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Articles 1 - 19 of 19
Full-Text Articles in Physical Sciences and Mathematics
The Role Of Particle Surface Functionality And Microstructure Development In Isothermal And Non-Isothermal Crystallization Behavior Of Polyamide 6/Cellulose Nanocrystals Nanocomposites, Shahram Rahimi, Joshua U. Otaigbe
The Role Of Particle Surface Functionality And Microstructure Development In Isothermal And Non-Isothermal Crystallization Behavior Of Polyamide 6/Cellulose Nanocrystals Nanocomposites, Shahram Rahimi, Joshua U. Otaigbe
Faculty Publications
Polyamide 6 (PA6)/cellulose nanocrystal (CNC) and aminopropyl triethoxy silane (APS) - modified CNC nanocomposites were prepared by in situ anionic ring opening polymerization and subsequent melt extrusion. The morphological observation of these hybrid systems revealed that the non-modified nanocrystals developed a network-like fibrillar structure while the APS-modified CNCs were finely dispersed mostly as individual whiskers. The isothermal and non-isothermal crystallization kinetics was extensively studied with emphasis on the effects of CNC surface functionality and the subsequent microstructure development on crystallization behavior of these novel nanocomposite systems. The non-modified CNC particles with corresponding fibrillar microstructure were found significantly hinder the crystallization …
Block Ionomer Complexes Consisting Of Sirna And ARaft-Synthesized Hydrophilic-Block-Cationic Copolymers Ii: The Influence Of Cationic Block Charge Density On Gene Suppression, Keith Hampton Parsons, Andrew Christopher Holley, Gabrielle A. Munn, Alex S. Flynt, Charles L. Mccormick
Block Ionomer Complexes Consisting Of Sirna And ARaft-Synthesized Hydrophilic-Block-Cationic Copolymers Ii: The Influence Of Cationic Block Charge Density On Gene Suppression, Keith Hampton Parsons, Andrew Christopher Holley, Gabrielle A. Munn, Alex S. Flynt, Charles L. Mccormick
Faculty Publications
Block ionomer complex (BIC)–siRNA interactions and effectiveness in cell transfection are reported. Aqueous RAFT polymerization was used to prepare a series of hydrophilic-block-cationic copolymers in which the cationic block statistically incorporates increasing amounts of neutral, hydrophilic monomer such that the number of cationic groups remains unchanged but the cationic charge density is diluted along the polymer backbone. Reduced charge density decreases the electrostatic binding strength between copolymers and siRNA with the goal of improving siRNA release after targeted cellular delivery. However, lower binding strength resulted in decreased transfection and RNA interference pathway activation, leading to reduced gene knockdown. Enzymatic siRNA …
Dealloying Behavior Of Nico And Nicocu Thin Films, Benjamin Peecher, Jennifer R. Hampton
Dealloying Behavior Of Nico And Nicocu Thin Films, Benjamin Peecher, Jennifer R. Hampton
Faculty Publications
Porous metals and alloys, such as those fabricated via electrochemical dealloying, are of interest for a variety of energy applications, ranging from their potential for enhanced catalytic behavior to their use as high surface area supports for pseudocapacitor materials. Here, the electrochemical dealloying process was explored for electrodeposited binary NiCo and ternary NiCoCu thin films. For each of the four different metal ratios, films were dealloyed using linear sweep voltammetry to various potentials in order to gain insight into the evolution of the film over the course of the linear sweep. Electrochemical capacitance, scanning electron microscopy, and energy dispersive X-ray …
A New Class Of Allosteric Hiv-1 Integrase Inhibitors Identified By Crstallographic Fragment Screening Of The Catalytic Core Domain, Disha Patel, Janet Antwi, Pratibha C. Koneru, Erik Serrao, Stefano Forli, Jacques J. Kessl, Lei Feng, Nanjie Deng, Ronald M. Levy, James R. Fuchs, Arthur J. Olson, Alan N. Engelman, Joseph D. Bauman, Mamuka Kvaratskhelia, Eddy Arnold
A New Class Of Allosteric Hiv-1 Integrase Inhibitors Identified By Crstallographic Fragment Screening Of The Catalytic Core Domain, Disha Patel, Janet Antwi, Pratibha C. Koneru, Erik Serrao, Stefano Forli, Jacques J. Kessl, Lei Feng, Nanjie Deng, Ronald M. Levy, James R. Fuchs, Arthur J. Olson, Alan N. Engelman, Joseph D. Bauman, Mamuka Kvaratskhelia, Eddy Arnold
Faculty Publications
HIV-1 integrase (IN) is essential for virus replication and represents an important multifunctional therapeutic target. Recently discovered quinoline-based allosteric IN inhibitors (ALLINIs) potently impair HIV-1 replication and are currently in clinical trials. ALLINIs exhibit a multimodal mechanism of action by inducing aberrant IN multimerization during virion morphogenesis and by competing with IN for binding to its cognate cellular cofactor LEDGF/p75 during early steps of HIV-1 infection. However, quinoline-based ALLINIs impose a low genetic barrier for the evolution of resistant phenotypes, which highlights a need for discovery of second-generation inhibitors. Using crystallographic screening of a library of 971 fragments against the …
Fulleretic Well-Defined Scaffolds: Donor–Fullerene Alignment Through Metal Coordination And Its Effect On Photophysics, Derek E. Williams, Ekaterina A. Dolgopolova, Danielle C. Godfrey, Evgeniya D. Ermolaeva, Perry J. Pellechia Dr., Andrew B. Greytak Prof. Dr., Mark Smith Dr., Stanislav M. Avdoshenko, Dr., Alexey A. Popov Dr., Natalia B. Shustova Prof. Dr.
Fulleretic Well-Defined Scaffolds: Donor–Fullerene Alignment Through Metal Coordination And Its Effect On Photophysics, Derek E. Williams, Ekaterina A. Dolgopolova, Danielle C. Godfrey, Evgeniya D. Ermolaeva, Perry J. Pellechia Dr., Andrew B. Greytak Prof. Dr., Mark Smith Dr., Stanislav M. Avdoshenko, Dr., Alexey A. Popov Dr., Natalia B. Shustova Prof. Dr.
Faculty Publications
Herein, we report the first example of a crystalline metal–donor–fullerene framework, in which control of the donor–fullerene mutual orientation was achieved through chemical bond formation, in particular, by metal coordination. The 13C cross-polarization magic-angle spinning NMR spectroscopy, X-ray diffraction, and time-resolved fluorescence spectroscopy were performed for comprehensive structural analysis and energy-transfer (ET) studies of the fulleretic donor–acceptor scaffold. Furthermore, in combination with photoluminescence measurements, the theoretical calculations of the spectral overlap function, Förster radius, excitation energies, and band structure were employed to elucidate the photophysical and ET processes in the prepared fulleretic material. We envision that the well-defined fulleretic donor–acceptor …
C60 And Sc3N@C80(Tmb-Ppo) Derivatives As Constituents Of Singlet Oxygen Generating, Thiol-Ene Polymer Nanocomposites, Emily M. Barker, Ashli R. Toles, Kyle A. Guess, J. Paige Buchanan
C60 And Sc3N@C80(Tmb-Ppo) Derivatives As Constituents Of Singlet Oxygen Generating, Thiol-Ene Polymer Nanocomposites, Emily M. Barker, Ashli R. Toles, Kyle A. Guess, J. Paige Buchanan
Faculty Publications
Numerous functionalization methods have been employed to increase the solubility, and therefore, the processability of fullerenes in composite structures, and of these radical addition reactions continue to be an important methodology. C60 and Sc3N@C80 derivatives were prepared via radical addition of the photodecomposition products from the commercial photoinitiator TMB-PPO, yielding C60(TMB-PPO)5 and Sc3N@C80(TMB-PPO)3 as preferred soluble derivatives obtained in high yields. Characterization of the mixture of isomers using standard techniques suggests an overall 1PPO:6TMB ratio of addends, reflecting the increased reactivity of the carbon radical. Although, a higher …
Predictive Coupled-Cluster Isomer Orderings For Some SiNCM (M, N ≤ 12) Clusters: A Pragmatic Comparison Between Dft And Complete Basis Limit Coupled-Cluster Benchmarks, Jason N. Byrd, Jesse J. Lutz, Duminda S. Ranasinghe, Yifan Jin, Ajith Perera, Xiaofeng F. Duan, Larry W. Burggraf, John A. Montgomery Jr.
Predictive Coupled-Cluster Isomer Orderings For Some SiNCM (M, N ≤ 12) Clusters: A Pragmatic Comparison Between Dft And Complete Basis Limit Coupled-Cluster Benchmarks, Jason N. Byrd, Jesse J. Lutz, Duminda S. Ranasinghe, Yifan Jin, Ajith Perera, Xiaofeng F. Duan, Larry W. Burggraf, John A. Montgomery Jr.
Faculty Publications
The accurate determination of the preferred Si12C12 isomer is important to guide experimental efforts directed towards synthesizing SiC nano-wires and related polymer structures which are anticipated to be highly efficient exciton materials for opto-electronic devices. In order to definitively identify preferred isomeric structures for silicon carbon nano-clusters, highly accurate geometries, energies and harmonic zero point energies have been computed using coupled-cluster theory with systematic extrapolation to the complete basis limit for set of silicon carbon clusters ranging in size from SiC3 to Si12C12. It is found that post-MBPT(2) correlation energy plays a …
Crystal Structure Of Di-Aqua-Bis-(7-Di-Ehtyl-Amino-3-Formyl-2-Oxo-2h-Chromen-4-Olato-Κ(2) O (3), O (4))Zinc(Ii) Dimethyl Sulfoxide Disolvate, Aaron B. Davis, Frank R. Fronczek, Karl J. Wallace
Crystal Structure Of Di-Aqua-Bis-(7-Di-Ehtyl-Amino-3-Formyl-2-Oxo-2h-Chromen-4-Olato-Κ(2) O (3), O (4))Zinc(Ii) Dimethyl Sulfoxide Disolvate, Aaron B. Davis, Frank R. Fronczek, Karl J. Wallace
Faculty Publications
The structure of the title coordination complex, [Zn(C14H14NO4)2(H2O)2]·2C2H6OS, shows that the ZnII cation adopts an octahedral geometry and lies on an inversion center. Two organic ligands occupy the equatorial positions of the coordination sphere, forming a chelate ring motif via the O atom on the formyl group and another O atom of the carbonyl group (a pseudo--diketone motif). Two water molecules occupy the remaining coordination sites of the ZnII cation in the axial positions. The water molecules are each hydrogen bonded to …
Wrinkled1 Rescues Feedback Inhibition Of Fatty Acid Synthesis In Hydroxylase-Expressing Seeds, Neil D. Adhikari, Philip D. Bates, John Browse
Wrinkled1 Rescues Feedback Inhibition Of Fatty Acid Synthesis In Hydroxylase-Expressing Seeds, Neil D. Adhikari, Philip D. Bates, John Browse
Faculty Publications
Previous attempts at engineering Arabidopsis (Arabidopsis thaliana) to produce seed oils containing hydroxy fatty acids (HFA) have resulted in low yields of HFA compared with the native castor (Ricinus communis) plant and caused undesirable effects, including reduced total oil content. Recent studies have led to an understanding of problems involved in the accumulation of HFA in oils of transgenic plants, which include metabolic bottlenecks and a decrease in the rate of fatty acid synthesis. Focusing on engineering the triacylglycerol assembly mechanisms led to modest increases in the HFA content of seed oil, but much room for …
Characteristic Length Scales Of The Secondary Relaxations In Glass-Forming Glycerol, Sudipta Gupta, Eugene Mamontov, Niina Jalarvo, Laura Stingaciu, Michael Ohl
Characteristic Length Scales Of The Secondary Relaxations In Glass-Forming Glycerol, Sudipta Gupta, Eugene Mamontov, Niina Jalarvo, Laura Stingaciu, Michael Ohl
Faculty Publications
We investigate the secondary relaxations and their link to the main structural relaxation in glass-forming liquids using glycerol as a model system. We analyze the incoherent neutron scattering signal dependence on the scattering momentum transfer, Q , in order to obtain the characteristic length scale for different secondary relaxations. Such a capability of neutron scattering makes it somewhat unique and highly complementary to the traditional techniques of glass physics, such as light scattering and broadband dielectric spectroscopy, which provide information on the time scale, but not the length scales, of relaxation processes. The choice of suitable neutron scattering techniques depends …
Polymer Chain Dynamics In Epoxy Based Composites As Investigated By Broadband Dielectric Spectroscopy, Mohammad K. Hassan, Samuel James Tucker, Ahmed Abukmail, Jeffrey S. Wiggins, Kenneth A. Mauritz
Polymer Chain Dynamics In Epoxy Based Composites As Investigated By Broadband Dielectric Spectroscopy, Mohammad K. Hassan, Samuel James Tucker, Ahmed Abukmail, Jeffrey S. Wiggins, Kenneth A. Mauritz
Faculty Publications
Epoxy networks of the diglycidyl ether of bisphenol A (DGEBA) were prepared using 3,3′- and 4,4′-diaminodiphenyl sulfone isomer crosslinkers. Secondary relaxations and the glass transitions of resultant networks were probed using broadband dielectric spectroscopy (BDS). A sub-Tg γ relaxation peak for both networks shifts to higher frequencies (f) with increasing temperature in Arrhenius fashion, both processes having the same activation energy and being assigned to phenyl ring flipping in DGEBA chains. A β relaxation is assigned to local motions of dipoles that were created during crosslinking reactions. 4,4′-based networks exhibited higher Tg relative to 3,3′-based …
Molecular Scale Cure Rate Dependence Of Thermoset Matrix Polymers, Christopher Harold Childers, Mohammad K. Hassan, Kenneth A. Mauritz, Jeffrey S. Wiggins
Molecular Scale Cure Rate Dependence Of Thermoset Matrix Polymers, Christopher Harold Childers, Mohammad K. Hassan, Kenneth A. Mauritz, Jeffrey S. Wiggins
Faculty Publications
This manuscript demonstrates the molecular scale cure rate dependence of di-functional epoxide based thermoset polymers cured with amines. A series of cure heating ramp rates were used to determine the influence of ramp rate on the glass transition temperature (Tg) and sub-Tg transitions and the average free volume hole size in these systems. The networks were comprised of 3,3′-diaminodiphenyl sulfone (33DDS) and diglycidyl ether of bisphenol F (DGEBF) and were cured at ramp rates ranging from 0.5 to 20 °C/min. Differential scanning calorimetry (DSC) and NIR spectroscopy were used to explore the cure ramp rate dependence of the polymer network …
Determination Of Hexavalent Chromium (Cr(Vi)) Concentrations Via Ion Chromatography And Uv-Vis Spectrophotometry In Samples Collected From Nacogdoches Wastewater Treatment Plant, East Texas (Usa), Kefa Karimu Onchoke, Salomey A. Sasu
Determination Of Hexavalent Chromium (Cr(Vi)) Concentrations Via Ion Chromatography And Uv-Vis Spectrophotometry In Samples Collected From Nacogdoches Wastewater Treatment Plant, East Texas (Usa), Kefa Karimu Onchoke, Salomey A. Sasu
Faculty Publications
The concentration of hexavalent chromium (Cr(VI)), a toxic environmental pollutant and carcinogen, was determined in samples collected from Nacogdoches Wastewater Treatment Plant (NWWTP) using ion chromatography and UV-visible spectrophotometry (IC, UV-Vis). On reaction with 1,5-diphenylcarbazide (DPC) Cr+6 forms a 1,5-diphenylcarbazide-Cr(VI) complex, which is then analyzed at 530nm and 540nm, respectively. Via ion chromatography Cr(VI) concentrations were in the range of 0.00190 ± 0.0020 and 0.0010 ± 0.0006ppm at the influent and effluent, respectively. With the use of standard addition wastewater samples were spiked with a 0.5ppm Cr(VI) standard of various amounts and subsequently analyzed with UV-Vis spectrophotometry. The spiked concentrations …
Water Soluble Cationic Porphyrin Sensor For Detection Of Hg2+, Pb2+, Cd2+, And Cu2+, Matibur Zamadar, Christopher Orr, Miranda Uherek
Water Soluble Cationic Porphyrin Sensor For Detection Of Hg2+, Pb2+, Cd2+, And Cu2+, Matibur Zamadar, Christopher Orr, Miranda Uherek
Faculty Publications
Here we report the sensing properties of the aqueous solution of meso-tetra(N-methyl-4-pyridyl)porphine tetrachloride (1) for simultaneous detection of toxic metal ions by using UV-vis spectroscopy. Cationic porphyrin 1 displayed different electronic absorptions in UV-vis region upon interacting with Hg2+, Pb2+, Cd2+, and Cu2+ ions in neutral water solution at room temperature. Quite interestingly, the porphyrin 1 showed that it can function as a single optical chemical sensor and/or metal ion receptor capable of detecting two or more toxic metal ions, particularly Hg2+, Pb2+, and Cd2+ ions coexisting in a water sample. Porphyrin 1 in an aqueous solution provides a unique …
"High-Valent Copper In Biomimetic And Biological Oxidations", J. Brannon Gary
"High-Valent Copper In Biomimetic And Biological Oxidations", J. Brannon Gary
Faculty Publications
A long-standing debate in the Cu-O2 field has revolved around the relevance of the Cu(III) oxidation state in biological redox processes. The proposal of Cu(III) in biology is generally challenged as no spectroscopic or structural evidence exists currently for its presence. The reaction of synthetic Cu(I) complexes with O2 at low temperature in aprotic solvents provides the opportunity to investigate and define the chemical landscape of Cu-O2 species at a small molecule level of detail; eight different types are characterized structurally, three of which contain at least one Cu(III) center. Simple imidazole or histamine ligands are competent in these oxygenation …
Calculating Heat Of Formation Values Of Energetic Compounds: A Comparative Study, Michael S. Elioff, Jordon Hoy, John A. Bumpus
Calculating Heat Of Formation Values Of Energetic Compounds: A Comparative Study, Michael S. Elioff, Jordon Hoy, John A. Bumpus
Faculty Publications
Heat of formation is one of several important parameters used to assess the performance of energetic compounds. We evaluated the ability of six different methods to accurately calculate gas-phase heat of formation (Δ 𝑓𝐻𝑜 298,g) values for a test set of 45 nitrogencontaining energetic compounds. Density functional theory coupled with the use of isodesmic or other balanced equations yielded calculated results in which 82% (37 of 45) of the Δ 𝑓𝐻𝑜 298,g values were within ±2.0 kcal/mol of the most recently recommended experimental/reference values available. This was compared to a procedure using density functional theory …
Physical And Electrochemical Area Determination Of Electrodeposited Ni, Co, And Nico Thin Films, Matthew Gira, Kevin Tkacz, Jennifer R. Hampton
Physical And Electrochemical Area Determination Of Electrodeposited Ni, Co, And Nico Thin Films, Matthew Gira, Kevin Tkacz, Jennifer R. Hampton
Faculty Publications
The surface area of electrodeposited thin films of Ni, Co, and NiCo was evaluated using electrochemical double-layer capacitance, electrochemical area measurements using the [Ru(NH3)6]3+/[Ru(NH3)6]2+ redox couple, and topographic atomic force microscopy (AFM) imaging. These three methods were compared to each other for each composition separately and for the entire set of samples regardless of composition. Double-layer capacitance measurements were found to be positively correlated to the roughness factors determined by AFM topography. Electrochemical area measurements were found to be less correlated with measured roughness factors as well as applicable …
Decarbonylative Cross Coupling Of Phthalimides With Diorganozinc Reagents—Efforts Toward Catalysis, Kimberly S. Deglopper, Sarah K. Fodor, Thomas Bd Endean, Jeffrey B. Johnson
Decarbonylative Cross Coupling Of Phthalimides With Diorganozinc Reagents—Efforts Toward Catalysis, Kimberly S. Deglopper, Sarah K. Fodor, Thomas Bd Endean, Jeffrey B. Johnson
Faculty Publications
The decarbonylative coupling of phthalimides with diorganozinc reagents to form o-substituted benzamides has been previously demonstrated as a viable process, but only with stoichiometric nickel(0). Investigations into a number of reaction variables, including solvent, ligand, and substrate substitution, have yielded multiple sets of conditions capable of achieving up to 10 catalyst turnovers, most successfully with the use of electron withdrawing nitrogen substituents on the phthalimide. In addition, these investigations have provided insight into the intermediates within the catalytic cycle and have revealed new approaches to the development of a general catalytic methodology.
Preface, Desmond H. Murray