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1
Buckley, C. "Transient free radicals and triplets in solution." Thesis, University of Oxford, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.233411.
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Ritchie, A. J. D. "Chemically induced dynamic electron polarisation of transient free radicals in solution." Thesis, University of Oxford, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.354864.
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Simpson, Nigel J. K. "Studies of transient free radicals in solution by flash photolysis E.S.R." Thesis, University of Oxford, 1990. http://ora.ox.ac.uk/objects/uuid:dd9a8aa9-f68a-4362-af7e-6c052fa3a5fe.
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An introduction is presented to the nature of polarized and non-polarized transient spin resonance signals, produced by flash-photolysis e.s.r., followed by a description of the equipment used for experimental work. Theories of Chemically Induced Dynamic Electron Spin Polarization are reviewed and various models introduced to illustrate these concepts. A description is given of the first thorough investigation into the effect of CIDEP polarization transfer down a free radical chain and expands upon the consequences of hyperfine-dependent relaxation and the relative signs of coupling constants in various radical species. It concludes with an account of two methods of kinetic analysis which are the first practical demonstrations of their kind, and employ extension of expressions developed in earlier chapters. Studies are made of the CIDEP behaviour of radicals in high viscosity paraffins. A reassessment of previous published work is made: anomalous polarization behaviour was found to have been over-compensated for. A new method of extracting values for T1 and T2,/sub> is demonstrated for strong transient e.s.r. signals. A collection of experimental data relating to the previously unexplained absorptive polarization observed in the spectrum of ketyl radicals and the longer-time phase inversion of hyperfine-dependent CIDEP is given. The operation of Triplet Mechanism CIDEP in the ketyl radical systems is ruled out and a division of radicals into geminately formed and free-encounter pairs is shown to be incapable of explaining the observed phase changes. In its place a cross-relaxational mechanism, drawing upon simultaneously generated nuclear spin polarization is advanced. Conclusions are drawn that this may account for both anomalies. Lastly a photochemical application of CIDEP is demonstrated; two different reaction intermediates are identified upon photolysis of ortho phthalaldehyde, depending upon the quenching conditions. A reaction scheme consistent with all experimental data is proposed. A brief comment upon the photo-chemistry of indan 2-one concludes this work.
4
Grant, A. I. "Electron spin resonance studies of transient species." Thesis, University of Oxford, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.354833.
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MacFaul, Philip. "Free radical generation by photolysis of iron(III) porphyrin carboxylate complexes in aqueous solution." Thesis, University of York, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.241076.
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Osborne, Victoria A. "The photodecomposition of carboxylate complexes of ionic iron (III) porphyrins in solution." Thesis, University of York, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.313870.
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Yeung, May T. "Free radical studies in solution." Thesis, University of Oxford, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.306870.
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Saadalla-Nazhat, R. A. S. "Reactions of radiation-produced free radicals with copper-amino acid complexes and related compounds in aqueous solution." Thesis, University of Newcastle Upon Tyne, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.378870.
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Myint, Pe. "Free radical reactions of hyaluronic acid in aqueous solution." Thesis, University of Salford, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.292943.
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Cai, Yudong. "Synthetic and mechanistic aspects of free-radical reactions in solution." Thesis, University College London (University of London), 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.322240.
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Milne, E. C. "An E.S.R. investigation of free-radical polymerization in aqueous solution." Thesis, University of York, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.304358.
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12
Gao, Jun. "Advances in mathematical modelling of multicomponent free-radical polymerizations in bulk, solution and emulsion." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0004/NQ44761.pdf.
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Laplante, Marc. "A Java(TM)-based model for multi-component free-radical bulk and solution polymerizations." Thesis, University of Ottawa (Canada), 2004. http://hdl.handle.net/10393/26686.
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Modelling and simulation play an essential role in developing, optimizing and understanding the steps involved in the production of polymers. A simulator was designed in order to model free-radical bulk and solution homopolymerizations, as well as multi-component polymerizations. Several optional models were incorporated in to the simulator, such as several glass transition temperature models, and the penultimate model. Java(TM) was selected as the programming language because of its object-oriented nature, providing high flexibility and ensuring easy extension of the code. Once the simulator was validated against experimental data and another simulator, it was used to model three systems: butyl acrylate/vinyl acetate (BA/VAc), styrene/butyl acrylate (Sty/BA), and butyl acrylate/methyl methacrylate/vinyl acetate (BA/MMA/VAc). (Abstract shortened by UMI.)
14
Lewis, Scott Romak. "SOLUTION PHASE AND MEMBRANE IMMOBILIZED IRON-BASED FREE RADICAL REACTIONS: FUNDAMENTALS AND APPLICATIONS FOR WATER TREATMENT." UKnowledge, 2011. http://uknowledge.uky.edu/gradschool_diss/170.
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Membrane-based separation processes have been used extensively for drinking water purification, wastewater treatment, and numerous other applications. Reactive membranes synthesized through functionalization of the membrane pores offer enhanced reactivity due to increased surface area at the polymer-solution interface and low diffusion limitations. Oxidative techniques utilizing free radicals have proven effective for both the destruction of toxic organics and non-environmental applications. Most previous work focuses on reactions in the homogeneous phase; however, the immobilization of reactants in membrane pores offers several advantages. The use of polyanions immobilized in a membrane or chelates in solution prevents ferric hydroxide precipitation at near-neutral pH, a common limitation of iron(Fe(II/III))-catalyzed hydrogen peroxide (H2O2) decomposition. The objectives of this research are to develop a membrane-based platform for the generation of free radicals, degrade toxic organic compounds using this and similar solution-based reactions, degrade toxic organic compounds in droplet form, quantify hydroxyl radical production in these reactions, and develop kinetic models for both processes.
In this study, a functionalized membrane containing poly(acrylic acid) (PAA) was used to immobilize iron ions and conduct free radical reactions by permeating H2O2 through the membrane. The membrane’s responsive behavior to pH and divalent cations was investigated and modeled. The conversion of Fe(II) to Fe(III) in the membrane and its effect on the decomposition of hydrogen peroxide were monitored and used to develop kinetic models for predicting H2O2 decomposition in these systems. The rate of hydroxyl radical production, and hence contaminant degradation can be varied by changing the residence time, H2O2 concentration, and/or iron loading. Using these membrane-immobilized systems, successful removal of toxic organic compounds, such as pentachlorophenol (PCP), from water was demonstrated.
Another toxic organic compound of interest for water treatment applications is trichloroethylene (TCE). Due to its limited solubility in water, a majority of the TCE is often present in the form of droplets. In this study, effective TCE droplet degradation using chelate-modified, iron-catalyzed free radical reactions at near-neutral pH was demonstrated. In order to predict the degradation of aqueous and non-aqueous phase TCE for these reactions, a mathematical model was constructed through the use of droplet mass transfer correlations and free radical reaction kinetics.
15
VIGOUROUX, CECILE. "Microdynamique des solutions : influence des espèces paramagnétiques sur la relaxation en RMN." Université Joseph Fourier (Grenoble), 1998. http://www.theses.fr/1998GRE10068.
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Ce travail concerne l'etude de differents systemes modeles en solution, representant les interactions inter- ou intramoleculaires. L'agent de perturbation est une espece paramagnetique. Nous utilisons le tempol (radical nitroxyde neutre), l'anion nitrosodisulfonate (radical nitroxyde charge) ou des cations lanthanide trivalents. La methode consiste a mesurer des taux de relaxation spin-reseau et des coefficients de diffusion translationnelle par resonance magnetique nucleaire, puis a elaborer un modele theorique ou les valeurs calculees sont les plus proches possibles des valeurs experimentales. Les resultats obtenus montrent la particularite du chloroforme (formation d'agregats entre molecules de chloroforme et de solute). Nous montrons egalement que le fluor est difficilement utilisable comme sonde de distance intramoleculaire pour nos systemes (sucre doublement marque par un radical tempol et un noyau #1#9f). Nous avons pu mettre en evidence par la mesure experimentale la formation d'associations entre un ion cs#+ et une molecule de tempol par un modele simultane de dynamique translationnelle et rotationnelle. Les resultats sur les cations lanthanides trivalents en presence de cations tetramethylammonium montrent que les modeles de mouvements relatifs d'ions spheriques sont parfaitement adaptes a ces systemes. Nous obtenons une adequation moins bonne en remplacant un radical neutre (tempol) par un radical charge (anion nitrosodisulfonate) en presence d'un autre anion (methanesulfonate). Nous pouvons alors etudier les proprietes electroniques des cations lanthanides. Nous montrons experimentalement la substitution des molecules d'eau par l'anion nitrate complexant dans le cas du gd#3#+. Nous estimons les parametres de champ cristallin des cations lanthanides hydrates par des mesures de deplacements paramagnetiques.
16
MAGALHAES, WELINGTON F. "Influence de parametres physico-chimiques sur les reactions du positonium en solution." Université Louis Pasteur (Strasbourg) (1971-2008), 1987. http://www.theses.fr/1987STR13218.
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17
Critchley, Andrew Duncan James. "Structure of free radicals." Thesis, University of Newcastle Upon Tyne, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.327188.
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18
梁韻詩 and Wan-sze Leung. "High resolution spectroscopy of free radicals." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1998. http://hub.hku.hk/bib/B31237319.
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Towle, Jonathan Peter. "The LMR spectra of free radicals." Thesis, University of Oxford, 1992. http://ora.ox.ac.uk/objects/uuid:7ac8e9e4-33e8-428b-962d-943bf07d5f94.
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Laser Magnetic Resonance (LMR) is a very sensitive, accurate and high resolution spectroscopic technique. Transitions of paramagnetic species are brought into coincidence with a fixed frequency laser using Zeeman tuning. Three different LMR spectrometers are described, two of which use the CO laser as a radiation source and the other used optically pumped far-infrared lasers. These LMR spectrometers have been used to study four radicals, germanium hydride (GeH), tellurium deuteride (TeD), iron hydride (FeH) and iron deuteride (FeD). Transitions in the fundamental and first hot bands of the GeH radical have been detected by CO LMR. The transitions occur within both 2Π1andfrasl;2 and 2Π3andfrasl;2 manifolds. These data have been fitted with previously published data for GeH and GeD to determine the parameters of a single model effective Hamiltonian which describes all naturally occurring isotopomers. Details of the Hamiltonian are given. The same Hamiltonian was used to model transitions in the fundamental and first two hot bands of the TeD radical that were also recorded using CO LMR. Resonances from the seven most abundant isotopomers, including the two with I = ½, have been identified. Seven transitions in the fundamental band of FeH have been observed using Faraday CO LMR. Due to the complicated electronic structure for FeH it is not possible to model these data using a single model effective Hamiltonian. It has been possible to fit the parameters of a second order Zeeman expression to these FeH data and so determine accurate zerofield transition wavenumbers for six of these transitions. Pure rotational transitions in the ground state of FeD have been observed using FIR LMR. As for FeH the parameters of second order Zeeman expressions can be fitted to these transitions and zero field wavenumbers determined.
20
Leung, Wan-sze. "High resolution spectroscopy of free radicals /." Hong Kong : University of Hong Kong, 1998. http://sunzi.lib.hku.hk/hkuto/record.jsp?B19737610.
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21
Ayuko, Washington O. "Free radicals as potential antitumour agents." Thesis, Aston University, 1991. http://publications.aston.ac.uk/12521/.
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The aim of this work was to use extremely low concentrations of free radical generating compounds as a 'catalyst' to trigger endogenous free radical chain reactions in the host and to selectively eliminate neoplastic cells in the host. To test the hypothesis, a number of free radical generating compounds were screened on several malignant cell lines in vitro to select model compounds that were used against tumour models in vivo. 2,2-Diphenyl-1-picrylhydrazyl (DPPH) and its derivatives were selected at the model compounds for in vivo experiments in view of their high cytotoxic potency against several malignant cell lines in vitro. The water soluble derivative, 2,2-diphcnyl-l-(2', 4'-dinitro-6'-sulphophenyl) hydrazyl (DDSH) given by subcutaneous injections demonstrated significant antitumour activities against the MAC 16 murine colon adcnocarcinoma implanted subcuta-ncously in male NMRI mice at nanomolar concentration range. 40-60% of long term survival of over 60 days was achieved (compared with control survival of 20 days) with total tumour elimination. This compound was also active against both P388 leukaemia in male BDF1 mice and TLX5 lymphoid tumour in male CBA/CA mice at a similar concentration range. However, some of these animals died suddenly after treatment with no evidence of disease present at post mortem. The cause of death was unknown but thought to be related to the treatment. There was significant increase in scrum level of malondialdchydc (MDA) following treatment, but did not correlate to the antitumour activities of these compounds. Induction of supcroxide dismutasc (SOD), and glutathione peroxidase (GPx) occurred around day 8 after the administration of DDSH. Histological sections of MAC16 tumours showed areas of extensive massive hacmorrhagic necrosis and vascular collapse associated with perivas-cular cell death following the administration of nanomolar concentration of DDSH which was probably compatible with the effects of free radicals. It was concluded that the antitumour activities of these compounds may be related to free radical and cytokinc production.
22
Costello, Andrew. "The reactions of alkylperoxyl radicals in solution." Thesis, University of York, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.357012.
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Bharadwaj, Lalita Anne. "Oxygen free radicals, mediators of vascular tone." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq24005.pdf.
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Meads, Roger Francis. "Kinetics and photochemistry of transient free-radicals." Thesis, University of Canterbury. Chemistry, 1992. http://hdl.handle.net/10092/7756.
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We report here several experimental and theoretical studies of free-radicals in the gas phase. Bimolecular rate constants for the reactions
BH + NO → products k = 1.26 →!± 0.07 x 10^10 cm^3 s^-1
BH + C2H4 → products k = 1.41 →!± 0.09 x 10^10 cm^3 s^-1
CN + NH3 → HCN + NH2 k = 3.0 →!± 0.4 x 10^11 cm^3 s^-1
CN + ND2 → DCN + ND2 k = 1.5 →!± 0.3 x 10^11 cm^3 s^-1
have been measured and upper limits to the rate constants for the reactions
BH + CO → products k < 1.1 x 10^11 cm^3 s^-1
BH + CH2H4 → products k < 1.6 x 10^12 cm^3 s^-1
BH + CxH6 → products k < 9.1 x 10^13 cm^3 s^-1
BH + O2 → products k < 1.3 x 10^13 cm^3 s^-1
have been set. BH (1 ) radicals were generated by excimer-laser photolysis of diborane at 193 nm and detected by time-resolved laser-induced fluorescence. The effects of varying the temperature and the nature of the buffer gas on the reactions of BH with NO and C2H4 have been investigated. CN (2 +) radicals were generated by excimer-laser photolysis of C2N2 at 193 nm and their time evolution was monitored by absorption spectroscopy.
In addition to the rate constant measurements, the products of the reactions of CN with NH3and ND3 have been determined using mass spectrometry and infrared absorption spectroscopy. The methods of ab initio molecular orbital theory have been used to determine structures and relative energies of species which could conceivably be involved in these reactions. The results of all studies have been interpreted in relation to the mechanisms of the reactions concerned.
Prompt emission observed during the 193 nm excimer-laser photolyses of diborane and stannane has been characterised and the identity of the probable emitting species for each band observed has been assigned on the basis of band structure, known thermochemistry and the dependence of band intensity on photolysis laser power. The results obtained have been interpreted in terms of the nature of the photodissociation processes.
25
Langford, Vaughan S. "Magnetooptical spectroscopy of matrix-isolated free radicals." Thesis, University of Canterbury. Chemistry, 1997. http://hdl.handle.net/10092/9269.
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This Ph.D. thesis presents the results of magnetooptical spectroscopic investigations of free radicals isolated in Ar matrices at cryogenic temperatures (≤20 K). The experiments required development of a high-resolution simultaneous magnetic circular dichroism (MCD) and absorption spectrometer, MOD4. Design, construction and commission of MOD4 comprised a significant portion of this project, and its description constitutes a substantial part of the 'Experimental' chapter of the thesis.
The results of matrix-isolation experiments on the first-row radical monohydrides, CH, NH (and ND) and OH (and OD), and the theoretical analyses of the data comprise the main body of this thesis, and are presented in three chapters. Temperature and magnetic-field dependencies of the MCD and absorption over the ranges T≈1.4 –17 K and B = 0 to ∼ 4.5 T, are interpreted in terms of a spin-orbit (SO) –crystal-field (CF) model. The data are analysed by the application of quantum-mechanical and group-theoretical techniques, utilising moment analysis and (in the case of NH) spectral simulation. These allow SO and CF parameters to be extracted. Assignments of structure observed in the spectra have also been attempted.
Radical monoanions and monocations of buckminsterfullerene (C₆₀) have been investigated in Ar matrices using MCD and absorption spectroscopy, over the ranges
T≈1.6 –30 K and B = 0 –4 T. Preliminary conclusions have been drawn from these data, concerning the symmetry of the molecules, but more experimental and theoretical work needs to be done.
Ferricenium, the radical cation of ferrocene, has been isolated in Ar (with a SF6 counter-ion) for the first time. Preliminary MCD and absorption data are presented, and show well-resolved vibronic structure; assignments to totally symmetric and Jahn-Teller-active vibrational overtones are made.
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MacPherson, A. P. "Gas phase heterocyclisation reactions of free radicals." Thesis, University of Edinburgh, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.657154.
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A new strategy of the synthesis of benzofurans was extended to cases with substituents on the 2,3,5-and/or 6 positions. This involves pyrolysis of 2-allyloxycinnamate esters to generate oxygen centred radicals which cyclise with loss of carbon dioxide and an alkyl radical. Small amounts of substituted coumarin by-products were identified in some cases and their formation rationalised mechanistically. This work was extended in four ways. Firstly the use of 2-t-butylthiocinnamate ester, which generates a sulphur centred radical on pyrolysis, leads to benzothiophene in adequate yield. Secondly when the base benzene ring was replaced by thiophene the preparation of the unusual thieno[3,2-b]furan ring system was achieved. The attempted extension to seven membered ring formation by pyrolysis of 2-substituted-aryl pyrroleacrylates gave instead six membered ring products. Finally the attempted synthesis of pyrrolizine by cyclisation of N-pyrrolylmethyl radicals failed to give any products, although the precursors were successfully prepared. The intramolecular attack of phenoxyl, aminyl, benzyl and thiophenoxyl radicals on ortho disposed pyrrole rings was studied systematically. In the case of the unsubstituted pyrrole ring phenoxyl and aminyl radicals did not cyclise: products showed that 1,5-aryl shifts were taking place following hydrogen atom capture. Benzyl and thiophenoxyl radicals both led to good syntheses of fused tricyclic systems and an investigation of the chemistry of the little known pyrrolo[2,1-b]benzothiophene system was undertaken. 2,5-Dimethyl substituents on the pyrrole ring led to a variety of products in all cases studied (phenoxyl, benzyl and thiophenoxyl). These arose either by direct attack on the pyrrole ring or by an interesting radical transfer, cyclisation sequence from the methyl group. Finally, the radical transfer, cyclisation sequence was again observed when a phenoxyl radical reacted with 2,5-diphenyl substituents on the pyrrole ring. The corresponding thiophenoxyl radical gave a number of products which were separated and identified using a variety of NMR techniques, one of which was a dibenzopyrrolothiazepine, the first example of seven membered ring formation by this method.
27
Yang, Guang. "Detection and assay of oxygen free radicals." Thesis, University of Newcastle Upon Tyne, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.316279.
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Knight, John. "Interaction between free radicals and mucus secretions." Thesis, University of Newcastle Upon Tyne, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.327216.
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Crockett, Rowena. "Generation of free radicals from heterocyclic compounds." Thesis, University of Aberdeen, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.290239.
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Tetrazolinones, thiatriazole 1-oxides and meso-ionic oxatriazoles were investigated as sources of free radicals. Mono-substituted tetrazolinones decomposed at their melting points. Nitrosation and nitration of the tetrazolinone ring was unsuccessful, although alkoxyalkylation of the ring took place in ether in the presence of nitrosomium and nitronium tetrafluoroborate. The tetrazolinone ring was photolytically unstable, and both eliminated nitrogen and cycloreverted. γ-irradiation of the naphthyl deivative caused cleavage of the nitrogen-hydrogen bond to give a radical which was identified by spin trapping and esr spectroscopy. Thiatriazolyl radicals were generated from thiatriazol-1-ium salts by reduction over sodium metal. Deuterium and nitrogen-15 labelled diphenylthiatriazolium salts were prepared in the reaction between thiatriazole 1-oxides and phosphorus pentachloride or pentabromide. This allowed an unambiguous assignment of the nitrogen and hydrogen hyperfine coupling constants in the esr spectrum of the unlabelled thiatriazolyl radical. X-ray crystallographic analysis was carried out on single crystals of 2,4-diphenyl-2,5-dihydro-1,2,3,5-thiatriazol 1-oxide and 2,4-diphenyl-2H-1,2,3,5-thiatriazol-1-ium bromide. Meso-ionic oxatriazolones were relatively stable to thermolysis, whereas oxatriazolimines decomposed at their melting points. The oxatriazolones decomposed on photolysis via two mechanistic pathways, while the oxatriazol-imines were resistant to photolysis. Radicals were generated by γ-irradiation and oxidation via decomposition of the heterocyclic ring. Electrochemical reduction of nitrophenyl derivatives allowed an investigation of radicals in which the heterocyclic ring was remote from the radical centre. Photochemical reaction between the nitrophenyl derivatives of the oxatriazole and tetrahydrofuran produced oxy-nitroxide radicals which were realatively long-lived and in which the heterocyclic ring was intact. The rates of hydrolysis and crystal structures of three diacetylazolinones, including diacetyltetrazolinone were investigated with the aim of determining whether a correlation existed between bond lengths and reactivity. The relative rates of hydrolysis were found to be independent of the bond lengths. However a correlation was found between the rates of hydrolysis and the acidity of the unsubstituted azolinones.
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Stellman, Joan Lindsay. "Free radicals in the pathogenesis of delirium." Thesis, University of Aberdeen, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.394588.
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The aim of this thesis was to look for evidence of increased serum free radical activity in elderly hospital patients with delirium. The following parameters were measured: serum iron, copper, zinc, ascorbic acid, antioxidant activity and markers of lipid peroxidation. The results did not show evidence of increased free radical activity in patients with delirium compared to non-delirious control patients. However, the results did show that, compared to healthy community controls, inpatients with infection and delirium (Group A), or with infection only (Group C) or (unexpectedly) with delirium but without clinical or microbiological evidence of infection (Group D) showed biochemical evidence of a systemic inflammatory response. The pattern of change observed in the inpatient groups was: a reduced serum iron and transferrin saturation, reduced serum zinc, elevated serum copper and reduced plasma ascorbic acid. This pattern of change is associated with inflammation. As a result of these findings, the hypothesis is proposed that delirium represents an epiphenomenon of the systematic inflammatory response syndrome (SIRS). Reduced iron levels, reduced zinc levels and low ascorbic acid levels have all, separately, been associated with altered brain function or cognitive impairment in studies of non-inflammatory states. It is therefore argued that these biochemical changes, individually or in combination with other biochemical and immunological changes that occur during the SIRS, such as HPA axis dysfunction, may result in cognitive impairment during inflammation, and, in severe or predisposing cases, contribution to the clinical manifestation of delirium. It is suggested that the area of the brain most vulnerable to the effects of these changes and, in consequence, most likely to produce cognitive dysfunction during delirium is the limbic system and, in particular, the thalamus, hypothalamus and hippocampus.
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Corlett, Gary Keith. "Laser spectroscopy of metal-containing free radicals." Thesis, University of Leicester, 1997. http://hdl.handle.net/2381/30046.
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Laser-induced fluorescence (LIF) spectroscopy has been used to probe the properties of several metal-containing free radicals, prepared in a supersonic jet expansion by either an electrical discharge or by laser ablation/photolysis. The first spectroscopic observation of the zinc monoethyl radical was carried out following an electrical discharge through a mixture of zinc diethyl and helium. The laser excitation spectra recorded contained extensive vibrational structure, and a partial assignment is presented with the aid of ab initio SCF calculations. This was the first time an electrical discharge had been used to prepare a binary organometallic intermediate in a supersonic jet. LIF excitation and dispersed fluorescence spectra of the MgCCH free radical were obtained following laser ablation of magnesium metal in the presence of methane. This was the first observation of the electronic spectrum of MgCCH, and vibrational progressions in the metal-carbon stretching mode were assigned for both the X˜2sum+ and A 2pi electronic states. Other weak vibrational structure attributable to metal-carbon bending and carbon-carbon stretching modes is also tentatively assigned. In addition, the rotational constant was found for the A 2pi state following a simulation of the observed rotational structure. Laser ablation of calcium and strontium in the presence of benzene gave intense LIF spectra of several well-known and one unknown species. Subsequent analysis of the observed vibrational structure led to the conclusion that the CaCCCH3 and SrCCCH3 free radicals were the spectral carriers, respectively. This task was aided by a series of density-functional theory calculations. This is the first spectral observation of both species. Initial attempts at characterising the alkali metal monoxides by LIF spectroscopy are also presented. These intermediates were to be prepared by laser ablation of the corresponding metal in the presence of N2O. Early experiments focused on the monoxides of Li and Na, and currently only Li + N2O has produced an LIF spectrum. The observed structure, which is quite complex and not amenable to any simple assignment, has been tentatively assigned to the C2pi -- X2pi and C2pi -- A2sum+ systems of LiO. These preliminary findings bode well for future studies of the heavier alkali monoxides.
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Franco, Pujante Carlos. "Organic free radicals for molecular electronics and spintronics." Doctoral thesis, Universitat Autònoma de Barcelona, 2016. http://hdl.handle.net/10803/399515.
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La presente tesis doctoral se centra en el campo de la electrónica molecular, en particular se ocupa del desarrollo de nuevos dispositivos moleculares y del estudio de los fenómenos de transferencias electrónica asociados a ellos. Las propiedad de los policloro trifenilmetil radicales (PTM) han sido utilizadas en este trabajo para investigar los diferentes mecanismos de transferencia de carga asociados a varios sistemas en los cuales los PTM están involucrados.
En la primera parte de la tesis se ha descrito el estudio de los procesos de transferencia de carga a través de dos diferentes familias de hilos moleculares, una de vinilo tiofene y la otra de oligo-p-fenilenos vinilenos fusionado conectados a dos moléculas de PTM las cuales actúan como dadores y aceptores de electrones en sistemas de valencia mixta D-B-A. Estos sistemas han sido completamente caracterizados por diferentes técnicas espectroscópicas en sus diferentes estados de oxidación: neutro, de valencia mixta y oxidada. Además, los mecanismos para la transferencia electrónica intermolecular a través de estos hilos moleculares han sido elucidados.
En la segunda parte de la tesis ha sido reportada la síntesis de una familia de derivados de PTM con grupos tiol conectados al PTM a través de un cadena alquílica de diferentes longitudes, capaces de formar monocapas auotensambladas (SAM) sobre substratos de oro. Asimismo, se ha estudiado los mecanismos de transferencia electrónica a través de las SAMs de PTM en sus diferentes estados de oxidación, contactadas estas por el electrodo de eutéctico galio-indio y por el microscopio de efecto túnel.
Para finalizar, en la última parte de la tesis, se ha reportado el estudio de las propiedades magnéticas y eléctricas de dos derivados de PTM en break-juction unimoleculares de oro y HOPG. Interesante fue el hecho de que en las break-juction unimoleculares de oro, se detectó un pico Kondo lo que indica que el momento magnético del radical PTM interactúa con los electrones de conducción.The present Doctoral Thesis is framed in the field of molecular electronics, specifically is focused on the development of new molecular electronic devices and on the study of the electron transfer phenomena associated to them. We exploit the properties of polychloro thriphenylmethyl radical (PTM) molecules to explore the charge transfer mechanisms involved in many different systems containing PTM derivatives. In the first part of the Thesis, we have described the study of the charge transfer process through two different families of molecular wires, oligo vinylene-thiophne (nTV) and fused oligo-p-phenylene vinylene (nCOPV), connecting two PTM moieties acting as electron donor/acceptor in mixed valence systems D-B-A. These systems were fully characterized by different spectroscopic techniques in their neutral, mixed valence and oxidized states. The mechanism for the intramolecular charge transfer through these wires was elucidated. In the second part of Thesis we have reported the synthesis of a family of PTM derivatives containing a thiol terminal group connected to the PTM through an alkyl chain with different length, able to form self-assembled monolayers (SAM) on gold substrates. We have studied the charge transport mechanisms through PTM SAMs contacted by eutectic gallium-indium electrode and scanning tunneling microcopy, in their different redox states. Finally, in last part of the thesis we have reported the study of the electric and magnetic properties of two PTM derivatives in gold and HOPG single molecule break-junctions. On gold PTM break-junctions, a Kondo peak was detected indicating that the localized magnetic moment of PTM radical interacts with conducting electrons.
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Mondon, K. J. "Enzyme inactivation by pyrimidine and purine free radicals." Thesis, Brunel University, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.332433.
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Ma, Tongmei, and 馬彤梅. "Cavity ringdown laser absorption spectroscopy of free radicals." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2004. http://hub.hku.hk/bib/B30137342.
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Black, Michael. "Gas phase cyclisation reactions of aromatic free radicals." Thesis, University of Edinburgh, 1990. http://hdl.handle.net/1842/10822.
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Lush, Rachel K. "Hydrogen atom abstraction pathways to functionalised free radicals." Thesis, University of Oxford, 2001. http://ora.ox.ac.uk/objects/uuid:84e82ee6-f8b4-4f11-a3d2-30af12f4e0b3.
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Radical translocation chemistry has classically been employed for the generation of carboncentred radicals as a means of remotely functionalising nominally unreactive sites. Previous work within the group had investigated vinyl radicals to effect translocation and had identified a need for a more reactive abstracting radical. In this regard, the high energy of alkoxyl radicals would facilitate rapid 1,5-hydrogen abstraction as opposed to simple reduction. This thesis describes the use of alkoxyl radicals, generated from N-alkoxyphthalimides, to abstract a hydrogen atom selectively from the α-position of a lactam ring. Alkoxyl radicals generated from precursors designed to lead to intramolecular trapping of the translocated radical were prone to β-scission in preference to 1,5-hydrogen atom abstraction. This is attributed to a combination of developing π-overlap in the transition state and stabilisation of the resulting radical both by nitrogen and the attached alkyl substituents. Incorporation of an alkenyl trap onto the lactam ring led to successful 1,5-hydrogen atom abstraction and stereoselective cyclisation, although β-scission remained the dominant pathway. Translocation initiated by nitrogen-centred radicals was investigated and it was found that 1,5-hydrogen abstraction occurred in preference to β-scission; intramolecular trapping of the translocated radical proved impossible either because the precursors were unstable to the reaction conditions or because increased steric bulk impeded hydrogen abstraction by the less reactive aminyl radical. Preparation of bicyclic pyrrolidinones via successive 5-endo-5-exo-trig cyclisations was investigated; the precursors were found to undergo direct reduction in preference to cyclisation. Alkyl or aryl groups attached to the a-acylamino carbon may lead to preferential 5-endo cyclisation by stabilisation of the developing radical in the transition state.
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Gogna, Sanjeev. "The effect of free radicals in neuronal apoptosis." Thesis, University of Warwick, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.341595.
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Zaidi, Naveed Ahmed. "Ring opening/cyclisation in oxiranyl carbinyl free radicals." Thesis, Loughborough University, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.303179.
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Robles, Eric San Jose. "Electronic spectroscopy of jet-cooled organometallic free radicals /." The Ohio State University, 1992. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487776801323524.
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Nicholson, Ian. "Proton electron double resonance imaging of free radicals." Thesis, University of Aberdeen, 1992. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU602265.
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Puwanich, Patana. "Rapid imaging of free radicals using FC-PEDRI." Thesis, University of Aberdeen, 1999. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU602006.
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In the work described in this thesis, new techniques to reduce the electron paramagnetic resonance (EPR) irradiation power required in field cycled proton electron double resonance (FC-PEDRI) and to improve the temporal resolution of FC-PEDRI have been investigated. These are the aims of this work. Details of free radicals and basic principles of EPR and EPR imaging are given and the fundamentals of NMR are also described. The principles of NMR imaging (MRI) are summarised and the essential hardware of MRI for the experiments are also described. Details of PEDRI and FC-PEDRI are also described in this thesis. It is widely realised in MRI that a surface coil, or local RF coil, generates very strong magnetic fields in the coil proximity and that the field decreases rapidly with the distance away from the coil. This should be a useful advantage to limit the EPR irradiation within the desired area of the sample. Hence, the use of a surface coil as an EPR irradiation resonator has been investigated. Not only is the EPR irradiation restricted to the area of interest close to the surface coil but a stronger RF field and high SNR are also generated in this region too. The double resonance coil assembly developed here consisted of a split-solenoid coil (for NMR) and a loop-gap resonator surface coil (for EPR). The results confirmed that the enhancement of NMR signal was higher compared to the whole-body birdcage EPR coil used previously and that the enhancement area was restricted within the proximity of the surface coil. Using the technique of rapid imaging in NMR with FC-PEDRI, fast imaging of free radicals has been investigated. A number of fast pulse sequences are presented in this thesis. A snapshot centric-reordered phase-encoding pulse sequence using the technique of population preparation has been studied and employed. With an essential ideal of EPR irradiation applied only once followed by a snapshot NMR imaging pulse sequence, the EPR power is greatly reduced and the temporal resolution is greatly improved, too. However, the experimental results showed that the image quality needed much improvement and this technique is still limited to be used with samples where the longitudinal relaxation time (Ti) is longer than 250 ms. Next, the rapid imaging of free radicals in very short Ti samples equivalent to biological tissue (typically Ti of -150 ms) was investigated. The basis of image artefacts was studied. From the experimental results, it was found that the snapshot NMR pulse sequence must be commenced very soon after the end of field cycling to avoid the signal enhancement decay. To address the problem of image artefacts, the NMR FID data have been analysed. As a result, phase shift correction and amplitude adjustment schemes have been adopted and applied to the FID data. Details of the data correction schemes are given. Experiments employing rapid imaging of free radicals in vivo using FC-PEDRI are presented. The results show that the rapid imaging in vivo using this technique are possible. However, the resulting images are still noisy. More study is required for further refinement of this technique. Experiments using EPR surface coils with rapid FC-PEDRI were also investigated. The preliminary results obtained from biological-equivalent samples show the possibility of the use of this method in in vivo experiments.
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Beardah, Matthew Simon. "Laser spectroscopy of small metal-containing free radicals." Thesis, University of Leicester, 1999. http://hdl.handle.net/2381/30030.
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The work presented in this thesis is concerned with the preparation of small supersonically-cooled alkaline-earth metal-containing polyatomic molecules by a laser ablation method, with subsequent detection using laser electronic spectroscopy. The results of spectroscopic studies involving three alkaline-earth metal-containing free radicals are presented. A new electronic transition, the D2T,+ -X2T,+ system, of the BaOH free radical is reported. The laser-induced fluorescence (LIF) spectrum is relatively straightforward, showing a simple vibrational progression in the Ba-0 stretching mode (v3). A re investigation of the C - X system of BaOH, carried out under supersonic jet conditions for the first time, is also presented. The LIF excitation spectrum is rather more complex than expected and possible explanations for these observations are considered. Five new electronic transitions of the SrOH free radical are reported for the first time. Three of these, the 52E+-r, £2S+-*2I+ and F2T1-X21,+ transitions, show simple structure in their vibrationally-resolved LIF excitation spectra. Another new transition, the C2TI- X2I,+ transition, is remarkably complex. It is proposed that a combination of Renner-Teller coupling and a 'reverse-polarised' n orbital in the C2TI electronic state is responsible for the added complexity in the LIF excitation spectrum. The 2'2S+ - X2I,+ electronic transition of SrOH shows evidence of vibronic interaction with the nearby C2Tl state. A dispersed fluorescence study of the ground state (X2I > +) of the MgCCH radical is also presented. The results of this study, in addition to a previous FTIR-matrix isolation study, have now accounted for four out of the five fundamental vibrational frequencies of ground state MgCCH. Finally, experiments involving a newly constructed REMPI-TOF mass spectrometer are discussed. Initial test experiments involving NO, CaOH, SrOH and SrCCH show that while the mass spectrometer detection aspect of the instrument is working well, supersonic cooling has proved elusive. Possible design aspects of the spectrometer which may be affecting the supersonic cooling are discussed, along with suggestions for future improvements.
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Pooley, Simon Jonathan. "Electronic spectroscopy of some metal-containing free-radicals." Thesis, University of Leicester, 1998. http://hdl.handle.net/2381/30023.
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Laser-induced fluorescence (LIF) spectroscopy has been used to probe the properties of some metal-containing free-radicals. These radicals were formed using three different techniques; fragmentation through electric discharge, laser ablation and laser photolysis and were studied in a supersonic jet expansion. A dispersed fluorescence spectroscopic study of the zinc-monoethyl free radical was performed. From this work vibrational frequencies, particularly of the Zn-C stretching and the Zn-C-C bending modes, have determined for both the X˜ and A states. In addition several peaks in the excitation spectrum reported by Povey et al. (22500--24000 cm-1) have been assigned. Recently Professor T.A. Miller and co-workers at Ohio State University recorded rotationally-resolved LIF spectra of ZnC2H5 in the 22500--23100 cm-1 region. This study complemented the dispersed fluorescence work described above, so the author was asked to generate a model and interpret this spectra. A Hamiltonian model to simulate rotational structure of asymmetric top molecules which includes spin-rotation terms has been written by the author to form part of a spectral simulation program. This program was used to simulate the rotationally resolved LIF spectra of ZnC2H5 detailed above. Unfortunately a complete analysis has not been possible but values for the A, B and C rotational constants for many of the bands are presented here along with a analysis of the observed values of spin-rotation constants. Finally, LIF spectra of a new electronic transition of BaOH, the D˜2sum+ - X 2sum+ system has been observed. Also, the C˜ - X˜ system was reinvestigated. The C˜ - X˜ system is particularly interesting because it shows much more complexity than might be expected from previous studies. Vibrationally and partially rotationally resolved spectra are reported for both systems and the C˜ - X˜ region offers some evidence that the molecule may be bent in the excited state with a large spin-rotation interaction coupling.
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Garg, Dhiraj Kumar. "Numerical modeling and simulation of polymerization reactions in coiled flow inverters." Thesis, Strasbourg, 2014. http://www.theses.fr/2014STRAE002/document.
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L’objectif de ce travail fut d’améliorer la modélisation et la simulation de la polymérisation radicalaire dans des réacteurs continus et discontinus. Une solution analytique explicite généralisée (AS) fut obtenue dans le cas de la polymérisation en masse/solution, homogène et isotherme menée dans un réacteur fermé de volume variable. Les différentes étapes considérées furent l'initiation, la propagation, le transfert au monomère, au solvant, à un agent de transfert de chaîne, la terminaison par combinaison et dismutation. Différents modèles rendant compte des effets de gel, de vitrification et de cage ont également été considérés. AS a été validée avec succès par comparaison avec des solutions numériques et des données expérimentales de la littérature. Par ailleurs, AS a été étendue à des conditions pour lesquelles elle ne fut pas originellement développée comme par exemple des conditions non isothermes. La polyvalence et la flexibilité de AS sur l’ensemble de l’échelle de conversion du monomère furent ainsi démontrées. Ensuite, pour élargir encore plus son champ d'application, AS fut utilisée dans des simulations numériques (CFD). Une nouvelle transformation très simple a été proposée afin d’adimensionnaliser les constantes cinétiques en terme de concentration. Cela a permis de rentrer dans les simulations les données chimiques sous leur forme originale en mole et de faciliter ainsi le codage et le débogage du code de calcul. Cette transformation a ensuite été utilisée pour évaluer trois géométries tubulaires de microréacteur, un réacteur tubulaire droit (STR), à géométrie hélicoïdale (CTR) et à inversion de flux (CFIR), dans des conditions d'alimentation différentes (fluides d’entrée non ou parfaitement mélangés) et à de très faibles nombres de Reynolds (<1). La modélisation a été réalisée avec des paramètres constants ou variables des propriétés physiques du fluide sous écoulement (densité, viscosité et conductivité thermique) ainsi qu’en variant de manière discrète les coefficients de diffusion. Leurs effets sur les résultats de simulation ont été observés et comparés avec les données expérimentales publiées pour 4 monomères différents et furent en très bon accord. Les résultats pour le cas d’un mélange parfait furent indépendants de la géométrie des microréacteurs. Le CFIR semble être le réacteur le plus prometteur puisque, dans les conditions de microréaction étudiées, il a permis le meilleur contrôle des caractéristiques du polymère synthétiséThis thesis aimed at improving the modeling and simulation of free radical polymerization (FRP) in batch as well as in flow reactors. A generalized explicit analytical solution (AS) was obtained in case of variable volume, bulk/solution polymerization, homogeneous and isothermal batch reactor. The reaction steps included initiation, propagation, transfer to monomer, transfer to solvent, transfer to chain transfer agent (CTA), termination by combination and disproportionation. Different models of gel, glass and cage effects were also implemented explicitly. AS was validated against numerical solutions as well as published experimental data and was found in good agreement. Furthermore, its applicability was extended to conditions for which AS was not derived, i.e. non-isothermal conditions. The versatility and flexibility of AS over the complete range of monomer conversion were thus demonstrated. Then, to broaden its applications range even more, AS was used in CFD simulations. A new and simple transformation was proposed to make kinetic rate coefficients dimensionless in terms of concentration. This enabled chemical data to be fed in molar form to CFD modeling. It also enabled easy coding and debugging by keeping the original form of generation terms intact. The results were found to be improved after validation against experimental data. This transformation was then used for evaluating three tubula microreactor geometries, namely straight tube reactor (STR), coiled tube reactor (CTR) and coil flow inverter reactor (CFIR), under different feed conditions (unmixed or perfectly mixed) at very low Reynolds numbers (<1). The modeling for FRP was performed with constant or variable fluid physical parameters (density, viscosity and thermal conductivity) along with discrete variation of diffusion coefficients. Their effects on simulation results were observed and compared with published experimental data for 4 different monomers and were found to match perfectly. Results for mixed feed condition were found to be independent of microreactor geometry. CFIR seems to be the most promising reactor design under microreaction investigated conditions as it allowed the best control over polymer characteristics
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Mills, Tim. "Studies in free radical chemistry." Thesis, University of Nottingham, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.342465.
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Krudopp, Heimke [Verfasser]. "Free lipid radicals and nitroxide radicals in dispersed systems studied by EPR spectroscopy / Heimke Krudopp." Kiel : Universitätsbibliothek Kiel, 2018. http://d-nb.info/1173163212/34.
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L-, B. Cheton Paulette 1962. "The biological role of manganese and hydroxyl free radicals /." Thesis, McGill University, 1987. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=63965.
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Donato, Karen Ann. "Graft polymerization of methyl methacrylate onto polytetrafluoroethylene free radicals." Ohio : Ohio University, 1985. http://www.ohiolink.edu/etd/view.cgi?ohiou1183996024.
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Feng, Ying-Hong. "Effects of oxygen free radicals upon selected biological systems." Thesis, University of Oxford, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.359462.
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Gillett, David Alan. "Transient free radicals studied by laser magnetic resonance spectroscopy." Thesis, University of Oxford, 1994. http://ora.ox.ac.uk/objects/uuid:038bdb7e-1f8c-4112-bcea-4a0ca7ab7bcf.
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A liquid nitrogen cooled, carbon monoxide laser magnetic resonance spectrometer was used to study mid-infrared vibration-rotation transitions in the gaseous free radical NCO, in its ̅X2Π state, at very high resolution. The use of an intracavity absorption cell made possible the observation of some transitions with sub-Doppler resolution. Developments to the spectrometer extended the range of operation of the CO laser. Most importantly, a CO laser operating on overtone transitions, Δν = 2, was operated in Oxford. The Δν = 2 CO laser operates over the range 2450-3800cm-1 (4.08-2.63 μm), and the Δν = 1 CO laser over the range 1200-2100 cm-1 (8.33-4.76 μm). NCO exhibits a Renner-Teller effect in its ground electronic state, an interaction between the motion of the electrons and the bending motion of the nuclei. Vibration-rotation transitions were observed in a sequence of bands involving the excitation of the out-of-phase stretching vibration, in the region of 1900cm-1. Some of the bands involved the excited bending vibration. The Zeeman effect behaviour of the molecular energy levels, particularly in the 2Σ vibronic states, clearly showed the manifestation of the Renner-Teller effect. The Zeeman effect in the 2Σ vibronic states was considered in detail. Many of the 2Σ LMR spectra were recorded at sub-Doppler resolution. NCO is complicated to model, and unassigned LMR spectra remain. A harmonic Renner-Teller model was developed for the analysis. It was implemented by constructing an explicit matrix representation of the single electronic state N2 effective Hamiltonian, which was diagonalised exactly. A new term in this Hamiltonian, describing centrifugal distortion corrections to the Renner-Teller coupling term, was developed for the 2Σ vibronic states in order to account for anharmonic vibronic interactions.