Dissertations / Theses on the topic 'Oxygen generator'
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1
Köksal, Erin (Erin Sevim). "Computational mass transfer moduling of flow through a photocatalytic oxygen generator." Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/45816.
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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2008.Includes bibliographical references (leaves 45-46).
A self-contained, portable oxygen generator would be extraordinarily useful across a broad spectrum of industries. Both safety and energy-efficiency could be enhanced tremendously in fields such as coal mining, commercial airlines, and aerospace. A novel device is proposed which employs a photocatalytic process to produce oxygen from water. Oxygen is generated through a reaction that utilizes the interaction between an ultraviolet light and a titanium dioxide thin film to catalyze the decomposition of water into dissolved oxygen and hydrogen ions. The dissolved oxygen is then transported into a volume of gaseous nitrogen through a diffusion process. A pair of parallel microfluidic channels is employed to expedite the oxygen transport by reducing diffusion lengths, and thereby diffusion times. In the following, a computational simulation of the convection-diffusion relation was developed in order to characterize the performance of the proposed microfluidic chip. Specifically, the time to reach airflow steady state is determined for several geometries. Information from fluid dynamic modeling was then used to estimate the system performance characteristics such as power requirements, output oxygen concentration, output flow rate, and rise time of the proposed oxygen generator in a variety of applications.
by Erin Köksal.
S.B.
2
Lau, Hwee Beng Michael. "A study of the thermo-mechanical integrity issues of a ceramic oxygen generator (COG)." Thesis, Imperial College London, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.397679.
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Hill, Tyrone F. (Tyrone Frank) 1980. "Microchemical systems for singlet oxygen generation." Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/45867.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2008.Includes bibliographical references (p. 153-158).
Chemical Oxygen-Iodine Lasers (COIL) are a technology of interest for industrial and military audiences. COILs are flowing gas lasers where the gain medium of iodine atoms is collisionally pumped by singlet delta oxygen molecules, which are created through the catalyzed multiphase reaction of hydrogen peroxide and chlorine. Currently the use of COIL technology is limited by size and efficiency issues. This thesis seeks to use MEMS technology towards the development of more compact and efficient COIL systems, with a focus on the singlet oxygen generator (SOG) stage. Based on success in other applications, MEMS technology offers opportunities for improved reactant mixing, product separation, and heat transfer in SOGs. A MEMS singlet oxygen generator (or microSOG) is built and demonstrated. The chip features 32 multiplexed packed bed reaction channels and utilizes capillarity effects to separate the gas and liquid products. Cooling channels are arranged on the chip such that they form a cross-flow heat exchanger with the reaction channels. Spontaneous optical emission measurements and mass spectroscopy are used to confirm singlet oxygen production in the chip. A singlet delta oxygen molar flow rate corresponding to a power of 1.37 W was measured in the chip. The singlet oxygen molar flow rate per unit of hardware volume is 6.7x10-2 mol/L/sec, which represents an order of magnitude improvement over sparger and rotary SOG designs. A detailed physical model is developed to understand the behavior of the microSOG. This model is used along with the experimental results to gain insights into the poorly characterized singlet oxygen deactivation coefficients. Clogging and nonlinear hydraulic behavior prevented the first-generation microSOG from performing as well as the models originally suggested. These issues are addressed in a proposed second generation design, which simulations indicate will produce 50% more singlet oxygen per unit of hardware volume than its predecessor.
by Tyrone Frank Hill.
Ph.D.
4
Smelser, Jennifer Beasley. "Oxygen depletion shutdown algorithm for portable gasoline generators." Thesis, [Tuscaloosa, Ala. : University of Alabama Libraries], 2009. http://purl.lib.ua.edu/2178.
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Spirig, John Vincent. "A new generation of high temperature oxygen sensors." Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1188570727.
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Bauer, Ralph Aaron. "Inorganic membranes for power generation and oxygen production." The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1556889103215598.
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Schmidt, Marek Wojciech, and Marek Schmidt@rl ac uk. "Phase formation and structural transformation of strontium ferrite SrFeOx." The Australian National University. Research School of Physical Sciences and Engineering, 2001. http://thesis.anu.edu.au./public/adt-ANU20020708.190055.
Full textAbstract:
Non-stoichiometric strontium iron oxide is described by an abbreviated formula SrFeOx (2.5 ≤ x ≤ 3.0) exhibits a variety of interesting physical and chemical properties over a broad range of temperatures and in different
gaseous environments. The oxide contains a mixture of iron in the trivalent and the rare tetravalent state. The material at elevated temperature is a mixed oxygen conductor and it, or its derivatives,can have practical
applications in oxygen conducting devices such as pressure driven oxygen
generators, partial oxidation reactors in electrodes for solid oxide fuel cells
(SOFC).
¶
This thesis examines the behaviour of the material at ambient and elevated temperatures using a broad spectrum of solid state experimental
techniques such as: x-ray and neutron powder diffraction,thermogravimetric and calorimetric methods,scanning electron microscopy and Mossbauer
spectroscopy. Changes in the oxide were induced using conventional thermal
treatment in various atmospheres as well as mechanical energy (ball milling).
The first experimental chapter examines the formation of the ferrite from
a mixture of reactants.It describes the chemical reactions and phase transitions that lead to the formation of the oxide. Ball milling of the reactants prior to annealing was found to eliminate transient phases from the reaction route and to increase the kinetics of
the reaction at lower temperatures.
Examination of the thermodynamics of iron oxide (hematite) used for the
reactions led to a new route of synthesis of the ferrite frommagnetite and
strontium carbonate.This chapter also explores the possibility of synthesis
of the material at room temperature using ball milling.
¶
The ferrite strongly interacts with the gas phase so its behaviour was studied under different pressures of oxygen and in carbon dioxide.The changes in ferrite composition have an equilibrium character and depend on temperature and oxygen concentration in the
atmosphere. Variations of the oxygen
content x were described as a function of temperature and oxygen partial
pressure, the results were used to plot an equilibrium composition diagram.
The heat of oxidation was also measured as a function of temperature and oxygen partial pressure.
¶
Interaction of the ferrite with carbon dioxide below a critical temperature
causes decomposition of the material to strontium carbonate and SrFe12O19 .
The critical temperature depends on the partial pressure of CO2 and above
the critical temperature the carbonate and SrFe12O19 are converted back into
the ferrite.The resulting SrFe12O19 is very resistant towards carbonation and
the thermal carbonation reaction does not lead to a complete decomposition
of SrFeOx to hematite and strontium carbonate.
¶
The thermally induced oxidation and carbonation reactions cease at room
temperature due to sluggish kinetics however,they can be carried out at ambient temperature using ball milling.The reaction routes for these processes are different from the thermal routes.The mechanical oxidation induces two
or more concurrent reactions which lead to samples containing two or more
phases. The mechanical carbonation on the other hand produces an unknown
metastable iron carbonate and leads a complete decomposition of the ferrite
to strontiumcarbonate and hematite.
¶
Thermally and mechanically oxidized samples were studied using Mossbauer
spectroscopy. The author proposes a new interpretation of the Sr4Fe4O11
(x=2.75) and Sr8Fe8O23 (x=2.875)spectra.The interpretation is based
on the chemistry of the compounds and provides a simpler explanation of
the observed absorption lines.The Mossbauer results froma range of compositions
revealed the roomtemperature phase behaviour of the ferrite also
examined using x-ray diffraction.
¶
The high-temperature crystal structure of the ferrite was examined using
neutron powder diffraction.The measurements were done at temperatures
up to 1273K in argon and air atmospheres.The former atmosphere protects
Sr2Fe2O5 (x=2.5) against oxidation and the measurements in air allowed
variation of the composition of the oxide in the range 2.56 ≤ x ≤ 2.81.
Sr2Fe2O5 is an antiferromagnet and undergoes phase transitions to the paramagnetic
state at 692K and from the orthorhombic to the cubic structure
around 1140K.The oxidized formof the ferrite also undergoes a transition
to the high-temperature cubic form.The author proposes a new structural
model for the cubic phase based on a unit cell with the Fm3c symmetry.
The new model allows a description of the high-temperature cubic form of
the ferrite as a solid solution of the composition end members.The results
were used to draw a phase diagramfor the SrFeOx system.
¶
The last chapter summarizes the findings and suggests directions for further research.
8
Pettit, Andrew I. "Oxygen radical generation by lymphoblast NADPH oxidase in hypertension." Thesis, University of Leicester, 2006. http://hdl.handle.net/2381/29519.
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Objectives. The aim of this thesis was to investigate increased reactive oxygen species production originating from NADPH oxidase in lymphoblasts from hypertensive subjects. Results. Combined intra and extracellular stimulated reactive oxygen species production was increased in hypertensive cell lines. The ROS production was abolished by Diphenyleneiodonium chloride but not by rotenone, indicating that a non-mitochondrial flavoprotein, such as NADPH oxidase, was involved. Analysis of NADPH oxidase subcomponents revealed an increase in p22phox in lymphoblasts from hypertensive subjects, accounting for some of the increased reactive oxygen species production. There was increased basal Tyr/Thr phosphorylation of p44/p42 MAPK in the hypertensive lymphoblasts, but the difference was lost on stimulation. The various kinase inhibitors had no effect on basal reactive oxygen species production. Tyrosine kinase inhibition produced up to 70% reduction in stimulated reactive oxygen species production in both cell lines. Inhibition of p44/p42 MAPK kinase, P13K, and PLA2 produced a small reduction in stimulated ROS production. There was no differential reduction in ROS production from the hypertensive group with these inhibitors, suggesting no role of these pathways in priming of NADPH oxidase. Conclusions. We have shown there is increased reactive oxygen species production in lymphoblasts from hypertensive subjects probably originating from NADPH oxidase. Increased expression of p22phox in hypertension lymphoblasts accounts for approximately a third of the increased reactive oxygen species production. We could not demonstrate tyrosine kinase, p38 MAPK, p44/p42 MAPK, P13K or PLA2 priming of reactive oxygen species production.
9
Garcia, Jorge David S. M. Massachusetts Institute of Technology. "Sodium chlorate oxygen generation for fuel cell power systems." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/112489.
Full textAbstract:
Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2017.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 95-97).
In this thesis we experimentally investigated the use of sodium chlorate as an oxygen storage medium for use in underwater fuel cell power systems. Research into improving hydrogen storage systems is the primary concern when designing fuel cell systems with access to atmospheric oxygen. However, in an underwater environment, performance of the oxygen storage system cannot be overlooked. Oxygen candles using sodium chlorate offer gravimetric storage densities similar to compressed gas storage while also offering volumetric storage densities greater than both gas and cryogenic liquid oxygen storage. Unfortunately, this technology does not allow for controllable rates of oxygen production and is known to cause fires and occasionally explosions when contaminated with organic materials or exposed to external sources of heat. Though useful as an emergency source of oxygen, sodium chlorate will not be viable for use in power systems until safer and more controllable methods of releasing its oxygen are implemented. During this project we developed a batch method for releasing oxygen from sodium chlorate. Two grams of sodium chlorate with nanoscale cobalt oxide catalyst were loaded into a reaction chamber and heated until decomposition. Afterwards a piston was used to eject the materials from the reaction chamber. This method proved to be safer and more reliable than similar chlorate-based oxygen systems as the primary modes of failure, those associated with the buildup of solid residue at the inlets and exits of the reaction chamber, were removed. Aside from preventing the flow of oxygen to a fuel cell, the over-pressurization caused by these problems could compromise the reaction chamber and potentially result in catastrophic failures. The achieved rate of oxygen production, 0.21 L/min with a heating rate between 25 W and 33 W, was below the target 1.13 L/min needed to operate a 200 W PEM fuel cell. Further assessment of this method will require the use of a more active cobalt oxide catalyst, a system with a larger reaction chamber capable of decomposing increased amounts sodium chlorate per cycle and a reduction in heat losses through the use of improved insulation and thermal isolation techniques.
by Jorge David Garcia.
S.M.
10
Beigley, John Robertson. "Oxidation of waxes using microwave-generated singlet molecular oxygen." Master's thesis, University of Cape Town, 1999. http://hdl.handle.net/11427/19577.
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Waxes are a widely used chemical commodity throughout the world due to certain intrinsic properties. Applications vary widely, including such obvious ones as candles and polishes, less obviously coatings, ink, and cosmetics, and more obscurely, hot melt adhesives, textile processing and chewing gum. The waxes used are obtained from a variety of sources, natural, mineral, and synthetic. The properties of the wax determine its suitability for a particular application. For certain of the latter, a wax containing Oxygen groups is often the most appropriate type. While there are a number of such waxes that occur naturally, there are also many more in which the raw wax has undergone oxidation by chemical processes. Generally, this is done utilising elevated temperatures, and passing air or oxygen through the wax. Oxidation then takes place via a free radical process. Singlet molecular oxygen is a higher-energy state species of oxygen, in which the two electrons in the π* 2p antibonding molecular orbitals, while remaining unpaired, are excited to antiparallel spin. Reactions of singlet oxygen are very site-specific, resulting in more specific products compared to the free radical process. It was considered that oxidation of waxes by reaction with singlet oxygen might produce different products compared to the thermal oxidation, and also compared to oxidation using ozone. An apparatus was set up to test this theory. The singlet oxygen was generated by passing a stream of oxygen through a microwave beam to form a plasma, the resulting singlet oxygen-containing gas being reacted with molten wax. Optimisation of the setup was performed before performing reactions, using several different waxes. The experiments were duplicated by ones with the microwave switched off, so that any results could be ascribed to the presence of singlet oxygen, and not normal oxygen. A similar apparatus was set up to react the same waxes with ozone, the latter being generated by passing oxygen through an electrical discharge-type generator. Blank runs with the electric discharge apparatus switched off, were also carried out to be able to distinguish any reaction due to the unozonised oxygen. The results showed that the singlet oxygen only reacted with a particular type of wax, namely oxidised polyethylene wax (AC6-29), although other effects were caused by the heat of the plasma. The ozone, on the other hand, reacted readily with all types of waxes tested. Other experiments were also conducted to investigate the use of microwave technology for chemical purposes, including development of an analytical method for saponification value determination in which microwaves replaced conventional heating.
11
Ferreira, Joana Teles. "Ruthenium phythalocyanines as potential photosensitizers for singlet oxygen generation." Doctoral thesis, Universidade de Aveiro, 2017. http://hdl.handle.net/10773/22727.
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Doutoramento em QuímicaA Terapia Fotodinâmica combina luz, oxigénio molecular e um fotossensibilizador para a produção de espécies reativas de oxigénio, como 1O2 e radicais livres, os quais vão induzir stress oxidativo e, eventualmente, morte celular. Isto permite assim a destruição de células tumorais de uma forma não invasiva, seletiva e localizada, com efeitos secundários reduzidos. As ftalocianinas são compostos promissores para serem aplicados como fotossensibilizadores na produção de oxigénio singleto. No entanto, um inconveniente destes compostos é a sua reduzida solubilidade em meio aquoso. Isto pode ser ultrapassado através da sua funcionalização nas posições periféricas e/ou axiais com grupos hidrofílicos apropriados, como por exemplo hidratos de carbono e cadeias de poliéter. A introdução de ligandos axiais reduz a agregação das ftalocianinas em solução, melhorando a sua eficiência para produzir 1O2. Este trabalho descreve a síntese de Ftalocianinas de Ruténio (RuPcs) para serem utilizadas como fotossensibilizadores. Estas RuPcs estão funcionalizadas nas posições axiais com ligandos apropriados que proporcionam a solubilidade e/ou seletividade requeridas para a sua aplicação em Terapia Fotodinâmica. Neste sentido, foram sintetizados diferentes derivados de piridina e fosfina funcionalizados com grupos iónicos, cadeias de poliéter, hidratos de carbono ou com unidades de ácido fólico, as quais foram posteriormente coordenadas ao ião central de RuPcs. Adicionalmente, a solubilidade em água foi melhorada através da funcionalização da periferia das RuPcs com cadeias poliéter. Foram estudadas as propriedades físicas e fotofísicas, nomeadamente, a solubilidade em água e a capacidade de produzir oxigénio singleto, de todos os fotossensibilizadores preparados. Além disso, os compostos foram avaliados in vitro em células do cancro da bexiga com respeito à sua capacidade para serem internalizados por células cancerígenas a aos seus efeitos tóxicos, tanto no escuro como mediante ativação com luz.
The Photodynamic Therapy (PDT) combines light, molecular oxygen and a PS for the production of reactive oxygen species (ROS), such as 1O2 and free radicals, which will induce oxidative stress and, eventually, cell death. This allows for the non-invasive, selective and localized destruction of tumor cells with reduced side effects. Phthalocyanines (Pcs) are promising compounds to be applied as PSs for singlet oxygen generation. However, a major drawback of these compounds is their low solubility in physiological media. This can be overcome through functionalization of the macrocycle at the peripheral and/or axial positions with appropriate hydrophilic functions, such as carbohydrates and polyether chains. The introduction of axial ligands reduces their aggregation in solution, thus improving their 1O2 generation efficiency. This work describes the synthesis of Ruthenium Phthalocyanines (RuPcs) to be applied as photosensitizers (PSs) for singlet oxygen generation. These RuPcs are endowed with suitable axial ligands, providing the required solubility and/or selectivity. In this respect, several pyridine or phosphine-based structures bearing charged functions, polyether chains, carbohydrate units or folic acid units were synthesized and further coordinated to the central ion of RuPcs. In addition, solubility in water is enhanced through peripheral functionalization with polyether chains. The photophysical properties of the prepared PSs, namely their solubility in water and their ability to generate singlet oxygen were studied. Furthermore, the PSs were also evaluated in vitro in bladder cancer cells with respect to their capability to be internalized by cancer cells and their toxic effects, both in the dark and upon activation by light.
La Terapia Fotodinámica combina luz, oxígeno molecular y un fotosensibilizador para la producción de especies reactivas de oxígeno, como el 1O2 y radicales libres, los cuales inducen estrés oxidativo y, eventualmente, la muerte celular. Esto permite así la destrucción de células tumorales de una forma no invasiva, selectiva y localizada, con efectos secundarios reducidos. Las ftalocianinas muestran un gran potencial para su aplicación como fotosensibilizadores para la producción de oxígeno singlete. Sin embargo, un inconveniente de estos compuestos es su solubilidad reducida en medio acuoso. Esto puede superarse a través de su funcionalización en las posiciones periféricas y/o axiales con grupos hidrofílicos apropiados, como por ejemplo hidratos de carbono y cadenas poliéter. La introducción de ligandos axiales reduce la agregación de las ftalocianinas en disolución, mejorando su eficiencia para producir 1O2. Este trabajo describe la síntesis de Ftalocianinas de Rutenio (RuPcs) para su utilización como fotosensibilizadores en la producción de oxígeno singlete. Estas RuPcs están funcionalizadas en las posiciones axiales ligandos apropriados que proporcionan la solubilidad y/o selectividad requeridas para una aplicación en Terapia Fotodinámica. En este sentido, se sintetizaron diferentes derivados de piridina y fosfina funcionalizados con grupos cargados, cadenas poliéter, hidratos de carbono o con unidades de ácido fólico, las cuales fueron posteriormente coordinadas al ión central de RuPcs. Además, se mejoró la solubilidad de las RuPcs mediante la introducción de cadenas poliéter en las posiciones periféricas. Se estudiaron las propiedades físicas y fotofísicas, en particular, la solubilidad en agua y la capacidad para producir oxígeno singlete, de los fotosensibilizadores preparados. Además, todos los compuestos se evaluaron in vitro en células del cáncer de vejiga urinaria, con respecto a su capacidad para ser internalizados por las células cancerígenas y a sus efectos tóxicos, tanto en la oscuridad como mediante la activación con luz
12
Fisher, Helen M. "Mechanisms of reactive oxygen species generation by mammalian spermatozoa." Thesis, University of Edinburgh, 1995. http://hdl.handle.net/1842/20503.
Full textAbstract:
The generation of reactive oxygen species (ROS) is an activity normally associated with phagocytic leucocytes, which employ an enzymatic complex, the NADPH oxidase, to catalyze the univalent reduction of molecular oxygen to superoxide. However, it is now apparent that many other cell types, including mammalian spermatozoa, generate ROS. ROS have been implicated in peroxidative damage associated male sub-fertility, and also more recently, in the regulation of normal sperm function. With the obvious biological importance of ROS generation by spermatozoa in mind, the aims of this PhD have been to identify and characterize the mechanisms, and cellular components involved in the generation of ROS by these cells. Experiments investigating ROS generation by human spermatozoa have shown that the mechanisms involved are functionally similar to those pertaining to the NADPH oxidase of phagocytic leucocytes. ROS generation by human spermatozoa is enzymatic in nature and utilizes NADPH as the electron donor, reducing molecular oxygen to superoxide, which subsequently dismutates to hydrogen peroxide. Further similarities with the NADPH oxidase include the probable involvement of a flavoprotein and a role for protein phosphorylation, as regulated by PKC and protein phosphatases. Biochemical and molecular analyses of human spermatozoa have shown that the cellular components that form the NADPH oxidase of phagocytic leucocytes are not present in the spermatozoon. Spectral analyses of human sperm membranes failed to reveal the presence of the characteristic low potential cytochrome b558, and similarly, western blot analyses of human spermatozoa failed to detect the cytochrome b558 or the presence of the two NADPH oxidase cytosolic components, p47phox and p67phox. ROS generating activity was extracted from human spermatozoa, using the non-ionic detergent n-octyl-β-D-thioglucoside. The solubilized protein extract was resolved by non-denaturing PAGE and shown to contain 6 bands with ROS generating activity. ROS generating activity was then isolated in an active form via 2'-5'ADP affinity chromatography. The individual components of this activity were subsequently separated via SDS-PAGE, which revealed a heterogeneous protein population. One of these proteins was purified, and a polyclonal antibody raised against it.
13
Mkhize, Colin, Jonathan Britton, John Mack, and Tebello Nyokong. "Optical limiting and singlet oxygen generation properties of phosphorus triazatetrabenzcorroles." World Scientific Publishing, 2015. http://hdl.handle.net/10962/d1020266.
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Novel phosphorus triazatetrabenzcorrole (TBC) tetrasubstituted at the α- and β-positions of the peripheral fused benzene rings with t-butylphenoxy substituents have been prepared and characterized. The effect of the substituents on the electronic structures and optical properties is investigated with TD-DFT calculations and MCD spectroscopy. The optical limiting properties have been investigated to examine whether the lower symmetry that results from the direct pyrrole–pyrrole bond and hence the permanent dipole moment that is introduced result in higher safety thresholds, relative to the values that have been reported for phthalocyanines. The suitability of the compounds for singlet oxygen applications has also been examined.Original publication is available at http://dx.doi.org/10.1142/S1088424614501065
14
Sirman, John Derrick. "A study of the mass transport and electrochemical properties of materials for ceramic oxygen generators." Thesis, Imperial College London, 1998. http://hdl.handle.net/10044/1/11279.
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Махонін, Микола Віталійович. "Метод визначення параметрів генератору медичного озону для ефективного підвищення його продуктивності." Thesis, Національний технічний університет "Харківський політехнічний інститут", 2019. http://repository.kpi.kharkov.ua/handle/KhPI-Press/42015.
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Дисертація на здобуття наукового ступеня кандидата технічних наук (доктора філософії) за спеціальністю 05.11.17 «Біологічні та медичні прилади і системи». – Національний технічний університет «Харківський політехнічний інститут», Харків, 2019. Дисертація Махоніна М.В. присвячена вирішенню однієї з актуальних науково-технічних задач сучасного медичного приладобудування – підвищенню ефективності генератору медичного озону за рахунок визначення параметрів розрядної камери, напруги живлення та витрати кисню. На даний час у світі активно використовують озон та його суміші для широких потреб різних галузей. Для отримання озону використовуються спеціальні генератори озону різних типів у залежності від сфери їх застосування. Ці генератори відрізняються розмірами, кількістю озону, що генерується за відрозок часу та інші. Особливістю ж генераторів медичного озону є те, що необхідно підтримувати задані параметри отримуваної озоно-кисневої суміші на протязі усього часу проведення процедури, а у якості робочого газу використовується медичний кисень. Це дозволяє реалізовувати методики озонотерапії для максимально ефективного лікування пацієнтів. Типові параметри озоно-кисневої суміші, які повинен забезпечувати медичний генератор озону регламентуються в Україні «Методиками для застосування озону в медичній практиці», які були затверджені Міністерством охорони здоров’я в 2004 році. Згідно сучасної редакції цих методик концентрація озону в озоно-кисневій суміші повинна змінюватись у діапазоні від 0,1 до 80 мг/л, а витрата суміші від 0,1 до 1 л/хв. Медичні генератори озону активно використовуються у кабінетах озонотерапії та медичних установах України, країн СНД, а також країн Латинської Америки. Щорічно у світі проводиться велика кількість конференцій присвячених озонотерапії, на яких вона отримує свій подальший розвиток Практичне використання генераторів медичного озону свідчить, що більшість апаратури, що використовуються, потребує вдосконалення для забезпечення роботи на основі сучасних медичних рішень у лікуванні. Тобто розробка сучасного генератора потребує не тільки відповідність параметрів сучасним вимогам, а й ще запас на розвиток та можливість збільшення значень концентрації озону. Крім того, у більшості медичних генераторів озону спостерігається невідповідність заявлених параметрів озоно-кисневої суміші та значення продуктивності по озону. Продуктивність генератора озону, в свою чергу, залежить від: параметрів розрядної камери, параметрів напруги живлення, параметрів
робочого газу. Вирішенням проблему пошуку оптимальних значень цих параметрів для підвищення ефективності роботи генератора озона займаються багато науковців, серед яких можна виділити японських, німецьких та науковців з країн СНД. Але на даний момент ще не існує універсальної моделі розрахунку параметрів генератору Таким чином, задача підвищення ефективності роботи генератора медичного озону за рахунок визначення найкращих параметрів його вузлів, що дозволить підвищити якість процедур озонотерапії є актуальним і перспективним напрямком розвитку генераторів озону. У дисертаційній роботі вперше побудовано математичну модель синтезу озону в розрядній камері генератора медичного озону, яка враховує вплив не тільки параметрів електричної енергії, а також параметрів розрядної камери та робочого газу. Отримані залежності впливу параметрів електричної енергії на синтез озону у розрядній камері на основі проведеного аналізу та з використанням комп’ютерного моделювання. Отримала подальший розвиток модель процесу генерації озону в бар'єрному розряді, яка, на відміну від існуючої, враховує не тільки параметри напруги живлення і розміри камери, але і процеси, що відбуваються в розрядному проміжку. Запропоновано методику розрахунку основних параметрів генератора озону при його розробці, що дозволяє підвищити ефективність синтезу озону. Практичне значення одержаних результатів полягає у обґрунтованні переліку параметрів, що чинять найбільший вплив на продуктивність генератора медичного озону; інженерних розрахунках параметрів генератора медичного озону, які дозволили оптимізувати конструкцію генератора з заданими параметрами; реалізації експериментального зразка генератора медичного озону з вдосконаленою системою автоматичного регулювання витрати газу, що дозволила забезпечити виконання широко спектру процедур озонотерапії. Отриманні практичні результати дисертаційної роботи впроваджені на НВП «Еконіка» при розробці та виготовлення сучасних генераторів медичного озону, а також розроблений макетний зразок пройшов медичну апробації у медичному центрі «Пульс-медика» та у Інституті медичної радіології ім. С.П. Григор’єва.Thesis for the degree of candidate of technical sciences (PhD) in the specialty 05.11.17 “Biological and medical devices and systems”. -National Technical University "Kharkov Polytechnic Institute", Kharkov, 2019. The thesis is devoted to the solution of one of the current scientific and technical problems of modern medical instrument making - increasing the efficiency of the medical ozone generator by determining the parameters of the discharge chamber, the supply voltage and the oxygen consumption. Currently, ozone and its mixtures are widely used in the world for the wide range of applications. Different types of ozone generators depending on their application are used for ozone synthesis. These generators differ in size, the amount of ozone generated by the time span, etc. The peculiarity of the generators of medical ozone is that it is necessary to maintain the prescribed parameters of the resulting ozone-oxygen mixture throughout the entire duration of the procedure, and medical oxygen is used as the working gas. This allows us to implement ozone therapy techniques for the most effective treatment of patients. Typical parameters of the ozone-oxygen mixture, which the ozone generating plant should provide, are regulated in Ukraine "Methods for the application of ozone in medical practice", which were approved by the Ministry of Health in 2004. According to the modern version of these methods, the concentration of ozone in the ozone-oxygen mixture should vary in the range from 0.1 to 80 mg / l, and the flow rate of the mixture is from 0.1 to 1 l / min. Medical ozone generators are actively used in the offices of ozonotherapy and medical institutions in Ukraine, CIS countries, as well as Latin American countries. A large number of conferences devoted to ozone therapy are being held annually in the world in which it is further developed. The practical use of generators of medical ozone shows that most of the equipment used needs to be improved to provide work on the basis of modern medical solutions in treatment. That is, the development of a modern generator requires not only compliance with the parameters of modern requirements, but also a stock for development and the possibility of increasing the values of ozone concentration. In addition, in most medical ozone generators there is a discrepancy between the stated parameters of the ozone oxygen mixture and the value of ozone productivity. The performance of the ozone generator, in turn, depends on: the parameters of the discharge chamber, the parameters of the supply voltage, the parameters of the working gas. Many scientists, including Japanese, German and scholars from the CIS countries, are engaged in solving the problem of finding the optimal values of these parameters for increasing the efficiency of ozone generator operation. But at the moment there is still no universal model for calculating the parameters of the ozone generator. Thus, the task of increasing the efficiency of the medical ozone generator by determining the best parameters of its nodes, which will improve the quality of ozone therapy procedures, is an urgent and promising direction for the development of ozone generators. In the dissertation, for the first time, a mathematical model of the synthesis of ozone in a digital chamber of the medical ozone generator was constructed, which takes into account the influence not only of the parameters of electric energy, but also of the parameters of the discharge chamber and the working gas. The dependence of the influence of electric energy parameters on the synthesis of ozone in a discharge chamber was obtained on the basis of the conducted analysis and using computer simulation. The model of the ozone generation process in the barrier discharge has been further developed, which, in contrast to the existing one, takes into account not only the power supply parameters and camera dimensions, but also the processes occurring in the discharge gap. The method of calculation of the basic parameters of the ozone generator during its development, which allows increasing the efficiency of ozone synthesis, is proposed. The practical value of the results obtained is to justify the list of parameters that have the greatest impact on the performance of the medical ozone generator; engineering calculations of parameters of the generator of medical ozone, which allowed to optimize the design of the generator with the given parameters; the implementation of an experimental model of the medical ozone generator with an improved system of automatic regulation of gas consumption, which allowed to ensure the implementation of a wide range of procedures for ozone therapy. The practical results of the dissertation work were introduced at the Scientific-Production Enterprise "Econika" in the development and manufacture of modern generators of medical ozone, and also a prototype sample was developed, was tested at the medical center "Pulse Medika" and at the Institute of Medical Radiology N.A. Grigoriev.
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Giurnazi, Ali Mansour. "Involvement of reactive oxygen species generation in cellular and subcellular fractions." Thesis, University of Nottingham, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.318298.
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Zhang, Jinnan. "Enhancement of Silver Nanoparticles in Fluorescence, Raman and Singlet Oxygen Generation." University of Cincinnati / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1460444904.
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Махонін, Микола Віталійович. "Метод визначення параметрів генератору медичного озону для ефективного підвищення його продуктивності." Thesis, Національний технічний університет "Харківський політехнічний інститут", 2019. http://repository.kpi.kharkov.ua/handle/KhPI-Press/42014.
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Дисертація на здобуття наукового ступеня кандидата технічних наук за спеціальністю 05.11.17 – біологічні та медичні прилади і системи. Національний технічний університет «Харківський політехнічний інститут», Харків, 2019 р. Дисертацію присвячено розробці методу визначення параметрів генератору медичного озону для ефективного підвищення його продуктивності за рахунок визначення параметрів його частин з урахуванням впливу факторів різної природи. На основі дослідження питання побудови генераторів медичного озону була доведена актуальність дослідження шляхів підвищення його ефективності. Наведені основні фактори, що впливають на продуктивність генератора озону. Запропонована математична модель на основі використання елементарного об’єму , що описує процеси, які відбуваються у розрядній камері при подачі напруги. Розроблено метод визначення параметрів розрядної камери генератору медичного озону, який дозволяє отримати найбільш ефективну конструкцію при заданих режимах роботи. Проведено дослідження розробленної автоматичної системи витрати робочого газу з поліпшеними характеристиками, яка дозволяє здійснювати основні методики озонотерапії. Доведена працездатність даної системи на основі роботи макета генератора медичного озону при проходженні медичної апробації.Thesis for the degree of candidate of technical sciences in specialty 05.11.17 – biological and medical devices and systems. – National Technical University "Kharkіv Polytechnic Institute", Kharkіv, 2019. The thesis is devoted to the development of a method for determining the parameters of a medical ozone generator to effectively increase its productivity by determining the parameters of its constituent parts, taking into account the influence of factors of different nature. On the basis of the study of the issues of constructing generators of medical ozone, the relevance of the study of ways to increase its efficiency was proved. A mathematical model based on the use of a single volume, which describes the processes occurring in the discharge chamber when the voltage is applied, is proposed. The level of influence of the parameters of the working gas and the geometry of the discharge chamber on the performance of the ozone generator, as well as on the stability of the parameters of the ozone-oxygen mixture, which were set. A method has been developed for calculating the parameters of a discharge chamber of a medical ozone generator, which makes it possible to obtain the most efficient design for given operating modes. A study has been carried out on the development of an automated working gas consumption system with improved characteristics, which makes it possible to carry out the main methods of ozone therapy. The efficiency of this system has been proved on the basis of the work of a medical ozone generator layout during the passage of medical approbation.
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Guo, Mengqing. "Catalytic Modification of Oxygen Carriers for Chemical Looping Applications." The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1564572229572212.
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Muhammed, Najya. "Singlet oxygen generation and photo-oxidation reactions in supercritical fluid carbon dioxide." Thesis, Loughborough University, 2009. https://dspace.lboro.ac.uk/2134/33632.
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Oxygen is remarkable in that it has a triplet ground state, a 3Σg state, with its first two excited states being of singlet multiplicity (1Δg and 1Σg+, lying 94 kJ mol-1 and 158 kJ mol-1 above the ground state, respectively). Relaxation of the singlet state to the ground state is consequently spin forbidden, resulting in a long lifetime for singlet oxygen: Singlet oxygen is a highly reactive species and is responsible for oxidative damage in a number of systems. In this study, singlet oxygen quantum yields, ΦΔ, have been measured at varying temperatures and pressures, as a function of oxygen concentration, in supercritical fluid carbon dioxide.
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Bresolí, Obach Roger. "Novel strategies for singlet molecular oxygen O2(1Δg) generation and detection in cells." Doctoral thesis, Universitat Ramon Llull, 2018. http://hdl.handle.net/10803/662972.
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En aquesta tesi s'han utilitzat diferents estratègies per obtenir control en la producció i detecció de diferents espècies reactives d'oxigen (ROS), especialment per a l'oxigen singlet (1O2).
En la primera part de la tesi, l'enfoc principal consisteix en entendre la generació de ROS i intentar potenciar-ne el seu efecte. En primer lloc, demostrem que la modificació de diferents fotosensibilitzadors afegint-hi un catió de trifenilfosfoni com a element diana produeix derivats amb una excel·lent activitat fotoantimicrobiana contra bacteris Gram-positius (S. aureus i E. faecalis). En segon lloc, descobrim una sèrie de nous aspectes de la reacció de “-phenyl quenching” per derivats de 9-fenilfenalenona. La fototoxicitat d’aquests derivats ja es troba esmentada en el llibre: “L'origen de les espècies” de C. Darwin. També es suggereix una via metabòlica mediada per la reacció BPQ en la biosíntesi dels pigments vegetals derivats de fluorones. A més, si el grup fenil és substituït per altres grups arils, s'observa diferencies en la reacció de BPQ. En tercer lloc, s’ha demostrat que diferents antraquinones d’origen natural indueixen fototoxicitat en biofilms de C. tropicalis a causa de la generació de O2•, tenint l’1O2 un rol menor. En quart lloc, es demostra el fàrmac antitumoral Doxorubicina produeix quantitats significants d’1O2, però es redueix la seva generació quan es complexa amb el ADN. En cinquè lloc, s’ha estudiat l’efecte d’adsorció o unió covalent d’un fotosensibilitzador a nanopartícules mesoporoses de sílice. A més a més, s’han derivatitzat per afegir-hi elements diana. Sisè i últim, s’ha estudiat les propietats fotoquímiques d’una nova diada que conté un bromo-bodipy com a fotosensibilitzador i trampa química de ROS (que desactiva la capacitat del bromo-bodipy de generar 1O2). Un cop oxidada la trampa química, la diada recupera la capacitat de generar 1O2 i causar dany cel·lular. S’observa diferents propietats foto-antitumorals d’aquesta diada en funció de l’estrès cel·lular o de la localització cel·lular.
En la segona part de la tesi, s'ha centrat en la detecció de ROS. En primer lloc, s’han dissenyat, sintetitzat i caracteritzat nanosondes fluorescents per la detecció d'1O2 en sistemes biològics. La nanovehiculització elimina algunes de les limitacions de les diferents sondes fluorescents d’1O2. En aquest sentit, diverses sondes tals com SOSG, ADPA o furil-vinil-naftooxazol s’han unit covalentment a nanopartícules utilitzant diferents cadenes espaiadores per tal d’optimitzar la seva reactivitat front 1O2. A diferència de quan es troben lliures en solució, les nanosondes són fàcilment internalitzades per cèl·lules eucariotes i procariotes i es minimitza la interacció amb proteïnes (com per exemple, l’albúmina de sèrum boví). Les diferents nanosondes responen a l’1O2 generat intracel·lular. Com a prova de concepte, també s’ha desenvolupat una nanosonda fluorescent per la detecció no selectiva de ROS, basada en 2’,7’-diclorodihidrofluoresceina. En segon lloc, s’ha caracteritzat la estructura i reactivitat de la sonda fluorescent: CellROX Deep Red. En tercer lloc, s’ha desenvolupat la primera sonda d’optoacústica per la detecció de ROS basada en l’oxidació de la tetrametilbenzidina. S’ha aconseguit detectar 1O2 produït per bacteris utilitzant tal sonda.
Finalment i com a prova de concepte, s’ha dissenyat un “self-reporter” nanofotosensibilitzador. El nanosistema és capaç de produir i detectar 1O2 simultàniament. Aquest nanodispositiu s'ha utilitzat amb èxit per la fotoinactivació de S. aureus, observant-se una correlació entre el canvi de fluorescència de la sonda i la mort bacteriana.En esta tesis se han utilizado distintas estrategias para obtener el control en la producción y detección de diferentes especies reactivas de oxígeno (ROS), especialmente para el oxígeno singlete (1O2). En la primera parte de la tesis, el enfoque principal consiste en entender la generación de ROS e intentar potenciar su efecto. En primer lugar, demostramos que la modificación de distintos fotosensibilizadores, añadiendo un catión de trifenilfosfonio como elemento diana, produce derivados con una excelente actividad fotoantimicrobiana contra bacterias Gram-positivas (S. aureus y E. faecalis). En segundo lugar, descubrimos una serie de nuevos aspectos de la reacción de "-phenyl quenching" por derivados de 9-fenilfenalenona. La fototoxicidad de estos derivados ya se encuentra mencionada en el libro: "el origen de las especies" de C. Darwin. También se sugiere una vía metabólica mediada por la reacción BPQ en la biosíntesis de los pigmentos vegetales derivados de fluorenonas. Además, si el grupo fenilo es sustituido por otros grupos arilos, se observan diferencias en la reacción de BPQ. En tercer lugar, se ha demostrado que distintas antraquinonas de origen natural inducen fototoxicidad en biofilms de C. tropicalis debido a la generación de O2•, teniendo el 1O2 un rol menor. En cuarto lugar, se demuestra que el fármaco antitumoral Doxorubicina produce cantidades significantes de 1O2, pero se reduce su generación cuando se compleja con el ADN. En quinto lugar, se ha estudiado el efecto de adsorción o unión covalente de un fotosensibilizador a nanopartículas mesoporosas de sílice. Además, se han derivatizado para añadir elementos diana. Sexto y último, se han estudiado las propiedades fotoquímicas de una nueva diada que contiene un bromo-bodipy como fotosensibilizador y trampa química de ROS (que desactiva la capacidad del bromo-bodipy para generar 1O2). Una vez oxidada la trampa química, la diada recupera la capacidad para generar 1O2 y causar daño celular. Se observan diferentes propiedades foto-antitumorales de esta diada en función del estrés celular o de la localización celular. La segunda parte de la tesis, se ha centrado en la detección de ROS. En primer lugar, se han diseñado, sintetizado y caracterizado nanosondas fluorescentes para la detección de 1O2 en sistemas biológicos. La nanovehiculización elimina algunas de las limitaciones de las distintas sondas fluorescentes de 1O2. En este sentido, varias sondas tales como SOSG, ADPA o furilo-vinilo-naftooxazol se han unido covalentemente a nanopartículas utilizando distintas cadenas espaciadoras para optimizar su reactividad frente 1O2. A diferencia de cuando se encuentran libres en solución, las nanosondas son fácilmente internalizadas por células eucariotas y procariotas y se minimiza la interacción con proteínas (como por ejemplo con la albúmina de suero bovino). Las distintas nanosondas responden al 1O2 generado intracelular. Como prueba de concepto, también se ha desarrollado una nanosonda fluorescente para la detección no selectiva de ROS, basada en 2',7'-diclorodihidrofluoresceina. En segundo lugar, se ha caracterizado la estructura y reactividad de la sonda fluorescente: CellROX Deep Red. En tercer lugar, se ha desarrollado la primera sonda de optoacústica para la detección de ROS basada en la oxidación de la tetrametilbenzidina. Se ha logrado detectar 1O2 producido por bacterias emprando tal sonda. Finalmente, y como prueba de concepto, se ha diseñado un "self-reporter" nanofotosensibilitzador. El nanosistema es capaz de producir y detectar 1O2 simultáneamente. Este nanodispositivo ha sido utilizado con éxito para la fotoinactivación de S. aureus, observándose una correlación entre el cambio de fluorescencia de la sonda y la muerte bacteriana.
In this thesis, different strategies have been used in order to gain control in reactive oxygen species (ROS) production and detection, especially for singlet oxygen (1O2). In the first part of the thesis, the main focus is towards understanding ROS generation and try to potentiate its effect. First, we demonstrate that modification of different photosensitisers with the triphenylphosphonium cation yields derivatives with an excellent photoantimicrobial activity against Gram‐positive bacteria (i.e., S. aureus and E. faecalis). Second, we uncover a number of new aspects of -phenyl quenching reaction in 9-phenylphenalenone scaffold, whose phototoxicity was already mentioned in Darwin’s Origin of Species. It is suggested an excited state-mediated metabolic pathway in the biosynthesis of fluorone plant pigments. Moreover, if phenyl moiety is substituted for other aryl groups, it is observed that the electrocyclic ring opening back to ground state ketones have lifetimes between miliseconds and picoseconds. Third, we demonstrate that the main photosensitizing mechanism, involved in the photo-induced C. tropicalis antibiofilm activity by natural anthraquinones, is via O2• production, whereas 1O2 participation seems of lesser importance. Fourth, we demonstrate that doxorubicin produces significant amounts of 1O2, however, this is largely suppressed when bound to DNA. Fifth, we studied the effect of PS adsorption or covalently bond onto the surface of mesoporous silica nanoparticles. Moreover, we further derivatitze them for attach targeting elements. Sixth and last, we studied the activation a new dyad comprising a bromo-bodipy, which acts as PS, plus a non-selective ROS chemical trap, which quenches the ability of bromo-bodipy to produce 1O2. For that aPS we observe a differential behaviour in function of the cellular stress or even in function of the organelle. In the second part of the thesis, focus has been shifted towards ROS detection. First, we designed, synthesized, and characterized biocompatible fluorescent nanoprobes for 1O2 detection in biological systems that circumvents many of the limitations of the different molecular 1O2 fluorescent probes. Under that purpose different 1O2 probes (Singlet Oxygen Sensor Green, anthracene dipropionic acid and furyl-vinyl-naphthoxazole) were covalently linked to nanoparticles core using different architectures to optimize their response to 1O2. In contrast to its molecular counterpart, the optimum nanoprobes are readily internalized by prokaryotic and eukaryotic cells and they do not interact with proteins (i.e. bovine serum albumin). Furthermore, the spectral characteristics do not change inside cells, and the probe responds to intracellular generated 1O2 with the corresponding change in fluorescence. As a proof of concept, a non-selective ROS fluorescent nanoprobe, based on diacetyl 2’,7’-dichlorodihydrofluorescein, has been synthetized and successfully used for detecting intracellular ROS. Second, we have performed the chemical characterization of the CellROX Deep Red, a new commercial non-selective ROS fluorescent probe, ascertained its putative chemical structure and evaluated its reactivity towards different reactive oxygen/nitrogen species and light in solution. Third, we developed the first ROS optoacoustic probe based on the oxidation of tetramethylbenzidine and successfully used for detecting 1O2 produced by bacteria. Finally, as proof of concept we have designed a self-reporter nanophotosensitizer. The nanosystem is capable to produce and detect the 1O2 generated simultaneously. It has been successfully used for S. aureus photoinactivation in which a correlation was observed between fluorescent change of the probe and bacterial cellular death.
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Seotsanyana-Mokhosi, Itumeleng. "Photosensitizing properties of non-transition metal porphyrazines towards the generation of singlet oxygen." Thesis, Rhodes University, 2001. http://hdl.handle.net/10962/d1006086.
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Metallophthalocyanine complexes containing non-transition metals are very useful as sensitizers for photodynamic therapy, a cure for cancer that is based on visible light activation of tumour localized photo sensitizers. Excited sensitizers generate singlet oxygen as the main hyperactive species that destroy the tumour. Water soluble sensitizers are sought after for the convenience of delivery into the body. Thus, phthalocyanine (pc), tetrapyridinoporphyrazines (tppa) and tetramethyltetrapyridinoporphyrazines (tmtppa) with non-transition central metal atoms of Ge, Si, Sn and Zn were studied. First was the synthesis of these complexes, followed by their characterisation. The characterisation involved the use of ultraviolet and visible absorption spectroscopy, infrared spectroscopy, nuclear magnetic resonance spectroscopy, electrochemical properties and elemental analysis. Photochemical properties of the complexes were then investigated. Photolysis of these macrocycles showed two processes; -reduction of the dye and photobleaching, which leads to the disintegration of the conjugated chromophore structure of the dye. Photobleaching is the reductive quenching of the excited state of the sensitizers. The intensity of the quenching decreased progressively from tmtppa, tppa to pc metal complexes with photobleaching quantum yields, 6.6 x 10.5⁻¹, 1.8 x 10.5⁻¹ and 5.4 x 10⁻⁶ for Zntmtppa, Zntppa and Znpc, respectively. Efficiency of singlet oxygen sensitization is solvent dependent with very different values obtained for the same compound in different solvents, for example, 0.25 and 0.38 were observed as singlet oxygen quantum yields for Gepc complex in DMSO and DMF respectively. In DMSO the efficiency of ¹O₂ generation decrease considerably from pc to tppa and finally tmtppa. In water Getmtppa exhibits much higher singlet oxygen quantum yield, hence promising to be effective as a sensitizer for photodynamic therapy.
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Hamedi, Rad Mina. "Processing and Evaluation of Next Generation Oxygen Carrier Materials for Chemical Looping Combustion." University of Toledo / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1433242011.
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Åsman, Björn. "Juvenile periodontitis generation of free oxygen radicals and elastase by peripheral PMN cells /." Stockholm : Kongl. Carolinska Medico Chirurgiska Institutet, 1988. http://catalog.hathitrust.org/api/volumes/oclc/18171198.html.
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Guillodo, Michaël. "Membrane céramique BIMEVOX pour application dans un générateur électrochimique à oxygène : caractérisations électrochimiques et physico-chimiques." Université Joseph Fourier (Grenoble), 2001. http://www.theses.fr/2001GRE10088.
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Cette etude s'inscrit dans le cadre d'un contrat de programme de recherche (cpr) entre la societe air liquide et le cnrs. Ce cpr porte sur la faisabilite de nouveaux materiaux ceramiques a base de bimevox dans une application generateur ceramique a oxygene (cog : ceramic oxygen generator) afin d'abaisser la temperature de fonctionnement de ceux-ci. L'utilisation d'echantillons denses de bimevox0. 10 (me = cu, co) d'architecture et de microstructure homogenes permet d'obtenir des proprietes electriques stables, reproductibles et independantes de l'histoire thermique du materiau. A 600\c sous air, le bicuvox0. 10 se comporte comme un electrolyte solide alors que le bicovox0. 10 est caracterise par une conductivite electronique de type p avec un nombre de transport ionique de 0,985 dans les memes conditions. Le domaine de stabilite redox est fixe respectivement par un potentiel cathodique de 0,4 v/air (couple cuo/cu) et 0,53 v/air (couple bi 2o 3/bi) pour le bicuvox0. 10 et le bicovox0. 10. Le mecanisme de reduction de la solution solide de bicuvox0. 10 presente une etape intermediaire irreversible. Les proprietes d'echange de l'oxygene, determinees par sims, ont permis de montrer que le coefficient d'echange de l'oxygene vis-a-vis de ces materiaux est mediocre et qu'il est necessaire d'adjoindre des electrodes presentant des proprietes electrocatalytiques pour la dissociation et la recombinaison de l'oxygene moleculaire. Les mesures de flux de semi-permeabilite electrochimique a l'oxygene corroborent ce dernier point et montrent que l'emploi d'un conducteur mixte permet de catalyser les reactions en surface des membranes ceramiques. Le developpement d'electrodes composites (melange perovskite/bimevox) a permis de valider la notion d'electrode a gradient de composition (egc) composee de trois couches successives, deposees par serigraphie sur l'electrolyte solide. L'importance de de l'architecture et de la microstructure de l'electrode egc a temperature intermediaire (microstructure de la premiere couche, homogeneisation du melange, taille de grains, porosite et epaisseur des couches) a ete mise en evidence. D'un point de vue technologique, les tests de systemes symetriques (anode/electrolyte solide/cathode) sous conditions operatoires continues (0,15 a cm - 2 a 600\c sous air pendant 500 heures) ont montre une destabilisation irreversible du bicuvox0. 10 apres 200 heures. Le bicovox0. 10, dans des conditions d'elaboration, d'architecture et de microstructure optimisees, presente une stabilite en potentiel apres 1000 heures de fonctionnement. Cependant, une degradation physico-chimique irreversible a ete observee (formation du compose bivo 4). Les instabilites et les degradations des bimevox0. 10 sont d'origine electrochimique et liees aux proprietes redox de ces materiaux. Par consequent, ces materiaux ne presentent pas d'interets industriels dans une application it-cog.
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Andrasik, Stephen James. "Singlet Oxygen Generation Using New Fluorene-Based Photosensitizers Under One- and Two-Photon Excitation." Doctoral diss., University of Central Florida, 2007. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/2210.
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Molecular oxygen in its lowest electronically excited state plays an important roll in the field of chemistry. This excited state is often referred to as singlet oxygen and can be generated in a photosensitized process under one- or two-photon excitation of a photosensitizer. It is particularly useful in the field of photodynamic cancer therapy (PDT) where singlet oxygen formation can be used to destroy cancerous tumors. The use of two-photon activated photosensitizers possesses great potential in the field of PDT since near-IR light is used to activate the sensitizer, resulting in deeper penetration of light into biological tissue, less photo-bleaching of the sensitizer, and greatly improved resolution of excitation. The synthesis and photophysical characterization of new fluorene-based photosensitizers for efficient singlet oxygen production were investigated. The spectral properties for singlet oxygen production were measured at room temperature and 77 K. Two-photon absorption (2PA) cross-sections of the fluorene derivatives were measured by the open aperture Z-scan method. The quantum yields of singlet oxygen generation under one- and two-photon excitation ([Phi][sub Delta] and 2PA[Phi][sub Delta], respectively) were determined by the direct measurement of singlet oxygen luminescence at ≈ 1270 nm. The values of [Phi][sub Delta] were independent of excitation wavelength, ranging from 0.6 - 0.9. The singlet oxygen quantum yields under two-photon excitation were 2PA[Phi][sub Delta] ½[Phi][sub Delta, indicating that the two processes exhibited the same mechanism of singlet oxygen production, independent of the mechanism of photon absorption.Ph.D.
Department of Chemistry
Sciences
Chemistry PhD
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Burkitt, Mark John. "The role of iron in the generation and toxicity of oxygen-centred free radicals." Thesis, University of York, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.329652.
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Lavado, Andrea Sofia Caetano das Neves. "Porphyrinic-nanoplatforms : controlled intracellular generation of reactive oxygen species in human mesenchymal stem cells." Thesis, University of Nottingham, 2014. http://eprints.nottingham.ac.uk/14200/.
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Reactive Oxygen Species (ROS) are known as important intracellular signaling molecules. These are also well known for their role in oxidative stress and cellular damage, leading to their involvement in several pathologies. Despite the widespread postulation of ROS mechanisms, little is actually known about the immediate response in living cells to the generation of these highly reactive compounds. The development of nanoplatforms incorporating photosensitizers would permit the generation of ROS at specific sub-cellular locations and determine the in situ cellular response. The work presented in this thesis describes the development of porphyrinic nanoplatforms for the controlled generation of ROS and investigates their impact on the surface marker expression of human Mesenchymal Stem Cells (hMSCs). Surface tailoring of polyacrylamide nanoparticles with alkyne and amine functionalities were exploited to achieve stable reactive chemical groups for further conjugation. Nanoplatforms surface was also modulated with trimethylammonium functionalities for the development of nanosystems for sub-cellular targeting and facilitated uptake. Physicochemical characterization of alkyne and alkyne/trimethylammonium functionalised constructs showed sizes in the range of 40 nm with a positive surface charge. Alkyne/trimethylammonium nanosystemswere found to be stable over long periods of time, whilst amino functionalized nanosystems were found to be prone to aggregation. Mechanisms of conjugation were exploited to create covalent linkage of porphyrinic photosensitizers to mono and dually functionalised constructs. Conjugation through "click chemistry" allowed stable coupling with alkyne and alkyne/trimethylammonium nanosystems. To overcome aggregation associated with amino functionalised nanoplatforms, porphyrin conjugated monomers were synthesised which resulted in stable polyacrylamide nanoparticles. The developed conjugated nanosystems showed final sizes in the range 40-100 nm, while conjugates with surface charges greater than + 20 mV have led to sizes higher than 100 nm. The effect of surface charge on cellular delivery was investigated and nanosystems with a surface charge in the range + 13 mV to + 18 mV proved optimal in terms of cell delivery and viability. It was found that highly charged nanosystems (above + 20 mV) remained attached to the cellular membrane and had a negative effect on cell viability. In addition, intracellular co-localisation studies showed preferential mitochondrial targeting of the delivered nanosystems. Production of ROS in nanoparticle treated hMSCs was achieved by exposure to light at wavelength of 575 nm. For porphyrin conjugated nanosystems a single light dosage resulted in a "blast zone" in the irradiated area where significant production of hydrogen peroxide was also observed. Titration of the amount of porphyrin conjugated at the surface of nanoparticles resulted in systems with different levels of ROS production. Control of ROS generation allowed development of a nanoplatform that was used to expose cells to repeated exposure of ROS over a time period of 100 minutes. The surface marker expression of hMSCs treated with porphyrin conjugated nanosystems was investigated. In the absence of light the surface marker expression of hMSCs was maintained, positive for CD29 and CD105 and negative for CD34 and CD45. Increased generation ROS in hMSCs did not produce alterations in the surface marker expression of cells, and over two generations of treated cells (light and nanoparticles) no changes were detected in surface marker expression. The developed nanoplatforms have the potential to be applied as a tool to investigate the cellular mechanisms and metabolism associated with different levels of oxidative stress. In addition, these nanosystems could also represent an innovative platform for theranostic applications (drug delivery/diagnostic).
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Han, Jin-Soon Brockman Herman E. "Effects of active oxygen species generated from hydrogen peroxide in Neurospora crassa and Salmonella typhimurium." Normal, Ill. Illinois State University, 1991. http://wwwlib.umi.com/cr/ilstu/fullcit?p9203030.
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Thesis (Ph. D.)--Illinois State University, 1991.Title from title page screen, viewed December 8, 2005. Dissertation Committee: Herman E. Brockman (chair), Radheshym K. Jayaswal, Alan J. Katz, David F. Weber, Brian J. Wilkinson. Includes bibliographical references (leaves 113-125) and abstract. Also available in print.
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Barbosa, dos Santos Freitas e. Sousa João. "Microplasma generation of high fluxes of singlet delta oxygen at atmospheric pressure for biomedical applications." Paris 11, 2010. http://www.theses.fr/2010PA112303.
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Dans ce travail, nous avons étudié expérimentalement la production à pression atmosphérique d'oxygène singulet delta, O2(a1Δg), par micro-plasmas. Nous avons développé un type particulier de microdécharges, appelées MCSD (micro-cathode sustained discharges) aptes à produire, en régime continu, des décharges luminescentes exemptes de transition en régime d'arc. Au moyen de diagnostics électrique et optique, le champ électrique réduit (E/N), la température du gaz (Tgaz), les profils de densité de l'oxygène atomique, la distribution spatiale de l'ozone, ainsi que la densité de O2(a1Δg) ont été obtenus pour de nombreuses conditions expérimentales. Nos résultats montrent que les MCSD se comportent essentiellement comme des colonnes positives à haute pression, caractérisées par des faibles valeurs de E/N (5-20 Td) et de Tgaz (300-700 K). Les MCSD ont ainsi toutes les caractéristiques requises pour générer efficacement l'état O2(a1Δg). L'optimisation du fonctionnement en parallèle de plusieurs MCSD nous a permis d'obtenir à pression atmosphérique, et de transporter sur plusieurs dizaines de cm, des densités d'O2(a1Δg) supérieures à 10 puissance17 cm-3. Soulignons que, grâce à leur remarquable stabilité, les MCSD sont, à ce jour, les seules décharges permettant de produire des flux importants d' O2(a1Δg) à pression atmosphérique. La source d'O2(a1Δg) étudiée dans ce travail, bien caractérisée et d'une grande fiabilité, est maintenant susceptible d'applications novatrices, en particulier dans le domaine biomédical. Nous avons pu démontrer son efficacité pour l'étude de l'oxydation de l'ADN, et en collaboration avec des biologistes, nous avons déterminé la nature des lésions produites par O2(a1Δg)Atmospheric pressure generation of singlet delta oxygen (SDO) by microplasmas has been experimentally studied. Ln this work, we have used a specific type of microdischarges, called MCSD (microcathode sustained discharges), which have allowed the operation of DC glow discharges, free from the glow-to-arc transition. From electrical and optical diagnostics, the reduced electric field (E/N), the gas temperature (Tgas), the atomic oxygen density profiles, the ozone spatial distribution, as weIl as the SDO density have been obtained for several operating conditions. Our results show that MCSD are similar to high-pressure positive columns, with low values of E/N (5-10 Td) and of Tgas (300-700 K). Thus, MCSD fulfill aIl the required characteristics for an efficient production of SDO. It must be pointed out that, due to its remarkable stability, the MCSD is, to this date, the only discharge technique that has been proven capable of generating high fluxes of SDO at atmospheric pressure. By optimizing the operation of arrays of several MCSD, we have efficiently produced and transported at atmospheric pressure, over distances longer than 50 cm, SDO densities higher than 10 to the power of 17 cm-3. Additionally, O3 densities up to 10 to the power of 16 cm-3 have also been obtained. As the ratio density of SDO to O3 can be finely and easily tuned in the range [10 to the power of -2 - 10 to the power of +5], our plasma source is unique in the context of the new research field of Plasma Medicine. Indeed, we have shown that arrays of MCSD are very useful tools for examining in detail the reactivity of these reactive oxygen species towards DNA. Ln collaboration with biologists, we have determined the damages induced in DNA by SDO and O3
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Ash, Catherine Elizabeth. "Functional and molecular mechanisms underlying reduced mitochondrial reactive oxygen species generation under dietary restricted feeding conditions." Thesis, University of Liverpool, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.494167.
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Dietary restriction (DR) across a wide phylogenetic range increases both mean and maximal lifespan by retarding the ageing process and delaying the onset and incidence of age-related pathologies. DR animals exhibit reduced tissue oxidative damage but anti-oxidant enzyme activities and other defence mechanisms against reactive oxygen species (ROS) are not consistently upregulated In such animals. As an alternative explanation ROS generation was Studied in isolated mitochondria from tissues of DR rats. About 90% of cellular ROS generation is thought to result from the single electron transfer to molecular oxygen within the mitochondria. Indeed mitochondria isolated from a range of tissues from DR rats had lower rates of H2O2 generation when compared to age matched control animals, whilst mitochondrial state III and IV respiration rates were unaltered.
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Schroeter, Sandra. "Reactive oxygen and hydrogen species generation in radio-frequency atmospheric pressure plasmas : experimental and numerical investigations." Thesis, University of York, 2017. http://etheses.whiterose.ac.uk/18738/.
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Atmospheric pressure plasmas (APPs) are known to be effective sources for reactive oxygen and nitrogen species (RS), making them potentially suitable for applications in biomedicine, where these species are believed to play a crucial role. However, in order to fully establish plasma sources in biomedicine, detailed characterisation of the RS produced is required. This is particularly challenging at atmospheric pressure, because of high collision rates among particles leading to fast de-excitation of excited states (quenching), complex gas mixing, and the small physical dimensions of the investigated systems, which effectively limits the accurate application of several commonly used diagnostic techniques applicable in low pressure systems. The motivation of this work is therefore to investigate the chemical kinetics in APPs, using a combination of simulations and experimental diagnostics, which are able to overcome the above-mentioned challenges. Experimentally, absolute RS species densities such as O, OH, H2O2, N, and NO, are determined using absorption spectroscopy in the UV and VUV spectral range, a technique independent on quenching and providing high spectral resolution. Spatially resolved two-photon absorption laser-induced fluorescence with sub-nanosecond temporal resolution enables the determination of atomic species densities (O and H) in the plasma effluent. Experimental values are benchmarked against zero-dimensional plasma-chemical kinetics simulations, which are used to investigate the principal reaction mechanisms leading to the formation and consumption of the investigated species. It is generally found that formation pathways depend strongly on the concentration of molecules in the feed gas, and the position in the plasma jet, as well as potential impurities being present in the feed gas, which is an important aspect for consideration for the applications of APPs. The results are used to propose possible tailoring schemes to optimise RS productions in APPs.
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Wang, Xuan Verfasser], and Henning Jacob [Akademischer Betreuer] [Jessen. "Toxicity of singlet oxygen generated from water-soluble anthrancene endoperoxides or trehalose-photosensitizer conjugates against bacteria." Freiburg : Universität, 2021. http://d-nb.info/1238517617/34.
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Hargreaves, Aspasia. "Biological sensitizers of near UV : generation of reactive oxygen species and damage to cellular components and microbes." Thesis, Nottingham Trent University, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.366086.
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Hoffman, Marjorie A. "Generation of DNA-damaging reactive oxygen species via the autoxidation of hydrogen sulfide under physiologically relevant conditions." Thesis, University of Missouri - Columbia, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10180877.
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Hydrogen sulfide (H2S) is more commonly known for its toxic properties; however, recently, there has been evidence that this small, gaseous molecule could serve as an endogenous cell-signaling agent. Surprisingly, a number of studies have also provided evidence that H 2S is a DNA-damaging mutagen. Using a plasmid-based DNA strand cleavage assay, we examined the chemical mechanisms of DNA damage by H2S. We found single-strand DNA cleavage was caused by micromolar concentrations of H2S. The mechanistic process was studied and was shown to involve the autoxidation of H2S to generate superoxide, hydrogen peroxide, and ultimately hydroxyl radical, a well-known DNA-damaging agent, via a trace metal-mediated Fenton-type reaction. In the presence of physiological thiol concentrations, DNA strand cleavage by H2S still occurred. The oxidation byproducts of H2S, such as thiosulfate, sulfite, and sulfate, do not contribute to DNA strand cleavage. However, the initially generated oxidation products, like persulfide (S22-), most likely go through rapid autoxidation reactions, which contribute to superoxide generation. This autoxidation process is of potential relevance to both the genotoxic and cell signaling properties of H2S.
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CLAY, COREY DAVIS. "AN EVALUATION OF TCDD AND POLYHALOGENATED BIPHENYL MEDIATED REACTIVE OXYGEN GENERATION BY CYTOCHROMES P4501A1, P4501A2 AND P4502E1." University of Cincinnati / OhioLINK, 2003. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1061220136.
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Perng, John Kangchun. "Ultrasound imaging of oxidative stress in vivo with chemically generated gas microbubbles." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/43608.
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Ultrasound contrast agents (UCA) have tremendous potential for in vivo molecular imaging because of their high sensitivity and great spatial resolution of ultrasound imaging. However, the diagnostic potential of UCAs has been difficult to exploit because current contrast agents are based on pre-formed microbubbles, which can only detect cell surface receptors. In this work, we demonstrated that chemical reactions that generate gas forming molecules can be used to perform molecular imaging by ultrasound in vivo. This new approach for generating ultrasound contrast agents was demonstrated by imaging reactive oxygen species (ROS) in vivo with allylhydrazine, a compound that is converted into nitrogen and propylene gas after reacting with radical oxidants. We demonstrated that allylhydrazine encapsulated within liposomes (termed APLs) can detect a 10 uM concentration of radical oxidants by ultrasound, and can image oxidative stress in mice, induced by lipopolysaccharide (LPS), using a clinical ultrasound machine. We showed that a 1-2% increase in gas concentration above saturation can be detected acoustically and suggest that numerous biological targets can be imaged via appropriately designed gas forming reactions. This work was the first demonstration of in vivo imaging of ROS using ultrasound, and this work presented a new strategy to generate gas bubbles from reactions involving radical oxidants. We anticipate numerous applications of chemically generated microbubbles, given the excellent spatial resolution of ultrasound imaging, its widespread clinical use and its high sensitivity to detect gas bubbles.
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Drew, Dana. "An Isotopic, Trace Element, and Volatile Investigation of Large-Volume Rhyolite Generation at the Picabo Volcanic Field of the Yellowstone Hotspot Track." Thesis, University of Oregon, 2014. http://hdl.handle.net/1794/17894.
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Rhyolites of the Picabo volcanic field (10.4-6.6 Ma) of the Yellowstone hotspot in eastern Idaho are preserved as thick ignimbrites and lavas along the margins of the Snake River Plain. This study presents new O and Hf isotope data and U-Pb geochronology from individual zircons, O isotope data from major phenocrysts, whole rock Sr and Nd isotope data, whole rock geochemistry, and trace element and volatile analyses of quartz-hosted melt inclusions, which were used to characterize the evolution of rhyolite generation through the eruptive sequence. The chemical composition of the first eruption of the caldera complex, the Tuff of Arbon Valley, suggests magma generation through repeated magma injection into the crust, remelting, crystallization, mixing, and crustal assimilation. Subsequent eruptions have diverse and low δ18O signatures indicating rhyolite generation through the remelting of variably hydrothermally altered volcanics, followed by rapid batch assembly.
This thesis includes co-authored material previously published.
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Lucas, Stephen Marc. "Valproic Acid Leads to an Increase in ROS Generation by Inhibiting the Deacetylation of Mitochondrial SOD." BYU ScholarsArchive, 2020. https://scholarsarchive.byu.edu/etd/9247.
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Valproic Acid Promotes Acetylation of Superoxide Dismutase-2 During Neurogenesis. Valproic acid (VPA) is a known developmental toxicant associated with a high prevalence of neural tube defects (NTD). The mechanism of VPA-induced NTD is unclear, but oxidative stress may be implicated. To understand how embryotoxic oxidative stress may occur, we measured superoxide dismutase (SOD) activity following VPA treatment in the embryonic pluripotent P19 mouse carcinoma cell line. In undifferentiated P19 cultures treated with VPA (5 mM), dichlorofluorescein fluorescence increased 15% compared to untreated controls over 20 min, indicating a modest, yet statistically significant increase in ROS generation. Undifferentiated P19 cells were treated with VPA for 6 h, after which total SOD and mitochondrial SOD (SOD2) activities were measured. VPA treatment decreased total SOD activity by approximately 20% but SOD2 activity was undetectable; but this was not a consequence of changes to SOD (SOD1 or SOD2) protein concentrations. Interestingly, glutathione redox state increased from -262 mV to -245 mV after a 6 h treatment with VPA, indicating significant oxidation of the cellular redox environment. Measurement of mitochondrial superoxide levels showed an increase following VPA treatments. While it is unlikely that VPA works directly as an oxidant, these data suggest that VPA may promote oxidative stress through an alternative means, such as via the inhibition of SOD activity and thus, allow for an increase in ROS. Importantly, VPA is a known deacetylase inhibitor, and SOD2 function is regulated by acetylation. As such, we evaluated the acetylation state of SOD2 to determine potential disruption via acetylation. Treated undifferentiated P19 cells showed a significant increase in SOD2 acetylation. However, in fully differentiated P19-derived neurons, cells showed no such SOD2 acetylation. Additionally, pretreatment with dithiole-3-thione (D3T), a Nrf2 activator of the antioxidant response, attenuated VPA-induced mitochondrial ROS production and SOD2 acetylation and improved SOD2 activity, suggesting Nrf2 as a potential means to reduce VPA-mediated oxidative stress. To evaluate the effects in the embryo proper, gestational day 8 mouse embryos were treated with VPA in culture for 6 h. Similar to P19 cells, VPA-treated neurulating embryos showed significant SOD2 acetylation and a concomitant decrease in total SOD activity. These data support a similar consequence of VPA-induced oxidative stress in embryos as is demonstrated in our cellular model. Since no SOD2 acetylation is observed in differentiated neurons and VPAinduced SOD2 acetylation occurs more prevalently in undifferentiated/differentiating cells, these data purport means by which VPA preferentially induces oxidative stress in developing systems.
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Shi, Ping. "Experimental study of phase relationships in part of the system Mg-Fe-Ca-Ti-Si-O at 1300°C, 1atm, and various oxygen fugacities, with applications to redox partial melting." Thesis, University of Edinburgh, 1989. http://hdl.handle.net/1842/11911.
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González, Forero Danilo. "Automatized Nanoparticle Models Generation and Application to the Oxygen Evolution Reaction Catalyzed by IrO2. Slab vs Nanoparticle Models." Doctoral thesis, Universitat Autònoma de Barcelona, 2020. http://hdl.handle.net/10803/671127.
Full textAbstract:
Les nanopartícules tenen un gran impacte en múltiples camps científics principalment a causa d’i) la seva gran superfície específica i ii) la possibilitat d’ajustar l’estructura electrònica del material modificant la seva grandària i forma. Això és especialment rellevant en el camp de la catàlisi amb metalls de transició. Per a caracteritzar les propietats catalítiques de les nanopartícules s’han desenvolupat diverses tècniques experimentals i computacionals. No obstant això, la majoria dels esforços computacionals dedicats a comprendre l’activitat catalítica de les nanopartícules empren superfícies esteses per a representar el material. De fet, fins on sabem, hi ha pocs exemples de reaccions catalitzades per nanopartícules d’òxid metàl·lic utilitzant models de nanopartícules. Això limita l’exploració de llocs particulars sol presents en les superfícies de les nanopartícules i, per tant, és desitjable l’ús de models més realistes. Un dels colls d’ampolla en l’ús de models de nanopartícules realistes és el fet que la construcció del model no és senzilla, particularment per a materials multicomponent com els òxids de metalls de transició.
Aquesta tesi té dues parts principals. En primer lloc, desenvolupem una eina computacional capaç de construir models de nanopartícules per a compostos multicomponent amb estequiometria controlada i terminació de superfície de manera automatitzada, la qual cosa elimina la subjectivitat i el biaix humà. En segon lloc, utilitzem models de *slabs i nanopartícules per a avaluar els factors clau que determinen l’adsorció d’aigua i el rendiment catalític de *IrO2 per a la reacció d’evolució d’oxigen (*OER) mitjançant l’ús de simulacions DFT. El rendiment OER catalitzat per IrO2 s’ha explorat a través dels mecanismes d’atac nucleofílico d’aigua (WNA) i de oxoacoblament (I2M) tant per a superfícies com per a models de nanopartícules.
Hem trobat que la dissociació de l’aigua està controlada per les propietats intrínseques del material com l’acidesa de l’Anar, la basicitat Obr, la naturalesa del lloc vacant i els efectes cooperatius entre les molècules d’aigua adsorbidas. Respecte al mecanisme de la OER, els nostres resultats suggereixen que tant el mecanisme WNA com l’I2M requereixen intermediaris radicals per a ser factibles. A més, el mecanisme WNA sembla ser el més favorable per a gairebé tots els llocs estudiats en superfícies i nanopartícules. De fet, el mecanisme I2M només sembla ser el preferit en la superfície (011), on el caràcter oxil dels àtoms d’O en la superfície és major i la distància interatómica entre els grups oxil és bastant curta. A més, i de manera bastant notable, el lloc de la punta de la nanopartícula exhibeix un sobrepotencial lleugerament més gran que l’ideal, la qual cosa suggereix que els llocs tetracoordinats han d’explorar-se per a millorar el rendiment catalític del IrO2 per a la OER.Las nanopartículas tienen un gran impacto en múltiples campos científicos principalmente debido a i) su gran superficie específica y ii) la posibilidad de ajustar la estructura electrónica del material modificando su tamaño y forma. Esto es especialmente relevante en el campo de la catálisis con metales de transición. Para caracterizar las propiedades catalíticas de las nanopartículas se han desarrollado varias técnicas experimentales y computacionales. Sin embargo, la mayoría de los esfuerzos computacionales dedicados a comprender la actividad catalítica de las nanopartículas emplean superficies extendidas para representar el material. De hecho, hasta donde sabemos, hay pocos ejemplos de reacciones catalizadas por nanopartículas de óxido metálico utilizando modelos de nanopartículas. Esto limita la exploración de sitios particulares solo presentes en las superficies de las nanopartículas y, por lo tanto, es deseable el uso de modelos más realistas. Uno de los cuellos de botella en el uso de modelos de nanopartículas realistas es el hecho que la construcción del modelo no es sencilla, particularmente para materiales multicomponente como los óxidos de metales de transición. Esta tesis tiene dos partes principales. En primer lugar, desarrollamos una herramienta computacional capaz de construir modelos de nanopartículas para compuestos multicomponente con estequiometría controlada y terminación de superficie de manera automatizada, lo que elimina la subjetividad y el sesgo humano. En segundo lugar, utilizamos modelos de slabs y nanopartículas para evaluar los factores clave que determinan la adsorción de agua y el rendimiento catalítico de IrO2 para la reacción de evolución de oxígeno (OER) mediante el uso de simulaciones DFT. El rendimiento OER catalizado por IrO2 se ha explorado a través de los mecanismos de ataque nucleofílico de agua (WNA) y de oxoacoplamiento (I2M) tanto para superficies como para modelos de nanopartículas. Hemos encontrado que la disociación del agua está controlada por las propiedades intrínsecas del material como la acidez del Ir, la basicidad Obr, la naturaleza del sitio vacante y los efectos cooperativos entre las moléculas de agua adsorbidas. Con respecto al mecanismo de la OER, nuestros resultados sugieren que tanto el mecanismo WNA como el I2M requieren intermediarios radicales para ser factibles. Además, el mecanismo WNA parece ser el más favorable para casi todos los sitios estudiados en superficies y nanopartículas. De hecho, el mecanismo I2M solo parece ser el preferido en la superficie (011), donde el carácter oxil de los átomos de O en la superficie es mayor y la distancia interatómica entre los grupos oxil es bastante corta. Además, y de manera bastante notable, el sitio de la punta de la nanopartícula exhibe un sobrepotencial solo un poco más grande que el ideal, lo que sugiere que los sitios tetracoordinados deben explorarse para mejorar el rendimiento catalítico de IrO2 para la OER.
Nanoparticles have a large impact in multiple scientific fields mainly due to i) their large specific surface area and ii) the possibility of tuning the electronic structure of the material by modifying its size and shape. This has been particularly relevant in the field of catalysis with precious transition metals. To characterize the nanoparticle catalytic properties several experimental and computational techniques have been developed. Most of the computational efforts devoted to understand the catalytic activity of nanoparticles, however, employ extended surfaces to represent the material. Indeed, to the best of our knowledge, few examples of reactions catalyzed by metal oxide nanoparticles have been studied by using nanoparticles models. This limits the exploration of particular sites only present in the nanoparticle surfaces and thus, the use of more realistic models is desirable. One of the bottlenecks in the use of realistic nanoparticle models is the fact that model construction is not straightforward, particularly for multicomponent materials such as transition metal oxides. This thesis has two main parts. Firstly, we develop a computational tool able to construct nanoparticle models for multicomponent compounds with controlled stoichiometry and surface termination in an automatized manner, which removes human subjectivity and bias. Secondly, we use slab and nanoparticle models to evaluate the key factors that determine the water adsorption and the catalytic performance of IrO2 for the oxygen evolution reaction (OER) by using DFT simulations. The OER performance of IrO2 has been explored through the water nucleophilic attack (WNA) and oxo-coupling (I2M) mechanisms for both surfaces and nanoparticle models. We have found that the water dissociation is controlled by the intrinsic material properties like the Ir acidity, the Obr basicity, the nature of the vacant site and the cooperative effects between adsorbed water molecules. Concerning the OER mechanism, our results suggest that both the WNA and the I2M mechanisms require radical intermediates to be feasible. Moreover, the WNA mechanism seems to be the most favorable for almost all studied sites on surfaces and nanoparticles. Indeed, the I2M mechanism only seems to be the preferred one on the (011) surface, were the oxyl character of O atoms on the surface is larger and the interatomic distance between the oxyl groups is rather short. Furthermore, and quite remarkably, the tip site of the nanoparticle exhibits an OER potential that is only slightly larger than the ideal one, thereby suggesting that tetracoordinated sites should be explored to improve the catalytic performance of IrO2 for the OER.
Universitat Autònoma de Barcelona. Programa de Doctorat en Química
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ARELLANO, MERYELEM TANIA CHURAMPI. "TREATMENT OF EFFLUENTS CONTAINING CYANIDE BY SINGLET OXYGEN GENERATED BY THE REACTION OF HYDROGEN PEROXIDE AND SODIUM HYPOCHLORITE." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2012. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=21883@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROCOORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
PROGRAMA DE SUPORTE À PÓS-GRADUAÇÃO DE INSTS. DE ENSINO
O presente trabalho teve como objetivo estudar a viabilidade da aplicação do processo oxidativo avançado que utiliza oxigênio singlete, gerado quimicamente por peróxido de hidrogênio e hipoclorito de sódio, para oxidar o cianeto livre. O processo foi estudado em batelada, simulando uma solução sintética de KCN com características de pH e concentração similares às condições típicas de um efluente real. A combinação aquosa do H2O2 e NaClO para gerar oxigênio singlete, foi eficaz para oxidar o cianeto, em uma faixa de pH 9 a 11. Com concentrações iniciais de cianeto de 10, 100, 500 e 1000 mg/L, e proporção molar de [H2O2maisNaClO]:[CN-]igual a 2:1, foi possível atingir uma concentração final de cianeto menor do que 0,2 mg/L, com 98,9 por cento e 99 por cento de remoção, a pH 11 e 9, em apenas 2 e 20 minutos, respectivamente. Quando o cianeto foi oxidado por H2O2 e NaClO separadamente, para as mesmas condições experimentais, o peróxido de hidrogênio apenas oxidou o cianeto em 30 por cento e 26 por cento, a pH 9 e 11, respectivamente, em 60 minutos de reação. Quando o cianeto foi oxidado com NaClO, o cianeto atingiu uma concentração final menor do que 0,2 mg/L, com uma remoção de 98 por cento e 99 por cento, a pH 9 e 11, em 60 e 5 minutos de reação, respectivamente.
The synergistic combination of hydrogen peroxide and hypochlorite ion in water results in formation of the highly oxidizing intermediate species singlet oxygen (1O2), which is effective in the oxidation of free cyanide (CN-) in water. The process was fast and efficient over the studied pH range of 9-11, and up to an initial CN- concentration of 1000 mg/L. For an initial [CN-] equal 100 mg/L, pH equal 9, and molar ratio ([H2O2]more[NaClO])/[CN-] equal 1:1 it was possible to achieve a final concentration of [CN-] lower than 0.2 mg/L (99.8 per cent reduction) in t equal 20 min at 25 degrees celsius in a batch reaction. By comparison, the same reaction with either of the separate oxidants (H2O2 or NaClO) at the same molar ratio of oxidant/CN- equal 1:1 resulted in a maximum of 87 per cent breakdown of the cyanide (using NaClO) for the same 20 min reaction period.
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Groche, Florian J. [Verfasser]. "Chemical Oxygen Generation From Peroxo-Compounds For Aviation Purposes - From Basic Chemistry To Prototype Design / Florian J. Groche." München : Verlag Dr. Hut, 2017. http://d-nb.info/1155057295/34.
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Miljevic, Branka. "The application of a profluorescent nitroxide probe to detect reactive oxygen species derived from combustion-generated particulate matter." Thesis, Queensland University of Technology, 2010. https://eprints.qut.edu.au/39344/1/Branka_Miljevic_Thesis.pdf.
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Particulate pollution has been widely recognised as an important risk factor to human health. In addition to increases in respiratory and cardiovascular morbidity associated with exposure to particulate matter (PM), WHO estimates that urban PM causes 0.8 million premature deaths globally and that 1.5 million people die prematurely from exposure to indoor smoke generated from the combustion of solid fuels. Despite the availability of a huge body of research, the underlying toxicological mechanisms by which particles induce adverse health effects are not yet entirely understood. Oxidative stress caused by generation of free radicals and related reactive oxygen species (ROS) at the sites of deposition has been proposed as a mechanism for many of the adverse health outcomes associated with exposure to PM. In addition to particle-induced generation of ROS in lung tissue cells, several recent studies have shown that particles may also contain ROS. As such, they present a direct cause of oxidative stress and related adverse health effects.
Cellular responses to oxidative stress have been widely investigated using various cell exposure assays. However, for a rapid screening of the oxidative potential of PM, less time-consuming and less expensive, cell-free assays are needed. The main aim of this research project was to investigate the application of a novel profluorescent nitroxide probe, synthesised at QUT, as a rapid screening assay in assessing the oxidative potential of PM. Considering that this was the first time that a profluorescent nitroxide probe was applied in investigating the oxidative stress potential of PM, the proof of concept regarding the detection of PM–derived ROS by using such probes needed to be demonstrated and a sampling methodology needed to be developed. Sampling through an impinger containing profluorescent nitroxide solution was chosen as a means of particle collection as it allowed particles to react with the profluorescent nitroxide probe during sampling, avoiding in that way any possible chemical changes resulting from delays between the sampling and the analysis of the PM. Among several profluorescent nitroxide probes available at QUT, bis(phenylethynyl)anthracene-nitroxide (BPEAnit) was found to be the most suitable probe, mainly due to relatively long excitation and emission wavelengths (λex= 430 nm; λem= 485 and 513 nm). These wavelengths are long enough to avoid overlap with the background fluorescence coming from light absorbing compounds which may be present in PM (e.g. polycyclic aromatic hydrocarbons and their derivatives). Given that combustion, in general, is one of the major sources of ambient PM, this project aimed at getting an insight into the oxidative stress potential of combustion-generated PM, namely cigarette smoke, diesel exhaust and wood smoke PM.
During the course of this research project, it was demonstrated that the BPEAnit probe based assay is sufficiently sensitive and robust enough to be applied as a rapid screening test for PM-derived ROS detection. Considering that for all three aerosol sources (i.e. cigarette smoke, diesel exhaust and wood smoke) the same assay was applied, the results presented in this thesis allow direct comparison of the oxidative potential measured for all three sources of PM. In summary, it was found that there was a substantial difference between the amounts of ROS per unit of PM mass (ROS concentration) for particles emitted by different combustion sources. For example, particles from cigarette smoke were found to have up to 80 times less ROS per unit of mass than particles produced during logwood combustion. For both diesel and wood combustion it has been demonstrated that the type of fuel significantly affects the oxidative potential of the particles emitted. Similarly, the operating conditions of the combustion source were also found to affect the oxidative potential of particulate emissions. Moreover, this project has demonstrated a strong link between semivolatile (i.e. organic) species and ROS and therefore, clearly highlights the importance of semivolatile species in particle-induced toxicity.
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Cheng, Yubo. "Reactive oxygen species generation and gene expression linked to sources of atmospheric fine particulate matter (PM₂.₅) in Hong Kong." HKBU Institutional Repository, 2019. https://repository.hkbu.edu.hk/etd_oa/662.
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Fine particulate matter (PM2.5) is the leading public health risk factor of global disease burden, which has caused 4.2 million deaths in 2015. This thesis aims to improve the scientific understanding on the sources and health impacts of PM2.5 in Hong Kong. Various chemical and biological analytical techniques were applied to characterize the chemical and toxicological properties of PM2.5 samples collected in Hong Kong during 2011-2012. Positive matrix factorization (PMF), together with the quantified chemical markers and water-soluble PM2.5-induced reactive oxygen species (ROS) activity as the input matrix, was performed to apportion the source-specific contributions to ambient organic carbon (OC) and the oxidative potential of water-soluble PM2.5. Zebrafish was applied as in-vivo model to evaluate the PM2.5-induced differential expression genes (DEGs). An L2-normaliztion integrated PMF was developed and applied to quantitatively assess the ability of PM2.5 to induced DEGs in relation to various sources and chemical compositions of PM2.5. The main findings are summarized below: (1) Thirty nine primary organic aerosol (POA) and secondary organic aerosol (SOA) markers of various anthropogenic (i.e. biomass burning (BB)) and biogenic sources (i.e. isoprene, monoterpenes and β-caryophyllene) were identified and quantified. High levels of OC and SOA markers were observed on regional pollution days than long regional transport (LRT) pollution and local emissions days. A kinetic model (Kintecus) was applied to explore the major formation channels of isoprene SOA, and it was found that isoprene SOA was mainly formed through the ring-opening reaction of isoprene epoxydiols (IEPOX) in Hong Kong. (2) PMF analysis, together with the chemical markers measured in Chapter 1 &2, was performed to evaluate the sources of OA in Hong Kong. Sea salt, marine vessels, vehicle emissions, BB/SOA, SOA, and secondary sulfate (SS) were apportioned as the major sources of ambient OC in Hong Kong. Secondary formation, including SOA, BB aging and SS sources, was found to be the major contributor to OC (~51%) throughout the whole year. BB was the major anthropogenic contributor to OC on regional days (28.8%); while marine vessel was the dominated primary source of OC on local days (33.2%). SOC concentrations were estimated using a tracer-based method (SOCTBM) and PMF (SOCPMF). Both SOCTBM and SOCPMF showed highest concentrations on regional days (SOCTBM: 0.74 µg m-3; SOCPMF: 3.27 µg m-3). Among all SOA precursors, monoterpenes had the most abundant contribution (40.9%) to SOCTMB during the whole year. Moreover, sulfate has significant impacts on SS-related SOC and SOA from monoterpenes and naphthalene. Particle acidity (HP+) showed correlation with SOC from BB aging. These results provide us a quantitative understanding on the SOA origins in the region, which lays a foundation for the source apportionment of PM2.5-induced toxicity in the following chapters. (3)Cell-free dithiothreitol (DTT) and ·OH generation assays were applied to measure the ROS activity induced by water-soluble PM2.5 collected in Hong Kong during 2011-2012. Different levels of ROS activity were observed for different chemical fractions of PM2.5 and PM2.5 from various sources. Six factors, i.e. SS, BB, SOA, vehicle emissions, marine vessels and metal factors were apportioned by PMF as the major sources of water-soluble PM2.5 induced ROS potential. Metal factors was found to be the major contributor to both DTT activity (39.1%) and ·OH generation ability (84.5%) throughout the year, especially on LRT (DTT: 54.8%; ·OH generation: 91.1%) and regional days (DTT: 53.9%; ·OH generation: 87.7%). On local days, contribution of marine vessels to DTT oxidation become more significant (48.7%), however its contribution to ·OH generation is negligible. Metal factors is by far the most significant contributor to ·OH generation, even on local days (73.1%). It is interesting to note that all six PMF-resolved sources are associated with DTT oxidation, however only three sources (i.e. metal factor, vehicle emissions and SOA) showed contributions to ·OH generation. Moreover, among these six sources, marine vessels exhibited the highest intrinsic DTT ability; while metal factor was the most effective source in ·OH generation. (4) Zebrafish embryo (AB strain) was applied as the in-vivo model to assess PM2.5 toxicity in Hong Kong through genome-wide gene transcriptional analysis. The results showed that embryonic exposure to PM2.5 could induce remarkable changes in gene expression patterns in zebrafish. DEGs between PM2.5 extract treated and untreated zebrafish embryo samples were identified, and they were found mainly associated with responses to xenobiotic stimulus, and muscle and heart development and functions. The correlation analysis between co-expressed gene modules and chemical species of PM2.5 implied the different chemical compositions and sources of PM2.5 have significant influences on the PM2.5-induced biological responses. (5) An L2-normalizaiton integrated PMF was developed to analyze the high throughput biological and chemical data simultaneously, which quantitatively evaluated the ability of PM2.5 to induce DEGs in relation to sources and compositions. In this chapter, nine sources associated with PM2.5-induced DEGs were well apportioned, i.e. fresh sea salt, aged sea salt, SS, SOA, BB, coal combustion, vehicle emissions, marine vessels and metal factors. Among these sources, metal factors (annual mean: 26.5%, range: 17.6-39.3%) and vehicle emissions (annual mean: 16.3%, range: 0.0-25.3%) are the two leading contributors to PM2.5-induced DEGs levels. PM2.5 from combustion related sources (e.g. vehicle emissions, metal factors, BB) and sea salt exhibited stronger ability to induce DEGs than those from secondary sources. Although secondary formation (including SOA and SS) has a significant contribution to ambient PM2.5 (12 μg m-3, 40%), its capacity of DEGs induction is quite low. Moreover, several biological functions and pathways influenced by PM2.5 from various sources have also been well evaluated. In this study, large scales of biological and chemical data were analyzed for the first time by a L2-normalizaiton integrated PMF to apportion the PM2.5-induced DEGs, and this thesis work firstly reported the major sources of water-soluble PM2.5-induced ROS in Hong Kong. Results from this study provide a scientific basis for the prediction of PM2.5-associated adverse health outcomes and can help the policy makers to formulate cost-effective and targeted PM2.5 mitigation strategies to protect public health.;Fine particulate matter (PM2.5) is the leading public health risk factor of global disease burden, which has caused 4.2 million deaths in 2015. This thesis aims to improve the scientific understanding on the sources and health impacts of PM2.5 in Hong Kong. Various chemical and biological analytical techniques were applied to characterize the chemical and toxicological properties of PM2.5 samples collected in Hong Kong during 2011-2012. Positive matrix factorization (PMF), together with the quantified chemical markers and water-soluble PM2.5-induced reactive oxygen species (ROS) activity as the input matrix, was performed to apportion the source-specific contributions to ambient organic carbon (OC) and the oxidative potential of water-soluble PM2.5. Zebrafish was applied as in-vivo model to evaluate the PM2.5-induced differential expression genes (DEGs). An L2-normaliztion integrated PMF was developed and applied to quantitatively assess the ability of PM2.5 to induced DEGs in relation to various sources and chemical compositions of PM2.5. The main findings are summarized below: (1) Thirty nine primary organic aerosol (POA) and secondary organic aerosol (SOA) markers of various anthropogenic (i.e. biomass burning (BB)) and biogenic sources (i.e. isoprene, monoterpenes and β-caryophyllene) were identified and quantified. High levels of OC and SOA markers were observed on regional pollution days than long regional transport (LRT) pollution and local emissions days. A kinetic model (Kintecus) was applied to explore the major formation channels of isoprene SOA, and it was found that isoprene SOA was mainly formed through the ring-opening reaction of isoprene epoxydiols (IEPOX) in Hong Kong.
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Pond, Bethany Leigh. "Effects of flow on reactive oxygen species production in brain versus aortic endothelial cells| The source of ROS generation." Thesis, State University of New York at Buffalo, 2015. http://pqdtopen.proquest.com/#viewpdf?dispub=1600812.
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Endothelial cells are a vital region in the pathophysiology of the vasculature because it is the interface between blood flow and the vessel. One way that the structure of the vessels wall can change is by the accumulation of reactive oxygen species (ROS), which has been correlated to aneurysm formation. Four main ROS sources in endothelial cells are: NADPH oxidase, mitochondria electron transport chain, eNOS uncoupling, and xanthine oxidase. Endothelial cells are an essential component of vasculature that has distinct functions and morphology. The aorta and brain arteries are highly populated by endothelial cells but the morphology and cellular signaling has been shown to be different. This study focuses on the difference between brain and aorta ROS production and how flow affects ROS. Joeseph Moran-Guiati and Jason Kushner provided the brain and aortic endothelial cultures for these studies. NADPH oxidase complex is the main contributor in both cell types but more in brain. Surprisingly, both cell types contain approximately the same number of NOX subunits, suggesting that the difference in ROS production is dependent on how activated these subunits are. Mitochondrial ROS was only significantly generated in brain cells and is verified because brain endothelium contains higher numbers of mitochondria. Both uncoupling of eNOS and xanthine oxidase did not contribute to ROS generation in static cultures. ROS production increased even further in both cell types when cells were exposed to flow and even higher in brain, suggesting that flow effects ROS generation. These results provide useful information in the difference between ROS generation and how it can be harmful in possibly causing intracranial aneurysm formation.
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Sommani, Piyanart. "Study on the modulation of reactive oxygen species generation in cellular systems and its effects on some biologically significant events." Kyoto University, 2007. http://hdl.handle.net/2433/135575.
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Kyoto University (京都大学)0048
新制・課程博士
博士(エネルギー科学)
甲第13404号
エネ博第161号
新制||エネ||38(附属図書館)
UT51-2007-Q805
京都大学大学院エネルギー科学研究科エネルギー社会・環境科学専攻
(主査)教授 牧野 圭祐, 教授 吉川 暹, 准教授 小瀧 努
学位規則第4条第1項該当
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Mai, Trang. "FUNCTIONALIZATION OF IRON OXIDE NANOPARTICLES AND THE IMPACT ON SURFACE REACTIVE OXYGEN SPECIES GENERATION FOR POTENTIAL BIOMEDICAL AND ENVIRONMENTAL APPLICATIONS." UKnowledge, 2019. https://uknowledge.uky.edu/cme_etds/102.
Full textAbstract:
Iron oxide nanoparticles (IONPs) have been widely studied for a variety of applications, from biomedical applications (e.g., cell separation, drug delivery, contrast agent for magnetic resonance imaging and magnetically mediated energy delivery for cancer treatment) to environmental remediations (e.g., heavy metal removal and organic pollutants degradation). It has been demonstrated that IONPs can induce the production of reactive oxygen species (ROS) via Fenton/Haber-Weiss reactions which has been shown to be one of the key underlying mechanisms of nanoparticles toxicity. This inherent toxicity of nanoparticles has been shown to enhance the efficacy of traditional cancer therapies such as chemotherapy and radiation. In addition, the generation of ROS induced by IONPs has been also studied as advanced oxidation processes (AOP) for wastewater treatment. Recent research has also shown that exposure to an alternating magnetic field can significantly enhance the generation of ROS induced by IONPs. Moreover, the coatings of IONPs play an important role on the surface reactivity of nanoparticles since it can prevent the generation of ROS via Fenton chemistries at the surface of the nanoparticles.
In this work, co-precipitated IONPs were functionalized with small molecules including citric acid, sodium phosphate, amino silane and dopamine. The impact of coating on surface reactivity of the as-synthesized particles was studied using methylene blue dye degradation assay under AMF exposure. With the coatings of these small molecules, the IONPs induced ROS generation was significantly decreased because of the dense surface coverage. To study the effect of polymeric coatings, a degradable poly (beta amino ester) (PBAE) polymer coating was synthesized with dopamine as an anchor to bind to nanoparticles. The surface reactivity of the particles was expected to be recovered once the polymer coating was degraded. Furthermore, the impact of non-degradable PEG-based polymer coating on surface reactivity via ROS generation was also investigated using methylene blue decolorization assay with the presence of AMF. The retention of surface reactivity of PEG-based polymer coated IONPs shows promise for cancer treatment.
The application of IONPs as heterogeneous catalyst for organic contaminant degradation was investigated. Bisphenol A (BPA) was used as a model compound, and Fenton reactions were induced by IONPs with the presence of hydrogen peroxide and hydroxylamine as well as alternating magnetic field exposure. The kinetics of BPA degradation under water bath and AMF exposure at 37oC was also studied, and the results showed potential applications of IONPs for organic pollutants remediation.
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Tsang, Shui Ying. "The role of copper and copper-ligand interactions in the generation of reactive oxygen species and the promotion of biomolecular damage." Thesis, University of Aberdeen, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.319216.
Full textAbstract:
The work described in this thesis investigates the mechanisms by which copper complexes catalyse the generation of reactive oxygen species (ROS), including the highly reactive hydroxyl radical (.OH), and induce oxidative damage to DNA. An ESR study into the copper-Fenton reaction revealed that, in the presence of buffers and other copper chelators, .OH is generated. In contrast, it is suggested that a Cu(III) species may be formed in the reaction of aqueous, unchelated copper ions. The generation of .OH in the copper-Fenton reaction, under biomimetic conditions, was confirmed by analysis of the products formed following the incubation of DNA components with this system. Preferential binding of Cu(II) to guanosine over the other nucleosides was determined and copper redox cycling at GC sites was found to be more facile than at AT sites. Stability constants for the copper complexes with several other biochemically important ligands such as glutathione (GSH), Quin2 and 1,10-phenanthroline (OP) were also measured. The ease of redox cycling for the copper complexes was found to be of the order: OP ~ Quin2 > GSH. However, OP enhanced both the copper-Fenton reaction and copper-induced DNA damage while both GSH and Quin2 were inhibitory. Gel chromatography studies suggested that ternary complex formation occurs between Cu(I)-DNA and both Quin2 and OP. This implies that the ternary complex with OP is more redox active than that with Quin2. Whilst cysteine enhanced copper-mediated DNA damage at early incubation times, it was more protective than GSH and homocysteine at later stages. The effects at early incubation times are attributed to the ease of copper redox cycling in the presence of thiols while the effects over prolonged incubations reflect Cu(II) stabilisation by the respective disulphides or similar products.
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Kominato, Rieko. "Src activation generates reactive oxygen species and impairs metabolism-secretion coupling in diabetic Goto-Kakizaki and ouabain-treated rat pancreatic islets." Kyoto University, 2008. http://hdl.handle.net/2433/124247.
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