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Dissertations / Theses on the topic 'Radiation studies'

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Published: 6 September 2023
Last updated: 7 September 2023

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1

Sotthibandhu, Sakuntala. "Radiation damage studies of silicon detectors." Thesis, Imperial College London, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.339072.

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2

Langley, Ruth E. "Radiation-induced apoptosis : in vitro studies." Thesis, University of Nottingham, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.387684.

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3

Krishnamurthy, Satheesh. "Synchrotron radiation studies of nanostructured materials." Thesis, University of Newcastle Upon Tyne, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.430334.

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4

Paris, Mark V. "Model studies of solar spectral irradiance at the bottom and top of a cloudy atmosphere." Diss., Georgia Institute of Technology, 1985. http://hdl.handle.net/1853/16900.

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5

La, Rosa Francesco. "Studies on ToF-PET using Cherenkov radiation." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2015. http://amslaurea.unibo.it/9543/.

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La tomografia ad emissione di positroni (PET) è una tecnica di imaging di medicina nucleare, utilizzata oggi diffusamente in ambito clinico. Essa fornisce immagini e informazioni fisiologiche dei processi funzionali all’interno del corpo. La PET si basa sulla rilevazione di fotoni di annichilazione prodotti in seguito al decadimento di un radio farmaco iniettato nel paziente. I rilevatori convenzionali sono costituiti da un materiale scintillatore accoppiato ad un fotomoltiplicatore, solitamente un PMT o SiPM. Uno sviluppo della PET è la Time of Flight PET (ToF PET), attualmente già in commercio ed utilizzata con prestazioni eccellenti. Un’ulteriore modifica, che potenzialmente permetterebbe di ottenere una migliore risoluzione temporale, è la ToF PET basata sulla rilevazione di fotoni tramite radiazione Cherenkov, invece che luce di scintillazione. Questo lavoro di tesi è incentrato dunque su questa tecnica specifica. Si illustra una rassegna di pubblicazioni scientifiche degli ultimi anni riguardo ad essa con i relativi risultati ottenuti e i possibili sviluppi futuri. Infine si propone un approfondimento personale, nel quale, tramite un programma scritto in ROOT, si è realizzata una geometria di un sistema di rilevazione ToF PET. Esso prevede la rilevazione dei fotoni di annichilazione tramite un radiatore Cherenkov accoppiato ad un SiPM. In futuro questo potrà essere implementato e utilizzato per simulare il processo fisico della PET, verificando la validità e le prestazioni del sistema così sviluppato.
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6

Weaver, Jill Suzanne. "Synchrotron Radiation Studies of Magnetic Thin Films." Thesis, University of York, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.485147.

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The purpose of these studies has been to gain a better understanding of the relationships that govern the interfaces of ferromagnetic / ill-V semiconductor heterostructures and other materials. The results here in are expected to promote the development of next generation spin electronic devices which may open the way toward incorporating data processing and storage in a single device through the utilisation of both electron charge and spin. Development ofsuch devices relies a great deal on the quality ofinterface which can be set up between the semiconductor and ferromagnetic structures, as a poor interface leads to difficulty in carrier transport between the materials. Studies into interface magnetism, which can most effectively be carried out using the synchrotron technique of x-ray magnetic circular dichroism (XMCD), have been used to make substantial strides forward in the understanding of the importance of interface quality. It is hoped that these shidies involving synchrotron radiation, predominantly in the area of XMCD, wiJI help the further development ofnew spintronic technologies.
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7

Gray, D. E. "Studies of radiation in cloudy atmosphere£s." Thesis, University of Oxford, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.379984.

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8

Al-Hakim, M. M. R. "Radiation chemical and spectroscopic studies of lipoxygenase." Thesis, University of Salford, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.372141.

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9

Thompson, Stephen P. "Studies of cosmic dusts using synchrotron radiation." Thesis, Keele University, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.303876.

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10

Wright, Andrew Edward. "Studies of reactive intermediates with synchrotron radiation." Thesis, University of Southampton, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.242644.

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11

Martis, V. "Synchrotron radiation studies of multicomponent metal oxides." Thesis, University College London (University of London), 2012. http://discovery.ucl.ac.uk/1388216/.

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The work described in this thesis is focused on the development of characterization methods for determining the structure of multicomponent metal oxides using synchrotron radiation techniques, in particular, X-ray Absorption Fine Structure (XAFS) and Energy Resolved Electron Yield X-ray Absorption Spectroscopy (EREY– XAS). XAFS is a superior technique for determining the local structure of, for example, transition metals that are used as dopants in very low concentrations. It also provides information on early stages of crystallization processes before a material develops sufficient long range order. Energy resolved XAS was developed as an alternative to conventional transmission and fluorescence techniques which probe mainly the bulk of materials. This techniques yield information about the local structure from the near surface region of materials. The other complementary techniques used for characterization of materials were XRD, Raman spectroscopy, X-ray Photoelectron Spectroscopy (XPS) and Scanning Electron Microscopy (SEM). New insights about formation of Bi2MoO6 crystallites from an amorphous gel below 200oC were obtained with a novel in situ setup, in which XAFS and XRD was combined with RAMAN spectroscopy in a single experiment. Combined XRD/XAFS technique was used for determining the growth mechanism of Bi2MoO6 formed under hydrothermal conditions from an amorphous gel. The reaction kinetics was quantified by using the Avrami-Erofe’ev formalism. The surface sensitive of EREY–XAS was performed on several materials in particular chromium doped Fe2O3 catalysts and cobalt substituted aluminophosphates such as CoAlPO-18 and CoAlPO-34. The sensitivity of technique was assessed by comparison with conventional XAS techniques and XPS. Finally, the interactions of a synchrotron X-ray beam with a sample were studied. In particular, the effects of exposure to a monochromatic 10 keV X-ray beam on thermally induced crystallization of lithium disilicate glass were investigated.
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12

Mulroy, Louise. "Pulsed radiation studies of photo-protective systems." Thesis, Keele University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.388948.

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13

Liu, Wenqing. "Synchrotron radiation studies of spintronic hybrid systems." Thesis, University of York, 2014. http://etheses.whiterose.ac.uk/8180/.

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Spintronics is an emergent interdisciplinary topic for the studies of spin-based, other than or in addition to charge-only-based physical phenomena, which promises not only new capabilities of electronic devices, but also abundant science. For applied materials, the spin ordering has long been investigated within the context of conventional ferromagnetic materials (FMs), while the study of spin generation, relaxation, and spin-orbit coupling (SOC) in semiconductors (SCs) took off only recently with the advent of spintronics and it is here that many novel materials and FM/SC hybrid structures can find their greatest potential in both science and technology. In the pursuit for such goals, the intrinsic material properties are important indicators and the artificially synthetized hybrid systems (layered FM/SC structures and FM-doped SCs) are valuable models for studying spindependent phenomena and could potentially be used as actual components for an eventual spintronic device. These results are expected to contribute to some of the most fundamental questions of the contemporary spintronic materials research, such as the FM/SC interfacial hybridization and magnetism, the spin and orbital ordering of ferrites, and the fundamental magnetism of doped TIs, and the proximity effects in FM/DMS and FM/doped TI heterostructures.
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14

Melero, García Emilio. "Fragmentation studies of small molecules using synchrotron radiation." Licentiate thesis, KTH, Physics, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-1697.

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This thesis presents experimental data on the fragmentationof gas phase sulfur hexafluoride (SF6) and deutheromethane(CD4) molecules after their interaction with synchrotronradiation in the energy range of 70-200 eV. The data wasobtained using coincidence spectroscopy between energy resolvedelectrons and ions (EREICO).

Degradation of the molecular bond upon selective ionizationof different molecular orbitals has been studied by measuringionic fragments in coincidence with energy selected electrons.Besides the direct ionisation of the orbitals also the indirectprocess, in which the hole is created by the decay of a highlyenergetic core-excited state, was studied. The differencesdetected in the fragmentation after the direct and indirectionisation of a selected orbital can be related, in some cases,with the relaxation of the nuclei in the potential energysurface of the core excited state during its lifetime, thusproviding information on the neutral core excited state.

An experimental set-up capable of photon inducedfluorescence spectroscopy (PIFs) studies of core excitedmolecules in the visible range has been constructed. Thistechnique can yield complementary information to the EREICOdata about the energy distribution in the fragmentation sincethe internal energy of excited emitted fragments that decay inthe visible can be measured. It also allows the detection ofpossible neutral fragments.

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15

Bao, Zhuo. "Synchrotron Radiation Studies of Free and Adsorbed Molecules." Doctoral thesis, Uppsala University, Surface and Interface Science Division, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-8610.

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This thesis contains two parts. The first part concerns the research work on free molecules using synchrotron-radiation-related techniques. Auger electron spectra of two free open-shell molecules, O2 and NO, were studied experimentally and theoretically. Photoionization experimental technique with tunable synchrotron radiation source was used to induce core-level electron ionization and obtain the KVV normal Auger electron spectra. A quantitative assignment of O2 normal Auger spectrum was obtained by applying ab initio CI calculations and LVI Auger line shape simulations including the bond length dependence of Auger transition rates. The photon energy dependence of normal Auger electron spectra was focused on with photon energies in the vicinities of core-ionization threshold energies. Consequently, the MAPCI (Molecular Auger Post Collision Interaction) theory was developed. Taking the near-threshold O2 normal Auger spectrum as an example, the two extreme cases of MAPCI effect, “atomic-like PCI” and “molecular PCI”, were discovered and discussed. The effect of shape resonance on near-threshold molecular normal Auger spectrum was discussed taking NO near threshold normal Auger spectra as example.

The second part deals with research work on the chemisorption of small epoxy organic molecules, ethylene oxide, methyl oxirane, on Si (100) surfaces. Synchrotron radiation related techniques, UPS, XPS and NEXAFS, were applied. Based on the valence photoemission spectra, C 1s and Si 2p XPS spectra, the epoxy ring opening reactions of these molecules in chemisorption process were proved. Further tentative search for the surface-adsorbate CDAD effect was performed, and no evident circular dichroism was confirmed.

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16

Walker, Christina Helen. "Monte Carlo radiation transfer studies of protoplanetary environments /." St Andrews, 2007. http://hdl.handle.net/10023/218.

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17

Robinson, P. T. "Magnetic resonance studies of radiation processes in quartz." Thesis, University of Oxford, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.355772.

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18

Walker, Christina H. "Monte Carlo radiation transfer studies of protoplanetary environments." Thesis, University of St Andrews, 2007. http://hdl.handle.net/10023/218.

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Monte Carlo radiation transfer provides an efficient modelling tool for probing the dusty local environment of young stars. Within this thesis, such theoretical models are used to study the disk structure of objects across the mass spectrum - young low mass Brown Dwarfs, solar mass T-Tauri stars, intermediate mass Herbig Ae stars, and candidate B-stars with massive disks. A Monte Carlo radiation transfer code is used to model images and photometric data in the UV - mm wavelength range. These models demonstrate how modelling techniques have been updated in an attempt to reduce the number of unknown parameters and extend the diversity of objects that can be studied.
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19

Hope, S. "Spin polarised radiation studies of ultrathin magnetic films." Thesis, University of Cambridge, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.604219.

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Two distinct spin polarised radiation techniques have been employed to determine the magnetic properties of ultrathin magnetic films in-situ and ex-situ. The magneto-optical Kerr effect has been used to study the evolution of the magnetic properties during room temperature growth of Co/Cu(110) in -situ. The thickness dependence of the magnetic moment per atom in the Cu/Ni/Cu/Si(001) system has been investigated ex-situ using polarised neutron reflection. The Co/Cu(110) system is found to exhibit a 3D growth mode, becoming ferromagnetic at a critical thickness of dc=4.6±1.1. ML. Remarkably, the magnetic susceptibility χ follows a power law near dc with a critical exponent γ=2.39±0.08, which is in excellent agreement with the theoretical value of γ=2.43 for a 2D percolation phase transition. STM measurements on the same crystal indicate that the percolation phase transition is related to the coalescence of Co island clusters across the entire sample area. For a given Co thickness in the range 5MLCo<40ML the magnetic easy axis is found to switch through 90° over a repeatable duration (of the order of one hour) dependent on the thickness of the Co film. The behaviour is attributed to the reversal in sign of the effective uniaxial anisotropy constant, due to the adsorption of submonolayer quantities of residual CO gas in the UHV chamber. The effect of the adsorbed CO gas can be reversed by the adsorption of submonolayer coverages of Cu overlayer thereby switching the easy axis back to its original direction. For thin Co films (dCo<15ML) the easy axis switches abruptly between the two directions. For thicker Co films (dCo>15ML) the magnetic easy axis can take up intermediate directions and allows us to controllably engineer the direction of easy magnetisation at a constant Co thickness. A phenomenological model is developed to explain the switching behaviour based on competing uniaxial and cubic anisotropies. Depositing Co, or annealing the sample to 400K will produce similar behaviour. The nature of the switching for each mechanism is discussed.
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20

Myles, Dean Aubrey Albert. "Synchrotron X-radiation studies of C-reactive proteins." Thesis, Keele University, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.305880.

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21

Morgan, Andrew Gordon. "Studies of final state photon radiation at LEP." Thesis, Durham University, 1994. http://etheses.dur.ac.uk/5952/.

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We consider two aspects of calculations involving the production of final state photons at LEP. The first addresses photons produced in association with hadrons. We motivate a measurement of the quark to photon fragmentation function and show how it can be used to account for isolated and non-isolated production rates. The second concerns the rare Z-decay to photons. We expose a subtle relationship between its various contributions. Following its investigation, we offer an improved method of calculation for weak processes at one loop.
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22

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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23

Bailet, Gilles. "Radiation and ablation studies for in-flight validation." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLC008.

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Dévoiler les mystères du système solaire pour comprendre les mécanismes de la formation de la Terre, pour rechercher des signes de vie ou pour développer des colonies sur d’autres planètes, dépend de notre capacité à repousser les limites de l'ingénierie et de la science. Pour cela, il est important de développer des technologies de pointe pour permettre aux véhicules spatiaux de survivre la phase d'entrée ou de rentrée atmosphérique. Lors de l’entrée ou de la rentrée, l’engin spatial peut être exposé à flux radiatifs intenses qui ne peuvent pas encore être prédits avec précision, imposant ainsi des marges de sécurité sur la conception des systèmes de protection thermique. Ces incertitudes augmentent lorsque le bouclier thermique est constitué d'un matériau ablatif car sa dégradation introduit de nouvelles espèces chimiques réagissant avec le plasma produit devant le véhicule, ce qui affecte le rayonnement. Le but de cette thèse est d’étudier les flux de chaleur radiatifs sur un véhicule de rentrée de petite taille en présence d’un bouclier ablatif (Thermal Protection System, ou TPS), en utilisant des simulations numériques et des expériences pour développer un instrument de vol qui sera embarqué à bord du CubeSat QARMAN.Une évaluation de la trajectoire de rentrée du véhicule QARMAN (masse : 5 kg) a été réalisée en utilisant un code maison à 6 degrés de liberté. Un ensemble de simulations Monte Carlo ont permis de quantifier les incertitudes et ont montré un maximum de ± 15% écart par rapport à la trajectoire nominale. Les spectres sans ablation ont alors été déterminés en utilisant une approche découplée avec deux codes : Stagline (VKI) et SPECAIR (EM2C, CentraleSupélec). Ces simulations ont été effectuées pour la trajectoire nominale ainsi que pour la gamme des incertitudes. Elles ont permis de mettre en évidence un comportement non-linéaire des caractéristiques spectrales par rapport aux valeurs nominales, avec une augmentation drastique vers la fin de la mission.Les effets de l'ablation ont été étudiés avec une nouvelle technique de mesure développée au cours de cette thèse. Basée sur deux sondes de mesure de rayonnement, l’une refroidie et l’autre recouverte d’un matériau ablatif, cette méthode permet de quantifier l'émission et l'absorption induite par tout type de TPS ayant des interactions gaz-surface avec l'écoulement, dans l’hypothèse que les raies d’émission et d’absorption des espèces ablatives ne soient pas superposées. La méthode a été validée sur un échantillon de graphite TPS. Elle a ensuite été appliquée à la prédiction du rayonnement attendu lors de la mission QARMAN (Cork P50 TPS). Cette étude a également permis de sélectionner un spectromètre d’émission adapté à la mission QARMAN et aux objectifs de la thèse (plage de 350 à 800 nm pour une masse de 68 g).Un instrument de mesure de rayonnement standard a été testé et les limites de cet appareil ont été établies. Deux nouvelles technologies ont été développées et la charge utile (spectromètre d’émission INES) a été construite et intégrée au véhicule QARMAN. Un étalonnage spectral et thermique dédié a également été développé pour maximiser la qualité du retour scientifique en prenant en compte les variations de température dans la baie de charge utile de QARMAN.L’instrument proposé est, à ce jour, la seule charge utile non intrusive capable d’effectuer des mesures radiatives sans limitations liées à la contamination par les poussières et gaz d'ablation. L’instrument peut aussi fournir des mesures de la récession, de la sublimation et du gonflement du TPS avec une précision d'au moins 0,2 mm. Le fonctionnement de l'appareil a été démontré pour une grande variété de conditions de test, y compris différents profils d'enthalpie, mélanges de gaz et matériaux de TPS
Unveiling the mysteries of the solar system to understand the mechanisms of Earth’s formation, to search for signs of life, or to develop settlements on other planets, depends on our abilities to push the limits of engineering and science. One of the key aspects of space exploration is the development of advanced technologies to sustain the entry/reentry phase. During entry or reentry, the spacecraft may be exposed to intense radiative fluxes that cannot be accurately predicted yet, thus imposing high safety margins on the design of thermal protection systems. These uncertainties rise when the heat shield is made of an ablative material as its degradation introduces new chemical species reacting with the flow affecting radiation processes. The goal of this thesis is to study the radiative heat fluxes onto a small size reentry vehicle in the presence of an ablative TPS, using numerical simulations and experiments to develop a flight instrument that will be carried onboard the QARMAN CubeSat.An assessment of the reentry trajectory of the 5-kg QARMAN vehicle was performed using a custom 6-degree of freedom code. An extensive set of Monte Carlo simulations allowed to quantify uncertainties and showed a maximum of ±15% deviation from the nominal trajectory. The spectra without ablation were then computed using a decoupled approach with two codes: Stagline (VKI) and SPECAIR (EM2C, CentraleSupélec). These simulations were performed for the nominal trajectory as well as for the range of uncertainties. They showed a nonlinear behavior of the spectral features deviations from nominal with a drastic increase toward the end of the mission.The effects of ablation were studied with a new measurement technique developed during this thesis. Based on two radiation measurement probes, one cooled and the other with an ablative surface, it allows to quantify the emission and absorption induced by any kind of TPS having gas-surface interactions with the flow, provided that the radiative emission or absorption features of the ablative species do not fully overlap. The method was validated on a graphite TPS sample. It was then applied to determine the radiation expected during the QARMAN mission (Cork P50 TPS). This study also allowed to select an emission spectrometer (350-800 nm range for a 68-g mass).A standard radiation instrument was tested and the limits of this device shown. On those lessons learned, two new technologies were developed and an emission spectrometer payload (INES) was built and integrated into the QARMAN reentry CubeSat. A dedicated spectral and thermal calibration was also developed to maximize the quality of the scientific return by tackling the non-standard internal temperature variations of QARMAN’s payload bay.Relying on two inventions made during this study, the apparatus is at the time of writing, the only non-intrusive payload capable of making radiative measurements without limitations due to ablation dust contamination. The instrument can also provide measurements of recession, sublimation and swelling of the TPS with a precision of at least 0.2 mm. Operation of the apparatus was demonstrated for a wide variety of test conditions, including different enthalpy profiles, gas mixtures and TPS materials
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24

Damet, Jerome. "Physics and Detector Simulation Studies of B-Meson Decays in ATLAS." Doctoral thesis, Uppsala University, Department of Nuclear and Particle Physics, 2001. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-1284.

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25

Ball, Stephen M. "Studies of laser photolysis." Thesis, University of Oxford, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.294334.

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26

Álvarez, Ruiz Jesús. "Photon induced fluorescence studies of molecules using synchrotron radiation." Licentiate thesis, KTH, Physics, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-1567.

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This Licentiate thesis presents research accomplished at theSection of Atomic and Molecular Physics at the Royal Instituteof Technology in Stockholm using photon induced fluorescencespectroscopy (PIFS) during the last two years.

The main results presented are summarized:

- Neutral photodissociation in CO was observed aftersynchrotron photon excitation in the range 19-26 eV bycollecting dispersed fluorescence from excited neutral C atoms.Follow-up ab initio calculations point out CO Rydberg seriesconverging to the CO+ C and D states as precursors.

- The branching ratio between N2 + (B-X)(v’=1,v’’=2) and (v’=0,v’’=1)transitions in the 20-46 eV energy range reveals strongnon-Franck-Condon effects. Ab initio calculations indicate thatthe autoionization of certain superexcited states areresponsible for some of the structures present in the branchingratio curve, confirming the important role of non-Rydbergdoubly excited resonant states (NRDERS) in de-excitationprocesses above the ionization potential.

- Photon induced neutral dissociation processes in NO arereported. Neither Rydberg series nor other molecular states inNO known so far can account for the collected data. From abinitio calculations more information regarding the NO precursorstates and the mechanism behind the observed neutraldissociation were obtained.

- The details of a new experimental set-up for gas phasefluorescence measurements using synchrotron radiation aredescribed. It is able to perform simultaneous measurements ofdispersed and total fluorescence in the visible range. Thefirst results obtained with this set-up are presented,concerning fluorescence after excitation of the N2 molecules inthe N 1s edge.

These four studies conform the set of papers enclosed in theLicentiate thesis.

Finally a pre-study to further apply PIFS to speciespreviously excited by microwave discharge is included as futureplans.

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27

Davies, Robert. "Methods development and radiation damage studies in macromolecular crystallography." Thesis, University of Oxford, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.491362.

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Radiation damage limits the amount of time that a macromolecular crystal diffracts when exposed to X-ray irradiation. Various aspects of this problem were inv~stigated in this work along with methods development for quantitative determination of the metal content of proteins and celIs. In particular, the iron storage protein ferritin was used to extend current understanding of the changes that occur in macromolecular crystals held at 100 K during exposure to X-rays. The characteristics of the expl!nsion in unit celI volume with absorbed dose and with temperature were examined and found to be distinguishable. A comparison between the iron loaded (holo) and the iron void (apo) forms of ferritin alIowed the contribution to the damage ofthe absorbing iron core to be determined. Glutaraldehyde cross-linking was also tested as a method to increase r~diation resistance. Experiments were carried out to establish the room temperature dose limit of protein crystals and compare this with the dose limit measured at cryotemperatures. Surprisingly, it was found that there was a significant decrease in radiation damage at higher dose rates. An online microspectrophotometer at the European Synchrotron Radiation Facility was used to screen large numbers of potential radioprotectants at 100 K by monitoring the absorbance spectra of the 400 nm peak associated with a disulphide radical anion formed by X-ray cleavage of a disulphide bond. Ascorbate, quinone, TEMP and DIT were identified as effective radioprotectants. The most promising radioprotectant (ascorbate) was put into co-crystallisation and soaking trials with lysozyme to measure its protective effect against X-ray induced damage at 100 K and room temperature. For high throughput trace element detection, XRF was investigated, but calibration for proteins proved problematic. MicroPIXE was used for trace element mapping of wild type and Niemann Pick TypeC (a neurodegenerative disorder) cells to identify alterations in trace element composition.
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28

Studniarek, Michal. "Interface and multifunctional device spintronics : studies with synchrotron radiation." Thesis, Strasbourg, 2016. http://www.theses.fr/2016STRAE028/document.

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La spintronique multifonctionnelle est une nouvelle direction d'avancement pour aller au-delà des limites de l'électronique moderne. Il vise à développer des dispositifs qui seraient sensibles à plus d’un stimulus et/ou ont un signal multi-réponse. Dans cette thèse, nous explorons cette voie multifonctionnelle émergente en combinant l’électronique de spin et les systèmes organiques pour ouvrir la voie vers des dispositifs polyvalents. Nous étudions la formation d'une spinterface dans le système Co/manganèse-phthalocyanine. Nous proposons l'introduction de multifonctionnalités intrinsèques en utilisant des matériaux à transition de spin. Nous développons une nouvelle approche de fonctionnalisation pour ajuster leurs propriétés vers des applications. Nous proposons un contrôle fonctionnel externe sur une spinterface en utilisant un substrat multiferroïque. Dans le cadre de cette thèse, un insert polyvalent à température variable a été développé à la ligne de lumière DEIMOS du synchrotron SOLEIL. Nous démontrons comment il peut être utilisé pour sonder des atomes actifs dans n'importe quel dispositif électronique
Multifunctional spintronics is a new direction of advancement beyond the limits of modern electronics. By combining elementary charge of an electron and its spin, it aims to develop devices which would be sensitive to more than one stimuli and/or have multiresponse signal. In this thesis, we explore the multifunctional potential emerging while combining spin electronic and organic systems to pave the way towards multipurpose devices. First, we study formation of a ferromagnetic/organic spinterface in Co/manganese-phthalocyanine system. We propose introduction of intrinsic multifunctionality by using spin crossover materials. We develop a novel functionalization approach for tuning their properties towards device applications. We propose an external functional control over any hybrid spinterface by using multiferroic substrate. In the framework of this thesis, a Versatile Variable Temperature Insert was developed at the DEIMOS beamline of the SOLEIL synchrotron. We demonstrate how it can be used to probe active atoms in any microelectronic device
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Murray, James. "Structural studies of neuraminidases and x-ray radiation damage." Thesis, University of Oxford, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.418151.

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30

Eadie, Ewan David. "Studies to Target Optical Radiation Dosimetry Needs in Healthcare." Thesis, University of Dundee, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.500625.

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31

Evans, A. M. "Studies of plasmas produced by high power laser radiation." Thesis, Swansea University, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.636936.

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This thesis describes some studies of ion emission from a laser-produced plasma. The plasmas were produced by focussing a light pulse of wavelength 1.06 um and duration 35 ps from a multistage high power (GW) Neodymium-in-Glass laser system onto a solid plane target. An ion analyser mounted normal to the target, with its axis pointing directly at the site of the plasma, received a small fraction of the ions emitted from the plasma and provided data regarding their atomic nature and charge state. Preliminary measurements of ion emission using an oil-pumped vacuum chamber revealed that the targets were severely contaminated with an impurity of a hydrocarbon nature. Pre-cleaning of the target with a prior laser pulse was not possible since it was found that the impurity was rapidly re-deposited. The installation of a new turbomolecular pumping system and the meticulous cleaning of the vacuum chamber and plasma diagnostics alleviated these problems and allowed, for the first time, plasmas to be produced and studied that either contained or did not contain ions of a hydrocarbon impurity, depending upon the nature of the target site. The nature of the target site irradiated was either 'Fresh' or 'Cratered'; a fresh target site was an area of the target not previously irradiated with laser light whereas a cratered target site was an area previously irradiated with laser light. It soon became clear that plasmas produced in the new clean vacuum chamber from a 'cratered' target site contained ions of a much higher charge state than seen from a 'fresh' contaminated target site. This observation was further substantiated when the limited resolution of the original ion analyser was greatly increased by the use of an electromultiplier system of much wider bandwidth. The refinements made to the previous state of this project have made possible studies of a number of important features of the plasma, for example, fast ions where their true nature and charge state could be established. As a consequence it should be possible in the future to obtain satisfactory estimates of the electron temperature in the plasma corona.
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32

Burke, Marc. "Pulsed radiation studies of carotenoid radicals and excited states." Thesis, Keele University, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.482117.

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33

Rule, Robert J. "Studies related to crystal growth using synchrotron radiation diffraction." Thesis, University of Liverpool, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.291738.

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34

Charalambides, Stelios Nicolaou. "Remote sensing studies of Antarctica using radiation budget measurements." Thesis, Imperial College London, 1985. http://hdl.handle.net/10044/1/37655.

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35

Handrup, Karsten. "Synchrotron radiation based studies of complex molecules on surfaces." Thesis, University of Nottingham, 2014. http://eprints.nottingham.ac.uk/13988/.

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In this thesis two single molecule magnets based on the dodecamanganese (III, IV) cluster, with either benzoate or terphenyl-4-carboxylate ligands have been studied on the Au(111) and rutile TiO2(110) surfaces. We have used in situ electrospray deposition to produce a series of surface coverages from a fraction of a monolayer to multilayer films in both cases. X-ray absorption spectroscopy measured at the Mn L-edge (Mn 2p) has been used to study the effect of adsorption on the oxidation states of the manganese atoms in the core. In the case of the enzoate-functionalized complex, reduction of the manganese metal centres is observed due to the interaction of the manganese core with the underlying surface. In the case of terphenyl-4 carboxylate, the presence of this much larger ligand prevents the magnetic core from interacting with either the gold or the titanium dioxide surfaces and the characteristic Mn3+ and Mn4+ oxidation states necessary for magnetic behaviour are preserved. In contrast to the single molecule magnets where no charge transfer between the molecules and the substrates or within the molecules themselves were wanted, the molecules of bi isonicotinic acid and the giant zinc porphyrin nanorings have been studied on rutile TiO2(110) and Au(111) surfaces in the pursuit of charge transfer. In the case of the bi-isonicotinic acid it is studied on the rutile TiO2(110) where the technique of resonant inelastic X-ray scattering was been employed. Here we introduce the core-hole clock implementation to estimate the charge transfer from the molecule to the substrate. We verify previous results of ultrafast charge transfer in the sub-femtosecond regime (2.9 ± 0.3 femtoseconds) out of the LUMO+1 orbital. When the higher lying state of the LUMO+2 state is probed charge transfer out of this state and to the substrate is possibly there, but it is not possible to resolve it since it is masked by other effects originating from the inelastic scattering of the system. Furthermore, we see potential charge transfer within the molecule itself and new states observed in the inelastic scattering. Finally, zinc porphyrin nanorings were investigated on two surfaces of rutile TiO2(110) and Au(111). The techniques used here were X-ray photoemission spectroscopy and resonant photoemission spectroscopy. When the rutile TiO2(110) surface was employed hardly any participator decay was present suggesting charge transfer within the molecule itself or to the surface. This is further backed up by the fact that all of the core-excited unoccupied states are found to overlap energetically with the unoccupied states of the substrate, facilitating charge transfer out all the core-excited states. In the case of the Au(111) surface somewhat similar results are found, having all the core-excited states of the molecule located within the unoccupied states of the substrate, which again will facilitate charge transfer out all the core-excited states of the molecule. When the Au(111) substrate was employed the technique of near edge X-ray absorption fine structure was used to investigate the geometric orientation of the molecule on the surface. With the result of 86◦ ± 10◦ to the surface normal we verify previous scanning tunneling microscopy measurement that the zinc porphyrin nanorings will take a at lying orientation on the gold substrate.
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36

Taheri, Faissal Bakkali. "Numerical and experimental studies of coherent Smith-Purcell radiation." Thesis, University of Oxford, 2016. https://ora.ox.ac.uk/objects/uuid:d483c501-ba46-4e08-9d38-5af29211aedc.

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This thesis investigates the properties of coherent Smith-Purcell radiation (cSPr) at femtosecond-scale in the case of electrons bunches in the ultrarelativistic regimes. Of particular interest is the use of cSPR as a diagnostic tool to determine the longitudinal time profiles of such bunches, the study of azimuthal distribution of the radiated energy, and a contribution to the understanding of polarization properties. The study consists in a first theoretical part carried mostly in the context of the surface-current theory, supported with insights from particle-in-cell simulations. Then, as a step toward a better determination of time profile, the question of phase reconstruction is addressed through the design of a new algorithm proposed in this thesis and tested in known challenging cases. Experimental results are then presented, spanning shifts having taken place at the FACET facility at SLAC, Stanford, between 2013 and 2015.
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Haley, Benjamin. "How Protraction Moderates Radiation Risk in Animal Mortality Studies." Thesis, Northwestern University, 2017. http://pqdtopen.proquest.com/#viewpdf?dispub=10258166.

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Radiation is a ubiquitous health risk. Contemporary populations are exposed to several hundred milliSieverts per person over their lifetimes from both natural and human made sources such as radon, cosmic rays, CT-scans, etc. Risk estimates based on studies of atomic bomb survivors suggest that these exposures induce excess cancer mortality at a rate of several percent per Sievert.

To develop accurate risk estimates, it is important to recognize that contemporary exposures are different than atomic bomb survivor exposures. Instead of a single acute high dose rate exposure from an atomic explosion, populations today experience many small, protracted exposures accumulating to moderate total doses over their lifetimes. Therefore, in order to estimate the risk of contemporary exposures using atomic bomb survivor data, it is important to determine the differences in radiation dose response following acute vs. protracted exposures.

The committee to estimate the biological effects of ionizing radiation exposure in humans (BEIR) is one of the central authorities in the United States tasked with estimating radiation risk. Their seventh and most recent report (BEIR VII) written in 2006 estimated that contemporary protracted exposures induce 1.5 fold less risk than atomic bomb survivor exposures.

The work presented in this dissertation leverages a large body of historical animal mortality data to argue that BEIR VII overestimates the risk of protracted exposures. Concretely, evidence is presented from animal exposures that support the concept that contemporary protracted exposures induce about 2 fold less risk than atomic bomb survivor exposures.

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38

Bangert, D. E. "Computational studies of gratings." Thesis, University of Cambridge, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.344034.

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39

Clingen, Peter H. "Biochemical studies of purine photodamage in DNA." Thesis, Queen's University Belfast, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.241386.

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40

Ozols, Agris. "Low-dose studies of genomic instability-mechanisms and targets." Thesis, Queen Mary, University of London, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.271260.

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41

Nguti, N. D. "Laue and anomalous diffraction studies in synchrotron radiation protein crystallography." Thesis, Keele University, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.295803.

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42

Thurston, Gavin O. "Studies on the effect of radiation on 3T3 cell motility." Thesis, University of British Columbia, 1988. http://hdl.handle.net/2429/29441.

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The ability of mammalian cells to locomote is important in a variety of normal and pathological processes. Previous work has suggested that low doses of x-irradiation may perturb cell motility, a finding that may have important consequences in embryogenesis, cancer metastasis, and immune response. This thesis has sought to study in more detail the effect of radiation on mammalian cell motility. Work performed in other laboratories used the colloidal gold assay and time lapse cinemicroscopy to study x-irradiation induced changes to 3T3 fibroblast motility in tissue culture. These studies were repeated here, with qualitative results similar to those reported earlier. However, these methods were not amenable to a detailed quantitative analysis. For this, spatial and temporal information on the motility and dynamic morphology of a large number of cells is required. Such a task would be impossible to perform manually, thus an automated microscope system was developed that used a computer-driven precision stage and a solid state optical sensor to track individual cells in tissue culture. Information on motility and morphology was concurrently extracted from many cells. As part of the thesis, several techniques were developed to analyze and display these data, and to correlate motility and morphology observations. These techniques were directed at preserving the actual process of 3T3 cell motility, and parameters were measured to quantify the short term persistence of cell movement (on a time scale of 0.5 to 2 hours), and the long term persistence of cells in maintaining certain characteristic behaviour (on a time scale of 3 to 12 hours). The response of 3T3 fibroblasts to x-irradiation was characterized by a number of parameters. The population average cell speed was measured following treatment, and a dose response and time response was determined in the range of 1.5 Gy. Other motility parameters indicate that the normal process of cell motility, evidenced by a series of motile segments, was disrupted by x-rays. This was thought to reflect perturbation to the control mechanisms of cell motility. The morphology of 3T3 cells stained with Coomassie blue was examined in an effort to correlate the observed motility changes with changes in the fixed cell morphology. This stain is a general structural protein stain with higher affinity toward microfilaments. High doses of x-rays were required to produce significant perturbation to cell morphology, and in the dose regime of interest, the morphology of irradiated cells was not identifiably different from control. Of note is that it was the well spread, quiescent cells that seemed least perturbed by large doses of irradiation. In summary, x-rays apparently disrupt the normal process of cell motility. Several lines of evidence suggest that actively migrating cells are the most perturbed by irradiation. This work has developed techniques to quantify cell motility in a meaningful way, and to characterize the x-ray induced perturbations.
Science, Faculty of
Physics and Astronomy, Department of
Graduate
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43

MacManus, Liam Francis. "Surface modification studies of polypropylene using ultraviolet radiation and ozone." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ32497.pdf.

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44

Lee, SangKyu. "Image-based dose correlation studies on radiation- induced lung injury." Thesis, McGill University, 2011. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=97013.

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The goal of this work is to develop an accurate and automatic tool to evaluate normal lung tissue response to radiotherapy (RT) and its correlation with local dose. Manifestation of radiation-induced lung disease (RILD)in radiography is a measurable endpoint for RT-induced normal tissue complication. Follow-up CT images from RT-received non-small-cell lung cancer patients were registered to a corresponding planning CT image. Followingimage intensity calibration, the extent of RILD was segmented based on the change in physical density during the follow-up period. Dose coverage to the RILD segmentation and healthy lung was calculated based on retrievedtreatment plans. Normal tissue response in terms of RILD volume and local dose-response showed dependency on patients and follow-up periods. Monte-Carlo dose calculation was found to be important to obtain bettercorrelation. Provided the improved accuracy in CT calibration and image registration, this tool can facilitate further normal tissue toxicity studies.
Le but de ce travail est de développer un outil automatisé de haute précision permettant d'evaluer la réponse de tissus de poumons sains à la radiothérapie (RT), ainsi que leurs corrélation avec la dose locale. Les complications de tissus de poumons sains induites par RT peuvent être mesurées à l'aide des manifestations de maladies pulmonaires induites par radiations (MPIR) en radiographie. Le suivi des images CT par des cellules de poumons cancéreuses provenant de la RT a été enregistré à leur image CT de planication correspondante. à l'aide du suivi de la calibration de l'intensité de l'image, l'etendue des MPIR a été segmentée en se basant sur le changement de densité physique durant la période de suivi. La dose reliée à la segmentation des MPIR et aux tissus de poumons sains a été calculée en se basant sur des planications de traitements établis. La réponse des tissus sains en termes de volume MPIR et la réponse de la dose locale ont démontrées une dépendance signicative par rapport aux patients et aux périodes de suivi. Le calcul de dose par simulations Monte-Carlo sest révélé être important an d'obtenir de meilleures corrélations. En tenant compte de l'amélioration de l'exactitude des calibrations CT et des enregistrements d'image, cet outil peut faciliter le déroulement des futures études de toxicité des tissus sains.
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45

Clegg, R. "Radiation-chemical studies of some sulphophthalocyanine complexes and vitamin B12." Thesis, University of Salford, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.374501.

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46

Bebb, Andrew M. "Synchrotron radiation studies of spin-polarised electron momentum density distributions." Thesis, University of Warwick, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.404845.

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47

Maginn, Stephen James. "Applications of synchrotron radiation Laue diffraction in molecular structure studies." Thesis, University of Liverpool, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.253418.

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48

Yang, Chenxing. "Simulation studies of liquids, supercritical fluids and radiation damage effects." Thesis, Queen Mary, University of London, 2017. http://qmro.qmul.ac.uk/xmlui/handle/123456789/24858.

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The work in this thesis aims to gain fundamental understanding of several important types of disordered systems, including liquids, supercritical fluids and amorphous solids on the basis of extensive molecular dynamics simulations. I begin with studying the diffusion in amorphous zirconolite, a potential waste form to encapsulate highly radioactive nuclear waste. I find that amorphization has a dramatic effect for diffusion. Interestingly and differently from previous understanding, diffusion increases as a result of amorphization at constant density. Another interesting insight is related to different response of diffusion of different atomic species to structural disorder. I calculate activation energies and diffusion pre-factors which can be used to predict long-term diffusion properties in this system. This improves our understanding of how waste forms operate and provides a quantitative tool to predict their performance. I subsequently study the effects of phase coexistence and phase decomposition in Y-stabilized zirconia, the system of interest in many industrial applications including in encapsulating nuclear waste due to its exceptional resistance to radiation damage. For the first time I show how the microstructure emerges and evolves in this system and demonstrate its importance for self-diffusion and other properties. This has not been observed before and is important for better understanding of existing experiments and planning the new ones. I subsequently address dynamical properties of subcritical liquids and supercritical fluids. I start with developing a new empirical potential for CO2 with improved performance. Using this and other potentials, I simulate the properties of supercritical H2O, CO2 and CH4 and map their Frenkel lines in the supercritical region of the phase diagram. I observe that the Frenkel line for CO2 coincides with experimentally found maxima of solubility and explain this finding by noting that the Frenkel line corresponds to the optimal combination of density and temperature where the density is maximal and the diffusion is still in the fast gas-like regime. This can serve as a guide in future applications of supercritical fluids and will result in their more efficient use in dissolving and extracting applications. I extend my study to collective modes in liquids. Here, my simulations provide first direct evidence that a gap emerges and evolves in the reciprocal space in transverse spectra of liquids. I show that the gap increases with temperature and is inversely proportional to liquid relaxation time. Interestingly, the gap emerges and evolves not only in subcritical liquids but also in supercritical fluids as long as they are below the Frenkel line. Given the importance of phonons in condensed matter physics and other areas of physics, I propose that the discovery of the gap represents a paradigm change. There is an active interest in the dynamics of liquids and supercritical fluids, and I therefore hope that my results will quickly stimulate high-temperature and high-pressure experiments aimed at detecting and studying the gap in several important systems.
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Celik, Murat. "Experimental and computational studies of electric thruster plasma radiation emission." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/40306.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2007.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Includes bibliographical references (p. 231-239).
Electric thrusters are being developed for in-space propulsion needs of spacecraft as their higher specific impulse enables a significant reduction in the required propellant mass and allows longer duration missions. Over the last few decades many different electric propulsion concepts have been proposed and studied. In studying the electric thrusters, in order to improve the thruster performance as well as to understand the underlying physics of thruster's operation, various diagnostics methods were employed. As one unique method, emission spectroscopy provides a non-invasive, fast and economical diagnostic allowing also the ability to access hard to reach locations. In this study, emission spectroscopy is employed as a means to determine the trends in thruster operations as well as diagnosing the plasma parameters. This study presents the spectral measurement results of three different electric thrusters and plasma sources. First, the BHT-200 Hall thruster emission spectra measurements are presented for varying discharge voltage and for various regions of observation.
(cont.) Second, spectral measurements of a TAL type laboratory mini-Hall thruster, MHT-9, were presented. Third, radiation emission measurements of an experimental Helicon plasma source being studied to assess the possibility of using Helicon discharge as a propulsive system are presented and the trends are discussed. Two collisional-radiative (C-R) models are developed for Argon and Xenon plasmas to analyze the experimental spectra. In the C-R models, electron induced excitation, deexcitation and ionization collisions, and spontaneous radiative de-excitation transitions are simulated for neutral and singly charged ion species. The models are validated against measured spectra obtained using different experimental setups. The BHT-200 Hall thruster has insulator ceramic annular walls made of Boron-Nitride (BN). Erosion of ceramic walls is one of the major life limiting factors for Hall thrusters. Emission spectroscopy is used as a means to determine the trends in the thruster wall erosion rate by measuring the radiation emission of the Boron neutral 249.68nm and 249.77nm lines. Discussion about the spectral measurements and relevant analysis are presented.
by Murat Çelik.
Ph.D.
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50

Trachenko, Kostyantyn Oleksiyovich. "Simulation studies of silica glass dynamics and radiation damage effects." Thesis, University of Cambridge, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.620962.

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