Physical Sciences and Mathematics Commons^™

Effect Of Elevated Atmospheric Carbon Dioxide Levels On Nodule Relative Efficiency In White Clover, J R. Crush, B D. Campbell, J.P M. Evans

IGC Proceedings (1993-2023)

Plant growth, total nitrogenase activity and hydrogen evolution rates were determined for 39-, 47- and 54-day-old white clover (Trifo/ium repe11s L.) plants growing at 350 or 700 ppm CO2 with day/night temperatures of 18/13°C or 28/23°C. The three plant parameters increased with plant age, temperature and CO2 concentration. Nitrogenase activity/g plant dry matter (DM) and hydrogen evolved/ g DM decreased as plants developed, presumably as nitrogen was cycled internally and plants became less reliant on recently fixed nitrogen. Nodule relative efficiency - an expression of the energy flux to nitrogenase relative to hydrogen production - was significantly lower initially in …

The Characterization And Electrochemistry Of Natural Uranium Dioxide Under Long-Term Disposal Conditions, Martin D. M. Badley

Electronic Thesis and Dissertation Repository

This thesis describes the studies performed on a number of natural uranium dioxide (UO₂) specimens to determine a range of reactivities. This work will support the safety case for the long-term disposal of spent nuclear fuel in Canada. Under relevant long-term disposal conditions, water radiolysis could produce oxidizing conditions at the surface of the fuel, potentially leading to fuel corrosion and the release of radionuclides into the groundwater. The rate of such a process would be determined by the radiation dose rate from the fuel and the reactivity of the fuel, which will be determined by its composition, …

Optimized Intermediate Layer Formation And Electroless Plating Methods To Obtain Supported Dense Pd Surfaces, Gamze Gümüşlü Gür, Berna Toprak

Turkish Journal of Chemistry

Dense metallic membranes, especially Pd and Pd alloys, have been intensely investigated to provide an alternative and economical way to obtain H2 with ultrahigh purity. To overcome the high cost of Pd, composite membrane structures that comprise a thin layer of Pd are utilized. However, it is a challenge to obtain a thin, dense, and uniform Pd layer on the support materials. This study investigates the parametric analysis of γ-Al2O3 interlayer formation and the electroless Pd plating (Pd ELP) procedures on α-Al2O3 supports with the aim to achieve a thin, uniform Pd surface without annealing. Adjustments in PEG/PVA concentration, dipping …

Palladium (0) Nanoparticles Distributed On Lanthanum (Iii) Oxide As An Effective Catalyst For The Methanolysis Of Hydrazine-Borane To Produce Hydrogen, Adem Rüzgar, Lokman Şener, Yaşar Karataş, Mehmet Gülcan

Turkish Journal of Chemistry

Pd (0) nanoparticles (NPs) distributed on lanthanum (III) oxide were ex situ generated from the reduction of Pd2+ ions using NaBH4 as reducing agent. The Pd/La2O3 displayed good catalytic activity in H2(g) releasing from the hydrazine-borane (HB) methanolysis reaction and it was identified by advanced techniques. Pd/La2O3 was found to be an active catalyst procuring three equiv. H2(g) per mole of HB. The results from TEM images represent the formation of Pd (0) NPs with an average particle size of 1.94 ± 0.1 nm on the surface of La2O3. Moreover, Pd/La2O3 with various Pd loadings were prepared and tested as …

Maximizing Charge Dynamics In Znin2s4/Cn Van Der Waals Heterojunction For Optimal Hydrogen Production From Photoreforming Of Glucose, Jinqiang Zhang, Xinyuan Xu, Lei Shi, Huayang Zhang, Shaobin Wang, Hongqi Sun

Research outputs 2022 to 2026

Biomass photoreforming stands out as a promising avenue for green hydrogen, leveraging solar energy for the generation and transformation of clean and renewable energy resources. The pursuit of efficient photocatalysts is motivated by the unsatisfied hydrogen evolution performance arising from the complex and stubborn structure of biomass. Herein, we loaded 2-dimensional (2D) ZnIn2S4 onto 2D carbon nitride nanosheets, resulting in the formation of Van der Waals (VDW) heterojunctions (ZIS/CN). Band structure and morphology of CN were rationally tailored through precursor engineering to effectively magnify interfacial internal electric field and minimize diffusion pathway within the VDW heterostructure, realizing optimal charge dynamics …

The Effect Of Mechanical Strain On The Electronic Conductivity Of Α- Fe2o3: A Density Functional Theory Study, Sheriff Naziru Abdulmutalib

Theses and Dissertations

Hydrogen has emerged as a promising future energy carrier due to its ability to produce zero carbon dioxide (CO2) emissions when burned. However, the limited natural abundance of hydrogen necessitates the development of cost-effective and environmentally friendly methods for large-scale hydrogen production. Among the different hydrogen production approaches, photoelectrochemical water splitting, which employs a photoanode material in a cell using solar energy to split water into hydrogen and oxygen, is the focus of this work. α-Fe2O3 (hematite) is a photoanode material that shows a promising future for hydrogen generation in a photoelectrochemical cells due to its cheapness, availability, and its …

Experimental Investigation On Hydrogen-Rich Syngas Production Via Gasification Of Common Wood Pellet In Bangladesh: Optimization, Mathematical Modeling, And Techno-Econo-Environmental Feasibility Studies, Md Sanowar Hossain, Mujahidul Islam Riad, Showmitro Bhowmik, Barun K. Das

Research outputs 2022 to 2026

Since hydrogen produces no emissions, there is increasing interest in its production throughout the world as the need for clean and sustainable energy grows. Bangladesh has an abundance of biomass, particularly wood pellets, which presents a huge opportunity for gasification to produce hydrogen. Gasification of mahogany (Swietenia mahagoni-SM) and mango (Mangifera indica-MI) wood is performed in a downdraft gasifier to evaluate the impact of particle size, equivalence ratio, and temperature on hydrogen gas composition and gasifier performance. Under the optimal conditions determined by central composite design-response surface methodology (CCD-RSM) optimization, gasification of SM and MI wood can greatly increase hydrogen …

Substituent Effects And Mechanistic Insights On The Catalytic Activities Of (Tetraarylcyclopentadienone)Iron Carbonyl Compounds In Transfer Hydrogenations And Dehydrogenations, Bryn K. Werley, Xintong Hou, Evan P. Bertonazzi, Anthony Chianese, Timothy W. Funk

Chemistry Faculty Publications

(Cyclopentadienone)iron carbonyl compounds are catalytically active in carbonyl/imine reductions, alcohol oxidations, and borrowing hydrogen reactions, but the effect of cyclopentadienone electronics on their activity is not well established. A series of (tetraarylcyclopentadienone)iron tricarbonyl compounds with varied electron densities on the cyclopentadienone were prepared, and their activities in transfer hydrogenations and dehydrogenations were explored. Additionally, mechanistic studies, including kinetic isotope effect experiments and modifications to substrate electronics, were undertaken to gain insights into catalyst resting states and turnover-limiting steps of these reactions. As the cyclopentadienone electron density increased, both the transfer hydrogenation and dehydrogenation rates increased. A catalytically relevant, trimethylamine-ligated iron …

Bulk Hydrogen Isotopes In Ordinary Chondrites, Michael J. Cato

Earth and Planetary Sciences ETDs

Bulk hydrogen isotopes in nominally anhydrous meteorites are a key component in our understanding of the distribution of hydrogen in our solar system, including the provenance of water on the Earth. Here, we develop a step-heated continuous-flow method to measure the bulk hydrogen isotopes in nominally anhydrous rocks and use this method to significantly increase the dataset of bulk hydrogen isotopes in ordinary chondrites, nearly doubling the number of equilibrated members. We found that as thermal alteration increases from petrologic type 3.0 to 4, there is a correlated decrease in both hydrogen content and isotope ratio, followed by no significant …

Optimizing Photosystem I And Plastocyanin Isolation To Develop A Photosystem I-Catalyst System For Photochemical Hydrogen Production, Angelina Vuong

Honors Program Theses and Projects

Over the course of many years, greenhouse gases such as carbon dioxide (CO2) and methane (CH4) have formed in large amounts in the atmosphere, which has contributed to global warming. Global warming can lead to extreme weather conditions or have an impact on living organisms, for example, wildfires, droughts, limited amount of food sources, and respiratory issues from pollution. This is mainly due to the use of burning fossil fuel as an energy source, which emits greenhouse gases into the air and traps heat into the atmosphere. Thus, the aim of this study is to assemble and characterize a system …

Ambient Ammonia Synthesis Via Microwave-Catalytic Materials And Plasma Chemistry, Siobhan Brown

Graduate Theses, Dissertations, and Problem Reports

Ammonia is critical to supporting human life on earth because of its use as fertilizer. The Haber-Bosch process to produce ammonia has been practiced for over 100 years. This process operates at high pressure and temperature to overcome the thermodynamic and kinetic limitations of the ammonia synthesis reaction thus researchers have tried to overcome it for decades. At present this process represents 1% of global energy usage and 2.5% of global CO₂ emissions. The proposed chemical looping ammonia synthesis approach seeks to reduce the environmental impact of this critical process and to elucidate microwave-catalytic principles.

This research aims to …

Synthesis And Processing Of Polymeric Materials For Hydrogen Storage, Dominic Adrewie

Theses and Dissertations

Hydrogen is one of the most promising alternatives and clean fuel sources, but it has faced several hurdles due to storage and transportation issues. Several methods have been proposed, developed, and are being improved. Key among these is the use of polymers as safe hydrogen storage media.

This work investigated the polymerization of methyl vinyl ketone using different concentrations 2,2’-Azobis(2-methylpropionitrile) as the initiator in a free radical polymerization mechanism. There was a subsequent analysis of the effect of the initiator concentration on the conversion rate and the molecular weight of the polymers produced with the help of Gel permeation chromatography. …

Transistion Metal Chalcogenides And Phosphides For Energy Storage And Conversion Through Water Splitting, Kelsey Thompson

Electronic Theses & Dissertations

In contemporary society, there are many different ways that energy is used in daily life. From applications that require a high energy density to long-term storage in a stable manner, the requirements for energy usage are diverse. Therefore, the greater the number of uses a designed material exhibits, the more practical it may be for wide-scale manufacture. Two areas of particular interest for energy applications are fuel cells (to generate energy) and supercapacitors (to store energy). To provide cheaper and more durable alternatives for energy storage, electrodes containing CoMoO₄, NiMoO₄, CoMoS₄, NiMoS₄, …

Identifying The Isotopic Signature Of Lake-Effect Precipitation In Shallow Groundwater, Andrew Brown

Honors Projects

Three different stable isotopes of water occur in nature, with the majority of water on Earth containing the oxygen isotope 16O. These isotopes have slightly differing physical and chemical properties. H2O with heavier oxygen isotopes should theoretically precipitate earlier than lighter isotope H2O, meaning this natural process should allow for the observation of the magnitude of effects of lake-effect precipitation on the basis of water isotope differences. Furthermore, it may allow for better understanding of the significance lake-effect precipitation plays in recharging shallow aquifers. In this study, patterns of lake-effect precipitation from Lake Michigan were observed in a collection of …

Hydrogen Technologies, University Of North Dakota. Energy And Environmental Research Center

EERC Brochures and Fact Sheets

Fact sheet about hydrogen technology and the Energy & Environmental Research Center’s (EERC’s) National Center for Hydrogen Technology (NCHT). Includes information about hydrogen as an energy and fuel source and past EERC hydrogen projects.

The Potential Of Diabase Sills In Eastern Pennsylvania To Store Co2 And H2, Rhiannon R. Schmitt

Graduate Theses, Dissertations, and Problem Reports

With anthropogenic CO₂ concentrations rising, geologic carbon sequestration and H₂ storage are essential processes in mitigating climate change. Typical geologic carbon sequestration involves the capture of anthropogenic CO₂ and injection into depleted oil/gas reservoirs or saline formations with an impermeable cap rock to prevent the buoyant migration of CO₂. The risk of eventual CO₂ migration through these low permeability cap rocks adds expensive monitoring costs to this traditional sequestration strategy. Another method for CO₂ sequestration utilizes the reaction of CO₂ with mafic and ultramafic rocks. CarbFix, a sequestration project in Iceland, has …

Hydrogen/Deuterium Exchange Measurements May Provide An Incomplete View Of Protein Dynamics: A Case Study On Cytochrome, Pablo M Scrosati, Victor Yin, Lars Konermann

Chemistry Publications

Many aspects of protein function rely on conformational fluctuations. Hydrogen/deuterium exchange (HDX) mass spectrometry (MS) provides a window into these dynamics. Despite the widespread use of HDX-MS, it remains unclear whether this technique provides a truly comprehensive view of protein dynamics. HDX is mediated by H-bond-opening/closing events, implying that HDX methods provide an H-bond-centric view. This raises the question if there could be fluctuations that leave the H-bond network unaffected, thereby rendering them undetectable by HDX-MS. We explore this issue in experiments on cytochrome

Synthesis, Characterization, And Catalytic Activity Of Functionalized Metal Bis(Thiosemicarbazones)., Caleb Aaron Calvary

Electronic Theses and Dissertations

Bis-(thiosemicarbazones) are a class of ligands that have found a wide range of uses from electrocatalysts to medicinal and diagnostic reagents. These ligands contain a diimine backbone, N₂S₂ chelating core, and pendent amines. In order to further explore this class of ligands, the previously underreported transamination reaction, which exchanges one pendent amine group for another, was utilized to create several derivatives using aliphatic and aromatic amines. The transamination reaction is appealing alternative to making the desired thiosemicarbazide. Further appeals come from the fact that it is a one-pot reaction that gives highly pure products in good yields. …

A Theoretical Study Of Synchronous Proton Transfer In (Hf)N, (H2O) N, And (Hcl) N Where N = 3, 4, 5, Johnny Yang

Honors Theses

For (HF)_n, (H₂O)_n, and (HCl)_n (n = 3 − 5), we have rigorously characterized the structures for the minima and transition states for synchronous proton transfer (SPT) with the CCSD(T) method and aug-cc-pVTZ basis set. The electronic barrier heights (∆E^†) associated with these transition states have also been computed with the explicitly correlated CCSD(T)-F12 method and the aug-cc-pVQZ-F12 basis set (abbreviated aQZ-F12). (HCl)_n (n = 3 − 5) SPT transition states have not been previously identified to the best of our knowledge, and they have been found …

Determination Of The Rydberg Constant From The Emission Spectra Of H And He+, Kyle D. Shaffer

Ramifications

Abstract

In this experiment, the Rydberg constants for the hydrogen atom and He⁺ were determined by analysis of the emission spectra of Hand He, respectively, in comparison to the principal quantum numbers of each transition. Using both a hydrogen and then a helium atomic lamp attached to a 0.5 m grating spectrometer and a photomultiplier detector (PMT), a change in voltage detected by the PMT can be paired with a corresponding wavelength passing through the spectrometer from each emission peak in the visible to ultraviolet range. The peaks acquired from this change in voltage were analyzed to find their …

Accelerated Fe$^{Iii}$/Fe$^{Ii}$ Redox Cycle Of Fenton Reaction System Using Pd/Nh$_{2}$-Mil-101(Cr)And Hydrogen, Zhong-Xing Liu, Xin Liu, Yong Li, Shi-Qian Gao

Turkish Journal of Chemistry

In this paper, a novel improvement in the catalytic Fenton reaction system named MHACF-NH$_{2}$-MIL-101(Cr) was constructed based on H$_{2}$ and Pd/NH$_{2}$-MIL-101(Cr). The improved system would result in an accelerated reduction in Fe$^{III}$, and provide a continuous and fast degradation efficiency of the 10 mg L$^{-1}$ 4-chlorophenol which was the model contaminant by using only trace level Fe$^{II}$. The activity of Pd/NH$_{2}$-MIL-101(Cr) decreased from 100% to about 35% gradually during the six consecutive reaction cycles of 18 h. That could be attributed to the irreversible structural damage of NH$_{2}$-MIL-101(Cr). Key words:

Vibration Overtone Hyperpolarizability Measured For H2 Using Electric Field Induced Second Harmonic Generation, Rachel Ellis

UNLV Theses, Dissertations, Professional Papers, and Capstones

The vibrational contribution to the second hyperpolarizability (γ) of gas phase H2 was measured using electric field induced second harmonic generation. Measurements were made for the pure vibrational 3-0 Q(J) overtone transitions (v=0,J → v’=3,J for J = 0,1,2,3). Measured intensities were found to be 4-14% larger than ab initio calculations. The first chapter of this thesis provides an introduction to nonlinear optics, second harmonic generation, and the tensor nature of hyperpolarizabilities. The second chapter provides theoretical expressions for γ and relevant static and Raman polarizabilities. The third chapter covers the experimental design and electric field induced second harmonic generation. …

Impact Of Interlayer Cation Composition And Strongly Bound Water On Smectite ẟ²H, As Determined By A Modified Tcea Method, Nadine J. Kanik

Electronic Thesis and Dissertation Repository

Interlayer cation composition and cation hydration enthalpy can potentially affect the excess hydrogen-yield and δ²H of smectitic clays. Complexities arise from condensed atmospheric water adsorbed on the clay, as it constitutes a potential additional source of hydrogen when attempting to measure the δ²H of structural OH groups. To approach this problem, the δ²H of different cation-saturated, dried forms of six Clay Minerals Society Source Clay smectites were measured. A modified sample drying and on-line High-Temperature-Conversion-Elemental-Analysis (TCEA) Continuous-Flow-Isotope-Ratio-Mass-Spectrometry protocol, facilitated isotopic measurements. A stronger interlayer cation hydration enthalpy (Ca²⁺>Na⁺>K⁺), …

Non-Conventional Vehicles As A Way Towards Carbon Neutrality In Iceland, Julia Sokolowska

Independent Study Project (ISP) Collection

Paris Agreement’s chief objective is to protect the Earth and its inhabitants from a point of no return, when the effects of climate change will be so intense that they will shift the equilibrium of ecosystems. The distinctiveness of this international environmental treaty is that it does not impose climate change mitigation measures, but rather allows nation states to create their own set of measures, the NDCs, to reach the global warming of ‘well below 2oC’ by the end of the century. Thus, Iceland has submitted its own NDC, the Climate Action Plan 2018-2030, which has an ambitious goal of …

Composite Zeolite Beta Catalysts For Catalytic Hydrocracking Of Plastic Waste To Liquid Fuels, Dureem Munir, Hassaan Amer, Rabya Aslam, Mohamed Bououdina, Muhammad Rashid Usman

Publications and Scholarship

Abstract The conversion of model waste plastic mixture into high-value liquid product was studied in the presence of hydrogen and composites of zeolite beta catalysts. For the sake of comparison, the conversion of actual waste plastic mixture and high-density polyethylene was also carried out. The composite zeolite beta catalysts were synthesized using a range of silica-to-alumina ratios, alkali concentrations, and hydrothermal treatment times. SEM, EDX, XRD, N2-BET, FTIR, and py-FTIR were used for the characterization of the catalysts. The catalytic experiments were conducted in a 500 ml stirred batch reactor at 20 bar initial cold H2 pressure and the temperature …

High-Pressure Studies On The Transition From Red Phosphorus To Black Phosphorus, Heng Xiang

Electronic Thesis and Dissertation Repository

Black phosphorus (BP) is a promising material in many research fields. However, the transition process from amorphous red phosphorus (ARP) is elusive and hence hinders large scale synthesis and applications. This work describes the application of the high-pressure method to study the transition process from ARP to BP.

In this thesis, the following three objectives were achieved: (1) to understand the mechanism of the transition, (2) to facilitate the synthesis of BP by taking the advantage of less pure ARP, (3) to propose new methods of synthesizing BP-based materials, such as the moderately oxidized BP and the black phosphorus/ amorphous …

Synthesis And Connection Of Iridium Hydrogen Evolution Catalyst To Chlorella Vulgaris Photosystem I For Light-Driven Hydrogen Evolution, Anna Ramirez

Honors Program Theses and Projects

Hydrogen gas has been shown to be a promising energy source as options other than fossil fuels are being looked at in the face of anthropogenic climate change. It is known that anthropogenic climate change is caused by the production of greenhouse gases being let into the atmosphere, specifically a common reason for this is the burning of fossil fuels for energy. The overall goal of this project is to design a biochemical hybrid system that will be used to make H 2 gas and does not require the use of fossil fuels. Burning hydrogen as fuel produces only water …

Studying Near-Critical And Super-Critical Fluids In Reduced Gravity, Christian Hawkins, Ana Oprisan, Carole Lecoutre-Chabot, Yves Garrabos, Daniel Beysens

Journal of the South Carolina Academy of Science

Critical and supercritical fluids have a variety of applications, from use as machine lubricants in high pressure or high temperature environments to the manufacturing of materials such as aerogel. The optical properties of fluids undergo rapid changes near the critical point resulting in a rapid increase in turbidity known as critical opalescence. These optical changes can be used to probe the universality of critical behavior. As a fluid approaches the critical point, the compressibility rapidly increases. In a gravitational field, this increase in compressibility leads to near-critical fluids stratifying by phase and density, making it difficult to observe the optical …

Growth Kinetics, Carbon Isotope Fractionation, And Gene Expression In The Hyperthermophile Methanocaldococcus Jannaschii During Hydrogen-Limited Growth And Interspecies Hydrogen Transfer, Begüm D. Topçuog˘ Lu, Cem Meydan, Tran B. Nguyen, Susan Q. Lang, James F. Holden

Faculty Publications

Hyperthermophilic methanogens are often H2 limited in hot subseafloor environments, and their survival may be due in part to physiological adaptations to low H2 conditions and interspecies H2 transfer. The hyperthermophilic methanogen Methanocaldococcus jannaschii was grown in monoculture at high (80 to 83 M) and low (15 to 27 M) aqueous H2 concentrations and in coculture with the hyperthermophilic H2 producer Thermococcus paralvinellae. The purpose was to measure changes in growth and CH4 production kinetics, CH4 fractionation, and gene expression in M. jannaschii with changes in H2 flux. Growth and cell-specific CH4 production rates of M. jannaschii decreased with decreasing …

Semiclassically Modeling Hydrogen At Rydberg States Immersed In Electromagnetic Fields, Jaron Williams

Mathematics Senior Capstone Papers

Originally, closed-orbit theory was developed in order to analyze oscillations in the near ionization threshold (Rydberg) densities of states for atoms in strong external electric and magnetic fields. Oscillations in the density of states were ascribed to classical orbits that began and ended near the atom. In essence, observed outgoing waves following the classical path return and interfere with original outgoing waves, giving rise to oscillations. Elastic scattering from one closed orbit to another gives additional oscillations in the cross-section. This study examines how quantum theory can be properly used in combination with classical orbit theory in order to study …