The transmembrane serine receptor Tsr associates with a coupling protein, CheW, and a histidine kinase, CheA, to form a ternary complex that regulates the activity of CheA. CheA activity is inhibited by binding of L-serine to Tsr. This work aims to characterize the ligand-binding properties of Tsr and the inhibitory effect of L-serine on CheA activity. The periplasmic domain of Tsr (pTsr) was purified and characterized. Analytical gel filtration and analytical ultracentrifugation indicated that binding of Lserine promotes dimerization. The binding stoichiometry and dissociation constant for binding of L-serine to pTsr were determined by fluorescence spectroscopy. As protein concentration decreased, the dissociation constant increased. A working model was proposed to account for the interactions between L-serine and pTsr. The activity of CheA in a ternary complex with full-length Tsr and CheW was analyzed by measuring the production of [32P]-phospho-CheY. (Phospho-CheY is the product of CheA catalysis.) The results revealed that binding of L-serine decreased CheA activity without changing its affinity for ATP. These findings suggest that the allosteric effect of L-serine on CheA activity might occur through V-type inhibition. Optimization of an alternative, continuous, non-radioactive assay for CheA is underway.

The texturing of ultra-high temperature ceramics (UHTCs) using weak magnetic fields is studied and developed for the first time. Textured UHTCs were prepared by magnetically assisted slip casting (MASC) in weak magnetic field (B ~ 0.5 T). Analytical calculations describing the balance of torques acting on the suspended particles suggested that texture would form at such low magnetic fields. The calculations include a novel contribution of Stokes drag arising from the inhomogeneous velocity profile of the fluid during slip casting. Experimental proof-of-concept of the theoretical calculations was successfully demonstrated. Calculations of Lotgering orientation factor (LOF) based on the intensities of the (00l) family of peaks measures by XRD revealed strong c-axis crystalline texture in TiB2 (LOF = 0.88) and ZrB2 (LOF = 0.79) along the direction of the magnetic field. Less texture was achieved in HfB2 (LOF = 0.39). In all cases, the density of the textured materials was less than that of control untextured materials, indicating that texturing hindered the densification. The findings from this work confirm the potential for more cost-effective, simple, and flexible processes to develop crystalline texture in UHTCs and other advanced ceramics and give new insight into the mechanisms of magnetic alignment of UHTCs under low magnetic fields. The microstructural evolution during slip casting and pressureless sintering is investigated. The interplay between magnetic alignment and particle packing was investigated using XRD and SEM. During MASC, the suspended particles rotate into their aligned configuration. Particles that deposit at the bottom of the mold near the plaster of Paris substrate have their alignment slightly disrupted over a ~220 μm-thick region. The aligned suspended particles lock into an aligned configuration as they consolidate, leading to a uniform degree of texturing across the entire sample height of several millimeters upon full consolidation of the particle network. If the magnetic field is removed before the particles fully consolidate, the suspended particles re-randomize their orientation. Grain size measurements done using the ASTM E112 line counting method on SEM images revealed anisotropic microstructures in green and sintered textured ZrB2 materials. Smaller effective grain sizes were observed in the direction of c-axis texture than the directions perpendicular to the texture. Grain aspect ratios of 1.20 and 1.13 were observed in materials where the c-axis texture directions were parallel (PAR) and perpendicular (PERP) to the slip casting direction, respectively. Constraint of the preferred a-axis grain growth direction in the textured materials inhibited their densification compared to the untextured material. The PERP material with the preferred grain growth direction constrained along the casting direction had smaller average grain sizes than the PAR material which contained the preferred grain growth directions in the circular plane normal to the casting direction. Compression testing suggests a trend towards higher strength and stiffness in materials with higher density. Classical catastrophic brittle failure was observed in the untextured materials, but in the textured materials some samples exhibited a multiple failure mode. The PERP material tended to exhibit superior strength and stiffness to the PAR material in the classical brittle failure mode due to the orientation of the stiffer a-axis along the loading direction and smaller average grain size in the plane normal to the loading direction in the PERP condition. In the multiple failure mode, the PAR material tended to reach higher strength values after the initial failure and reach slightly higher strains before ultimate failure due to the orientation of the compliant c-axis along the loading direction and ability of the grains elongated in the plane normal to the loading direction to rearrange themselves after initial failure(s). Regardless of density or texture condition, all ZrB2 samples survived thermal shock resistance (TSR) testing. Samples were heated to 1500°C in air, held for 30 minutes, then quenched in room temperature air. After TSR testing, oxide layers formed on the surface of the materials. The specific mass gain and oxide layer thickness tended to increase with increasing porosity and were dramatically increased when open porosity was dominant as in the CTRL 1900 condition. After TSR testing, the compressive strength and strain at failure were both higher compared to the as-sintered materials. The increases in the average compressive strength were 20%, 76%, and 57% in the CTRL, PAR, and PERP conditions, respectively. The combination of the presence of the oxide layer shifting the onset of macroscale damage to higher strain values, the dissipation of load in the more porous region near the oxide layer, and the constraining effect of the oxide layer acting against the expansion of the material contributed to reinforcement of the samples after TSR testing. The CTRL material outperformed the textured materials on average in terms of strength and stiffness due to the higher density. The results suggest that reinforcement was more effective in the PAR condition than the PERP, which may be caused by the formation of a homogenous oxide layer on the PAR while the PERP formed an anisotropic layer. The work presented in this dissertation lays the foundation for affordable, energy efficient preparation of UHTCs and other ceramic materials. Equipment costs are reduced by 3 orders of magnitude, and the operating costs and energy consumption are greatly reduced. Facilitation of the preparation of textured materials opens the door to renewed investigations into their processing and performance. This work describes in detail for the first time the relationships between processing, microstructure, and properties of a textured UHTC part, providing a model for future research. Finally, the findings in this work can be used to guide process optimization, exploration of complex shapes and microstructures, and design of manufacturing schemes to create specialty textured parts for demanding structural and functional applications. / Doctor of Philosophy / Textured ultra-high temperature ceramics (UHTCs), special materials with melting temperatures above 3000°C and potential for use in thermal protection of Mach 5+ aircraft and spacecraft, were prepared by magnetically assisted slip casting (MASC) in a weak magnetic field for the first time. The magnetic field was supplied by commercially available permanent magnets which was applied to a liquid-like slurry with UHTC particles floating in it to orient the UHTC particles with their c-crystal axis along the magnetic field direction. Calculations which described the balance of rotational forces acting to align or misalign the suspended particles suggested that the UHTC particles would align in the weak magnetic field. This prediction was realized. After the liquid in the slurry was removed during MASC to leave behind an aligned particle network, the samples were densified by heating in the absence of air to 2100°C for one hour. In titanium diboride (TiB2) and zirconium diboride (ZrB2), two of the most relevant UHTC materials, strong texture was achieved; 88% and 79% of the crystals in the material were aligned along the original magnetic field direction. This is the first time that this has been reported in the scientific literature. In hafnium diboride (HfB2), only 39% of the grains were aligned. The textured materials all had lower density than the untextured materials prepared alongside them using conventional slip casting. The relationship between magnetic alignment and particle packing was investigated by observing the microstructure. During MASC, the suspended particles rotate into their aligned configuration. Particles that deposit at the bottom of the mold near the plaster of Paris substrate have their alignment slightly disrupted over a ~220 μm-thick region. The aligned suspended particles lock into an aligned configuration as they consolidate, leading to a uniform degree of texturing over across the entire sample height of several millimeters upon full consolidation of the particle network. If the magnetic field is removed before the particles fully consolidate, the suspended particles re-randomize their orientation. The findings from this work confirm the potential for more cost-effective, simple, and flexible processes to develop crystalline texture in UHTCs and other advanced ceramics and give new insight into the mechanisms of magnetic alignment of UHTCs under low magnetic fields. Because of the magnetic alignment of the particles, it is expected that the microstructure would show some difference along and across the direction that the alignment formed along the applied magnetic field. In order to determine that, the size of the grains (particles joined to each other during densification) in the materials are measured along different directions in the sample chosen for their orientational relationship to the magnetic field and casting directions. Smaller effective grain sizes were observed along the direction of magnetically aligned crystalline texture than the directions perpendicular to the texture. Because of how the crystal axes of the particles are aligned, there are differences in how the particles join each other during densification, and that results in an anisotropic microstructure where different grain sizes as a function of the magnetic field direction and the texture direction. Compression testing conducted by squeezing the samples at a fixed rate suggests a trend that indicates the samples are stronger and stiffer when the density is higher, as expected. Untextured samples abruptly failed after reaching their maximum strength value in a manner typical of brittle ceramics. Some textured samples failed in this way, but some failed at low strength values then climbed back up in strength repeatedly until they eventually gave out completely, in a crumbly mode. In the classical brittle failure mode, the PERP material with c-axis texture aligned along the sample diameter, perpendicular to the loading direction, tended to exhibit superior strength and stiffness to the PAR material with c-axis texture oriented along the height and loading directions of the sample because the stiffer crystal axis was oriented along the loading direction and the average grain size seen by the load head was smaller. In the crumbly mode, the PAR material tended to reach higher strength values after initial failure and ultimately fail later in a crumblier mode because the more compliant crystal axis was oriented along the loading direction and the grains elongated in the plane perpendicular to the loading direction could rearrange themselves better after initial failure(s) to bear more load. Regardless of density or texture condition, all ZrB2 samples survived thermal shock resistance (TSR) testing, meaning that the samples remained fully intact after experiencing a big difference in temperature in very short time. Samples were heated in a furnace to 1500°C in air, held for 30 minutes, removed from the furnace, and cooled in air. After TSR testing, the samples developed an oxide layer on the outside, in a similar manner to rust forming on a piece of metal. How much it oxidized per unit area and how thick that oxide layer was increased with increasing porosity. These quantities increased dramatically when the pores connected the interior of the sample to the outside, as in the CTRL 1900 condition. After TSR testing, the samples were stronger by 20%, 76%, and 57% in the CTRL, PAR, and PERP conditions, respectively, indicating that the oxide layer was responsible for an enhancement in strength. The results suggest that increase of strength of the oxide layer was more effective in the PAR condition than the PERP, which is believed to be caused by the formation of a homogenous oxide layer on the PAR while the PERP formed an anisotropic layer. The work presented in this dissertation reduces the start-up equipment costs associated with magnetic alignment processes by 1000 times and lays the foundation for affordable, energy efficient preparation of UHTCs and other ceramic materials. The simplicity of this technique makes it easier for future researchers to study textured materials. This work describes in detail for the first time the relationships between processing, microstructure, and properties of a textured UHTC part, providing a model for future research. Finally, the findings in this work can be used to guide process optimization, exploration of complex shapes and microstructures, and design of manufacturing schemes to create specialty textured parts for demanding applications.

abstract: A recent joint study by Arizona State University and the Arizona Department of Transportation (ADOT) was conducted to evaluate certain Warm Mix Asphalt (WMA) properties in the laboratory. WMA material was taken from an actual ADOT project that involved two WMA sections. The first section used a foamed-based WMA admixture, and the second section used a chemical-based WMA admixture. The rest of the project included control hot mix asphalt (HMA) mixture. The evaluation included testing of field-core specimens and laboratory compacted specimens. The laboratory specimens were compacted at two different temperatures; 270 °F (132 °C) and 310 °F (154 °C). The experimental plan included four laboratory tests: the dynamic modulus (E*), indirect tensile strength (IDT), moisture damage evaluation using AASHTO T-283 test, and the Hamburg Wheel-track Test. The dynamic modulus E* results of the field cores at 70 °F showed similar E* values for control HMA and foaming-based WMA mixtures; the E* values of the chemical-based WMA mixture were relatively higher. IDT test results of the field cores had comparable finding as the E* results. For the laboratory compacted specimens, both E* and IDT results indicated that decreasing the compaction temperatures from 310 °F to 270 °F did not have any negative effect on the material strength for both WMA mixtures; while the control HMA strength was affected to some extent. It was noticed that E* and IDT results of the chemical-based WMA field cores were high; however, the laboratory compacted specimens results didn't show the same tendency. The moisture sensitivity findings from TSR test disagreed with those of Hamburg test; while TSR results indicated relatively low values of about 60% for all three mixtures, Hamburg test results were quite excellent. In general, the results of this study indicated that both WMA mixes can be best evaluated through field compacted mixes/cores; the results of the laboratory compacted specimens were helpful to a certain extent. The dynamic moduli for the field-core specimens were higher than for those compacted in the laboratory. The moisture damage findings indicated that more investigations are needed to evaluate moisture damage susceptibility in field. / Dissertation/Thesis / M.S. Civil and Environmental Engineering 2011

abstract: Asphalt concrete is the most recycled material in the United States and its reclamation allows the positive reuse of the constituent aggregates and asphalt binder, contributing to the long-term sustainability of the transportation infrastructure; decreasing costs, and the total energy and greenhouse emissions embodied into new materials and infrastructure. Although the national trends in Reclaimed Asphalt Pavements (RAP) usage are encouraging, the environmental conditions in Phoenix, Arizona are extreme and needs further consideration. The objective of this research study was to evaluate the viability of using RAP in future pavement maintenance and rehabilitation projects for the City. Agencies in the State of Arizona have been slow adopting the use of RAP as a regular practice. While the potential benefits are great, there is some concern on the impact to long-term pavement performance. RAP millings were sampled from the city’s stockpiles; processed RAP and virgin materials were provided by a local plant. Two asphalt binders were used: PG 70-10 and PG 64-16. RAP variability was evaluated by aggregate gradations; extracted and recovered binder was tested for properties and grading. A mixture design procedure based on the City’s specifications was defined to establish trial blends. RAP incorporation was based on national and local practices. Four different RAP contents were studied 10%, 15%, 25%, and 25% content with a softer binder, in addition to a control mix (0% RAP). Performance tests included: dynamic modulus to evaluate stiffness; Flow Number, to assess susceptibility for permanent deformation (rutting); and Tensile Strength Ratio as a measure of susceptibility to moisture damage. Binder testing showed very stiff recovered asphalts and variable contents with a reasonable variability on aggregate gradations. Performance test results showed slightly higher modulus as RAP content increases, showing a slight improvement related to rutting as well. For moisture damage potential, all mixtures performed well showing improvement for RAP mixtures in most cases. Statistical analysis showed that 0%, 10%, 15% and 25% with softer binder do not present significant statistical difference among mixtures, indicating that moderate RAP contents are feasible to use within the City paving operations and will not affect greatly nor negatively the pavement performance. / Dissertation/Thesis / Masters Thesis Civil, Environmental and Sustainable Engineering 2018

Twelve field projects were studied where fortyour locations were evaluated to assess the cause or causes of asphalt concrete that exhibits ‘tender zone’ characteristics and to investigate the tendency of these mixes to be susceptible to moisture damage. Data was collected during construction and samples were obtained to conduct laboratory tests. Field and laboratory data was used to develop multiple regression equations to predict final in place air voids and moisture susceptibility. The overall conclusion was that compactability appeared to be predicted in a reasonable manner while moisture susceptibility did not. The Methylene Blue test appears promising when used in conjunction with cold feed and/or mix moisture as a means of providing guidance for achieving higher in place density. The tensile strength ratio (TSR) test as performed in this research on laboratory compacted specimens was found to be questionable in terms of its ability to predict field moisture susceptibility.

Le soufre est présent dans les systèmes pétroliers à la fois sous forme organique et minérale. Il est impliqué dans de nombreuses réactions d'oxydoréduction qui affectent la qualité des huiles (par des réactions de sulfuration ou de désulfuration) et du gaz naturel (par la génération de H2S en contexte de réduction thermochimique des sulfates), ainsi que la porosité des roches réservoirs (par la dissolution de l'anhydrite ou la précipitation de soufre élémentaire ou de pyrobitume). Ces réactions sont gouvernées par la température (et dans une moindre mesure la pression), les conditions d'oxydoréduction et la composition chimique globale du système. La thèse comporte trois parties : (1) une étude thermodynamique des réactions chimiques impliquant le soufre dans les bassins sédimentaires ; (2) une étude expérimentale des réactions de sulfuration et de désulfuration des composés organiques ainsi que de la réduction thermochimique des sulfates; (3) une étude pétrographique et d'inclusions fluides sur des échantillons d'un réservoir carbonaté du bassin Pré-Caspien / Sulfur occurs in petroleum systems as both organic compounds and minerals as well as under different oxidation states. It is involved in a number of redox reactions which may impact the quality of crude oils (through sulfurization or desulfurization reactions) and natural gas (through the generation of H2S during thermochemical sulfate reduction), as well as the petrophysical properties of reservoir rocks (through the dissolution of anhydrite and the precipitation of elemental sulfur and pyrobitumen). These reactions are controlled by temperature (and to a lesser extent pressure), the redox conditions, and the overall chemical composition of the system representing the petroleum reservoir. The thesis consists of three parts: (1) a thermodynamic study of chemical reactions involving sulfur which occur in sedimentary basins; (2) an experimental simulation of sulfurization and desulfurization reactions of organic compounds, as well as of thermochemical sulfate reduction; and (3) a petrographic and fluid inclusion study of carbonate rock samples from a sulfur-rich hydrocarbon reservoir of the northern Caspian Sea

Flexible AC Transmission Systems (FACTS) have the ability of voltage supportand increase transmission capacity. In order to specify a FACTS devicethat is performing according to expectations in a network, a set of studiesand network analyses must be performed. Part of these studies are done usingpower system analysis programs such as PSS®E, which is a planning toolsimulating large power systems in phasor domain using RMS values. Theseplanning tools are used for evaluating stability and reinforcement needs ina power system. The results play a vital role in investment decisions inthe power system. FACTS devices are modeled in PSS®E using a programminglanguage called FORTRAN. It is important to model FACTS devicesaccurately to avoid misleading results. In this Master thesis, STATCOMand Hybrid-STATCOM models are proposed and programmed accordingto ABB’s control strategy. The models are tested in PSS®E and verifiedagainst detailed models in PSCAD. Also, the models are compared againstother industry wide spread generic models. / System inom produktgruppen FACTS (Flexible AC Transmission Systems)har m¨ojligheten att st¨odja sp¨anning och h¨oja ¨overf¨oringskapacitet p°a existerandeledningar. F¨or att kunna specificera en FACTS-anl¨aggning sombeter sig som f¨orv¨antat i ett eln¨at beh¨ovs ett antal studier och n¨atanalyserutf¨oras. Delar av dessa studier ¨ar gjorda genom att anv¨anda verktyg f¨orkraftsystemanalys som t.ex. PSS®E, som ¨ar ett verktyg f¨or n¨atplaneringd¨ar fasvektorer och RMS-v¨arden anv¨ands i ber¨akningarna. Dessa verktyganv¨ands f¨or att evaluera stabilitet och utbyggnadsbehov i eln¨atet. Resultatenfr°an verktygen spelar en vital roll i investeringsbeslut i ett eln¨at.FACTS-system modelleras i PSS®E med hj¨alp av programmeringsspr°aketFORTRAN. Det ¨ar viktigt att anv¨anda korrekta modeller f¨or att undvikamissledande resultat. I denna Master-uppsats f¨oresl°as och utvecklasSTATCOM och Hybrid-STATCOM modeller i enlighet med ABBs kontrollstrategi.Modellerna testas i PSS®E och verifieras mot detaljerade modelleri PSCAD. Modellerna j¨amf¨ors ¨aven mot andra generiska modeller som ¨araccepterade och spridda ¨over branschen i stort.

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Shunt compensation devices have been a powerful candidate for expanding the limits of transmission facilities, allowing more active power transport and supporting voltage and overall stability of the network. An example of such devices is the Static Synchronous Compensator (STATCOM) which is based on Voltage Source Converter (VSC) which synthesizes output voltage and current for mainly reactive power compensation. STATCOMs might be accompanied with a Thyristor Switched Capacitor (TSC) or Reactor (TSR) which are controllable shunt devices for extra VARs required, along with passive filters for absorbing the switching harmonics generated by the VSC. Such STATCOM topology is referred as the Hybrid STATCOM.However, such configuration typically results in parallel resonances with the maingrid’s passive elements at different harmonic frequencies. This leads to amplification of background harmonics, if any exist, at the Point of Common Coupling (PCC) where the Hybrid STATCOM is connected. This thesis deals with the VSC control in the STATCOM to mitigate the harmonic amplification behavior by active filtering,which is based on emulating an impedance by the control. Also, the overall system passivity is essentially studied, which ensures a passive system with respect to harmonics. / Shunt-kompensationsanordningar har varit en kraftfull kandidat för att öka gränserna för överföringsanläggningar, vilket möjliggör högre aktiv effekt och understöderspännings-stabilitet och övergripande stabilitet i kraftnätet. Ett exempel på sådana enheter är Static Synchronous Compensator (STATCOM) som är baserat på Voltage Source Converter (VSC) som syntetiserar utspänning och ström för huvudsakligen reaktiv effektkompensation. STATCOMs kan åtföljas av en Thyristor Switched kapacitor (TSC) eller Reaktor (TSR) som är kontrollerbara shunt-apparater som ökar kapaciteten för reaktiv effekt (VARs), tillsammans med passiva filter för att absorbera övertoner som genereras av VSC. Sådan STATCOM-topologi kallas HybridSTATCOM. Emellertid, en sådan konfiguration resulterar i parallella resonanser med huvudnätets passiva element vid olika övertoner. Detta leder till förstärkning av bakgrundsövertoner, om någon existerar, vid Point of Common Coupling (PCC) där Hybrid STATCOM är ansluten. Denna avhandling behandlar hur VSC kontrolleras i STATCOM för att mildra förstärkningen av nivåer för övertoner genom aktivfiltrering, vilket är baserat på att VSC kontrollen emulerar en impedans. Dessutom studeras övergripande systempassivitet, vilket säkerställer ett passivt system med avseende på övertoner.

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