Now showing items 16366-16385 of 20306

    • The Roles of Electrode Contacts in Organic Photovoltaics

      Armstrong, Neal R.; Zacher, Brian James; Adamowicz, Ludwik; Miranda, Katrina M.; Monti Masel, Oliver L.; Armstrong, Neal R. (The University of Arizona., 2013)
      In organic photovoltaic (OPV) devices, the outer interface structures are crucial in establishing the environment to which charge collection efficiency is keenly sensitive. These outer structures consist of both the physical electrodes and the subsequent electrode contacts formed by integrating electrodes with photoactive materials. Currently, fundamental understanding and strict control of contact effects within OPVs is insufficient. This dissertation is a compilation of this author's research devoted to understanding, modifying, characterizing, and controlling contact effects in OPVs. An overview of the role of electrodes and electrode contacts in OPVs is presented in the Introduction (Chapter 1). The following three chapters each embody a fulfilled research project focusing on a specific aspect of the roles and impacts of electrodes and contacts in OPVs. Chapter 2 presents the work of a modeling study on the impacts of electrical surface heterogeneity on OPV performance and establishes guidelines for acceptable degrees of surface electrical heterogeneity. Chapter 3 explores the use of electrochemically deposited and doped conductive polymers as interlayers for OPVs. Chapter 4 utilizes metal-insulator-semiconductor capacitor (MIS-C) structures as a unique platform for isolating the role of electrodes and contacts in facilitating deleterious non-ideal injection and transport pathways in OPVs. The Conclusion (Chapter 5) presents the author's suggestions for future studies involving electrodes and electrode contacts in OPVs.
    • The Roles of MUC1 and EGFR in Breast Cancer Progression and Mammary Lactation

      Schroeder, Joyce A.; Horm, Teresa Marie; McDermott, Kimberly; Weinert, Ted; Martinez, Jesse; Schroeder, Joyce A. (The University of Arizona., 2013)
      The relationship between MUC1 and EGFR has been characterized by our lab to be highly tumorigenic. A peptide therapeutic was developed in our lab to block the cytoplasmic interaction of MUC1 and EGFR by competing with the EGFR-binding domain of MUC1. The peptide, PMIP, reduced invasion and proliferation in vitro and reduced tumor growth and metastasis in vivo. These studies demonstrated the potency of MUC1/EGFR interactions in tumor progression, and we sought to explore this concept further. We wanted to clarify a mechanism by which MUC1 and EGFR together drive breast cancer metastasis, and we identified c-Met as a mediator of MUC1 and EGFR-driven cell motility. In two separate assays, we demonstrated that c-Met activity was necessary for MUC1 and EGFR to promote migration and invasion. In addition, we wanted to identify the role of EGFR membrane localization in membrane identity and tumor initiation. We established several EGFR localization mutants to compare to wild-type basolateral EGFR and we performed proof-of-concept experiments to show that these mutants will be useful in future studies. Finally, we studied the effect of MUC1 and EGF loss on tissue architecture and function in the lactating mammary gland. EGF is the primary ligand for EGFR during lactation, and MUC1 is highly expressed during this period of mammary development. In addition, it has been shown that EGFR and MUC1 interact at the apical cell surface of lactating mammary ducts, yet there is no link between lactation and tumor formation. We hypothesized that MUC1 and EGFR interaction may have a role in maintaining tissue architecture and lactation function in the mouse mammary gland. We found instead that the loss of MUC1 and EGF had no noticeable effect on lactation and did not result in tissue defects. These studies further clarified the relationship between MUC1 and EGFR in several different contexts, showing a role for their interaction in metastatic progression, and showing that their ablation has no effect in the lactating mammary gland. Future studies will elucidate the role of MUC1 and EGFR interaction in tumor initiation, and we have taken several steps in our studies toward that goal.
    • Roles of organic cation transporters on the disposition of N-butylpyridinium chloride and structurally related ionic liquids

      Sipes, I. Glenn; Cheng, Yaofeng; Sipes, I. Glenn; Sipes, I. Glenn; Chen, Qin; Wright, Stephen H.; Cherrington, Nathan; Stamer, W. Daniel (The University of Arizona., 2010)
      Studies in this dissertation were conducted to explore the roles of organic cation transporters (OCTs) in the disposition of N-butylpyridinium Chloride (NBuPy-Cl) and structurally related ILs. Following a single i.v. dose to rats, the blood concentration of NBuPy-Cl and 1-butyl-1-methylpyrrolidinium chloride (BmPy-Cl) decreased in a biphasic manner with a clearance of 3.3 and 7 ml/min, respectively. More than 84% of dosed compounds were excreted in the urine. Depending on the vehicle, the dermal absorption of BmPy-Cl and NBuPy-Cl (5 mg/kg, 125 μg/cm²) was 10-35% at 96 h. Following a single oral (50 mg/kg) administration to rats, the maximum blood concentrations of both ILs were reached in less than 90 min in rats. Most of the orally dosed NBuPy-Cl (62-68 %) was excreted in the urine in 72 h. However, more of the dosed BmPy-Cl was eliminated in the feces Its oral bioavailability was only 47%. The elimination differences between BmPy-Cl and NBuPy-Cl were not altered by the size (0.5, 5, or 50 mg/kg) or frequency (1 or 5 administrations) of oral doses. In all urine and blood samples, only parent compounds were detected. Co-administration of NBuPy-Cl and inulin intravenously to rats revealed that the clearance of NBuPy-Cl exceeded the rat glomerular filtration rate, suggesting a renal secretion processing. The in vitro transport studies demonstrated that NBuPy-Cl, BmPy-Cl and 1-butyl-3-methylimidazolium chloride are substrates (Kt, 9~277 μM), as well as inhibitors (IC₅₀: 0.2~7.5 μM), of rOCT1/2 and hOCT2. Their inhibitory effects increased dramatically with increasing the alkyl chain length. The IC₅₀ values were 0.1, 3.8, 14 and 671 μM (hexyl-, butyl-, ethyl-pyridinium and pyridinium chloride) for rOCT2 mediated metformin transport. Similar structurally related inhibitory kinetics were observed for rOCT1 and hOCT2. In vivo co-administration of NBuPy-Cl prolonged the plasma half-life and reduced renal clearance of the diabetic drug, metformin. In summary, BmPy-Cl and NBuPy-Cl are partially absorbed from gastrointestinal tract. The present in blood is eliminated rapidly in the urine as parent, by renal filtration and OCT-mediated secretion. ILs also compete with other substrates of OCTs and have the potential to alter their pharmacokinetic profiles.
    • Roles of Parvalbumin-Expressing Interneurons in Physiological Changes to Primary Auditory Cortex After Hearing Loss and Blast Exposure

      Bao, Shaowen; Fuglevand, Andrew; Masri, Samer; Nighorn, Alan; Cowen, Stephen (The University of Arizona., 2020)
      Hearing loss affects approximately 1 in 8 Americans and has a significant impact on quality of life, often leading to tinnitus and central auditory processing disorder. Hearing loss causes a cascade of changes to the auditory processing pathway, starting with death of hair cells in the inner ear and ultimately causing a series of physiological changes in primary auditory cortex (AI). Blast exposure commonly affects veterans and can lead to hearing loss as well as Traumatic Brain Injury (TBI), which damages the soft tissue and vasculature of the central nervous system and can independently cause central auditory processing disorder. The distinct effects of hearing loss and TBI on auditory processing remain poorly understood. Further research is needed to identify the role of AI in auditory processing deficits after hearing loss and/or TBI, as well as to identify specific cellular mechanisms to serve as targets for potential therapeutic approaches. First, I identify changes to the primary auditory cortex of rats following blast exposure with associated hearing loss. This includes distortions in the normal tonotopic frequency map in the form of random, frequency specific expansions. Additionally, there are associated changes to the hearing threshold and bandwidth of frequency tuning at individual cortical recording sites. These changes outline broad physiological deficits in auditory processing in primary auditory cortex after blast exposure. Next, I show that blast exposure alone can impair temporal processing in AI, but concurrent hearing loss dramatically exacerbates these impairments. I dissociate the effects of blast exposure and hearing loss by protecting either one or both ears from hearing loss during blast exposure. While blast exposure without hearing loss causes deficits in temporal processing which could lead to central auditory processing disorder, blast exposure with associated hearing loss causes more numerous and severe deficits. Specifically, only blast exposure with concurrent hearing loss reduces the expression of the Parvalbumin protein in AI and causes deficits in gap detection behavior, which is used as a test for potential tinnitus. Finally, I show that hearing loss alone causes a set of changes to Parvalbumin-expressing inhibitory interneurons (PV neurons) in AI. This includes a reduction of Parvalbumin expression in AI, changes to the gene expression profiles of PV neurons, and an overall reduction in the inhibitory output of PV neurons. These changes are not mirrored in another population of neurons called Somatostatin-expressing interneurons. I show that deficits in gap detection behavior following hearing loss can be rescued by Chemogenetic activation of PV neurons in AI.
    • The Roles, Employment Status and Time Allocation of Foreign-Born Faculty in American Postsecondary Education

      Lee, Jenny J.; Liu, Xin; Milem, Jeffrey; Jaquette, Ozan; Lee, Jenny J. (The University of Arizona., 2012)
      As the demographics of faculty in American higher are fast changing and more foreign-born faculty entering the system, more information about this new group of entrants needs to be scrutinized. This research is aiming to answer some issues related the foreign-born professors overlooked by the mainstream studies about faculty in American postsecondary education. In the first half of this dissertation, related issues such as highly skilled immigrants and their importance to the economy, national strategy and smart power have been discussed. In the second half of this paper, some empirical research and statistical results revealed significant differences between the foreign-born and native-born faculty in terms of salary, working hours, time allocations and variances of above factors in different fields. This research suggested that foreign-born faculty is treated fairly in American academia and they enjoyed neither salary advantage nor disadvantage in comparison to their native counterparts. However, this author found empirical evidence that foreign-born did emphasize more on research by allocating more share of their work time on research and publications. This study shed some light on the researches about faculty salary, time allocation and some other aspects of employment for the foreign-born faculty. The author hopes to raise the academic interests of this topic and would like to see more detailed studies and researches in this direction.
    • ROMANTIC ART IN DISTRESS: THE DESPAIR OF FRENCH AESTHETICS IN THE TWENTIETH CENTURY.

      MACARTHUR, ROBERT. (The University of Arizona., 1982)
      This dissertation concerns itself with the period of the 1920's and 1930's in French intellectual history. Three prominent figures have been chosen from French culture of this period--Nobel Prize-winning author Roger Martin du Gard, cubist painter George Braque, and Christian existentialist Gabriel Marcel--to illustrate the thesis that this era witnessed a major breakdown in the "romantic style." This latter term is employed to describe the prevailing culture of the West dating from the eighteenth century. It is the view of this study that beyond the catastrophic wars and destruction that afflicted the West during this time, there was an underlying crisis taking place in this "romanticism" that caused as much, as was caused by, the events. Hence, the theme of this dissertation is cultural despair and illness. The subjects are used to portray this illness in the state it had reached by the 1920's and 1930's. It is concluded that basic inherent weaknesses that were latent to romanticism came to the surface in the twentieth century because that era was marked by a culmination of historical crises which exposed the hidden cultural one. The study deals with all the general tendencies of romanticism in a critical manner. The intention is to point out the dangers of some of these tendencies, and in what manner they were dealt with by the three subjects, whose approaches to romanticism were varied.
    • Ronaldo Miranda's solo and four-hand piano works: The evolution of language towards musical eclecticism

      Zumbro, Nicholas; Duarte, Vitor (The University of Arizona., 2002)
      This study attempts to demonstrate that despite the stylistic eclecticism evident in the works for piano solo and four-hands by Ronaldo Miranda, his music is grounded upon a strong preference for Classical forms. Out of his seven pieces four piano solo, five are available in addition to his two pieces for piano four-hands. Miranda's eclecticism is apparent in the high diversity of musical experiments and language found in his output. His piano pieces are dispersed within the four periods subdividing his works. Tonal, atonal and neotonal are terms that the composer himself uses to describe his music. This evolution is seen in his solo piano works from the early language of his tonal Suite #3 (1973), to the atonal pieces "Prologo, discurso e reflexao" (1980) and "Toccata" (1982), the neotonal language of his virtuoso "Estrela Brilhante" (1984), leading to the free atonalism of "Tres Micro-Pecas" (2001). Also included in this study are the "Tango" (1993), which was conceived out of the octatonic scale, and the tonal "Variacoes Serias" (1998) for piano four hands. In addition, this research demonstrates that Miranda reached a very distinctive musical style and is turning out to be among the leading active figures in contemporary Brazilian music. Even though Gerard Behague described the term "eclectic" as a phenomenon that occurred in Latin American composers during the last decades of the twentieth century, it does not appear that Miranda consciously intended to write "nationalistic" music. Instead, his pieces seem to capture the essence of Brazilian national music without resorting to direct use of folk material.
    • The Rooftop Raven Project: An Exploratory, Qualitative Study of Puzzle Solving Ability in Wild and Captive Ravens

      Jacobs, William J.; Cory, Emily Faun; Schwartz, Gary E.; King, James E.; Steklis, Horst D.; IMpey, Christopher D.; Jacobs, William J. (The University of Arizona., 2016)
      The family Corivdae, which includes crows and ravens, contains arguably some of the most intelligent species the animal kingdom has to offer. Separated from primates by at least 252 million years of evolution, birds bear striking physiological differences from mammals, while displaying similar intellectual abilities. This apparent convergent evolution of intelligence sheds light on what could possibly be a universal phenomenon. While many excellent studies show the abilities of corvids, the majority of them test only captive subjects. This study tested the capabilities of both captive and wild ravens, from three different species. The first portion of the study tested which of the four solutions offered wild ravens would choose when solving a Multi-Access Box. The second portion of the study tested the performance of wild and captive ravens when solving a Multi-Latch Box. The nine raven subjects were split into four different levels of enculturation based on their known histories. Two wild common ravens (Corvus corax) on the campus of the University of Arizona were level 1, four wild common ravens in the parking lot of a United States Forest Service parking lot were level 2, two captive and trained Chihuahuan ravens (Corvus cryptoleucus) from the Raptor Free Flight program at the Arizona-Sonora Desert Museum comprised level 3, and one captive and trained white-necked raven (Corvus albicollis) made level 4. It is possible to run trials with completely wild and free birds. It was found that ravens prefer direct methods of obtaining food, such as opening doors and pulling strings, instead of tool use. It was also found that while the relationship between enculturation level and success solving a puzzle was not linear, captive birds were the best solvers. The data given here suggest that captivity, training and enrichment history, and enculturation should all be considered when performing cognitive studies with animals.
    • ROOM-TEMPERATURE OPTICAL NONLINEARITIES IN GALLIUM-ARSENIDE AND FAST OPTICAL LOGIC GATES.

      Gibbs, Hyatt M.; LEE, YONG HEE.; Peyghambarian, Nasser; Sargent, Murray (The University of Arizona., 1986)
      This dissertation studies the physics of room-temperature optical nonlinearities in GaAs and their application to the optical logic gates. The microscopic origins of the room-temperature optical nonlinearities in GaAs are investigated experimentally and theoretically. The data of nonlinear absorption measurement are analyzed in the framework of a semiconductor plasma theory in combination with excitation-dependent line broadening. The importance of the plasma screening of the continuum-state Coulomb enhancement and band filling are emphasized for GaAs at room temperature. Optical bistability and optical logic gating are direct consequences of the nonlinear refractive index changes in etalons. The nonlinear index changes are directly measured by a new technique of observing the Fabry-Perot transmission peak shift using the self-photoluminescence as a broad-band source. The validity of a Kramers-Kronig technique under quasi-steady state conditions is crosschecked by an independent measurement of Δn under identical pumping conditions. Thermal index changes are also directly measured to establish the criteria on the temperature stability condition that is needed for reliable operation of devices based on dispersive nonlinearities. Optical logic gates based on dispersive optical nonlinearities may be the critical components of an all-optical computer in the future. Five optical logic functions are demonstrated in a nonlinear GaAs/AlGaAs MQW etalon. Specially designed dielectric mirrors are used to observe low-energy (3-pJ) operation of optical logic gates. Parallel operation using as many as eight optical logic devices is achieved with Wollaston prisms. Toward practical devices, optical logic gating using diode lasers is demonstrated in a setup much smaller than the usual argon-laser pumped dye laser setup. The cycle time of optical logic devices is limited, not by the switch-on time, but by the switch-off time which depends on the carrier relaxation rather than the switch-on time. To reduce the carrier relaxation time windowless GaAs is employed to take advantage of the faster surface recombination of carriers at the GaAs/dielectric mirror interface compared to that at the GaAs/GaAlAs interface. The speed and effectiveness of the windowless GaAs are compared with those of the proton-bombarded GaAs as optical logic gates.
    • Root and shoot development of wheat (Triticum aestivum L.) grown with limiting water

      Adjei, Gideon Boi-Tono.; Matsuda, Kaoru; Briggs, Robert E.; Stith, Lee S.; Bartels, Paul G.; Huff, Albert K. (The University of Arizona., 1982)
      Two-year studies (1979-1980, 1980-1981) designed to measure the relation of plant development to yield of spring wheats were undertaken at the University of Arizona Mesa Experiment Station and at the Casa Grande Overpass Farm, Tucson. Low density seeding rates (15 to 20 kg/ha) were used in both studies. The soil at Mesa and in Tucson were clay and sandy barns, respectively. All plants grown under limiting water conditions received 150 kg/m² pre-plant irrigation. Supplemental water as rainfall in the 1979-1980, 1980-1981 seasons were 153 and 79 kg/m² atMesa respectively, and 134 and 116 kg/m2 in Tucson for the respective seasons. Experiments were also conducted in Tucson during the two seasons to evaluate yield performance of wheats under well-watered conditions (525 kg 1m2 and 400 kg/m² irrigation water in the 1979-1980, 1980-1981 seasons, respectively) and on plants which received a single added irrigation approximately 2 to 3 weeks prior to the estimated time of anthesis. Yields in Mesa ranged from 2400 to 3700 kg/ha in 1980 and from 1800 to 3600 kg/ha in 1981. When grown under limiting water conditions in Tucson yields ranged from 1100 to 3000 kg/ha in 1980 and from 2000 to 4100 kg/ha in 1981. Productivities of plants grown with a single added irrigation ranged from 2000 to 4200 kg/ha. Under minimal water conditions yield was correlated with head weight of the main culm, average head weight, grain weight per spike, number of grains per unit land area, Leaf area and Flag leaf area indices at later stages of development, total plant dry weights, root depths and dry weights. Differences were found in tissue water status and leaf growth of selected entries. Tissue water potential was higher in a higher yielding than in a low yielding entry. Additionally, tissues at the basal region tended to be more "sensitive" to changes in soil moisture than those at the mid-section of the expanding leaf. Difficulty in sample selection and variability with plants militated against using leaf growth as an index for determining the degree of stress in field grown wheat cultivars. Neutron probe analysis of soil profile water depletion of a high yielding, long rooted cultivar was greater at the lower depths (60 to 120 cm) after anthesis than for an intermediate or low yielder.
    • Root Border Cell Development and Functions of Extracellular Proteins and DNA in Fungal Resistance at the Root Tip

      Hawes, Martha C.; Wen, Fushi; Hawes, Martha C.; VanEtten, Hans D.; Pierson, Leland S., III; Tax, Frans E.; Arnold, Anne Elizabeth (The University of Arizona., 2009)
      Soilborne plant pathogens are responsible for many of the major crop diseases worldwide. However, plant root tips are generally resistant to pathogen infections. The goal of this dissertation research is to understand the mechanism of this natural resistance by testing the hypothesis that root caps and root border cells control the rhizosphere community through the biological products which they deliver to the soil. Specific objectives of this dissertation project are 1) identifying, isolating, and characterizing the genes important for border cell development and for root exudates delivery, and 2) analyzing the function of extracellular macromolecules in root exudates in root tip-fungal pathogen interaction. The expression of a primary cell wall synthesis gene, PsFut1, encoding Pisum sativum fucosyltransferase, was characterized during border cell production, and the impact of silencing this gene on border cell development was examined. Another gene, BRDgal1, encoding β-galactosidase, was identified and characterized in Pisum sativum during this study. It was shown that this β-galactosidase is specifically produced in and secreted from root border cells. The microarray transcriptional profiling in M. truncatula and mRNA differential display analysis in pea plants were carried out following the induction of border cell production to gain a broader understanding of the genes which potentially influence border cell development. In order to study the commonality of border cell production across different plant species, the expression of rcpme1, the marker gene for border cell production, was compared between the garden pea and a gymnosperm species, the Norway spruce (Picea abies). To accomplish the second objective, the focus of this study was shifted from border cell development to mucilaginous root exudates excreted by border cells and root cap cells. This resulted in a breakthrough in the understanding of the mechanisms of root tip resistance. The presence of extracellular DNA in the root mucilage was discovered and its requirement for root tip resistance to fungal infection was demonstrated. Extracellular proteins in the root mucilage were identified and they were shown to be also required for the root tip resistance to fungal infection. This work provided new insights into understanding plant defense mechanisms.
    • Root border cell differentiation

      Hawes, Martha C.; Brigham, Lindy Andersen, 1951- (The University of Arizona., 1996)
      The inability of a plant to run from danger or seek nutrients necessitates its capacity to change the environment of the surrounding soil for protection and sustenance. A unique plant process, the release of thousands of autonomous cells from the root cap, called root border cells, may play a role in the ability of the plant to regulate microbial populations and nutrient availability in the rhizosphere. In this study, evidence is presented showing that root border cells are a differentiated tissue, that the production of border cells is highly regulated and tied to cell turnover in the root cap and that products of border cells regulate cell division in the root cap meristem. In vivo labeling experiments demonstrate that 13% of the proteins that are abundant in preparations from border cells are undetectable in root tip cells. Differences between the two cell populations are apparent as soon as border cells separate from each other, even when they are still adhered to the root tip. Twenty-five percent of the proteins synthesized by border cells in a 1-hour period are rapidly excreted into the incubation medium. Border cells arise within the root cap meristem by cell division and their production is tightly regulated both developmentally and in response to border cell removal. Removal of border cells results in the induction of cell division in the transverse root cap meristem to 400% of the basal rate within 30 minutes. This elevated rate of mitosis is maintained for 1.5 h and falls to basal levels within 6 hours. During this time, mitosis in the root apical meristem remains constant. mRNA differential display analysis showed changes in gene expression in the root cap within 5 to 15 minutes of removal of border cells. Genes putatively involved in cell functions in three regions of the cap showed expected distribution patterns by in situ hybridization and RNA blot analysis revealed changes in their expression patterns were seen in response to border cell removal. The presence of border cells acts as an inhibitor to continued mitosis and border cell production in the root cap. Evidence from fractionation studies shows that a heat stable, protease insensitive molecule in the range of 25 to 80 kDa, produced by the border cells themselves, is responsible for this inhibition.
    • Root proliferation in Medicago sativa L. (s. l.): (1) Evaluation of procedures for increased production of nondormant root-proliferating alfalfas. (2) Inheritance of the root-proliferating habit.

      Smith, Steven E.; Rodrigues, Geraldo Helcio Seoldo.; Briggs, Robert E.; Bartels, Paul G.; Stroehlein, Jack L.; Tucker, Thomas C. (The University of Arizona., 1987)
      This investigation examined the efficiency of various screening procedures which could be used in breeding for increased production of root-proliferating (RP) genotypes of alfalfa (Medicago sativa L. s. l.). Also investigated were relationships between RP and winter growth characteristics in populations derived from crosses between dormant, RP clones and nondormant, non-RP clones. In addition, this investigation also considered the inheritance of the RP habit. Plants from an 11-month F₁ progeny test containing 3508 offspring were qualitatively analyzed for RP expression using three pairs of screening procedures. Procedures compared included: (1) direct-seeding vs. transplanting; (2) use of characterized parental clones (known RP-expressing genotypes selected from field nursery) vs. uncharacterized parental clones (genotypes derived from RP seed lots with no prior knowledge of their ability to express the RP habit) in RP x nondormant crosses; and (3) low vs. high harvest frequencies. A low frequency (3.3%) of F₁ plants exhibited adventitious shoot formation. No differences were observed in the frequency of RP-expressing genotypes between the direct-seeded and transplanted treatments or between the low and high harvest frequency treatments. Characterized RP parents produced a hybrid population with a significantly higher frequency of RP-expressing genotypes than did the F₁ population derived from uncharacterized RP parents. Average winter forage production of the F₁ hybrids were similar in magnitude to the midparent value. Plant height was significantly and positively correlated with forage yield and could be used as an accurate indicator of winter forage yield in analyses of RP segregants. Estimates of components of genetic variance for RP expressivity indicated a predominance of additive effects and narrow sense heritability of 8.4%. Family selection and progeny testing are suggested for maximum breeding progress.
    • Rotational spectra and molecular structures of organometallic and organic molecules

      Kukolich, Stephen G.; Tanjaroon, Chakree (The University of Arizona., 2004)
      Understanding the nature of chemical bonds constitutes a major theme of this thesis. This thesis investigates the gas phase rotational spectra, electronic charge distributions and molecular structures of organometallic and organic molecules, using high-resolution pulsed beam Fourier transform microwave spectroscopy (PBFTMS) and computational methods. High-resolution rotational spectra and structural parameters were obtained for the following organometallic molecules in the singlet electronic state, including three symmetric and five asymmetric top complexes: C₅H₅Nb(CO)₄, CH₃Mn(CO)₅, MnRe(CO)₁₀, C₅H₅Mo(CO)₃H, C₅H₅W(CO)₃H, C₅H₅NiC₃H₅, C5H₄(CH₃)FeC₅H₅ and (C₅H₄(CH₃))₂Fe. High-resolution rotational spectra and structural parameters were obtained for three organic molecules in the singlet electronic state: ortho-benzyne (C₆H₄) and the keto-enol tautomers, 2-hydroxypyridine and 2-pyridone (C₅H₅NO). In addition to the tautomeric forms, pure rotational spectra of the H-bonded dimer, 2-hydroxypyridine:2-pyridinone, were also obtained. These detailed spectral investigations yielded novel and useful information about the molecular properties of these molecules. Primarily, these results provided information regarding chemical bonding, vibrational ground state structures, structural isomers, conformational behavior, metal-hydrogen bonding and electronic charge distributions. Density functional theory (DFT) and ab-initio calculations were carried out in conjunction with the experiments, providing additional insights into further understanding the equilibrium structures, structural isomers and the electric field gradient distributions for these molecules.
    • Rotational Spectroscopy and Gas Phase Structures of Hydrogen Bonded Dimers, Organometallic Complexes and Other Molecules

      Kukolich, Stephen; Zhou, Zunwu; Lichtenberger, Dennis; Ziurys, Lucy; Huxter, Vanessa (The University of Arizona., 2021)
      This dissertation focuses on the structural investigation of gas phase organometallic complexes, hydrogen-bonded dimers and other organic molecules through the use of pulsed-beam Fourier transform microwave spectroscopy technique and high-level computational methods. High-resolution microwave spectra and important structural parameters such as rotational constants and quadrupole coupling constants were measured and obtained for organometallic molecules ferrocenecarboxylic acid and methylmanganese pentacarbonyl, organic molecules 1-chloroborepin, phenylpropiolic acid and 2-aminopyridine, as well as hydrogen bonded dimer formamidinium formate. These studies have produced new important information for these molecules in regard to their gas phase structures, conformational behaviors, electronic charge distributions, chemical bonding and reactivity. Theoretical computations using Density Functional Theory (DFT) and ab initio methods were carried out to obtain optimized electronic structures of the molecules studied. The theoretical structures and parameters derived facilitated the scanning and assignment of rotational transitions. In addition, the comparisons between theoretically computed and experimentally determined structural parameters provide insights for structural determination of the molecules and other important molecular properties.
    • Rotational Spectroscopy and Structures of Organometallic Compounds

      Kukolich, Stephen G.; Karunatilaka, Chandana; Kukolich, Stephen G.; Ziurys, Lucy M.; Sanov, Andrei; Miranda, Katrina M.; Zheng, Zhiping (The University of Arizona., 2007)
      High-resolution pulsed beam Fourier Transform Microwave Spectroscopy (PBFTMS) technique has been used to investigate the rotational spectra, molecular structures and electronic charge distribution of organometallic and organic molecules. The thesis reports high-resolution rotational spectral findings for nine different asymmetric-top molecules in the singlet electronic ground state including: Cyclopentadienyltungstentricarbonylhydride, Bis-(cyclopentadienyl)tungstendihydride, Tetracarbonylethyleneosmium, two substituted Ferrocenes and an organic keto-enol tautomeric system, Z-2-Hydroxypyridine and 2-Pyridone. Moreover, gas-phase rotational constants and distortion constants have also been reported for an excited vibrational state of Cyclopentadienylnickelnitrosyl complex using a high-resolution Fourier Transform Spectrometer (FTS) system at Kitt Peak Arizona, (KPNO). Preliminary microwave results for a fluxional molecule, Cyclopentadienyliridiumdicarbonyl are also presented in this work. Extensive Density Functional Theory (DFT) calculations have been performed in conjunction with the experiments to provide additional insight toward further understanding the equilibrium structures, structural isomers and electric field distributions of these molecules. These calculations were not only helpful in predicting the preliminary structure and rotational constants of the molecules of interest, but also advantageous in analyzing the observed spectra.
    • Rotational Spectroscopy of Simple Metal Carbon Clusters: Resolving the Beauty of Fine and Hyperfine Interactions in Metal Monoacetylides and Metal Carbides

      Ziurys, Lucy M.; Randtke, Jie Min; Ziurys, Lucy M.; Brown, Michael; Miranda, Katrina; Sanov, Andrei (The University of Arizona., 2016)
      Pure rotational spectra of simple metal carbon clusters that relevant to transition metal synthesis and catalysis have been obtained using Fourier transform microwave (FTMW) techniques combined with millimeter-wave direct-absorption methods. Rotational spectra of metal acetylides (CuCCH, ZnCCH, Li/Na/KCCH, MgCCH, AlCCH, CrCCH), diatomic metal monocarbide (CrC) and T-shape metal dicarbides (YC₂ and ScC₂) were recorded in the 4–650 GHz frequency regime. Measurements of weaker isotoplogues including ⁶⁶ZnCCH, ⁶⁸ZnCCH, Zn¹³C¹³CH, ZnCCD, Li/Na/KCCD, CrCCD, Y¹³C¹²C, Y¹³C¹³C, Sc¹³C¹³C, were also studied to aid in structural determinations. This work is the first study of ZnCCH and ScC₂ by any type of spectroscopic technique. Hyperfine splittings in MgCCH and Li/Na/KCCH have also been resolved and the weak isotoplogues of YC₂ have been measured for the first time. Potential interstellar molecules ScO and FeCN were studied using the FTMW techniques in the 4–62 GHz frequency regime. Spectra of the zinc insertion product ClZnCH₃ were additionally recorded in the 10–30 GHz (FTMW) and 260–296 GHz (direct absorption) frequency ranges, along with weaker isotopologues Cl⁶⁶ZnCH₃ and Cl⁶⁸ZnCH₃. This works is the first measurement of zinc insertion products using the FTMW-DALAS techniques. The data were analyzed implementing an effective Hamiltonian, allowing for accurate spectroscopic parameters to be established. From rotational constants, the molecular geometries were accurately determined. Electronic properties were also assessed, including the degree of covalent vs ionic character in a chemical bond, and the molecular orbital composition. The fundamental physical and chemical properties of these benchmark species were obtained in order to gain insight into their role in larger molecular systems, test theoretical calculations, and, in certain cases, provide accurate rest frequencies for astronomical searches.
    • Roughness influence on strength and deformation behavior of rock discontinuities.

      Daemen, Jaak; Roko, Raoul Olatounbossoun.; Glass, Charles; Farmer, Ian; Benson, Clark; Myers, Donald (The University of Arizona., 1990)
      The influence of discontinuity roughness on the shear strength and deformation behavior of rock joint is analyzed. The study is divided into three parts: laboratory direct shear test on rock samples having different roughness characteristics, characterization of roughness profiles using variogram and probability density distribution and the application of dynamical systems theory to analyze the stability condition of the sliding motion. The relative motion along the rough joint is erratic particularly at a low normal load. A steady motion develops as the normal load increases. The kinematics of translational motion has two distinct characteristics: the translation occurs as a result of a gross and uniform motion (sliding) and/or through localized inhomogeneous motion (slipping). Three modes of volumetric changes are observed during the tangential motion: a dilatant-contractant behavior with the overall volumetric change being strictly dilatant, a dilatant-contractant behavior with the overall volumetric change varying from dilatant to contractant and the strictly contractant behavior. The size of the sheared zones is a function of the distribution of the asperities and of the interface strength. The coefficient of friction decreases as the normal load increases. It may or may not increase when the normal load is decreased. The probability density distribution of the height of the interface asperities is not always Gaussian. The variation of the experimental distribution (histogram) indicates that the asperities are not necessarily sheared off in order of decreasing height but rather on the basis of the condition underlying the existence of contact. The slope of the initial portion of the variogram and the sill, when it exists, are used to characterize the surface morphology of the discontinuity. The lower the slope, the smoother the surface. Two types of anisotropy are observed: geometic anisotropy (elliptic shape) and zonal anisotropy. The rate of collapse of the boundary of the loop describing the roughness of the interface describes the deformation of the discontinuity. The location of the orbit with respect to the stagnation line depends on the normalized stiffness. As the normalized shear stiffness increases, the orbit tends to collapse towards the stagnation axis.
    • Routes And Trajectories Based Dynamic Models For Traffic Prediction And Control

      Mirchandani, Pitu B.; Wu, Fan; Mirchandani, Pitu B.; Mirchandani, Pitu B.; Head, Larry; Lin, Wei Hua; Zen, Daniel Dajun (The University of Arizona., 2008)
      Network traffic assignment/equilibrium models have been widely used for transportation planning. For traffic management, one is interested on how traffic patterns change dynamically since equilibrium cannot be reached instantaneously. This dissertation focuses on modeling short-term traffic patterns in a transportation network, and addresses these topics: (1) comparison of loading route flows versus link flows, (2) development of a mesoscopic model for loading route flows in a network, (3) estimation of route flows based on the mesoscopic model, and (4) optimizing traffic signal timings based on the estimated route flows.With regard to the first topic, many models propagate flows through a network using link flows and independent turning probabilities (ITP) at nodes. Chapter 2 describes the effects of the ITP assumption on the traffic patterns that occur based on route flow loading; this provides the motivation for using route flows in this research.Route trajectories are the spatial-temporal realizations of vehicle route flow demands. This dissertation proposes a mesoscopic simulation platform where route flows are propagated through the network and dynamic trajectories are computed. Under interrupted and uninterrupted flow conditions, route trajectories from the mesoscopic model are compared with ones from a microscopic model, the latter model being used to provide realistic data since real data at this level of detail is not currently available. Results from both models match well; the corresponding traffic patterns are very similar, both graphically and statistically.In chapter 5, a model is presented for estimating temporal route flow demands when real-time data is available. The model is formulated as a bi-level optimization problem where a least-square model is constructed at the upper level and the mesoscopic model is utilized at the lower level to relate flow demands and route trajectories. Based on real-time measurements, this model estimates dynamic route flows that are consistent with observed traffic patterns. Computational results using a micro-simulator for "real" data show that the model estimates well the route flows loaded in the micro-simulation model.Finally, in chapter 6, a traffic signal control optimizer is developed based on the mesoscopic model and a gradient search to optimize any given performance index such as average delay. A numerical example shows that the optimizer significantly improves the performance index and the approach may be used for on-line traffic signal control.
    • Routing Map Topology Analysis and Application

      Chiu, Yi-Chang; Zhu, Lei; Chiu, Yi-Chang; Chiu, Yi-Chang; Wu, Yao-Jan; Tong, Daoqin; Fan, Neng (The University of Arizona., 2014)
      The transportation routing map is increasingly used in various transportation network modeling applications such as vehicle navigation and traffic assignment modeling. A typical navigation GIS map contains all detailed road facility layers and may not be as computationally efficient as a lower-resolution map for path finding. A lower-resolution transportation routing map retains only route-finding related roadways and is efficient for path finding but may result in sub-optimal routes because of misclassification links. With the goal in balancing the traffic analysis requirement of intended application and computation requirements of transportation navigation and traffic assignment, the systematic abstraction of the lower-resolution transportation routing map from high resolution map is an important and non-trivial task. For vehicle navigation applications, the traffic analysis requirement is the shortest path quality. An innovative transportation routing map abstraction method or Connectivity Enhancement Algorithm (CEA) is proposed to deal with vehicle navigation application routing map abstraction. The algorithm starts from a low-resolution network and keeps updating the map by adding links and nodes when it processes each search set. The outcome of the algorithm is an abstract map that retains the original detailed map's hierarchical structure with quality topological connectivity at a significant computations saving. With the development of traffic assignment modeling, a detailed network is desired to describe the real world traffic network. It is the consensus that one should not directly apply a GIS map blind-sight without a systematic approach and unnecessarily overuse the network details causes excessive run time. The traffic analysis requirement of those applications is the dynamic user equilibrium (DUE) condition network performance is identical or near-identical with high resolution network. The lowest network resolution level that meets the requirements of emerging traffic analysis is not easy to determine. The proposed traffic analysis network abstraction method gives a solution for this problem. It is an iterative network abstraction approach and considers the link travel time with DUE traffic condition. The case study and numerical analysis prove that the two network abstraction methods are sound and promising. The transportation routing map abstraction method could detect most misclassification links and is robust for different network scales. The abstracted navigation map provides the identical or near-identical SP cost/travel time for any OD pair while the computation burden is much lighter than that on original map. In another hand, the case studies about the traffic analysis network abstraction tell that the method converges very quick and the rendered the abstracted network that has lowest resolution of network or least links and nodes but the DUE condition network performance or trips cost/travel time is much closer to that on the original map.