels were determined by BET. The influence of the concentration of dianhydride on the time necessary for formation of the gel was investigated. The influence from the increase in the degree of cross-linking on the thermal behavior of the material was also documented. Water absorption isotherms were obtained for hydrogels with different reticulating agents and reticulation degrees at different temperatures. The Arrhenius equation was used to determine the diffusion coefficient of the different hydrogels at distinct temperatures and the threshold energy for the swelling process. The enthalpy of mixture was determined through the measurement of the maximum quantity of water absorbed at equilibrium at different temperatures, with the Gibbs/Helmholtz equation.
. Dissertação de mestrado em Engenharia Elétrica na área de Controle, Automação e Robótica - COPPE - UFRJ. 2009.Abstract
Neste trabalho são abordados a modelagem, a identificação de parâmetros e o controle de nível de um sistema de quatro tanques. Um modelo é obtido a partir da aplicação do princípio da conservação da massa, em conjunto com a equação de Bernoulli. O modelo não linear foi apreciado e validado por comparação com os resultados experimentais. O sistema apresenta comportamento de fase não-mínima, dependendo dos valores das parcelas do fluxo de água das bombas entre os tanques. Com a linearização desse modelo observa-se que o sistema apresenta um zero de transmissão que se move ao longo do eixo real, assumindo valores negativos ou positivos. Nesse sentido, o sistema de quatro tanques é ideal para ilustrar vários conceitos relacionados ao controle multivariável, em especial às limitações de desempenho relacionadas aos zeros no semi-plano direito. Um controle por uma estrutura descentralizada é proposto, e a sintonia individual das malhas é realizada. Para a configuração de fase não-mínima faz-se necessário um novo emparelhamento de variáveis, de acordo com o resultado obtido pela análise de interação das variáveis, sob o custo de instabilidade da planta em malha fechada a não modificação do emparelhamento. Por fim, são comparados os resultados experimentais e de simulações do controle proposto.
We perform first-principles investigations of two-dimensional, triangular lattices of Au-38 nanoparticles deposited on a graphene layer. We find that lattices of thiolate-covered nanoparticles cause electronic structure modifications in graphene such as minigaps, charge transfer, and new Dirac points, but graphene remains metallic. In contrast, for a moderate coverage of nanoparticles (approximate to 0.2 nm(-2)), a lattice of bare (noncovered) Au nanoparticles may induce periodic deformations on the graphene layer leading to the opening of a band gap of a few tens of meV at the Dirac point, in such a way that a properly charged system might become a semiconductor.
The emergence of cooperation has been widely studied in the context of game theory on structured populations. Usually the individuals adopt one strategy against all their neighbors. The structure can provide reproductive success for the cooperative strategy, at least for low values of defection tendency. Other mechanisms, such as punishment, can also be responsible for cooperation emergence. But what happens if the players adopt simultaneously different strategies against each one of their opponents, not just a single one? Here we study this question in the prisoner dilemma scenario structured on a square lattice and on a ring. We show that if an update rule is defined in which the players replace the strategy that furnishes the smallest payoff, a punishment response mechanism against defectors without imputing cost to the punishers appears, cooperation dominates and, even if the tendency of defection is huge, cooperation still remains alive.
Succinylated mercerized cellulose (cell 1) was used to synthesize an anion exchange resin. Cell 1, containing carboxylic acid groups was reacted with triethylenetetramine to introduce amine functionality to this material to obtain cell 2. Cell 2 was reacted with methyl-iodide to quaternize the amine groups from this material to obtain cell 3. Cells 2 and 3 were characterized by mass percent gain, degree of amination and quaternization, FTIR and CHN. Cells 2 and 3 showed degrees of amination and quaternization of 2.8 and 0.9 mmol/g and nitrogen content of 6.07% and 2.13%, respectively. Cell 3 was used for Cr (VI) adsorption studies. Adsorption equilibrium time and optimum pH for Cr (VI) adsorption were found to be 300 min and 3.1, respectively. The Langmuir isotherm was used to model adsorption equilibrium data. The adsorption capacity of cell 3 was found to be 0.829 mmol/g. Kinetic studies showed that the rate of adsorption of Cr (VI) on cell 3 obeyed a pseudo-second-order kinetic model.
This study describes the preparation of two new chelating materials, MMSCB 3 and 5, derived from succinylated twice-mercerized sugarcane bagasse (MMSCB 1). MMSCB 3 and 5 were synthesized from MMSCB 1 using two different methods as described by Gurgel and Gil (2009). In the first method MMSCB 1 was activated with 1,3-diisopropylcarbodiimide and in the second with acetic anhydride (to form an internal anhydride) and later both were reacted with triethylenetetramine in order to obtain MMSCB 3 and 5. New obtained materials were characterized by mass percent gain, concentration of amine groups, FTIR, and elemental analysis. MMSCB 3 and 5 showed mass percent gain of 19.9 and 57.1%, concentration of amine groups of 2.0 and 2.1 mmol/g, and nitrogen content of 5.8 and 4.4%. The capacity of MMSCB 3 and 5 to adsorb Cu2+, Cd2+, and Pb2+ from aqueous single metal ion solutions was evaluated at different contact times, pHs, and initial metal ion concentrations. Adsorption isotherms were well fitted by Langmuir model. Maximum adsorption capacities of MMSCB 3 and 5 for Cu2+, Cd2+, and Pb2+ were found to be 59.5 and 69.4, 86.2 and 106.4, 158.7 and 222.2 mg/g, respectively.
This work describes the preparation of new chelating materials derived from cellulose and sugarcane bagasse for adsorption of Cu2+, Cd2+, and Pb2+ ions from aqueous solutions. The first part involved the mercerization treatment of cellulose and sugarcane bagasse with NaOH 5 mol/L. Non- and mercerized cellulose and sugarcane bagasse were then reacted with ethylenediaminetetraacetic dianhydride (EDTAD) in order to prepare different chelating materials. These materials were characterized by mass percent gain, X-ray diffraction, FTIR, and elemental analysis. The second part consisted of evaluating the adsorption capacity of these modified materials for Cu2+, Cd2+, and Pb2+ ions from aqueous single metal solutions, whose concentration was determined by atomic absorption spectroscopy. These materials showed maximum adsorption capacities for Cu2+, Cd2+, and Pb2+ ions ranging from 38.8 to 92.6 mg/g, 87.7 to 149.0 mg/g, and 192.0 to 333.0 mg/g, respectively. The modified mercerized materials showed larger maximum adsorption capacities than modified non-mercerized materials.
This study describes the preparation of two new chelating materials derived from succinylated mercerized cellulose (cell 1). Cell 1 was activated through two different methods by using diisopropylcarbodiimide and acetic anhydride (to form an internal anhydride) and reacted with triethylenetetramine in order to obtain cell 2 and 4. New modified celluloses were characterized by mass percent gain, concentration of amine functions, elemental analysis, and infrared spectroscopy. Cell 2 and 4 showed degrees of amination of 2.8 and 2.3 mmol/g and nitrogen content of 6.07% and 4.61%, respectively. The capacity of cell 2 and 4 to adsorb Cu2+, Cd2+, and Pb2+ ions from single aqueous solutions were examined. The effect of contact time, pH, and initial concentration of metal ions on the metal ions uptake was also investigated. Adsorption isotherms were well fitted by the Langmuir model. The maximum adsorption capacity of cell 2 and 4 were found to be 56.8 and 69.4 mg/g for Cu2+; 68.0 and 87.0 mg/g for Cd2+; and 147.1 and 192.3 mg/g for Pb2+, respectively.
. Journal of Environmental Engineering. 2009;135(5):341-350.Abstract
This paper describes the preparation of new adsorbents derived from sugarcane bagasse and wood sawdust (Manilkara sp.) to
remove zinc (II) ions from electroplating wastewater. The first part deals with the chemical modification of sugarcane bagasse and wood sawdust, using succinic anhydride to introduce carboxylic acid functions into the material. The obtained materials (modified sugarcane bagasse MB2 and modified wood sawdust MS2) were then characterized by infrared spectroscopy (IR) and used in adsorption experiments. The adsorption experiments evaluates Zn2+ removal from aqueous single metal solution and real electroplating wastewater on both batch and continuous experiments using fixed-bed columns prepared in laboratorial scale with the obtained adsorbents. Adsorption isotherms were then developed using Langmuir model and the Thomas kinetic model. The calculated Zn2+ adsorption capacities were found to be 145 mg/g for MS2 and 125 mg/g for MB2 in single metal aqueous solution, whereas for the industrial wastewater these values were 61 mg/g for MS2 and 55 mg/g for MB2.
. Mathematical Problems in Engineering [Internet]. 2009;1(08/2009):1-18. WebsiteAbstract
This work deals with the analysis and design of a reaction thruster attitude control for the Brazilian Multimission platform satellite. The three-axis attitude control systems are activated in pulse mode. Consequently, a modulation of the torque command is compelling in order to avoid high nonlinear control action. This work considers the Pulse-Width Pulse-Frequency (PWPF) modulator which is composed of a Schmidt trigger, a first-order filter, and a feedback loop. PWPF modulator holds several advantages over classical bang-bang controllers such as close to linear operation, high accuracy, and reduced propellant consumption. The Linear Gaussian Quadratic (LQG) technique is used to synthesize the control law during stabilization mode and the modulator is used to modulate the continuous control signal to discrete one. Numerical simulations are used to analyze the performance of the attitude control. The LQG/PWPF approach achieves good stabilization-mode requirements as disturbances rejection and regulation performance.
BACKGROUND: There is a large increase in the number of elderly people in modern societies. This demographic phenomenon has been paralleled by an epidemic of chronic diseases and inflammatory processes usually associated with advanced age.
OBJECTIVE: We studied the role of protein kinase A (PKA), protein kinase B (Akt/PKB) and p38 mitogen-activated protein kinase (p38 MAPK) signaling pathways in ROS produced by neutrophils induced by pro-interferon-gamma (IFN-gamma) or anti-inflammatory interleukin 10 (IL-10) cytokines age-related.
METHODS: The ROS generation was studied in healthy subjects in age ranging from 20 to 80 years old divided in five age groups: (20-39), (40-49), (50-59), (60-69) and (70-80) years old. ROS production was quantified in a luminol-dependent chemiluminescence assay and the results were expressed as relative light units/min).
RESULTS: ROS production in human neutrophil was activated by IFN-gamma in all the groups studied. This activation was down-regulated by IL-10. The inhibitory effect of IL-10 on 20-49 years old group was reversed by the pre-treatment with H89 (PKA inhibitor) but not with PD169316 (p38 MAPK inhibitor). This differential effect of IL-10 associated with age was not observed with the neutrophil pre-treatment with Akt/PKB or NADPH-oxidase inhibitor (DPI). Lack of IL-10 effect on ROS production was observed in older subjects (50-80 years old). The effect of IL-10 showed a significant inhibition of ROS production similar to those got with PD169316 alone as compared to that of p38 MAPK.
CONCLUSION: The results suggest that inhibitory effect of the ROS production mediated by IL-10 depends on PKA for the younger and the lack effect on the elderly is p38 MAPK dependent.
. Solid State Communications. 2009;149(5-6):222-226.Abstract
The synthesis and characterization of two-dimensional (2D) molecular crystals composed of long and linear phosphonic acids atop graphene is reported. Using scanning probe microscopy in combination with first-principles calculations, we show that these true 2D crystals are oriented along the graphene armchair direction only, thereby enabling an easy determination of graphene flake orientation. We have also compared the doping level of graphene flakes via Raman spectroscopy. The presence of the molecular crystal atop graphene induces a well-defined shift in the Fermi level, corresponding to hole doping, which is in agreement with our ab initio calculations.
Tribological and corrosion properties of Ti6Al4V alloy both bare and coated by diamond-like carbon (DLC) were investigated in PBS solution. The films obtained by a PACVD technique present high hardness, good corrosion and wear resistance and lower friction coefficient compared to bare alloy. Tribocorrosion tests on bare alloy showed that when wear stops, the alloy rapidly passivates. DLC films present superior wear resistance under dry conditions. However, film life is greatly reduced during tribocorrosion tests.
TRIBOCORROSION OF Ti6Al4V ALLOY IN PHOSPHATE BUFFERED SALINE SOLUTION. The tribocorrosion behavior of Ti6Al4V alloy was investigated in a Phosphate Buffered Saline (PBS) solution by a reciprocating wear, using alumina ball as the counterface material, at different normal forces and sliding velocities. Dry wear experiments were performed in order to compare with the tribocorrosion experiments at open circuit potential and under anodic polarization. Dry wear induced a superior damage oil the counterface, forming larger and shallower wear tracks compared with those experiments performed in PBS solution. The anodic current was increased by wear; however the volume of oxidized metal in tribocorrosion experiments correspond to a relative low percentage of the wear track volume.
Crianças com paralisia cerebral podem estar impossibilitadas de realizar a comunicação verbal; escrita e manipular os dispositivos tradicionais de entrada de dados em computador (teclado e mouse); por problemas motores. O portador de necessidades especiais precisa de um ambiente alternativo com interface simples para promover a comunicação e auxiliar o processo de aprendizagem autônoma. Os ambientes de Realidade Aumentada podem oferecer interatividade; informações multimídia com imagens reais e virtuais; promover situações alternativas para a comunicação; colaboração; com intervenções em tempo real. A Realidade Aumentada torna-se, então, uma espécie de transdutor sensorial que traduz ideias e conceitos para sensações visuais e auditivas que podem ser percebidas e processadas. Este estudo teve como objetivo propor uma forma alternativa de comunicação para crianças com paralisia cerebral utilizando sistemas de realidade aumentada e com base na teoria da complexidade. Para realização do estudo foram utilizados sistemas de Realidade Aumentada e software de comunicação assistida para elaboração de ambientes de interação e comunicação destinados a cinco crianças com paralisia cerebral da primeira série do ensino fundamental de escolas públicas. As experiências realizadas mostraram que os ambientes propostos ofereceram às crianças a possibilidade de realizar atividades escolares de forma individual e coletiva; interagir com o professor e colegas de classe funcionando como um ambiente de comunicação alternativo; facilitando a percepção o entendimento de fenômenos físicos; químicos; sensações e construções mentais. Verificamos que as relações estabelecidas nos ambientes de comunicação alternativos com realidade aumentada permitem a interação e a construção de redes de ações resultando em processos dinâmicos e colaborativos.
The parasite load in cervical, mandibular, and parotid lymph nodes and in the skin of the nose and the pinna from dogs infected with Leishmania infantum were investigated by histologic and immunohistochemical studies. Twenty-two infected dogs with and without signs of infection were examined to demonstrate correlation of signs with parasite load and the correlation of facial skin lesions with parasites in regional lymph nodes. Chronic inflammation of the skin was demonstrated in infected dogs that had no gross skin lesions, confirming that normal-appearing skin can harbor the parasite, likely playing a role in transmission. Dogs with facial skin lesions showed a higher parasite load in parotid lymph nodes than dogs without lesions of the facial skin, based on Leishman-Donovan unit analysis. Based on immunohistochemical analysis, parasite load in parotid and cervical nodes was correlated with that of skin of the nose and pinna, as was the parasite load in mandibular lymph nodes and skin of the external nose. We demonstrated a logical involvement of the lymphatic vessels and their specific anatomic draining sites.
BACKGROUND: Diabetes is associated with a pro-inflammatory status characterized by an increased production of inflammatory molecules. Reactive oxygen species (ROS) and cAMP elevating agents represent two molecular systems, normally generated during inflammation. These molecules could be responsible for the alteration of signaling pathways. In the present paper we have studied the correlation between ROS generation and inositolpolyphosphates (InsP(1), InsP(2) InsP(3) and InsP(4)) released by granulocytes from Type 1 diabetic patients (DM1) in the presence or in the absence of cyclic AMP-elevating agents.
METHODS: The effect of cAMP on ROS production was quantified in a chemoluminescence assay luminol-dependent (RLU/min). InsP(1), InsP(2) InsP(3) and InsP(4) were quantified by inositol-H(3) in a Beta-counter and the results were expressed as count per minute (CPM).
RESULTS: The elevation of intracellular level of cAMP inhibited both InsP(3) and ROS production in granulocytes from healthy subjects and activated in the cells from Type 1 diabetic patients. InsP(1), InsP(2) and InsP(4) did not show significant alteration in both studied cells. There was a significant correlation between InsP(3) and ROS in the presence of elevated content of cAMP. This correlation was observed in a 15 minutes reaction for healthy subjects and in 120 minutes for DM1.
CONCLUSIONS: The importance of both InsP(3) release and ROS production in an inflammatory process and tissue pathophysiology in Type 1 diabetic patients is still under debate because hyperglycemia accelerates generation of oxidative stress and may play an important role in the development of complications in diabetes. Thus, our results demonstrated alteration in metabolic response in granulocytes from Type 1 diabetic patients and it may be important for the development of therapeutic processes and drugs that interfere with signaling of ROS generation and may contribute to the improvement of the severe complications of diabetes.
The use of additives to improve the quality of electrodeposited magnetic films is of current interest since magnetic films are widely used in data storage devices and sensors. This is a study of the influence of adding sodium saccharin in the electrodeposition of cobalt thin films on silicon, the most widely used material in magnetic recording media. Saccharin was added to the cobalt solution at three different concentrations: 10 g/l, 20 g/l and 50 g/l. The additive caused a morphological, microstructural and magnetic behaviour change in cobalt films. The levelling and brightening effect of saccharin was verified visually and by atomic force microscope. The films became single-phase structured by adding 50 g/l saccharin, on the contrary of the dual-phase structure found in the basic Co solution. The remanent magnetization (M-r) and the coercive field (H-e) of the films were improved and the metallic nuclei size decreased as the saccharin concentration increased. (c) 2008 Elsevier B.V. All rights reserved.
We study the robustness and stability of the yeast cell regulatory network by using a general inhomogeneous discrete model. We find that inhomogeneity, on average, enhances the stability of the biggest attractor of the dynamics and that the large size of the basin of attraction is robust against changes in the parameters of inho- mogeneity. We find that the most frequent orbit, which represents the cell-cycle pathway, has a better biological meaning than the one exhibited by the homogeneous model.
This work describes the preparation of new chelating material from mercerized sugarcane bagasse. The first part treats the chemical modification of non-mercerized sugarcane bagasse (SCB) and twice-mercerized sugarcane bagasse (MMSCB) with succinic anhydride. Mass percent gains (mpg) and degrees of succinylation (DS) of succinylated non- and twice-mercerized sugarcane bagasse 1 (SCB 1 and MMSCB 1) were calculated. MMSCB 1 exhibited an increase in mpg and DS of 49.2% and 0.9 mmol/g in relation to SCB 1. SCB 2 and MMSCB 2 were obtained by treatment of MMSCB 1 and SCB 1 with bicarbonate solution to release the carboxylate functions and characterized by FTIR. The second part evaluates and compares the adsorption capacity of SCB 2 and MMSCB 2 for Cu2+, Cd2+ and Pb2+ ions in an aqueous single metal solution. Adsorption isotherms were developed using Langmuir model. MMSCB 2 exhibited an increase in Qmax for Cd2+ (43.6 mg/g) and Pb2+ (83.3 mg/g) in relation to SCB 2.
This work describes the preparation of new chelating material from mercerized cellulose. The first part treats the chemical modification of non-mercerized cellulose (cell 1) and mercerized cellulose (cell 2) with succinic anhydride. Mass percent gains (mpg) and degree of succinylation (DS) of cell 3 (from cell 1) and cell 4 (from cell 2) were calculated. Cell 4 in relation to cell 3 exhibited an increase in mpg and in the concentration of carboxylic functions of 68.9% and 2.8 mmol/g, respectively. Cells 5 and 6 were obtained by treatment of cells 3 and 4 with bicarbonate solution to release the carboxylate functions and characterized by FTIR. The second part compares the adsorption capacity of cells 5 and 6 for Cu2+, Cd2+, and Pb2+ ions in an aqueous single metal solution. Adsorption isotherms were developed using Langmuir model. Cell 6 in relation to cell 5 exhibited an increase in Qmax for Cu2+ (30.4 mg/g), Cd2+ (86.0 mg/g) and Pb2+ (205.9 mg/g).
. Tendências em Matemática Aplicada e Computacional [Internet]. 2008;9(2008):321-330. WebsiteAbstract
This paper deals with the problem of 3-axis attitude stabilization of
a satellite subjected to dynamics perturbations. The controller is based on the
Linear Quadratic Gaussian control theory (LQG). The main purpose of the work
is to synthesize a control law characterized by simplicity on implementation. The
study considers the specific case of the Brazilian satellite PMM. The article presents
the system modelling, the proposed control, and analysis of simulation results.
In this paper we are concerned with some theoretical questions forthe FitzHugh-Nagumo equation. First, we recall the system, we briefly explain the meaning of the variables and we present a simple proof of the existence and uniqueness of strong solution. We also consider an optimal control problem for this system. In this context, the goal is to determine how can we act on the system in order to get good properties. We prove the existence of optimal state-control pairs and, as an application of the Dubovitski-Milyoutin formalism, we deduce the corresponding optimality system. We also connect the optimal control problem with a controllability question and we construct a sequence of controls that produce solutions that converge strongly to desired states. This provides a strategy to make the system behave as desired. Finally, we present some open questions related to the control of this equation.
The existence and uniqueness of weak solutions for a random version of a class ofnonlinear parabolic problems of nonlocal type with additive noise are studied.
We perform first-principles calculations for the interaction of the transition metal atoms Fe, Co, and W, as well as the FeO molecule, with the boron nitride fullerene B36N36. The stable structure of the atom-fullerene complexes may have the dopant atom either at the center of the cage or making covalent bonds with the fullerene wall, with similar total energies. We also find that the FeO molecule has a binding energy with the fullerene 2.5 eV larger than those of the transition metal atoms, and that it produces larger distortions in the cage. The electronic structure changes upon doping with the presence of several gap states. No magnetic moment is induced on the BN cage and, in general, the hybrid structures have the same magnetic moments as the isolated dopants.
Leishmania promastigotes interact with macrophages through the association of multiple membrane surface receptors. Macrophage complement receptor CR3 (CD11b/CD18 or Mac-1) has been implicated in the interaction of both human and murine macrophages with serum-opsonized promastigotes. The aim of this study was to determine CR3 expression in the livers and spleens of dogs naturally infected with Leishmania (Leishmania) chagasi. CR3 expression in liver was higher in asymptomatic than in symptomatic animals. Moreover, the hepatic parasitism load determined by immunocytochemical analysis was lower in parallel with higher numbers of granulomas. In contrast, in spleens, CR3 expression was higher in symptomatic animals than in asymptomatic ones. However, the tissue parasite load was greater in spleens of symptomatic dogs. There was a strict correlation between the parasite load and cellular CR3 expression in the spleens of dogs naturally infected with L. chagasi. CR3 macrophage integrins could be essential receptors for Leishmania survival. Considering that the symptomatic animals showed higher parasite loads and higher CD11b/CD18 expression in their spleens, we can conclude that these splenic cells (monocyte-macrophages) might serve to perpetuate intracellular infection.
Júnior OK, Gurgel LVA, de Melo JCP, Botaro VR, Melo TMS, de Gil RPF, Gil LF.
This work describes the preparation of new chelating materials derived from sugarcane bagasse for adsorption of heavy metal ions in aqueous solution. The first part of this report deals with the chemical modification of sugarcane bagasse with succinic anhydride. The carboxylic acid functions introduced into the material were used to anchor polyamines, which resulted in two yet unpublished modified sugarcane bagasse materials. The obtained materials were characterized by elemental analysis and infrared spectroscopy (IR). The second part of this reports features the comparative evaluation of the adsorption capacity of the modified sugarcane bagasse materials for Cu2+, Cd2+, and Pb2+ ions in aqueous single metal solution by classical titration. Adsorption isotherms were studied by the Freundlich and Langmuir models.
Linalool, a monoterpenic allylic alcohol, has been efficiently and selectively oxidized by dioxygen in methanol and ethanol solutions using a chloride-free Pd(OAc)(2)/Cu(OAc)(2) catalytic system under nonacidic conditions. Corresponding allylic ether arising from the exclusive oxidation of a trisubstituted internal double bond has been characterized as a major product in each alcohol. In methanol, this product, 7-methoxyhotrienol, was obtained in virtually quantitative yield. It is remarkable that a monosubstituted terminal double bond of the substrate remains intact. In acetic acid, catalytic palladium turnover was achieved only by using benzoquinone as a terminal oxidant, with the regioselectivity of allylic oxidation being completely switched from that in alcohols. A major product is 8-linalyl acetate, formed with up to 85% selectivity. All linalool derivatives obtained have a pleasant scent with a flower or fruit tinge and are natural products found either in exotic plants or in grape wines. To the best of our knowledge, the present work reports a first synthesis of these functionalized monoterpenes, potentially useful as components of synthetic perfumes. On the basis of the results obtained, the mechanism of this unusual oxidation reaction involving the formation of various organometallic intermediates is discussed, with bimetallic Pd-Cu catalysis being suggested.
We investigate, by means of first-principles calculations, structural and transport properties of junctions made of symmetric dithiolated molecules placed between Au electrodes. As the electrodes are pulled apart, we find that it becomes energetically favorable that Au atoms migrate to positions between the electrode surface and thiol terminations, with junction structures alternating between symmetric and asymmetric. As a result, the calculated IV curves alternate between rectifying and nonrectifying behaviors as the electrodes are pulled apart, which is consistent with recent experimental results.
BACKGROUND: It is generally agreed that elderly subjects undergo progressive deterioration of their immune responsiveness, which leads to an increased susceptibility to autoimmune processes, neoplasm and inflammation. Thus there is a general consensus that regulation of inflammation results from a balance between pro-inflammatory and anti-inflammatory pathways.
OBJECTIVE: The present study aimed to investigate the possible alterations of cyclic AMP/protein kinase A (cAMP/PKA) and p38 mitogen-activated protein kinase (p38 MAPK) pathway signaling (reactive oxygen species (ROS) generation) and inositol 1,4,5-triphosphate (InsP3) production by neutrophils during the aging process.
METHODS: Age-induced ROS generation and InsP3 production were studied in healthy subjects ranging in age from 20 to 80 years. The subjects were divided into six age groups: (I) 20-29, (II) 30-39, (III) 40-49, (IV) 50-59, (V) 60-69, and (VI) 70-80 years old. The effect of cAMP, H89 (inhibitor PKA), and PD169316 (inhibitor p38 MAPK) on ROS production was quantified in a luminol-dependent chemiluminescence assay (relative light units/min) and by InsP3 release (cpm).
RESULTS: Our results demonstrated a lack of dibutyryl cAMP inhibitory effects on ROS generation and InsP3 production by granulocytes from PKA-dependent 50-year-olds. However, the inhibitory effect of cAMP is restored in neutrophils after the age of 50 years when p38 MAPK signaling is inhibited.
CONCLUSIONS: The present study may be important towards a better understanding of the high susceptibility to infections and age-related inflammatory and deregulation diseases. The alteration of cAMP/PKA and p38 MAPK signaling pathways enhances the inflammatory process.
This article studies the existence of weak solutions for a stochastic version of the FitzHugh-Nagumo equations in a time dependent domain Q, where Q is a image of a cylinder C of Rn.
Electrodeposition appears as an option to obtain thin films of technological interest. In the present study, galvanostatic and potentiostatic deposition of cobalt films onto n-type Si(100) with two different resistivities, < 0.005 ohm cm and 50- 100 ohm cm, was performed. The influence of silicon resistivity on electrochemical parameters and on nucleation features was investigated by chronogalvanometric and chronopotentiometric curves. Atomic force microscopy characterization of the deposits indicated that electrochemical parameters and the deposition method (galvanostatic or potentiostatic) influence the morphology of the deposits. For potentiostatic deposition an instantaneous nucleation was found and the cobalt nuclei deposited onto low silicon resistivity were smaller in size and greater in quantity than those onto high silicon resistivity. For galvanostatic deposition a progressive or two-step nucleation was observed without significant influence of the substrate resistivity on deposit morphology. (c) 2005 Elsevier B.V. All rights reserved.
BACKGROUND: We compared skin biopsy samples from different anatomical regions for detecting Leishmania in dogs, using histological (HE), immunohistochemical (IHC) and polymerase chain reaction (PCR) techniques.
RESULTS: The sensitivity was 82.8 percent for PCR, 62.1 percent for IHC and 44.8 percent for HE. These methods do not appear to depend on the clinical status of the animal or the anatomical source of the skin sample; there is no "best region" for any method. However, PCR was more effective than IHC and HE for ear and nose skin samples whereas IHC was better than HE for nose samples. There was weak agreement between PCR and HE for all tissue samples; good agreement between PCR and IHC for ear and abdomen samples, and weak agreement for nose; and optimal agreement between IHC and HE for ear and abdomen and good agreement for nose samples.
CONCLUSION: The PCR on ear skin could be the best procedure for diagnosing canine visceral leishmaniasis. The good agreement between PCR and IHC indicates that IHC can be used as an alternative method. Finally, tissue samples from ears, nose and abdomen, particularly ears and nose, are potentially useful for diagnosing canine visceral leishmaniasis independently of the animal's clinical status.
We make use of first-principles calculations to study the effects of functionalization and compression on the electronic properties of 2D lattices of Au nanoparticles. We consider Au-38 particles capped by methylthiol molecules and possibly functionalized by the dithiolated conjugated molecules benzenedimethanethiol and benzenedicarbothialdehyde. We find that the nonfunctionalized lattices are insulating, with negligible band dispersions even for a compression of 20% of the lattice constant. Distinct behaviors of the dispersion of the lowest conduction band as a function of compression are predicted for functionalized lattices: The band dispersion of the benzenedimethanethiol-functionalized lattice increases considerably with compression, while that of the benzenedicarbothialdehyde-functionalized lattice decreases.
BACKGROUND: Granulocytes from healthy subjects and from patients suffering from diabetes mellitus present differences in reactivity to stimulation with cyclic nucleotide-elevating agents. The production of reactive oxygen species (ROS) is inhibited in cells from non-diabetic subjects following such stimulation, but activated through a PKA-independent signaling pathway in granulocytes from type 1 and type 2 diabetic patients. The aim of the present study was to understand better the changes in signaling mechanisms induced by the disease.
METHODS: ROS production in granulocytes from healthy subjects and from type 1 and type 2 diabetic patients was measured using a luminol-dependent chemiluminescence assay. Granulocytes were stimulated by the addition of the cAMP-elevating agent dibutyryl cAMP. In some experiments, granulocytes were pre-treated with an inhibitor of PKA or Akt/PKB prior to cAMP stimulation.
RESULTS: Intracellular elevation of cAMP induced a PKA-dependent and Akt/PKB-independent inhibition of ROS production in granulocytes from healthy subjects, but a significant activation in cells from both type 1 and type 2 diabetic patients. Most significantly, activation of ROS generation in cells from diabetic patients was shown to be Akt/PKB-dependent and PKA-independent.
CONCLUSIONS: These results suggest that chronic hyperglycaemia could induce metabolic adaptation in cAMP-related signaling mechanisms. Epac (exchange protein directly activated by cAMP) is a novel cAMP receptor besides PKA involved in different signaling pathways. The cAMP-stimulated inverse ROS response in granulocytes from type 1 and type 2 diabetic patients may be due to a change in signaling pathways from cAMP/PKA to cAMP/Epac/Akt/PKB. These preliminary results require further studies in order to evaluate their consequences on innate immunity and pathogenesis of diabetes mellitus.
The vascular effects of 7-epiclusianone on the rat aorta were investigated. In the rat aortic rings with functional endothelia, 7-epiclusianone up to 10 μM induced a concentration-dependent vasodilatation of the sustained contractions induced by phenylephrine (0.3 μM). At concentrations higher than 10 μM, 7-epiclusianone induced a concentration-dependent contraction in the aortic rings. The vasodilator effect of 7-epiclusianone was drastically decreased with L-NAME (100 μM) as well as in endothelium-denuded aortic rings. Moreover, indomethacin (10 μM) induced a significant shift to the left in the vasodilator but did not modify the vasoconstrictor effect of 7-epiclusianone. In arteries without pre-contraction, 7-epiclusianone (3–100 μM) induced concentration-dependent contraction only in endothelium-intact and in the presence of L-NAME (100 μM). This effect was inhibited by indomethacin (10 μM) and ZM230487 (1 μM), selective inhibitors of cyclooxygenase and of 5-lipoxygenase, respectively. We can conclude that at low concentrations 7-epiclusianone induces an endothelium-dependent vasodilator effect in rat aortic rings. At higher concentrations and in conditions where NO synthase was inhibited, 7-epiclusianone induces a vasocontractile effect. Nitric oxide seems to participate in the vasodilatation, while endothelial cyclooxygenase- and 5-lipoxygenase-derived products play a role in the vasoconstrictor effect.
Pinheiro CFS, Herrmann HJ, Andrade, Jr. SJ, Bernardes AT. Rede de fusíveis apoloniana, in XXIX Encontro Nacional de Física da Matéria Condensada, São Lourenço-MG, 2006. XXIX Encontro Nacional de Física da Matéria Condensada, São Lourenço-MG, 2006.; 2006.
We perform first-principles calculations to study the relative stability of boron nitride fullerenes B(n)N(m). We consider fullerenes with octahedral, icosahedral and tubular shapes, in a size range with (n + m) between 20 and 288. A scaling analysis allows the total energy comparisons to extend to larger sizes. We find that tubular-shaped fullerenes are as stable as octahedral-shaped ones for (n + m) <= 80. We also find that, in N-rich conditions, icosahedral fullerenes with line defects composed of N-N bonds may be as stable as octahedral fullerenes. (c) 2006 Elsevier B.V. All rights reserved.
We investigate, by means of first-principles calculations, the possible formation of Au-covered carbon fullerenes. Coverages between 32 and 92 Au atoms over C-60 were considered. Among those, the most stable structure is Au92C60, which retains the I-h symmetry of C-60 after geometry optimization. Au92C60 has a small formation energy per Au atom (0.65 eV), which is in fact smaller than those of the Au-38 and Au-55 gold clusters, which were already observed. Au92C60 can be further stabilized by an overlayer of methylthiol molecules, which reduces the formation energy per gold atom to a value smaller than that of the bulk phase of gold.
The hydrogenation of myrcene catalyzed by Ru, Cr, Ir and Rh complexes leads to the formation of a complex mixture of mono-, di- and trihydrogenated products. Seven major products have been characterized, showing that they arise from the sigma-alkyl and/or eta(3)-allyl intermediates formed by the reaction of metal catalysts with both terminal C=C bonds of myrcene. A good control of chemoselectivity has been achieved through the appropriate choice of the metal and reaction conditions. Monohydrogenated products have been obtained with excellent combined selectivity of 95-98% at a high conversion of myrcene (> 80%). Among the catalysts studied, rhodium complexes show the highest activity and selectivity, especially at temperatures lower than 100 degrees C. (c) 2005 Elsevier B.V. All rights reserved.
Sol-gel palladium silica composites are active catalysts for the selective hydrogenation of myrcene. The temperature of the thermal treatment of the catalyst is essential for its selectivity. Catalysts treated at 1100 degrees C give monohydrogenated products with excellent combined selectivity of 90-95% at almost complete conversion of the substrate. The obtained products arise from the or-alkyl and/or eta(3)-allyl intermediates formed by the interaction of the palladium catalyst with both terminal C=C bonds of myrcene and the main products (ca. 70%) result from the reaction with the less substituted one. The selective monohydrogenation of myrcene could be useful to produce a mixture of diolefins of different reactivity, which could be further transformed to oxygenated derivatives with selectivities better than myrcene itself. (c) 2005 Elsevier B.V All rights reserved.
