Este trabalho comparou as propriedades termomecânicas de concretos refratários comerciais para aplicação em conjunto de porta ventos de alto-forno. Dez composições diferentes de concretos refratários à base de alta alumina, alta mulita e alta andaluzita foram caracterizados. Para identificar e quantificar a composição e a microestrutura dos refratários foram utilizadas técnicas de espectroscopia de fluorescência de raios X (FRX), difratometria de raios X (DRX) qualitativa e quantitativa, microscopia eletrônica de varredura com análise de energia dispersiva de raios X (MEV-EDS), massa especifica aparente e porosidade aparente (MEA/Pa). A caracterização termomecânica foi realizada com ensaios de flexão três pontos, propagação de trinca para cálculo da energia de fratura com entalhe chevron, módulo de elasticidade dinâmico, coeficiente de Poisson e o cálculo do coeficiente de expansão térmica utilizando a regra das misturas. Para compreender o dano causado pelo choque térmico ensaios cíclicos de choque térmico foram feitos seguidos de analises de módulo de elasticidade por técnica de excitação por impulso seguido do módulo de ruptura por flexão três-pontos. Os parâmetros de resistência ao choque térmico (R e R´) e os parâmetros de resistência ao dano por choque térmico (R´´´, R´´´´ e Rst) foram calculados. Os resultados de ciclagem térmica e os parâmetros de resistência ao choque térmico mostram que para os concretos analisados, todos os materiais tem nucleação de trincas para temperaturas iguais ou superiores a 1100°C. Os parâmetros de resistência ao dano por choque térmico corroboram com os resultados das análises de MEV. O concreto D1 apresentou a melhor combinação de resistência ao dano por choque térmico e baixa condutividade térmica, propriedades requeridas para a aplicação em conjunto de porta ventos de alto-forno. Por fim é mostrado que as análises de ciclagem térmica devem ser analisadas cuidadosamente com foco na aplicação dos concretos e no desempenho da microestrutura do material, visto que as propriedades termomecânicas são caracterizadas por indiretamente por diferentes técnicas e portanto vários parâmetros precisam ser considerados. O concreto D1 apresentou boa resistência ao dano por choque térmico e baixa condutividade térmica e portanto possui o melhor desempenho para a aplicação em conjunto de porta ventos. / This work compares the thermomechanical properties of commercial castable refractories for blast furnace blowpipe application. Ten different compositions of commercial castable refractories with compositions of high alumina, high mullite, and high andalusite were characterized. In order to identify and quantify the composition and microstructure of the castables, X-ray fluorescence (XRF), X-ray diffraction (XRD), scanning eléctron microscopy with energy dispersive spectrum (SEM-EDS), bulk density, and apparent porosity were used. The thermomechanical characterization was performed through threepoint flexural strength, work of fracture through crack propagation in notched samples, dynamic elasticity modulus, Poisson ratio, and the calculation of the thermal expansion coefficient using the mix law. Cyclic thermal shocks at 1100°C were realized in order to characterize the materials under thermal shock damage environment followed by elasticity modulus, modulus of rupture, and SEM analysis. The parameters for thermal shock resistance (R e R´) and the parameters for thermal shock damage resistance (R´´´, R´´´´ e Rst) were calculated. The thermal shock cycling tests and the thermal shock resistance correlated and showed that all castables had crack nucleation after a thermal shock of 1100°C or higher. The thermal shock damage parameters and the SEM analysis correlate. Castable D1 showed high resistance to thermal shock damage and lower thermal conductivity, which are required properties for the blast-furnace blowpipe application. Thermal shock cycling tests performed on castables should therefore be examined not only through mechanical testing, but also through microstructure analysis. Castable D1 showed high thermal shock damage resistance and lower value of thermal conductivity; therefore, it is the best castable for blast furnace blowpipe application among the samples tested.

ABSTRACT A theoretical and experimental study of the vibrational and chemical relaxation rates of diatomic gases, in flows behind shock waves and along nozzles,is made here. ¶ The validity of the conventional relaxation rate models, which are generally used to analyse experiments, is tested by developing a detailed microscopic description of the diatomic relaxation processes. Assuming the diatomic molecules to be represented by the anharmonic Morse Oscillator, the vibrational Master equation, which describes the time variation of each vibrational energy level population, is constructed by allowing one-quantum vibration to translation (V-T) energy exchanges and vibration to vibration (V-V) energy exchanges between the molecules. Dissociation and recombination are allowed to occur from, and to, the uppermost vibrational level. Solving the Master equation, it is found that a number of effects are explained by the inclusion of V-V transitions. In particular it is found that V-V energy exchanges cause the induction time for H2 dissociation to be increased; suggest that the linear rate law, for H2 and Ar mixtures, fails for a H2 mole fraction above 20%; give an acceleration of vibrational excitation as equilibrium is approached for H2 and N2; cause the vibrational temperature to be lower than the value found without V-V transitions for vibrational de-excitation in nozzle flows of H2 and N2, and conversely for recombination of H2 in nozzle flows. The most important result is the demonstration that conventional nozzle flow calculations, with shock-tube-determined dis-sociation and vibrational excitation rates, appear to be valid for the recombining and vibrationally de-excitating flows considered. ¶ The dissociation rates of undiluted nitrogen are measured in the free-piston shock tube DDT, using time-resolved optical interferometry, over a temperature range of 6000-14000K and confirm the strong temperature dependence of the pre-exponential factor observed by Hanson and Baganoff (1972). ¶ The vibrational de-excitation and excitation rates are determined in the small free-piston shock tunnel T2 over temperature ranges of 2000-4000K and 7000-10300K, respectively, by measuring the shock angles and curvatures, from optical interferograms, of flow over an inclined flat plate in the nonequilibrium nozzle flow. The de-excitation rate is found to be within a factor of ten of the excitation rate, while the excitation rate of N2 by collision with N is found to be less than about 50 times the excitation rate of N2 by N2. The dissociation rates of nitrogen, in the flow behind a shock attached to a wedge, are investigated in the large free-piston shock tunnel, using the shock curvature technique. The discrepancy, reported by Kewley and Hornung (1974b), between theory and experiment at the highest enthalpy is found to be resolved by including the measured helium contamination (Crane 1975) in the free-stream. Reasonable agreement is obtained between experimental shock curvatures and calculations using accepted dissociation rates.

This dissertation has investigated the impact of the acculturation and repatriation processes and the language experiences of French academic sojourners on their perceptions of cultural identity. This dissertation was based on three substantive themes: culture shock, reverse culture shock and cultural identity issues.

The main objective of this study was to investigate promoter sequences of putative HSR genes for the presence of unique regulatory elements and modules that might be involved in the regulation of HSR. In order to achieve this objective, an in silico promoter analysis strategy was devised, which focused on the identification of promoter sequences and regulatory elements, and modelling of promoter modules by using Genomatix software tools such as MatInspector and ModelInspector. Results showed that two modules (EGRF_SP1F_01 and SP1F_CEBP_01) were conserved in the promoter sequences of three well-known Hsp-genes (Hsp90, Hsp105β and αβ-crystallin). Screening the 60 target gene promoters for the presence of the two modules revealed that 12 genes (20 %) contained both modules. These included Moesin, Proline-4 hydroxylase, Poly(A) binding protein and Formin-binding protein. None of these genes had been previously associated with heat shock response.

Malaria is caused by a protozoan parasite belonging to the genus Plasmodia. Plasmodium falciparum is responsible for the fatal form of human malaria. Spread of drug resistant parasites warrants for sound biological understanding of the parasite at both cellular and biochemical level. Heat shock proteins are highly conserved group of proteins required for correct folding, transport, and degradation of substrate proteins in vivo. Hsp60 is found in eubacteria, mitochondria, and chloroplasts, where in cooperation with Hsp10, it participates in protein folding. Keeping in mind the central importance of chaperones in biological processes, our lab has been interested in examining roles of heat shock proteins in malarial parasite during its asexual growth in human erythrocytes. During its life cycle, the parasite continually shuttles between a cold-blooded insect vector with the body temperature of 27°C and a warm-blooded human host with the body temperature of 37°C and parasite experiences episodes of heat shock periodically. Therefore malaria parasite serves as good model to study heat shock protein functions. Like all biological systems, the malaria parasite expresses several chaperones including proteins of the Hsp40, Hsp60, Hsp70, Hsp90 and Hsp100 families. Towards this we have systematically characterized different families of stress proteins Hsp40, Hsp60, Hsp70, Hsp90 as well as Hsp100. In addition to cloning their genes we have studied their expression, localization, abundance, complexes and their biological roles. Earlier studies from our lab showed PfHsp90 is essential for parasite growth and survival in human erythrocytes. Our present study attempts to study heat shock protein 60 of the malarial parasite (PfHsp60). In this connection we have been successful to clone and express PfHsp60 gene from Plasmodium falciparum in E. coli and to raise antibodies specific to PfHsp60. We have examined its expression and import in the mitochondrion of malarial parasite during its asexual growth in human erythrocytes. Analysis of the total parasite lysates resolved by two-dimensional gel electrophoresis followed by western blotting using specific antibodies showed PfHsp60 exhibits an isoelectric point corresponding to its signal uncleaved precursor (pI - 6.2). Mass spectrometric analysis of the spot corresponding to precursor PfHsp60 confirmed the presence of signal peptide region. Co-immunoprecipitation analysis of total parasite lysates with antibodies specific to PfHsp60 showed precursor PfHsp60 to be associated with PfHsp70 and PfHsp90. Co-immunoprecipitation from the mitochondrial and cytoplasmic fraction confirmed the position of mature PfHsp60. Indirect immunofluorescence analysis also showed presence of a pool of PfHsp60 in the cytoplasm of the parasite, in addition to its expected localization in the mitochondrion. Treatment of parasite infected erythrocytes with an inhibitor of Hsp90 disrupted its association with cytoplasmic chaperones and targeted precursor Pfhsp60 for intracellular degradation. On the other hand treatment with the mitochondrial import inhibitor further inhibited the import of precursor PfHsp60 into the mitochondrion and stabilized its interaction with cytosolic chaperones. Previous reports have shown that there are four fold accumulations of PfHsp60 transcripts in heat shocked parasites. However, the expression of PfHsp60 was not induced upon heat shock in the blood stages of P.falciparum. Biochemical data indicate that the mitochondrion is not the source of ATP in the parasite. Furthermore the genome does not seem to encode the critical subunits of Fo-F1 ATP synthase. Yet, the active mitochondrial electron transport chain serves for regeneration of ubiquinone required for pyrimidine biosynthesis. The active electron transport chain is critical for parasite survival. Recent study with the lab-grown 3D7 strain of malaria parasite concluded that mitochondria are not required for energy conversion. Transcriptome analysis of the parasite derived directly from blood samples of infected patients showed that genes encoding the proteins of mitochondrial biogenesis, oxidative phosphorylation, respiration and highlighted the mean expression level for PfHsp60 is dramatically up regulated in parasites. Gene up regulation doesn’t always translate to increase in protein function or metabolic up regulation. When we analyzed the total parasite lysates of field isolates resolved by two-dimensional gel electrophoresis also showed presence of the precursor form of Pfhsp60 in the cytoplasm of the parasite. Overall, our observations indicated accumulation of precursor PfHsp60 in the parasite cytoplasm suggesting an inefficient mitochondrial protein import in the malarial parasite. The defect in mitochondrial protein import is possibly reflective of the compromised energy state of the parasite mitochondrion. This fits with the model that has been reported in mutant strains of yeast, Saccharomyces cerevisiae lacking functional F o-F1-ATPase. These strains were found to grow very poorly under anaerobic conditions and are known to accumulate Hsp60 protein in the cytoplasm mainly its precursor form. Under optimal growth conditions most eukaryotes maintain close co-ordination between gene expression, translation and translocation efficiently. As a result, mitochondrial precursor proteins are usually not found to accumulate in the cytoplasm. To our knowledge this the first report suggesting an inefficient co-ordination in the synthesis and translocation of precursor PfHsp60 and possibly other proteins during asexual growth of malarial parasite in human erythrocytes under optimal growth conditions. Finally, expression of the PfHsp60 gene in E.coli resulted in its association with bacterial GroEL subunits co-fractionating with a size of 920 kDa, corresponding to the tetra decameric form. The observation indicated possible existence of a hybrid chaperonin complex consisting of subunits from ectopically expressed PfHsp60 and endogenous GroEL.

No description available.

In der vorliegenden Arbeit wird eine Methode vorgestellt, mit welcher die Zuverlässigkeit mikroelektromechanischer Systeme (MEMS) bezüglich stoßinduzierter Fehlermechanismen bereits in der Entwurfsphase neuer Produkte abgeschätzt bzw. verbessert werden kann. Der Ansatz bezieht sich dabei auf bruch- sowie adhäsionsbedingte Ausfallmechanismen und erfordert zwei wesentliche Schritte. Zuerst werden Systemmodelle der jeweils zu untersuchenden mikromechanischen Systeme erstellt, welche die Berechnung der Stoßantwort wie auch der dabei auftretenden Belastungen in Sinne von Auslenkungen, Deformationen und Aufprallkräften ermöglichen. In einem zweiten Schritt wird die zur Fertigung vorgesehene Technologie bezüglich des Auftretens beider stoßbedingter Ausfallmechanismen sowie deren Abhängigkeit von verschiedenen Umgebungsbedingungen oder Betriebsparametern systematisch untersucht. Die aus der Prozesscharakterisierung resultierenden Daten dienen zur Ableitung prozessspezifischer Fehlerkriterien, welche die Einschätzung der zuvor berechneten Lasten ermöglichen. Auf diese Weise kann abgeschätzt werden, inwieweit die Zuverlässigkeit der betrachteten mikromechanischen Strukturen beeinflusst wird bzw. mit welchen Maßnahmen diese gesteigert werden kann.

Shock waves create a unique environment of high pressure, high temperature and high strain-rates. It has been observed that chemical reactions that occur in this regime are exothermic and can lead to the synthesis of new materials that are not possible under other conditions. The exothermic reaction is used in the development of binary energetic materials. These materials are of significant interest to the energetic materials community because of its capability of releasing high heat content during a chemical reaction and the relative insensitivity of these types of energetic materials. Synthesis of these energetic materials, at nano grain sizes with structural reinforcements, provides an opportunity to develop a dual functional material with both strength and energetic characteristics. Shock-induced chemical reactions pose challenges in experiment and instrumentation. This thesis is addressed to the theoretical development of constitutive models of shock-induced chemical reactions in energetic composites, formulated in the framework of non-equilibrium thermodynamics and mixture theories, in a continuum scale. Transition state-based chemical reaction models are introduced and incorporated with the conservation equations that can be used to calculate and simulate the shock-induced reaction process. The energy that should be supplied to reach the transition state has been theoretically modeled by considering both the pore collapse mechanism and the plastic flow with increasing yield stress behind the shock wave. A non-equilibrium thermodynamics framework and the associated evolution equations are introduced to account for time delays that are observed in the experiments of shock-induced or assisted chemical reactions. An appropriate representation of the particle size effects is introduced by modifying the initial energy state of the reactants. Numerical results are presented for shock-induced reactions of mixtures of Al, Fe2O3 and Ni, Al with epoxy as the binder. The theoretical model, in the continuum scale, requires parameters that should be experimentally determined. The experimental characterization has many challenges in measurement and development of nano instrumentation. An alternate approach to determine these parameters is through ab-initio calculations. Thus, this thesis has initiated ab-initio molecular dynamics studies of shock-induced chemical reactions. Specifically, the case of thermal initiation of chemical reactions in aluminum and nickel is considered.

In this thesis, different optomechanical design and adhesive configurations for mounting mirrors and prisms used in a laser system are investigated. Maintaining stability and strength of optical components of a laser device is difficult especially if the system is to be used in military environment. In order to determine the strength of prism mounts to high acceleration levels, mathematical correlations derived by Yoder are used. By use of these mathematical correlations, safety factor of different prism mounts and adhesive configurations are calculated for an acceleration level of 40g. So as to decide most stable mirror mount and adhesive configuration, several experiments are conducted. For the experiments, 5 different optomechanical mounts are designed. Then, 25 mirrors are bonded to the designed mounts with 5 different adhesives. These experiments are done to simulate harsh military environmental conditions such as thermal shock, mechanical vibration and mechanical shock. In the experiments, angular movement of mirrors due to adhesive cure, thermal shock, mechanical vibration and mechanical shock are monitored. Thermal shock is applied between -40&ordm / C and 70&ordm / C with a temperature change of 22&ordm / C/min. On the v other hand, mechanical vibration of 14 grms and mechanical shock of 40g for 6 ms is applied in the experiments. Shortly, this study is done for determination of the most stable mirror and prism mount design and adhesive combination of a laser system subjected to extremely harsh environments.

A pulsed-plasma jet (called a "spark-jet" by other researchers), is a high-speed synthetic jet that is generated by striking an electrical discharge in a small cavity. The gas in the cavity pressurizes owing to the heating and is allowed to escape through a small orifice. A series of experiments were conducted to determine the characteristics of the pulsed-plasma jet issuing into stagnant air at a pressure of 45 Torr. These results show that typical jet exit velocities of about 250 m/s can be induced with discharge energies of about 30 mJ per jet. Furthermore, the maximum pulsing frequency was found to be about 5 kHz, because above this frequency the jet begins to misfire. The misfiring appears to be due to the finite time it takes for the cavity to be recharged with ambient air between discharge pulses. The velocity at the exit of the jet is found to be primarily dependent on the discharge current and independent of other discharge parameters such as cavity volume and orifice diameter. Temperature measurements are made using optical emission spectroscopy and reveal the presence of considerable non-equilibrium between rotational and vibrational modes. The gas heating efficiency was found to be 10% and this parameter is shown to have a direct effect on the plasma jet velocity. These results indicate that the pulsed-plasma jet creates a sufficiently strong flow perturbation that is holds great promise as a supersonic flow actuator. An experimental study is conducted to characterize the performance of a pulsed-plasma jet for potential use in supersonic flow control applications. To obtain an estimate of the relative strength of the pulsed-plasma jet, the jet is injected normally into a Mach 3 cross-flow and the penetration distance is measured by using schlieren imaging. These measurements show that the jet penetrates 1.5 [delta], where [delta] is the boundary layer thickness, into the cross-flow and the jet-to-crossflow momentum flux ratio is estimated to be 0.6. An array of pulsed-plasma jets was issued from different locations upstream of a 30-degree compression ramp in a Mach 3 flow. Furthermore, two different jet configurations were used: normal injection and pitched and skewed injection. The pitched and skewed configuration was used to see if the jets could act as high-bandwidth pulsed vortex generators. The interaction between the jets and the separation shock was studied using phase-locked schlieren imaging. Results show that the plasma jets cause a significant disturbance to the separation shock and clearly influence its unsteadiness. While all plasma jet configurations tested caused an upstream motion of the separation shock, pitched and skewed plasma jets caused an initial downstream shock motion before the upstream motion, demonstrating the potential use of these plasma jets as vortex generator jets. The effect of the plasma jet array on the separation shock unsteadiness is studied in a time-resolved manner by using 10 kHz schlieren imaging and fast-response wall pressure measurements. An array of three pulsed-plasma jets, in a pitched and skewed configuration, is used to force the unsteady motion of the interaction formed by a 24° compression ramp in a Mach 3 flow. The Reynolds number of the incoming boundary layer is Re[theta]=3300. Results show that when the pulsed jet array is placed upstream of the interaction, the jets cause the separation shock to move in a quasi-periodic manner, i.e., nearly in sync with the pulsing cycle. As the jet fluid convects across the separation shock, the shock responds by moving upstream, which is primarily due to the presence of hot gas and hence the lower effective Mach number of the incoming flow. Once the hot gases pass through the interaction, the separation shock recovers by moving downstream, and this recovery velocity is approximately 1% to 3% of the free stream velocity. With forcing, the low-frequency energy content of the pressure fluctuations at a given location under the intermittent region decreases significantly. This is believed to be a result of an increase in the mean scale of the interaction under forced conditions. Pulsed-jet injection are also employed within the separation bubble, but negligible changes to the separation shock motion were observed. These results indicate that influencing the dynamics of this compression ramp interaction is much more effective by placing the actuator in the upstream boundary layer. / text