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Biothermodynamics Of Metal And Dna Coordination To The Pneumococcal Transcription Factors Adcr, Scza, And Copr, Alexander James Cutright

Theses and Dissertations

ransition metals are micronutrients that play critical roles in all forms of life, acting as stabilizing ions, catalytic centers, and as signaling ions. Due to their importance, classes of biomolecules have been designed with the sole purpose of regulating their intracellular concentrations. One group of which are transcription factors, which regulate intracellular metal concentration by activating or repressing transcription, dependent on metal availability. The activation of transcription factors by metal availability can be attested to conformational changes that are governed by both dynamics and thermodynamics. Due to the influential nature of transcription factors, their activity and activation mode have become …

Investigating Student Expectations, Buy-In, And Engagement In Lower Division Undergraduate Chemistry Labs, Elizabeth Blanche Vaughan

Dissertations and Theses

Laboratory courses constitute an integral aspect of chemistry education at the undergraduate level. Despite their prominence, a growing number of researchers have begun to think more critically about the value of laboratory learning experiences. As pedagogical decisions should be based on evidence, it is necessary for chemistry education researchers and practitioners to investigate the claim that teaching laboratories are a valuable part of science education. Therefore, the aim of this dissertation was to address one small section of this gap in the literature by obtaining a more robust understanding of students' expectations, buy-in, and engagement in lower division, undergraduate, chemistry …

Design, Synthesis, And Nmr-Guided Characterization Of A Targeted Covalent Inhibitor-Like Molecule Against Ivyp1 From P. Aeruginosa, Samuel Taylor Moore

Master's Theses

Multi-drug resistance poses a serious threat to future generations and historical antibiotic pipelines; consequently, the medical and economic burdens associated with treating multidrug-resistant bacteria are substantiated. In this context, P. aeruginosa (PA) emerges as one of the most significant healthcare challenges, being a leading cause of resistance-associated mortality worldwide. Despite modern efforts to combat these poor outcomes, drug-resistant cases continue to rise, and the need for novel antibiotic treatment is apparent. To this end, we investigated relevant resistance mechanisms and past antibiotic targets within PA, and in doing so, we identified relationships between peptidoglycan biology and a periplasmic protein, Inhibitor …

Investigation Of Real-Time Gaseous Thermal Decomposition Products Of Representative Per- And Polyfluoroalkyl Substances (Pfas), Kateřina Litvanová, Bethany Klemetstrud, Feng Xiao, Alena Kubatova

Chemistry Faculty Publications

The thermal decomposition of per- and poly fluoroalkyl substances (PFAS) is poorly understood. Here, we present an innovative, comprehensive analytical method to investigate their thermal decomposition, including perfluorocarboxylic acids (PFCAs), alcohol, sulfonates, and GenX (acid dimer), focusing on identifying their breakdown products. In this study, evolved gas analysis–mass spectrometry (EGA-MS) was used for fast real-time screening to determine the significant temperatures to be investigated with the thermal desorption-pyrolysis coupled with gas chromatography–mass spectrometry (TD-Py-GC-MS), which provided detailed information about evolved PFAS and their breakdown products. This approach enabled a systematic study of perfluorocarboxylic acids (PFCAs) ranging from C₃ to …

Exfoliated Hydrotalcite-Transition Metal Complex Composite For Eco-Friendly And Efficient Catalytic Degradation Of 4-Nitrophenol, Sidra Khan, Najma Memon, Saima Q. Memon, Yilmaz Yurekli

Karbala International Journal of Modern Science

Nitrophenols are notorious aquatic organic contaminants found as degradation products of various parent compounds, including pesticides and industrial chemicals that persist in the environment and must be removed. Catalytic degradation is one of the feasible routes to clean the contaminated water systems, however, environmental contamination with catalysts is also widespread. Herein, we report an environmentally friendly catalyst based on composited Fe-Schiff’s base with exfoliated layered double hydroxides (LDH) of aluminum and nickel (hydrotalcite). The composite showed agglomerated pleated LDH structures sheathed with Fe(III)SB. Nitrogen adsorption isotherm data exhibited improved surface area and narrow pores patterns for composite as compared to …

The Utilization Of Alcohol Dehydrogenase (Adh) Enzymes In Stereocontrolled Synthesis, Gaurav Pramod Kudalkar

Dissertations and Doctoral Documents, University of Nebraska-Lincoln, 2023–

Clostridium acetobutylicum alcohol dehydrogenase (CaADH) has been shown to catalyze the stereoselective reduction of a broad array of carbonyl compounds. This study uses a Hammett linear free-energy relationship (LFER) analysis to gain insight into CaADH enzyme mechanism across three substrate classes: aryl aldehydes, aryl β-keto esters, and aryl trifluoromethyl ketones. Kinetic data were collected by monitoring NADPH fluorescence, and Michaelis-Menten kinetics were applied. Hammett plots reveal that hydride transfer is rate-limiting for aldehydes and β-keto esters (ρ > 0), while it is proposed that dehydration is rate-limiting for trifluoromethyl ketones (ρ < 0). ¹³C NMR confirmed significant hydration in trifluoromethyl ketones. The …

Physical Properties Of Aqueous Imide-Based Electrolyte Solutions, Mollie Harr

Honors Capstones

In order to observe the effects that cations have on the physical properties of -TFSI [-bis(trifluoromethane sulfonyl)imide] based salts, four salts (LiTFSI, NaTFSI, Mg(TFSI)2, and Al(TFSI)3) were selected for testing. The data gathered shows that when the anion is large and bulky like -TFSI, the size of the cation does not have a large effect on the physical properties, but the oxidation state of the cation may have a significant effect. The ion-ion interactions, such as collisions, aggregation, and repulsion are more significant when the cation has a higher oxidation state due to the increased ratio of anion per molecule …

Increased Thermal Stability And Retained Antibacterial Properties In A Sulbactam And Amantadine Salt: Towards Effective Antibacterial-Antiviral Combination Therapies, Josephine Bicknell, Ivan Bondarenko, Alice Colatrella, Elani J. Cabrera-Vega, Jesus Daniel Loya, Delbert S. Botes, Jay L. Mellies, Gonzalo Campillo-Alvarado

Chemistry Faculty Publications and Presentations

A clinically relevant multidrug solid comprising sulbactam (β-lactamase inhibitor) and amantadine (antiviral) displays enhanced thermal stability and sustained antibacterial activity compared to starting materials.

We describe the formation of a multidrug salt comprising sulbactam (SUL, β-lactamase inhibitor) and amantadine (AMNH, antiviral). Physicochemical investigation of the SUL·AMNH salt revealed enhanced thermal stability compared to pristine starting materials. In vitro studies found that salt formation in SUL·AMNH does not disrupt antibacterial activity against model organisms Escherichia coli and Staphylococcus epidermidis. To our knowledge, we show the first β-lactamase inhibitor-antiviral salt where both components have been approved by the U.S. Food and Drug …

Synthesis And Characterization Of Metal-Organic Framework Nanostructures And Evaluation Of Their Photocatalytic Activity, James Kegere

Thesis/ Dissertation Defenses

Reticular materials have enlisted tremendous interest from researchers across the globe in the last two decades. This heightened interest stems from the novelty in structure and chemistry that renders them peerless in multiple fields such as medicine, energy, and environment. On the environmental research front these materials have found applications in mitigation of different pollutants such as CO₂ which is the most important greenhouse gas through storage and conversion, catalysis of CO₂ conversion into useful products. Furthermore, these materials have also proven to be effective sorbent materials for many toxic compounds that find their way into freshwater systems …

Na2B12Si6Se18: A Novel B12-Cluster-Containing Quaternary Selenoborate Framework Material, Gopabandhu Panigrahi, Hunter B. Tisdale, Gregory Morrison, Hans Conrad Zur Loye

Faculty Publications

We report the successful synthesis of the new quaternary, three-dimensional Na₂B₁₂Si₆Se₁₈ material using a solid-state synthesis route. This compound is characterized by a unique framework structure that features the rare icosahedral [B₁₂]¹⁰⁺ cation which is connected via Si2Se6 polyhedral units into a 3D framework structure with Na+ ions located inside the channels. The Na₂B₁₂Si₆Se₁₈ compound crystallizes in the cubic crystal system in the space group Im, with lattice parameter a = 11.91110(10) Å and unit cell volume of 1689.88(4) ų. …

Development Of A Rapid Method For Pfas Detection And Quantitation In Human Hair, Justin M. Allen

Student Theses

In recent years, per- and polyfluoroalkyl substances (PFAS) have emerged as a critical focus in environmental and public health research due to their persistent nature and widespread use in products ranging from non-stick cookware to firefighting foams. These "forever chemicals" resist degradation, posing significant ecological and human health risks. While extensive studies have explored PFAS in environmental matrices, research into their presence in human hair remains limited, with only a handful of studies addressing this biomarker's potential. This thesis aims to develop a robust analytical method for detecting PFAS in human hair, leveraging its unique properties to provide a long-term …

Antibiotic Resistance Of Laboratory E. Coli Strains, Alexis H. Hart

Honors Projects

Antibiotic resistance is an ongoing global health crisis. The prevalence and distribution of antibiotic resistance in environmental microbial communities have become climactic areas of investigation due to their far-reaching implications for ecosystem health, human well-being, and the sustainability of antimicrobial efficacy.

Kinetics And Oligomer Products Of The Multiphase Reactions Of Hydroxyacetone With Atmospheric Amines, Ammonium Sulfate, And Cloud Processing, David O. De Haan, Leila Nahid Hawkins, Elyse A. Pennington, Hannah G. Walsh, Alyssa A. Rodriguez, Michael A. Symons, Alyssa D. Andretta, Michael A. Rafla, Chen Le, Audrey C. De Haan, Tianqu Cui, Jason D. Surratt, Mathieu Cazaunau, Edouard Pangui, Jean-François Doussin

Chemistry and Biochemistry: Faculty Scholarship

Hydroxyacetone (HA) is an atmospheric oxidation product of isoprene and other organic precursors that can form brown carbon (BrC). Measured bulk aqueous-phase reaction rates of HA with ammonium sulfate, methylamine, and glycine suggest that these reactions cannot compete with aqueous-phase hydroxyl radical oxidation. In cloud chamber photooxidation experiments with either gaseous or particulate HA in the presence of the same N-containing species, BrC formation was minor, with similar mass absorption coefficients at 365 nm (<0.05 m2 g–1). However, rapid changes observed in aerosol volume and gas-phase species concentrations suggest that the lack of BrC was not due to slow reactivity. Filter-based UHPLC/(+)ESI-HR-QTOFMS analysis revealed that the SOA became heavily oligomerized, with average molecular masses of ∼400 amu in all cases. Oligomers contained, on average, 3.9 HA, 1.5 ammonia, and 1.6 other small aldehydes, including, in descending order of abundance, acetaldehyde, glycolaldehyde, glyoxal, and methylglyoxal. PTR-ToF-MS confirmed the production of these aldehydes. We identify C17H26O5, C10H22O9, C15H27NO7, C17H23NO5, and C18H32N2O9 as potential tracer ions for HA oligomers. We hypothesize that efficient oligomerization without substantial BrC production is due to negligible N-heterocycle (e.g., imidazoles/pyrazines) formation. While HA photooxidation is unlikely a significant atmospheric BrC source, it may contribute significantly to aqueous SOA formation.

The Investigation Of The Antimicrobial And Biofilm-Disrupting Properties Of Synthesized Hemibastadin Derivatives., Antonio Harvey

Longwood Senior Theses

This thesis explores the synthesis of a polyphenolic hemibastadin-1 derivative with presumed antimicrobial properties and improved biological safety. Structural modifications included replacing aromatic bromine atoms with phenolic groups and substituting the oxime linker group on the core structure for a triazole. A divergent synthetic strategy was designed with the dimeric nature of these targeted molecules in mind. Although this stepwise synthesis is not complete, the core triazole derivative was prepared with a respectable overall yield of 47% from the methyl gallate starting material. The final steps of the synthesis will require coupling of the divergent intermediates and deprotection of this …

Structural And Electronic Factors Controlling The Efficiency And Rate Of Intersystem Crossing To The Triplet State In Thiophene Polycyclic Derivatives, Cameron Griffrith, Sarah E. Krul, Sean J. Hoehn, Tram Phan, Carlos E. Crespo-Hernández

Faculty Scholarship

Thiophene polycyclic derivatives are widely used in organic light-emitting diodes, photovoltaics, and medicinal chemistry applications. Understanding the electronic and structural factors controlling their intersystem crossing rates is paramount for these applications to be successful. This study investigates the photophysical, electronic structure, and excited state dynamics of 1,2-benzodiphenylene sulfide, benzo[b]naphtho[1,2-d]thiophene, and benzo[b]naphtho[2,3-d]thiophene in polar aprotic and non-polar solvents. Steady-state absorption and emission spectroscopy, femtosecond transient absorption spectroscopy, and DFT and TD-DFT calculations are employed. Low fluorescence quantum yields of 1.2 to 2.7 % are measured in acetonitrile and cyclohexene, evidencing that the primary relaxation pathways in these thiophene derivatives are nonradiative. …

Effect Of Polyacrylamide Gel Elasticity On Collagen Type Ii Fibril Assembly, Kathryn G. Wilcox, Stephanie Kramer, Surajit Chatterjee, Adam Linscott, Sneha Suresh, Lydia Kisley, Svetlana Morozova

Faculty Scholarship

Collagen type II fibrils provide structural integrity to the articular cartilage extracellular matrix. However, the conditions that control the fibril radial size scale, distribution, and formation inside of dense networks are not well understood. We have investigated how surrounding elastic networks affect fibril formation by observing the structure and dynamics of collagen type II in model polyacrylamide gels of varying moduli. Cryogenic transmission electron microscopy (cryo-TEM) is used to image the fibril structure and is verified qualitatively with optical microscopy of fluorescently-tagged collagen within the gels. Using fluorescence correlation spectroscopy super-resolution optical fluctuation imaging (fcsSOFI), the diffusion dynamics of the …

Computational Logp Calculations And Determination Of Lipophilicity Values Of Fluorinated Morphine Derivatives, Mirabella Romano, Allison Vu, Emily Chen

Student Scholar Symposium Abstracts and Posters

The addictive effect of opioids impacted 60 million people globally in 2023. This opioid crisis necessitates the development of opioid derivatives that maintain analgesic efficacy while minimizing addictive effects from opioid use. The present work focuses on morphine, a commonly prescribed opioid with high affinity to the mu-opioid receptor (MOR). Morphine binds non-selectively within both healthy and inflamed tissue. By modifying morphine’s structure through fluorination to counteract its non-selective binding, the drug’s pharmacological ability to provide effective pain relief comes with a lower risk of addiction. Specifically, the addition of fluorine to differing beta positions of the main binding site …

Rings Of Power: Controlling Sod Mimic Activity By The Addition Of Pyridine Rings Within The Pyridinophane Scaffold, Katherine J. Smith, Timothy M. Schwartz, David M. Freire, Cameron Bowers, Sarah K. Dunn, Jackson F. Bonnell, Magy A. Mekhail, Giridhar Akkaraju, Kayla N. Green

Biology, Chemistry, and Environmental Sciences Faculty Articles and Research

Superoxide dismutase enzymes are a major defense against superoxide, which is a potent reactive oxygen species. Misregulation of reactive oxygen species and subsequent neuronal damage are etiological hallmarks of neurodegenerative disease. Macrocyclic small molecules have offered inroads toward functional SOD1 mimics. Herein, we report a series of five tetra-aza macrocyclic ^RPy₂N₂ ligands, varied by 4-position substitution of the pyridine ring with both electron-donating (R = OMe) and withdrawing groups (R = Cl, I, and CF₃) to offer the first comparison to well-studied ^RPyN₃ congeners and other mimics in the literature. New ligands …

D101n: A Unique And Ill-Understood Familial Als-Related Sod1 Mutant, Analisa Lott

Honors Program Theses and Research Projects

Background: Amyotrophic Lateral Sclerosis (ALS) is a fatal neurodegenerative disease, with 90% of documented cases considered sporadic and about 10% showing a hereditary link; such cases are deemed as familial ALS (fALS). Superoxide dismutase (SOD), a copper-zinc binding enzyme that protects cells from damaging free radicals, has been linked to fALS with certain toxic gain of function mutations, such as the D101N mutant. The human SOD1 D101N mutant has been shown to be associated with rapidly progressing neurodegeneration yet is less prone to aggregation than similar mutants, but its deviation from wild-type (WT) SOD1 remains misunderstood.

Objective: Although the D101N …

Alphafold2-Based Characterization Of Apo And Holo Protein Structures And Conformational Ensembles Using Randomized Alanine Sequence Scanning Adaptation: Capturing Shared Signature Dynamics And Ligand-Induced Conformational Changes, Nishank Raisinghani, Vedant Parikh, Brandon Foley, Gennady M. Verkhivker

Mathematics, Physics, and Computer Science Faculty Articles and Research

Proteins often exist in multiple conformational states, influenced by the binding of ligands or substrates. The study of these states, particularly the apo (unbound) and holo (ligand-bound) forms, is crucial for understanding protein function, dynamics, and interactions. In the current study, we use AlphaFold2, which combines randomized alanine sequence masking with shallow multiple sequence alignment subsampling to expand the conformational diversity of the predicted structural ensembles and capture conformational changes between apo and holo protein forms. Using several well-established datasets of structurally diverse apo-holo protein pairs, the proposed approach enables robust predictions of apo and holo structures and conformational ensembles, …

Nanofabrication Of Tetraphenyl Porphyrin Surface Assemblies Linked With Tin Tetrachloride: A Scanning Probe Microscopy Investigation, Quynh Do

LSU Doctoral Dissertations

Scanning probe microscopy (SPM) and colloidal lithography methods were used to study the covalent coupling of porphyrins to surfaces. In this dissertation, experimental methods for SPM operation, techniques, and applications are described. Measurement of tip-sample interactions between a sharp tip and surface is translated into digital image data maps with x-, y-, and z-data. Colloidal lithography can be used to fabricate test platforms for AFM studies. The periodicity and arrangement of the designed nanostructures is determined by the size of the colloidal particles used for surface masks. Data processing is required to obtain images and topography information from raw AFM …

Reaction Of A Chiral Platinum Triamine Compound With Key Amino Acid And Guanine Analog, Onu Emmanuel Chukwu

Masters Theses & Specialist Projects

Platinum compounds can exhibit cytotoxic activity through reaction with DNA; however, interaction with proteins and DNA bases, especially with methionine residues and Guanine analogs, is another common biological reaction. Our lab has synthesized Chloro[2-(4-Methyl-1,4- diazepan-1-yl) ethanamine]platinum(II) chloride ([Pt(L)Cl]Cl), which has a tridentate binding mode for the amine ligand. This study focused on the reaction of the chiral platinum triamine with key amino acids (methionine and 2-hydroxybutyric acid) and guanine analogs under different pH and temperature conditions. The mass spectrometry of N-AcMet Interaction with [Pt(L)Cl]+ showed a m/z of 542 and 579 for reactions at pH 4. The m/z of 542 …

Photogeneration, Characterization, And Kinetic Study Of A New Phthalocyanine Species, Sobenna Onyeso

Masters Theses & Specialist Projects

In the search for green chemistry, the development of synthetic metal complexes that model enzyme function has been extensively studied. Phthalocyanine metal complexes, closely related to these heme-containing macrocycles, have gained continued interest due to their ease of direct synthesis, efficient redox, and optical properties. Despite the significant progress in phthalocyanine metal complexes, much more work needs to be done in the characterization and identification of their metal-oxo species, as well as mechanistic insights into their catalytic oxidations. To date, the reactivity of metal-oxo species on phthalocyanine platforms has not been probed.

In this study, metal phthalocyanine complexes have been …

Investigation Of Polybenzoxazine Vitrimers Based On Dynamic Transesterification Exchange, Jaylen Davis

Dissertations

With the ever-increasing issue of plastic waste production, a greener approach to synthetic processes and increased sustainability in plastic materials is still a high demand. Thermosets, which find uses in applications such as coatings, adhesives, and aerospace composites account for 15% of global plastics production, are particularly problematic in this context, as covalent crosslinks within the material serve both as a source of high-performance stability during use and as a barrier to conventional recycling after use. Therefore, our efforts focus on the incorporation of dynamic transesterification exchange chemistry into polybenzoxazine thermosets, which allows these materials to undergo reprocessing. This investigation …

Sufex-Enabled Stereospecific Deoxygenative Diversification Of Alcohols, Amaechi Odoh

All Dissertations

Alcohols represent an important class of functional group in organic synthesis and medicinal chemistry, given that they are structurally diverse and prevalent in many natural products, biomolecules and renewable feedstocks. As such, they are highly attractive precursors for building-block synthesis, late-stage functionalization, and numerous synthetic transformations. However, existing strategies for the deoxygenative diversification of alcohols operate under constrained conditions, often leading to competing pathways (such as elimination), poor stereospecificity, low efficiencies, and limited substrate compatibility. To address these challenges, we have developed a conceptually novel use of sulfonyl fluorides as bifunctional reagents for the one-step deoxygenative diversification of complex alcohol …

Liquid Chromatography-Mass Spectrometry Based Metabolomics, Lipidomics And Epitranscriptomics., Raobo Xu

Electronic Theses and Dissertations

Metabolomics and lipidomics are the comprehensive studies of metabolites and lipids in cells, biological fluids, tissues, or organisms. These distinct chemical fingerprints are left behind by cellular processes. Epitranscriptomics is the field that focuses on examining chemical modifications on RNA molecules at the transcriptome level. Liquid chromatography-mass spectrometry (LC-MS) has been widely used in those omics studies. In this dissertation, I developed and applied both untargeted and targeted approaches using LC-MS based various analytical platforms to conduct omics studies. Firstly, I investigated caffeine metabolites in human urine and discovered three potential functional biomarkers to differentiate the stages of alcohol-associated liver …

Nickel Electrocatalysts On Carbon Supports For The Hydrogen Evolution Reaction., Mohan Paudel

Electronic Theses and Dissertations

Hydrogen is an important energy storage alternative to fossil fuels due to its high energy density. Currently, most hydrogen is produced through petroleum feedstocks, which produce large amounts of carbon dioxide. However, a more eco-friendly method is the electrocatalytic splitting of water into hydrogen and oxygen. Efficient catalysts for the hydrogen evolution reaction (HER) are typically platinum group metals, which are rare and expensive. There is growing interest in developing HER electrocatalysts with earth-abundant metals for water electrolysis. Nickel, which lies in the same group in the periodic table as Pt and has similar chemical properties, is explored extensively for …

The Disordered Negatively Charged C-Terminus Of The Large Hect E3 Ubiquitin Ligase Herc2 Provides Structural And Thermal Stability To The Hect C-Lobe, Kelly L. Waters, Kayla J. Rich, Noah D. Schwaegerle, Tianyi Yang, Shuanghong Huo, Donald E. Spratt

Chemistry

Homologous to the C-terminus of E6AP (HECT) and RCC1-like domain (RLD)-containing protein 2 (HERC2) is a large, 528 kDa E3 ubiquitin ligase that is associated with cancer, oculocutaneous albanism type 2, Prader-Willi syndrome, and other neurological diseases. HERC2 has been found to contribute to double-stranded DNA break repairs, tumor suppression, maintaining centrosome architecture, and ubiquitylation. The C-terminal portion of the HECT domain (C-lobe) of HERC2 is responsible for transferring ubiquitin to a substrate but the precise function of the other eight domains in HERC2 are unknown. Interestingly, HERC2 contains a unique and negatively charged C-terminal …

Selective Hydroxyl Functionalization Using Novel Bifunctional Macrocyclic Catalysts And Sufex-Based Methodologies, Austin Seilkop

All Dissertations

The research behind this dissertation explores innovative strategies for the functionalization of alcohols. Alcohols are abundant in biologically relevant molecules and pharmaceutical drugs, so designing new methods for modifying them has gained significant interest over the years. The first and second chapters of this dissertation focus on the selective functionalization of a particular class of alcohols, amino alcohols, a well-represented functional handle in biomolecules. The hydroxyl functionalization of amino alcohols often demands multiple synthetic steps. We developed a new class of macrocyclic catalysts to enable precise and efficient transformations of amino alcohols, advancing the scope and efficiency of amino alcohol …

Hydrothermal Synthesis, Characterisation, And Magnetic Study Of First-Row Transition Metal Molybdates And First-Row Transition Metal Vanadates, Mahsa Foroughian Foroughian

All Dissertations

Growing high-quality single crystals of transitional metal oxides have been of interest over the last two centuries because of the many applications of these transparent materials in various industries, such as optics, magnetism, semiconductors, and batteries. During this period, a variety of crystal growth techniques have been utilized, each offering unique advantages and disadvantages to the solid-state community.

Traditionally, metal oxides such as molybdates and vanadates are produced using high-temperature techniques (700 to 1200 °C). These methods can cause oxygen to be expelled, resulting in the creation of lattice defects and lower-valence metal ions and complicate precise measurements of physical …