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The Crystal and Molecular Structures of Tri-(p-Fluorophenyl)-Amine and Tri-(p-Iodophenyl)-Amine

Description: Because of the need for data on the geometry of nitrogen in arylamines, the determination of the crystal and molecular structures of tri-(p-fluorophenyl)-amine (TFPA) and tri-(p-iodophenyl)-amine (TIPA) was undertaken as the subject of this dissertation.
Date: January 1970
Creator: Freeman, Gerald R. (Gerald Richard)
Partner: UNT Libraries

Polycyclic Aromatic Hydrocarbon Solute Probes. Part 10: Evaluation of Select Hydrogenated Pyrene, Benzo[ghi]perylene, and Naphthacene Derivatives as Possible Solvent Polarity Probes

Description: Article on polycyclic aromatic hydrocarbon solute probes and the evaluation of select hydrogenated pyrene, benzo[ghi]perylene, and naphthacene derivatives as possible solvent polarity probes.
Date: February 16, 1993
Creator: Tucker, Sheryl A. (Sheryl Ann); Acree, William E. (William Eugene); Fetzer, John Charles, 1953- & Mitchell, Reginald H.
Partner: UNT College of Arts and Sciences

Spectroscopic Investigation of Fluorescence Quenching Agents: Effect of Nitromethane on the Fluorescence Emission Behavior of Select Cyclopenta-PAH, Aceanthrylene, and Fluorene Derivatives

Description: Article on a spectroscopic investigation of fluorescence quenching agents and the effect of nitromethane on the fluorescence emission behavior of select cyclopenta-PAH, aceanthrylene, and fluorene derivatives.
Date: March 2, 1992
Creator: Amszi, Vicki L.; Cordero, Yvonne; Smith, Bradley; Tucker, Sheryl A. (Sheryl Ann); Acree, William E. (William Eugene); Yang, Chengxi et al.
Partner: UNT College of Arts and Sciences

Cryogenic Treatment of Production Components in High-Wear Rate Wells

Description: Deep Cryogenic Tempering (DCT) is a specialized process whereby the molecular structure of a material is ''re-trained'' through cooling to -300 F and then heating to +175-1100 F. Cryocon, Inc. (hereafter referred to as Cryocon) and RMOTC entered an agreement to test the process on oilfield production components, including rod pumps, rods, couplings, and tubing. Three Shannon Formation wells were selected (TD about 500 ft) based on their proclivity for high component wear rates. Phase 1 of the test involved operation for a nominal 120 calendar day period with standard, non-treated components. In Phase 2, treated components were installed and operated for another nominal 120 calendar day period. Different cryogenic treatment profiles were used for components in each well. Rod pumps (two treated and one untreated) were not changed between test phases. One well was operated in pumped-off condition, resulting in abnormal wear and disqualification from the test. Testing shows that cryogenic treatment reduced wear of rods, couplers, and pump barrels. Testing of production tubing produced mixed results.
Date: April 29, 2002
Creator: Milliken, M.
Partner: UNT Libraries Government Documents Department

Study of anisotropy of spin cast and vapor deposited polyimide films using internal reflection techniques

Description: We have compared anisotropy of spin cast and vapor deposited polyimide (VDP) films, using internal reflection infrared spectroscopy. The films were deposited directly on the internal reflection element. We find that spin cast films are more anisotropic than their VDP counterparts, with the polyimide chains tending to align parallel to the substrate. Both films are found to contain more and less ordered regions. Within the ordered regions, the plane of the phenyl ring tends to align parallel to the substrate.
Date: November 1, 1996
Creator: Liberman, V.
Partner: UNT Libraries Government Documents Department

Invariant patterns in crystal lattices: Implications for protein folding algorithms

Description: Crystal lattices are infinite periodic graphs that occur naturally in a variety of geometries and which are of fundamental importance in polymer science. Discrete models of protein folding use crystal lattices to define the space of protein conformations. Because various crystal lattices provide discretizations of the same physical phenomenon, it is reasonable to expect that there will exist invariants across lattices related to fundamental properties of the protein folding process. This paper considers whether performance-guaranteed approximability is such an invariant for HP lattice models. The authors define a master approximation algorithm that has provable performance guarantees provided that a specific sublattice exists within a given lattice. They describe a broad class of crystal lattices that are approximable, which further suggests that approximability is a general property of HP lattice models.
Date: June 1, 2000
Creator: HART,WILLIAM E. & ISTRAIL,SORIN
Partner: UNT Libraries Government Documents Department

Synthesis and Characterization of a New Perhalogenated Porphyrin

Description: The first synthesis of an octahalotetraalkylporphyrin [2,3,7,8,12,13,17,18 -octabromo-5,10,15,20- tetrakis(trifluoromethyl)porphinato nickel(II)] is reported; this perhalogenated porphyrin has several novel properties including a very nonplanar ruffled structure with an unusually short Ni- N distance, an extremely red-shifted optical spectrum, and hindered rotation of the trifluoromethyl groups ({Delta}G<sub>278K</sub> =47 kJ mol<sup>-1</sup>).
Date: May 19, 1999
Creator: Jia, Songling; Medforth, Craig J.; Nelson, Nora Y.; Nurco, Daniel J.; Shelnutt, John & Smith, Kevin M.
Partner: UNT Libraries Government Documents Department

Responsive Copolymers for Enhanced Petroleum Recovery

Description: The objectives of this work was to: (1) synthesize responsive, amphiphilic systems; (2) characterize molecular structure and solution behavior; (3) measure rheological properties of the aqueous fluids including behavior in fixed geometry flow profiles and beds; and (4) to tailor polymer compositions for in situ rheology control under simulated reservoir conditions.
Date: February 27, 2002
Creator: McCormick, Charles & Hester, Roger
Partner: UNT Libraries Government Documents Department

Signature molecular descriptor : advanced applications.

Description: In this work we report on the development of the Signature Molecular Descriptor (or Signature) for use in the solution of inverse design problems as well as in highthroughput screening applications. The ultimate goal of using Signature is to identify novel and non-intuitive chemical structures with optimal predicted properties for a given application. We demonstrate this in three studies: green solvent design, glucocorticoid receptor ligand design and the design of inhibitors for Factor XIa. In many areas of engineering, compounds are designed and/or modified in incremental ways which rely upon heuristics or institutional knowledge. Often multiple experiments are performed and the optimal compound is identified in this brute-force fashion. Perhaps a traditional chemical scaffold is identified and movement of a substituent group around a ring constitutes the whole of the design process. Also notably, a chemical being evaluated in one area might demonstrate properties very attractive in another area and serendipity was the mechanism for solution. In contrast to such approaches, computer-aided molecular design (CAMD) looks to encompass both experimental and heuristic-based knowledge into a strategy that will design a molecule on a computer to meet a given target. Depending on the algorithm employed, the molecule which is designed might be quite novel (re: no CAS registration number) and/or non-intuitive relative to what is known about the problem at hand. While CAMD is a fairly recent strategy (dating to the early 1980s), it contains a variety of bottlenecks and limitations which have prevented the technique from garnering more attention in the academic, governmental and industrial institutions. A main reason for this is how the molecules are described in the computer. This step can control how models are developed for the properties of interest on a given problem as well as how to go from an output of the algorithm to ...
Date: April 1, 2010
Creator: Visco, Donald Patrick, Jr. (Tennessee Technological University, Cookeville, TN)
Partner: UNT Libraries Government Documents Department

Photo-control of nanointeractions.

Description: The manipulation of physical interactions between structural moieties on the molecular scale is a fundamental hurdle in the realization and operation of nanostructured materials and high surface area microsystem architectures. These include such nano-interaction-based phenomena as self-assembly, fluid flow, and interfacial tribology. The proposed research utilizes photosensitive molecular structures to tune such interactions reversibly. This new material strategy provides optical actuation of nano-interactions impacting behavior on both the nano- and macroscales and with potential to impact directed nanostructure formation, microfluidic rheology, and tribological control.
Date: February 1, 2005
Creator: Thomes, William Joseph, Jr.; Potter, Barrett George, Jr. (The University of Arizona, Tucson, AZ); Jiang, Liu; Long, Timothy Michael; Piech, Marcin; Jamison, Gregory Marks et al.
Partner: UNT Libraries Government Documents Department

Speciation of Heptavalent Technetium in Sulfuric Acid: Structural and Spectroscopic Studies.

Description: The speciation of Tc(VII) in 12 M sulfuric acid was studied by NMR, UV-visible and XAFS spectroscopy, experimental results were supported by DFT calculation and were in agreement with the formation of TcO{sub 3}OH(H{sub 2}O){sub 2}. In summary, the speciation of heptvalent technetium has been investigated in sulfuric acid. In 12 M H{sub 2}SO{sub 4}, a yellow solution is observed, and its {sup 99}Tc NMR spectrum is consistent with a heptavalent complex. The yellow solution was further characterized by EXAFS spectroscopy, and results are consistent with the formation of TcO{sub 3}(OH)(H{sub 2}O){sub 2}. No technetium heptoxide or sulfato- complexes were detected in these conditions. The molecular structure of TcO{sub 3}(OH)(H{sub 2}O){sub 2} has been optimized by DFT techniques, and the structural parameters are well in accordance with those found by XAFS spectroscopy. The experimental electronic spectra exhibit ligand-to-metal charge transfer transitions that have been assigned using TDDFT methods. Calculations demonstrate the theoretical electronic spectrum of TcO{sub 3}(OH)(H{sub 2}O){sub 2} to be in very good agreement with the experimental one. Recent experiments in 12 M H{sub 2}SO{sub 4} show the yellow solution to be very reactive in presence of reducing agents presumably forming low valent Tc species. Current spectroscopic works focus on the speciation of these species.
Date: June 10, 2010
Creator: Poineau, Frederic; Weck, Philippe F.; German, Konstantin; Maruk, Alesya; Kirakosyan, Gayane; Lukens, Wayne et al.
Partner: UNT Libraries Government Documents Department

ORGANIC GEOCHEMICAL STUDIES. I. MOLECULAR CRITERIA FOR HYDROCARBONGENESIS

Description: In recent years the search for life-forms at the earliest periods of geological time has been continued not only at the morphological level but also at the molecular level. This has been possible as a result of the increase in the biochemical knowledge and with the advent of analytical techniques that are capable of describing the intimate molecular architecture of individual molecules in acute detail. The fundamental premises upon which this organic geochemical approach rest are the following: that certain molecules, possessing a characteristic structural skeleton, show a reasonable stability to degradation over long periods of geological time; that their structural specificity can be understood in terms of known biosynthetic sequences; and that their formation by any non-biological means is of negligible probability. In this manuscript it is proposed to critically re-examine these premises and to establish criteria whereby one can differentiate molecules derived from biological systems from those that have their origin in non-biological processes. The importance of establishing such criteria lies in the significance these criteria have in determining whether life exists, or has existed, on other planets. Within the very near future it may be possible to provide an initial answer to this question when the first lunar samples are returned to the earth for analysis.
Date: September 22, 1967
Creator: McCarthy, Eugene D. & Calvin, Kevin
Partner: UNT Libraries Government Documents Department

IR DIAGNOSTICS FOR DYNAMIC FAILURE OF MATERIALS

Description: This project explores the thermodynamics of dynamic deformation and failure of materials using high-speed spatially-resolved infrared (IR) measurements of temperature. During deformation mechanical work is converted to different forms of energy depending on the deformation processes. For example, it can be dissipated as heat in purely plastic deformation, stored as strain energy in dislocations in metals and in oriented polymeric molecular structures, and expended during the generation of new surfaces during damage and fracture. The problem of how this work is converted into these various forms is not well understood. In fact, there exists a controversy for the relatively simple case regarding the amount of work dissipated as heat during uniform plastic deformation. The goals of this work are to develop dynamic IR temperature measurement techniques and then apply them to gain a better understanding of the dynamic failure processes in both metals and polymeric composite materials. The experimental results will be compared against predictions of existing constitutive models and guide the development of higher fidelity models if needed.
Date: February 13, 2006
Creator: McElfresh, M & DeTeresa, S
Partner: UNT Libraries Government Documents Department

Structural Consequences of Anionic Host-Cationic Guest Interactions in a Supramolecular Assembly

Description: The molecular structure of the self-assembled supramolecular assembly [M{sub 4}L{sub 6}]{sup 12-} has been explored with different metals (M = Ga{sup III}, Fe{sup III}, Ti{sup IV}) and different encapsulated guests (NEt{sub 4}{sup +}, BnNMe{sub 3}{sup +}, Cp{sub 2}Co{sup +}, Cp*{sub 2}Co{sup +}) by X-ray crystallography. While the identity of the metal ions at the vertices of the M{sub 4}L{sub 6} structure is found to have little effect on the assembly structure, encapsulated guests significantly distort the size and shape of the interior cavity of the assembly. Cations on the exterior of the assembly are found to interact with the assembly through either {pi}-{pi}, cation-{pi}, or CH-{pi} interactions. In some cases, the exterior guests interact with only one assembly, but cations with the ability to form multiple {pi}-{pi} interactions are able to interact with adjacent assemblies in the crystal lattice. The solvent accessible cavity of the assembly is modeled using the rolling probe method and found to range from 253-434 {angstrom}{sup 3}, depending on the encapsulated guest. Based on the volume of the guest and the volume of the cavity, the packing coefficient for each host-guest complex is found to range from 0.47-0.67.
Date: July 9, 2008
Creator: Pluth, Michael D.; Johnson, Darren W.; Szigethy, Geza; Davis, Anna V.; Teat, Simon J.; Oliver, Allen G. et al.
Partner: UNT Libraries Government Documents Department

Judging Edward Teller: A Closer Look at One of the Most Influential Scientists of the Twentieth Century

Description: Much has been written about Edward TEller, but little of it is objective. Given, on the one hand, his position as one of the most inventive theoretical physicists of the 20th century, and on the other, his central role in the development and advocacy of thermonuclear weapons, one might imagine it impossible at this point in history to write a scholarly, impartial account of Teller's life and his impact. Now, however, Istvan Hargittai, a prominent Hungarian physical chemist and historian of science, has written a balanced, thoughtful, and beautifully research biography that comes closest. Hargittai is uniquely qualified for this difficult task. Coming a generation and a half later from a similar Hungarian-Jewish background, Hargittai understands well the influences and terrible events that shaped Teller. The advent of virulent, political anti-Semitism, first in Hungary and then in Germany, made Teller twice a refugee. Both Teller and Hargittai lost close family in the Holocaust; Hargittai was himself liberated from a Nazi concentration camp as a child. While Teller was in the US by then, his and Hargittai's surviving family members in Hungary suffered mistreatment at the hands of the postwar Hungarian Communist dictatorship. Hargittai's informed Eastern European perspective also provides a fresh viewpoint to the cold war context of the second half of Teller's career. Furthermore, Hargittai's own scientific work in molecular structure clearly makes him appreciate of Teller's breakthroughs in that field in the 1930s.
Date: December 29, 2010
Creator: Libby, S B
Partner: UNT Libraries Government Documents Department

Defects in p-GaN and their atomic structure

Description: In this paper defects formed in p-doped GaN:Mg grown with Ga polarity will be discussed. The atomic structure of these characteristic defects (Mg-rich hexagonal pyramids and truncated pyramids) in bulk and thin GaN:Mg films grown with Ga polarity was determined at atomic resolution by direct reconstruction of the scattered electron wave in a transmission electron microscope. Small cavities were present inside the defects. The inside walls of the cavities were covered by GaN which grew with reverse polarity compared to the matrix. It was proposed that lateral overgrowth of the cavities restores matrix polarity on the defect base. Exchange of Ga and N sublattices within the defect compared to the matrix lead to a 0.6 {+-} 0.2 {angstrom} displacement between the Ga sublattices of these two areas. A [1{und 1}00]/3 shift with change from AB stacking in the matrix to BC within the entire pyramid is observed
Date: October 8, 2004
Creator: Liliental-Weber, Z.; Tomaszewicz, T.; Zakharov, D.; Jasinski, J. & and O'Keefe, M.
Partner: UNT Libraries Government Documents Department

Automated High Throughput Drug Target Crystallography

Description: The molecular structures of drug target proteins and receptors form the basis for 'rational' or structure guided drug design. The majority of target structures are experimentally determined by protein X-ray crystallography, which as evolved into a highly automated, high throughput drug discovery and screening tool. Process automation has accelerated tasks from parallel protein expression, fully automated crystallization, and rapid data collection to highly efficient structure determination methods. A thoroughly designed automation technology platform supported by a powerful informatics infrastructure forms the basis for optimal workflow implementation and the data mining and analysis tools to generate new leads from experimental protein drug target structures.
Date: February 18, 2005
Creator: Rupp, B
Partner: UNT Libraries Government Documents Department

Comparative Genomics and Evolution of Eukaryotic Phospholipid biosynthesis

Description: Phospholipid biosynthetic enzymes produce diverse molecular structures and are often present in multiple forms encoded by different genes. This work utilizes comparative genomics and phylogenetics for exploring the distribution, structure and evolution of phospholipid biosynthetic genes and pathways in 26 eukaryotic genomes. Although the basic structure of the pathways was formed early in eukaryotic evolution, the emerging picture indicates that individual enzyme families followed unique evolutionary courses. For example, choline and ethanolamine kinases and cytidylyltransferases emerged in ancestral eukaryotes, whereas, multiple forms of the corresponding phosphatidyltransferases evolved mainly in a lineage specific manner. Furthermore, several unicellular eukaryotes maintain bacterial-type enzymes and reactions for the synthesis of phosphatidylglycerol and cardiolipin. Also, base-exchange phosphatidylserine synthases are widespread and ancestral enzymes. The multiplicity of phospholipid biosynthetic enzymes has been largely generated by gene expansion in a lineage specific manner. Thus, these observations suggest that phospholipid biosynthesis has been an actively evolving system. Finally, comparative genomic analysis indicates the existence of novel phosphatidyltransferases and provides a candidate for the uncharacterized eukaryotic phosphatidylglycerol phosphate phosphatase.
Date: December 1, 2006
Creator: Lykidis, Athanasios
Partner: UNT Libraries Government Documents Department

Crystal and Molecular Structure of Hydridotis[bis(trimethylsilyl)amido]uranium(IV)

Description: New hydride derivatives of thorium (IV) and uranium (IV), HM[N(SiMe{sub 3}){sub 2}]{sub 3}, have recently been prepared. This paper describes the crystal structure of the uranium species, though the hydride-ion was not located, and shows that the thorium analogue is isostructural. The reaction chemistry and spectroscopy leave no doubt that these derivatives are authentic examples of four-coordinate, monomeric hydride, compounds.
Date: May 1, 1980
Creator: Andersen, Richard A.; Zalkin, Allen & Templeton, David H.
Partner: UNT Libraries Government Documents Department

Dynamical hierarchies - A summary

Description: This paper summarizes some of the problems associated with the generation of higher order emergent structures in formal dynamical systems. In biological systems, higher order hyperstructures occur both in an intuitive and a formal sense: monomers, polymers, membranes, organelles, cells, tissues, organs, etc. constitute an observable hierarchy, apparently generated by the underlying biomolecular process. However, in models and simulations of these systems, it has turned out to be quite difficult to produce higher order emergent structures from first principles. The first problem is to agree on what a higher order structure is. An emergent structure can be defined through an introduction of an observational function. If a property can be observed in the dynamics, but not at the level of the fundamental first order interacting structures, we define it to be emergent. It is well known that second order structures occur relatively easy in simulation, so the problem is how to proceed to third and higher order without external interference. A third order structure is defined through the interaction of second order structures forming a new observable not found at the lower levels.
Date: April 1, 1996
Creator: Rasmussen, S.; Barrett, C.L. & Olesen, M.W.
Partner: UNT Libraries Government Documents Department