The thinning trend of a low-aspect ratio ignimbrite (LARI) in a direction of increasing topographic relief at the Pululagua Volcanic Complex, Ecuador, is established by correlating continuous ground penetrating radar (GPR) profiles and radar reflector behavior with stratigraphic measurements and unit behavior. Minimum density-current and vertical (cross-sectional) velocity analyses of the LARIs parent pyroclastic density-current are performed by analyzing the exchange of kinetic energy for potential energy in an upslope direction. Continuous GPR profiles were acquired in a direction of increasing topographic relief with the intent of identifying the LARI within the GPR record and examining the relationships between the LARI and the underlying paleo-topographical surface. Stratigraphic measurements recorded throughout the field area demonstrate that the LARI thins 7.5 m in an upslope direction (over 480 m distance and 95 m elevation). Stratigraphic measurements enable correlations with GPR profiles, resulting in LARI identification. By utilizing GPR derived paleo-topographical surface elevations, minimum flow velocities of the LARI-producing parent pyroclastic density-current at the base of upslope flow are shown to be at least 25 m/s. Vertical velocity analyses based on the identification of internal GPR reflectors, interpreted as flow streamlines, yield pyroclastic surge-like cross-sectional velocity profiles of the LARIs parent density-current. Maximum density-current velocities at the base of upslope flow reach 24 m/s and diminish toward the base of the current.

My thesis explores what I call the "Sopranos Experience," which draws upon both the historical conventions of the gangster genre as well as the aesthetics and economics of pay-cable television to complicate The Sopranos' (HBO, 1999-2007) psychological relationship with the 21st-century, neoliberal American audience. The Sopranos Experience explicates how wavering identifications and dis-identifications that develop for the spectator through the series' form and content draw the responsibility of an audience away from moral ultimatums that attempt to finalize their experience with the genre, and towards a more personal ethical entanglement with the characters and their socioeconomic anxieties and desires. The ethical entanglement highlighted by The Sopranos reveals an entanglement that has always existed for the gangster genre throughout its history that has been recognized, but not thoroughly explored by previous gangster scholarship. Because of the The Sopranos' psychotherapy story arc through Tony's (James Gandolfini) relationship with Dr. Melfi (Lorraine Bracco), psychoanalysis plays a key role in the Sopranos Experience. The serial form and narrowcasting develop a more in-depth psychological relationship between the spectator and the characters than seen in previous gangster genre films. Through the psychoanalytic theory of Jean Laplanche, I argue the spectator's closer relationship with the series not only results in the spectator's constitution of self through the fictional characters, but that this constitution of self extends into their lived, everyday experiences with others. In this discussion of the psychological connection between the spectator and the characters, their shared anxieties about and desires for socioeconomic stability in a neoliberal environment mobilizes the spectator's relationship not just with the series, but with others in their lives. In recognizing their atomized role in the viewership experience, The Sopranos allows the spectator to make ethical demands about their atomization and vulnerability in a neoliberal society. Because they can recognize the collective's similar situation, the spectator is situated to make larger demands about socioeconomic systems that atomize the individual.

This research focuses on empirical observations of horizontal series arc faults. These faults differ from ground faults, for series faults encompass the electromagnetic transient effects of arc formations in series with sustained current flow when there is a break in the circuit. This may happen intentionally (as in a breaker) or unintentionally (as in a loose, damaged, or severed cable). This paper studies some of those transient effects during arc ignition, propagation, and cessation. Emphasis is on dc systems, for series faults present some of the more challenging safety concerns relating to widespread dc micro-grid acceptance and proliferation. However, arc behavior is also compared to that of ac systems under “quasi-equivalent”, passive circuit parameters. Variables of study primarily include arc voltage, current, and their relationship to electrode spacing under dynamic conditions. Results indicate that interruptions in dc current, while appearing more chaotic from a localized standpoint, do not produce the fast-acting transients associated with ac disturbances. Additionally, if dc arcs propagate over a slowly increasing distance of separation, they can be modeled as quasi-static in nature. An equation model is developed and curve-fitting parameters match well with historically tabulated constants. / text

Vacuum-Arc Remelting (VAR) is an important process for manufacturing Ti- and Ni-based superalloys. Currently, the sources and mechanisms behind microstructural anomalies produced in VAR superalloy ingots are not well understood. In order to help understand formation processes, a method of characterizing specific anomalies in VAR ingots is desired. This paper presents a method of characterizing the composition and morphology of anomalies in VAR alloy ingots using a combination of serial sectioning and X-ray fluorescence (XRF) energy dispersive spectroscopy (EDS) techniques. This process is demonstrated on a dirty white spot from an Alloy 718 sample. The white spot of interest was serial polished and 2-D XRF EDS maps were acquired at each polish depth. The EDS maps were then stacked to form a 3-D representation of the white spot. In addition, SEM and optical microscopy techniques were used to further characterize the composition and morphology of the dirty white spot. The dirty white spot is composed of both Ti-enriched and Nb-depleted regions. The 2-D EDS maps acquired with the XRF equipment provided adequate contrast for creating a 3-D representation of the Ti-rich region of the dirty white spot. However, contrast was not sufficient to create a 3-D representation of the Nb-depleted region. The XRF EDS equipment combined with SEM and optical microscopy techniques provided valuable information about the morphology and composition of the Alloy 718 dirty white spot. It is concluded that this dirty white spot was produced by fall-in from either the crown or shelf regions during the VAR process. / text

The heat-affected zone (HAZ) is the most common region of weld failures. The weld failures are directly related to the microstructure. Microstructure control of the HAZ is crucial to weld quality and prevention of weld failures. However, publications on modeling the development of the HAZ are relatively limited. Moreover, no efforts have been made to predict the HAZ microstructures in real-time. The primary goal of this research is to present a methodology to enable real-time predictions of microstructure evolution in the HAZ and its mechanical properties. This goal was achieved by an approach based on materials science principles and real-time sensing techniques. In this study, the entire welding process was divided into a series of sub-processes. Real-time multiple measurements from multiple sensors were incorporated into the sub-processes. This resulted in an integrated welding system upon which the predictions for the final HAZ microstructure are based. As part of the integrated system, the microstructural model was used to predict the TTT curves, volume fractions of the decomposition products, and hardness numbers of the heat-affected zones of steel alloys. Actual welds were performed under two different sets of conditions, and the resulting experimental data were compared with predictions made using the microstructural model. The predicted and experimental microstructure and hardness are found to be in good agreement, indicating that the microstructural model can be used in real applications. This research can act as an important component of future research to enable physics-based flexible control of welding. / text

The filtered cathodic vacuum arc (FCVA) technique is a well established deposition method for wear resistant mechanical coatings. More recently, this method has attracted attention for growing ZnO based transparent conducting films. However, the potential of FCVA deposition to prepare ZnO layers for electronic devices is largely unexplored. This thesis addresses the use of FCVA deposition for the fabrication of active ZnO based electronic devices. The structural, electrical and optical characteristics of unintentionally doped ZnO films grown on different sapphire substrates were systematically investigated. The potential of FCVA to grow both polar and non-polar ZnO films was demonstrated. The resulting films showed considerable promise for device applications with properties including high transparency(> 90%), moderate intrinsic carrier concentrations (10¹⁷ - 10¹⁹ cm⁻³), electron mobilities up to 110 cm⁻²/Vs, low surface roughness (< 5 nm) and well-structured photoluminescence. Post-growth annealing in oxygen at temperatures up to 800 C produced significant improvements in the electronic and optical properties of these films, due to the formation of larger grains with lower inter-grain potential barriers. Silver oxide (AgOᵪ ) and iridium oxide (IrOᵪ) Schottky diodes fabricated on annealed FCVA ZnO films showed ideality factors as low as 1.20, barrier heights up to 0.85 eV and high sensitivity to ultraviolet light (up to ̴ 10⁻⁵ at -2 V). Transparent and opaque MESFETs fabricated on these films showed well defined field effect characteristics, channel mobilities up to 70 cm⁻²/Vs and insensitivity to 1 mW/cm⁻² visible light. These devices were further subjected to extensive bias and temperature stress tests. MESFET stability appeared to be strongly dependent on Schottky gate type, bias conditions and ZnO film morphology. Positive bias stress of AgOᵪ gated devices resulted in irreversible damage, that is thought to be due to Ag electromigration across the gate interface. Mapping of the surface potential of the ZnO channel material with Kelvin probe force microscopy suggested a strong relationship between the defect density at grain boundaries and both channel mobility and current stability. Interval growth techniques were found to reduce the density of defects at grain boundaries and produced MESFETs with higher current stability. IrOᵪ gated devices showed superior bias stability and temperature resilience from 25 C-195 C.

Most amino acid sequences are predicted to specify a single three-dimensional protein structure. However, the identification of "metamorphic" proteins, which can adopt two folds from a single amino acid sequence, has challenged the one sequence/one structure paradigm. Polar-to-hydrophobic substitutions have been suggested computationally as one mechanism to decrease structural specificity, allowing the population of novel folds. Here, we experimentally investigate the role of polar-to-hydrophobic substitutions on structural specificity in the homodimeric ribbon-helix-helix protein Arc repressor. Previous work showed that a single polar-to-hydrophobic surface substitution in the strand region of Arc repressor (Arc-N11L) populates the wild-type fold and a novel dimeric "switch" fold. In this work, we investigate an Arc repressor variant with the N11L substitution plus two additional polar-to-hydrophobic surface substitutions (Arc-S-VLV). We determine that this sequence folds into at least three structures: both dimer forms present in Arc-N11L, and a novel octamer structure containing higher stability and less helicity than the dimer folds. We are able to isolate and stabilize a core of the S-VLV octamer by limited trypsinolysis and deletion mutagenesis (Arc-VLV 4-44). The shortened construct contains only the octameric structure by removing disordered C-terminal segments nonessential for this fold. A two-dimensional NMR spectrum of VLV 4-44 and subsequent trypsinolysis of this construct suggests that at least two types of subunits comprise the S-VLV octamer: subunits structured from residues 4 to 44 and subunits structured from residues 4 to 31. Crystal trials of trypsinolyzed Arc-VLV 4-44 yielded several leads, suggesting that obtaining a high resolution structure of the S-VLV octamer is possible. Relatedly, we determine that the proline residues flanking the Arc repressor strand act in concert as "gatekeepers" to prevent aggregation in the S-VLV sequence. We also find that three highly hydrophobic surface substitutions in the Arc repressor strand region are necessary and sufficient to promote higher-order oligomer formation. In summation, this work reveals in an experimental context that progressive increases in polar-to-hydrophobic surface substitutions populate increasingly diverse, structurally degenerate folds. These results suggest that "metamorphic" as well as "polymetamorphic" proteins, which adopt numerous folds, are possible outcomes for a single protein sequence.

No description available.

The uplift history of the Tibetan Plateau is poorly constrained in part due to its complex and extended tectonic history. This study uses basin analysis, stable isotope analysis, magnetostratigraphy, detrital zircon U-Pb dating, and paleoaltimetry, and frequency analysis to reconstruct the tectonic, spatial, and environmental evolution of the Zhada basin in southwestern Tibet since the late Miocene. The Zhada Formation, which occupies the Zhada basin and consists of ~ 850 m of fluvial, alluvial fan, eolian, and lacustrine sediments, is undeformed and lies in angular unconformity above Tethyan sedimentary sequence strata. The most negative Miocene δ¹⁸Opsw (paleo-surface water) values reconstructed from aquatic gastropods are significantly more negative than the most negative modern δ¹⁸O(sw) (surface water) values. In the absence of any known climate change which would have produced this difference, we interpret it as indicating a decrease in elevation in the catchment between the late Miocene and the present. Basin analysis indicates that the decrease in elevation was accomplished by two low-angle detachment faults which root beneath the Zhada basin and exhume mid-crustal rocks. This exhumation results from ongoing arc-parallel extension and provides accommodation for Zhada basin fill. Sequence stratigraphy shows that the basin evolved from an overfilled to an underfilled basin but that further evolution was truncated by an abrupt return to overfilled, incising conditions. This evolution is linked to progressive damming of the paleo-Sutlej River. During the underfilled portion of basin evolution, depositional environments were strongly influenced by Milancovitch cyclicity: particularly at the precession and eccentricity frequencies.

Les torches à arcs plasma sont actuellement utilisées dans de nombreuses applications industrielles. Une technologie plasma triphasée à électrodes en graphite est en cours de développement au Centre PERSEE MINES ParisTech. Cette technologie diffère sensiblement des technologies à courant continu traditionnelles et vise à dépasser certaines limites des systèmes actuels en termes de robustesse, de coûts d'équipement et d'exploitation pour des applications liées à conversion et la valorisation de biomasse et déchets. Dans le but d'améliorer la compréhension des phénomènes physiques instationnaires intervenant dans les décharges triphasées, une étude menée en parallèle sur les plans théorique et expérimental a été conduite en conditions non réactives (azote et gaz de synthèse). Sur un plan expérimental cette étude s'est appuyée sur des analyses réalisées avec une caméra ultra rapide (100 000 images par seconde) et l'analyse des signaux électriques. Sur un plan théorique cette étude a consisté à développer un modèle Magnéto-Hydro-Dynamique (MHD) 3D instationnaire de la zone d'arc dans l'environnement du logiciel Code Saturne® et à effectuer une étude paramétrique basée sur le courant, la fréquence et le débit de gaz plasma. Deux configurations : électrodes coplanaires et parallèles ont été étudiées. Cette étude a permis de mettre en avant l'influence des phénomènes électromagnétiques et hydrodynamiques sur le déplacement de l'arc. Dans le cas coplanaire les jets aux électrodes semblent jouer un rôle prépondérant sur le mouvement des arcs, les transferts de chaleur dans l'espace inter électrode et l'amorçage des arcs. Dans le cas parallèle le mouvement des canaux chauds semble être le paramètre dominant. La confrontation des résultats théoriques et expérimentaux a montré un très bon accord à la fois au niveau du mouvement des arcs et des signaux électriques.