Between 1845 and 1848, the United States doubled the size of its land holdings in North America, as Texas, Oregon, California, New Mexico, and other western regions were placed under the umbrella of U.S. sovereignty. Echoing John L. O’Sullivan’s famous phrase, historians have deemed these acquisitions “Manifest Destiny,” and have assumed that U.S. expansion – whether for good or ill – was foreordained. Yet this understanding fundamentally fails to take into account the history of the decade prior to 1846, when Americans throughout the continent believed that it was more likely that the United States would not expand beyond its borders. Examining five groups of Americans operating at the nations geographic and/or social margins, this dissertation argues that these groups hoped to achieve sovereignty outside of the United States. Nurtured by Jacksonian rhetoric that celebrated local government and personal ambition, and wary of – and at times running from – a United States mired in depression and uncertainty, these Americans were, in effect, forming their own “breakaway republics.” To validate their goal of self-sovereignty, breakaway republicans looked to the independent Republic of Texas, often referring to Texas to explain their objectives, or looking to Texas as an ally in achieving them. Between 1836 and 1845 – what this dissertation defines as “the Texas Moment” – Texas’ independent existence presupposed a different map of North America, where peoples of the northern, southern, and western borderlands carved out polities for themselves. With Texas in mind, even Americans who did not share the goals of breakaway republicans believed that independent American-led polities on the continent were likely, acceptable, and perhaps even desired. However, to a cabal of Democratic expansionists and James K. Polk in particular, this future was unacceptable. After winning the presidency after an unlikely series of contingencies in 1844, Polk and his allies laid the groundwork for a dramatic expansion of the U.S. state – and thereby a dramatic expansion of U.S. territory. Their actions ended the Texas Moment, thereby subsuming the actions of breakaway republicans and hiding their collective existence from later historians. Ultimately, the events of the mid-1840s were hardly the logical culmination of America’s expansionist destiny, but a profound rupture of the status quo. / History

The motivation of this research is to explore the viability of a method to directly verify whether or not an anaerobic adhesive within a threaded fastener assembly has cured sufficiently to provide secondary locking. Direct verification was implemented via the application of a test torque in the loosening direction of a fastener assembly with Loctite (given a 24 hour cure time). A three phase test plan was developed with the intent of identifying and utilizing this verification torque value which is unique to a given fastener assembly. It was proved that the direct verification method, as outlined in the test plan, was in fact a valid method of verification in some cases. Results were dependent on the materials and coatings of the fastener assemblies. The curing properties of the liquid locking compound (LLC) with plain steel specimens resulted in a verification test that could accurately predict sufficient locking and cure (using distributions in torque measurements). Tests with zinc coated and stainless steel specimens, however, did not produce the same level of predictability in cure as the plain steel specimens. The direct verification method as defined herein is not suited to certain materials and coatings. The less predictable curing properties of the stainless steel specimens caused complications in determining a verification torque that could reliably determine cure, resulting in dropping stainless steel from static and dynamic testing. The zinc coated specimen data was more consistent, but the adhesive did not add sufficient breakaway strength to the fastener assembly needed to define a usable verification value. These results led to the conclusion that the direct verification method as presented in this work is limited to more active material selections. One possibility to improve the secondary locking of less active materials is the use of a higher strength adhesive. Testing to observe the effect of application of verification torque on the secondary locking was also performed. Multiple verifications were found to be destructive to the point that just over a third of samples failed that might have otherwise passed a single verification test. The single verification testing, on the other hand, caused substantially less locking mechanism degradation, leading to the use of a single verification torque in further testing.

L'oxydation thermique est souvent étudiée par les méthodes classiques : mesure thermogravimétrie et observations MEB. L'utilisation de l'EA n'a pas encore été largement développée dans le domaine de l'oxydation thermique. Le présent travail vise à utiliser l'EA pour suivre in-situ l'oxydation et détecter les phénomènes physiques se produisant à haute température. Il porte sur deux groupes de matériaux : sensibles à l'oxydation catastrophique (Ti, Zy-4) et passifs (Cr, Ni). Ce travail présente tout d'abord l'oxydation du Ti pur à 900°C sous 150 mbar d'O2, en tant que matériau modèle. Il aborde également l'influence de la température, de l'atmosphère et de l'état de surface sur le comportement d'EA. L'oxydation du Zy-4, du Cr pur et du Ni pur sous oxygène et/ou sous vapeur d'eau est ensuite étudiée. Les ondes élastiques issues de l'oxydation sont converties en signaux d'EA via un capteur, lequel est collé au côté froid d'un guide d'onde en alumine. Une corrélation entre les mesures d'EA et les résultats classiques a été mise en évidence. La technique d'EA est capable de détecter l'oxydation catastrophique et d'identifier le mode de rupture de l'oxyde. Au-delà des paramètres discriminants d'EA, nous observons deux populations distinctes : la population dite normale est attribuée au bruit de fond et aux relaxations des contraintes dans l'oxyde associées à des phénomènes de fluage micro-mécanique, probablement situé aux joints de grains. La vitesse d'EA peut alors dépendre du niveau de ces contraintes et/ou de leurs relaxations. La population post-transitoire est associée à l'endommagement de l'oxyde conduisant à l'oxydation catastrophique. Selon le niveau d'énergie de transition, le mode de rupture de l'oxyde pourra être identifié. En revanche, l'EA n'a pas donné de résultats probants sur les matériaux passifs. Des signaux enregistrés ont pour principale origine le bruit de fond. / Thermal oxidation was often studied by conventional methods: thermogravimetric measurement and SEM observations. The use of AE has not yet been widely developed in the field of thermal oxidation. The present work aims to use AE to monitor on-line oxidation and detect physical phenomena occurring at high temperature. It focuses on two groups of materials: susceptible to catastrophic oxidation (Ti, Zy-4) and passive (Cr, Ni). This work first presents the oxidation of pure Ti at 900°C under 150 mbar of O2, as a model material. It also discusses the influence of temperature, atmosphere and surface condition on acoustic behaviour. Oxidation of Zy-4, pure Cr and Ni in pure oxygen and/or under water vapour is then studied. Elastic waves from oxidation are converted into AE signals via a sensor, which is placed outside the furnace by an alumina wave guide. A correlation between AE measures and classical results was highlighted. AE technique was able to detect catastrophic oxidation and identify failure modes of the oxide. Beyond the AE discriminated parameters, we observed two distinct populations: the so-called normal population is attributed to background noise and relaxation of stresses in the oxide associated with micro-mechanic creep, probably located at grain boundaries. AE velocity may then depend on stress level and/or their relaxation. Post-transition population is associated to oxide failure leading to breakaway oxidation. According to the transition energy level, the oxide failure modes could be identified. However, AE did not give conclusive results on passive materials. Recorded signals are mainly caused by background noise.

La croissance de la couche d'oxyde en oxydation haute température induit la génération de contraintes dans le système métal/oxyde pouvant être responsable d'un endommagement de ce film d'oxyde lui faisant ainsi perdre son caractère protecteur vis-à-vis du substrat métallique. L'étude se base sur l'essai de déflexion par oxydation monofaciale (DTMO) du système Zr/ZrO2: l'asymétrie de contraintes dans une lame mince créée par la protection d'une de ses faces, génère la courbure de celle-ci du côté de l'oxyde formé, étant sujet à de fortes contraintes de compression internes. Une campagne d'essais servira de référence pour la confrontation avec un modèle semi-analytique de comportement élasto-viscoplastique décrivant l'essai de DTMO en isotherme. Le modèle prend en compte les différentes déformations affectant le système métal/oxyde (notamment le fluage et les déformations chimiques). Les paramètres matériaux identifiés sont ensuite utilisée dans des modèles d'oxydation symétrique qui représentent des cas d'applications réelles pour la détermination des champs de contraintes. Ces prédictions sont confrontées aux observations de la microstructure et à une étude de l'endommagement des couches de zircone. Le phénomène de transition cinétique liée à l'apparition de l'endommagement y est mis en évidence par une analyse expérimentale multi technique. Un suivi par émission acoustique permet d'identifier des classes de signaux liées aux différents régimes de la cinétique d'oxydation du zirconium et deux tendances à la transition cinétique sont observées en thermogravimétrie et sont différenciées par la suite par des comportements différents à l'écaillage. / The oxide scale growth in high temperature oxidation leads to generation of stresses in the oxide/metal system. It could be responsible of the damage of this oxide film causing the loss of its protective character toward the metallic substrate. The study is based on the Deflection Test in Monofacial Oxidation (DTMO) of Zr/ZrO2 system: the protection of one face of a thin foil creates a stress asymmetry. It leads to the sample curvature on the oxide scale side due to internal high compressive stresses on it. A test campaign is held as a reference for a comparison with an elasto-viscoplastic semi-analytical model describing the DTMO in isotherm. This model considers the different deformations affecting the metal/oxide system (notably creep and chemical deformations). The identified material parameters are then used in symmetric oxidation models which represent real application cases for stress field determination. These predictions are confronted to microstructure observations and to an analysis of the damage in zirconia scale. The breakaway phenomenon linked to damage initiation in the oxide scale is highlighted with an experimental multi-technical analysis. With an acoustic emission monitoring, we identify clusters of signals linked to the different oxidation kinetics regimes and with thermogravimertry, two tendencies at breakaway are observed and are differentiated afterward with different behaviours at spalling.

The purpose of this study is to create a performer's guide for three separate pieces written by David Sampson. The first piece, Breakaway, is written for two trumpets and electronic accompaniment. The second piece is entitled Passage, and is written for muted flugelhorn and viola. The final piece for examination is the Sonata for trumpet entitled Triptych, a commission from the International Trumpet Guild in 1991. Although the number of compositions for trumpet has increased in the twentieth and twenty-first centuries, guides for the performer regarding pieces with unique instrumentation and internationally commissioned works extremely limited. Included in this study is an examination of the specific challenges found in Breakaway, Passage, and Triptych, with detailed consideration regarding the methods with which to execute the unique performance elements of each composition. In addition, the information found in this study will expand the number of twentieth and twenty-first century trumpet works that have been investigated in a formal research capacity.

A systematic in-depth study has been undertaken to establish the corrosion mechanism of a Model 25Cr-35Ni-Fe alloy and four commercial alloys HP40Nb, AISI314, HP40Al and Alloy 800H in low oxygen, high sulphur and carbon containing environments typically found in coal gasification and fluidised bed combustion processes. A review of present knowledge of corrosion processes in purely oxidizing, sulphidizing and carburizing environments and multiple reactant carburizing/ oxidizing, carburizing/sulphizing and oxidizing/sulphidizing environments is given. The experimental programme was designed to establish the role of sulphur on the corrosion process by studying corrosion mechanisms in a sulphurfree H2-7%C0-1.5%H2o gas, a low sulphur H2-7%C0-1.5%H20-0.2%H 2 S gas (pS2_8= 10 bar), and a high sulphur H 2 -7%C0-1.5%H 2 0-0.6%H 2 S gas (pS = lO bar) at 800'C. All_21j_hree environments had a constant partiaf pressure of oxygen (po2 = 10 bar) and carbon activity (ac = 0.3). In the sulphur-free gas the Model alloy formed a thin uniform cr 2 o 3 layer which grew at a constant parabolic rate throughout the exposure period of 0 - 5000 hours. Surface working increased the growth rate and thickness of the Cr 2 o 3 layer but created a large number of cracks and pores which allowed carbon containing gaseous species to diffuse through the oxide to form carbide precipitates in the alloy substrata. Alloying additions of Si promoted the formation of an inner SiO layer which reduced the corrosion rate by cutting off the outward diffusion of Cr, Mn and Fe. Alloying additions of Mn promoted the formation of an additional outer (Mn, Fe )Cr 2o 4 layer. The 3. 5% Al content of the HP40Al was insufficient to form a complete Al 2 o3 layer. Alloy 800H was susceptible to localised internal oxidation. Adding a low level of sulphur (0.2% H 2 S) to the gas increased the corrosion rate of the Model alloy in the 1nitial stages. This rate gradually slowed down before becoming parabolic after 1000 - 2000 hours. This was due to the nucleation of sulphides in addition to oxides. The oxides and sulphides grew side by side until the oxides overgrew the sulphides to form a complete Cr 2o3 layer which cut off further ingress of sulphur from the gas. The entrapped sulphides promoted localized thickening of the oxide layer. Eventually the sulphur redistributed from the sulphides in the scale to internal sulphide precipitates in the alloy with the corrosion rate returning to that of the sulphur-fre,e gas for the rest of the exposure period (5000 hours total). In the commercial alloys the internal sulphide precipitates prevented the inner Si02 layer becoming complete. Sulphur doped the (Mn, Fe) Cr 2 0 4 outer layer ana the intermediate Cr 2o3 layer formed from the spinal layer, increasing the number of cation . vacancies and the growth rate of the scale. These factors caused a massive Cr depletion of the alloy substrata after several thousand hours. The internal carbides became unstable which led to a massive amount of internal attack and a dramatic increase (breakaway) in the corrosion rate. Due to its thickness and the presence of Si02 inner layer the external scale became susceptible to spallation. If this occurred the oxides and sulphides nucleated on the alloy surface again but sulphides. protective alloy. insufficient Cr was available for the oxides to overgrow the The sulphides therefore grew to form a fast growing nonsulphide scale which soon led to catastrophic failure of the Increasing the level of sulphur in the gas to 0.6% H2S caused oxides and sulphides to nucleate on the surface, but in this case the sulphides overgrew the oxides to form thick fast growing non-protective sulphide scales on all the alloys.

Babbitt has long been used as the lining material in hydrodynamic sliding bearings. However, with the new operating conditions imposed on hydro-electric power plants due to grid frequency regulation, the power plants undergo more frequent starts and stops which increases the need for an alternative material with better friction characteristics at start-up compared to conventionally used white-metal (Babbitt). Polytetrafluoroethylene (PTFE) based materials have potential to provide significant improvements in hydrodynamic sliding bearings through their compliant and breakaway characteristics under loading. However, while pure PTFE can provide excellent performance, it is somewhat limited in extreme loading situations. This study is therefore aimed at investigating the tribological characteristics at the initiation of sliding (breakaway friction) of several polytetrafluoroethylene (PTFE) based materials including virgin PTFE, PTFE filled with 25% black glass, PTFE filled with 40% bronze, PTFE filled with 25% carbon, and PTFE filled with 20% glass fibre and 5% Molybdenum disulphide, as well as standard Babbitt material in lubricated sliding contact with a steel counter-face. Experiments were carried out using a reciprocating tribo-meter in the block on plate configuration with the specific goal of determining the friction characteristics at breakaway under various conditions. Apparent contact pressures of 1 to 8 MPa were applied with oil temperature levels of 25° to 85°C.Bronze- and carbon-filled PTFE and virgin PTFE were found to provide generally lower and more stable breakaway friction over the course of testing than the other materials. Breakaway friction tests after an extended stop under loading showed a maximum change in breakaway friction of 0.07 for bronze filled, carbon filled, and virgin PTFE whereas Babbitt produced an increase of 0.32 in the first cycle after the extended stop, reaching the friction level of more than three times of those of PTFE based composites. Breakaway friction for the four tested materials after an extended stop returned to the pre-stop values after 1 stroke. The effect of materials on the steel counter face was also examined using an optical profilometer finding that only glass filled composites (black glass filled PTFE, and glass fiber and MoS2 filled PTFE) produced significant polishing of the steel surface under high loads. No measurable polishing was detected for other tested materials. / <p>Validerat; 20110224 (anonymous)</p>

Mid-Tertiary metamorphic core complexes in the Basin and Range province of the western North American Cordillera are characterized by large-magnitude extensional deformation. Numerous models have been proposed for the kinematic evolution of these metamorphic core complexes. Such models generally invoke footwall isotatic rebound due to tectonic denudation, and the presence of a weak middle crust capable of flow at mid-crustal levels. In popular models of Cordilleran-style metamorphic core-complex development, initial extension occurs along a breakaway fault, which subsequently is deformed into a synform and abandoned in response to isostatic rebound, with new faults breaking forward in the dominant transport direction. In southeast Arizona, the Catalina and Pinaleño Mountains core complexes have been pointed to as type examples of this model. In this study, the “traditional” core-complex model is tested through analysis of field relations and geochronological age constraints, and by interpretation of seismic reflection profiles along a transect incorporating these core complexes. Elements of these linked core-complex systems, from southwest to northeast, include the Tucson Basin, the Santa Catalina-Rincon Mountains, the San Pedro trough, the Galiuro Mountains, the Sulphur Springs Valley, the Pinaleño Mountains, and the Safford Basin. A new digital compilation of geological data, across highly extended terranes, in conjunction with reprocessing and interpretation of a suite of industry 2-D seismic reflection profiles spanning nearly sub-parallel to regional extension, illuminate subsurface structural features related to Cenozoic crustal extension and provide new constraints on evolution of core complexes in southeast Arizona. The main objective is to develop a new kinematic model for mid-Tertiary extension and core complex evolution in southeast Arizona that incorporates new geological and geophysical observations. Geological and seismological data indicate that viable alternative models explain observations at least as well as previous core-complex models. In contrast to the “traditional” model often employed for these structures, our models suggest that the southwest- and northeast-dipping normal-fault systems on the flanks of the Galiuro Mountains extend to mid-crustal depths beneath the San Pedro trough and Sulphur-Springs Valley, respectively. In our interpretations and models, these oppositely vergent fault systems are not the breakaway faults for the Catalina and Pinaleño detachment systems.

Pour assurer une bonne résistance à l’oxydation à haute température, les couches d’oxydes thermiques formée sur les aciers inoxydables, doivent rester fines, riches en chrome et adhérentes à leur substrat métallique. Lorsque les aciers inoxydables sont soumis à des conditions sévères de températures ou d’atmosphères, l’oxydation catastrophique entraîne la croissance rapide de nodules d’oxydes de fer non protecteurs au détriment de la couche d’oxyde riche en Cr. Cette étude s’est intéressée aux différents mécanismes mis en jeu dans la perte du caractère protecteur des couches d’oxydes, dans le développement des nodules d’oxydes de fer, ainsi que dans la formation de zones d’oxydation interne. L’étude de la morphologie et de la composition des oxydes formés à l’aide de cartographie spectrale Raman ainsi que de cartographies MET et EBSD ont permis de proposer un mécanisme de formation de la zone d’oxydation interne, qui repose en partie sur l’évolution de la composition d’une couche d’oxyde « bordure » qui se forme le long des joints de grains du métal sous-jacent lors de l’oxydation. Cette étude a également démontré qu’une prédéformation avant oxydation améliore la durabilité des aciers en favorisant la formation d’une couche protectrice dès les premiers instants de l’oxydation. Lorsqu’elle survient, l’oxydation catastrophique reste localisée alors que sans prédéformation un régime protecteur n’est jamais atteint à 850 °C pour l’acier austénitique 304L. / To provide good resistance to oxidation at high temperature, the oxide layers formed on stainless steels must stay thin, rich in chromium and adhere to their metallic substrate. When the stainless steels operate at atmospheres or temperatures that are too severe, breakaway oxidation triggers the quick growth of Fe-rich oxide nodules, which are non-protective, instead of the Cr-rich layer. This study focuses on the different mechanisms that lead to the loss of the protective characteristic of the oxide layer, to the growth of the iron oxides, and in the formation of internal oxidation zones. The study of the morphology and composition of the oxides formed, along with Raman spectroscopy and TEM and EBSD mappings, allowed to propose a mechanism for the formation of the internal oxidation zone. This mechanism relies in part on the formation of a "boundary" oxide layer, that forms along the grain boundaries of the underlying metal during oxidation. This study also showed that a deformation prior to oxidation improves the durability of the steels by encouraging the formation of a protective layer during the first stages of the oxidation. When it starts, breakaway oxidation stays localized while with no deformation, a protective regime is never reached at 850 °C for austenitic stainless steel 304L.