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  Access Rights: Use restricted to UNT Community
 Decade: 2010-2019
 Collection: UNT Theses and Dissertations
Design, Synthesis and Screening of Homoleptic and Heteroleptic Platinum(ii) Pyridylazolate Complexes for N-type Semiconducting and Light-emitting Devices

Design, Synthesis and Screening of Homoleptic and Heteroleptic Platinum(ii) Pyridylazolate Complexes for N-type Semiconducting and Light-emitting Devices

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Date: August 2012
Creator: Oswald, Iain William Herbert
Description: A series of heteroleptic and homoleptic platinum(II) complexes has been synthesized and characterized towards their use in thin film devices such as organic light-emitting diodes (OLEDs) and organic thin film transistors (OTFTs). Pyridylpyrazolate- and pyridyltetrazolate-containing ligands were selected due to their structural rigidity and ease of functionalization. Single-crystal x-ray diffraction studies of two selected heteroleptic complexes show strong aggregation with preferential stacking into vertical columns with a varying degree of overlap of the neighboring square planar molecular units. It is shown that the close proximity of the molecules to one another in the stack increases semiconducting character, phosphorescence quantum yields, and shorter radiative lifetimes. The potential for these materials towards incorporation into high-efficiency doping free white OLEDs (DFW-OLEDs) for solid-state lighting and display applications has been realized and will be expanded upon by present and future embodiments of materials in this thesis.
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Design, Synthesis and Study of Supramolecular Donor – Acceptor Systems Mimicking Natural Photosynthesis Processes

Design, Synthesis and Study of Supramolecular Donor – Acceptor Systems Mimicking Natural Photosynthesis Processes

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Date: December 2015
Creator: KC, Chandra Bikram
Description: This dissertation investigates the chemical ingenuity into the development of various photoactive supramolecular donor – acceptor systems to produce clean and carbon free energy for the next generation. The process is inspired by the principles learned from nature’s approach where the solar energy is converted into the chemical energy through the natural photosynthesis process. Owing to the importance and complexity of natural photosynthesis process, we have designed ideal donor-acceptor systems to investigate their light energy harvesting properties. This process involves two major steps: the first step is the absorption of light energy by antenna or donor systems to promote them to an excited electronic state. The second step involves, the transfer of excitation energy to the reaction center, which triggers an electron transfer process within the system. Based on this principle, the research is focused into the development of artificial photosynthesis systems to investigate dynamics of photo induced energy and electron transfer events. The derivatives of Porphyrins, Phthalocyanines, BODIPY, and SubPhthalocyanines etc have been widely used as the primary building blocks for designing photoactive and electroactive ensembles in this area because of their excellent and unique photophysical and photochemical properties. Meanwhile, the fullerene, mainly its readily available version C60 is ...
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Designing Tools to Probe the Calcium-dependent Function of Arabidopsis Tonneau2

Designing Tools to Probe the Calcium-dependent Function of Arabidopsis Tonneau2

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Date: December 2013
Creator: Oremade, Oladapo O.
Description: Plants possess unique features in many aspects of development. One of these features is seen in cell wall placement during cytokinesis, which is determined by the position of the preprophase band (PPB) and the subsequent expansion of the phragmoplast that deposits the new cell wall. During phragmoplast expansion, the phragmoplast tracks to the cortical division site, which was delineated by the PPB. Thus the position of the PPB determines the orientation of the division plane. In Arabidopsis thaliana, TONNEAU2 (TON2) is required for PPB formation and has been shown to interact with a type A subunit of the PP2A phosphatase in the yeast two-hybrid system. In Arabidopsis tonneau2 (ton2) mutants, abnormalities of the cortical microtubule cytoskeleton, such as disorganization of the interphase microtubule array and lack of PPB formation before mitosis markedly affects cell shape and arrangement as well as overall plant morphology. Loss of dcd1/add1, the maize ton2 homologues gives rise to a similar phenotype in Zea mays. The TON2 protein has two EF hand domains which are calcium-binding sites. Since calcium has been known to play key roles in several areas of plant functioning, the following question was raised: “Does calcium binding contribute to the localization and function ...
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Determinants of Citizens’ 311 Use Behaviors: 311 Citizen-initiated Contact, Contact Channel Choice, and Frequent Use

Determinants of Citizens’ 311 Use Behaviors: 311 Citizen-initiated Contact, Contact Channel Choice, and Frequent Use

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Date: May 2015
Creator: Wu, Wei-Ning
Description: Facing increasingly complex policy issues and diminishing citizen satisfaction with government and service performance, managing the quality of citizen relationship management has become a main challenge for public managers. Solutions to complex policy problems of service performance and low level of citizen participation often must be developed by encouraging citizens to make their voices heard through the various participation mechanisms. Reflecting on this need, the municipal governments in the U.S. have developed centralized customer systems for citizen relationship management. 311 centralized customer system (named 311 in this study) has the functions of citizen-initiated contact, service-coproduction, and transaction, and many local governments launch 311 to maintain or enhance their relationship with the public. Using 311 is an easy and free technically for citizens, but ensuring some degree of citizen engagement and citizens’ 311 use has been challenging for local public managers of municipalities. Despite calls for the importance of 311 in the service and information delivery process, fair treatment and access to use of governmental information, citizen participation, government responsiveness, and citizen satisfaction, to the best of our understanding, no empirical studies explore citizens’ 311 behaviors in the micro and individual level in the field of public administration. This dissertation provides ...
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Determinants of Mental Health Problems Among College Students

Determinants of Mental Health Problems Among College Students

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Date: December 2010
Creator: Mirbaha-Hashemi, Fariba
Description: Many college students have reported struggling with mental health problems while dealing with challenging demands of college. The initial theoretical framework for this research was Pearlin's stress process model (SPM). Building on the SPM, the three additional mediating variables of perceived control, meaninglessness, and financial worries were added to create a composite model for the research. Mental health outcomes in the model were measured by a comprehensive range of factors, which included: psychological distress, suicide, substance abuse, and anger. Data were collected from a non-probability convenience sample of 463 undergraduate students attending a large state supported university in the southwestern region of the United States. Among the social status variables measured, being married, female, and white were significant predictors of poor mental health in the sampled college students. Poor self-image, feeling of meaninglessness, and worrying about current and future finances were significant mediating variables. Poor mental health could make individuals overwhelmed and discouraged. This is a formula for failure in college. The results of this study contribute to a better understanding of the correlates of mental health problems among college students. A greater understanding means that families and college administrations will have better ideas about how to intervene to reduce ...
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Development of Indium Oxide Nanowires as Efficient Gas Sensors

Development of Indium Oxide Nanowires as Efficient Gas Sensors

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Date: December 2011
Creator: Gali, Pradeep
Description: Crystalline indium oxide nanowires were synthesized following optimization of growth parameters. Oxygen vacancies were found to impact the optical and electronic properties of the as-grown nanowires. Photoluminescence measurements showed a strong U.V emission peak at 3.18 eV and defect peaks in the visible region at 2.85 eV, 2.66 eV and 2.5 eV. The defect peaks are attributed to neutral and charged states of oxygen vacancies. Post-growth annealing in oxygen environment and passivation with sulphur are shown to be effective in reducing the intensity of the defect induced emission. The as-grown nanowires connected in an FET type of configuration shows n-type conductivity. A single indium oxide nanowire with ohmic contacts was found to be sensitive to gas molecules adsorbed on its surface.
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Development of Silicon Nanowire Field Effect Transistors

Development of Silicon Nanowire Field Effect Transistors

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Date: December 2011
Creator: Nukala, Prathyusha
Description: An economically reliable technique for the synthesis of silicon nanowire was developed using silicon chloride as source material. The 30-40 micron long nanowires were found to have diameters ranging from 40 – 100 nm. An amorphous oxide shell covered the nanowires, post-growth. Raman spectroscopy confirmed the composition of the shell to be silicon-dioxide. Photoluminescence measurements of the as-grown nanowires showed green emission, attributed to the presence of the oxide shell. Etching of the oxide shell was found to decrease the intensity of green emission. n-type doping of the silicon nanowires was achieved using antimony as the dopant. The maximum dopant concentration was achieved by post-growth diffusion. Intrinsic nanowire parameters were determined by implementation of the as-grown and antimony doped silicon nanowires in field effect transistor configuration.
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Device Engineering for Enhanced Efficiency from Platinum(II) Phosphorescent OLEDs

Device Engineering for Enhanced Efficiency from Platinum(II) Phosphorescent OLEDs

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Date: August 2010
Creator: Li, Minghang
Description: Phosphorescent organic light emitting diodes (PHOLEDs) based on efficient electrophosphorescent dopant, platinum(II)-pyridyltriazolate complex, bis[3,5-bis(2-pyridyl)-1,2,4-triazolato]platinum(II) (Pt(ptp)2) have been studied and improved with respect to power efficiency, external efficiency, chromacity and efficiency roll-off. By studying the electrical and optical behavior of the doped devices and functionality of the various constituent layers, devices with a maximum EQE of 20.8±0.2 % and power efficiency of 45.1±0.9 lm/W (77lm/W with luminaries) have been engineered. This improvement compares to devices whose emission initially could only be detected by a photomultiplier tube in a darkened environment. These devices consisted of a 65 % bis[3,5-bis(2-pyridyl)-1,2,4-triazolato]platinum(II) (Pt(ptp)2) doped into 4,4'-bis(carbazol-9-yl)triphenylamine (CBP) an EML layer, a hole transporting layer/electron blocker of 1,1-bis[(di-4-tolylamino)phenyl]cyclohexane (TAPC), an electron transport layer of 1,3,5-tris(phenyl-2-benzimidazolyl)-benzene (TPBI), and a LiF/Al cathode. These devices show the acceptable range for warm white light quadrants and qualify to be called "warm white" even w/o adding another emissive layer. Dual EML devices composed of neat Pt(ptp)2 films emitting orange and CBP: Pt(ptp)2 film emitting blue-green produced a color rendering index (CRI) of 59 and color coordinates (CIE) of (0.47,0.49) at 1000Cd/m² with power efficiency of 12.6±0.2 lm/W and EQE of 10.8±0.2 %. Devices with two blue fluorescent emission layers as singlet ...
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Does Device Matter? Understanding How User, Device, and Usage Characteristics Influence Risky It Behaviors of Individuals

Does Device Matter? Understanding How User, Device, and Usage Characteristics Influence Risky It Behaviors of Individuals

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Date: August 2015
Creator: Negahban, Arash
Description: Over the past few years, there has been a skyrocketing growth in the use of mobile devices. Mobile devices are ushering in a new era of multi-platform media and a new paradigm of “being-always-connected”. The proliferation of mobile devices, the dramatic growth of cloud computing services, the availability of high-speed mobile internet, and the increase in the functionalities and network connectivity of mobile devices, have led to creation of a phenomenon called BYOD (Bring Your Own Device), which allows employees to connect their personal devices to corporate networks. BYOD is identified as one of the top ten technology trends in 2014 that can multiply the size of mobile workforce in organizations. However, it can also serve as a vehicle that transfers cyber security threats associated with personal mobile devices to the organizations. As BYOD opens the floodgates of various device types and platforms into organizations, identifying different sources of cyber security threats becomes indispensable. So far, there are no studies that investigated how user, device and usage characteristics affect individuals’ protective and risky IT behaviors. The goal of this dissertation is to expand the current literature in IS security by accounting for the roles of user, device, and usage characteristics ...
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Dolores Dyer: Women's Basketball and the American Dream

Dolores Dyer: Women's Basketball and the American Dream

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Date: December 2012
Creator: Roberts, Jackie
Description: Dolores Dyer played from 1952-1953 for the Texas Cowgirls, a barnstorming women's basketball team that provided a form of entertainment popular throughout the United States in that era. The story of Dyer's life demonstrates how a woman could attempt to achieve the American dream—a major theme in American history—through success in athletic competition. Dyer's participation with the Texas Cowgirls also provides a look into the circumstances that limited women's participation in professional sport during the mid-twentieth century. Women's sports studies, although some are very thorough, have gaps in the research, and women's barnstorming basketball is one of the areas often overlooked. In light of this gap, this thesis relies on a variety of sources, including primary documents from unpublished collections, archived materials, and original oral histories from several members of the Texas Cowgirls team. This thesis contains analysis of the socioeconomic factors that influenced Dolores Dyer's maturation into a professional basketball player, examines what the American dream meant to her, and evaluates the extent to which she achieved it. Overall, it constructs a social history that can serve as a foundational source for further study of women in sports during the twentieth century.
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