Chemistry Commons^™

Elemental Mixing State Of Aerosol Particles Collected In Central Amazonia During Goamazon2014/15, Matthew Fraund, Don Q. Pham, Daniel Bonanno, Tristan H. Harder, Bingbing Wang, Joel Brito, Suzane S. De Sa, Samara Carbone, Swarup China, Paulo Artaxo, Scot T. Martin, Christopher Pöhlker, Meinrat O. Andreae, Alexander Laskin, Mary K. Gilles, Ryan C. Moffet

Department of Chemistry Student Articles

Two complementary techniques, Scanning Transmission X-ray Microscopy/Near Edge Fine Structure spectroscopy (STXM/NEXAFS) and Scanning Electron Microscopy/Energy Dispersive X-ray spectroscopy (SEM/EDX), have been quantitatively combined to characterize individual atmospheric particles. This pair of techniques was applied to particle samples at three sampling sites (ATTO, ZF2, and T3) in the Amazon basin as part of the Observations and Modeling of the Green Ocean Amazon (GoAmazon2014/5) field campaign during the dry season of 2014. The combined data was subjected to k-means clustering using mass fractions of the following elements: C, N, O, Na, Mg, P, S, Cl, K ...

Avoiding The Cubic Equation In Finding The Van Der Waals Fluid's Vapor Pressures, Carl W. David

Chemistry Education Materials

The van der Waals coexistence curve of liquid and vapor volumes as functions of the temperature (all in reduced coordinates) as well as the correspponding vapor pressures at these temperatures, is obtained using SageMath, a symbolic calculus/algebra computer programming language.The lack of correspondence of the coexistence locus’ analytical form as obtained herein and those of Lekner remains disconcerting.

Hybrid Approaches To Structural Characterization Of Conformational Ensembles Of Complex Macromolecular Systems Combining Nmr Residual Dipolar Couplings And Solution X‑Ray Scattering, Vincenzo Venditti, Timothy K. Egnert, G. Marius Clore

Vincenzo Venditti

Solving structures or structural ensembles of large macromolecular systems in solution poses a challenging problem. While NMR provides structural information at atomic resolution, increased spectral complexity, chemical shift overlap, and short transverse relaxation times (associated with slow tumbling) render application of the usual techniques that have been so successful for medium sized systems (<50 >kDa) difficult. Solution X-ray scattering, on the other hand, is not limited by molecular weight but only provides low resolution structural information related to the overall shape and size of the system under investigation. Here we review how combining atomic resolution structures of smaller domains with sparse ...

Dynamic Equilibrium Between Closed And Partially Closed States Of The Bacterial Enzyme I Unveiled By Solution Nmr And X-Ray Scattering, Vincenzo Venditti, Charles D. Schwieters, Alexander Grishaev, G. Marius Clore

Vincenzo Venditti

Abstract Enzyme I (EI) is the first component in the bacterial phosphotransferase system, a signal transduction pathway in which phosphoryl transfer through a series of bimolecular protein–protein interactions is coupled to sugar transport across the membrane. EI is a multidomain, 128-kDa homodimer that has been shown to exist in two conformational states related to one another by two large (50–90°) rigid body domain reorientations. The open conformation of apo EI allows phosphoryl transfer from His189 located in the N-terminal domain α/β (EINα/β) subdomain to the downstream protein partner bound to the EINα subdomain. The closed conformation ...

Surface Hydrophobicity And Acidity Effect On Alumina Catalyst In Catalytic Methanol Dehydration Reaction, Ahmed Osman

Ahmed Osman

Deactivation Of Ceria Supported Palladium Through C–C Scission During Transfer Hydrogenation Of Phenol With Alcohols, Nicholas C. Nelson, Juan Sebastian Manzano, Igor I. Slowing

Igor I. Slowing

The stability of palladium supported on ceria (Pd/CeO₂) was studied during liquid flow transfer hydrogenation using primary and secondary alcohols as hydrogen donors. For primary alcohols, the ceria support was reduced to cerium hydroxy carbonate within 14 h and was a contributing factor toward catalyst deactivation. For secondary alcohols, cerium hydroxy carbonate was not observed during the same time period and the catalyst was stable upon prolonged reaction. Regeneration through oxidation/reduction does not restore initial activity likely due to irreversible catalyst restructuring. A deactivation mechanism involving C–C scission of acyl and carboxylate intermediates is proposed

Probing Surface Hydrogen Bonding And Dynamics By Natural Abundance, Multidimensional, 17o Dnp-Nmr Spectroscopy, Frédéric A. Perras, Umesh Chaudhary, Igor I. Slowing, Marek Pruski

Igor I. Slowing

Dynamic nuclear polarization (DNP)-enhanced solid-state nuclear magnetic resonance (SSNMR) spectroscopy is increasingly being used as a tool for the atomic-level characterization of surface sites. DNP surface-enhanced SSNMR spectroscopy of materials has, however, been limited to studying relatively receptive nuclei, and the particularly rare 17O nuclide, which is of great interest for materials science, has not been utilized. We demonstrate that advanced 17O SSNMR experiments can be performed on surface species at natural isotopic abundance using DNP. We use 17O DNP surface-enhanced 2D SSNMR to measure 17O{1H} HETCOR spectra as well as dipolar oscillations on a series of thermally ...

Ionic Liquid‐Assisted Microwave Synthesis Of Solid Solutions Of Perovskite Sr1‐Xbaxsno3 For Photocatalytic Applications, Tarek Alammar, Igor Slowing, Jim Anderegg, Anja Mudring

Igor I. Slowing

Nanocrystalline Sr1−xBaxSnO3 (x=0, 0.2, 0.4, 0.8, 1) perovskite photocatalysts were prepared by microwave synthesis in an ionic liquid (IL) and subsequent heat-treatment. The influence of the Sr/Ba substitution on the structure, crystallization, morphology, and photocatalytic efficiency was investigated and the samples were fully characterized. On the basis of X-ray diffraction results, as the Ba content in the SrSnO3 lattice increases, a symmetry increase was observed from the orthorhombic perovskite structure for SrSnO3 to the cubic BaSnO3 structure. The analysis of the sample morphology by SEM reveals that the Sr1−xBaxSnO3 samples favor the formation ...

Ion Trap Mass Analyzer Apparatus, Methods, And Systems Utilizing One Or More Multiple Potential Ion Guide (Mpig) Electrodes, Curtiss Dwight Hanson

Curtiss D. Hanson

In one aspect of the invention, an ion trap mass analyzer includes a variable- or multi-potential type ion guide (MPIG) assembly which has been pre-configured to produce a parabolic-type potential field. Each MPIG electrode has a resistive coating of designed characteristics. In one example the coating varies in thickness along the length of an underlying uniform substrate. The MPIG assembly can be a single MPIG electrode or an array of a plurality of MPIG electrodes. An array can facilitate delocalization for improved performance. This chemical modification of a uniform underlying substrate promotes cheaper and flexible instruments. The modified MPIG electrodes ...

Optimizing Synthesis Of Substituted Oxadiazole Based Liquid Crystal Compounds.Pptx, Blake Bordokas

Blake Bordokas

Stereospecific Electrophilic Fluorination Of Alkylcarbastannatrane Reagents, Xinghua Ma

All Graduate Works by Year: Dissertations, Theses, and Capstone Projects

The introduction of fluorine atoms into organic molecules significantly changes their physical, chemical, and biological properties. Fluorinated organic compounds are used as pharmaceuticals, agrochemicals, materials, and tracers for positron emission tomography (PET). For example, the site-specific fluorination of drugs can block sites of phase I metabolism by cytochrome P450 enzymes as well as improve target-binding affinities. In view of the unique features of fluorine-containing compounds, there has been increasing interest in the development of novel methods for the synthesis of fluorinated molecules, especially the site-specific monofluorination of complex molecules. Herein, we present the enantiospecific conversion of chiral secondary alkylcarbastannatranes into ...

Heterojunction Engineering For Next Generation Hybrid Ii-Vi Materials, Thor Garcia

All Graduate Works by Year: Dissertations, Theses, and Capstone Projects

Molecular Beam Epitaxy(MBE) is a versatile thin film growth technique with monolayer control of crystallization. The flexibility and precision afforded by the technique allows for unique control of interfaces and electronic structure of the films grown. This facilitates the realization of novel devices and structures within a research environment normally only achieved though complex industrial processes. In the past, the control of each interface in MBE has been explored to great benefit. In this work, we study the control of these interfaces so as to increase the performance of novel devices material systems. This dissertation focuses on two main ...

Cyanobacterial Toxins As Allelochemicals With Potential Applications As Algaecides, Herbicides And Insecticides, John P. Berry, Miroslav Gantar, Mario H. Perez, Gerald Berry, Fernando G. Noriega

Fernando Noriega

Cyanobacteria (“blue-green algae”) from marine and freshwater habitats are known to produce a diverse array of toxic or otherwise bioactive metabolites. However, the functional role of the vast majority of these compounds, particularly in terms of the physiology and ecology of the cyanobacteria that produce them, remains largely unknown. A limited number of studies have suggested that some of the compounds may have ecological roles as allelochemicals, specifically including compounds that may inhibit competing sympatric macrophytes, algae and microbes. These allelochemicals may also play a role in defense against potential predators and grazers, particularly aquatic invertebrates and their larvae. This ...

Evaluation Of Coarse-Grained Mapping Schemes For Polysaccharide Chains In Cellulose, Sergiy Markutsya, Ajitha Devarajan, John Y. Baluyut, Theresa Lynn Windus, Mark S. Gordon, Monica H. Lamm

Monica H. Lamm

A fundamental understanding of the intermolecular forces that bind polysaccharide chains together in cellulose is crucial for designing efficient methods to overcome the recalcitrance of lignocellulosic biomass to hydrolysis. Because the characteristic time and length scales for the degradation of cellulose by enzymatic hydrolysis or chemical pretreatment span orders of magnitude, it is important to closely integrate the molecular models used at each scale so that, ultimately, one may switch seamlessly between quantum, atomistic, and coarse-grained descriptions of the system. As a step towards that goal, four multiscale coarse-grained modelsfor polysaccharide chains in a cellulose-Iα microfiber are considered. Using the ...

Ab Initio Study Of Molecular Interactions In Cellulose Iα, Ajitha Devarajan, Sergiy Markutsya, Monica H. Lamm, Xiaolin Cheng, Jeremy C. Smith, John Ysrael Baluyut, Yana Kholod, Mark S. Gordon, Theresa Lynn Windus

Monica H. Lamm

Biomass recalcitrance, the resistance of cellulosic biomass to degradation, is due in part to the stability of the hydrogen bond network and stacking forces between the polysaccharide chains in cellulose microfibers. The fragment molecular orbital (FMO) method at the correlated Møller–Plesset second order perturbation level of theory was used on a model of the crystalline cellulose Iα core with a total of 144 glucose units. These computations show that the intersheet chain interactions are stronger than the intrasheet chain interactions for the crystalline structure, while they are more similar to each other for a relaxed structure. An FMO chain ...

Modification Of An Implant Material, Emily Leung, Nina A. Reger, Ashley Blystone, Ellen S. Gawalt Phd

Undergraduate Research and Scholarship Symposium

Titanium metal is a commonly used implant material which can be colonized by bacteria. Biofilms are formed when bacteria colonizes, attaches to a surface, and immobilizes. Bacterial infections or biofilms are hard to treat once formed on the surface of a metal implant. Coating the material may minimize bacteria attachment. Self-assembled monolayers are comprised of molecules that contain both a head and tail group, and can be used to coat metal to prevent biofilm formation and bacteria growth. 12-mercaptododecylphosphonic acid self-assembled monolayers have a phosphonic acid head group and a thiol tail group. A solution of
12-mercaptododecylphosphonic acid in tetrahydrofuran ...

Competing Irreversible Cooperative Reactions On Polymer Chains, James W. Evans, D. K. Hoffman, D. R. Burgess

James W. Evans

We analyze model processes involving competition between several irreversible reactions at the sites of a 1D, infinite, uniform polymer chain. These reactionscan be cooperative, i.e., the corresponding rates depend on the state of the surrounding sites. An infinite hierarchy of rate equations is readily derived for the probabilities of various subconfigurations. By exploiting a shielding property of suitable blocks of unreacted sites, we show how exact hierarchy truncation and solution is sometimes possible. The behavior of solutions is illustrated in several cases by plotting families of ‘‘reaction trajectories’’ for varying ratios of reactant concentrations ...

Optimization Of Multiplex Pcr For Multiple Locus Variable Number Tandem Repeat Analysis For Salmonella Typhimurium, George Hafez, Remington Turner, Andrea Haskett, Rajesh Nagarajan

Rajesh Nagarajan

Salmonella typhimurium infects an estimated 1.4 million in the United States and kills over five hundred annually. The current way of categorization, Pulse Field Gel Electrophoresis (PFGE) and antibiotic sensitivity testing, lack the ability to distinguish between some closely related strains. We are attempting to optimize a new technique of categorization, Multiple Locus Variable number tandem repeat Analysis (MLVA). We made changes to temperature and concentration variables within the multiplex PCR procedure to streamline the identification process. By optimizing the multiplex PCR procedure we intend to create more consistent amplification of the loci used in MLVA analysis, which will ...

Cobalt-Doped Ceria/Reduced Graphene Oxide Nanocomposite As An Efficient Oxygen Reduction Reaction Catalyst And Supercapacitor Material, Mohammad Mansoob Khan Dr

Dr. Mohammad Mansoob Khan

58th Annual Rocky Mountain Conference On Magnetic Resonance

Rocky Mountain Conference on Magnetic Resonance

Final program, abstracts, and information about the 58th annual meeting of the Rocky Mountain Conference on Magnetic Resonance, co-endorsed by the Colorado Section of the American Chemical Society and the Society for Applied Spectroscopy. Held in Breckenridge, Colorado, July 17-21, 2016.