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Full-Text Articles in Physical Sciences and Mathematics

An Adaptive Level Set Approach For Modeling Damage Due To Galvanic Corrosion, Joseph Wilder, Curtis Clemons, Dmitry Golovaty, Kevin Kreider, Gerald Young, R. Lillard Sep 2015

An Adaptive Level Set Approach For Modeling Damage Due To Galvanic Corrosion, Joseph Wilder, Curtis Clemons, Dmitry Golovaty, Kevin Kreider, Gerald Young, R. Lillard

Gerald W Young

This article presents an approach to solving problems related to galvanic corrosion that involve moving boundaries (due to preferential corrosion of one of the metals in the system). The method incorporates an adaptive (node based, finite difference) grid technique for the treatment of boundary-related singularities that arise in the calculation of the electric potential. Simulation of the time evolution of the damage done by the corroding interface is performed using of a level set formulation. An analysis of the convergence of the method and a comparison with experimental data from the literature are included.

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Global Magnetic Confinement For The 1.5d Vlasov-Maxwell System, Toan Nguyen, Truyen Nguyen, Walter Strauss Sep 2015

Global Magnetic Confinement For The 1.5d Vlasov-Maxwell System, Toan Nguyen, Truyen Nguyen, Walter Strauss

Truyen V. Nguyen

We establish the global-in-time existence and uniqueness of classical solutions to the ``one and one-half'' dimensional relativistic Vlasov--Maxwell systems in a bounded interval, subject to an external magnetic field which is infinitely large at the spatial boundary. We prove that the large external magnetic field confines the particles to a compact set away from the boundary. This excludes the known singularities that typically occur due to particles that repeatedly bounce off the boundary. In addition to the confinement, we follow the techniques introduced by Glassey and Schaeffer, who studied the Cauchy problem without boundaries.

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One-Dimensional Pressureless Gas Systems With/Without Viscosity, Truyen Nguyen, Adrian Tudorascu Sep 2015

One-Dimensional Pressureless Gas Systems With/Without Viscosity, Truyen Nguyen, Adrian Tudorascu

Truyen V. Nguyen

A general global existence result for one-dimensional pressureless Euler/Euler-Poisson systems with or without viscosity is obtained by employing the “sticky particles” model. We first construct entropy solutions for some appropriate scalar conservation laws, then we show that these solutions encode all the information necessary to obtain solutions for the pressureless systems. Another novel contribution is the stability and uniqueness of solutions, which is obtained via a contraction principle in the Wasserstein metric.

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One-Dimensional Approach To Modeling Damage Evolution In Galvanic Corrosion, Aaron Stenta, S. Basco, A. Smith, Curtis Clemons, Dimitry Golovaty, Kevin Kreider, Joseph Wilder, Gerald Young, Robert Lillard Sep 2015

One-Dimensional Approach To Modeling Damage Evolution In Galvanic Corrosion, Aaron Stenta, S. Basco, A. Smith, Curtis Clemons, Dimitry Golovaty, Kevin Kreider, Joseph Wilder, Gerald Young, Robert Lillard

Kevin L. Kreider

A one-dimensional mathematical model is developed to describe time-dependent damage evolution in well-mixed (spatially uniform species concentrations) galvanic systems using an IR drop approach. An asymptotic procedure taking advantage of disparity in length scales (thin film approximation for the electrolyte thickness) is used to derive the model. Limitations that result from the reduction of dimension are described, along with an analysis demonstrating the ability of the 1D model to capture physical phenomena, such as area ratio effects. Computed potential, current density, and corrosion damage profiles are compared and verified with experimental data available in the literature and 2D galvanic corrosion …

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An Adaptive Level Set Approach For Modeling Damage Due To Galvanic Corrosion, Joseph Wilder, Curtis Clemons, Dmitry Golovaty, Kevin Kreider, Gerald Young, R. Lillard Sep 2015

An Adaptive Level Set Approach For Modeling Damage Due To Galvanic Corrosion, Joseph Wilder, Curtis Clemons, Dmitry Golovaty, Kevin Kreider, Gerald Young, R. Lillard

Kevin L. Kreider

This article presents an approach to solving problems related to galvanic corrosion that involve moving boundaries (due to preferential corrosion of one of the metals in the system). The method incorporates an adaptive (node based, finite difference) grid technique for the treatment of boundary-related singularities that arise in the calculation of the electric potential. Simulation of the time evolution of the damage done by the corroding interface is performed using of a level set formulation. An analysis of the convergence of the method and a comparison with experimental data from the literature are included.

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Localized Corrosion Risk Assessment Using Markov Analysis, K Mccallum, J Zhao, M Workman, M Iannuzzi, M Kappes, Joe Payer, Curtis Clemons, S Chawla, Kevin Kreider, Nao Mimoto, Gerald Young Sep 2015

Localized Corrosion Risk Assessment Using Markov Analysis, K Mccallum, J Zhao, M Workman, M Iannuzzi, M Kappes, Joe Payer, Curtis Clemons, S Chawla, Kevin Kreider, Nao Mimoto, Gerald Young

Kevin L. Kreider

The objective of this work was to develop the foundation for an interactive corrosion risk management tool for assessing the probability of failure of equipment/infrastructure as a function of threats (such as pitting corrosion and coating degradation) and mitigation schemes (such as inhibitors and coatings). The application of this work was to assist with corrosion management and maintenance planning of equipment/infrastructure given dynamic changes in environmental conditions. Markov models are developed to estimate pitting damage accumulation density distributions as a function of input parameters for pit nucleation and growth rates. The input parameters are selected based upon characterization with experimental …

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One-Dimensional Approach To Modeling Damage Evolution In Galvanic Corrosion, Aaron Stenta, S. Basco, A. Smith, Curtis Clemons, Dimitry Golovaty, Kevin Kreider, Joseph Wilder, Gerald Young, Robert Lillard Sep 2015

One-Dimensional Approach To Modeling Damage Evolution In Galvanic Corrosion, Aaron Stenta, S. Basco, A. Smith, Curtis Clemons, Dimitry Golovaty, Kevin Kreider, Joseph Wilder, Gerald Young, Robert Lillard

Dimitry Golovaty

A one-dimensional mathematical model is developed to describe time-dependent damage evolution in well-mixed (spatially uniform species concentrations) galvanic systems using an IR drop approach. An asymptotic procedure taking advantage of disparity in length scales (thin film approximation for the electrolyte thickness) is used to derive the model. Limitations that result from the reduction of dimension are described, along with an analysis demonstrating the ability of the 1D model to capture physical phenomena, such as area ratio effects. Computed potential, current density, and corrosion damage profiles are compared and verified with experimental data available in the literature and 2D galvanic corrosion …

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On A Conjecture Of Gluck, James Cossey, Zoltan Halasi, Attila Maroti, Hung Nuguyen Sep 2015

On A Conjecture Of Gluck, James Cossey, Zoltan Halasi, Attila Maroti, Hung Nuguyen

James P. Cossey

Let F(G) and b(G) respectively denote the Fitting subgroup and the largest degree of an irreducible complex character of a finite group G. A well-known conjecture of D. Gluck claims that if G is solvable then |G:F(G)|≤b(G)2. We confirm this conjecture in the case where |F(G)| is coprime to 6. We also extend the problem to arbitrary finite groups and prove several results showing that the largest irreducible character degree of a finite group strongly controls the group structure.

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One-Dimensional Approach To Modeling Damage Evolution In Galvanic Corrosion, Aaron Stenta, S. Basco, A. Smith, Curtis Clemons, Dimitry Golovaty, Kevin Kreider, Joseph Wilder, Gerald Young, Robert Lillard Sep 2015

One-Dimensional Approach To Modeling Damage Evolution In Galvanic Corrosion, Aaron Stenta, S. Basco, A. Smith, Curtis Clemons, Dimitry Golovaty, Kevin Kreider, Joseph Wilder, Gerald Young, Robert Lillard

Curtis B. Clemons

A one-dimensional mathematical model is developed to describe time-dependent damage evolution in well-mixed (spatially uniform species concentrations) galvanic systems using an IR drop approach. An asymptotic procedure taking advantage of disparity in length scales (thin film approximation for the electrolyte thickness) is used to derive the model. Limitations that result from the reduction of dimension are described, along with an analysis demonstrating the ability of the 1D model to capture physical phenomena, such as area ratio effects. Computed potential, current density, and corrosion damage profiles are compared and verified with experimental data available in the literature and 2D galvanic corrosion …

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An Adaptive Level Set Approach For Modeling Damage Due To Galvanic Corrosion, Joseph Wilder, Curtis Clemons, Dmitry Golovaty, Kevin Kreider, Gerald Young, R. Lillard Sep 2015

An Adaptive Level Set Approach For Modeling Damage Due To Galvanic Corrosion, Joseph Wilder, Curtis Clemons, Dmitry Golovaty, Kevin Kreider, Gerald Young, R. Lillard

Curtis B. Clemons

This article presents an approach to solving problems related to galvanic corrosion that involve moving boundaries (due to preferential corrosion of one of the metals in the system). The method incorporates an adaptive (node based, finite difference) grid technique for the treatment of boundary-related singularities that arise in the calculation of the electric potential. Simulation of the time evolution of the damage done by the corroding interface is performed using of a level set formulation. An analysis of the convergence of the method and a comparison with experimental data from the literature are included.

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Localized Corrosion Risk Assessment Using Markov Analysis, K Mccallum, J Zhao, M Workman, M Iannuzzi, M Kappes, Joe Payer, Curtis Clemons, S Chawla, Kevin Kreider, Nao Mimoto, Gerald Young Sep 2015

Localized Corrosion Risk Assessment Using Markov Analysis, K Mccallum, J Zhao, M Workman, M Iannuzzi, M Kappes, Joe Payer, Curtis Clemons, S Chawla, Kevin Kreider, Nao Mimoto, Gerald Young

Curtis B. Clemons

The objective of this work was to develop the foundation for an interactive corrosion risk management tool for assessing the probability of failure of equipment/infrastructure as a function of threats (such as pitting corrosion and coating degradation) and mitigation schemes (such as inhibitors and coatings). The application of this work was to assist with corrosion management and maintenance planning of equipment/infrastructure given dynamic changes in environmental conditions. Markov models are developed to estimate pitting damage accumulation density distributions as a function of input parameters for pit nucleation and growth rates. The input parameters are selected based upon characterization with experimental …

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Localized Corrosion Risk Assessment Using Markov Analysis, K Mccallum, J Zhao, M Workman, M Iannuzzi, M Kappes, Joe Payer, Curtis Clemons, S Chawla, Kevin Kreider, Nao Mimoto, Gerald Young Sep 2015

Localized Corrosion Risk Assessment Using Markov Analysis, K Mccallum, J Zhao, M Workman, M Iannuzzi, M Kappes, Joe Payer, Curtis Clemons, S Chawla, Kevin Kreider, Nao Mimoto, Gerald Young

Nao Mimoto

The objective of this work was to develop the foundation for an interactive corrosion risk management tool for assessing the probability of failure of equipment/infrastructure as a function of threats (such as pitting corrosion and coating degradation) and mitigation schemes (such as inhibitors and coatings). The application of this work was to assist with corrosion management and maintenance planning of equipment/infrastructure given dynamic changes in environmental conditions. Markov models are developed to estimate pitting damage accumulation density distributions as a function of input parameters for pit nucleation and growth rates. The input parameters are selected based upon characterization with experimental …

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Topical Rapamycin Systematically Suppresses The Early Stages Of Pulsed Dye Laser-Induced Angiogenesis Pathways, Lin Gao, Sydney Phan, Dawnica Nadora, Margarita Chernova, Victor Sun, Salena Preciado, Brittany Ballew, Zhenyu Jia, Wangcun Jia, Gang Wang, Martin Mihm, J. Nelson, Wenbin Tan Sep 2015

Topical Rapamycin Systematically Suppresses The Early Stages Of Pulsed Dye Laser-Induced Angiogenesis Pathways, Lin Gao, Sydney Phan, Dawnica Nadora, Margarita Chernova, Victor Sun, Salena Preciado, Brittany Ballew, Zhenyu Jia, Wangcun Jia, Gang Wang, Martin Mihm, J. Nelson, Wenbin Tan

Zhenyu Jia

BACKGROUND: Administration of topical rapamycin (RPM) suppresses the regeneration and revascularization of photocoagulated blood vessels induced by pulsed dye laser (PDL). OBJECTIVE: To systematically elucidate the molecular pathophysiology of the inhibition of PDL-induced angiogenesis by topical RPM in a rodent model. METHODS: The mRNA expression profiles of 86 angiogenic genes and phosphorylation levels of ribosomal protein S6 kinase (P70S6K) in rodent skin were examined with or without topical RPM administration post-PDL exposure. RESULTS: The PDL-induced systematic increases in transcriptional levels of angiogenic genes showed a peak expression at days 3-7 post-PDL in rodent skin. Topical application of 1% RPM significantly …

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Transcultural Self-Efficacy Perceptions Of Baccalaureate Nursing Students, Margaret Halter, Faye Grund, Mark Fridline, Sharon See, Lisa Young, Carol Reece Sep 2015

Transcultural Self-Efficacy Perceptions Of Baccalaureate Nursing Students, Margaret Halter, Faye Grund, Mark Fridline, Sharon See, Lisa Young, Carol Reece

Mark Fridline PhD

Addressing the health care needs of a 21st-century nation that is experiencing increased diversity and disparity will require new models of educating future providers. The cultural competence and confidence model was the guiding framework in a study evaluating the influence of cultural educational offerings on the transcultural self-efficacy (TSE) perceptions in baccalaureate nursing students. The Transcultural Self-Efficacy Tool was used to measure perceived TSE in a pretest (N = 260), posttest (N = 236) study over an academic year. Significant changes were demonstrated in overall self-efficacy and on the cognitive, practical, and affective subscales. A classification and regression …

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Forecasting Climate Change Impacts On The Distribution Of Wetland Habitat In The Midwestern United States, Heath Garris, Randall Mitchell, Lauchlan Fraser, Linda Barrett Sep 2015

Forecasting Climate Change Impacts On The Distribution Of Wetland Habitat In The Midwestern United States, Heath Garris, Randall Mitchell, Lauchlan Fraser, Linda Barrett

Linda R. Barrett

Shifting precipitation patterns brought on by climate change threaten to alter the future distribution of wetlands. We developed a set of models to understand the role climate plays in determining wetland formation on a landscape scale and to forecast changes in wetland distribution for the Midwestern United States. These models combined 35 climate variables with 21 geographic and anthropogenic factors thought to encapsulate other major drivers of wetland distribution for the Midwest. All models successfully recreated a majority of the variation in current wetland area within the Midwest, and showed that wetland area was significantly associated with climate, even when …

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Controls On Trace Metal Authigenic Enrichment In Reducing Sediments: Insights From Modern Oxygen-Deficient Settings, Susan Little, Derek Vance, Timothy Lyons, James Mcmanus Sep 2015

Controls On Trace Metal Authigenic Enrichment In Reducing Sediments: Insights From Modern Oxygen-Deficient Settings, Susan Little, Derek Vance, Timothy Lyons, James Mcmanus

James McManus

Any effort to reconstruct Earth history using variations in authigenic enrichments of redox-sensitive and biogeochemically important trace metals must rest on a fundamental understanding of their modern oceanic and sedimentary geochemistry. Further, unravelling the multiple controls on sedimentary enrichments requires a multi-element approach. Of the range of metals studied, most is known about the behavior of Fe, Mn, and Mo. In this study, we compare the authigenic enrichment patterns of these elements with a group whose behavior is not as well defined (Cd, Cu, Zn, and Ni) in three oxygen-poor settings: the Black Sea, the Cariaco Basin (Venezuela), and the …

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The Sedimentary Flux Of Dissolved Rare Earth Elements To The Ocean, April Abbott, Brian Haley, James Mcmanus, Clare Reimers Sep 2015

The Sedimentary Flux Of Dissolved Rare Earth Elements To The Ocean, April Abbott, Brian Haley, James Mcmanus, Clare Reimers

James McManus

We determined pore fluid rare earth element (REE) concentrations in near-surface sediments retrieved from the continental margin off Oregon and California (USA). These sites represent shelf-to-slope settings, which lie above, within, and below the oxygen minimum zone of the Northeast Pacific. The sediments are characterized by varying degrees of net iron reduction, with pore fluids from the shelf sites being generally ferruginous, and the slope sediments having less-pronounced iron reduction zones that originate deeper in the sediment package. REE concentrations show maxima in shallow (upper 2–10 cm) subsurface pore fluids across all sites with concentrations that rise more than two …

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On The Isotope Composition Of Reactive Iron In Marine Sediments: Redox Shuttle Versus Early Diagenesis, Florian Shultz, Silke Severman, James Mcmanus, Anna Nofke, Ulrike Lomnitz, Christian Hensen Sep 2015

On The Isotope Composition Of Reactive Iron In Marine Sediments: Redox Shuttle Versus Early Diagenesis, Florian Shultz, Silke Severman, James Mcmanus, Anna Nofke, Ulrike Lomnitz, Christian Hensen

James McManus

The isotope composition of reactive iron (Fe) in marine sediments and sedimentary rocks is a promising tool for identifying Fe sources and sinks across ocean basins. In addition to cross-basinal Fe redistribution, which can modify Fe isotope signatures, Fe minerals also undergo diagenetic redistribution during burial. The isotope fractionation associated with this redistribution does not affect the bulk isotope composition, but complicates the identification of mineral- specific isotope signatures. Here, we present new Fe isotope data for Peru margin sediments and revisit previously published data for sediments from the California margin to unravel the impact of early diagenesis on Fe …

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Transitions Of Tethered Chain Molecules Under Tension, Jutta Luettmer-Strathmann, Kurt Binder Sep 2015

Transitions Of Tethered Chain Molecules Under Tension, Jutta Luettmer-Strathmann, Kurt Binder

Jutta Luettmer-Strathmann

An applied tension force changes the equilibrium conformations of a polymer chain tethered to a planar substrate and thus affects the adsorption transition as well as the coil-globule and crystallization transitions. Conversely, solvent quality and surface attraction are reflected in equilibrium force-extension curves that can be measured in experiments. To investigate these effects theoretically, we study tethered chains under tension with Wang-Landau simulations of a bond-fluctuation lattice model. Applying our model to pulling experiments on biological molecules we obtain a good description of experimental data in the intermediate force range, where universal features dominate and finite size effects are small. …

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Partition Function Zeros And Finite Size Scaling For Polymer Adsorption, Mark Taylor, Jutta Luettmer-Strathmann Sep 2015

Partition Function Zeros And Finite Size Scaling For Polymer Adsorption, Mark Taylor, Jutta Luettmer-Strathmann

Jutta Luettmer-Strathmann

The zeros of the canonical partition functions for a flexible polymer chain tethered to an attractive flat surface are computed for chains up to length N = 1536. We use a bond-fluctuation model for the polymer and obtain the density of states for the tethered chain by Wang-Landau sampling. The partition function zeros in the complex e(β)-plane are symmetric about the real axis and densest in a boundary region that has the shape of a nearly closed circle, centered at the origin, terminated by two flaring tails. This structure defines a root-free zone about the positive real axis and follows …

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Fate Of Quasiparticles In The Superconducting State, Sasa Dordevic, D. Van Der Marel, C. C. Homes Sep 2015

Fate Of Quasiparticles In The Superconducting State, Sasa Dordevic, D. Van Der Marel, C. C. Homes

Sasa V. Dordevic

Quasiparticle properties in the superconducting state are masked by the superfluid and are not directly accessible to infrared spectroscopy. We show how one can use a Kramers-Kronig transformation to separate the quasiparticle from superfluid response and extract intrinsic quasiparticle properties in the superconducting state. We also address the issue of a narrow quasiparticle peak observed in microwave measurements, and demonstrate how it can be combined with infrared measurements to obtain a unified picture of electrodynamic properties of cuprate superconductors.

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Dielectric Behavior Of 95.5% Pb(Zn1/3nb2/3)O-3-4.5% Pbtio3 Single Crystals Under Dc Bias From 12-550 K, Ang Chen, Zhi Yu Sep 2015

Dielectric Behavior Of 95.5% Pb(Zn1/3nb2/3)O-3-4.5% Pbtio3 Single Crystals Under Dc Bias From 12-550 K, Ang Chen, Zhi Yu

Ang Chen

This work reports a detailed study of the dielectric behavior of 95.5% Pb(Zn1/3Nb2/3)O-3 - 4.5% PbTiO3 (PZN-4.5PT) single crystals with and without dc bias. It is found that there are at least five sets of dielectric anomalies for PZN-4.5PT from 12K to 550K. There are two dielectric peaks, around 430K and 395K, which are referred to as cubic-tetragonal and tetragonal- rhombohedral phase transitions, respectively, above room temperature. Furthermore, a set of broad peaks around 350K (at 10kHz) that showed up under electric field of 10kV/cm might indicate the existence of a monoclinic distortion M-A phase.

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Adhesion And Friction Characteristics Of Carbon Nanotube Arrays, Alper Buldum Sep 2015

Adhesion And Friction Characteristics Of Carbon Nanotube Arrays, Alper Buldum

Alper Buldum

There has been a great deal of interest in understanding, design and fabrication of bio-mimetic and bio-inspired adhesives in recent years. In this paper we present theoretical investigations on adhesion, friction behaviors and characteristics of fibrillar arrays composed of noninteracting carbon nanotubes for bio-inspired dry adhesives. Contact, compression, subsequent pulling off and dry sliding friction simulations were performed. It is demonstrated that there are two different adhesion forces during pull off. Static friction force values are in between 40 and 60 N cm(-2) at different loads and they are significantly larger than the normal adhesion forces. Dynamic friction force and …

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Pentacene-Fused Diporphyrins, Lin Jiang, James Engle, Ross Zaenglein, Alex Matus, Christopher Ziegler, Hong Wang, Martin Stillman Sep 2015

Pentacene-Fused Diporphyrins, Lin Jiang, James Engle, Ross Zaenglein, Alex Matus, Christopher Ziegler, Hong Wang, Martin Stillman

Christopher J. Ziegler

In this work, we report the synthesis, spectroscopic characterization, and theoretical analysis of a linearly conjugated pentacene-fused porphyrin dimer and cross-conjugated quinone-fused dinaphtho[2,3]porphyrins. These multichromophoric systems display non-typical UV-visible absorptions of either porphyrins or pentacenes/quinones. UV-visible, emission and magnetic circular dichroism (MCD) spectroscopy suggest strong electronic interactions among the multichromophores in the system. DFT calculations revealed the delocalization of the HOMOs and LUMOs spanning the entire dimer and linker assembly. The pentacene-fused porphyrin dimer is significantly more stable than both the corresponding pentacene and the heptacene derivatives. The availability of these huge π-extended and electronically highly interactive multichromophoric systems promises …

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Combined Mcd/Dft/Tddft Study Of The Electronic Structure Of Axially Pyridine Coordinated Metallocorroles, Hannah Rhoda, Laura Crandall, G. Geier, Christopher Ziegler, Victor Nemykin Sep 2015

Combined Mcd/Dft/Tddft Study Of The Electronic Structure Of Axially Pyridine Coordinated Metallocorroles, Hannah Rhoda, Laura Crandall, G. Geier, Christopher Ziegler, Victor Nemykin

Christopher J. Ziegler

A series of metallocorroles were investigated by UV−vis and MCD spectroscopies to investigate similarities and differences in the electronic structure and spectroscopy of the closed- and open-shell metallocorroles. Similar to the free-base H3tpfc, inspection of the MCD Faraday B-terms for all of the macrocycles presented here revealed that a ΔHOMO < ΔLUMO condition is present for each complex, which results in an unusual sign-reversed sequence for π−π* transitions in their MCD spectra.

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Synthesis Of Dimeric Rhenium Phenylenediimine Conjugates, Christopher Ziegler, J Bass, C Bogdanowicz, R Herrick, A Hasheminasab Sep 2015

Synthesis Of Dimeric Rhenium Phenylenediimine Conjugates, Christopher Ziegler, J Bass, C Bogdanowicz, R Herrick, A Hasheminasab

Christopher J. Ziegler

No abstract provided.

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Improved Synthesis Of [Re(Co)(3)(H2o)(3)]Br And Its Derivatives, Gerard Kerins, Joshua Farrell, Richard Herrick, Christopher Ziegler Sep 2015

Improved Synthesis Of [Re(Co)(3)(H2o)(3)]Br And Its Derivatives, Gerard Kerins, Joshua Farrell, Richard Herrick, Christopher Ziegler

Christopher J. Ziegler

Rhenium has been studied at length as a non-radioactive chemical analog to Technetium, a popular diagnostic imaging agent employed in nuclear medicine and biology. This study details a new synthetic method for preparing [Re(CO)3(H2O)3]Br as well as multiple derivatives of this complex using tridentate ligands. Full synthetic details and characterization will be pre

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Enhanced Helical Folding Of Ortho-Phenylenes Through The Control Of Aromatic Stacking Interactions, Sanyo Mathew, Laura Crandall, Christopher Ziegler Sep 2015

Enhanced Helical Folding Of Ortho-Phenylenes Through The Control Of Aromatic Stacking Interactions, Sanyo Mathew, Laura Crandall, Christopher Ziegler

Christopher J. Ziegler

The ortho-phenylenes are a simple class of foldamers, with the formation of helices driven by offset aromatic stacking interactions parallel to the helical axis. For the majority of reported o-phenylene oligomers, the perfectly folded conformer comprises perhaps 50–75% of the total population. Given the hundreds or thousands of possible conformers for even short oligomers, this distribution represents a substantial bias toward the folded state. However, “next-generation” o-phenylenes with better folding properties are needed if these structures are to be exploited as functional units within more complex architectures. Here, we report several new series of o-phenylene oligomers, varying both the nature …

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Structure And Conformation Of The Medium-Sized Chlorophosphazene Rings, Bowers, David Bowers, Brian Wright, Vincenzo Scionti, Anthony Schultz, Matthew Panzner, Eric Twum, Lin-Lin Li, Bryan Katzenmeyer, Benjamin Thome, Peter Rinaldi, Chrys Wesdemiotis, Wiley Youngs, Claire Tessier Sep 2015

Structure And Conformation Of The Medium-Sized Chlorophosphazene Rings, Bowers, David Bowers, Brian Wright, Vincenzo Scionti, Anthony Schultz, Matthew Panzner, Eric Twum, Lin-Lin Li, Bryan Katzenmeyer, Benjamin Thome, Peter Rinaldi, Chrys Wesdemiotis, Wiley Youngs, Claire Tessier

Wiley J. Youngs

No abstract provided.

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Structure And Conformation Of Meso-2,4-Di(N-Carbazolyl)Pentane, Patrick Wagers, Wiley Youngs, Aditya Agrahari, Steven Schildcrout, John Masnovi Sep 2015

Structure And Conformation Of Meso-2,4-Di(N-Carbazolyl)Pentane, Patrick Wagers, Wiley Youngs, Aditya Agrahari, Steven Schildcrout, John Masnovi

Wiley J. Youngs

The stereochemistry of the title compound is established as meso. The carbazole groups have no parallel planar close contacts (π-type interactions), which differs from the packing found previously for terminal 1,n-di(N-carbazolyl)alkanes. Bond distances, bond angles, and torsion angles are compared with those calculated for the isolated molecule using M06-2X density functional theory, which is designed to model intramolecular dispersion effects. The results indicate that dispersion effects have a significant influence on the molecular conformation, although packing effects likely determine the magnitude of the puckering about one of the nitrogens (N1) and give a crystal conformation …

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