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Pimblott, Simon M. "Application of stochastic models to radiation chemistry." Thesis, University of Oxford, 1988. http://ora.ox.ac.uk/objects/uuid:7b7fa46c-dd6f-4c8a-a98f-9e43b536ace5.
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This thesis addresses one area of major interest in reaction kinetics, the theoretical description of recombination in nonhomogeneous systems. The reaction of the highly reactive particles formed by the passage of ionising radiation through a medium is an important example of this type of system. Stochastic effects are apparent in every stage of the development of a radiolysis system: in the interaction between the radiation and the medium and in the diffusion and reaction processes that follow. Conventional models for nonhomogeneous kinetics in radiation chemistry are based upon a deterministic analysis. These models are appraised together with an alternative stochastic approach. Three stochastic methods are discussed: a full Monte Carlo simulation of the diffusion and reaction and two approximate models based upon an independent pairs approximation. It is important that any kinetic model accurately describes the system it purports to represent and this can only be assured by extensive validation. The stochastic models are developed to encompass the diffusion-controlled reactions of ions and radicals and to include the effects of a bulk electrolyte upon the reactions between ions. To model a realistic radiation chemistry reaction scheme, it is necessary to consider reactions that are not fully diffusion-controlled. The radiation boundary condition is introduced and used to extend stochastic modelling to partially diffusion-controlled reactions. Recombination in an anisotropic environment is also considered. Although a complete analysis of the chemistry of a radiolysis system requires a complex reaction scheme, the scheme can be simplified, in acid and in alkali, by the use of an instantaneous scavenging approximation. In acid, this approximation produces a simple three reaction mechanism based upon five species: H, OH, H2 , H20 and H202 . The acid system is used to demonstrate the stochastic treatment of realistic kinetics. The instantaneous scavenging approximation is examined in detail and techniques are developed for the explicit modelling of reactions with a homogeneously distributed scavenger. A stochastic treatment of nonhomogeneous reaction kinetics requires a description of the initial spatial distribution of the reacting particles. A rudimentary Monte Carlo simulation is used to determine a simple distribution of clusters of reactive particles similar to that found along the path of a high energy electron in water. This distribution provides a suitable basis for kinetic simulation. The kinetics of a more detailed idealised track structure are also considered and the stochastic and deterministic kinetics of extended particle distributions are discussed.
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Piña-Sandoval, Flora Marcela. "The application of microwave radiation in materials chemistry." Thesis, University of Edinburgh, 2007. http://hdl.handle.net/1842/27193.
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We have developed tuned or tunable microwave cavities to be used in conjunction with an X-ray diffractometer working either in transmission mode with a capillary sample, or in reflection mode, with a flat plate. We have also developed further a microwave cavity that enables high-resolution neutron powder diffraction patterns to be taken, and tested it successfully on the High Resolution Powder Diffractometer (HRPD), at the ISIS Facility UK. One application that was planned was the elucidation of synthetic steps in the microwave-assisted formation of the zeolite ZSM-5. We also studied microwave-assisted processing of zeolites Na-Y and H-ZSM-5, accelerating the insertion of nickel, copper of molybdenum ions in the solid-state. Phase transitions in the ferroelectric materials BaTiO3, and KNbO3 were studied by in situ diffraction to determine whether microwave irradiation can influence the transition between phases of different dielectric susceptibility, and evidence for a lower transition temperature in both cases compared to that of conventional heating. In situ neutron diffraction measurements have provided the first direct evidence of a differential heating under microwave irradiation of heterogeneous catalysts in the form of MoS2 or Ni particles dispersed over a high surface area Al2O3 support. Finally, we performed in situ X-ray diffraction on a sample of AgI held in a glass capillary to observe the transformation between the dense β phase, and the more open, fast-ion conducting α phase; this revealed a significant reduction in the transition temperature, possibly arising from a strong interaction between the microwave field and the defects or lattice modes implicated in the transition.
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Wilkinson, Susan Anne. "Aspects of radiation curing." Thesis, City University London, 1989. http://openaccess.city.ac.uk/7720/.
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The electron beam induced polymerisation of dialkyltin diacrylates, as well as the UV and electron beam induced polymerisation of some novel silicon containing acrylates are discussed. The reactivity and film forming properties of these materials are compared with that of some commercial diluents such as, tripropyleneglycol diacrylate, TPGDA and trimethylolpropane triacrylate, TMPTA. Mechanistic studies concerning the initiation of free radical polymerisation of the acrylate ester, isodecylacrylate, IDA on electron beam irradiation are presented. Addition of electron and hole scavengers revealed that slow electrons contribute significantly to the initiation of electron beam induced polymerisation of acrylate esters. The film forming properties of phenyl acrylate and mono-, di- and tri- halophenyl acrylates on exposure to electron beam irradiation are evaluated in terms of their ability to produce tackfree films. The sensitivity of catechol diacrylate compared with t-butyl catechol diacrylate is also presented. Mechanistic studies concerning the initiation of both UV and electron beam induced cationic polymerisation of 3,4-epoxycyclohexylmethyl-31,41 -epoxycyclohexanecarboxylate, with the aid of diphenyliodonium hexafýuorophosphate, triphenylsulphonium hexafluorophosphate and (n -2,4-cyclopentadien- I-yl) [(I, 2,3,4,5,6-n) (-I-methylethyl) benzene] -iron(I+) hexafluorophosphate, as well as the radiolysis of 6,7-epoxy- 3,7-dimethyloctylacrylate in the presence of diphenyliodonium hexafluorophosphate are presented. The decomposition of the salts was monitored in situ by infrared and UV spectroscopy and hydrogen fluoride is credited as the true initiator of the cationic polymerisation of epoxides in an open system. The UV photolysis of the aforementioned onium salts led to the production of volatiles, resulting in the polymerisation of thin films of 3,4-epoxycyclohexylmethyl-31,41 - epoxycyclohexanecarboxylate, providing further evidence of hydrogen fluoride evolution. The use of FTIR- photoacoustic spectroscopy was proven to be an invaluable tool in monitoring the polymerisation of thin epoxide or acrylate films on an opaque substrate.
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MUSICO, FILHO WALTER. "Efeito da radiacao ionizante no prolipropileno nacional." reponame:Repositório Institucional do IPEN, 1995. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10453.
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Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
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Bazzi, Sophia [Verfasser], and Robin [Akademischer Betreuer] Santra. "Ab initio radiation chemistry / Sophia Bazzi ; Betreuer: Robin Santra." Hamburg : Staats- und Universitätsbibliothek Hamburg, 2019. http://d-nb.info/1201087171/34.
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Preston, Christopher M. L. "Poly(dimethylsiloxane) : blends with poly(urethane) & radiation chemistry /." [St. Lucia, Qld.], 2000. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe16169.pdf.
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Khan, Niaz Ahmad. "Aspects of radiation curing." Thesis, City University London, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.241483.
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Mohajerani, Shahroo. "A study of the radiation chemistry of poly(tetrafluoroethylene-co-hexafluoropropylene) /." St. Lucia, Qld, 2001. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe16518.pdf.
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Hasan, N. M. "Effects of ionizing radiation on biomolecules." Thesis, University of Salford, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.234702.
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Astill, David Timothy. "Synthesis and radiation stability of silicone elastomers." Thesis, Sheffield Hallam University, 1985. http://shura.shu.ac.uk/19292/.
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A wide range of polymer samples based upon polydimethylsiloxane (PDMS) have been subject to gamma irradiation, and the subsequent effects analysed using a variety of techniques. The preparation of a series of blends and block copolymers of PDMS containing small amounts of polystyrene (PS) is described, and their characterisation by spectroscopic and thermal analytical methods is discussed. A PD11S gum gave a G(X) value of 2.8 which is in good agreement with other reported values. Thermal analysis revealed a shift of 20°C. in the glass transition temperature, and disappearance of the exotherm band, upon onset of gelation. Within the sol component of a cross-linked sample, a complex range of reactions are evident which are related to the absorbed dose. It was found with PS-PDMS blends, upon absorption of low doses of radiation, that the amount of gel produced is very much lower than that observed with PDMS. A substantial degree of radiation protection was observed with a 3% W/w PS blend, which required a gelation dose of almost five times that of homopolymer PDMS. A selected number of block copolymers were irradiated and the gelation dose was again found to be far greater than would be expected of PDMS of similar relative molecular mass. Morphological studies allowed calculation of the size of the PS average domain size which increased with % w/w PS in the blend or copolymer. It is proposed that the radiation protection observed with polymers containing PS is related to the PS average domain size. The large surface area/volume ratio found with a 3% w/w PS blend would facilitate a considerable degree of miscibility of PS with PDMS, thereby decreasing the susceptibility of PDMS to cross-link formation.
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Agarwal, Amit. "Simulation studies of recombination kinetics and spin dynamics in radiation chemistry." Thesis, University of Oxford, 2011. http://ora.ox.ac.uk/objects/uuid:0b46a048-a2c9-4964-81e1-f526cc00c03d.
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Radiation chemistry is concerned with understanding the chemical kinetics following the application of ionising radiation. There are two main methods for modelling recom- bination and spin dynamics in radiation chemical systems: The Monte Carlo random flights algorithm, in which the trajectories of the diffusing species are followed ex- plicitly and the Independent Reaction Times (IRT) algorithm, where reaction times are sampled from appropriate marginal distribution functions. This thesis reports develop- ments to both methods, and applies them to better understand experimental findings, particularly spin relaxation effects. Chapter 4 introduces current simulation techniques and presents newly developed algorithms and simulation programs (namely Hybrid and Slice) for modelling spatially dependent spin effects. A new analytical approximation for accurately treating ion-pair recombination in low-permittivity solvents in also presented in this chapter. Chapter 5 explores the photodissociation of H₂O₂, where there is some controversy in the literature on the spin state of the precursor. This chapter explores the possibility of reproducing the observed spin polarisation phase using the Radical Pair Mechanism. Chapter 6 presents two new algorithms for treating reactive products in the IRT framework. These have been tested for two chemical systems: (i) photodissociation of H₂O₂ where the ·OH are scavengeable; (ii) water photolysis which produces H⁺, ·OH and e⁻_aq. In the latter case a careful handling of three body correlations is required. Chapter 7 presents simulation results which suggest a strong correlation between scavenging and ion recombination in low permittivity solvents. A path decomposition method has been devised that allows IRT simulations to be corrected for this effect. Chapter 8 presents evidence for spin-entanglement and cross-recombination to act as an extra source of relaxation for ion-recombination in low permittivity solvents. It is hypothesised this effect contributes to the anomalous relaxation times observed for certain cyclic hydrocarbons. Chapter 9 presents an extension of the IRT simulation method to micelles. The kinetics are shown to be accurately described using the mean reaction time and the exponential approximation.
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Jones, Luke. "The radiation chemistry of gases at the interface with ceramic oxides." Thesis, University of Manchester, 2016. https://www.research.manchester.ac.uk/portal/en/theses/the-radiation-chemistry-of-gases-at-the-interface-with-ceramic-oxides(2516a65b-1d12-41a4-b4a3-78226f0eafda).html.
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As of 2011, the UK had 112 tonnes (t) of plutonium dioxide PuO2 in interim storage at the Sellafield site and this is increasing by approximately 5 t per annum with the continued reprocessing of spent nuclear fuel. PuO2 is stored in small quantities in a sealed multi-canister system for security and ease of handling. During long term storage, radiolysis of the gas phase and adsorbed species could potentially lead to canister pressurisation and/or failure. It is of great importance to understand the mechanisms occurring in the gas phase and to understand the resulting gas phase composition after decades of storage. This research investigates the radiation chemistry of two gas phase systems in the presence or absence of inactive PuO2 surrogate material (namely cerium dioxide (CeO2) and zirconium dioxide (ZrO2)).The systems of interest are, firstly, radiolysis of hydrogen (H2), oxygen (O2) and argon gas mixtures utilising both 60Co gamma rays and He(2+) accelerated ions. Depletion of H2 and O2 has been investigated using gas chromatography. A bespoke manifold has been designed to mix these gases in various ratios, suitable reaction vessels and a subsequent sampling system has been developed to undertake this research. The rate of H2 depletion is independent of initial H2 concentration and radiation type. In the presence of an oxide surface, the rate of H2 depletion is vastly increased when compared to homogeneous studies using 60Co gamma rays. Depletion is greatest in the presence of ZrO2. In all systems, depletion of H2 is linear with increasing absorbed dose. The second system of interest is the radiolysis of moist air utilising 60Co gamma rays. Formation of nitric acid (HNO3) has been investigated using ion chromatography to determine nitrate (NO3-) anion production. Nitrate production increases linearly with absorbed dose and is greater in the presence of an oxide powder. The rate of production increases with increasing mass of oxide. Oxalate (C2O42-) was produced radiolytically from dimerisation of carbon dioxide and was greatest in the presence of ZrO2. Reducing the specific surface area of CeO2 reduced the concentration of nitrate formed when compared to higher surface area CeO2.
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Giroux, Louis. "Photochemistry of ethylene with infrared and ultraviolet radiation." Thesis, University of Ottawa (Canada), 1988. http://hdl.handle.net/10393/20878.
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Xu, Alan. "Atomic scale characterisation of radiation damage and radiation induced precipitation in tungsten-rhenium alloys." Thesis, University of Oxford, 2015. https://ora.ox.ac.uk/objects/uuid:1ae33661-c81f-4e77-a80c-bc12ed9123d9.
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Tungsten is considered the prime candidate material for plasma facing components within fusion reactors. However, exposure of tungsten to neutron flux brings about transmutation of tungsten into by-products: Re, Os and Ta. Under increasing levels of radiation damage, irradiation induced clustering/precipitation takes place that embrittles and thus reduces lifetime of such tungsten components. This thesis was undertaken to explore this subject on a deeper level. There are three components to this study. The first part considers the effect of Re content on irradiation induced clustering. Lab-made plate W-xRe (x: 2, 5, 10 and 25at.%) alloys were exposed to 1.2, 3.9 and 33dpa, self-ion irradiated at 773K. Analysis of cluster number density and volume fraction found they increase with damage level and bulk Re content. Based on these trends and existing literature data, a hypothesis was proposed suggesting clusters originate from vacancy clusters. Also, at 33dpa, rod shaped clusters form in W-25Re alloys while spherical clusters are present in other alloys. The clusters show close correspondence with irradiation induced precipitates and appear to be precursor phase. In the second part of this thesis, the effect of Os and Ta on cluster formation and alloy mechanical properties is examined. Lab-made plate W-1Re-1Os and W-2Re-1Ta alloys were irradiated at 33dpa at 573 and 773K and compared against control W-2Re alloy. At 33dpa and 573K, the Os and Ta presence suppresses cluster formation. Both ternary alloys contain smaller cluster diameter, composition, number density and volume fraction than the W-2Re alloy. However, at 33dpa and 773K, Os and Ta have opposing effects on cluster behaviour. Os increases the cluster nucleation rate and raises irradiation hardening (compared to W-2Re). Meanwhile, Ta presence decreased cluster number density and reduced the irradiation hardening (compared to W-2Re alloy). As well, Ta showed no evidence of clustering, only Re clusters form in the W-2Re-1Ta alloy. The final aspect of the thesis analyzes the effect of material microstructure and external variables on cluster formation in W-Re alloys. Commercial wire form W-25Re alloy was irradiated at 1.2dpa at 573 and 773K as atom probe needles and bulk sample. The larger free surface on atom probe needle samples appears to act as a sink for self-interstitials and vacancies at both temperatures. The effect of grain size and dislocation density was examined by irradiating commercial W-5Re wire (0.5-1μm diameter) and plate (1-3mm diameter) samples (annealed and unannealed) to 33dpa and 573K. It was found grain boundaries and dislocations act as defect sinks at 573K. Additionally, radiation enhanced Re grain boundary enrichment was observed for first time. The effect of grain size on cluster behaviour at 773K was also analysed. Commercial wire and lab-made plate W-3Re, W-5Re and W-25Re alloys were irradiated to 33dpa at 773K. The larger grain boundary area in wire samples is suspected of acting as a sink for self-interstitials leaving more vacancies for promoting cluster formation compared to lab-made samples. The discoveries made in this thesis broaden our current understanding of irradiation induced phase formation in tungsten. Their implications on plasma facing component design are discussed as well as recommendations for improvements. Further, areas requiring further research in this field are also highlighted.
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Trentmann, Jörg. "Atmospheric processes in a young biomass burning plume radiation and chemistry /." [S.l.] : [s.n.], 2001. http://www.sub.uni-hamburg.de/disse/568/Disse.pdf.
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Eypper, Marie. "Photoionisation studies of reactive intermediates with synchrotron radiation." Thesis, University of Southampton, 2009. https://eprints.soton.ac.uk/191337/.
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Abdallah, Suaad Audat. "Investigation of Oxidative DNA Damage from Ionizing Radiation." University of Toledo Health Science Campus / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=mco1349377002.
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Gerstel, Markus. "Radiation damage in protein crystallography : susceptibility study." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:be55baee-19b7-4a34-8694-fb9c3606a19c.
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Protein structure models obtained from X-ray crystallography are subject to radiation damage. The resulting specific alterations to protein structures can be mistaken for biological features, or may obscure actual protein mechanisms, leading to misidentification or obscuration of biological insight. The radiation chemistry behind this site-specific damage is not well understood. Radiation damage processes progress in proportion to the dose absorbed by the crystal in the diffraction experiment. Doses can be estimated using existing software, but these assume idealised experimental conditions. To simulate complex diffraction experiments, including treatment of imperfect X-ray beam profiles and inhomogeneous dose distributions, a new program, RADDOSE-3D, was developed. RADDOSE-3D can be integrated into beamline software to provide convenient, more accurate, comparative, and publishable dose figures, also facilitating informed data collection decisions. There is currently no method to automatically detect specific radiation damage in protein structure models in the absence of an 'undamaged' reference model. Radiation damage research therefore generally relies on detailed observation of a few model proteins. A new metric, BDamage, is designed and used to identify and quantify specific radiation damage in the first large-scale statistical survey of 2,704 published protein models, which are examined for the effects of local environments on site-specific radiation damage susceptibility. A significant positive correlation between susceptibility and solvent accessibility is identified. Current understanding of radiation damage progression is mostly based on a few consecutive structure model 'snapshots' at coarse dose intervals. The low sampling rate considerably limits the ability to identify varying site susceptibility and its causes. Real space electron density data are obtained for crystals of different mutants of a RhoGDI protein with very high sequence identity, to determine sensitising and stabilising factors for radiation induced structural changes. Utilising a newly developed data collection and analysis protocol, these changes could be tracked with unprecedented time resolution.
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Halevy, Patrick. "Protection mechanisms of novel photoyellowing inhibitors." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape3/PQDD_0034/MQ64366.pdf.
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Fields, Robert Eugene 1958. "Application of a quadrupole ion trap mass spectrometer to ICP-MS and the direct detection of x-rays using a charge-injection device." Diss., The University of Arizona, 1997. http://hdl.handle.net/10150/282314.
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This work describes the construction of an inductively-coupled plasma tandem quadrupole mass spectrometer where a quadrupole ion storage trap acts as a second sector and collision cell to achieve neutralization or collisional dissociation of interfering species before mass analysis. Because most elements exist as singly-charged ions in an inductively-coupled plasma (ICP) plume, the ICP can be used as an ionization source for mass analysis (ICP/MS). By reducing the sample to elemental ions before mass analysis, ICP/MS spectra tend to be simple compared with those obtained by ICP-optical emission spectrometry (ICP-OES) where elements may have hundreds to thousands of emission lines and spectral overlaps can be severe. This is especially troublesome in the analysis of rare earth elements which have the largest numbers of active emission lines when excited in an ICP. In addition, detection limits by ICP/MS are often up to 3 orders of magnitude lower than by ICP-OES. ICP/MS analysis is not immune from isobaric and isotopic interferences or matrix effects. For most analyses, an acid digestion precedes aspiration as an aqueous solution into an argon plasma gas. This can lead to large amounts of Ar+ etc., which may interfere to varying degrees with analytes of interest. Oxides, argides and hydrides of matrix ions or other analytes may also form and interfere. These same processes can also split peak areas between the atomic form of an analyte and the molecular. In isotope ratio studies where precise measurements on more than one isotope per analyte are needed, these effects may be compounded. Isobaric interferences normally require high resolution mass analysis to resolve if they cannot be separated prior to sample introduction. However, the interface between a high vacuum, high resolution sector or ion cyclotron resonance mass spectrometer and an atmospheric pressure plasma is non-trivial and such instruments are expensive. The focus of this work is new approach which uses a collision cell where weakly-bound molecular species can be dissociated and ions with relatively high electron affinities, such as Ar+, can be neutralized through charge exchange reactions.
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Bazafkan, Sedighealsharieh. "Radiation protection on polysaccharide solutions and gels." Thesis, University of Salford, 1996. http://usir.salford.ac.uk/14771/.
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The effects of ionizing radiation on solutions of (1) sodium alginate, (2) alginate gels (wet and dry), (3) xanthan gum, (4), locust bean gum (LBG) and (5) carboxymethyl cellulose (CMC), have been investigated. Problems arise in the radiation sterilization of these gums (either as a solution or gel) due to reduction in their viscosity and the gel strength, caused by the high doses (25kGy) commonly used for the purpose of sterilization. The alginates used here were manugel DMB, manugel DPB and manucol DMF. The irradiations were carried out using 'Co-ry-source and the gels and solutions were analysed by measurement of their apparent viscosities using a Brookfield viscometer L.V.T. The data shows that 2% solutions of the sodium salt of the three alginates used here are all pseudoplastic. There is a rapid decrease in viscosity of solutions irradiated up to a dose of 0.5kGy, and the initial rate of viscosity decrease is unaffected by the presence or absence of air. Inclusion of mannitol at high concentration (15%) could, at least partially, protect the alginate solutions degradation by scavenging -OH radicals. The possibility of using 60Co-7-radiation to sterilize alginate gels (wet gels) was also studied. Gels of this type have potential use of wound care. Those prepared here could bend easily. Irradiated to 25 kGy, the gels readily crack by becoming more brittle, are easily squashed and lose water. Inclusion of mannitol improved the quality of the gels and again indicates its protective role in these systems. When alginate solutions containing mannitol and the gelling agents 5-gluconolactone and calcium orthophosphate were irradiated separately and then mixed, gels were formed, indicating that pre-sterilization of the components by irradiation is a feasible method of preparation of sterile gels. Gels that were concentrated (dry) by water evaporation were more stable to radiation (25 kGy). The gels that had the greatest capability to take up saline and to be manipulated most easily (both before and after irradiation) were those that contained initially 2% alginate and 5% mannitol, and dried to a quarter of the original weight (ie. the gel now contained 8% alginate and 20% mannitol). These gels were clear and pliable and after irradiation to 30 kGy remain stable in saline for up to 24 hours. The effect of ionizing radiation on xanthan and LBG solutions are also studied. The initial studies indicated that these solutions were also pseudoplastic. Irradiation of xanthan gum solutions caused a rapid initial decrease in apparent viscosity. t-Butanol had some protective effect on xanthan-LBG and xanthan-NaC1 solutions. Addition of mannitol (20%) to xanthan gum solutions again only partially protects the solutions. The solutions with highest apparent viscosity were those prepared by mixing equal volumes of solutions of LBG 1%, mannitol (20%) and ascorbic acid (10" mol dm') and solutions of xanthan gum (1%), mannitol (20%) and ascorbic acid (10' mol dm'). The viscosity of this solution falls from 300,000 cps to 250,000 (shear rate 0.07s4), after irradiation to 25 kGy. Therefore, whereas xanthan gum solutions containing readily depolymerized by irradiation, very high viscosity irradiated xanthan solutions containing thickening agents (LBG) and radiation protectors (mannitol - ascorbic acid) can be prepared. Solutions of CMC are also pseudoplastic. Irradiation to 25 kGy resulted in a decrease in the apparent viscosity of solutions of CMC/mannitol/ascorbic acid from — 180,000cps to 8,000cps, whereas for solutions of CMC alone and for CMC/mannitol solutions the viscosity was less than 500cps. This further illustrates the protective effect of ascorbic acid as was observed for xanthan solutions and also suggests that mannitol radicals cause depolymerization of CMC.
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Llano, Jorge. "Modern Computational Physical Chemistry : An Introduction to Biomolecular Radiation Damage and Phototoxicity." Doctoral thesis, Uppsala University, Department of Cell and Molecular Biology, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-4224.
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The realm of molecular physical chemistry ranges from the structure of matter and the fundamental atomic and molecular interactions to the macroscopic properties and processes arising from the average microscopic behaviour.
Herein, the conventional electrodic problem is recast into the simpler molecular problem of finding the electrochemical, real chemical, and chemical potentials of the species involved in redox half-reactions. This molecular approach is followed to define the three types of absolute chemical potentials of species in solution and to estimate their standard values. This is achieved by applying the scaling laws of statistical mechanics to the collective behaviour of atoms and molecules, whose motion, interactions, and properties are described by first principles quantum chemistry. For atomic and molecular species, calculation of these quantities is within the computational implementations of wave function, density functional, and self-consistent reaction field theories. Since electrons and nuclei are the elementary particles in the realm of chemistry, an internally consistent set of absolute standard values within chemical accuracy is supplied for all three chemical potentials of electrons and protons in aqueous solution. As a result, problems in referencing chemical data are circumvented, and a uniform thermochemical treatment of electron, proton, and proton-coupled electron transfer reactions in solution is enabled.
The formalism is applied to the primary and secondary radiation damage to DNA bases, e.g., absorption of UV light to yield electronically excited states, formation of radical ions, and transformation of nucleobases into mutagenic lesions as OH radical adducts and 8-oxoguanine. Based on serine phosphate as a model compound, some insight into the direct DNA strand break mechanism is given.
Psoralens, also called furocoumarins, are a family of sensitizers exhibiting cytostatic and photodynamic actions, and hence, they are used in photochemotherapy. Molecular design of more efficient photosensitizers can contribute to enhance the photophysical and photochemical properties of psoralens and to reduce the phototoxic reactions. The mechanisms of photosensitization of furocoumarins connected to their dark toxicity are examined quantum chemically.
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Al-Samra, Eyad H. "Diffusion kinetics in radiation chemistry : an investigation of competition and correlation effects." Thesis, University of Oxford, 2015. https://ora.ox.ac.uk/objects/uuid:9771e740-c142-4dc2-85bc-897a4cf86320.
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The study of radiation chemistry is very important because of the wide range of applications. Many of the processes in radiation chemistry evolve randomly and can be modeled using the theory of stochastic process. The main aim of this thesis is to study correlation effects in model systems of the type found in radiation chemistry, i.e. clusters of reactive particles. Studies of this type involve a substantial amount of computer simulation. The first work described in the thesis shows how the Message Passing Interface can be incorporated in the algorithms used to simulate radiation chemical kinetics and how that can improve the performance of the programs. The reaction probability for two diffusing particles is well known, and current theories are based on this, making the approximation that pair distances evolve independently. This work analyses some correlation effects that appear in a system of three particles, with some new results, notably in the distribution of the joint distribution of the distances and the underlying 3-body backward diffusion equation, but it has not yet been possible to use these results to introduce corrections in the working simulations. The competition between scavenging and recombination is investigated in detail in chapters 4-6. A correction to the Smoluchowski theory for a fully-diffusion controlled reaction is proposed, and it is shown how the Independent Reaction Times method can be used to simulate this competition. The approximation is justified both by comparison to simulation results and theoretically, and is shown to apply to all the ordered scavenging reactions in a multi-particle system. Finally, the problem of modeling a reversible reaction is briefly investigated in chapter 7. The main result of this chapter is a generalization of previous work on the distance between a pair conditional on its future reaction time, generalized to a radiation boundary condition.
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Caló, A. (Antonio). "Electron spectroscopy of atoms and molecules using synchrotron radiation, UV radiation and electron impact." Doctoral thesis, University of Oulu, 2007. http://urn.fi/urn:isbn:9789514286650.
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The present thesis investigates the electronic structure of selected atoms and molecules in vapor phase. Electron spectroscopy is applied for studying the electronic transitions following excitation and ionization with electron and photon bombardment. The work focuses on the photoionization and Auger decay of selected noble gasses, and on the photoionization and Auger decay of core ionized or resonant excited alkali halide molecules. The experimental results are compared with theoretical predictions.
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Wei, Lihui. "Design, synthesis and characterization of rhenium complexes for the development of diagnostic and therapeutic agents in nuclear medicine." Related electronic resource: Current Research at SU : database of SU dissertations, recent titles available full text, 2005. http://wwwlib.umi.com/cr/syr/main.
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Fobi, Kwabena. "Purity Optimization of D-Gamma-Tocotrienol from Palm Oil. A Promising Radiation Protective Agent for Treatment of Acute Radiation Syndrome." Digital Commons @ East Tennessee State University, 2020. https://dc.etsu.edu/etd/3739.
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D-γ-tocotrienol (G-T3) chiefly present in palm oil has stolen the spotlight as a promising radiation protective agent for the treatment of acute radiation syndrome (ARS). Although G-T3 is a promising counteracting agent discovered, the separation and purification from its matrix are painstaking. These have limited its characterization, derivatization, and biomedical application. In this study, we developed chromatographic and distillation methods to enhance the purity and synthesis of G-T3 derivatives. Exactly 8% ethyl acetate (EA) in hexanes used in TLC resulted in right spots separation. Two gradient column chromatographic methods were examined using solvent mixtures of EA/hexanes and EA/petroleum ether (PE), respectively. We verified that a gradient elution with EA in PE led to the maximum purity (≥95%) based on the NMR and GC-MS outcomes. Also, G-T3 was stable in an emulsion to some extent, and some soluble G-T3 derivatives were synthesized, and their structure was confirmed
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Bhatkhande, Prajakta S. "Small Molecule Biomarkers Resulting from Radiation and Oxidative Damage to DNA." University of Toledo / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1470222983.
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Rigali, Mark Joseph 1963. "Chemical characterization of solid graphitic carbonaceous matter associated with the Oklo natural fission reactors and uranium ore deposits, Gabon (West Africa)." Diss., The University of Arizona, 1997. http://hdl.handle.net/10150/288812.
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Solid graphitic carbonaceous matter (CM) is closely associated with the Oklo uranium ore deposits and several of the natural fission reactors in Gabon, West Africa. This material facilitated the containment of uranium and numerous fissiogenic isotopes in these natural reactors for a period of nearly 2 Ga. Hence it is the subject of detailed studies because it may be useful as an analogue for carbonaceous materials, e.g. technical bitumens, that are currently being considered for the encapsulation and storage of anthropogenic radioactive waste. Chemical and structural analyses of the uraniferous CM associated with the natural fission reactors indicate that it is a polymer-like solid composed mainly of polycyclic aromatic hydrocarbons (PAHs) that are randomly oriented (turbostratic) and vary in size from several to several tens of A. Short-chained aliphatic hydrocarbons and oxygen-bearing moieties are attached to the PAH sheets and frequently bridge adjacent sheets. The Oklo uraniferous CM exhibits very high free radical concentrations, which can exceed 1021 free radicals/g organic carbon. The organic free radicals are stable PAH moieties located at or very near the surfaces of these organic solids, mainly on the internal surfaces of pores. Despite their presence, these pores could not have served as effective conduits for the transport of radionuclides by aqueous solutions through and out of the CM matrix. This is because of the very small average size of the pores, together with the CM's non-wettability by aqueous solutions. The Oklo CM has endured oxidation-reduction reactions during uranium mineralization, exposure to ionizing radiation, and alteration associated with the radiolysis products of water during and after natural reactor operation, perhaps up until the present time. Still, the CM acted as an effective barrier to radionuclide migration out of the CM-rich natural fission reactors. Properties, including its aromatic composition, resistance to alteration by ionizing radiation, and its non-wettability to aqueous solutions, make the Oklo uraniferous CM an effective barrier to radionuclide migration. These properties should be incorporated into man-made carbonaceous materials currently being considered for use in the storage of radioactive waste.
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Robb, Graeme R. "The microwave effect : non-thermal effects of microwave radiation in solid state chemistry." Thesis, University of Edinburgh, 2005. http://hdl.handle.net/1842/11895.
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Microwaves are commonly used for a number of solid state reactions, including sintering of ceramics, drying of materials and ionic substitution reactions. It is for such solid state processes that some of the most interesting effects are observed; yet these are presently amongst the most poorly understood. Diffraction is arguably the most incisive technique for the probing of solid state processes. To observe specific effects of microwave radiation it is necessary to perform in-situ diffraction experiments. Here we detail microwave applicators, modified for such a purpose. Simple phenomena, such as thermal expansion and phase transitions were observed for diverse materials (aspirin, silver iodide, β-alumina and barium titanate) under the influence of microwave heating. Furthermore, the use of w-situ diffraction as a method of temperature measurement is investigated. Some of these materials show unexpected effects when heated with microwaves, including anomalously large thermal expansion, the lowering of the phase transition temperature and a reduction in atomic displacement parameters. A consistent model has been proposed to explain these effects in terms of interactions of the electric field with a low-energy transverse optic phonon mode. The model only applies to materials possessing such a mode and no anomalous effects are observed otherwise. Barium titanate is a seemingly more complicated material and a strong electron-phonon interaction, resulting in local ordering may account for further anomalies. Another application of microwaves is the synthesis of nanoparticles using a microwave-induced plasma. This is an established technique, yet its application is limited to species with a volatile precursor. Here we extend the technique and design apparatus for use with a precursor in an aerosol, allowing the use of non-volatile, cheap precursor compounds.
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Boucly, Anthony. "Catalytical reactions and environmental chemistry modifications as seen by synchrotron radiation NAP-XPS." Thesis, Paris 6, 2017. http://www.theses.fr/2017PA066237/document.
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La NAP-XPS est un nouvel outil révolutionnaire permettant d'utiliser les avantages d'une analyse XPS (Sensibilité aux différents éléments chimiques ainsi que leurs états) à une pression proche de l'ambiante (de l'ordre du mbar) ouvrant ainsi la voie aux études in situ en se rapprochant des conditions réels et. Deux domaines profitent de cette nouvelle machine : la chimie environnementale et la catalyse. Dans le domaine de la chimie environnementale je m'intéresse à l'étude de l'hydratation des argiles dites gonflantes. J'ai ici démontré qu'il est effectivement possible de suivre l'hydratation des contre-ions en mettant en évidence différents comportement en fonction de leurs natures. De plus j'ai pu mettre en évidence un phénomène de radiolyse sous faisceau de la pyridine en présence d'eau dans ces milieux confinés. Concernant la catalyse, j'ai étudié l'oxydation du CO sur des nanocatalyseurs composés notamment de platine un excellent catalyseur, mais sensible aux problèmes d'empoisonnement au CO. Cette réaction est pour nous une réaction prototype permettant de tester le comportement des nanocatalyseurs (Pt, Zn et PtZn). J'ai pu déterminer la température de début de la réaction d'oxidation du CO, de plus en ajoutant du zinc au platine et pour former un nanocatalyseur bimétallique, j'ai démontré qu'on améliore sa résistance à l'oxidation et il montré que le zinc seul est lui aussi capable de catalyser l'oxidation du CO sous forme de création/destruction de carbonateThe NAP-XPS is a revolutionary new tool that makes possible to use the advantages of a standard XPS analysis (sensitivity to the different chemical elements as well as their states) at a near-ambient pressure (mbar range) thus enabling in situ studies closer to real conditions. Two fields fully benefit from this new machine: environmental chemistry and catalysis. In our case for the field of environmental chemistry we are interested in studying the hydration of so-called swelling clays. I have here demonstrated that it is indeed possible to follow the hydration of counter-ions and highlighted different behavior according to their natures. Moreover, I have been able to demonstrate a beam induced pyridine photolysis phenomenon in the presence of water in these confined media. Concerning catalysis, I studied the oxidation of CO on nanocatalysts composed in particular of platinum an excellent catalyst but sensitive to the CO poisoning. This reaction is for us a prototypical reaction to test the behavior of Pt, Zn, PtZn nanocatalysts. Here, I have been able to determine the onset temperature of the CO oxidation reaction. Moreover, by adding zinc to platinum and forming a bimetallic nanocatalyst, I have improved its resistance to oxidation and proved that zinc alone is also capable of catalyzing the oxidation of CO in the form of creation / destruction of carbonate
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Björkbacka, Åsa. "Radiation induced corrosion of copper." Thesis, KTH, Skolan för kemivetenskap (CHE), 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-33335.
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The Swedish concept for storage of highly radioactive spent nuclear fuel is called the KBS-3 program. The proposed procedure is that the waste will be stored in a deep repository, 500 meters down in the Swedish bedrock, for 100 000 years. The fuel will be sealed inside cast iron cylinders surrounded by copper. The iron-copper canisters will then be placed one by one in holes and embedded in bentonite clay. The environment in the deep repository will be that of an underground rock cave, there will be groundwater and low amounts of oxygen present. Substances which are likely to react with the copper canister and cause corrosion are oxygen, sulphides and reactive water radiolysis products. Gamma radiation from the spent nuclear fuel will penetrate through the canister and further into the bentonite clay. When the gamma radiation comes in contact with the water in the bentonite clay, water radiolysis will occur. Corrosive radiolysis products are for example hydroxyl radicals, solvated electrons and hydrogen peroxide. The main purpose of this work was to study the effect of gamma radiation on copper pieces, in an aqueous environment, both under oxic and anoxic conditions. The surfaces of the copper pieces were characterized using scanning electron microscopy (SEM) and infrared absorption spectroscopy (IRAS). The dissolution of copper was measured using inductively coupled plasma spectroscopy (ICP). A second study was also performed where the reactions of three different oxidants; hydrogen peroxide, permanganate and iridium hexachloride, were studied in the presence of copper in an inert environment. All of the reactions were studied spectrophotometrically and the dissolution of copper was measured using inductively coupled plasma spectroscopy (ICP). The SEM measurements showed corrosion products on the irradiated copper pieces both under oxic and anoxic conditions. Under anoxic conditions the corrosion products had a center of a small cavity which was surrounded by a larger, flat, circular area. From that area, wider cavities were spreading out in apparently random directions. SEM-EDS measurements detected oxygen on the surface of the corrosion products. ICP measurements of the water phase showed that the water from irradiated samples contained higher levels of copper than unirradiated samples. ICP measurements from the reactions of copper in the presence of oxidants showed that copper was only dissolved in the presence of iridium hexachloride. These results show that gamma radiation causes corrosion of copper in an aqueous environment, both under oxic and anoxic conditions. It can also be concluded that hydrogen peroxide is not the radiolysis product that causes the dissolution of copper when copper is irradiated in an aqueous and inert environment.
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Scholes, Mahala Louise. "Radiolysis of DNA related compounds in aqueous solution." Thesis, Brunel University, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.291089.
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Armatas, Nathan Gabriel. "Molybdophosphonate clusters as building blocks in the oxomolybdate-organodiphosphonate/M(II)-organoamine system structural influences of secondary metal, organoamine, and diphosphonate tether length (M=copper, nickel, cobalt) /." Related electronic resource: Current Research at SU : database of SU dissertations, recent titles available full text, 2009. http://wwwlib.umi.com/cr/syr/main.
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Sargent, Sara. "Radiation Shielding Bricks for Mars Using Martian Regolith Simulant and Hydrogen-Rich Polymers." W&M ScholarWorks, 2018. https://scholarworks.wm.edu/etd/1550153774.
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Radiation shielding materials are an essential component of long-term space travel and habitation. The mission to Mars will require a radiation shielding material that can be produced on Mars through energy and cost-efficient means. in this study, Martian regolith simulant and hydrogen-rich polymers are used to create a radiation shielding material in the form of bricks. The bricks are capable of shielding against galactic cosmic radiation on Mars. There are three methods in which the bricks were formed: 1) a heated press, 2) a microwave oven in a CO2 atmosphere, and 3) a vacuum oven with a low CO2 pressure. Each brick varies by the type of polymer, percent of polymer, and the method in which it was made. Flexural tests were conducted on the bricks to determine the flexural strength, flexural strain, and modulus of elasticity. OLTARIS was used to estimate the effectiveness of these bricks to shield against GCR on the Martian surface.
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Holmboe, Michael. "The Bentonite Barrier : Microstructural properties and the influence of γ-radiation." Doctoral thesis, KTH, Kärnkemi, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-34048.
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Garcia-Macias, Gustavo Adolfo. "Molecular photoionisation using synchrotron radiation : photoelectron photoion coincidence and circular dichroism." Thesis, University of Nottingham, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.251988.
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Herron, Maura Ethna. "In-situ studies of electrode surfaces using synchrotron X-ray radiation." Thesis, University of Southampton, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.316425.
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Yeh, Ka-Lo. "The generation of high field terahertz radiation and its application in terahertz nonlinear spectroscopy." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/49748.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 2009.Includes bibliographical references (p. 147-155).
In this thesis research, I implemented a terahertz generation scheme that enables high-field near-single-cycle terahertz (THz) pulse generation via optical rectification in a LiNbO3 (LN) crystal. I also developed a method for the non reconfigurable generation of high-intensity multiple-cycle THz fields aimed to more efficiently deliver THz energy to resonant samples. A novel free-space THz-pump/THz-probe setup enabled time-resolved measurement of ultrafast nonlinear electronic responses in doped bulk semiconductor samples. The ability to spectrally and temporally resolve the response of the semiconductor sample using a THz probe allowed us to uncover both the dynamics of impact ionization and interesting phonon-plasma interactions in indium antimonide (InSb) for the first time. Nonlinear vibrational responses in LN were ob-served first in a dual THz beam setup on an integrated LN waveguide platform with optical probing to reveal the generation of terahertz second harmonic signals and also in THz transmission measurements in cooled LN where THz intensity-dependent self-phase modulation and harmonic generation were observed. An outlook and preliminary results toward implementation and observation of high-field THz-driven responses in ferroelectric materials are given in the final chapter of this thesis.
by Ka-Lo Yeh.
Ph.D.
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Safi, Ismael. "Radiation Effects on KBS-3 Barriers: SKB’s work so far." Thesis, KTH, Skolan för kemivetenskap (CHE), 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-221172.
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In the Swedish concept for final disposal of spent nuclear fuel, referred to as KBS-3, a three-layered protection system is used. The system consists of a copper canister holding the spent nuclear fuel deposited 500 meters in a repository built in groundwater saturated granitic rock. The copper canisters are placed in deposition holes, buffered and backfilled by bentonite clay. One of the challenges associated with this system is the long-term exposure of the engineered barriers i.e. the canister including the spent fuel and the cast iron insert as well as the bentonite buffer to ionizing radiation. The possible effects of radiation on the materials in the engineered barriers have been studied not only by the Swedish Nuclear Fuel and Waste Co (SKB), but also by academia nationally and internationally. In this work, literature studies have been carried out to investigate whether all possible/potential effects of ionizing radiation from the spent nuclear fuel on the engineered barriers have been considered by SKB. Apart from a general summary of the relevant issues in chapter one, regions within the KBS-3 design where enhanced radiation may occur have been identified and the related radiation induced processes have been summarized in chapter two. These issues include effects of water-radiolysis on the spent fuel, the cast-iron insert and other ferrous materials, the copper shell and the bentonite buffer. Three types of possible damages have been identified: the microstructural defects in the ferrous materials by direct radiation, the radiation-induced microstructural alterations of the spent fuel and the bentonite and radiation-induced oxidation i.e. dissolution of the fuel and corrosion of the ferrous metals and the copper. The relevant SKB documents have been identified (in chapter 3) to be the SR-Site main report, the underlying Process reports and reports of FUD-programs. Apart from these documents, other SKB technical reports and open literature are used as basis for assessing whether all the issues mentioned in chapter two of this study have been considered by SKB. According to the assessment, most of the significant issues mentioned in chapter two have been mentioned and discussed in the identified SKB documents. In the main safety assessment, i.e. the SR-Site project, the significance of most of the radiation processes has been based on dose levels expected at the different regions within the KBS-3 design. Irrespective of the assessments in SR-Site though, the current understanding of the relevant issues and plans for future research efforts summarized in FUD-programs reflect the research developments. However, the recent developments in understanding of radiation-induced effects on montmorillonite and the corrosion of copper in argon atmosphere need to be given due importance in coming FUD-programs. A separate investigation of radiation effects on FSW-joints may contribute to removal of the remaining uncertainties. In addition, mechanism involved in radiation-induced fuel dissolution and copper corrosion may require more research efforts than those planned.Det svenska konceptet för slutförvar av använt kärnbränsle, KBS-3, består av tre barriärer som är tänkt att skydda omgivningen mot joniserande strålning från använt kärnbränsle. Systemet består av specialtillverkade kopparkapslar som innehåller det använda kärnbränslet. Kapslarna förvaras i deponeringshål 500 meter ner i berggrunden och är inneslutna i bentonitlera. En av frågeställningarna associerade med djupt geologiskt förvar av kärnbränsle är hur de konstruerade barriärna, alltså kopparhöljen som omsluter gjutjärninsatsen och det använda kärnbränslet samt bentonitleran, kan påverkas av joniserande strålning från det använda kärnbränslet. Möjliga strålningseffekter på de skyddande barriärna har studerats nationellt och internationellt. Syftet med denna studie var att utvärdera huruvida SKB har i sina säkerhetsanalyser av slutförvaret tagit tillräcklig hänsyn till effekter av joniserande strålning på de konstruerade barriärna. Studien består av tre kapitel där kapitel 1 utgör en generell sammanfattning av frågeställningar kopplade till KBS-3 barriärer. I kapitel 2 har områden i och omkring de konstruerade barriärna där joniserande strålning från använt kärnbränsle kan förekomma identifierats och möjliga strålningsinducerade processer i dessa områden sammanfattats. Tre typer av möjliga strålningsinducerade skador har identifierats: 1) strålningsinducerade mikrostrukturella defekter i metaller som förekommer i systemet, 2) strålningsinducerade mikrostrukturella förändringar i använt kärnbränsle och i bentonitleran samt 3) strålningsinducerad oxidation, dvs. upplösning av det använda kärnbränslet och korrosion av metaller som förekommer i systemet. SKB-dokumenten som identifierats (i kapital 3) som relevanta för utvärderingen i denna studie är följande: Säkerhetsanalysen (SR-Site), tekniska rapporter som ligger till grund för SR-Site och FUD-programmen. Enligt bedömningen i denna studie har SKB tagit hänsyn till de flesta relevanta frågeställningarna kopplade till strålningsinducerade effekterna på de konstruerade barriärna. I SR-Site har de flesta bedömningar relaterade till och om signifikansen hos de strålningsinducerade processerna baserats på doser och dosrater som förväntas förekomma i och omkring de konstruerade barriärna. Oavsett bedömningarna i SR-Site har dock de mest relevanta frågeställningarna tagits upp i FUD-programmen och framtida forskningsinsatser i enlighet med det som av SKB har uttryckts som behov av en utökad processförståelse. Dessa frågeställningar reflekterar väl de mest signifikanta utvecklingarna som rapporterats i öppna vetenskapliga studier om strålningsinducerade processer som kan förekomma i ett djupt geologiskt förvar för använt kärnbränsle. De senaste rapporterade observationerna om strålningseffekter på montmorillonit och kopperkorrosion i argonatmosfär måste dock tas upp och diskuteras i de kommande FUD-programmen. Separata studier av strålningseffekter på koppardelar som har behandlats med FSW-teknik rekommenderas. För att uppnå en bättre och djupare förståelse för de förekommande mekanismerna i strålningsinducerad upplösning av använt kärnbränsle krävs sannolikt mera forskningsinsatser än de planerade.
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OLIVEIRA, ANA C. S. "Avaliação dos efeitos da radiação gama nas características físico-químicas de KIWI (Actinidia deliciosa)cv. Hayward minimamente processado." reponame:Repositório Institucional do IPEN, 2011. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10045.
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Made available in DSpace on 2014-10-09T12:34:09Z (GMT). No. of bitstreams: 0Made available in DSpace on 2014-10-09T14:06:44Z (GMT). No. of bitstreams: 0
Dissertação (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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Hopkins, John Dawson. "Structural studies of mixed metal oxides by neutron diffraction and synchrotron radiation." Thesis, Keele University, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.321701.
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Yang, Sha. "Synthesis and Characterization of Hydrogen-Rich Polyimide Materials for Radiation Shielding." W&M ScholarWorks, 2005. https://scholarworks.wm.edu/etd/1539626841.
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Lundström, Tim. "Radiation chemistry of aqueous solutions related to nuclear reactor systems and spent fuel management /." Linköping : Univ, 2003. http://www.bibl.liu.se/liupubl/disp/disp2003/tek840s.pdf.
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Fraser, Wesley T. "Evaluation of spore wall chemistry as a novel biochemical proxy for UV-B radiation." Thesis, Open University, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.494651.
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The stratospheric ozone layer provides protection for Earth's land-based organisms against harmful ultraviolet (UV) radiation, but the past century has seen the ozone layer compromised as a result of human activity, resulting in commensurate shifts in surface UV-B flux. Despite the importance of UV radiation to the well-being of life, records of surface UV-B flux only exist for a short period of time. In order to gain a deeper understanding of the behaviour of ozone and UV-B flux in the past an alternative method of determining UV-B is required. Changes in spore chemistry have been proposed as a palaeo-monitor of UV-B flux, which can then be related to stratospheric ozone abundance. By employing the rapid and inexpensive technique of FTIR microspectroscopy to investigate changes in spore chemistry, a large dataset spanning seven different spatial and temporal UV regimes has been generated in order to evaluate the feasibility of routine usage of a spore-based UV-B proxy.
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Leonard, Simon. "Solid-state structural chemistry at high pressure using X-ray synchrotron radiation diffraction techniques." Thesis, University of Leicester, 1990. http://hdl.handle.net/2381/33783.
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Energy dispersive X-ray diffraction with synchrotron radiation has been used to probe the room temperature, high pressure phase diagrams of several inorganic compounds. A review of the publications for high pressure X-ray diffraction at synchrotron sources is given. The techniques, theory, apparatus and errors of high pressure X-ray diffraction are discussed. A spectroscopic system used to enable pressure calibration is refined and its merits discussed. The calibration of this instrument against an NaC1 standard is presented. CuGeO3 undergoes two phase transitions at 73 kbar and 110 kbar respectively. The effect of pressure on the Jahn-Teller distortion around copper is discussed. The first high pressure polymorph of hafnia (beginning at 26 kbar) is shown to be iso-structural with that of zirconia. A mechanism for the transition is offered. The effect of pressure on the series of iso-structural vanadates MVO3 (M = K, Rb, Cs, NH4) reveals phase transitions in KVO3 and RbVO3 at 27 and 40 kbar respectively. Models for the transitions are offered. Intuitive expectations of an increase in compressibilities with an increase in cation size are not realised. NH4VO3 transforms to an amorphous phase at 47 kbar. A full structural model for (COD)PtNPhS(O)2NPh is offered with an R- factor of 2.54%. A discussion of ring-puckering in this and similar systems is given. An improved structural model for powdered hafnia is offered. High resolution synchrotron techniques are used in combination with Rietveld refinement methods. A discussion of the structure is given.
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Cheng, Anchi. "Kinetics and mechanism of lipid mesophase structural changes induced by pressure and X-radiation damage /." The Ohio State University, 1995. http://rave.ohiolink.edu/etdc/view?acc_num=osu148786179681917.
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Pugh, Christopher Scott. "Fabrications and Characterizations of Boron Containing Polyimides for Radiation Shielding." W&M ScholarWorks, 1999. https://scholarworks.wm.edu/etd/1539626217.
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Sheridan, Kevin Thomas. "Experimental techniques for cold chemistry and molecular spectroscopy in an ion trap." Thesis, University of Sussex, 2013. http://sro.sussex.ac.uk/id/eprint/47145/.
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A range of experimental techniques for application in reaction studies between ionic and neutral atoms/molecules and high resolution spectroscopy experiments with sympathetically cooled molecular ions are presented. A novel ion trap loading scheme using the photo-ionisation of atoms generated by the pulsed laser ablation of a solid calcium target has been characterised. We have identified the range of ablation laser fluences that must be used in order to produce a flux of neutral calcium atoms, which is a prerequisite for isotope selective ion trap loading. Calcium ions are trapped and laser cooled in a linear radio-frequency ion trap. We have developed a spectroscopy scheme that allows the entire fluorescence spectrum of trapped ions to be rapidly collected with high precision while maintaining a low ion temperature and good ion localisation throughout interrogation. The scheme has been demonstrated by measuring the saturation intensity of the calcium ion 4S1/2→4P1/2 transition. We have developed a novel scheme to measure the secular motion of trapped ions and demonstrated the application of the technique to ion-neutral collision reaction experiments. Employing pulsed excitation and Doppler velocimetry, we have measured the centre-of-mass mode frequency of single ions as well as large ion crystals with a frequency precision better than 2x10-3 within an interrogation time on the order of seconds. This method has been used to measure the mass of ions and observe charge exchange collisions between trapped calcium isotopes. In particular, we have measured the 44Ca++40Ca!40Ca++44Ca reaction cross section and demonstrated the single-event resolution of the technique. Finally, we have developed a novel all-optical broadband scheme for exciting, amplifying and measuring the secular motion of ions in the trap. Oscillation induced by optical excitation has been coherently amplified to control and measure the ion's secular motion. Requiring only a single interrogation laser, the ion's oscillation amplitude can be precisely controlled. The application of this technique to non-destructive spectroscopy of trapped molecular ions is discussed.
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Roth, Olivia. "Redox Chemistry in Radiation Induced Dissolution of Spent Nuclear Fuel : from Elementary Reactions to Predictive Modeling." Doctoral thesis, KTH, Kärnkemi, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4901.
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The focus of this doctoral thesis is the redox chemistry involved in radiation induced oxidative dissolution of spent nuclear fuel and UO2 (as a model substance for spent nuclear fuel). It is shown that two electron oxidants are more efficient than one electron oxidants in oxidative dissolution of UO2 at low oxidant concentrations. Furthermore, it is shown that H2O2 is the only oxidant that has to be taken into account in radiation induced dissolution of UO2 under deep repository conditions (granite groundwater dominated by α-radiolysis). Previously determined rate constants for oxidation of UO2 by H2O2 and O2, and rate constants for dissolution of U(VI) from the surface are successfully used to reproduce numerous UO2 dissolution rates reported in the literature. The impact of reactive solutes (Fe(II)(aq), 2-propanol and chloride) and Pd-inclusions (as a model for ε-particles) in combination with H2, on radiation induced oxidative dissolution of UO2 is investigated. It is shown that both the studied reactive solutes (under oxygen free conditions) and the combination of Pd inclusions and H2 inhibit the dissolution. Calculations (based on the fuel inventory) show that 1 µM Fe(II)(aq) decreases the dissolution rate by a factor of ~50 and that 1 ppm surface coverage of ε-particles is sufficient to completely stop the dissolution of 100 year old fuel (assuming 40 bar H2).The dissolution behavior of NpO2 and PuO2 in H2O2 containing aqueous solution without complexing agent is studied and compared to UO2. Based on the measured dissolution rates, we would not expect the dissolution of the actinides to be congruent. Instead, in a system without complexing agent, the rates Np and Pu are expected to be lower than the U release rate. The effect of ionizing irradiation on the UO2 reactivity is studied in order to elucidate the effect of self-irradiation on the reactivity of the spent fuel matrix. It is shown that a threshold dose must be achieved before any effect of irradiation can be seen. Beyond the threshold the reactivity seems to increase with increasing dose. Furthermore, the effect appears to be permanent. The effect of particle size on the reactivity of UO2 powder is studied in view of proposed theories suggesting a particle size dependence of both the pre-exponential factor and the activation energy for redox reactions. The rate constant and activation energy for oxidation of UO2 by MnO4- seems to agree with the proposed equations. The radiation chemical synthesis of UO2 nanoparticles is studied. It is shown that U(VI) released by dissolution of spent nuclear fuel could be reduced to UO2 nanoparticles.These particles could, due to their high reactivity towards H2O2, act as oxidant scavenger in a future deep repository for spent nuclear fuel.Denna doktorsavhandling behandlar redoxprocesser involverade i strålningsinducerad oxidativ upplösning av använt kärnbränsle och UO2 (som modellsubstans för använt kärnbränsle).Detta arbete visar att två-elektron oxidanter är mer effektiva än en-elektron oxidanter i oxidativ upplösning av UO2 vid låga oxidantkoncentrationer. Dessutom visas, på kinetiska grunder,att H2O2 är den enda oxidant som måste tas hänsyn till vid stålningsinducerad oxidativ upplösning av UO2 under djupförvarsförhållanden (granitiskt grundvatten dominerat av α-radiolys). Tidigare bestämda hastighetskonstanter för oxidation av UO2 med H2O2 och O2, samt hastighetskonstanter för upplösning av U(VI) från ytan har framgångrikt använts för att återskapa UO2 upplösningshastigheter rapporterade i litteraturen. Inverkan av reaktiva ämnen i vattenfas (Fe(II)(aq), 2-propanol och klorid) samt av Pd-inneslutningar (som modell av ε-partiklar) i UO2 matrisen i kombination med H2, på strålningsinducerad upplösning av UO2 har studerats. Studien visar att både de reaktiva ämnena i vattenfasen (under syrefria förhållanden) och Pd- inneslutningar i kombination med H2 hämmar upplösningen. Beräkningar (baserade på ett bränsleinventarie) visar att 1 µM Fe(II)(aq) minskar upplösningshastigheten med en faktor ~50 samt att 1 ppm ytbeläggning av ε-partiklar är tillräckligt för att effektivt stoppa uppslöningen av 100 år gammalt bränsle (vid 40 bar H2).Upplösning av NpO2 och PuO2, i jämförelse med UO2,har studerats i vattenlösning innehållande H2O2 utan komplexbildare. Baserat på de uppmätta upplösningshastigheterna förväntas upplösningen av dessa aktinider från UO2-bränsle vara inkongruent. I ett system utan komplexbildare kan NpO2 odh PuO2 upplösningshastighetern förvantas vara lägre än UO2 upplösningshastigheten. Effekten av joniserande strålning på reaktiviteten hos UO2 har studerats för att klargöra effekten av egen-bestrålning. Studien visar att dosen måste nå ett visst tröskelvärde innan någon effekt på reaktiviteten kan observeras. Vid doser över tröskelvärdet ökar reaktiviteten med ökande dos. Effekten verkar vara permanent. Partikelstorlekens inverkan på reaktiviteten hos UO2 pulver har studerats med utgångspunkt i föreslagna samband mellan partikelstorlek och pre-exponentiell faktor och mellan partikelstorlek och aktiveringsenergi. Studien visar att hastighetskonstanten och aktiveringsenergin för reaktionen mellan UO2 och MnO4- överenstämmer med de föreslagna sambanden. Stålningskemisk syntes av UO2 nanopartiklar har studerats. Studien visar att U(VI) frigjort genom upplösning av använt kärnbränsle i ett djupförvar kan reduceras till UO2 nanopartiklar. Dessa partiklar kan, på grund av sin höga reaktivitet med H2O2, fungera som infångare av oxidanter i ett framtida djupförvar för använt kärnbränsle.
QC 20100908
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Beaton, Christa. "Photo-protection mechanisms of UV stabilizers on milled wood lignin." Thesis, McGill University, 2000. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=32897.
Full textAbstract:
This study focuses on understanding the photochemical reactions that occur between ultraviolet stabilizers and lignin during irradiation in order to further comprehend the photo-protection mechanisms of these stabilizers during brightness reversion. The stabilizers chosen for study included a variety of ultraviolet absorbers (UVAs), in addition to a hindered nitroxide free radical (4-hydroxy-TEMPO). Irradiated samples were analyzed using quantitative 31P NMR, in addition to a technique known as 'Derivatization Followed by Reductive Cleavage'.Benzophenone-based UVAs have been shown to be actively involved in photochemical reactions with lignin during irradiation, while benzotriazole-based UVAs are comparatively photostable under identical irradiation techniques. All additive combinations were found to inhibit the formation of carboxylic acids and photochemical condensation reactions in lignin; however, the joint application of 2,4-DHB and 4-hydroxy-TEMPO demonstrated synergistic inhibition of these reactions.
All additive combinations were shown to impede the formation of catechol structures and to retard the cleavage of lignin beta-arylether groups during irradiation. The combined use of Tinuvin 1130 and 4-hydroxy-TEMPO provided the most efficient inhibition of these reactions. These results provide insight into the excellent photoyellowing inhibition provided by this additive combination when applied onto mechanical pulps.