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Synthesis Of Mn-Based Transition Metal Phosphide Nanoparticles And Evaluation Of Their Activity As Pre-Catalysts For Electrocatalytic Water Oxidation And Magnetic Applications
No full textIn this dissertation, Ni2-xMnxP (0.0≤x≤1.5) nanoparticles have been synthesized for the first time using the arrested precipitation technique. This synthesis is based on the formation of a nickel phosphide amorphous phase followed by the incorporation of manganese in the next step. Manganese oxide as a byproduct of this reaction can be separated from Ni2-xMnxP (0.0≤x≤1.5) nanoparticles using a new technique. In this strategy, a mixture of oleic acid/water was added to as-synthesized nanoparticles dispersed in hexane. Manganese oxide nanoparticles can be transferred to the water phase while Ni2-xMnxP nanoparticles remain in hexane. Using this method, Ni2-xMnxP can be synthesized up to x=1.5. Purified Ni2-xMnxP (0.0 ≤ x ≤1.5) nanoparticles have been tested as electrocatalysts for the oxygen evolution reaction (OER) process, and different parameters, including geometric and intrinsic activities, stability, and faradiac efficiency have been evaluated for this system. Compared to the most active compositions in Fe2−xMnxP (x ≤ 0.9) and Co2−xMnxP (x ≤ 1.4), the NiMnP precatalyst resulted in the highest OER activity with a geometric overpotential of 280.0 mV at 10 mA/cm2 relative to 302.5 mV for CoMnP and 350.0 mV for Fe1.1Mn0.9P. Magnetic properties of CoMnP and NiMnP nanoparticles have been investigated using an MPMS3 instrument, and different magnetic parameters of these systems were measured. The behavior of as-synthesized CoMnP nanoparticles is not consistent with the bulk system, but upon heating the nanoparticles to 450 °C they follow the magnetic properties of the bulk system. NiMnP nanoparticles exhibit paramagnetism behavior with a small Weiss constant, consistent with antiferromagnetic exchange at low temperature
Volatility Spillover Across Energy Markets
No full textThis study examines price volatility spillovers between two major world crude oil benchmarks, WTI and Brent, as well as between WTI and its refinery products using daily data from 1987 to 2023. The analysis focuses on two key phenomena: the financialization of commodity markets and the fracking revolution. To capture these dynamics, the study employs two models: the BEKK-GARCH model by Engle and Kroner (1995) and the D-Y volatility index by Diebold and Yilmaz (2009, 2012). Findings reveal that both phenomena significantly influence the direction and magnitude of volatility spillovers between these markets. Specifically, results from the D-Y index show that financialization reversed the spillover direction. During the pre-financialization period, WTI acted as a net sender of volatility while Brent was the net receiver, a relationship that flipped in the post-financialization era. Additionally, we checked volatility spillover between WTI and its by-products in the United States. The results show that the heating oil market is the primary sender of volatility to WTI and gasoline markets in all sample sub-periods
Nonlinear Dynamics And Control Of An Autonomously Operated Towed System
No full textEmergency towing vessels are a vital component of maritime safety. This study works to improve on previous works in the area of automating the towing of disabled ships. In doing so control methods for transient three degree of freedom dynamics of a tug and tow system which is connected with a finite element cable are evaluated. A Heaviside unit step function is inserted to void both the elastic and viscous interaction between the massive elements whenever the distance between two neighboring masses appears to be below the corresponding undeformed distance. This follows the representation of the cable as a one-dimensional structure whose segments cannot hold compressive deformations. The system is influenced by environmental forces which include sea current and wind. The control strategies utilize two different error signals that pass through a PID controller. The first phase evaluates a tension control error which incorporates the tension in the segment attached to the tug and the desired tension signal which follows an underdamped second order linearly damped oscillator profile up to an initial desired speed. The second control phase evaluates two different methods of velocity control. The first method uses the speed of the tug in comparison to a smooth desired speed function that ramps up from the initial desired speed to a defined cruising speed while also evaluating the tension in the segment attached to the tug. In doing so the segment tension is passed through a smooth sigmoidal function that evaluates the tension with respect to the desired segment tension. The output of this function increases or decreases the desired velocity of the tug to either protect the cable or increase cruising speed. The second method utilizes a weighted control error which sways the control signal between tracking and tension control to prevent the cable from over tensioning. The tension controller reduces the tension spikes in the cable while maintaining optimal control of the ensemble. The tension zoning velocity controller is effective at mitigating rises in tension at the cost of speed during increased resistance time periods. The weighted control error is effective at maintaining desired speeds while incorporating a tension failsafe in the event of excessive tension. The results show the effectiveness of tension control and the incorporation of this in the tracking control phase as well as the ability to maintain controllability in the event of tension loss
Regulation Of Respiratory Supercomplexes Through Inhibitory Cytochrome C Oxidase Y304 Phosphorylation Causes Mitochondrial Dysfunction In Diabetic Heart
No full textCytochrome c Oxidase (CcO) is the terminal enzyme of the electron transport chain in mammals and is subject to tight regulation. We here analyzed heart mitochondria from Cohen diabetes-resistant (CDr) and diabetes-sensitive (CDs) rats, a model for type 2 diabetes. We uncovered a specific inhibitory phosphorylation at tyrosine 304 on the catalytic subunit I of CcO (pY304-CcO-I) induced by a high-sucrose diet in CDr and CDs rats. This phosphorylation is found in dimeric CcO and, for the first time, in a specific subset of respiratory supercomplexes (SCs), which is linked to increased tissue inflammation and reduced CcO activity, causing mitochondrial impairment and contributing to overall metabolic dysfunction. We propose that CcO enzymatic activity in dimeric CcO and specific CcO-associated SCs is regulated through Y304-CcO-I phosphorylation, leading to enzyme inhibition, redistribution of SCs, and diminished mitochondrial quality control. These results suggest that the combination of genetic predisposition to diabetes and high-sucrose diet is most detrimental to cardiac health
The Impact Of Pbl On The Academic And Linguistic Development Of English Language Learners In A High School Science Classroom
No full textThe dissertation examines the effects of Project-Based Learning (PBL) on the development of the English Language Learners (ELLs) in the high school science classroom. The increasing need for better teaching methods makes this study important. It explores how PBL improves language learning, scientific knowledge, and academic performance compared to traditional methods. The study includes two groups: Group A learned through PBL, while Group B used traditional teaching.
The research measures students\u27 language skills, engagement, critical thinking, and understanding of scientific concepts. The study collected pre- and post-assessment data using tests, classroom observations, and student reflections. The PSAT exam scores were also analyzed to check if PBL improves academic results. The findings show that PBL students improved more in science and language skills than in traditional classrooms. They showed greater engagement, stronger problem-solving skills, and better communication in written as well as spoken English.
The study also highlights how teamwork builds student confidence and participation in a learning environment. Hands-on projects helped ELLs connect science concepts to real life, making learning clearer and easier. The results suggest that PBL helps students think deeply, remember information longer, and achieve better academic success. The PSAT results showed that the PBL group performed better, supporting the idea that modern teaching methods help ELLs more than traditional ones.
Research has important lessons for teachers, education leaders, as well as curriculum planners. By proving that PBL is effective, this study encourages a shift from memorization to active, student-centered learning. The findings suggest that PBL not only helps language development but also teaches key 21st-century skills for future success. Future studies should examine PBL’s long-term effects in different subjects and student groups to further confirm its benefits for ELLs
New Insights Into The Control Of The Bacterial Translation Initiation Machinery
No full textNEW INSIGHT INTO THE CONTROL OF THE BACTERIAL TRANSLATION INITIATION MACHINERY
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AISHWARYA GHOSH April 2025 Advisors: Dr. Jared Schrader Major: Biological Sciences Degree: Doctor of Philosophy In the central dogma of bacteria, translation initiation plays a crucial role in regulating the flow of genetic information into functional proteins. Traditionally, this process has been understood through the Shine-Dalgarno (SD) model, which describes the interaction between mRNA and the ribosome to ensure accurate translation initiation. While the SD model is well-established concept, the mechanisms regulating translation initiation beyond this model, particularly in bacteria like Caulobacter crescentus, which lack SD sites, remain unclear. Furthermore, although it is known that bacteria can survive and adapt to low temperatures, the precise molecular mechanisms behind this adaptation are not fully understood. Environmental factors, such as temperature, can impact the secondary structure of mRNA, but the connection between these factors requires further investigation. Here, I uncover new insights into translation initiation in C. crescentus, revealing that start codon selection is dictated by mRNA secondary structures, with optimal SD spacing further enhancing efficiency when mRNA structures permit ribosomal accessibility. Also, I identify the N-terminal intrinsically disordered region (IDR) of translation initiation factor IF2 as a key player in bacterial adaptation to cold shock. Our findings show that the N-terminal IDR of IF2 promotes phase separation in response to cold shock, enhancing bacterial fitness under low-temperature conditions. Our studies reveal that translation initiation in C. crescentus is regulated by mRNA secondary structures, and the presence of Shine-Dalgarno sequence boost translation initiation efficiency. Additionally, we observe that the formation of IF2 condensates is reversible, suggesting that these condensates are dynamic structures rather than aggregates. Bioinformatics analyses reveal that the N-terminal IDR in bacterial IF2 proteins is conserved across various bacterial species. These condensates could serve as functional analogs of eukaryotic stress granules, which are known to organize cellular stress responses. The insights gained from this work have profound implications not only for our understanding of translation regulation but also for bacterial stress adaptation. Additionally, it discovers a new type of condensate within the bacterial central dogma, contributing to our knowledge of how bacterial cells organize and regulate the biochemical processes. Our findings highlight the potential of bacterial condensates, specifically IF2 condensates, as novel therapeutic targets for the development of antibiotics aimed at combating the worldwide issue of antibiotic resistance in pathogenic bacteria
Structural Impacts Of Canonical And Non-Canonical Oligonucleotide Modifications
No full textNucleic acids, including DNA (deoxyribonucleic acid) and RNA (ribonucleic acids), are the fundamental building blocks of living organisms. The events that cause modification of DNA/RNA are of interest because they impact the nucleic acid function. Targeting DNA is important for treating diseases such as cancer. Cisplatin (cisPt) is a well-studied drug that targets DNA and blocks replication, but its use is limited by adverse side effects and cellular resistance. Prevoius research addressed some of these challenges through development of platinum analogues such as carboplatin and oxaliplatin. Amino acid-linked platinum analogues (AAPt) are the focus of this thesis work. AAPt complexes are synthesized using amino acids as the non-labile ligands. Previous work suggested that using positively charged amino acids such as arginine and ornithine as the ligands could have benefits such as enhanced interactions with DNA. In fact, one AAPt was shown to have good antiproliferative activity against a prostate cancer cell line with reduced activity against a normal prostate cancer cell line. These studies were the motivations to study the L-argPt and L-ornPt complexes. Moreover, the isomeric versions, D-argPt and D-ornPt, were synthesized and compared 152 with the L versions. A total of four cisPt analogues (collectively referred to as AAPt complexes) were examined in this thesis work. The antitumor properties of cisPt are related to DNA adduct formation. DNA adducts affect the structural properties of DNA, such as creating bends. Chapter 2 of the thesis, focuses on DNAs with adducts of the four AAPt complexes. The adducts were characterized by polyacrylamide gel electrophoresis and matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry. AAPt complexes form DNA adducts at dGpG, dApG, dGpA, and dApA sites. Among these sites dGpA and dApA adducts were largely ignored in the past. The bend angles of DNAs containing these adducts were determined using gel mobility assays and compared with the bends created by cisPt-DNA adducts. The bend angle of a GG-containing DNA was calculated to be 30° with a cisPt adduct and 37° with AAPt (L-argPt, D-argPt, L-ornPt, and D-ornPt) adducts. The bend angles for AG-containing DNA with cisPt and AAPt adducts were similar (28° and 30°, respectively). The bend angles for GA- and AA-containing DNAs and cisPt or AAPt adducts were 29° and 22°, respectively. For both cisPt and AAPt, the DNA bend angles were adduct dependent, with decreasing bending in the following order: dGpG≥ dApG≈dGpA\u3edApA for cisPt and dGpG\u3edApG≈dGpA\u3edApA for AAPt DNA adducts. Reaction kinetics are an important pharmacological factor for a drug to be considered for clinical use. In Chapter 3, the reaction kinetics were examined for AAPt-DNA interactions. The studies were conducted on single-stranded DNAs containing three different adduct sites (dGpG, dApG, or dApA) and four AAPt analogues. The reaction kinetics were determined using DNA with one major adduct site and the adduct formation was monitored by gel electrophoresis. Pseudo-first order conditions were employed with excess metal complex. The reaction rates of AAPt complexes and cisPt were compared with prior studies that employed other methods such as HPLC or NMR spectroscopy. This study showed that GG-containing DNA has the highest rate of reaction with cisPt. 153 The trend for reaction rate for cisPt is GG\u3eAA\u3eAG DNA. The trends for the AAPt complexes varied as follows: 1) L-argPt, GG\u3eAA≈AG DNA; 2) D-argPt, GG≈AG≈AA DNA; 3) L-ornPt, AG\u3eAA≈GG DNA; and 4) D-ornPt, GG≈AG≈AA DNA. Canonical RNA modifications, such as 2′-O-methyl guanosine (Gm) and pseudouridine (), are involved in various roles in regulating RNA stability, transcription, and translation.145, 319 RNA oxidative damage caused by ROS is considered a significant factor in cellular dysfunction and disease.265 In Chapter 4, the roles of Gm and in mediating oxidative stress were examined. By using radiolabeled RNA gel electrophoresis was employed to examine oxidative damage of modified RNAs and compared to unmodified RNAs. RNA sequencing techniques such as alkaline hydrolysis, chemical sequencing, and enzymatic sequencing (RNase T1) were used to map the locations of the modified sites in the RNA. The Gm-modified sites (Gm5 and Gm6) showed altered fragmentation after three different reaction times (10, 30, and 60 minutes) with the Fenton reagent which generates reactive oxygen species. Furthermore, an altered fragmentation pattern was observed at the modification site after 30 and 60 minutes of the Fenton reaction but not for the 10-minute reaction time. These results show that the Gm and modifications could have roles in mediating oxidative damage of RNA
Advanced Lanthanide Probes For Magnetic Resonance Imaging And Computational Modeling
No full textThis thesis is a collection of six chapters that describes a combination of experimental and literature analyses into the field of lanthanide coordination chemistry, with emphasis on medical imaging and computational analysis. The first chapter summarizes the following chapters. The second and third chapters describe the design, characterization, and analysis of lanthanide-containing contrast agents for use with magnetic resonance imaging. The fourth chapter is a detailed overview of the current state of targeted contrast agents for use with magnetic resonance imaging. The fifth chapter describes the design, characterization, and analysis of photoluminescent catalysts with an emphasis on the computational analyses of two complexes of divalent europium. The final chapter summarizes important results and discussions from the previous chapters while also providing future directions for the studies
