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Dissertations / Theses on the topic 'Electrostatics'

To see the other types of publications on this topic, follow the link: Electrostatics.

Author: Grafiati

Published: 4 June 2021

Last updated: 31 July 2024

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1

Xin, W. (Weidong). "Continuum electrostatics of biomolecular systems." Doctoral thesis, University of Oulu, 2008. http://urn.fi/urn:isbn:9789514287602.

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Abstract Electrostatic interactions are very important in biomolecular systems. Electrostatic forces have received a great deal of attention due to their long-range nature and the trade-off between desolvation and interaction effects. It remains a challenging task to study and to predict the effects of electrostatic interactions in biomolecular systems. Computer simulation techniques that account for such interactions are an important tool for the study of biomolecular electrostatics. This study is largely concerned with the role of electrostatic interactions in biomolecular systems and with developing novel models to estimate the strength of such interactions. First, a novel formulation based upon continuum electrostatics to compute the electrostatic potential in and around two biomolecules in a solvent with ionic strength is presented. Many, if not all, current methods rely on the (non)linear Poisson-Boltzmann equation to include ionic strength. The present formulation, however, describes ionic strength through the inclusion of explicit ions, which considerably extends its applicability and validity range. The method relies on the boundary element method (BEM) and results in two very similar coupled integral equations valid on the dielectric boundaries of two molecules, respectively. This method can be employed to estimate the total electrostatic energy of two protein molecules at a given distance and orientation in an electrolyte solution with zero to moderately high ionic strength. Secondly, to be able to study interactions between biomolecules and membranes, an alternative model partly based upon the analytical continuum electrostatics (ACE) method has been also formulated. It is desirable to develop a method for calculating the total solvation free energy that includes both electrostatic and non-polar energies. The difference between this model and other continuum methods is that instead of determining the electrostatic potential, the total electrostatic energy of the system is calculated by integrating the energy density of the electrostatic field. This novel approach is employed for the calculation of the total solvation free energy of a system consisting of two solutes, one of which could be an infinite slab representing a membrane surface.

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2

Wong, Eric Tsz Chung. "Electrostatics in intrinsically disordered proteins." Thesis, University of British Columbia, 2012. http://hdl.handle.net/2429/43451.

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3

Kwok, Philip Chi Lip. "Electrostatics of aerosols for inhalation." Thesis, The University of Sydney, 2007. http://hdl.handle.net/2123/1934.

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Electrostatics of aerosols for inhalation is a relatively new research area. Charge properties of these particles are largely unknown but electrostatic forces have been proposed to potentially influence lung deposition. Investigation on the relationship between formulation and aerosol charging is required to understand the fundamental mechanisms. A modified electrical low pressure impactor was employed to measure the particles generated from metered dose inhalers and dry powder inhalers. This equipment provides detailed size and charge information of the aerosols. The particles were sized by impaction onto thirteen stages. The net charges in twelve of the size fractions were detected and recorded by sensitive electrometers. The drug deposits were quantified by chemical assay. The aerosol charge profiles of commercial metered dose inhalers were product-dependent, which was due to differences in the drug, formulation, and valve stem material. The calculated number of elementary charges per drug particle of size ≤ 6.06 μm ranged from zero to several ten thousands. The high charge levels on particles may have a potential effect on the deposition of the aerosol particles in the lung when inhaled. New plastic spacers marketed for use with metered dose inhalers were found to possess high surface charges on the internal walls, which was successfully removed by detergent-coating. Detergent-coated spacer had higher drug output than the new ones due to the reduced electrostatic particle deposition inside the spacer. Particles delivered from spacers carried lower inherent charges than those directly from metered dose inhalers. Those with higher charges might be susceptible to electrostatic forces inside the spacers and were thus retained. The electrostatic low pressure impactor was further modified to disperse two commercial Tubuhaler® products at 60 L/min. The DPIs showed drug-specific responses to particle charging at different RHs. The difference in hygroscopicity of the drugs may play a major role. A dual mechanistic charging model was proposed to explain the charging behaviours. The charge levels on drug particles delivered from these inhalers were sufficiently high to potentially affect deposition in the airways when inhaled. Drug-free metered dose inhalers containing HFA-134a and 227 produced highly variable charge profiles but on average the puffs were negatively charged, which was thought to be due to the electronegative fluorine atoms in the HFA molecules. The charges of both HFAs shifted towards neutrality or positive polarity with increasing water content. The spiked water might have increased the electrical conductivity and/or decreased the electronegativity of the bulk propellant solution. The number of elementary charges per droplet decreased with decreasing droplet size. This trend was probably due to the redistribution of charges amongst small droplets following electrostatic fission of a bigger droplet when the Raleigh limit was reached.

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4

Kwok, Philip Chi Lip. "Electrostatics of aerosols for inhalation." Faculty of Pharmacy, 2007. http://hdl.handle.net/2123/1934.

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PhD
Electrostatics of aerosols for inhalation is a relatively new research area. Charge properties of these particles are largely unknown but electrostatic forces have been proposed to potentially influence lung deposition. Investigation on the relationship between formulation and aerosol charging is required to understand the fundamental mechanisms. A modified electrical low pressure impactor was employed to measure the particles generated from metered dose inhalers and dry powder inhalers. This equipment provides detailed size and charge information of the aerosols. The particles were sized by impaction onto thirteen stages. The net charges in twelve of the size fractions were detected and recorded by sensitive electrometers. The drug deposits were quantified by chemical assay. The aerosol charge profiles of commercial metered dose inhalers were product-dependent, which was due to differences in the drug, formulation, and valve stem material. The calculated number of elementary charges per drug particle of size ≤ 6.06 μm ranged from zero to several ten thousands. The high charge levels on particles may have a potential effect on the deposition of the aerosol particles in the lung when inhaled. New plastic spacers marketed for use with metered dose inhalers were found to possess high surface charges on the internal walls, which was successfully removed by detergent-coating. Detergent-coated spacer had higher drug output than the new ones due to the reduced electrostatic particle deposition inside the spacer. Particles delivered from spacers carried lower inherent charges than those directly from metered dose inhalers. Those with higher charges might be susceptible to electrostatic forces inside the spacers and were thus retained. The electrostatic low pressure impactor was further modified to disperse two commercial Tubuhaler® products at 60 L/min. The DPIs showed drug-specific responses to particle charging at different RHs. The difference in hygroscopicity of the drugs may play a major role. A dual mechanistic charging model was proposed to explain the charging behaviours. The charge levels on drug particles delivered from these inhalers were sufficiently high to potentially affect deposition in the airways when inhaled. Drug-free metered dose inhalers containing HFA-134a and 227 produced highly variable charge profiles but on average the puffs were negatively charged, which was thought to be due to the electronegative fluorine atoms in the HFA molecules. The charges of both HFAs shifted towards neutrality or positive polarity with increasing water content. The spiked water might have increased the electrical conductivity and/or decreased the electronegativity of the bulk propellant solution. The number of elementary charges per droplet decreased with decreasing droplet size. This trend was probably due to the redistribution of charges amongst small droplets following electrostatic fission of a bigger droplet when the Raleigh limit was reached.

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5

Jovell, Megias Ferran. "Contact resistance and electrostatics of 2DFETs." Doctoral thesis, Universitat Autònoma de Barcelona, 2018. http://hdl.handle.net/10803/664041.

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Durant la darrera dècada, la popularització del grafè i altres materials de dues dimensions (2D) ha revolucionat la ciència de materials. Els nous fenòmens físics que esdevenen en aquests nous materials obren les possibilitats per a nous dispositius amb característiques extraordinàries. En el camp de l’electrònica d’alta freqüència, per alguns d'aquests dispositius s'ha predit que poden obrir el forat que hi ha actualment en el rang del terahertz. En aquesta tesis s'han fet servir diferents tècniques de simulació per estudiar diferents dispositius en l'entorn d'alta freqüència en ment. En primer lloc, un transistor d'efecte de camp compost per una mono capa de disulfit de molibdè (MoS$_2$) ha estat estudiat fent servir el model de deriva difusió. Per aprofundir en això, s'ha estudiat també una unió $p-n$ amb aquest mateix material. Malgrat que el model de deriva difusió està pensat per materials convencionals, s'ha fet servir un conjunt de paràmetres efectius per tal de reproduir les dades experimentals. Amb aquest conjunt de paràmetres, ha estat possible reproduir el corrent de sortida d'aquest transistor tot i que no el període de transició. D’altra banda, els resultats de la unió $p-n$ han estat molt valuosos per a l'estudi de la zona de depleció. Un dels obstacles a superar per poder poder utilitzar grafè i altres materials 2D en aplicacions d'alta freqüència, per tal de no comprometre el rendiment d'aquests dispositius, és el d'obtenir una resistència de contact (R$_c$) prou baixa. En aquesta tesi, s'ha proposat d'afegir una capa intermèdia de grafit entre el contacte metàl·lic i el canal de grafè per tal de reduir la resistència de contacte per sota dels 100 $\Omega\cdot\mu$m que sovint es cita com el límit del qual pot limitar el rendiment dels transistors d'efecte de camp. Un contacte de tipus ``top'' s'ha fet servir per a l'estructura de grafit-grafè que és molt convenient per simulacions de transport balístic mitjançant la teoria de la densitat del funcional juntament amb la teoria del no equilibri de green per a calcular aquesta resistència. En particular, s'han simulat diverses longituds de superposició del grafè sobre el contacte de grafit per tal d'estudiar-ne el seu efecte. S'ha observat que per a concentracions de portadors intrínseques, la resistència de contacte és molt alta, però per a làmines de grafè dopades, aquesta resistència decau per sota del límit citat. Per tal d'avaluar aquests resultats, s'ha estudiat el camí de corrent mitjançant el formalisme d’autocanals. Aquesta anàlisi demostra que la transferència d'electrons es duu a terme mitjançant l'àrea de solapament en comptes de la vora. El cas de vora també ha estat considerat com a referència per ser el cas límit. S'ha conclòs que una capa de grafit abans de la capa de grafè és viable per tal de reduir la resistència de contacte en els contactes metall-grafè. Finalment, per tal d'entendre amb profunditat alguns dels resultats experimentals pel què fa a la resistència de contacte entre un metall i el grafè, l'objectiu és de generar estructures realistes mitjançant la dinànima molecular. Per a tal fi, el primer pas és el de parametritzar l'enllaç metall-carboni. El potencial d'odre d'enllaç fou escollit ja que és el potencial indicat per descriure aquesta mena d'enllaços covalents. Les interaccions metall-metall foren descrites pel potencial d'àtom incrustat, i la l'enllaç carboni-carboni pel potencial de Tersoff. El potencial de l'ordre d'enllaç està caracteritzat per un conjunt de deu paràmetres que descriuen les característiques de l'enllaç com són la distància d'equilibri o l'energia d'enllaç, entre altres. Mitjançant l'algorisme de Monte Carlo temperat paral·lel, s'ha pogut obtenir un conjunt de paràmetres per a la interacció Pd-C i Ni-C.
In the last decade, the rise of graphene and other 2-dimensional materials revolutionized materials science. The new physics brought by these new materials opened up the possibilities of new devices with outstanding characteristics. In the field of radiofrequency electronics, some of these devices are predicted to bridge the terahertz gap in the frequency spectrum. In this thesis, several simulation techniques have been employed to study different devices with this long term goal in mind. In first place, a single-layer molybdenum disulfide (MoS$_2$) field effect transistor (FET) has been studied using the drift-diffusion model. To delve deeper into this, a MoS$_2$ $p-n$ junction has also been studied in this framework. Even though the drift-diffusion model is suited for bulk materials, a set of effective parameters was found. With it, it has been possible to reproduce the on-current of experimental data of the single-layer MoS$_2$ FET, but not the subthreshold swing. On the other hand, the MoS$_2$ $p-n$ junction yielded valuable results for the study of the depletion region. One of the hurdles that must be overcome in order to harness the possibilities of graphene and other 2D materials so that the performance of high frequency devices is not compromised is to achieve a low enough contact resistance (R$_c$) between the metal contact and the channel. In this thesis, an intermediate graphite layer between the metal contact and the graphene layer is proposed in order to achieve the 100 $\Omega\cdot\mu$m mark that is often quoted to be the upper limit for $R_c$ not to be the limiting factor. A graphite-graphene top contact structure is proposed and studied under ballistic transport by density functional theory (DFT) and Non-Equilibrium Green's Function Theory (NEGF) to calculate the contact resistance. In particular, several overlap amounts between graphene over the graphite bulk were studied. The results obtained are very promising for doped samples of graphene. To assess these results, a current path analysis was conducted using the eigenchannel formalism. This analysis showed that the transfer of electrons was done through the area of contact instead of an edge. It was concluded that graphite was a suitable buffer to reduce R$_c$ for metal-graphene contacts. Finally, in order to understand better some of the experimental results in the contact resistance of metal-graphene contacts, the objective was to generate realistic atomic configurations using Molecular Dynamics. For that, a first step is to parametrize the metal-carbon interactions. The bond order potential (BOP) force field was chosen for this as it is a force field that can accurately describe the metal-carbon covalent bond. The metal-metal bond is described using the embeded atom potential (EAM) and the carbon-carbon interaction, by the Tersoff force field. The BOP force field has a ten parameter set that describe the characteristics of the bond: equilibirum distance, bond energy, etc. Using Parallel Tempering Monte Carlo (PTMC) optimisation algorithm trained from first principles calculations of small metal particles on top of a graphene sheet, a set of parameters for the BOP force field was obtained for the Pd-C and Ni-C pairs.

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6

Shipway, Jennifer Mary. "Coiled coils : electrostatics & macromolecular assemblies." Thesis, University of Sussex, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.250122.

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The coiled coil is a common and well-studied protein-folding motif. It is based on the seven-residue repeat abcdefg, where a and d residues are largely hydrophobic. Structurally, coiled coils comprise two or more a-helices that are brought together with the a and d residues packing in a well-defined manner to form a hydrophobic core. Interhelical electrostatic interactions are frequently observed between core-flanking g and e residues. There is debate as to whether these interactions are present solely to confer specificity, or whether they also have a role in stabilising the structures. A program, TRAWLER, was written to analyse the core-flanking interactions in a set of high-resolution structural data, and designed proteins were used to investigate the role of these interactions further. It is shown that the electrostatic interactions are stabilising in comparison to a state where the charged residues are present but not interacting. The strength of this stabilisation is strongly context dependent: pairs containing glutamic acid and lysine are more stabilising when the glutamic acid is placed at g and the lysine at e. It is proposed that this is due to the packing of these residues against the surface presented by the core a and d residues. It is noted that previous studies using different a residues in the core exhibit the opposite preference. Further designs include a histidine-based switch and a series of bi-faceted coiled coils. In the latter, coiled-coil repeats were overlaid within a sequence to produce two oligomerisation interfaces. Such sequences are seen in natural a-sheet and a-cylinder structures. Designed peptides were intended to form vertically staggered a-cylinders, leading to the formation of elongated nanotubes. The behaviours of these peptides are presented and the difficulties inherent in such designs are discussed.

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7

Houldershaw, David. "The electrostatics of iron binding to transferrin." Thesis, Birkbeck (University of London), 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.244463.

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8

Wang, Nuo. "Computational Studies on Biomolecular Diffusion and Electrostatics." Thesis, University of California, San Diego, 2015. http://pqdtopen.proquest.com/#viewpdf?dispub=3731932.

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As human understandings of physics, chemistry and biology converge and the development of computers proceeds, computational chemistry or computational biophysics has become a substantial field of research. It serves to explore the fundamentals of life and also has extended applications in the field of medicine. Among the many aspects of computational chemistry, this Ph. D. work focuses on the numerical methods for studying diffusion and electrostatics of biomolecules at the nanoscale. Diffusion and electrostatics are two independent subjects in terms of their physics, but closely related in applications. In living cells, the mechanism of diffusion powers a ligand to move towards its binding target. And electrostatic forces between the ligand and the target or the ligand and the environment guide the direction of the diffusion, the correct binding orientation and, together with other molecular forces, ensure the stability of the bound complex. More abstractly, diffusion describes the stochastic manner biomolecules move on their energy landscape and electrostatic forces are a major contributor to the shape of the energy landscape. This Ph. D. work aims to acquire a good understanding of both biomolecular diffusion and electrostatics and how the two are used together in numerical calculations. Three projects are presented. The first project is a proof of concept of the bead-model approach to calculate the diffusion tensor. The second project is the benchmark for a new electrostatics method, the size-modified Poisson-Boltzmann equation. The third project is an application that combines diffusion and electrostatics to calculate the substrate channeling efficiency between the human thymidylate synthase and dihydrofolate reductase.

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9

Loggenberg, Ernest Wilfred. "Teaching and learning electrostatics using everyday knowledge, indigenous knowledge and scientific argumentation." Thesis, Nelson Mandela Metropolitan University, 2012. http://hdl.handle.net/10948/d1008412.

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South African School Curriculum, calls for the integration of IKS within school science (Department of Education, 2006, Department of Basic Education, 2011). Lightning is an area of high interest in the Eastern Cape and is used as the topic in this study which focuses on the integration of indigenous knowledge systems in science education. The study investigated the impact of an intervention strategy framed around the use of scientific argumentation and the integration of everyday knowledge and indigenous knowledge systems (IKS) into the teaching of electrostatics at Grade Ten level. The impact focused on the teachers’ ability to implement the strategy, the electrostatics knowledge gained by learners, the learners’ argumentation ability, and the motivational and confidence levels of both teachers and learners. The sample comprised eight schools (the science teachers and their Grade Ten Physical Science learners) in the Uitenhage District of Education of the Eastern Cape Province of South Africa. Qualitative data were generated via interviews, classroom observations, pre- and post test questionnaires with open-ended questions to evoke meaningful responses that could not be anticipated by the research, and argumentation writing frames for both teachers and learners. Limited quantitative data were generated via the argumentation writing frames and the more close-ended questionnaire questions. The findings of the teacher and learner argumentation frames and the teacher checklists which revealed that the intervention impacted positively on the teachers’ ability to integrate IKS into their teaching practice. The use indigenous knowledge as the context for argumentation appears to have been a more effective way of introducing the concept than doing so within a scientific context (which the learners found difficult). The intervention facilitated an enhanced level of understanding on lightning, and assisted with the creation of the “third space” and border crossing between IKS and western science. The individual interviews disclosed the teachers’ improved ability to integrate IKS, IKS improving the facilitation of the argumentation strategy, and their improved motivation and confidence.

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10

Finlayson, Samuel David. "A direct investigation of electrostatics in nonpolar colloids." Thesis, University of Bristol, 2016. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.715773.

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11

Ghanbarian, Alavijeh Shahzad. "Atomistic and coarse-grained simulations of DNA electrostatics." Thesis, University of British Columbia, 2015. http://hdl.handle.net/2429/52864.

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This thesis aims to understand the nanoscale effects of water as a structured solvent on the phenomenon of counterion-induced DNA condensation. We present results of molecular dynamics simulations of the electrostatic interaction between two DNA molecules in the presence of divalent counterions in different solvation models. We also develop a coarse-grained implicit solvent model for investigating the dynamics on long time and length scales. In the first project, we investigate the role of the solvation effects on the interaction between like-charged cylindrical rods as simplified model for DNA molecules. We obtain the average force between two parallel charged rods in simulations that differ only by their representation of water as a implicit or explicit solvent, but have otherwise identical parameters. We find that the presence of water molecules changes the structure of the counterions and results in both qualitative and quantitative changes of the force between highly charged polyelectrolytes. In the second project, we explore the importance of the DNA geometry on the electrostatic forces by considering two rigid helical models. The simulation results indicate that the DNA shape is an essential contributor to the interaction. A regime of attractive interaction, which disappeared in the cylindrical model, is recovered in the explicit solvent model in both types of helical models. The results also confirm that the behaviour of the interactions between two DNA molecules in the explicit solvent model are different from the implicit solvent models. In the third project, we develop a coarse-grained (CG) representation of these solvation effects. This CG model is constructed from explicit simulations and significantly reduces the computational expense. Short-ranged corrections are added to the pair-wise interaction potentials in the implicit solvent model such that the structure of counterions in the system is consistent with the results from the explicit solvent simulations. This CG model succeeds in reproducing the like-charge attraction effect between DNA molecules in explicit simulations. In a final project, we apply the CG model developed previously to study three DNA strands in the presence of divalent counterions as a starting point for investigating many-body effects in the mechanism of DNA bundling.
Science, Faculty of
Physics and Astronomy, Department of
Graduate

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12

Abu-ali, Jareer Mansour. "Food coating application in: electrostatic atomization, non-electrostatic coating and electrostatic powder coating /." Connect to this title online, 2004. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1092539703.

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Thesis (Ph. D.)--Ohio State University, 2004.
Title from first page of PDF file. Document formatted into pages; contains xii, 196 p.; also includes graphics (some col.). Includes bibliographical references (p. 185-192). Available online via OhioLINK's ETD Center

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13

Benesch, Thorben. "Like-charge attraction of colloidal particles in confined space." Thesis, Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/21261.

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14

Shin, Won-Tae. "Effects of electric fields on fluids : applications in ozonation." Diss., Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/32770.

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Salama, Fawzi. "Electrostatic Charge Generation and Wall Fouling in a High-Pressure Gas-Solid Fluidized Bed: Implementation and Preliminary Testing of a Measurement Technique." Thèse, Université d'Ottawa / University of Ottawa, 2013. http://hdl.handle.net/10393/26123.

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Due to the nature of gas-solid fluidized beds, providing continuous contacts between fluidizing particles and between particles and the reactor wall, the occurrence of electrostatic charges is unavoidable. In the polyethylene industry, electrostatics is a major problem. Large amounts of electrostatic charges are generated causing polyethylene and catalyst particles to adhere to the reactor wall, forming sheets. Particle sheets can break off and block the distributor plate, causing long shutdown periods for clean-up which result in economic loss due to decreased production and higher maintenance costs. The overall purpose of the project of which this thesis is part of is to help industry in minimizing this problem by examining the mechanisms underlying this phenomenon. Towards this goal, an experimental technique for the measurement of the degree of wall fouling and its charge distribution was previously developed and implemented in an atmospheric system with a column of 0.102 m in diameter. This technique was extended in this thesis to a pilot-scale unit (0.154 m in diameter) designed to be capable of operating at pressures and temperatures up to 2 600 kPa and 100°C respectively and gas velocities up to 1 m/s, which are operating conditions of industrial polyethylene reactors. Preliminary experiments showed that increasing the operating pressure from 101 kPa to 401 kPa almost doubled the amount of polyethylene wall fouling due to the higher bubble rise velocity at this pressure, enhancing charge generation within the fluidized bed. Changing the particle size distribution by removing particles smaller than 250 μm had no significant effect on the extent of the wall fouling. Increasing the column diameter from 0.102 m to 0.154 m decreased wall fouling due to the lower column wall area per mass of particles. Overall, particle-particle contacts generated positively and negatively charged particles, but did not produce a net charge in the bed due to the negligible elutriation. However, particle-wall contacts produced a net charge. The formation of the wall layer was due to the image force created by the net charge and the layering effect created by the attraction between oppositely charged particles.

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16

Armour-Chelu, David Ian. "The measurement of the charging properties of fine particulate materials in pneumatic suspension." Thesis, University of Greenwich, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.285986.

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Chandrasekhar, Prabhu. "Design And Testing Of A Triboelectrostatic Separator For Cleaning Coal." Thesis, Virginia Tech, 1998. http://hdl.handle.net/10919/31594.

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Numerous advanced coal-cleaning processes have been developed in recent years that are capable of substantially reducing both ash and sulfur-forming minerals from coal. However most of the processes involve fine grinding and use water as a medium; therefore, the clean coal products must be dewatered before they can be transported and burned in power plants. Unfortunately, dewatering is an expensive process, which makes it difficult to deploy advanced coal cleaning processes in commercial applications. Dry beneficiation technique is an alternate approach to solving this problem. Additionally, dry beneficiation process can be economically competitive and environmentally safe. Triboelectrostatic separation is one such technique and is very effective when applied to fine coal unlike other dry beneficiation techniques. This work involves the design (mathematical and physical) and testing of a novel triboelectrostatic separation process.
Master of Science

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18

Kanim, Stephen Emile. "An investigation of student difficulties in qualitative and quantitative problem solving : examples from electric circuits and electrostatics /." Thesis, Connect to this title online; UW restricted, 1999. http://hdl.handle.net/1773/9775.

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19

Velo, Ani P. "Optimal Design of Gradient Fields with Applications to Electrostatics." Digital WPI, 2000. https://digitalcommons.wpi.edu/etd-dissertations/311.

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"In this work we consider an optimal design problem formulated on a two dimensional domain filled with two isotropic dielectric materials. The objective is to find a design that supports an electric field which is as close as possible to a target field, under a constraint on the amount of the better dielectric. In the case of a zero target field, the practical purpose of this problem is to avoid the so called dielectric breakdown of the material caused due to a relatively large electric field. In general, material layout problems of this type fail to have an optimal configuration of the two materials. Instead one must study the behavior of minimizing sequences of configurations. From a practical perspective, optimal or nearly optimal configurations of the two materials are of special interest since they provide the information needed for the manufacturing of optimal designs. Therefore in this work, we develop theoretical and numerical means to support a tractable method for the numerical computation of minimizing sequences of configurations and illustrate our approach through numerical examples. The same method applies if we were to replace the electric field by electric flux, in our objective functional. Similar optimization design problems can be formulated in the mathematically identical contexts of electrostatics and heat conduction."

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20

Hanf, Karl J. M. (Karl John Mortley) 1969. "Protein design with hierarchical treatment of solvation and electrostatics." Thesis, Massachusetts Institute of Technology, 2002. http://hdl.handle.net/1721.1/29223.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2002.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Includes bibliographical references (p. 249-258).
A detailed treatment of the electrostatic energy of biomolecules in solution is used for two applications that require consideration of large numbers of states: multiple-site titration and protein design. The continuum electrostatic model is combined with covalent, van der Waals, and non-polar energy terms, and the statistical mechanical basis for this model is reviewed. Multiple-site titration is modeled with four titratable residues of the protein barstar. A full enumeration of the titration states is used to predict pH-dependent properties of the system, and the effects of several simplifying assumptions are evaluated. The analytical continuum electrostatics (ACE) method, a computationally inexpensive approximation of the electrostatic free energy, is evaluated in the context of predicting group terms of the binding free energy. A primary source of error in the ACE prediction of atomic solvation energies is identified and ameliorated. A procedure is developed which optimizes the parameters of the ACE method in order to minimize its errors as compared to finite-difference solution of the linearized Poisson-Boltzmann equation. Parameter sets optimized on a "testing" biomolecular binding system yield reduced average errors for related biomolecular systems. Finally, a protein design method is developed which uses the dead-end elimination and A* discrete search algorithms to systematically search large numbers (10²⁴) of structures, varying the proteinsequence and the side chain conformation at all selected residues.
(cont.) The method is novel in its co-optimization of binding and folding free energies, its use of three levels of increasingly detailed discrete search (sequence, fleximers, and rotamers), and its use of three hierarchical energy functions to successively screen candidate structures identified by the discrete search. Redesigning sets of three and seven residues of the protein barstar, the wild-type sequence, which is experimentally known to bind very tightly to barnase, is ranked very highly by this method (#5 out of 8000, or #89 out of 1.3 x 10⁹), unlike that of previous protein design studies. The present method chooses a structure for the wild-type sequence that is very similar to the crystal structure. Several novel sequences predicted to bind more tightly than wild-type barstar are promising candidates for synthesis.
by Karl J.M. Hanf.
Ph.D.

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Alkhateeb, Osama. "Singularity-Free Boundary Methods for Electrostatics and Wave Scattering." University of Akron / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=akron1334816052.

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Deb, P. "Electrostatics and dynamics in molecular functions: a spectroscopic approach." Thesis(Ph.D.), CSIR-National Chemical Laboratory, Pune, 2019. http://dspace.ncl.res.in:8080/xmlui/handle/20.500.12252/5848.

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Understanding the physical basis of biomolecular processes is a continued pursuit in molecular biology. Non-covalent interactions (hydrogen bonding, hydrophobic interactions, electrostatic interactions, van der Waals interactions, etc.), fundamental to several biological processes, are exploited to regulate biomolecular functions involving molecular-recognition, protein folding, enzyme-catalysis and protein-protein interactions. In addition to these interactions, biological macromolecules have dynamic structures and the fluctuations of these structures are intimately related to their biological functions. Even at normal temperatures under thermal equilibrium conditions, the proteins are never at rest. Almost all biological processes involve structural and conformational changes in proteins. Proteins, in course of their transient interactions and conformational changes, behave in astounding ways, leading to enzyme catalysis, protein folding and misfolding, signaling and transport, charge transfer and energy relaxation and transduction. Proteins are the functional entities of cell and malfunction of proteins leads to several diseases. Therefore a cognitive understanding of interactions and dynamics, which play the central role in protein functions, is also crucial in the realm of drug discovery. Apart from understanding biomolecular functions, a feasible and economically viable synthetic strategy is required to obtain desired organics motifs of clinical importance. To this end, modern organic chemistry is longing for developing suitable catalysts to introduce chemical changes in reactions with a high level of precision. The core of catalyst design in homogeneous medium requires the knowledge of different kinds of interactions involved in catalysis along with the knowledge of the nature of fluctuating solvent medium. Various interactions, responsible in catalyzing reactions, are often non-covalent in nature. However, due to the lack of a general approach in describing/quantifying non-covalent interactions and dearth of our knowledge on the role of solvent dynamics in reaction mechanism, a unique catalyst design principle is still not known to date. Molecular functions are largely governed by intermolecular interactions. Usual theoretical approaches use some geometry and distance criteria to describe different intermolecular interactions. However often such descriptions lead to rise of confusion. Moreover, describing intermolecular interactions through geometric and distance constraints conceals the fact that such interactions can be explained and understood well by electrostatics. In this thesis, using electrostatics and dynamics, we have addressed few important challenges in biology and synthetic chemistry, the two principal contributing domains toward developing molecules relevant to the pharmaceutical industry. We have described how we have been able to surmount the challenges those came along the way.
AcSIR

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He, Chuan. "Probing the electrostatics and hydrodynamics in gas-solid fluidized beds." Thesis, University of British Columbia, 2015. http://hdl.handle.net/2429/52320.

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Novel electrostatic dual-tip probes, combined with suitable signal analysis methods, were developed for in-situ measurement and monitoring of particle charge density levels and bubble properties inside gas-fluidized beds. The probes were calibrated in several particulate flow devices : ejector-funnel, motor-pulley, vertical tube and vibration tray setups, as well as a two-dimensional fluidized bed. The effects of particle charge density, solid flux, particle velocity and angle of impact on the transferred current received by the probe from charged particles were quantified. For dual-tip (two-material) probes, substantial differences were observed in the signals from the two tips made of different materials, arising mainly from charge transfer and depending on the hydrodynamics and charge density inside the bed. The probes were deployed with glass beads and polyethylene particles for both single bubble injection and freely bubbling experiments in two- and three-dimensional fluidization columns of different scales. Statistical and Fast Fourier Transform analysis showed that current signals were strongly affected by the local hydrodynamics in the fluidized bed. The amplitudes of current signal peaks, peak frequencies, as well as mean and standard deviations of the current increased with increasing superficial gas velocity. Local particle charge density and bubble behaviour were estimated by a signal processing procedure with decoupling methods. The probes were tested in steady state experiments, as well as in dynamic experiments by abruptly changing the superficial gas velocity or adding antistatic agent. Both particle charge density and bubble rise velocity obtained from the probes were of the same order of magnitude and followed similar trends as those directly measured by a Faraday cup and video images, respectively. The electrostatic probe signal was found to not always be consistent with the charge polarity and charge density on the particles. The probe signals and particles charge densities may have different polarity and relative magnitudes for different operating conditions and particle properties : density, mean size and size range, dielectric constant, sphericity, roughness and hydrophobicity. Particles with narrow size distribution and larger mean size generated higher charge densities. The novel probe has potential for in-situ monitoring electrostatic charges and hydrodynamic behaviour in gas-solid fluidized beds.
Applied Science, Faculty of
Chemical and Biological Engineering, Department of
Graduate

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Wilcox, Bethany R. "New tools for investigating student learning in upper-division electrostatics." Thesis, University of Colorado at Boulder, 2015. http://pqdtopen.proquest.com/#viewpdf?dispub=3704843.

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Student learning in upper-division physics courses is a growing area of research in the field of Physics Education. Developing effective new curricular materials and pedagogical techniques to improve student learning in upper-division courses requires knowledge of both what material students struggle with and what curricular approaches help to overcome these struggles. To facilitate the course transformation process for one specific content area -- upper-division electrostatics -- this thesis presents two new methodological tools: (1) an analytical framework designed to investigate students' struggles with the advanced physics content and mathematically sophisticated tools/techniques required at the junior and senior level, and (2) a new multiple-response conceptual assessment designed to measure student learning and assess the effectiveness of different curricular approaches. We first describe the development and theoretical grounding of a new analytical framework designed to characterize how students use mathematical tools and techniques during physics problem solving. We apply this framework to investigate student difficulties with three specific mathematical tools used in upper-division electrostatics: multivariable integration in the context of Coulomb's law, the Dirac delta function in the context of expressing volume charge densities, and separation of variables as a technique to solve Laplace's equation. We find a number of common themes in students' difficulties around these mathematical tools including: recognizing when a particular mathematical tool is appropriate for a given physics problem, mapping between the specific physical context and the formal mathematical structures, and reflecting spontaneously on the solution to a physics problem to gain physical insight or ensure consistency with expected results. We then describe the development of a novel, multiple-response version of an existing conceptual assessment in upper-division electrostatics courses. The goal of this new version is to provide an easily-graded electrostatics assessment that can potentially be implemented to investigate student learning on a large scale. We show that student performance on the new multiple-response version exhibits a significant degree of consistency with performance on the free-response version, and that it continues to provide significant insight into student reasoning and student difficulties. Moreover, we demonstrate that the new assessment is both valid and reliable using data from upper-division physics students at multiple institutions. Overall, the work described in this thesis represents a significant contribution to the methodological tools available to researchers and instructors interested in improving student learning at the upper-division level.

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Wu, Meng-Jiao 1981. "Improvement of the precorrected-FFT implementation of biomolecule electrostatics simulation." Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/87873.

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Thesis (M.Eng. and S.B.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2003.
Includes bibliographical references (leaves 31-32).
by Meng-Jiao Wu.
M.Eng.and S.B.

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Fallaize, D. R. "Large-scale parallelised boundary element method electrostatics for biomolecular simulation." Thesis, University College London (University of London), 2012. http://discovery.ucl.ac.uk/1343954/.

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Large-scale biomolecular simulations require a model of particle interactions capable of incorporating the behaviour of large numbers of particles over relatively long timescales. If water is modelled as a continuous medium then the most important intermolecular forces between biomolecules can be modelled as long-range electrostatics governed by the Poisson- Boltzmann Equation (PBE). We present a linearised PBE solver called the "Boundary Element Electrostatics Program"(BEEP). BEEP is based on the Boundary Element Method (BEM), in combination with a recently developed O(N) Fast Multipole Method (FMM) algorithm which approximates the far-field integrals within the BEM, yielding a method which scales linearly with the number of particles. BEEP improves on existing methods by parallelising the underlying algorithms for use on modern cluster architectures, as well as taking advantage of recent progress in the field of GPGPU (General Purpose GPU) Programming, to exploit the highly parallel nature of graphics cards. We found the stability and numerical accuracy of the BEM/FMM method to be highly dependent on the choice of surface representation and integration method. For real proteins we demonstrate the critical level of surface detail required to produce converged electrostatic solvation energies, and introduce a curved surface representation based on Point-Normal G1-continuous triangles which we find generally improves numerical stability compared to a simpler surface constructed from planar triangles. Despite our improvements upon existing BEM methods, we find that it is not possible to directly integrate BEM surface solutions to obtain intermolecular electrostatic forces. It is, however, practicable to use the total electrostatic solvation energy calculated by BEEP to drive a Monte-Carlo simulation.

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Alvarez, Cabrera Carlos Edouardo. "On shape and electrostatics : statistical mechanics studies of model systems." Paris 11, 2010. http://www.theses.fr/2010PA112058.

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Ce travail de thèse présente une série d’études de systèmes mettant en jeu un noyau dur sphéroïdal et des interactions Coulombiennes. Nous considérons dans un premier temps une bicouche de sphères dures dipolaires, étudiée par simulations Monte Carlo (MC). Il apparait que la pression entre les deux couches est de la forme -1/h⁵, ou h est la distance inter-couches. Des structures en anneaux, entachées néanmoins d'effets de taille finie, ont par ailleurs été observées. Nous avons ensuite obtenu la solution analytique du potentiel électrostatique pour des colloïdes chargés sphéroïdaux, dans le régime de Debye-Huckel pour des conditions limites de Neumann et Dirichlet. Cette dernière permet de retrouver le potentiel lointain dans le régime de Poisson-Boltzmann pour des colloïdes fortement chargés. Des simulations MC de colloïdes sphéroïdaux avec charge ponctuelle au centre ont également été implémentées, et montrent que le potentiel électrostatique est plus fort dans les directions où la courbure des colloïdes est plus grande. Le mémoire se termine par la description de deux études en cours. Dans la première on analyse l'effet de l'addition de petites sphères sur la phase nématique de particules sphéroïdales dures. On trouve que pour un rapport d'aspect de 3, l'effet est faible, tandis que pour un rapport d’aspect de 4, la transition nématique-isotropique est repoussée à des densités plus élevées. La deuxième étude détaille les résultats de simulations MC d'un système bidisperse en taille de colloïdes sphériques chargés. Nos résultats permettent de tester des théories de champ moyen récentes proposées pour les mélanges (modèle en cellule, et jellium renormalisé). On montre en outre qu'une augmentation de la différence de tailles entre les colloïdes conduit à un effet d'écran accru pour l'espèce la plus petite, et à un effet contraire pour l'espèce de plus grande taille
This doctoral work presents a series of studies of systems in which the particles interact by means of spheroidal hard core and electrostatic interactions. We first consider a dipolar hard sphere bilayer, studied by means of Monte Carlo (MC) simulations. The pressure between the layers is found to vary as -1/h⁵, where h is the distance between layers. We observed vortex like structures, frustrated by the finite size of the system. Next we obtained the analytical solution to the screened potential of charged spheroidal colloid particles in the Debye-Huckel regime for Neumann and Dirichlet boundary conditions. This latter result agrees with the solution of the Poisson-Boltzmann equation far from the colloid for strongly charged particles. We also perform MC simulations of spheroidal colloids with a point charge at the center and find, both analytically and in simulations, that the effective potential is stronger in the direction where the curvature of the colloid is higher. Finally we present two studies under progress. The first one deals with the effect of the addition of small spheres to spheroidal prolate particles in the nematic phase. We have seen that for an aspect ratio of 3 this effect is mild, but for an aspect ratio of 4, the nematic to isotropic transition is shifted to higher spheroid densities. In the second work, preliminary MC results for a size bidisperse spherical charged colloidal system are provided. This allows for a test of recently proposed mean-field approaches for polydisperse charged systems (cell model and renormalized jellium). In addition, we have found that as the size difference between the colloids is increased, the screening of the smaller species increases, while the opposite effect is observed for the larger species

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Goh, Allex. "Electrostatics problems relating to the laser interferometer space antenna mission /." May be available electronically:, 2007. http://proquest.umi.com/login?COPT=REJTPTU1MTUmSU5UPTAmVkVSPTI=&clientId=12498.

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Dong, Feng Zhou Huan Xiang Ferrone Frank A. "Study of electrostatic effects on protein folding and binding stabilities /." Philadelphia, Pa. : Drexel University, 2005. http://dspace.library.drexel.edu/handle/1860/484.

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30

Muthiraparampil, Susamma Thomas. "Misconceptions in electrostatics among learners at university entry point: a South African case study." Thesis, Walter Sisulu University, 2012. http://hdl.handle.net/11260/d1007755.

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The study explored misconceptions in electrostatics and their origins amongst learners at entry point in a South African University. Available literature showed misconceptions in electrostatics amongst High School learners and confirmed textbooks as one of the sources of misconceptions. It was therefore important to look for misconceptions in electrostatics amongst first year Bachelor of Science (B.Sc 1) learners in physics courses and their origins at the start of the academic year. The study also explored educators' misconceptions in the topic to check whether they could also be a source of learners' misconceptions. The results were intended to give guidance on how to eliminate learners' misconceptions at school rather than carrying them to higher education institutions. The study used the ex-post facto research design and was a case-study. The ex-post facto research design enabled the researcher to investigate whether one or more pre-existing conditions have possibly caused the existing problem of misconceptions. The sample consisted of 198 learners from B.Sc 1 physics course and 28 educators from 15 High Schools in one education district in the Eastern Cape Province of South Africa. The data were collected through questionnaires, analysis of textbooks, and interviews. The Statistical Package for Social Sciences (SPSS) version 17 was used for quantitative analysis whereas categorization and coding were used for qualitative analysis. The study revealed that learners had misconceptions in electrostatics. The origins of misconceptions were traced to educators, textbooks, intuition, daily language and lack of hands-on activities. It emerged from the study that educators also had misconceptions and the cause of their misconceptions were textbooks, websites and gaps in content knowledge. The recommendations from the study were the following: identify preliminary knowledge of learners during introduction of the lesson; introduce the iii constructivist approach to teaching in the teacher training curriculum so that learners at school can be taught using the same approach; frequent upgrading of educators through inservice workshops to reduce educators' misconceptions which, in turn, will help to reduce the misconceptions among learners; introduction of conceptual change textbooks.

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Thammongkol, Vivan. "Electrostatic fluidized bed prepegging of carbon fiber with PEEK." Thesis, Georgia Institute of Technology, 1989. http://hdl.handle.net/1853/10272.

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32

Barnes, Kathryn L. "Mechanisms of particle migration in electrostatic precipitators." Thesis, Loughborough University, 1987. https://dspace.lboro.ac.uk/2134/7505.

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Electrostatic precipitators are high efficiency gas cleaning devices widely used in industry for removing particulates from process gases. A major factor affecting their performance is particle migration, which is governed by the complex interaction of electrical and hydrodynamic phenomena. A fuller understanding of these fundamental mechanisms is therefore essential to the development of realistic mathematical models. The work described in this thesis concentrates on the fluid-particle interactions in a wire-plate-system. A pilot-scale rig was built using actual components from an industrial precipitator, allowing realistic conditions to be simulated in the laboratory. Hot-wire anemometry and laser-Doppler photon correlation techniques were employed to study the time-averaged velocity field. Several designs of wall strengthener were considered, and in each case the effect on the surrounding flow field was investigated using helium bubble visualisation. The turbulent nature of the fluid was characterised by local dispersion coefficient values and fluctuating velocity components. Alumina test dust in the size range 1-10 pm was used in the precipitator under a variety of operating conditions, and a technique was established for extracting representative dust samples. The samples allowed simultaneous measurement of concentration and size distribution, from which concentration profile development and collection efficiency information was obtained. Two alternative numerical models of the precipitator were developed, both incorporating the results from the fluid flow field experimentation. The first approach was based on the finite difference solution of the convective-diffusion equation, using appropriate boundary conditions. In the second approach, the transport of dust down the precipitator duct was simulated by the step-wise progression of a series of vertical line-sources, whose motion was governed by electrical migration and lateral diffusive spread. The validity of the models was tested by comparison of the predicted concentration profiles with corresponding experimental results.

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33

D'Souza, Arvind Inacib. "Picosecond dynamics of charged carriers in amorphous semiconductors /." The Ohio State University, 1985. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487260135357755.

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Kim, Anthony Young. "Heteroaggregation of oppositely charged colloids /." Thesis, Connect to this title online; UW restricted, 2002. http://hdl.handle.net/1773/9834.

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Mainelis, Gediminas. "ELECTROSTATIC COLLECTION OF AIRBORNE MICROORGANISMS." University of Cincinnati / OhioLINK, 2000. http://rave.ohiolink.edu/etdc/view?acc_num=ucin971368202.

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Kolberg, Sigbjørn. "Modeling of Electrostatics and Drain Current in Nanoscale Double-Gate MOSFETs." Doctoral thesis, Norwegian University of Science and Technology, Department of Electronics and Telecommunications, 2007. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-1729.

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This work comprises a new technique for 2D compact modeling of short-channel, nanoscale, double-gate MOSFETs. In low-doped devices working in the subthreshold regime, the potential distribution is dominated by the capacitive coupling between the body contacts. This 2D potential is determined by an analytical solution of the Laplace equation for the body using the technique of conformal mapping. Near threshold, where the spatial inversion charge becomes important, a self-consistent solution is applied. In sufficiently strong inversion, the electronic charge will dominate the potential profile in central parts of the channel. For this case, an analytical solution of the 1D Poisson’s equation is used. Based on the modeled barrier topography, the drain current is calculated for the drift-diffusion transport mechanism. The results compare favorably with numerical simulations. A parametrized model for drain current, with all parameters extracted from the modeling framework, is presented as an example of a compact model suitable for inclusion in circuit simulators.

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Graber, Zachary T. "Electrostatics and binding properties of Phosphatidylinositol-4,5-bisphosphate in model membranes." Kent State University / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=kent1416597361.

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Smart, Jason. "The application of contimuum electrostatics and diffusional models to biomolecular systems /." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC IP addresses, 1998. http://wwwlib.umi.com/cr/ucsd/fullcit?p9906489.

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Tian, Ye. "Study of the Effect of Polyethylene Resin Particle Size on the Degree of Fluidized Bed Reactor Electrification and Wall Fouling." Thesis, Université d'Ottawa / University of Ottawa, 2014. http://hdl.handle.net/10393/31220.

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In gas-solid fluidized bed reactors, such as those employed for polyethylene production, the generation of electrostatic charge is almost unavoidable. Electrostatic charges are generated due to the continuous contacts between particles and particles and the reactor wall. In such processes, accumulation of electrostatic charge causes a layer of particles to adhere to the reactor wall, a problem known as “sheeting” in polyolefin industry. Sheeting results in frequent reactor shutdowns for clean-up and in turn significant economic loss. The overall focus of this research is to better understand the underlying mechanisms of charge generation in gas-solid fluidized beds to ultimately be able to find means to reduce or eliminate this problem. The specific objective of this thesis is to determine the effect of fluidizing particle size on the degree of bed electrification and reactor wall coating. The experimental program involved the fluidization of polyethylene resins received directly from commercial reactors (i.e., having a wide size distribution of 20-1500 micron), as well as mono-sized large particles (600-710 micron) and binary mixture of small particles (200-300 micron and 300-425 micron with fractions up to 20 wt%) and large particles (600-710 micron). Experiments were carried out under atmospheric conditions in 3D fluidization columns housing two Faraday Cups for electrostatic charge measurement. For all conditions, the charge, mass and size distribution of particles fouled on the reactor wall as well as the layer thickness were measured and compared. Fluidization of the resins as received resulted in a certain size of particles (400 µm and smaller) to adhere to the column wall. For binary mixtures, the particles layer formed on the reactor wall mainly consisted of the smaller particles. Although the extent of wall coating declined as the amount of the smaller particles increased, but the smaller particles had a much higher net specific charge and thus replaced the large particles within the wall coating. Such high charge of small particles accumulated on the column wall in turn prevented the wall coating growth due to repelling the oppositely charged particles to the bulk of the bed. Regardless of the charge polarity of the bulk and wall particles, the wall fouling formation mechanism was found to be similar. Between the two sizes of small particles tested, the 212-300 micron particles gained a higher net specific charge than 300-425 micron particles. Bipolar charging due to small and large particles contacts was detected within the bulk of the bed and the wall coating.

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Colbert, Steven Anthony ACairncross Richard A. "Numerical simulations of droplet trajectories from an electrostatic rotary-bell atomizer /." Philadelphia, Pa. : Drexel University, 2007. http://hdl.handle.net/1860/1877.

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DeBenedictis, Mach Austin. "Glass fiber / polypropylene prepregs produced by electrostatic fluidized bed powder fusion coating." Thesis, Georgia Institute of Technology, 1991. http://hdl.handle.net/1853/11190.

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Hobden, Carole Lesley. "A study of the cell surface properties of Candida albicans." Thesis, University of Essex, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.295552.

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Hsueh, Weichung Paul 1962. "Fabrication and modeling of a floating-gate transistor for use as an electrostatic-discharge detector." Thesis, The University of Arizona, 1988. http://hdl.handle.net/10150/276727.

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Electrostatic discharge is of great concern to the electronics industry. It degrades and destroys large numbers of integrated circuits at every step from fabrication through packaging and testing. The goal of this research effort was the development of a device that can be used to obtain quantitative information on electrostatic discharge (ESD) in the integrated-circuit workplace. The device that was developed can be utilized in two different modes. (1) It can be used to form ESD test wafers or test chips. (2) It can be incorporated on product chips to give the ESD history of devices or monitor the process line. The technology that was examined in this work was that for floating-gate PROMS. A simple analytical model for obtaining a parameter called the ESD factor was developed. The prototype detector was designed, fabricated and tested in the Semiconductor Processing Facility of the University of Arizona. Evidence will be presented that the FLOTOX type of EEPROM functions well in its application as an ESD detector.

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Maffett, Michael Jacob. "Computations on the Role of Electrostatic in Understanding the Effects of Pressure on Myoglobin Structure." Miami University Honors Theses / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=muhonors1209137529.

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Punzalan, Rubio Reyes. "Evaluation of the effects of ethyl triesterification of the phosphate linkage in nucleic acid complexes /." The Ohio State University, 1987. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487335992901618.

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46

Rogers, Laura Ann. "Membranes as a hub for cellular signaling /." Access full-text from WCMC, 2007. http://proquest.umi.com/pqdweb?did=1481668281&sid=2&Fmt=2&clientId=8424&RQT=309&VName=PQD.

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Anandakrishnan, Ramamoorthi. "Speeding up electrostatic computations for molecular dynamics." Diss., Virginia Tech, 2011. http://hdl.handle.net/10919/40262.

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Molecular dynamics (MD) simulations are routinely used to study the structure and function of biological molecules. However the accuracy and duration of these simulations are constrained by their computational costs, thus limiting the ability to accurately simulate systems of realistic sizes over biologically relevant time periods. The two most computationally demanding steps in these simulations are (1) determining the charge state of ionizable sites in biomolecules, which is a key input to the simulation, and (2) calculating long range electrostatic interactions during the simulation. Presented here are two novel methods, the direct interaction approximation (DIA) and the hierarchical charge partitioning (HCP) approximation, for speeding up each of these two computations. The average charge state of ionizable sites in biomolecules can be calculated as the statistical average over all possible (2^N) microstates for a molecule, where N is the number of ionizable sites. In general this computation scales exponentially as O(N² 2^N). The DIA is an O(²) approximation for calculating the average charge state of ionizable sites. For each site, the DIA treats direct interactions (interactions involving the site of interest) exactly, while using an average value for indirect interactions (interactions not involving the site of interest). The DIA was tested on two problems. The computation of thermal average properties for the 2-D Ising model of ferromagnetism, and the average charge state of ionizable residues in biomolecules. Compared to the commonly used non-deterministic Monte Carlo method, for the same computational cost, the deterministic DIA was found to be at least as accurate, as measured by RMS error relative to the exact computation. Thus, the DIA may be a practical alternative to the Monte Carlo method for some problems. In atomistic MD simulations, the computation of long range electrostatic interactions, scale as O(n²), where n is the number of atoms. For most biologically relevant timescales the simulations involve 10^12–16 simulation steps. Thus, the computational cost of long range interactions become the limiting factor in the size and duration of MD simulations. The HCP is an O(n log n) approximation for computing long range electrostatic interactions. The approximation is based on multiple levels of natural partitioning of biomolecular structures into a hierarchical set of components. For components that are far from the point of interest, the charge distribution for each component is approximated by a much smaller number of charges. For nearby components, the HCP uses the full set of atomic charges. For large structures the HCP can be several orders of magnitude faster than the exact pairwise O(n²) all-atom computation. For a representative set of structures, the accuracy of the HCP is comparable to the industry standard explicit solvent particle mesh Ewald (PME), and is in general more accurate than the spherical cutoff method. And, unlike the PME, the DIA can be easily extended to implicit solvent GB models. 50 ns implicit solvent simulations for a representative set of four biomolecules suggests that the HCP could be a practical alternative for implicit solvent simulations, and preferable to the cutoff based method. The HCP is available for general use in the open source MD software, NAB within AmberTools.
Ph. D.

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48

Ndeleni, Zingiswa. "Teaching Electrostatics in Grade 11 Physical Sciences using a Conceptual Change Approach." University of the Western Cape, 2018. http://hdl.handle.net/11394/5935.

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Magister Educationis - MEd (Mathematics and Science Education)
The study was conducted at a senior secondary school situated in a deep rural area of the district of Cofimvaba in the Eastern Cape Province. It was motivated by academically struggling grade 12 learners in my school who were experiencing problems in mastering the electrostatics concept which is introduced in grade 10. The aim was to come up with alternative teaching strategies that can assist learners in grasping the concept. This study employed the conceptual change framework as a teaching strategy to improve learners' understanding of electrostatics. Theories that underpin this study are constructivism and conceptual change. The sample for this study was a Grade11 physical science class with a total sample size of fortyfive learners. It was a case study as the researcher focused on a single class in a school. This study employed a mixed approach as both qualitative and quantitative instruments were used in the data collection process. Learners wrote the pre-test that served as a baseline evaluation. An intervention in the form of a lesson presentation followed, addressing the four stages of conceptual change. A post-test followed immediately after the presentation to assess the results of the conceptual change approach. Five learners were randomly selected from the total population for interviewing. The study found that learners understanding of electrostatics improved after the conceptual change lesson and learners indicated that they found the lessons much more interesting. The study provided insight into the use of the conceptual change framework as a teaching strategy and contributed to the limited baseline data available on the teaching of electrostatics in rural schools in South Africa.

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Poudel, Pramod Prasad. "NOVEL AROMATIC ION–PAIRS: SYNERGY BETWEEN ELECTROSTATICS AND Π-FACE AROMATIC INTERACTIONS." UKnowledge, 2012. http://uknowledge.uky.edu/chemistry_etds/4.

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This dissertation focuses on the design and study of charged aromatic molecules where weak π-π interactions synergize with electrostatic interactions to enhance the overall interaction between aromatic moieties. Each chapter investigates some aspect of this hypothetical synergy between electrostatics and π-face aromatic cohesion. The first chapter unveiled the importance of electrostatics in the intramolecular stacking of flexible aromatic molecular templates 1-2Br and 2a. While our previous studies found dicationic molecular template 1-2Br to have intramolecular π-stacking between electron poor pyridinium and electron rich xylylene moieties, no such stacking interaction was observed in the neutral analog 2a. Chapter two systematically explored the stacking pattern of electron poor aromatics in the form of oxygen- and / or nitrogen- substituted triangulenium cations, [1(NR)3]+ and [1(O)3(OH)3]+. As indicated in the chemical literature, triazatriangulenium cations [1(NR)3]+ with N- ethyl (and longer alkyl chains) chains were found to pack as face-to-face dimers. This study found the formation of columnar, face-to-face, n-meric association between aromatic cations in the structures with decreased steric interactions of the side chains in the stacking planes ([1(NMe)3]+ and [1(O)3(OH)3]+). Similar iso-structural triangulene based aromatic anions, (2)- and (3)2- didn’t indicate any facial interactions in the solid states. The possible synergy between unit charge electrostatics and π-face aromatic interactions was explored in aromatic ion pairs 1•2 of triangulene based aromatic cations and aromatic anions. This charge-assisted π-π stacking seems to be the novel way of getting strong π-system interactions where the strongest non-covalent force and the weakest non-covalent force: ionic bonding and π-stacking respectively synergize together. The π-π interaction between ionic aromatics in the solid state was investigated by means of single crystal x-ray diffraction and powder x-ray diffraction (PXRD). The interaction in the solution state was examined by UV-Vis spectroscopy, electrospray ionization mass spectroscopy (ESI-MS) and electrochemical studies. Studies found that optimal synergy was possible only in the ion pairs with no steric interactions of alkyl (or aryl) side chains in the stacking planes (1(O)3•2 & 1(NMe)3•2) and the interaction was found to be comparable with the strongest radical-assisted π-stacking described in the chemical literature.

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Grandison, Scott. "Boundary integral equation techniques in protein electrostatics and free surface flow problems." Thesis, University of East Anglia, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.410096.

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