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Articles 481 - 510 of 759
Full-Text Articles in Chemical Engineering
Foundational Work In Bioelectrochemical Anaerobic Reactor Design With Electron Mediators, Christopher D. Hoeger
Foundational Work In Bioelectrochemical Anaerobic Reactor Design With Electron Mediators, Christopher D. Hoeger
Theses and Dissertations
Bioelectrical reactors (BER) have potential to be utilized in a wide variety of industrial applications. This work explores the kinetics involved with reduction of electron mediators (anthraquinone disulfonate and methyl viologen) in bioelectrical reactors. It also discusses on possible application of BER technology to produce ethanol from CO2 and electricity. It is established that Clostridium ragdahlei is capable of sustaining life and product formation with CO2 as the only carbon source. This means it is theoretically possible to utilize CO2 as he source of carbon and electricity as the source of reducing equivalents for bacterial growth and product formation. A …
Immobilized Viologen Polymer For Use In Direct Carbohydrate Fuel Cells, Yining Pan
Immobilized Viologen Polymer For Use In Direct Carbohydrate Fuel Cells, Yining Pan
Theses and Dissertations
Glucose and other carbohydrates are some of the most abundant renewable energy sources in the world. The oxidation of carbohydrates in a fuel cell allows their chemical energy to be converted directly into electrical energy. Viologen has been indentified and shows promising ability as an electron-transfer catalyst or mediator for carbohydrate oxidation in an alkaline carbohydrate fuel cell. Building on the previous results, the objective of this work was to develop an immobilization chemistry of viologen onto an electrode and to investigate the catalytic activity for carbohydrate oxidation in direct carbohydrate fuel cells.The immobilization was achieved by electropolymerizing a novel …
Application Of Fuel Element Combustion Properties To A Semi-Empirical Flame Propagation Model For Live Wildland Utah Shrubs, Chen Shen
Theses and Dissertations
Current field models for wildfire prediction are mostly based on dry or low-moisture fuel combustion research. To better study live fuel combustion behavior and develop the current semi-empirical bush combustion model, a laminar flow flat-flame burner was used to provide a convection heating source to ignite individual live fuel samples. In this research project, four Utah species were studied: Gambel oak (Quercus gambelii), canyon maple (Acer grandidentatum), big sagebrush (Artemisia tridentata) and Utah juniper (Juniperus osteosperma). Leaf geometrical parameters and time-dependent combustion behavior were recorded. Qualitative results included various combustion phenomena like bursting, brand formation and bending. Quantitative results included …
Protein-Surface Interactions With Coarse-Grain Simulation Methods, Shuai Wei
Protein-Surface Interactions With Coarse-Grain Simulation Methods, Shuai Wei
Theses and Dissertations
The interaction of proteins with surfaces is a major process involved in protein microarrays. Understanding protein-surface interactions is key to improving the performance of protein microarrays, but current understanding of the behavior of proteins on surfaces is lacking. Prevailing theories on the subject, which suggest that proteins should be stabilized when tethered to surfaces, do not explain the experimentally observed fact that proteins are often denatured on surfaces. This document outlines several studies done to develop a model which is capable of predicting the stabilization and destabilization of proteins tethered to surfaces. As the start point of the research, part …
Entropic Depletion Of Dna In Triangular Nanochannels, Wesley F. Reinhart, Douglas R. Tree, Kevin D. Dorfman
Entropic Depletion Of Dna In Triangular Nanochannels, Wesley F. Reinhart, Douglas R. Tree, Kevin D. Dorfman
Faculty Publications
Using Monte Carlo simulations of a touching-bead model of double-stranded DNA, we show that DNA extension is enhanced in isosceles triangular nanochannels (relative to a circular nanochannel of the same effective size) due to entropic depletion in the channel corners. The extent of the enhanced extension depends non-monotonically on both the accessible area of the nanochannel and the apex angle of the triangle. We also develop a metric to quantify the extent of entropic depletion, thereby collapsing the extension data for circular, square, and various triangular nanochannels onto a single master curve for channel sizes in the transition between the …
A Steady-State Detection (Ssd) Algorithm To Detect Non-Stationary Drifts In Processes, Jeff Kelly, John Hedengren
A Steady-State Detection (Ssd) Algorithm To Detect Non-Stationary Drifts In Processes, Jeff Kelly, John Hedengren
Faculty Publications
Detecting windows or intervals of when a continuous process is operating in a state of steadiness is useful especially when steady-state models are being used to optimize the process or plant on-line or in real-time. The term steady-state implies that the process is operating around some stable point or within some stationary region where it must be assumed that the accumulation or rate-of-change of material, energy and momentum is statistically insignificant or negligible. This new approach is to assume the null-hypothesis that the process is stationary about its mean subject to independent and identically distributed random error or shocks (white-noise) …
Exploring The Mechanisms Of Dna Hybridization On A Surface, Terry J. Schmitt, J Brandon Rogers, Thomas A. Knotts Iv
Exploring The Mechanisms Of Dna Hybridization On A Surface, Terry J. Schmitt, J Brandon Rogers, Thomas A. Knotts Iv
Faculty Publications
DNA microarrays are a potentially disruptive technology in the medical field, but their use in such settings is limited by poor reliability. Microarrays work on the principle of hybridization and can only be as reliable as this process is robust, yet little is known at the molecular level about how the surface affects the hybridization process. This work uses advanced molecular simulation techniques and an experimentally parameterized coarse-grain model to determine the mechanism by which hybridization occurs on surfaces. The results show that hybridization proceeds through a mechanism where the untethered (target) strand often flips orientation. For evenly lengthed strands, …
Coal Char-Co2 Gasification Measurements And Modeling In A Pressurized Flat-Flame Burner, Randy C. Shurtz, Thomas H. Fletcher
Coal Char-Co2 Gasification Measurements And Modeling In A Pressurized Flat-Flame Burner, Randy C. Shurtz, Thomas H. Fletcher
Faculty Publications
A pressurized flat-flame burner (PFFB) was used to conduct coal gasification studies. The PFFB was designed to provide an environment with laminar, dispersed entrained flow, with particle heating rates of ∼105 K/s, pressures of up to 15 atm, and gas temperatures of up to 2000 K. Residence times were varied from 30 to 700 ms in this study. Char gasification studies by CO2 were conducted on a subbituminous coal and 4 bituminous coals in the PFFB. Pressures of 5, 10, and 15 atm were used with gas compositions of 20, 40, and 90 mol % CO2. Gas conditions with peak …
Characterization Of Macromolecular Structure Of Pyrolysis Products From A Colorado Green River Oil Shale, James L. Hillier, Thomas H. Fletcher, Mark S. Solum, Ronald J. Pugmire
Characterization Of Macromolecular Structure Of Pyrolysis Products From A Colorado Green River Oil Shale, James L. Hillier, Thomas H. Fletcher, Mark S. Solum, Ronald J. Pugmire
Faculty Publications
Volatile products from an oil shale from the Colorado Green River formation were studied by several methods. The oil shale was demineralized, and the resulting kerogen was also chemically analyzed. Both the oil shale and the demineralized kerogen were pyrolyzed at 10 K/min, and the pyrolysis products (light gas, tar, and char) were analyzed using 13C NMR, XPS, GC/MS, and FTIR. Low temperature ashing was performed in order to compare pyrolysis yields of oil shale and demineralized kerogen on a dry ash-free basis. Volatile yields of approximately 75% were achieved in an oil shale retort and 79% in the kerogen …
Time-Dependent Deposition Characteristics Of Fine Coal Fly Ash In A Laboratory Gas Turbine Environment, Robert Laycock, Thomas H. Fletcher
Time-Dependent Deposition Characteristics Of Fine Coal Fly Ash In A Laboratory Gas Turbine Environment, Robert Laycock, Thomas H. Fletcher
Faculty Publications
Time-dependent deposition characteristics of fine coal fly ash were measured in the Turbine Accelerated Deposition Facility (TADF) at Brigham Young University. Two samples of subbituminous coal fly ash, with mass mean diameters of 3 and 13 microns, were entrained in a hot gas flow with a gas temperature of 1288 C and Mach number of 0.25. A nickel-based, superalloy metal coupon approximately 0.3 cm thick was held in a hot particle-laden gas stream to simulate deposition in a gas turbine. Tests were conducted with deposition times of 20, 40, and 60 min. Capture efficiencies and surface roughness characteristics (e.g., Ra) …
Prediction Of Sawdust Pyrolysis Yields From A Flat-Flame Burner Using The Cpd Model, Aaron D. Lewis, Thomas H. Fletcher
Prediction Of Sawdust Pyrolysis Yields From A Flat-Flame Burner Using The Cpd Model, Aaron D. Lewis, Thomas H. Fletcher
Faculty Publications
High heating rate pyrolysis experiments were performed on a softwood sawdust in a flat-flame burner reactor at temperatures from 1163 to 1433 K with particle residence times ranging from 23 to 102 ms at atmospheric pressure. Volatile yields of the 45−75 μm sawdust were measured and are believed to be similar to those that would occur in an industrial entrained-flow combustor or gasifier. A refractory tar yield near 1.5 wt % (dry, ash-free) was measured. A high percentage of the fully pyrolyzed sawdust char was spherical, having lost the original sawdust structure. It is suggested that the morphology of sawdust …
Liquid-Liquid Equilibrium Of Biodiesel Components, Joseph C. Bell
Liquid-Liquid Equilibrium Of Biodiesel Components, Joseph C. Bell
Theses and Dissertations
Biodiesel is produced from vegetable oils through transesterification. Triglyceride mixtures extracted from oilseed feedstocks are upgraded by reaction with an alcohol in the presence of a catalyst to produce fatty acid esters. This reaction produces a mixture of esters, glycerin, alcohol, and catalyst. Separation of the fatty acid esters (biodiesel) and glycerin can be accomplished through liquid-liquid extraction by water addition. Designing liquid-liquid extraction with water as the solvent requires ternary liquid-liquid equilibrium data for mixtures of water, glycerin, and fatty acid esters. Ternary mixture LLE data have been experimentally measured for several of these systems. Those measured include mixtures …
Streamlined Extract Preparation For E. Coli-Based Cell-Free Protein Synthesis And Rapid Site-Specific Incorporation Of Unnatural Amino Acids In Proteins, Prashanta Shrestha
Streamlined Extract Preparation For E. Coli-Based Cell-Free Protein Synthesis And Rapid Site-Specific Incorporation Of Unnatural Amino Acids In Proteins, Prashanta Shrestha
Theses and Dissertations
This thesis reports the viability of E. coli cell extracts prepared using equipment that is both common to biotechnology laboratories and able to process small volume samples and expression of proteins containing unnatural amino acids (UAAs) at higher level using PCR amplified linear DNA templates (LETs) in cell-free protein synthesis (CFPS) system. E. coli-based cell extracts are a vital component of inexpensive and high-yielding CFPS reactions. However, effective preparation of E. coli cell extract is limited to high-pressure homogenizers (French press style or impinge-style) or bead mill homogenizers, which all require a significant capital investment. This work specifically assessed the …
Model Development And Application Of Molecular Simulations For The Study Of Proton Transport In Bulk Water And For The Prediction Of Dipole Moments Of Organic Compounds, Abhishek Asthana
Theses and Dissertations
The present work demonstrates the application of molecular simulations (MD) in two different areas: proton transport in bulk water and estimation of the dipole moment of polar organic compounds. In both areas, relatively few successful and robust methodologies exist. In the first part, a new polarizable water model is developed for MD simulations of the proton transport process. The model was parametrized from a combination of quantum chemical calculations and experimental water properties. The model was implemented in MD simulation studies of liquid water at room temperature, as well as with excess protons. For pure water the model gave good …
Site-Specific Metallization Of Multiple Metals On A Single Dna Origami Template, Bibek Uprety
Site-Specific Metallization Of Multiple Metals On A Single Dna Origami Template, Bibek Uprety
Theses and Dissertations
This work examines the selective deposition of two different metals on the same DNA origami template for nanofabrication. DNA, with adjustable size and shape serves as a suitable template for fabricating metal junctions in the nanometer domain via bottom-up assembly. Bottom-up assembly utilizes the recognition capability of molecules like DNA to self-assemble and form structures. In this regard, DNA origami provides a useful means for forming nanostructures by folding single-stranded DNA into different two and three dimensional shapes. Selective deposition of metal on specific locations of a DNA template is essential for making DNA-templated electronic circuits.Site-specific metallization of DNA origami …
Reactive Rayleigh–Taylor Turbulent Mixing: A One-Dimensional-Turbulence Study, E.D. Gonzalez-Juez, A.R. Kerstein, D.O. Lignell
Reactive Rayleigh–Taylor Turbulent Mixing: A One-Dimensional-Turbulence Study, E.D. Gonzalez-Juez, A.R. Kerstein, D.O. Lignell
Faculty Publications
We study the problem of reactive Rayleigh–Taylor turbulence in the Boussinesq framework using one-dimensional-turbulence (ODT) simulations. In this problem a reaction zone between overlying heavy/cold reactants and underlying light/hot products moves against gravity. First, we show that ODT results for global quantities in non-reactive Rayleigh–Taylor turbulence are within those from direct numerical simulations (DNS). This comparison give us confidence in using ODT to study unexplored flow regimes in the reactive case. Then, we show how ODT predicts an early stage of reactive Rayleigh–Taylor turbulence that behaves similarly to the non-reactive case, as observed in previous DNS. More importantly, ODT indicates …
Fib/Sem-Based Calculation Of Tortuosity In A Porous Licoo2 Cathode For A Li-Ion Battery, T. Hutzenlaub, A. Asthana, J. Becker, D. R. Wheeler, R. Zengerle, S. Thiele
Fib/Sem-Based Calculation Of Tortuosity In A Porous Licoo2 Cathode For A Li-Ion Battery, T. Hutzenlaub, A. Asthana, J. Becker, D. R. Wheeler, R. Zengerle, S. Thiele
Faculty Publications
We present a new method to quantify tortuosity in the porous, LiCoO2 cathode of a Li-ion battery. The starting point is a previously published 3D reconstruction from FIB/SEM images with three phases, the active material domain, carbon-binder domain and pore space. Based on this geometrical configuration, we compute effective diffusivities, from which we in turn derive tortuosity values for the pore space ranging between 5 and 11.6 for the three spatial directions. In a next step, we compare our approach to an imaging method that employs back-filling material. These methods do not differentiate between the carbon-binder domain and the pore …
Ultrasound-Induced Phase Change Of Emulsion Droplets For Targeted Gene And Drug Delivery, James R. Lattin
Ultrasound-Induced Phase Change Of Emulsion Droplets For Targeted Gene And Drug Delivery, James R. Lattin
Theses and Dissertations
This dissertation explores the potential of using perfluorocarbon emulsion droplets to add an ultrasound-sensitive element to drug delivery systems. These emulsion droplets may be induced to vaporize with ultrasound; during the rarefactional phase of an ultrasound wave, the pressure around the droplets may fall below the vapor pressure of the liquid forming the emulsion, providing a thermodynamic potential for vaporization. This ultrasound-induced phase change of the emulsion droplet could release therapeutics attached to the droplet surface or aid in drug delivery due to mechanical effects associated with vaporization and expansion, similar to the ability of cavitating bubbles to aid in …
Beyond Gel Electrophoresis: Microfluidic Separations, Fluorescence Burst Analysis, And Dna Stretching, Kevin D. Dorfman, Scott B. King, Daniel W. Olson, Joel D. P. Thomas, Douglas R. Tree
Beyond Gel Electrophoresis: Microfluidic Separations, Fluorescence Burst Analysis, And Dna Stretching, Kevin D. Dorfman, Scott B. King, Daniel W. Olson, Joel D. P. Thomas, Douglas R. Tree
Faculty Publications
This review addresses methods for obtaining sequence information directly from unamplified genomic length DNA. Our generic starting point is a large piece of DNA that contains many thousands of base pairs (kilobase pairs, kbp) or even millions of base pairs (megabase pairs, Mbp). We would like to determine the genomic distance between two repeats of a given sequence, indicated by the red dots on the coiled DNA molecule in Figure 1. Let us consider the case where these sequences are restriction sites, which can be selectively cut using proteins known as restriction enzymes. For decades, gel electrophoresis served as the …
Syngas Impurity Effects On Cell Growth, Enzymatic Activities And Ethanol Production Via Fermentation, Deshun Xu
Syngas Impurity Effects On Cell Growth, Enzymatic Activities And Ethanol Production Via Fermentation, Deshun Xu
Theses and Dissertations
A syngas compositional database with focus on trace impurities was established. For this work, ammonia (NH3) and benzene (C6H6) effects on cell growth, enzymatic activities of hydrogenase and alcohol dehydrogenase (ADH), and product formation were studied. NH3, after entering media, will be converted rapidly to NH4+, which will raise the total osmolarity of the media. NH3, as a common nutrient for the cell growth, is not the real culprit for cell growth inhibition. In essence, it is the high osmolarity resulting from the accumulation of NH4+ in the media which disrupts the normal regulation of the cells. It was concluded …
Thermodynamic Kinetics And Efficiency Analysis Of Methyl Viologen, Chang Chen
Thermodynamic Kinetics And Efficiency Analysis Of Methyl Viologen, Chang Chen
Theses and Dissertations
Methyl Viologen (MV) is an electron mediator that has great possibilities to be used with an electrode system in which the electrode system provides electrons towards reducing MV species. MV has three redox states and they can be converted to each other via redox reactions on the surface of the electrode. The concentration of the three species of MV was related to the voltage potential applied to the system through a thermodynamic model. With the thermodynamic model the concentration of the three species can be predicted with different applied voltage potentials towards providing guidance for controlling the redox state of …
Defining The Role Of Ultrasound In Drug Delivery, William G. Pitt
Defining The Role Of Ultrasound In Drug Delivery, William G. Pitt
Faculty Publications
Ultrasound is a very effective modality for drug delivery because energy that is noninvasively transmitted through the skin can be focused on a specific location and employed to release drug at that site. Most of the drug delivery techniques employ one or both of the results of ultrasonic insonation – the generation of thermal energy, called hyperthermia, or the oscillation of gas bubbles, called acoustic cavitation. Cavitation perturbs cell membrane structures via several modes and increases the permeability to drugs or other solutes. Microconvection, caused by stable cavitation, shears cell membranes. The shock waves and fluid jets of inertial cavitation …
Phase Transitions Of Nanoemulsions Using Ultrasound: Experimental Observations, Ram Singh, Ghaleb A. Husseini, William G. Pitt
Phase Transitions Of Nanoemulsions Using Ultrasound: Experimental Observations, Ram Singh, Ghaleb A. Husseini, William G. Pitt
Faculty Publications
The ultrasound-induced transformation of perfluorocarbon liquids to gases is of interest in the area of drug and gene delivery. In this study, three independent parameters (temperature, size, and perfluorocarbon species) were selected to investigate the effects of 476-kHz and 20-kHz ultrasound on nanoemulsion phase transition. Two levels of each factor (low and high) were considered at each frequency. The acoustic intensities at gas bubble formation and at the onset of inertial cavitation were recorded and subsequently correlated with the acoustic parameters. Experimental data showed that low frequencies are more effective in forming and collapsing a bubble. Additionally, as the size …
Development Of A Method To Study Thromboembolism By Direct Observation In Blood-Contacting Microsystems Using High-Definition Video Microscopy, Yong Min Kim
Theses and Dissertations
A unique and novel method to study thromboembolism by direct observation was developed. High-definition videos of thrombus formation and embolization were successfully obtained in miniature flow cells using in-vitro, non-invasive, real-time techniques. Critical parameters of thromboembolism such as thrombus growth rate, thrombus growth direction, shear force on the thrombus at embolization, and adhesion strength of the thrombus to the foreign surface were determined. Thrombus growth was found predominantly in two locations: 1) in the flow recirculation zone just after the trailing edge of the small tubes (53%) and 2) at the leading edge of the small tubes (47%). In the …
Novel Iron Catalyst And Fixed-Bed Reactor Model For The Fischer-Tropsch Synthesis, Kyle Martin Brunner
Novel Iron Catalyst And Fixed-Bed Reactor Model For The Fischer-Tropsch Synthesis, Kyle Martin Brunner
Theses and Dissertations
This work investigates a novel iron Fischer-Tropsch (FT) catalyst preparation and describes the development of a trickle fixed-bed recycle reactor model (TFBRRM) for the FT synthesis applicable to both iron and cobalt catalysts. The iron catalyst preparation was developed using a novel solvent deficient precipitation reaction. Fifteen Fe/Cu/K/SiO2 catalysts were prepared to investigate key preparation variables including timing of promoter addition, washing or not washing after precipitation, and drying temperature. Adding promoters to starting materials before precipitation (1S) gives more uniform promoter distributions which gives higher water-gas shift activity and lower methane selectivity. Unwashed catalysts have smaller average pore and …
Understanding Noble Metal Addition In Cobalt Fischer Tropsch Catalysts, Kari Marie Cook
Understanding Noble Metal Addition In Cobalt Fischer Tropsch Catalysts, Kari Marie Cook
Theses and Dissertations
The effects of noble metal (NM) promotion and deposition order (co-deposition of NM with the final Co deposition [co-dep] or sequential deposition of NM after Co deposition [seq-dep]) on surface area, pore size, metal retention, crystallite size, noble metal distribution and bonding in Co Fischer Tropsch (FT) catalysts were studied as were the resulting Co reducibility and Fischer Tropsch activity/selectivity properties. Catalysts containing nominally 25wt% Co with either 0.3 wt% Ru, 0.58 wt% Pt, 0.55wt% Re, or no NM on a La-stabilized-Al2O3 support were prepared by wet deposition. The Co, Pt, and Re were uniformly dispersed, but Ru distribution and …
Homogeneous Viologens For Use As Catalysts In Direct Carbohydrate Fuel Cells, Dane C. Hansen
Homogeneous Viologens For Use As Catalysts In Direct Carbohydrate Fuel Cells, Dane C. Hansen
Theses and Dissertations
Deriving electrical energy from glucose and other carbohydrates under mild conditions is an important research objective because these biomolecules are abundant, renewable, and can provide 12 to 24 electrons per molecule, yielding substantial electrical power. It was previously observed that disubstituted viologens, salts of N,N'-disubstituted 4,4'-bipyridine, are able to oxidize glucose under alkaline conditions. Building on that initial result, the objective of this work was to understand and quantify the effectiveness and utility of viologens as catalysts for use in direct carbohydrate fuel cells.The extent that viologens oxidize carbohydrates, the conditions under which that oxidation occurs, and the mechanism for …
Constrained Control And Optimization Of Tubular Solid Oxide Fuel Cells For Extending Cell Lifetime, Ben Spivey, John Hedengren, Thomas F. Edgar
Constrained Control And Optimization Of Tubular Solid Oxide Fuel Cells For Extending Cell Lifetime, Ben Spivey, John Hedengren, Thomas F. Edgar
Faculty Publications
Extending fuel cell lifetime is a necessary objective for reducing fuel cell power generation cost of electricity. Capital costs comprise the most significant fraction of the cost of electricity. Reducing the frequency of fuel cell replacement can be achieved by implementing a control strategy that prevents excursions into operating regions causing failure. In this paper we implement a constrained MIMO model predictive controller (MPC) to avoid the failure modes relevant for a high-temperature tubular solid oxide fuel cell (SOFC) system while performing load-following. The primary causes of failure are catalyst poisoning, fuel or air starvation, carbon deposition, and microcracking. Prior …
Multiple Molecule Effects On The Cooperativity Of Protein Folding Transitions In Simulations, Jacob I. Lewis, Devin J. Moss, Thomas A. Knotts Iv
Multiple Molecule Effects On The Cooperativity Of Protein Folding Transitions In Simulations, Jacob I. Lewis, Devin J. Moss, Thomas A. Knotts Iv
Faculty Publications
Though molecular simulation of proteins has made notable contributions to the study of protein folding and kinetics, disagreement between simulation and experiment still exists. One of the criticisms levied against simulation is its failure to reproduce cooperative protein folding transitions. This weakness has been attributed to many factors such as a lack of polarizability and adequate capturing of solvent effects. This work, however, investigates how increasing the number of proteins simulated simultaneously can affect the cooperativity of folding transitions — a topic that has received little attention previously. Two proteins are studied in this work: phage T4 lysozyme (Protein Data …
Performance Characteristics Of Lithium Coin Cells For Use In Wireless Sensing Systems, Yin Zhang
Performance Characteristics Of Lithium Coin Cells For Use In Wireless Sensing Systems, Yin Zhang
Theses and Dissertations
Understanding the pulsed discharge behavior of low-rate lithium coin cells in wireless sensing systems is critical to prolong the operating life and/or reduce the size of battery-powered WSs. This dissertation presents the battery transient analysis for a sensor duty cycle, experimental studies for sustained pulse discharge cycling, and investigation on recharge strategies for a battery/power harvesting hybrid system for WSs. The transient behavior of the lithium coin cells during pulse discharge and subsequent relaxation was investigated with single-pulse experiments and theoretical analysis. The voltage response for a pulsed discharge had two parts: a region of rapid voltage change and a …