Digital Commons Network^™

Element Transport In A River-Lake Continuum Across Forest-Dominated Landscapes: A Case Study In Central Louisiana, Zhen Xu

LSU Doctoral Dissertations

Studying the biogeochemical connectivity between rivers and lakes can help us understand their ecological and environmental impacts within a drainage basin, which is especially true for forest watersheds that play a vital role in provisioning freshwater services to ecosystems and downstream communities. This dissertation research consists of three interconnected studies with the overarching goal of discerning the connectivity of elements in a river-lake continuum across forest-dominated landscapes. These studies utilized water samples and in situ measurements collected from the Little River-Catahoula Lake continuum in the subtropical Louisiana, USA at monthly intervals during 2015-2016 and 1978-2008 historical water quality, hydrological and …

Aromatic Interactions At The Ligand–Protein Interface: Implications For The Development Of Docking Scoring Functions, Michal Brylinski

Faculty Publications

© 2017 John Wiley & Sons A/S The ability to design and fine-tune non-covalent interactions between organic ligands and proteins is indispensable to rational drug development. Aromatic stacking has long been recognized as one of the key constituents of ligand–protein interfaces. In this communication, we employ a two-parameter geometric model to conduct a large-scale statistical analysis of aromatic contacts in the experimental and computer-generated structures of ligand–protein complexes, considering various combinations of aromatic amino acid residues and ligand rings. The geometry of interfacial π–π stacking in crystal structures accords with experimental and theoretical data collected for simple systems, such as …

Time-Lapse Polymerizations Triggered By Ph Clock Reactions, Elizabeth Jee

LSU Doctoral Dissertations

The theme of this work is time-lapse polymerizations triggered by pH clock reactions. The first chapter is the introduction and gives a long overview of the different chemistries studied here. The second chapter focuses on the bromate-sulfite clock reaction. Based on some simplified and accepted reaction equations for the bromate-sulfite clock. We presumed it may be possible to increase the pH of the solution via ammonia addition and hinder or significantly reduce the reactivity of the clock reagents, thus creating a storage stable reaction. Adding a polymer system that would not crosslink until the solution became acidic would have created …

The Effectiveness Of Online Homework Tutorials As Compared To Pen And Paper Tutorials, Molly Shuman

LSU Master's Theses

The purpose of this study was to determine if students learn more from completing web based homework (WBHW) compared to completing homework by traditional means with pen and paper. Determining the efficacy of WBHW is important because many schools are being pressured to implement technology in the classroom. To determine the effectiveness of WBHW, student normalized learning gains were calculated from pre and post-test scores for 62 students. Learning gains were then compared when students completed WBHW, traditional homework, or did not complete homework at all, over four units in a high school chemistry class. No difference in learning gains …

Chemically Patterned Surfaces As Test Platforms To Study Magnetic And Solvent-Responsive Properties At The Nanoscale: Investigations Using Scanning Probe Microscopy, Shalaka Kulkarni

LSU Doctoral Dissertations

Chemically patterned surfaces were fabricated using a combination of molecular self-assembly and particle lithography to generate billions of nanostructures of organosilane self-assembled monolayers (SAMs). Monodisperse mesospheres were used as surface masks to prepare nanostructures on flat surfaces using the simple benchtop chemistry steps of mixing, centrifuging, evaporation, and drying. Periodic arrays of well-defined organosilane nanostructures serve as discrete surface sites for the selective deposition of polymers and magnetic nanoparticles.

In this dissertation, particle lithography approaches for surface patterning provide new directions for studying surface chemistry at the molecular-level using high resolution investigations with scanning probe microscopy (SPM). Atomic force microscopy …

The Power Of Affective Factors (Self-Efficacy, Motivation And Gender) To Predict Chemistry Achievement With The Benefits Of Knowledge Surveys On Metacognition Level, Xin Wu

LSU Doctoral Dissertations

Self-efficacy, gender, and motivation are subjective predictors of students' academic achievement. Self-assessment prompted by knowledge surveys involves metacognition, i.e., students' awareness of how they learn. Knowledge surveys can be used to measure changes in students' achievement level and to assist students in content review and inspire reflection on one's ability to learn. In this work, I combined the above predictors into the survey to determine whether achievement in general chemistry can be foreseen. My proposed research will be conducted on 426 students enrolled in General Chemistry I classes (Chemistry for science majors) during a regular 15-week semester at Louisiana State …

Application Of Scanning Probe Microscopy For New Physical Measurements And Studies Of Surface Chemical Reactions Of Materials At The Molecular Level, Stephanie Loletha Daniels

LSU Doctoral Dissertations

Scanning probe microscopy (SPM) provides unique capabilities for surface visualization and measurements that reach atomic and molecular dimensions. My research focus is directed toward applying and developing new measurements for analytical and surface chemistry with SPM. Two distinct goals based on studies with atomic force microscopy (AFM) will be described within this dissertation. The primary goal was to develop and apply a new AFM imaging mode for ultrasensitive measurements of the superparamagnetic properties of proteins. Magnetic sample modulation (MSM)-AFM, has capabilities to investigate and map the magnetic response of nanomaterials with unprecedented spatial resolution. The second goal was to apply …

Inhibition And Nucleic Acid Binding Studies Of The Carboxyltransferase Component Of Bacterial Acetyl-Coa Carboxylase, Brian Benson

LSU Doctoral Dissertations

Acetyl-CoA carboxylase is an essential enzyme, as it catalyzes the first committed and regulated step in fatty-acid biosynthesis in all organisms excepting few Archaea and Eubacteria. Acetyl-CoA carboxylase from gram-negative and gram-positive bacteria is a multifunctional enzyme composed of three separate proteins. The carboxyltransferase subunit catalyzes the transfer of a carboxyl group from carboxybiotin to acetyl-CoA, forming malonyl-CoA. The crystal structure of the Escherichia coli (E. coli) carboxyltransferase component of acetyl-CoA carboxylase revealed a unique Zn-domain, presumed to mediate nucleic acid binding, that is absent in the eukaryotic enzyme. Notably, the Zn-domain, adjacent to the active site of carboxyltransferase, makes …

Studies Of Nanoparticles From A Group Of Uniform Materials Based On Organic Salts (Gumbos), Aaron Tesfai

LSU Doctoral Dissertations

Tesfai, Aaron, B.S., B.A., University of Missouri, Columbia, 2003 Doctor of Philosophy, Spring Commencement 2010 Major: Chemistry Studies of Nanoparticles from a Group of Uniform Materials Based on Organic Salts (GUMBOS) Dissertation directed by Professor Isiah M. Warner Pages in dissertation, 101. Words in abstract, 271. Ionic liquids (ILs) are defined as organic salts composed of ions with melting points at or below 100 °C. ILs have gained considerable attention because of their desirable properties such as low volatility, high thermal stability, and tunability. GUMBOS are an emergent class of organic salts, many of which are ionic liquids (ILs). However, …

The Hydrology And Sediment Transport Of Low-Gradient, Forested Headwater Streams, Philip Saksa

LSU Master's Theses

Understanding stream hydrology of headwater regions is critical in effective land management for downstream water quantity and quality. Although extensive research has been performed on headwater streams in topographically variable areas, fewer studies examine low-gradient headwater stream systems, such as those existing on much of the southeastern coastal plain. This study aims to investigate spatial and temporal variation of headwater stream hydrology in a low-gradient forested watershed, quantify mass loading of suspended and dissolved solids in the watershed, and assess the applicability of a spatially distributed model in predicting hydrologic responses of a flat terrain landscape. Stream discharge and sediments …

Transport And Kinetics Of Aromatic Hydrocarbons Into Micron-Sized Liquid Droplets: With Applications To Atmospheric Chemistry, Suresh Raja

LSU Doctoral Dissertations

In the natural process of wet deposition, gas-water interfaces play an important role in the transport of chemical contaminants in the atmosphere via fog, rain and cloud drops. Evidences from several other works point out deviations in gas-liquid partitioning as predicted by Henry’s law. Uptake and mass transfer of benzene, naphthalene, and phenanthrene was chosen to study in a falling droplet train apparatus. Higher droplet-to-vapor partition constant (KDV) was noted for diameters less than 200ìm and was attributed to surface adsorption and accumulation. Mass transfer of phenanthrene was dependent on gas-phase diffusion and mass accommodation at the interface, while the …

Electronic Structural Investigations Of Bi- And Polymetallic Complexes Using Quantum Mechanical Methods, Zakiya Sheni Wilson

LSU Doctoral Dissertations

Understanding the dynamics influencing chemical reactivity is essential for properly exploiting matter into more useful purposes. In that manner, computational chemistry is a tool frequently used to study chemical properties at the most intimate level, i.e. the single molecule.

With this work, we probe the chemistry governing a variety of multi-faceted bi- and polymetallic compounds. To date our research consists of four major projects: bimetallic rhodium-catalyzed hydroformylation and aldehyde-water shift hydrocarboxylation catalysis; a novel linear M-H-M interaction in a bridged bis(dialkylphosphino)methane complex of nickel; and CeBe₁₃, a heavy fermion conductor. Computational investigations on these systems allow us to …

Stormwater Diversion As A Potential Coastal Wetland Restoration Method, Jennifer Howard Woods

LSU Master's Theses

The Barataria-Terrebonne estuary has been eroding at a rate of up to 103.6 km2 yr-1 for several decades. If the current rate of loss is not reduced, an additional 2,550 km2 of coastal wetlands will be lost by the year 2050. Currently, stormwater in Terrebonne Parish is pumped into canals, ultimately discharging into the Gulf of Mexico. An opportunity exists to use this stormwater for wetland restoration; however, the ecological impacts of stormwater diversions on wetlands are unknown. The objectives of this project were to 1) to investigate the seed banks of a degraded marsh to determine if a viable …

Detrital Tourmaline As An Indicator Of Provenance: A Chemical And Sedimentological Study Of Modern Sands From The Black Hills, South Dakota, David Brent Viator

LSU Master's Theses

Detrital tourmaline has proven useful as a provenance indicator mineral of ancient sedimentary/metasedimentary units due to its presence in many rock types, chemical responsiveness to environments of formation, complex and variable chemical compositions, high resistance to chemical and mechanical weathering, and stability through diagenesis and metamorphism. This study further establishes detrital tourmaline as a provenance indicator mineral by examining the chemical and sedimentological relationships between modern detrital tourmalines in the sediments of the Black Hills, South Dakota, USA, and in situ tourmalines from southern Black Hills’ tourmaline-bearing metasedimentary rocks, granites, and rare-element enriched pegmatites. Results show that detrital tourmaline is …

Analysis Of Hydrocarbon Materials By Use Of Nonpolar Matrices In Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry (Maldi-Ms)., Stephen Francis Macha

LSU Historical Dissertations and Theses

In this study, polyaromatic hydrocarbon compounds including anthracene, pyrene, acenaphthene and perylene were investigated as nonpolar matrices in matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) for the analysis of selected nonpolar analytes. First, the influence of matrix and the analyte ionization potentials on a charge-transfer ionization mechanism were determined. Results of these studies demonstrated that formation of radical molecular cations in MALDI-MS depends on the ionization energy difference between the matrix and the analyte. Charge-transfer ionization occurs only when the ionization potential of the matrix is higher than that of the analyte. Next, nonpolar matrices were investigated for the analysis of …

Theoretical Studies Of Sodium Metal Clusters., Melissa R. Prince

LSU Historical Dissertations and Theses

Theoretical methods were used to study small sodium metal clusters. The goal was to find a simple way to model the electronic structure in these clusters that can be used to study large sodium clusters. Monte Carlo studies using Feynman's path integral formulation of quantum mechanics with Bose-Einstein statistics were used to study sodium metal clusters whose valence electrons with opposite spins were paired as bosons. Next, non-atom-based Gaussian s orbitals were used in a Hartree-Fock Monte Carlo procedure. Based on these results, standard quantum chemistry programs were used to test the utility of using non-atom-based basis sets made up …

Redox, Ph, And Ion Chemistry Of Acid Sulfate Rice Soils In Thailand., Sunchai Satawathananont

LSU Historical Dissertations and Theses

Five Thailand soils belonging to the Rangsit Very Acid (Rsa), Rangsit (Rs), Mahaphot (Ma), Bang Pakong (Bg), and Bangkok (Bk) series were employed in redox-pH-ion chemistry studies. Decreases in soil redox potential upon submergence were relatively slower and less intense in the acid sulfate soils than in the non-acid marine soil. Among the acid sulfate soils, the Rsa soil was most sluggish with respect to decreases in redox potential. Addition of organic matter or liming in combination with submergence accelerated decreases in redox potential in the flooded Rsa soil as well as in the other acid sulfate soils to the …