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  Partner: UNT Libraries
 Collection: UNT Theses and Dissertations
Modeling the chemical and photophysical properties of gold complexes.

Modeling the chemical and photophysical properties of gold complexes.

Date: August 2004
Creator: Barakat, Khaldoon A.
Description: Various gold complexes were computationally investigated, to probe their photophysical, geometric, and bonding properties. The geometry of AuI complexes (ground state singlet) is very sensitive to the electronic nature of the ligands: σ-donors gave a two-coordinate, linear shape; however, σ-acceptors yielded a three-coordinate, trigonal planar geometry. Doublet AuIIL3 complexes distort to T-shape, and are thus ground state models of the corresponding triplet AuIL3. The disproportionation of AuIIL3 to AuIL3 and AuIIIL3 is endothermic for all ligands investigated, however, σ-donors are better experimental targets for AuII complexes. For dimeric AuI complexes, only one gold center in the optimized triplet exciton displays a Jahn-Teller distortion, and the Au---Au distance is reduced versus the ground state distance (i.e., two reasons for large Stokes' shifts).
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Modeling the Impact and Intervention of a Sexually Transmitted Disease: Human Papilloma Virus

Modeling the Impact and Intervention of a Sexually Transmitted Disease: Human Papilloma Virus

Date: May 2006
Creator: Corley, Courtney D.
Description: Many human papilloma virus (HPV) types are sexually transmitted and HPV DNA types 16, 18, 31, and 45 account for more than 75% if all cervical dysplasia. Candidate vaccines are successfully completing US Federal Drug Agency (FDA) phase III testing and several drug companies are in licensing arbitration. Once this vaccine become available it is unlikely that 100% vaccination coverage will be probable; hence, the need for vaccination strategies that will have the greatest reduction on the endemic prevalence of HPV. This thesis introduces two discrete-time models for evaluating the effect of demographic-biased vaccination strategies: one model incorporates temporal demographics (i.e., age) in population compartments; the other non-temporal demographics (i.e., race, ethnicity). Also presented is an intuitive Web-based interface that was developed to allow the user to evaluate the effects on prevalence of a demographic-biased intervention by tailoring the model parameters to specific demographics and geographical region.
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Modeling the Relationship Between Golden Algae Blooms in Lake Texoma, Usa, Versus Nearby Land Use and Other Physical Variables

Modeling the Relationship Between Golden Algae Blooms in Lake Texoma, Usa, Versus Nearby Land Use and Other Physical Variables

Date: August 2012
Creator: Ware, Trudy M.
Description: Pyrmnesium parvum, commonly known as golden algae, is an algal species that under certain circumstances releases toxins which can lead to fish kills and the death of other economically and ecologically important organisms. One of the major objectives of the study was to investigate whether a relationship exists between land use and Prymnesium parvum abundance in littoral sites of Lake Texoma, USA. Another objective was to investigate whether a relationship exists between other physical variables and counts of P. parvum. Lastly, developing a valid model that predicts P. parvum abundance was an objective of the study. Through stepwise regression, a small but highly significant amount of the variation in P. parvum counts was found to be explained by wetlands, soil erodibility and lake elevation. The developed model provides insight for potential golden algae management plans, such as maintaining wetlands and teaching land owners the relationship between soil erosivity and golden algae blooms.
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Modeling the role of blogging in librarianship

Modeling the role of blogging in librarianship

Date: August 2007
Creator: Stephens, Michael
Description: This phenomenological study examines the motivations and experiences of librarians who author professionally-focused Weblogs. I constructed a model of librarianship based on Wilson and Buckland. The results show a close fit between librarian bloggers and the ideals of the field as expressed by two primary library and information science philosophers. A Web survey generated 239 responses to demographic and open-ended questions. Using the results of the survey, I analyzed demographic data and performed a phenomenological analysis of the open-ended questions. A list of category responses was generated from each set of answers via the coding of descriptive words and phrases. Results indicated the motivations of librarian bloggers are based around themes of sharing, participation in community, and enhanced professional development. Respondents reported feeling more connected to the profession and to colleagues across the world because of blogging. Respondents perceived the librarian blogosphere as a community with both positive aspects - feedback, discussion, and support - and negative aspects - insular voices, divides between technologists and librarians, and generational rifts. Respondents also reported an increased ability to keep current, improved writing skills, and opportunities to speak and contribute to professional journals.
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Modeling Transition Metal Catalysts for Small Molecule Activation and Functionalization

Modeling Transition Metal Catalysts for Small Molecule Activation and Functionalization

Date: May 2013
Creator: Figg, Travis M.
Description: There is a high demand for the development of processes for the conversion of ubiquitous molecules into industrially useful commodities. Transition metal catalysts are often utilized for the activation and functionalization of small organic molecules due to their diverse nature and proven utility with a myriad of chemical transformations. The functionalization of methane (CH4) and dinitrogen (N2) to methanol (CH3OH) and ammonia (NH3) respectively is of particular interest; however, both methane and dinitrogen are essentially inert due to the inherit strength of their bonds. In this dissertation a series of computational studies is performed to better understand the fundamental chemistry behind the functionalization of methane and the activation of dinitrogen in a homogeneous environment. A catalytic cycle is proposed for the oxy-functionalization of methane to methanol. The cycle consists of two key steps: (1) C-H activation across a metal-alkoxide bond (M-OR), and (2) regeneration of the M-OR species through an oxy-insertion step utilizing external oxidants. The C-H activation step has been extensively studied; however, the latter step is not as well understood with limited examples. For this work, we focus on the oxy-insertion step starting with a class of compounds known to do C-H activation (i.e., Pt(II) systems). Computational studies ...
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Modeling Transition Metal Chemistry for Catalytic Functionalization of Molecules

Modeling Transition Metal Chemistry for Catalytic Functionalization of Molecules

Date: August 2011
Creator: Morello, Glenn
Description: The diversity of transition metal complexes allows for a wide range of chemical processes to be mediated by the metal, from catalysis to surface chemistry. Investigations into the structure and electronic configuration of transition metal complexes allow for tuning of desired species by modifications to the ligands and/or metals to achieve more efficient thermodynamics and kinetics for the process of interest. Transition metals, often used in catalysts for a number of important processes, require detailed descriptions of intermediates, transition states and products to fully characterize a reaction mechanism(s) in order to design more active and efficient catalysts. Computational investigations into inorganic catalysts are explored with the aim of understanding the activity of each species and how modifications of supporting ligands, co-ligands and metals vary the interaction along the reaction pathway. Reported results give important insight into the development of the most active complexes in addition to determining the least active complexes to aid experimental development. This report first investigates the mechanisms of two unique transfer reactions: 1) formation of low coordinate nickel-nitrene ((P~P)Ni=NR; P~P = 1,2-bis(dihydrophosphino)-ethane or 1,2-bis(difluoromethylphosphino)-ethane) complexes as catalysts for nitrogen atom transfer and 2) oxidation of a triphosphorus niobium complex, [(η2-P3SnPh3)Nb(OMe)3], for the transfer of the phosphorus ...
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Modeling utilization of planned information technology

Modeling utilization of planned information technology

Date: May 2000
Creator: Stettheimer, Timothy Dwight
Description: Implementations of information technology solutions to address specific information problems are only successful when the technology is utilized. The antecedents of technology use involve user, system, task and organization characteristics as well as externalities which can affect all of these entities. However, measurement of the interaction effects between these entities can act as a proxy for individual attribute values. A model is proposed which based upon evaluation of these interaction effects can predict technology utilization. This model was tested with systems being implemented at a pediatric health care facility. Results from this study provide insight into the relationship between the antecedents of technology utilization. Specifically, task time provided significant direct causal effects on utilization. Indirect causal effects were identified in task value and perceived utility constructs. Perceived utility, along with organizational support also provided direct causal effects on user satisfaction. Task value also impacted user satisfaction in an indirect fashion. Also, results provide a predictive model and taxonomy of variables which can be applied to predict or manipulate the likelihood of utilization for planned technology.
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Modeling wild type and mutant glutathione synthetase.

Modeling wild type and mutant glutathione synthetase.

Access: Use of this item is restricted to the UNT Community.
Date: August 2004
Creator: Dinescu, Adriana
Description: Glutathione syntethase (GS) is an enzyme that belongs to the ATP-grasp superfamily and catalyzes the second step in the biosynthesis of glutathione. GS has been purified and sequenced from a variety of biological sources; still, its exact mechanism is not fully understood. Four highly conserved residues were identified in the binding site of human GS. Additionally, the G-loop residues that close the active site during catalysis were found to be conserved. Since these residues are important for catalysis, their function was studied computationally by site-directed mutagenesis. Starting from the reported crystal structure of human GS, different conformations for the wild type and mutants were obtained using molecular dynamics technique. The key interactions between residues and ligands were detected and found to be essential for enzyme activity.
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Models to Combat Email Spam Botnets and Unwanted Phone Calls

Models to Combat Email Spam Botnets and Unwanted Phone Calls

Date: May 2008
Creator: Husna, Husain
Description: With the amount of email spam received these days it is hard to imagine that spammers act individually. Nowadays, most of the spam emails have been sent from a collection of compromised machines controlled by some spammers. These compromised computers are often called bots, using which the spammers can send massive volume of spam within a short period of time. The motivation of this work is to understand and analyze the behavior of spammers through a large collection of spam mails. My research examined a the data set collected over a 2.5-year period and developed an algorithm which would give the botnet features and then classify them into various groups. Principal component analysis was used to study the association patterns of group of spammers and the individual behavior of a spammer in a given domain. This is based on the features which capture maximum variance of information we have clustered. Presence information is a growing tool towards more efficient communication and providing new services and features within a business setting and much more. The main contribution in my thesis is to propose the willingness estimator that can estimate the callee's willingness without his/her involvement, the model estimates willingness level based ...
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Moderators of the sociocultural internalization-body dissatisfaction relationship among female undergraduates.

Moderators of the sociocultural internalization-body dissatisfaction relationship among female undergraduates.

Date: December 2009
Creator: Latimer-Kern, Kelsey M.
Description: The sociocultural model of eating pathology is an empirically-supported model explaining eating disorder etiology. The model poses that body dissatisfaction and subsequent eating pathology stems from the unrealistic standards formulated by Westernized society. Although the model has strong empirical support, variables within the model do not account for 100% of the variance in disordered eating. Thus, the current researcher attempted to explore potential moderating factors in the sociocultural model of eating disorders that may help to explain variance currently unaccounted for. In particular, the researcher focused on the relationship between sociocultural internalization and body dissatisfaction, given that this relationship has not been previously explored within the literature. Based on theoretical support, the researcher chose several potential variables to test, including perfectionism, neuroticism, body surveillance, and shame. Primary analyses tested each variable for moderating effects using hierarchical moderated regression, but no significant findings were shown. Results of post hoc analyses showed all variables had significant mediating effects, with the exception of self-oriented perfectionism. The discussion section addresses consistency with previous research, limitations of the present study, treatment implications and guidelines for future research.
Contributing Partner: UNT Libraries