Investigação de concretos afetados pela reação álcali-agregado e caracterização avançada do gel exsudado

A crescente preocupação com a qualidade e durabilidade das estruturas de concreto tem gerado grandes avanços na tecnologia do concreto, porém existem muitas questões ligadas aos processos de deterioração ainda a serem esclarecidas. Entre os vários processos que afetam a durabilidade do concreto, encontra-se a reação álcali-agregado (RAA), um fenômeno bastante complexo, mas que foi descoberto há muitos anos, porém responsável por ter afetado mais de 140 barragens no mundo. Ainda não se dispõe de uma maneira totalmente eficiente e econômica de combater a reação, uma vez instalada no concreto. A presente pesquisa aborda, do ponto de vista científico e tecnológico, o tema RAA. A investigação se deu em três etapas. Na primeira, o objetivo principal foi estudar aproximadamente cem testemunhos de concreto, provenientes de uma estrutura de usina hidrelétrica já afetada pela RAA, e verificar o reflexo desta patologia nas suas propriedades como a resistência à compressão, à tração, módulo de elasticidade, velocidade de pulsos ultra-sônicos e permeabilidade. Em conjunto, foram realizados ensaios para avaliar expansões residuais e investigações microscópicas com o objetivo de verificar os agentes causadores da reação. Na segunda etapa, o agregado quartzito, proveniente da região da usina hidrelétrica avaliada, foi estudado, desde análises microscópicas, ensaios de expansão em argamassas e concretos até a determinação das propriedades de concretos confeccionados em laboratório. As propriedades avaliadas foram as mesmas dos testemunhos. Nas duas primeiras etapas realizadas, o papel do lítio também foi abordado com o objetivo de verificar a sua eficiência no combate a RAA Por fim, na terceira etapa, foi realizado um amplo estudo do gel exsudado coletado na superfície do concreto da estrutura deteriorada pela RAA. O estudo envolveu desde a sua simples caracterização através da determinação de suas propriedades até uma caracterização avançada fazendo-se o emprego de técnicas como a difração de raios X, microscopia eletrônica de varredura, análise térmica, espectroscopia no infravermelho e espectroscopia de ressonância nuclear magnética. Nesta etapa, o lítio também foi abordado com o objetivo de se verificar o seu efeito no gel exsudado. Os resultados com os testemunhos de concreto indicam que houve reflexos negativos em algumas propriedades devido a RAA, destacando o módulo de elasticidade. Verificou-se ainda a existência de expansões residuais nos testemunhos de concreto extraídos quando expostos a determinadas condições ambientais. Nos ensaios de expansão com os testemunhos, o lítio se mostrou capaz de reduzir em parte as expansões residuais nos testemunhos de concreto estudados. Adicionalmente, o agregado quartzito provou ser bastante reativo, chegando a expansões de 0,24% nas argamassas pelo método acelerado e 0,09% nos prismas de concreto, nas idades de 16 e 365 dias, respectivamente. Entre as propriedades estudadas nos concretos moldados, e atacados em laboratório, verificou-se também que o módulo de elasticidade foi a propriedade mais afetada no tempo. Ainda o lítio nesta etapa também mostrou algum efeito positivo nas expansões. No estudo do gel exsudado, foi possível caracterizá-lo como um silicato de potássio hidratado com grande potencialidade para expandir. A partir principalmente da ressonância nuclear magnética, verificou-se que o potássio faz parte da estrutura do gel enquanto que o sódio se apresenta combinado na forma de trona, um produto cristalizado que se encontra segregado na rede do silicato de potássio amorfo. O lítio em contato com o gel se mostrou capaz de afetar a sua estrutura através das alterações observadas por ressonância nas ligações do silício.

Contribuição ao estudo do envelhecimento de ligantes asfálticos : influência da adição de polímeros e comportamento frente a radiação uv

A malha rodoviária brasileira apresenta-se, em sua maior extensão, em má condições de serventia. Uma das alternativas para se evitar deformações permanentes e trincamentos no pavimento é a adição, a quente e em reatores especiais, de polímeros ao asfalto. Esta prática já é realizada no Brasil há alguns anos, porém ainda não se tem um domínio do assunto, principalmente no caso da modificação de ligantes asfálticos brasileiros. O objetivo deste trabalho é avaliar a influência de algumas propriedades do polímero modificador no envelhecimento do ligante asfáltico modificado. Para tanto se realizou inicialmente um estudo sobre o mecanismo de envelhecimento de ligantes puros, inclusive frente a radiação ultravioleta do sol, e em seguida utilizou-se a mesma metodologia para avaliar o papel do polímero neste processo. Além disso, relacionou-se através de um projeto de experimentos a massa molar e teor de estireno do polímero SBS linear com suas propriedades clássicas, estabilidade, temperatura de transição vítrea e morfologia. Observou-se que a simulação de envelhecimento UV em laboratório, desenvolvida neste estudo, foi extremamente satisfatória. Os processos de foto-oxidação e termooxidação resultam em mecanismos diferentes de envelhecimento. A origem e composição química dos ligantes é de suma importância no mecanismo de envelhecimento UV destes. A massa molar e o teor de estireno do polímero modificador representam propriedades importantes para a estabilidade e durabilidade do ligante asfáltico modificado.

Compressibilidade da matéria nuclear em estrelas de nêutrons

Neste trabalho, são discutidos modelos da hadrodinâmica quântica com aproximação de campo médio aplicados a estrelas de nêutrons. O modelo de Walecka define o ponto de partida para desenvolver o modelo de acoplamento derivativo ajustável. A presente dissertação visa a um estudo detalhado sobre a influência dos parâmetros do modelo ajustável no sistema, analisando seus limites, inclusive quando os parâmetros são iguais a zero ou infinito (modelo exponencial). Esta análise tem o propósito de estabelecer um conjunto de parâmetros que defina um modelo que esteja de acordo com as propriedades fenomenológicas tais como módulo de compressão da matéria nuclear, massa efetiva na saturação da matéria nuclear e também algumas propriedades estáticas globais das estrelas de nêutrons como, por exemplo, massa e raio. Estabelecido o modelo a ser considerado, a autora dessa dissertação introduz, como inovação, a compressibilidade hadrônica como função da densidade. Tradicionalmente, determinam-se propriedades da matéria apenas para a densidade de saturação.

Modificação superficial de filmes de poliéster usando plasma a baixa temperatura

A polyester film has a vast application field, due some properties that are inherent of this kind of material such as, good mechanical resistance, chemical resistance to acids and bases and low production cost. However, this material has some limitations as low superficial tension, flat surface, low affinity to dyers, and poor adhesion which impede the use of the same ones for some finality as good wettability. Among the existent techniques to increase the superficial tension, plasma as energy source is the more promising technique, because of their versatility and for not polluting the environment. The plasma surface polymeric modification has been used for many researchers, because it does not affect the environment with toxic agents, the alterations remains only at nanometric layers and this technique shows expressive results. Then, due to its good acceptance, polyester films were treated with oxygen plasma varying the treatment time from 10 to 60 min with an increase of 10 min to each subsequent treatment. Also, the samples were treated with a gas mixture (nitrogen + oxygen) varying the percentage of each gas the mixture from 0 to 100%, the treatment time remaining constant to all treatments (10 min). After plasma treatment the samples were characterized by contact angle, surface tension, Raman spectroscopy, Infrared attenuated total reflection (IR-ATR) and atomic force microscopy, with the aim to study the wettability increase of treated polyester films as its variables. In the (O2/N2) plasma treatment of polyester films can be observed an increase of superficial roughness superior to those treated by O2 plasma. By the other hand, the chemical modification through the implantation of polar groups at the surface is obtained more easily using O2 plasma treatment

Compósitos de matriz metálica à base níquel com adição de TaC e NbC produzidos via metalurgia do pó

Carbide reinforced metallic alloys potentially improve some important mechanical properties required for the overall use of important engineering materials such as steel and nickel. Nevertheless, improved performance is achieved not only by composition enhancement but also by adequate processing techniques, such as novel sintering methods in the case of powder metallurgy. The method minimizes energy losses in addition to providing uniform heating during sintering. Thus, the general objective of this study was to evaluate the density, hardness, flexural strength, dilatometric behavior and to analyze the microstructure of metal matrix composites based nickel with addition of carbides of tantalum and / or niobium when sintered in a conventional furnace and Plasma assisted debinding and sintering (PADS). Initially, were defineds best parameters of granulation, screening and mixing procedure. After, mixtures of carbonyl Ni and 5%, 10% and 15 wt.% NbC and TaC were prepared in a Y-type mixer under wet conditions during 60 minutes. The mixtures were then dried and granulated using 1.5 wt. % paraffin diluted in hexane. Granulates were cold pressed under 600 MPa. Paraffin was then removed from the pressed pellets during a pre-sintering process carried out in a tubular furnace at 500 °C during 30 min. The heating rate was 3 ºC/min. The pellets were then sintered using either a plasma assisted reactor or a conventional resistive tubular furnace. For both methods, the heating rate was set to 8 ºC/min up to 1150 °C. The holding time was 60 minutes. The microstructure of the sintered samples was evaluated by SEM. Brinell hardness tests were also carried out. The results revealed that higher density and higher hardness values were observed in the plasma-assisted sintered samples. Hardness increased with the concentration of carbides in the Ni-matrix. The flexural strength also increased by adding the carbides. The decline was larger for the sample with addition of 5% 5% TaC and NbC. In general, compositions containing added carbide 10% showed less porous and more uniform distribution of carbides in the nickel matrix microstructural appearance. Thus, both added carbide and plasma sintering improved density, hardness, flexural strength and microstructural appearance of the composites

Pirólise termoquímica de pós da fibra de coco seco em um reator de cilindro rotativo para produção de bio-óleo

This master thesis aims at developing a new methodology for thermochemical degradation of dry coconut fiber (dp = 0.25mm) using laboratory rotating cylinder reactor with the goal of producing bio-oil. The biomass was characterized by infrared spectroscopy with Fourier transform FTIR, thermogravimetric analysis TG, with evaluation of activation energy the in non-isothermal regime with heating rates of 5 and 10 °C/min, differential themogravimetric analysis DTG, sweeping electron microscopy SEM, higher heating value - HHV, immediate analysis such as evaluated all the amounts of its main constituents, i.e., lignin, cellulose and hemicelluloses. In the process, it was evaluated: reaction temperature (450, 500 and 550oC), carrier gas flow rate (50 and 100 cm³/min) and spin speed (20 and 25 Hz) to condensate the bio-oil. The feed rate of biomass (540 g/h), the rotation of the rotating cylinder (33.7 rpm) and reaction time (30 33 min) were constant. The phases obtained from the process of pyrolysis of dry coconut fiber were bio-oil, char and the gas phase non-condensed. A macroscopic mass balance was applied based on the weight of each phase to evaluate their yield. The highest yield of 20% was obtained from the following conditions: temperature of 500oC, inert gas flow of 100 cm³/min and spin speed of 20 Hz. In that condition, the yield in char was 24.3%, non-condensable gas phase was 37.6% and losses of approximately 22.6%. The following physicochemical properties: density, viscosity, pH, higher heating value, char content, FTIR and CHN analysis were evaluated. The sample obtained in the best operational condition was subjected to a qualitative chromatographic analysis aiming to know the constituents of the produced bio-oil, which were: phenol followed by sirigol, acetovanilona and vinyl guaiacol. The solid phase (char) was characterized through an immediate analysis (evaluation of moisture, volatiles, ashes and fixed carbon), higher heating value and FTIR. The non-condensing gas phase presented as main constituents CO2, CO and H2. The results were compared to the ones mentioned by the literature.

Efeitos biológicos in vitro de agentes físicos utilizados em fisioterapia

The uses of radiobiocomplexes labeled with technetium-99m contributed to health science advances. Stannous chloride (SnCl2) has been used as a reducing agent for the labeling process. Cytotoxic and genotoxic effect of the SnCl2 have been described in several studies and with this experimental models alterations in molecular and cellular level can be evaluated. In the last years the physicals therapists acquired new devices which emits electromagnetic radiation such us Extremely Low Frequency Pulsated Electromagnetic Fields (E.L.F. P.E.M.F.), radiofrequency, Intense Pulsed Light (I.P.L.) and others which emits sonic waves such us Biorresonance. Scientific evidence of the effects and dosage is important to protect public health and to reach exposition levels that result in significant biological effects. The aim of this project is to verify the effects of these physical agents in plasmid DNA and E. coli AB1157 cultures in presence or absence of SnCl2 and the effects in blood constituents labeled with technetium-99m. Wistar rats blood was exposed to the cited sources and the labelling of blood constituents with 99mTc was carried through. Cultures of E. coli AB1157 and plasmidial samples DNA had been also exposed the physical agents. The results suggest that these agents are capable of altering neither the survival of E. coli cells or plasmid DNA electrophoresis mobility. The multidiscipline character was clearly in this study due the interaction between Nuclear Medicine department of the UERJ and the Laboratory of Physical Agents of the Maimonides University in Argentina until the union between the teacher (biomedical and physiotherapist) and student (physiotherapist), besides collaborators of the area of Physics and Biology, promoting new ideas and perspectives and also adding the knowledge of different areas and origins

Efeitos de um extrato aquoso de lantana camara (Cambará de espinho) na marcação de constituintes sanguíneos com técnecio-99m e na morfologia de hemácias de ratos-wistar

Medicinal plants have been studied and used in the world. Lantana camara has medicinal properties and it has been used in folk medicine. The aim was to verify the effect of a lantana extract on the labeling of blood constituents with 99mTc, and to evaluate the effect of an aqueous extract of Lantana camara on the morphology of RBC withdrawn from Wistar rats. The results showed that lantana extract has decreased the fixation of radioactivity on the IF-P. This effect was not observed in the BC compartment and in IF-BC. The BC-%ATI was decreased in all concentrations tested when the BC was washed. The osmotic fragility assay and morphological analysis were carried out. In presence of the extract, the data obtained indicated that (i) an increase of the hemolysis and (ii) modifications on the morphology of RBC. These effects of the Lantana camara could be associated with some pharmacological properties of the chemical compounds of this studied extract

Identificação e fatores de virulência de Candida spp isoladas da cavidade bucal de transplantados renais do hospital universitário Onofre Lopes em Natal-RN

Despite Candida species are often human commensals isolated from various oral sites such as: tongue, cheek and palatal mucosa plus subgingival region, there are some properties linked to the organism commonly known as virulence factors which confer them the ability to produce disease. Oral candidiasis is one of the main oral manifestations reported in literature related to kidney transplant patients. The objectives of the present study were to identify and investigate virulence factors of yeasts isolated from the oral cavity of kidney transplant recipients admitted at the Hospital Universitário Onofre Lopes, in Natal RN. Seventy Candida species isolated from 111 kidney transplant recipients were investigated in this study. Identification of the isolates was performed by using the evidence of germ tube formation, hypertonic broth, tolerance to grow at 42°C, micromorphology and biochemical profiles. We observed a high rate of isolation of yeasts from the oral cavity of kidney transplant recipients (63.1%) being C. albicans was the most prevalent species. Oral candidiasis was diagnosed in 14.4% of transplant recipients. We evaluated virulence properties of the isolates regarding to: biofilm formation on polystyrene microplates as well as XTT reduction, adherence to acrylic resin and human buccal epithelial cells and proteinase activity. Most isolates were able to form biofilm by the method of adhesion to polystyrene. All isolates of Candida spp. remained viable during biofilm formation when analyzed by the method of XTT reduction. The number of CFU attached to the acrylic resin suggested high adherence for C. parapsilosis. C. albicans isolates showed higher median adherence to human buccal epithelial cells than non-C. albicans Candida isolates. Nevertheless, this difference was not statistically significant. C. dubliniensis showed low ability to adhere to plastic and epithelial cells and biofilm formation. Proteolytic activity was observed for all the isolates investigated, including the unique isolate of C. dubliniensis. There was a statistically significant association between proteinase production and the presence of oral candidiasis. Studies related to oral candidiasis in renal transplant recipients are limited to clinical and epidemiological data, but investigations concerning Candida spp. virulence factor for this group of individuals are still scarce. We emphasize the importance of studies related to virulence factors of yeasts isolated from this population to contribute to the knowledge of microbiological aspects of oral candidiasis

Compactação do solo e intervalo hídrico ótimo no crescimento e na produtividade da cultura do milho

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

Alterações na cor e no grau de floculação de um Latossolo Vermelho-Escuro sob cultivo contínuo de cana-de-açúcar

Objetivou-se avaliar o grau de modificação de algumas propriedades físicas e da cor do horizonte superficial de um Latossolo Vermelho-Escuro textura média, submetido ao cultivo contínuo com cana-de-açúcar durante 25 anos, em Jaboticabal, SP. Os tratamentos foram constituídos por dois tipos de uso do solo, ou seja, ausência de cultivo (vegetação nativa) e cultivo intenso com cana-de-açúcar e por três profundidades no perfil, 0-10, 10-20 e 20-30cm. O cultivo intenso e contínuo alterou a cor do solo na camada de 0-10cm de 2,5YR 2,5/4 na ausência de cultivo para 2,5YR3/4 e degradou a macroestrutura, reduzindo o grau de floculação da argila do solo.

Novas configurações de monopólios planares quase-fractais para sistemas de comunicações móveis

The characteristic properties of the fractal geometry have shown to be very useful for the construction of filters, frequency selective surfaces, synchronized circuits and antennas, enabling optimized solutions in many different commercial uses at microwaves frequency band. The fractal geometry is included in the technology of the microwave communication systems due to some interesting properties to the fabrication of compact devices, with higher performance in terms of bandwidth, as well as multiband behavior. This work describes the design, fabrication and measurement procedures for the Koch quasi-fractal monopoles, with 1 and 2 iteration levels, in order to investigate the bandwidth behavior of planar antennas, from the use of quasi-fractal elements printed on their rectangular patches. The electromagnetic effect produced by the variation of the fractal iterations and the miniaturization of the structures is analyzed. Moreover, a parametric study is performed to verify the bandwidth behavior, not only at the return loss but also in terms of SWR. Experimental results were obtained through the accomplishment of measurements with the aid of a vetorial network analyzer and compared to simulations performed using the Ansoft HFSS software. Finally, some proposals for future works are presented

Obtenção de compósitos cerâmicos baseados em Al2O3/TiC através dos precursores poliméricos

The obtaining of ceramic materials from polymeric precursors is subject of numerous studies due to lower energy costs compared to conventional processing. The aim of this study is to investigate and improve the mechanism for obtaining ceramic matrix composite (CMC) based on SiOC/Al2O3/TiC by pyrolysis of polysiloxane in the presence of an active filler and inert filler in the pyrolysis temperature lower than the usually adopted for this technique, with greater strength. It also investigates the influence of pyrolysis temperature, the content of Alas active filler, the presence of infiltrating agents (Al, glass and polymer) after pyrolysis, temperature and infiltration time on some physical and mechanical properties. Alumina is used as inert filler and Al and Ti as active filler in the pyrolysis. Aluminum, glass and polysiloxane are used as agents infiltrating the post-pyrolysis. The results are analyzed with respect to porosity and bulk density by the Archimedes method, the presence of crystalline phases by X-ray diffraction (XRD) and microstructure by scanning electron microscopy (SEM). The ceramic pyrolyzed between 850 °C 1400 °C contain porosity 15% to 33%, density 2.34 g/cm3 and flexural strength at 4 points from 30 to 42 MPa. The microstructure features are porous, with an array of Al2O3 reinforced by TiC particles and AlTi3. The infiltration post-pyrolysis reveals decrease in porosity and increase density and strength. The composites have potential applications where thermal stability is the main requirement

Utilização do éster de soja como biolubrificante

The lubricants found in the market are of mineral or synthetic origin and harm to humans and the environment, mainly due to their improper discard. Therefore industries are seeking to develop products that cause less environmental impact, so to decrease mainly, operator aggression the Cutting Fluids became an emulsion of oil / water or water / oil. However, the emulsion was not considered the most suitable solution for environmental question, therefore the search for biodegradable lubricants and which no are toxic continues and so vegetable oils are seen, again, as a basis for the production of lubricants. The biggest problem with these oils is their oxidative instability that is intensified when working at high temperatures. The process transesterification decreases the oxidation, however changes some physical and chemical properties. Therefore soybean oil after the transesterification process was subjected to tests of density, dynamic viscosity, kinematic viscosity which is calculated from two parameters mentioned, flash point and acidity. Besides the physico-chemical test the soybean oil was subjected to a dynamic test in a tribometer adapted from a table vise, whose induced wear was the adhesive and ultimately was used as cutting fluid in a process of turning in two different materials, steel 1045 and cast iron. This latter test presented results below the mineral cutting fluid which it was compared in all tests, already in other experiments the result was satisfactory and other experiments not, so that chemical additives can be added to the oil analyzed to try equate all parameters and so formulate a biolubrificante not toxic to apply in machining processes of metalworking industry

Possíveis efeitos alelopaticos de Brachiaria decumbens sobre o crescimento inicial de limão cravo (Citrus limonia)

Foram estudados os possíveis efeitos alelopáticos da incorporação da matéria seca da parte aérea de Brachiaria decumbens, ao substrato, nas concentrações de 0, 1,5 e 3,0% (p/p) sobre o crescimento inicial de limão cravo (Citrus limonia Osbeck), em casa-de-vegetação. Foram determinados os parâmetros biométrico s e algumas propriedades físico-químicas da solução do solo. A maior quantidade de matéria seca incorporada causou redução de 44, 42, 57 e 55% das médias da altura, teor de clorofila, área foliar e acúmulo de matéria seca total, respectivamente. O potencial osmótico, pH, condutividade elétrica e os teores de nutrientes da solução do solo foram alterados. Provavelmente, a redução do crescimento observada seja devida a deficiência de N causada por alterações na dinâmica do N-solo em função da incorporação de B. decumbens.