Physical Sciences and Mathematics Commons^™

Ab Initio Structural Studies Of Cyclobutylmethyl Cations: Effect Of Fluoroalkyl Groups On The Relative Stability Of The Carbocations, Prakash Reddy, Golam Rasul, G. K. Surya Prakash

Chemistry Faculty Research & Creative Works

Ab initio calculations at MP2/cc-pVTZ level show that the trifluoromethyl group has a strong destabilizing effect on the nonclassical, σ-bridged cyclobutylmethyl cations. The GIAO-MP2 derived ¹³C NMR chemical shifts indicate substantial charge delocalization from the neighboring cyclobutyl ring for carbocations with an α-fluorolkyl group as compared to the 1-cyclobutylethyl cation, and this enhanced charge delocalization in case of the α-(trifluoromethyl)cyclobutylmethyl cation would lead to the ring-opening rearrangement to form the relatively more stable nonclassical primary cyclobutylmethyl cation, in which the carbocation center is farthest from the strongly electron-withdrawing trifluoromethyl group.

Air-Oxidation Of Phenolic Resin Aerogels: Backbone Reorganization, Formation Of Ring-Fused Pyrylium Cations, And The Effect On Microporous Carbons With Enhanced Surface Areas, Hojat Majedi Far, Suraj Donthula, Tahereh Taghvaee, Adnan Malik Saeed, Zachary Garr, Chariklia Sotiriou-Leventis, Nicholas Leventis

Chemistry Faculty Research & Creative Works

This paper is a thorough investigation of the chemical transformations during pyrolytic conversion of phenolic resins to carbons, and reports that all carbons obtained from main-stream phenolic resins including phloroglucinol-formaldehyde (FPOL), phloroglucinol-terephthalaldehyde (TPOL), resorcinol-formaldehyde (RF), and phenol-formaldehyde (PF) contain fused pyrylium rings and charge-compensating phenoxides. Those four phenolic resins were prepared via a fast HCl-catalyzed process as low-density nanostructured solids classified as aerogels, which, owing to their open porosity, allowed air circulation through their bulk. In that regard, the first step of this study was the air-oxidation of those phenolic resin aerogels at 240 °C. In FPOL and TPOL aerogels, …

Investigation Of The Ozone Formation Reaction Pathway: Comparisons Of Full Configuration Interaction Quantum Monte Carlo And Fixed-Node Diffusion Monte Carlo With Contracted And Uncontracted Mrci, Andrew D. Powell, Nikesh S. Dattani, Rene F. K. Spada, Francisco B. C. Machado, Hans Lischka, Richard Dawes

Chemistry Faculty Research & Creative Works

The association/dissociation reaction path for ozone (O₂ + O ↔ O₃) is notoriously difficult to describe accurately using ab initio electronic structure theory, due to the importance of both strong and dynamic electron correlations. Experimentally, spectroscopic studies of the highest lying recorded vibrational states combined with the observed negative temperature dependence of the kinetics of oxygen isotope exchange reactions confirm that the reaction is barrierless, consistent with the latest potential energy surfaces. Previously reported potentials based on Davidson-corrected internally contracted multireference configuration interaction (MRCI) suffer from a spurious reef feature in the entrance channel even when extrapolated …

Fuzzy Color Clustering For Melanoma Diagnosis In Dermoscopy Images, Haidar A. Almubarak, R. Joe Stanley, William V. Stoecker, Randy Hays Moss

Electrical and Computer Engineering Faculty Research & Creative Works

A fuzzy logic-based color histogram analysis technique is presented for discriminating benign skin lesions from malignant melanomas in dermoscopy images. The approach extends previous research for utilizing a fuzzy set for skin lesion color for a specified class of skin lesions, using alpha-cut and support set cardinality for quantifying a fuzzy ratio skin lesion color feature. Skin lesion discrimination results are reported for the fuzzy clustering ratio over different regions of the lesion over a data set of 517 dermoscopy images consisting of 175 invasive melanomas and 342 benign lesions. Experimental results show that the fuzzy clustering ratio applied over …

The Covalent Interaction Between Dihydrogen And Gold: A Rotational Spectroscopic Study Of H₂-Aucl, Daniel A. Obenchain, Derek S. Frank, Garry S. Grubbs, Herbert M. Pickett, Stewart E. Novick

Chemistry Faculty Research & Creative Works

The pure rotational transitions of H₂-AuCl have been measured using a pulsed-jet cavity Fourier transform microwave spectrometer equipped with a laser ablation source. The structure was found to be T-shaped, with the H-H bond interacting with the gold atom. Both ³⁵Cl and ³⁷Cl isotopologues have been measured for both ortho and para states of H2. Rotational constants, quartic centrifugal distortion constants, and nuclear quadrupole coupling constants for gold and chlorine have been determined. The use of the nuclear spin-nuclear spin interaction terms D_aa, D_bb, and D_cc for H₂ were required …

Prevention And Reversal Of Selenite-Induced Cataracts By N-Acetylcysteine Amide In Wistar Rats, Yasaswi Maddirala, Shakila Tobwala, Humeyra Karacal, Nuran Ercal

Chemistry Faculty Research & Creative Works

Background: The present study sought to evaluate the efficacy of N-acetylcysteine amide (NACA) eye drops in reversing the cataract formation induced by sodium selenite in male Wistar rat pups.

Methods: Forty male Wistar rat pups were randomly divided into a control group, an N-acetylcysteine amide-only group, a sodium selenite-induced cataract group, and a NACA-treated sodium selenite-induced cataract group. Sodium selenite was injected intraperitoneally on postpartum day 10, whereas N-acetylcysteine amide was injected intraperitoneally on postpartum days 9, 11, and 13 in the respective groups. Cataracts were evaluated at the end of week 2 (postpartum day 14) when the rat pups …

Inelastic Rate Coefficients For Collisions Of C₆Hˉ With H₂ And He, Kyle M. Walker, François Lique, Fabien Dumouchel, Richard Dawes

Chemistry Faculty Research & Creative Works

The recent detection of anions in the interstellar medium has shown that they exist in a variety of astrophysical environments -- circumstellar envelopes, cold dense molecular clouds and star-forming regions. Both radiative and collisional processes contribute to molecular excitation and de-excitation in these regions so that the ‘local thermodynamic equilibrium’ approximation, where collisions cause the gas to behave thermally, is not generally valid. Therefore, along with radiative coefficients, collisional excitation rate coefficients are needed to accurately model the anionic emission from these environments. We focus on the calculation of state-to-state rate coefficients of the C₆H^- molecule in …

Multifunctional Porous Aramids (Aerogels), Fabrication Thereof, And Catalytic Compositions Derived Therefrom, Nicholas Leventis, Chariklia Sotiriou-Leventis, Malik Adnan Saeed

Chemistry Faculty Research & Creative Works

The present disclosure provides a series of new and improved porous polyamide aerogels derived from multifunctional aromatics that combine the high mechanical strength of aramids with the pore structure of aerogels. The polyamide aerogels have a hyperbranched structure, relatively low density, high porosity and may be derived from functionalized monomers having more aromatic groups than functional groups. The present disclosure also provides a new method for producing the porous polyamide aerogels by polymerizing an aromatic multifunctional carboxylic acid or a ferrocene multifunctional carboxylic acid with a polyfunctional aromatic isocyanate at moderate reaction conditions followed by drying with liquid CO2. Also …

Polycyclic Aromatic Hydrocarbons With Aliphatic Sidegroups: Intensity Scaling For The C-H Stretching Modes And Astrophysical Implications, Xuejuan Yang, Aigen Li, Rainer Glaser, Jianxin Zhong

Chemistry Faculty Research & Creative Works

The so-called unidentified infrared emission (UIE) features at 3.3, 6.2, 7.7, 8.6, and 11.3 μm ubiquitously seen in a wide variety of astrophysical regions are generally attributed to polycyclic aromatic hydrocarbon (PAH) molecules. Astronomical PAHs may have an aliphatic component, as revealed by the detection in many UIE sources of the aliphatic C-H stretching feature at 3.4 mm. The ratio of the observed intensity of the 3.4 mm feature to that of the 3.3 μm aromatic C-H feature allows one to estimate the aliphatic fraction of the UIE carriers. This requires knowledge of the intrinsic oscillator strengths of the 3.3 …

Cost Effective Surface Functionalization Of Gold Nanoparticles With A Mixed Dna And Peg Monolayer For Nanotechnology Applications, Risheng Wang, Isabella Bowling, Wenyan Liu

Chemistry Faculty Research & Creative Works

A cost effective and generally applicable co-functionalization of gold nanoparticles with a mixed DNA and PEG polymers is reported. Compared to the pure DNA functionalization method, this protocol uses a much smaller amount of thiol-DNA to achieve a similar binding efficacy of gold nanoparticles with DNA origami nanostructures. The lower consumption of DNA provides a scaling-up potential for the application of DNA-nanoparticle conjugates in nanotechnology.

Biomarker Discovery Using Urinary Metabolomics For Noninvasive Early Cancer Detection, Casey Franklin Burton

Doctoral Dissertations

"The development of new screening methods for the early detection of cancer remains one of the foremost challenges facing modern cancer research. The emergence of new analytical technologies and their application to 'omics'-based approaches has provided researchers with powerful new tools for molecular biomarker discovery that may benefit early screening of cancer. This dissertation outlines several key advances made toward the application of urinary metabolomics to cancer biomarker discovery. The term urinary metabolomics here refers to the investigation of small metabolites in urine as potential disease biomarkers. The advantage of using this approach lies in its noninvasive sampling characteristics and …

Textured Nise₂ Film: Bifunctional Electrocatalyst For Full Water Splitting At Remarkably Low Overpotential With High Energy Efficiency, Abdurazag T. Swesi, Jahangir Masud, Wipula P. R. Liyanage, Siddesh Umapathi, Eric W. Bohannan, Julia E. Medvedeva, Manashi Nath

Physics Faculty Research & Creative Works

Herein we have shown that electrodeposited NiSe₂ can be used as a bifunctional electrocatalyst under alkaline conditions to split water at very low potential by catalyzing both oxygen evolution and hydrogen evolution reactions at anode and cathode, respectively, achieving a very high electrolysis energy efficiency exceeding 80% at considerably high current densities (100 mA cm^-2). The OER catalytic activity as well as electrolysis energy efficiency surpasses any previously reported OER electrocatalyst in alkaline medium and energy efficiency of an electrolyzer using state-of-the-art Pt and RuO₂ as the HER and OER catalyst, respectively. Through detailed electrochemical and …

In Situ Ph Determination Based On The Nmr Analysis Of ¹H-Nmr Signal Intensities And ¹⁹F-Nmr Chemical Shifts, Ming Huang

Masters Theses

"The pH of an NMR sample can be measured directly by NMR experiments of signal intensities, chemical shifts, or relaxation time constants that depend on the pH. The ¹H NMR peak intensities of the pH indicator phenolphthalein change as it changes from the OH-depleted form to the OH-rich form in the range of pH = 11.1 to 12.7. Because this range is rather small, another NMR technique was utilized based on ¹⁹F chemical shifts. The shift of F^- in an aqueous solution of NaF changes in the alkaline range between pH = 11.0 and 14.0 and even …

Designing High Performance Overall Water Splitting Electrocatalysts From Non-Precious Metal Selenides, Abdurazag T. Swesi

Doctoral Dissertations

“The energy production has been depending mostly on fossil fuel which will be depleted someday in the near future. Aspects such as the loss of energy resources and destruction of the environment have motivated researchers for pursuing transition away from fossil fuels to renewable solar-fuels. Therefore, in order to meet the continuous increasing demand for energy, the hydrogen, with the largest energy density stored in it, can then efficiently be used in fuel cells without concern of contaminants. Water splitting reaction to generate H₂ and O₂ is one promising method of converting solar energy into fuels. The major …

Drinking Water Disinfection By-Products Detection, Formation And The Precursors Removal Study, Runmiao Xue

Doctoral Dissertations

"Haloacetic acids (HAAs) and trihalomethanes (THMs) are two groups of commonly found disinfection by-products (DBPs). Iodinated THMs and HAAs were observed after disinfection of water containing high level of iodide and are proved to be more toxic than their corresponding chlorinated and brominated species. In the presented dissertation, a novel rapid and sensitive high performance ion chromatography-tandem mass spectrometry (HPIC-MS/MS) method has been developed for simultaneous analysis of all these HAAs, bromate, bromide, iodide, and iodate, seventeen compounds in total, without any tedious sample preparation. Besides an efficient analytical method for the detection of DBPs, seeking for a green disinfectant …

Advanced Analytical Strategies To Determine Biomedical Parameters For Medical Diagnostics, Drug Delivery, And Therapy, Sisi Chen

Doctoral Dissertations

"Biomedical parameters are critical for diseases prognosis, diagnosis and therapy. Many research groups have dedicated their studies to develop analytical instrumentation and apply analytical methods to determine biomedical parameters that have the potential to help with disease control and increase public health. This dissertation focuses on three major aspects of analytical strategies development and applications: 1) detection of pH changes caused by nanotoxicity (induced by TiO₂ nanoparticles) using newly developed micro-pH sensor, 2) quantification of renal cell carcinoma (RCC) biomarkers by high-performance liquid chromatography - tandem mass spectrometry (HPLC-MS/MS), and 3) nuclear magnetic resonance (NMR) studies of porous wall …

Rapid Quantification Of Trypsin Inhibitors In Food And Feed Formulations With Electrospray Ionization Mass Spectrometry, Radheshyam Panta

Doctoral Dissertations

"Presence of anti- nutrients deteriorate the nutritional value of animal foods and feed formulations. The important one being trypsin inhibitors. Trypsin inhibitors in food and feed formulations lower the protein supplement and hence the ultimate consequence is the decrease in growth and development of animals. It is therefore, crucial to monitor trypsin inhibitors in animal food and feed formulations. Research work mentioned in this dissertation is based on the development of rapid, more accurate and robust method for determination of trypsin inhibitor in food and feed formulations. The developed method includes extraction of trypsin inhibitor from food and feed formulation …

Application Of Quantum Monte Carlo Methods To Molecular Potential Energy Surfaces, Andrew Douglas Powell

Doctoral Dissertations

"Various computational methods have been used to generate potential energy surfaces, which can help us simulate and interpret how atoms or molecules behave during a chemical reaction. For accurate work, ab initio wavefunction methods have traditionally been used, which have some disadvantages. For example, highly accurate methods scale poorly with system size (n⁷ or higher) and are mostly not well parallelized for calculations with multiple processors. One alternative method that has more favorable scaling with system size and is well parallelized is a computational technique called quantum Monte Carlo (QMC). QMC methods scale with the number of electrons as …

Optimization Of Solvent Suppression Sequences For Nmr Analysis Of Aqueous Solutions, Annalise Rose Pfaff

Doctoral Dissertations

"When the use of deuterated solvents is precluded in the NMR analysis of biomolecules in their natural environment, pre-saturation solvent suppression pulse sequences are frequently employed to avoid interference from the overbearing solvent signal. However, these sequences generally require extensive re-adjustment of NMR parameters between samples. For this reason, the EXCEPT (EXponentially Converging Eradication Pulse Train) solvent suppression sequence was developed, which exhibits a tolerance of over an order of magnitude in sample T₁ variation. EXCEPT uses an innovative version of "inversion-recovery nulling" with frequency-selective, low-power adiabatic pulses and exponentially decreasing interpulse delays that effectively reduce solvent net magnetization by …

The Maculoprotective Effect Of A Thiol Antioxidant In Retinal Degeneration Models, Hsiu-Jen Wang

Doctoral Dissertations

"Age-related macular degeneration (AMD) is a leading cause of irreversible blindness among adults, age 60 and older, in developed countries. While oxidative stress is implicated in the pathogenesis of AMD, clinical studies have shown that dietary antioxidants can delay progression of AMD. Currently, there is no FDA-approved treatment for AMD. Therefore, we hypothesized that N-acetylcysteine amide (NACA), a thiol antioxidant, would protect retinal pigment epithelium and impede the progression of retinal degeneration. The goal of this work was to evaluate the efficacy of NACA in preventing retinal pigment epithelial cell and photoreceptor death in AMD models. To achieve this, we …