Comportamiento térmico y mecánico del yeso con adiciones de aerogel de sílice granulado

La presente tesis doctoral aborda el estudio de un nuevo material mineral, compuesto principalmente por una matriz de yeso (proveniente de un conglomerante industrial basado en sulfato de calcio multifase) y partículas de aerogel de sílice hidrófugo mesoporoso, compatibilizadas mediante un surfactante polimérico, debido a su alto carácter hidrófugo. La investigación se centra en conocer los factores que influyen en las propiedades mecánicas y conductividad térmica del material compuesto generado. Este estudio pretende contribuir al conocimiento sobre el desarrollo de nuevos morteros de elevado aislamiento térmico que puedan ser utilizados en la rehabilitación energética de edificios de viviendas existentes, debido a que estos representan gran parte del consumo energético del parque de viviendas de España, aunque también a nivel internacional. De los materiales utilizados para desarrollar los morteros estudiados, el yeso, además de ser un material muy abundante, especialmente en España, requiere una menor cantidad de energía para la fabricación de un conglomerante (debido a una menor temperatura de fabricación), en comparación con el cemento o la cal, por lo que presenta una menor huella de carbono que estos últimos. Por otro lado, el aerogel de sílice hidrófugo mesoporoso es, de acuerdo con la documentación disponible, el material que posee actualmente la mayor capacidad de aislamiento térmico en el mercado. El desarrollo de nuevos morteros minerales con una capacidad de aislamiento térmico mayor que los materiales aislantes utilizados tradicionalmente, tiene una aplicación relevante en los casos de rehabilitación energética de edificios históricos y patrimoniales, en los que se requiere la aplicación del aislamiento por el interior de la fachada, ya que este tipo de soluciones tienen el inconveniente de reducir el espacio habitable de las áreas involucradas, especialmente en zonas climáticas en las que el aislamiento térmico puede suponer un espesor considerable, por lo que es ideal utilizar materiales de altas prestaciones de aislamiento térmico capaces de aportar el mismo nivel de aislamiento (o incluso mayor), pero en un espesor considerablemente menor. La investigación se desarrolla en tres etapas: bibliográfica, experimental y de simulación. La primera etapa, parte del estudio de la bibliografía existente, relacionada con materiales aislantes, incluyendo soluciones basadas, tanto en morteros aislantes, como en paneles de aislamiento térmico. La segunda, de carácter experimental, se centra en estudiar la influencia de la microestrucrura y macroestructura, del nuevo material mineral, en las propiedades físicas elementales, mecánicas y conductividad térmica del compuesto. La tercera etapa, mediante una simulación del consumo energético, consiste en cuantificar teóricamente el potencial ahorro energético que puede aportar este material en un caso de rehabilitación energética en particular. La investigación experimental se centró principalmente en conocer los factores principales que influyen en las propiedades mecánicas y conductividad térmica de los materiales compuestos minerales desarrollados en esta tesis. Para ello, se llevó a cabo una caracterización de los materiales de estudio, así como el desarrollo de distintas muestras de ensayo, de tal forma que se pudo estudiar, tanto la hidratación del yeso en los compuestos, como su posterior microestructura y macroestructura, aspectos fundamentales para el entendimiento de las propiedades mecánicas y conductividad térmica del compuesto aislante. De este modo, se pudieron conocer y cuantificar, los factores que influyen en las propiedades estudiadas, aportando una base de conocimiento y entendimiento de este tipo de compuestos minerales con aerogel de sílice hidrófugo, no existiendo estudios publicados hasta el momento de finalización de esta tesis, con la aproximación al material propuesta en este estudio, ni con yeso (basado en sulfato de calcio multifase), ni con otro tipo de conglomerantes. Particularmente, se determinó la influencia que tiene la incorporación de partículas de aerogel de sílice hidrófugo, en grandes proporciones en volumen, en un compuesto mineral basado en distintas fases de sulfato de calcio. No obstante, para llevar a cabo las mezclas, fue necesario utilizar un surfactante para compatibilizar este tipo de partículas, con el conglomerante basado en agua. El uso de este tipo de aditivos tiene una influencia, no solo en el aerogel, sino en las propiedades del compuesto en general, dependiendo de su concentración, por lo que se establecieron dos porcentajes de adición: la primera, determinada a partir de la cantidad mínima necesaria para compatibilizar las mezclas (0,1% del agua de amasado), y la segunda, como límite superior, la concentración utilizada habitualmente a nivel industrial para estabilizar burbujas de aire en hormigones espumados (5%). El surfactante utilizado mostró la capacidad de modificar la superficie del aerogel, cambiando el comportamiento de las partículas frente al agua, permitiendo una invasión parcial de su estructura porosa, por parte del agua de amasado. Este comportamiento supone un aumento muy importante en la relación agua/yeso, afectando el hábito cristalino e influenciando negativamente las propiedades mecánicas de la matriz de yeso, presentando un efecto aún notable a mayor concentración de surfactante (5%). En cuanto a las propiedades finales alcanzadas, fue posible lograr un compuesto mineral ultraligero (200 kg/m3), con alrededor de un 60% de aerogel en volumen y de alta capacidad aislante (0,028 W/m•K), presentando una conductividad térmica notablemente menor que los morteros aislantes del mercado, e incluso también menor que la de los aislantes tradicionales basado en las lanas minerales o EPS; no obstante, con la limitante de presentar bajas propiedades mecánicas, condicionando su posible aplicación futura. Entre los factores principales relacionados con las propiedades mecánicas, se encontró que estas dependen exponencialmente del volumen de yeso en el compuesto; no obstante, factores de segundo orden, como el grado de hidratación, o una mejor distribución del conglomerante entre las partículas de aerogel, debido al aumento de la superficie específica del polvo mineral, pueden aumentar las propiedades mecánicas entre el doble y el triple, dependiendo del volumen de aerogel en cuestión. Además, se encontró que el aerogel, en conjunto con el surfactante, es capaz de introducir una gran cantidad de aire (0,70 m3 por cada m3 de aerogel), que unido al agua evaporada (no consumida por el conglomerante durante la hidratación), el volumen de aire total alcanza, generalmente, un 40%, independientemente de la cantidad de aerogel en la mezcla. De este modo, el aire introducido en la matriz desplaza las proporciones en volumen del aerogel y del yeso, disminuyendo, tanto las propiedades mecánicas, como la capacidad aislante de compuesto mineral. Por otro lado, la conductividad térmica mostró tener una dependencia directa de la contribución de las tres fases principales en el compuesto: yeso, aerogel y aire ocluido. De este modo, se pudo desarrollar un modelo matemático, adaptado de uno existente, capaz de calcular, con bastante precisión, la relación de los tres componentes mencionados, en la conductividad térmica de los compuestos, para el rango de volúmenes y materiales utilizados en esta tesis. Finalmente, la simulación del consumo energético realizada a una vivienda típica de España, de los años 1900 a 1959 (basada en muros de ladrillo macizo), para las zonas climáticas estudiadas (A, D y E), permitió observar el potencial ahorro energético que puede aportar este material, dependiendo de su espesor, como aislamiento interior de los muros de fachada. Particularmente, para la zona A, se determinó un espesor óptimo de 1 cm, mientras que para la zona D y E, 3,5 y 3,9 cm respectivamente. En este sentido, el nuevo material estudiado es capaz de disminuir, entre un 35% y un 80%, el espesor de la capa aislante, en comparación con paneles de lana de roca o los morteros minerales de mayor capacidad aislante del mercado español respectivamente. ABSTRACT The present doctoral thesis studies a new mineral-based composite material, composed by a gypsum matrix (based on an industrial multiphase gypsum binder) and mesoporous hydrophobic silica aerogel particles, compatibilized with a polymeric surfactant due to the high hydrophobic character of the insulating particles. This study pretends to contribute to the development of new composite insulating materials that could be used in energy renovation of existing dwellings, in order to reduce their high energy consumption, as they represent a great part of the total energy consumed in Spain, but also internationally. Between the materials used to develop de studied insulating mortars, gypsum, besides being an abundant material, especially in Spain, requires less energy for the manufacture of a mineral binder (due to lower manufacturing temperatures), compared to lime or cement, thus presenting lower carbon footprint. In other hand, the hydrophobic mesoporous silica aerogel, is, according to the existing references, the material with the highest know insulating capacity in the market. The development of new mineral mortars with higher thermal insulation capacity than traditional insulating materials, presents a relevant application in energy retrofitting of historic and cultural heritage buildings, in which implies that the insulating material should be installed as an internal layer, rather than as an external insulating system. This type of solution involves a reduced internal useful area, especially in climatic zones where the demand for thermal insulation is higher, and so the insulating layer thickness, being idealistic to use materials with very high insulating properties, in order to reach same insulating level (or higher), but in lower thickness than the provided by traditional insulating materials. This research is developed in three main stages: bibliographic, experimental and simulation. The first stage starts by studying the existing references regarding thermally insulating materials, including existing insulating mortars and insulating panels. The second stage, mainly experimental, is centered in the study of the the influence of the microstructure and macrostructure in the physical and mechanical properties, and also in the thermal conductivity of the new mineral-based material. The thirds stage, through energy simulation, consists in theoretically quantifying the energy savings potential that can provide this type of insulating material, in a particular energy retrofitting case study. The experimental research is mainly focused in the study of the factors that influence the mechanical properties and the thermal conductivity of the thermal insulating mineral composites developed in this thesis. For this, the characterization of the studied materials has been performed, as well as the development of several experimental samples, in order to study the hydration of the mineral binder within the composites, but also the final microstructure and macrostructure, fundamental aspects for the understanding of the composite’s mechanical and insulating properties. Thus, is was possible to determine and quantify the factors that influence the studied material properties, providing a knowledge base and understanding of mineral composites that comprises mesoporous hydrophobic silica aerogel particles, being the first study up to date regarding the specific approach of the present study, regarding not just multiphase calcium sulfate plaster, but also other mineral binders. Particularly, the influence of the incorporation of hydrophobic silica aerogel particles, in high volume ratios into a mineral compound, based on different phases of calcium sulfate has been determined. However, to perform mixing, it is necessary to use a surfactant in order to compatibilize these particles with the water-based mineral binder. The use of such additives has an influence, not only in the aerogel, but the overall properties of the compound, so two different surfactant concentration has been studied: the first, the minimum amount of surfactant (used in this thesis) in order to develop the slurries (0.1% concentration of the mixing water), and the second, as the upper limit, the concentration usually used industrially to stabilize air bubbles in foamed concrete (5%). One of the side effects of using such additive, was the modification of the aerogel particles, by changing their behavior in respect to water, generating a partial invasion of the aerogel’s porous structure, by the mixing water. This behavior produces a very important increase in water/binder ratios, affecting the crystal habit and negatively influencing the mechanical properties of the gypsum matrix. This effect further increased when a higher concentration of surfactant (5%) is used. Regarding final materials properties, it was possible to achieve an ultra-lightweight mineral composite (200 kg/m3), with around 60% by volume of aerogel, presenting a very high insulating capacity (0.028 W/m•K), a noticeable lower thermal conductivity compared to the insulating mortars and traditional thermal insulating panels on the market, such as mineral wool or EPS; however, the limiting factor for future’s material application in buildings, is related to the very low mechanical properties achieved. Among the main factors related to the mechanical properties, it has been found an exponential correlation to the volume of gypsum in the composite. However, second-order factors such as the degree of hydration, or a better distribution of the binder between the aerogel particles, due to the increased surface area of the mineral powder, can increase the mechanical properties between two to three times, depending aerogel volume involved. In addition, it was found that the aerogel, together with the surfactant, is able to entrain a large amount of air volume (around 0.70 m3 per m3 of aerogel), which together with the evaporated water (not consumed by the binder during hydration), can reach generally around 40% of entrained air within the gypsum matrix, regardless of the amount of aerogel in the mixture. Thus, the entrained air into the matrix displaces the volume proportions of the aerogel and gypsum, reducing both mechanical and insulating properties of the mineral composite. On the other hand, it has been observed a direct contribution of three main phases into the thermal conductivity of the composite: gypsum, aerogel and entrained air. Thus, it was possible to develop a mathematical model (adapted from an existing one), capable of calculating quite accurate the thermal conductivity of such mineral composites, from the ratio these three components and for the range of volumes and materials used in this thesis. Finally, the energy simulation performed to a typical Spanish dwelling, from the years 1900 to 1959 (mainly constructed with massive clay bricks), within three climatic zones of Spain (A, D and E), showed the energy savings potential that can provide this type of insulating material, depending on the thickness of the applied layer. Particularly, for the climatic A zone, it has been found an optimal layer thickness of 1 cm, while for zone D and E, 3.5 and 3.9 cm respectively. In this manner, the new studied materials is capable of decreasing the thickness of the insulating layer by 35% and 80%, compared with rock wool panels or mineral mortars with the highest insulating performance of the Spanish market respectively.

RNA polymerase sigma factor determines start-site selection but is not required for upstream promoter element activation on heteroduplex (bubble) templates

Sequence-selective transcription by bacterial RNA polymerase (RNAP) requires σ factor that participates in both promoter recognition and DNA melting. RNAP lacking σ (core enzyme) will initiate RNA synthesis from duplex ends, nicks, gaps, and single-stranded regions. We have used DNA templates containing short regions of heteroduplex (bubbles) to compare initiation in the presence and absence of various σ factors. Using bubble templates containing the σD-dependent flagellin promoter, with or without its associated upstream promoter (UP) element, we demonstrate that UP element stimulation occurs efficiently even in the absence of σ. This supports a model in which the UP element acts primarily through the α subunit of core enzyme to increase the initial association of RNAP with the promoter. Core and holoenzyme do differ substantially in the template positions chosen for initiation: σD restricts initiation to sites 8–9 nucleotides downstream of the conserved −10 element. Remarkably, σA also has a dramatic effect on start-site selection even though the σA holoenzyme is inactive on the corresponding homoduplexes. The start sites chosen by the σA holoenzyme are located 8 nucleotides downstream of sequences on the nontemplate strand that resemble the conserved −10 hexamer recognized by σA. Thus, σA appears to recognize the −10 region even in a single-stranded state. We propose that in addition to its described roles in promoter recognition and start-site melting, σ also localizes the transcription start site.

Homologous pairing in stretched supercoiled DNA

By using elastic measurements on single DNA molecules, we show that stretching a negatively supercoiled DNA activates homologous pairing in physiological conditions. These experiments indicate that a stretched unwound DNA locally denatures to alleviate the force-driven increase in torsional stress. This is detected by hybridization with 1 kb of homologous single-stranded DNA probes. The stretching force involved (≈2 pN) is small compared with those typically developed by molecular motors, suggesting that this process may be relevant to DNA processing in vivo. We used this technique to monitor the progressive denaturation of DNA as it is unwound and found that distinct, stable denaturation bubbles formed, beginning in A+T-rich regions.

Capabilities of liposomes for topological transformation

Dynamic behaviors of liposomes caused by interactions between liposomal membranes and surfactant were studied by direct real-time observation by using high-intensity dark-field microscopy. Solubilization of liposomes by surfactants is thought to be a catastrophic event akin to the explosion of soap bubbles in the air; however, the actual process has not been clarified. We studied this process experimentally and found that liposomes exposed to various surfactants exhibited unusual behavior, namely continuous shrinkage accompanied by intermittent quakes, release of encapsulated liposomes, opening up, and inside–out topological inversion.

Altered stability of pulmonary surfactant in SP-C-deficient mice

The surfactant protein C (SP-C) gene encodes an extremely hydrophobic, 4-kDa peptide produced by alveolar epithelial cells in the lung. To discern the role of SP-C in lung function, SP-C-deficient (−/−) mice were produced. The SP-C (−/−) mice were viable at birth and grew normally to adulthood without apparent pulmonary abnormalities. SP-C mRNA was not detected in the lungs of SP-C (−/−) mice, nor was mature SP-C protein detected by Western blot of alveolar lavage from SP-C (−/−) mice. The levels of the other surfactant proteins (A, B, D) in alveolar lavage were comparable to those in wild-type mice. Surfactant pool sizes, surfactant synthesis, and lung morphology were similar in SP-C (−/−) and SP-C (+/+) mice. Lamellar bodies were present in SP-C (−/−) type II cells, and tubular myelin was present in the alveolar lumen. Lung mechanics studies demonstrated abnormalities in lung hysteresivity (a term used to reflect the mechanical coupling between energy dissipative forces and tissue-elastic properties) at low, positive-end, expiratory pressures. The stability of captive bubbles with surfactant from the SP-C (−/−) mice was decreased significantly, indicating that SP-C plays a role in the stabilization of surfactant at low lung volumes, a condition that may accompany respiratory distress syndrome in infants and adults.

Considerations of transcriptional control mechanisms: Do TFIID–core promoter complexes recapitulate nucleosome-like functions?

The general transcription initiation factor TFIID was originally identified, purified, and characterized with a biochemical assay in which accurate transcription initiation is reconstituted with multiple, chromatographically separable activities. Biochemical analyses have demonstrated that TFIID is a multiprotein complex that directs preinitiation complex assembly on both TATA box-containing and TATA-less promoters, and some TFIID subunits have been shown to be molecular targets for activation domains in DNA-binding regulatory proteins. These findings have most commonly been interpreted to support the view that transcriptional activation by upstream factors is the result of enhanced TFIID recruitment to the core promoter. Recent insights into the architecture and cell-cycle regulation of the multiprotein TFIID complex prompt both a reassessment of the functional role of TFIID in gene activation and a review of some of the less well-appreciated literature on TFIID. We present a speculative model for diverse functional roles of TFIID in the cell, explore the merits of the model in the context of published data, and suggest experimental approaches to resolve unanswered questions. Finally, we point out how the proposed functional roles of TFIID in eukaryotic class II transcription fit into a model for promoter recognition and activation that applies to both eubacteria and eukaryotes.

Bacteria are different: Observations, interpretations, speculations, and opinions about the mechanisms of adaptive evolution in prokaryotes

To some extent, the genetic theory of adaptive evolution in bacteria is a simple extension of that developed for sexually reproducing eukaryotes. In other, fundamental ways, the process of adaptive evolution in bacteria is quantitatively and qualitatively different from that of organisms for which recombination is an integral part of the reproduction process. In this speculative and opinionated discussion, we explore these differences. In particular, we consider (i) how, as a consequence of the low rates of recombination, “ordinary” chromosomal gene evolution in bacteria is different from that in organisms where recombination is frequent and (ii) the fundamental role of the horizontal transmission of genes and accessory genetic elements as sources of variation in bacteria. We conclude with speculations about the evolution of accessory elements and their role in the adaptive evolution of bacteria.

Meiosis: how could it work?

A physical connection between homologs is required for reductional segregation at the first division of meiosis. This connection is usually provided by one or a few well-spaced crossovers. A speculative overview of processes leading to formation of these crossovers is presented.

A loop-loop "kissing" complex is the essential part of the dimer linkage of genomic HIV-1 RNA.

RNA-RNA interactions govern a number of biological processes. Several RNAs, including natural sense and antisense RNAs, interact by means of a two-step mechanism: recognition is mediated by a loop-loop complex, which is then stabilized by formation of an extended intermolecular duplex. It was proposed that the same mechanism holds for dimerization of the genomic RNA of human immunodeficiency virus type 1 (HIV-1), an event thought to control crucial steps of HIV-1 replication. However, whereas interaction between the partially self-complementary loop of the dimerization initiation site (DIS) of each monomer is well established, formation of the extended duplex remained speculative. Here we first show that in vitro dimerization of HIV-1 RNA is a specific process, not resulting from simple annealing of denatured molecules. Next we used mutants of the DIS to test the formation of the extended duplex. Four pairs of transcomplementary mutants were designed in such a way that all pairs can form the loop-loop "kissing" complex, but only two of them can potentially form the extended duplex. All pairs of mutants form heterodimers whose thermal stability, dissociation constant, and dynamics were analyzed. Taken together, our results indicate that, in contrast with the interactions between natural sense and antisense RNAs, no extended duplex is formed during dimerization of HIV-1 RNA. We also showed that 55-mer sense RNAs containing the DIS are able to interfere with the preformed HIV-1 RNA dimer.

Rotation of subunits during catalysis by Escherichia coli F1-ATPase.

During oxidative and photo-phosphorylation, F0F1-ATP synthases couple the movement of protons down an electrochemical gradient to the synthesis of ATP. One proposed mechanistic feature that has remained speculative is that this coupling process requires the rotation of subunits within F0F1. Guided by a recent, high-resolution structure for bovine F1 [Abrahams, J. P., Leslie, A. G., Lutter, R. & Walker, J. E. (1994) Nature (London) 370, 621-628], we have developed a critical test for rotation of the central gamma subunit relative to the three catalytic beta subunits in soluble F1 from Escherichia coli. In the bovine F1 structure, a specific point of contact between the gamma subunit and one of the three catalytic beta subunits includes positioning of the homolog of E. coli gamma-subunit C87 (gamma C87) close to the beta-subunit 380DELSEED386 sequence. A beta D380C mutation allowed us to induce formation of a specific disulfide bond between beta and gamma C87 in soluble E. coli F1. Formation of the crosslink inactivated beta D380C-F1, and reduction restored full activity. Using a dissociation/reassembly approach with crosslinked beta D380C-F1, we incorporated radiolabeled beta subunits into the two noncrosslinked beta-subunit positions of F1. After reduction of the initial nonradioactive beta-gamma crosslink, only exposure to conditions for catalytic turnover results in similar reactivities of unlabeled and radiolabeled beta subunits with gamma C87 upon reoxidation. The results demonstrate that gamma subunit rotates relative to the beta subunits during catalysis.

Medidas de dispersão de gás em células mecânicas industriais e seus condicionantes.

A qualidade da dispersão de gás em células de flotação é comumente caracterizada através de parâmetros como velocidade superficial do gás (Jg), hold-up do gás (?g), distribuição de tamanho de bolha (db ou D3,2) e fluxo de superfície de bolha (Sb). Sendo um processo de separação de minerais que é dependente da interação (colisão + adesão) entre partículas hidrofóbicas e bolhas de ar, a flotação tem seu desempenho dependente de uma dispersão de gás apropriada na polpa de minério. Desta forma, este trabalho objetivou caracterizar o estado da dispersão de gás de duas células em um banco composto por quatro células Wemco de 42,5 m³ (subaeradas), operando em série na usina da Vale Fertilizantes (Cajati-SP). Realizaram-se três campanhas de medidas que foram conduzidas sob diferentes condições operacionais: a) Diâmetro do rotor (D) de 1,09 m e rotação (N) entre 145 RPM e 175 RPM; b) D = 0,99 m e N entre 110 RPM e 190 RPM; c) D = 0,99 m e N de 120 RPM e de 130 RPM. Observaram-se os seguintes valores de dispersão de gás: 0,7 <= Jg <= 5,4 cm/s, 7 <= ?g <= 15%, 1,6 <= D3,2 <= 2,4 mm e Sb na faixa de 24 a 162 s-1. A magnitude de Jg medida na 1ª e 2ª campanhas mostrou-se acima dos valores reportados pela literatura, indicando necessidade de modificação de condições operacionais dos equipamentos, assim como cuidadosa manutenção. Posteriormente, a 3ª campanha indicou maior conformidade dos parâmetros de dispersão de gás em relação à literatura, constatando-se uma considerável melhora de desempenho do processo de flotação.

Efeitos do treinamento de força no músculo esquelético em ratos com caquexia induzida pelo câncer

A ausência de terapias eficazes para a caquexia permanece como um problema central para o tratamento do câncer no mundo. Em contrapartida, o treinamento de força (i.e. também conhecido como treinamento resistido) tem sido amplamente utilizado como uma estratégia não farmacológica anticatabólica, prevenindo a perda da massa e da função da musculatura esquelética. Entretanto, o papel terapêutico do treinamento de força na caquexia do câncer permanece apenas especulativo. Portanto, nesse estudo avaliamos se o treinamento de força poderia atenuar a perda da massa e da função da musculatura esquelética em um severo modelo de caquexia do câncer em ratos. Para isso, ratos machos da linhagem Wistar foram randomizados em quatro grupos experimentais: 1) ratos sedentários injetados com solução salina na medula óssea (Controle); 2) ratos injetados com solução salina na medula óssea e submetidos ao treinamento de força (Controle + T); 3) ratos sedentários injetados com células do tumor Walker 256 na medula óssea (Tumor); e 4) ratos injetados com células do tumor Walker 256 na medula óssea e submetidos ao treinamento de força (Tumor + T). Foram avaliados a massa e a área de secção transversa da musculatura esquelética, marcadores de disfunção metabólica e do turnover proteico, a função da musculatura esquelética in vivo e ex vivo, o consumo alimentar, o crescimento tumoral e a sobrevida dos grupos experimentais com tumor. O grupo Tumor apresentou atrofia muscular após quinze dias da injeção das células tumorais como pode ser observado pela redução na massa dos músculos Plantaris (- 20,5%) e EDL (-20%). A atrofia no músculo EDL foi confirmada por análises histológicas, demonstrando uma redução de 43,8% na área de secção transversa. Embora o treinamento de força tenha aumentado o conteúdo proteico da lactato desidrogenase e revertido totalmente o conteúdo da forma fosforilada de 4EBP-1 (i.e. repressor da transcrição de mRNA), ele não atuou na morfologia da musculatura esquelética nos animais com tumor. Além disso, o treinamento de força não atenuou a perda de função da musculatura esquelética, a anorexia, o crescimento tumoral ou a taxa de mortalidade. Contudo, a força muscular, avaliada pelo teste de 1RM, apresentou uma correlação negativa com a sobrevida dos animais (p = 0,02), sugerindo que a perda de força prediz a mortalidade nesse modelo experimental de caquexia do câncer. Em suma, a injeção de células do tumor Walker 256 na medula óssea induz caquexia do câncer em ratos. O treinamento de força não foi eficaz em atenuar a perda de massa e função da musculatura esquelética nesse modelo. Entretanto, a força muscular prediz a sobrevida dos animais, sugerindo que novos estudos são necessários para elucidar o possível efeito terapêutico do treinamento de força para atenuar a caquexia do câncer e a progressão tumoral

Avaliação da influência do efeito de ultrassom na lixiviação de metais de placas de circuito impresso obsoletas.

Os equipamentos elétricos e eletrônicos (EEE) possuem uma grande importância na sociedade contemporânea, e estão presentes no cotidiano das pessoas de forma ubíqua. Com o aumento no consumo de EEE juntamente com a obsolescência precoce, surge um novo tipo de resíduo, chamado de Resíduos de Equipamentos Elétricos e Eletrônicos (REEE). Os REEE não devem ser descartados em aterros, pelo risco de contaminação e pelo desperdício de material. Assim, a reciclagem se faz necessária. As placas de circuito impresso (PCI) estão presentes na grande maioria do REEE e contem a maior variedade de metais, incluindo metais valiosos como Au, Ag, Pt e Cu. A complexidade torna a reciclagem destas placas muito difícil. Rotas hidrometalúrgicas tem surgido como uma alternativa mais limpa para o tratamento de PCI, em detrimento aos processos pirometalúrgicos. Nas rotas hidrometalúrgicas, os metais são extraídos pela lixiviação realizada por ácidos ou bases. O efeito ultrassônico tem sido empregado na síntese de novas substâncias e também em alguns casos no tratamento de resíduos. O processo central no uso de ultrassom é a cavitação acústica, capaz de produzir microbolhas na solução com temperatura da ordem de 5000 K e pressão de 500 atm localmente. Além disto, a implosão das bolhas de cavitação em meio heterogêneo causa um jato de solução na superfície, que pode alcançar velocidade de 100 m.s-1. Assim, esta tese tem como objetivo a investigação do efeito do ultrassom sobre PCI obsoletas. Dois efeitos foram investigados: o efeito da cominuição das PCI promovido pela cavitação e a influência da cavitação na lixiviação com ácido sulfúrico de Fe, Al e Ni. Os parâmetros investigados na cominuição foram: tipo de placa, granulometria da placa moída e potência de ultrassom. Os parâmetros de lixiviação avaliados foram: razão sólido-líquido (S/L), concentração de ácido e potência de ultrassom. Também foram realizados ensaios de lixiviação sonicados com meio oxidante. Foi feita a análise cinética para se determinar qual é o controle da reação de lixiviação.

Plastisol foaming process. Decomposition of the foaming agent, polymer behavior in the corresponding temperature range and resulting foam properties

The decomposition of azodicarbonamide, used as foaming agent in PVC—plasticizer (1/1) plastisols was studied by DSC. Nineteen different plasticizers, all belonging to the ester family, two being polymeric (polyadipates), were compared. The temperature of maximum decomposition rate (in anisothermal regime at 5 K min−1 scanning rate), ranges between 434 and 452 K. The heat of decomposition ranges between 8.7 and 12.5 J g−1. Some trends of variation of these parameters appear significant and are discussed in terms of solvent (matrix) and viscosity effects on the decomposition reactions. The shear modulus at 1 Hz frequency was determined at the temperature of maximum rate of foaming agent decomposition, and differs significantly from a sample to another. The foam density was determined at ambient temperature and the volume fraction of bubbles was used as criterion to judge the efficiency of the foaming process. The results reveal the existence of an optimal shear modulus of the order of 2 kPa that corresponds roughly to plasticizer molar masses of the order of 450 ± 50 g mol−1. Heavier plasticizers, especially polymeric ones are too difficult to deform. Lighter plasticizers such as diethyl phthalate (DEP) deform too easily and presumably facilitate bubble collapse.

Targetless image-based method for measuring displacements and strains on concrete surfaces with a consumer camera

Measurement of concrete strain through non-invasive methods is of great importance in civil engineering and structural analysis. Traditional methods use laser speckle and high quality cameras that may result too expensive for many applications. Here we present a method for measuring concrete deformations with a standard reflex camera and image processing for tracking objects in the concretes surface. Two different approaches are presented here. In the first one, on-purpose objects are drawn on the surface, while on the second one we track small defects on the surface due to air bubbles in the hardening process. The method has been tested on a concrete sample under several loading/unloading cycles. A stop-motion sequence of the process has been captured and analyzed. Results have been successfully compared with the values given by a strain gauge. Accuracy of our methods in tracking objects is below 8 μm, in the order of more expensive commercial devices.