X-ray scattering studies of mixed langmuir monolayers and Langmuir-Blodgett films of a noncentrosymmetric porphyrin with cadmium arachidate

The structures of mixed Langmuir (floating) monolayers and Langmuir-Blodgett (LB) films of a phenanthroline-porphyrin with cadmium arachidate (PhenPor + CdAr) have been investigated by synchrotron X-ray grazing incidence diffraction (GIXD) and specular X-ray reflectivity (SXR). GIXD measurements of the floating monolayers showed only one peak, arising from the CdAr domains in the films, at a scattering angle of 21.5 degrees. This is consistent with a hexagonal structure (alpha = 4.77 Angstrom). The correlation length in these domains is 250 Angstrom. GMD measurements of the LB films, however, show two sets of diffraction features: one arises from CdAr domains with a rectangular in-plane structure (alpha = 7.44 Angstrom and b = 4.90 Angstrom) and a correlation length of 85 Angstrom; the other is from porphyrin domains with an oblique in-plane structure (alpha (p) 15.2 Angstrom, b(p) = 8.86 Angstrom, and gamma (p) = 80 degrees) and a correlation length of 105 Angstrom. These dimensions are consistent with the surface pressure-area isotherm measurements and indicate that the two components are immiscible. The thickness of the bilayer is 57 Angstrom, and there is no correlation between the bilayers. Introduction of a trigger compound does not alter the structure of the films but slightly increases the bilayer thickness. The SXR measurements of the floating monolayers also support the suggested immiscibility of the two components in the films.

Recent advances in processing and characterization of periodic mesoporous MCM-41 silicate molecular sieves

The discovery of periodic mesoporous MCM-41 and related molecular sieves has attracted significant attention from a fundamental as well as applied perspective. They possess well-defined cylindrical/hexagonal mesopores with a simple geometry, tailored pore size, and reproducible surface properties. Hence, there is an ever-growing scientific interest in the challenges posed by their processing and characterization and by the refinement of various sorption models. Further, MCM-41-based materials are currently under intense investigation with respect to their utility as adsorbents, catalysts, supports, ion-exchangers, and molecular hosts. In this article, we provide a critical review of the developments in these areas with particular emphasis on adsorption characteristics, progress in controlling the pore sizes, and a comparison of pore size distributions using traditional and newer models. The model proposed by the authors for adsorption isotherms and criticalities in capillary condensation and hysteresis is found to explain unusual adsorption behavior in these materials while providing a convenient characterization tool.

Aluminophosphate-based mesoporous molecular sieves: Synthesis and characterization of TAPOs

Mesoporous Ti-substituted aluminophosphates (AlPOs) with a hexagonal, cubic and lamellar pore structure, characteristic of MCM-41, MCM-48, and MCM-50, respectively, were synthesized. The stability of these mesophases upon template removal was studied. The pore structures, surface properties, and local atom environments of Al, P, and Ti of the hexagonal and cubic Ti-containing mesoporous products were extensively characterized using X-ray diffraction, magic angle spinning nuclear magnetic resonance, AAS, XPS, ultraviolet–visible, and adsorption of nitrogen and water vapor techniques while the lamellar mesophase was not further characterized due to its very poor thermal stability. Ti-containing mesoporous AlPO materials show a reasonable thermal stability upon template removal, a hydrophilic surface property, and high porosity showing application potentials in catalytic oxidation of hydrocarbons.

The crystallography and morphology of Mo2C in ferrite

The orientation relationships between hexagonal Mo2C precipitates (H) in ferrite (B) have been determined by electron diffraction to an accuracy of +/-2degrees. With one exception, the 19 results are consistent with the previously reported Pitsch and Schrader (P/S) orientation relationship. However, these more accurate determinations show clearly that there is a systematic deviation of up to 5.5degrees from the exact P/S relationship and that this deviation consists of a small rotation about the parallel close packed directions-[100](B)//[2 (1) over bar(1) over bar0](H). The long direction of the Mo2C needles has been determined unequivocally in terms of the orientation relationship to be [100](B)//[2 (1) over bar(1) over bar0](H). Moire fringes between precipitate and matrix have been used to improve the accuracy of the orientation relationship results and to determine the lattice parameters of the carbide precipitates investigated. The Moire fringe analysis has shown small systematic departures from the exact parallelism between [100](B) and [2 (1) over bar(1) over bar0](H) along the length of Mo2C needles and a lowering of the carbide lattice parameter that is consistent with the replacement of Mo by Fe in the carbide. The orientation relationship results, including the observed systematic deviation from the exact P/S relationship, are shown to be consistent with the edge-to-edge model. (C) 2002 Kluwer Academic Publishers.

Structural changes in mixed Langmuir-Blodgett films upon nanoparticle formation

The formation of CdS nanoparticles by reacting mixed Langmuir-Blodgett films of arachidic acid and either octadecylamine or dimethyldioctadecylammonium nitrate on a cadmium-containing subphase with hydrogen sulfide gas has resulted in the identification of a number of structural changes, observed using grazing incidence X-ray diffraction. In the case of octadecylamine, the structure after reaction is a hexagonal close-packed array of surfactant-stabilized nanoclusters, with a lattice constant of a = 17.65 Angstrom. In both octadecylamine and dimethyldioctadecylammonium nitrate films, the presence of a unit cell tilted at 38degrees to the plane of the substrate was found. Despite these changes, the average nanoparticle size was unaffected by the addition of either second component to the film.

Characterization of the acidic properties of mesoporous aluminosilicates synthesized from leached saponite with additional aluminum incorporation

The acidic properties of hexagonal mesoporous aluminosilicates synthesized via a new successful short time synthesis route using leached saponite and a low concentration of surfactant are thoroughly investigated. The resulting aluminosilicate mesoporous materials with high Si/Al ratios of around 11 have a maximal surface area of 1130 m(2)/g, a pore volume of 0.92 cm(3)/g, and a narrow pore size distribution at around 3 nm. The replacement of the sodium ions, present as counterions in the synthesized aluminosilicates, with protons imparts useful catalytic acidity. This acidity is extensively studied with FTIR spectroscopy after adsorption of ammonia and cyclohexylamine, while deuterated acetonitrile differentiates between Bronsted and Lewis acidity. Al-27 NMR spectroscopy determined the coordination of the aluminum in the FSM materials. Simultaneously the effect of an additional Al incorporation, utilizing sodium aluminate, aluminum nitrate, and aluminum isopropoxide is studied. From an acidic point of view, the incorporation with Al(NO3)(3) appears to be the most optimal, as the sample has a very high amount of acid sites (1.3 mmol/g). Investigating the nature of the acid sites it is found that in all samples except the one incorporated with Al(NO3)(3), more Bronsted than Lewis sites are present, both sites being quite acidic as they resist desorption temperatures up to 300 degreesC. Probing the coordination and location of the Al atoms, all the catalysts appeared to have mostly tetrahedral aluminum, up to 95% of the total Al amount for the proton exchanged AI(NO3)(3) incorporated sample.

Effect of the number of shells on the pressure and energy of two-dimensional free bubble clusters

We have performed Surface Evolver simulations of two-dimensional hexagonal bubble clusters consisting of a central bubble of area lambda surrounded by s shells or layers of bubbles of unit area. Clusters of up to twenty layers have been simulated, with lambda varying between 0.01 and 100. In monodisperse clusters (i.e., for lambda = 1) [M.A. Fortes, F Morgan, M. Fatima Vaz, Philos. Mag. Lett. 87 (2007) 561] both the average pressure of the entire Cluster and the pressure in the central bubble are decreasing functions of s and approach 0.9306 for very large s, which is the pressure in a bubble of an infinite monodisperse honeycomb foam. Here we address the effect of changing the central bubble area lambda. For small lambda the pressure in the central bubble and the average pressure were both found to decrease with s, as in monodisperse clusters. However, for large,, the pressure in the central bubble and the average pressure increase with s. The average pressure of large clusters was found to be independent of lambda and to approach 0.9306 asymptotically. We have also determined the cluster surface energies given by the equation of equilibrium for the total energy in terms of the area and the pressure in each bubble. When the pressures in the bubbles are not available, an approximate equation derived by Vaz et al. [M. Fatima Vaz, M.A. Fortes, F. Graner, Philos. Mag. Lett. 82 (2002) 575] was shown to provide good estimations for the cluster energy provided the bubble area distribution is narrow. This approach does not take cluster topology into account. Using this approximate equation, we find a good correlation between Surface Evolver Simulations and the estimated Values of energies and pressures. (C) 2008 Elsevier B.V. All rights reserved.

Microscopia eletrônica de varredura de ovos de Haemagogus leucocelaenus (Diptera: Culicidae)

OBJETIVO: Observar detalhes morfológicos de ovos de Haemagogus leucocelaenus visualizados pela primeira vez por microscopia eletrônica de varredura (MEV) e realizar morfometria das principais estruturas. MÉTODOS: Foram utilizados ovos de Hg. leucocelaenus provenientes de fêmeas capturadas na Reserva Biológica do Tinguá, RJ, sendo parte destinada à eclosão e outra ao processamento de MEV, dos quais três foram submetidos à análise morfométrica. O material foi fixado em glutaraldeído 2,5% e pós-fixado em tetróxido de ósmio 1%, ambos em tampão cacodilato de sódio 0.1M, pH 7.2, processado e observado ao MEV Jeol 5310. Medições foram realizadas com o auxílio do software de análise Semafore. RESULTADOS: Os ovos apresentaram contorno elíptico com aproximadamente 574 µm de comprimento e 169 µm de largura, sendo o índice do ovo (l/wratio) 3,39 µm. O exocório é extremamente regular, possuindo ornamentação hexagonal e algumas vezes pentagonal. Nas células coriônicas, observaram-se tubérculos simetricamente dispostos com relação ao eixo longitudinal, e, no interior delas, tubérculos menores, individualizados, dispostos na periferia, e poucos agrupados no centro. A superfície do retículo coriônico não apresentou rugosidades. O aparelho micropilar apresenta colar proeminente, contínuo, com disco micropilar bem evidente. CONCLUSÕES: A ornamentação do exocório apresenta diferenças em relação aos tubérculos das células coriônicas e ao retículo coriônico externo entre os ovos de Hg. leucocelaenus comparados aos ovos de Hg. janthinomys e Hg. equinus, bem como com relação aos de Aedes aegypti, Ae. albopictus e Ae bahamensis.

Leptonic mixing, family symmetries, and neutrino phenomenology

Tribimaximal leptonic mixing is a mass-independent mixing scheme consistent with the present solar and atmospheric neutrino data. By conveniently decomposing the effective neutrino mass matrix associated to it, we derive generic predictions in terms of the parameters governing the neutrino masses. We extend this phenomenological analysis to other mass-independent mixing schemes which are related to the tribimaximal form by a unitary transformation. We classify models that produce tribimaximal leptonic mixing through the group structure of their family symmetries in order to point out that there is often a direct connection between the group structure and the phenomenological analysis. The type of seesaw mechanism responsible for neutrino masses plays a role here, as it restricts the choices of family representations and affects the viability of leptogenesis. We also present a recipe to generalize a given tribimaximal model to an associated model with a different mass-independent mixing scheme, which preserves the connection between the group structure and phenomenology as in the original model. This procedure is explicitly illustrated by constructing toy models with the transpose tribimaximal, bimaximal, golden ratio, and hexagonal leptonic mixing patterns.

Thermodynamic pathway for the formation of SnSe and SnSe2 polycrystalline thin films by selenization of metal precursors

In this work, tin selenide thin films (SnSex) were grown on soda lime glass substrates by selenization of dc magnetron sputtered Sn metallic precursors. Selenization was performed at maximum temperatures in the range 300 °C to 570 °C. The thickness and the composition of the films were analysed using step profilometry and energy dispersive spectroscopy, respectively. The films were structurally and optically investigated by X-ray diffraction, Raman spectroscopy and optical transmittance and reflectance measurements. X-Ray diffraction patterns suggest that for temperatures between 300 °C and 470 °C, the films are composed of the hexagonal-SnSe2 phase. By increasing the temperature, the films selenized at maximum temperatures of 530 °C and 570 °C show orthorhombic-SnSe as the dominant phase with a preferential crystal orientation along the (400) crystallographic plane. Raman scattering analysis allowed the assignment of peaks at 119 cm−1 and 185 cm−1 to the hexagonal-SnSe2 phase and those at 108 cm−1, 130 cm−1 and 150 cm−1 to the orthorhombic-SnSe phase. All samples presented traces of condensed amorphous Se with a characteristic Raman peak located at 255 cm−1. From optical measurements, the estimated band gap energies for hexagonal-SnSe2 were close to 0.9 eV and 1.7 eV for indirect forbidden and direct transitions, respectively. The samples with the dominant orthorhombic-SnSe phase presented estimated band gap energies of 0.95 eV and 1.15 eV for indirect allowed and direct allowed transitions, respectively.

Mecanismos de gestão de recursos humanos no setor público: as implicações da austeridade

Dissertação de Mestrado apresentada ao Instituto Politécnico do Porto para cumprimento dos requisitos necessários à obtenção do grau de Mestre em Gestão das Organizações – Ramo de Gestão de Empresas Orientador: Professor Doutor Pedro Nunes Orientador: Professor Henrique Curado

Zonal distribution of gold and platinium group elements in the Mondunguara deposits Mozambique

The Mondunguara copper mines are situated in mountainous terrain in west-central Mozambique. The mineralization consists of chalcopyrite, pyrrhotite, common pcntlandite, cobaltpentlandite, pyrite and several minor oxides and sulphides in tabular ore bodies deeping steep to the north. Gold was known to occur in small quantities but no systematic sampling and analysis for precious clements was ever done. Mineralogical and geological evidence has shown that the ores are magmatic in origin and were derived from gabbro-peridotitic magma dykes saturated in sulphides when intruded. The ore bodies show a clear zonation. Platinum group elements as well as pure gold are associated with high temperature hexagonal pyrrhotite. This pyrrhotite being of no use is generally discarded to the tailing dumps. Late hydrothermal phases are enriched in native silver, silver tellurides as well as electrum.

Printed electronics for ubiquitous computing applications

Dissertação para obtenção do Grau de Doutor em Química

Desenvolvimento de um sensor colorimétrico em papel para a deteção de bactérias eletroquimicamente ativas

Bactérias eletroquimicamente ativas possuem a capacidade de transferir eletrões extracelularmente, durante a respiração celular. Esta característica tem sido atualmente explorada para aplicação na produção de eletricidade, tratamento de águas residuais, biorremediação e em diversas áreas da biotecnologia, onde a transferência eletrónica ocorre na presença de aceitadores insolúveis (tais como, óxidos metálicos e ânodos metálicos). Contudo, o número de espécies identificadas, isoladas e caracterizadas até à data é bastante reduzido. Os métodos atualmente disponíveis para deteção de bactérias eletroquimicamente ativas são morosos, dispendiosos e complexos de operar, tornando-se necessário o desenvolvimento de outros métodos mais rápidos, simples e menos dispendiosos que auxiliem na otimização das aplicações mencionadas. O objetivo principal deste trabalho foi o desenvolvimento de um sensor colorimétrico de papel utilizando um material eletrocrómico, trióxido de tungsténio, como camada ativa para a deteção destas bactérias. Para isso, foram definidos no papel poços delimitados por barreiras hidrofóbicas, através da impressão e difusão de uma camada de cera. As várias amostras de nanopartículas de WO3, sintetizadas por um método hidrotermal assistido por micro-ondas, foram depositadas nos poços por drop casting. As nanopartículas com estrutura cristalográfica hexagonal, impregnadas no sensor de papel, foram capazes de detetar com sucesso uma bactéria eletroquimicamente ativa, Geobacter sulfurreducens, desde uma fase de crescimento bastante inicial (Abs600 nm = 0,1, correspondente a 0,07 g/L com um rácio RGB de 1,10 ± 0,040) até à fase exponencial-tardia (Abs600 nm = 0,5, correspondente a 0,33 g/L com um rácio RGB de 1,33 ± 0,005), com P <0,0001. O sensor de papel e respetivo método de deteção colorimétrico desenvolvido neste trabalho, revelou ser sensível e específico à deteção destas bactérias, de uma forma rápida, simples e pouco dispendiosa.