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Gurke, Johannes. "Protons and Photons." Doctoral thesis, Humboldt-Universität zu Berlin, 2019. http://dx.doi.org/10.18452/19747.
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Gegenstand dieser Arbeit ist die Frage wie thermische und photochemische Gleichgewichte verbunden werden können und sich gegenseitig beeinflussen. Dazu wurden zwei Projekte bearbeitet, zum einen das Konzept der „säure-katalysierten Zykloreversion“ und zum anderen das Konzept der „licht-induzierten pKs Veränderung“. Im ersten Konzepte wurde eine extern steuerbare, thermische Rückreaktion genutzt, um die Zusammensetzung im photostationären Zustand zu kontrollieren. Durch Zugabe von katalytischen Mengen einer starken Säure wurde die Ringöffnung eines Diarylethens, welches mit einem Flurenol substituiert ist, eingeleitet. Der zugrundeliegende Prozess wurde kinetisch und thermodynamisch, sowohl durch Experimente als auch durch computergestützte Rechnungen beschrieben. Eine säure-induzierte Dehydratation öffnet einen neuen Reaktionspfad, wodurch die normalerweise sehr hohe Reaktionsbarriere der Ringöffnung umgangen werden kann. Die quantitative Umsetzung mit Säure führt zu einer kompletten Löschung der photochemischen Reaktivität. Dieses Konzept kann in der Speicherung von Lichtenergie in photochromen metastabilen Systemen genutzt werden. Durch die Nutzung von 3-H-Thiazol-2-on als Rest im Diarylethen konnte eine signifikante pKs Änderung von 2.8 Einheiten in wässriger Umgebung erreicht werden. Dabei wurden zwei Säure-Base Gleichgewichtssysteme miteinander gekoppelt, welche an der thermischen Umwandlung gehindert sind, jedoch photochemisch ineinander überführt werden können. Des Weiteren wurde eine hohe Abhängigkeit der Quantenausbeute von dem Protonierung festgestellt. Diese wurde genutzt um die Performance der Photoreaktion zu beeinflussen. Die Beeinflussung der Photoreaktion erfolgt nicht durch Veränderung der Energetik des Grundzustandes, sondern durch Veränderung der Potentialhyperfläche des angeregten Zustandes. Durch neue molekulare Designs konnte eine signifikante Verbesserung im Vergleich zu bekannter Molekülen und Konzepten in beiden Projekten erreicht werden.Two projects are implemented in this work, which share the goal to interconnect acid-base equilibria with the photoreactions of diarylethene (DAE) photoswitches. This task can be divided into two logic questions: How can photochemical equilibria be controlled or rather influenced via an acidic or basic stimulus and how can a photoreaction induce control over an acid-base equilibrium? In the first project, “Acid-Catalyzed Cycloreversion”, an externally tunable thermal back reaction was designed to influence a photochemical equilibrium. Upon addition of catalytic amounts of acid, a closed DAE carrying a fluorenol moiety undergoes facile thermal ring opening. The underlying thermodynamics and kinetics of the entire system have been analyzed experimentally as well as computationally. Appling an excess of acid leads to a complete inhibition of the photoreaction through the introduction of a charge-transfer. My work suggests that acid catalysis provides a useful tool to bypass thermal barriers, potentially usable to efficiently trigger the release of light energy stored in photoswitches. In the second project, entitled “Light-induced pKa Modulation”, a significant pKa change of 2.8 units in an aqueous medium was achieved by connecting two different acid-base equilibria. These thermodynamic equilibria are separated by a high activation barrier, overcome by a photoreaction. The developed system which is based on the incorporation of a 3 H thiazol 2 one moiety into a DAE, shows a strong dependency of the quantum yield and hence, of the photoconversion on the protonation state. Adjusting the pH within the range of the pKa change, a substantial enhancement of the photoconversion is achievable as well as a distinct alteration of the performance of the photoreaction. This effect does not originate from different reaction paths on the ground state potential energy surface (PES), but results presumably from a protonated state dependent difference in the excited PES.
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JAFER, RASHIDA. "Laser plasma protons and applications in cancer therapy and proton radiography." Doctoral thesis, Università degli Studi di Milano-Bicocca, 2009. http://hdl.handle.net/10281/7457.
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Recent developments in high power, ultrashort pulse laser systems enable laser intensities beyond 10^21 W/cm^2 to be achieved. When focused onto thin foil targets, plasmas with extremely high electrostatic fields (>10^12V/m) are produced, resulting in the acceleration of protons/ions to very high energies (~60MeV). During my PhD, I have worked on experimental investigations into proton acceleration driven by high power laser pulses. Key to successful deployment of laser proton sources one one side is getting higher proton energies through to achieve the ultimate goal of realising table top machines for the treatment of cancer and on the other side, optimising the beam quality, an objective that was of the main motivation for my PhD work. My two main achievements were:
1. The production of bright, ultrashort and radially smooth pulsed proton beams using laser heating of pre-plasmas formed with long (nanosecond) pulses with ultrahigh intensity picosecond pulses.
2. Use of these beams to study the ultrafast dynamics of target implosion under intense laser irradiation
The experiments on proton acceleration with the specific goal of controlling the proton beam quality by optical tool design, were performed at RAL. This scheme involves the use of multiple laser pulses to enhance and control the properties of beams of protons accelerated in ultra-intense laser irradiation of planar foil targets. Specifically, one laser pulse produces and controls the expansion of the target to enhance the energy coupling to the main (delayed) laser and/or drives shock deformation of the target to change the direction of the proton beam. The preplasma formed by this low intensity nanosecond beam (~ 0.5-5x10^12 W/cm^2) was used to enhance the laser absorption of the main (delayed) CPA (Chirped pulse amplified). The main CPA picosecond beam was used at high intensity (~ 4x 10^20 W /cm^2) to produce intense proton beams from the hydrogen rich target. The optimum intensity of the nanosecond beam was investigated and optimised to yield a very smooth and circular distribution of the proton beam achieved using a second long pulse laser at 5x10^12w/cm^2.
The second achievement concerns an experiment also performed at RAL on proton radiography. As the laser based protons are characterised by small source size, high degree of collimation and short duration, they can be used in point projection backlighting schemes to perform radiography. In particular, I used this idea to perform radiography of a cylindrical target ~ 200µm long imploding under irradiation by long laser pulses of nanosecond duration. This allows measuring the degree of compression of the target as well as the stagnation time in the dynamic regime. The experiment took place in the framework of the HiPER project (the European High Power laser Energy Research facility Project). The final goal of the experiment was to study the transport of fast electron in cylindrical compressed target a subject of interest for fast ignition. In parallel to proton radiography x-ray radiography was used to compare the results. One of the specific advantages of using laser generated protons is that their spectrum is continuous upto a high energy cutoff. Because of their different time of flights protons proved to be very effective in revealing the implosion history of the target. In principle, the obtained implosion can be followed in time with a single shot sensitivity. Instead x-ray radiograph gives one image per laser shot at one fixed time and one has to make several shots in order to reveal the complete history of implosion. Another advantage of using proton radiography is a simpler experimental setup keeping imploding cylinder between proton target and proton detector on the same axis. Simulations of formation of proton images were made with the Monte Carlo MCNPX Code using the density profiles of the imploded cylinder obtained with the 2D-hydro CHIC code. A detailed study of Multiple Coulomb Scattering and Stopping Powers of the protons in low energy regimes for cold and warm matter was done to interpret the experimental results.
Finally, I’m taking part in the analysis of experimental results obtained at the University of Rochester (USA) on the Omega-EP laser, and concerning magnetic field effect on the proton radiographs of a wired cone.
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Pilcher, John Victor. "Coincident proton decay of the continuum induced by 200 MeV protons on 12C." Doctoral thesis, University of Cape Town, 1989. http://hdl.handle.net/11427/17190.
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Bibliography: p. 212-221.Coincident protons from the reaction ¹²C(p,2p) at an incident proton energy of 200 Me V, have been measured using conventional particle telescopes. Data were acquired at nine pairs of angles (θ₂=20°, 45°, 70°, 95°, 120° and 145° for θ₁ =-20°, and θ₂=35°, 85° and 135° for θ₁ =-45°). An improved model, based on previous theoretical and experimental work, has been proposed to describe the reaction mechanism leading to the observed coincident proton yield from the nuclear continuum. This model considers an initial quasifree nucleon-nucleon interaction - described by a distorted wave impulse approximation (DWIA) treatment - between the incident proton and a single target nucleon, followed by the rescattering of the struck nucleon, which behaves as an intranuclear projectile, from the spectator part of the target nucleus. The validity of the DWIA treatment used in the continuum study, has been tested by analysing the kinematic regions of the coincident proton energy spectra corresponding to the knockout of protons from the outer lp3/2 orbital of ¹²C which do not undergo further interactions with the residual nucleus. Good agreement in shape has been found between the calculated and measured cross sections in the kinematic region of interest to the continuum study. An average spectroscopic factor of 1.1±0.3 was extracted. Except in the -20°,20° case, the DWIA treatment was found to be insensitive to the choice of the initial or final energy prescriptions for the two-body scattering approximation. Nonlocality effects were found to be small, changing the absolute value of spectroscopic factors by a maximum of 20%. Coincident continuum cross sections were extracted from the experimental data corresponding to the detection of protons at the θ₁ angles with energies of 70±5 MeV, 100±5 MeV and 130±5 MeV. Comparisons were made with calculations which modelled the proposed reaction mechanism in terms of a convolution integral over the DWIA cross sections describing the initial quasifree knockout process and experimental inelastic scattering probabilities describing the further multiple scattering interactions undergone by the knocked out nucleons. Good agreement has been found between the normalized calculated and measured continuum cross sections (spectroscopic factors varying from 0.8 to 2.3 between sets of data, depending on the kinematic region sampled and the prescription used for the two-body scattering approximation). It has been shown that contributions from nucleons that are knocked out both in- and out-of-plane in the initial quasifree process should be considered, and that the contribution from neutron knockout in the initial interaction is significant, ranging from 0.13 to 0.62 that of the proton knockout contribution.
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Roder, Ana Flávia Vidotti [UNESP]. "Estudo da interação de prótons com alvos não homogêneos, aplicados a tomografia com feixes de prótons." Universidade Estadual Paulista (UNESP), 2014. http://hdl.handle.net/11449/108789.
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000769599.pdf: 18986432 bytes, checksum: a3924b26321cd155af0495154ed8096f (MD5)O tratamento do câncer através da irradiação com prótons tem se desenvolvido a amplamente, de maneira que a cada década o número de centros com essa tecnologia aumenta progressivamente. Entretanto, o planejamento da rotina de terapia ainda é realizado com imagens de raios-X, que pode causar incertezas quanto ao posicionamento preciso do feixe de prótons sobre o tumor devido à diferença de comportamento ao interagir com a matéria. Por isso, são necessários estudos que busquem o aprimoramento da tomografia computadorizada com prótons, que tem como principal função, determinar a posição do pico de Bragg com eficiência. Mas para se desenvolver essa técnica é preciso determinar a trajetória exata que a partícula percorre dentro do corpo do paciente, que é possível com simulações baseadas no método de Monte Carlo. Vários programas no mercado utilizam Monte Carlo para diferentes tipos de propósitos, dentre os que são voltados para o transporte do próton, estão: GEANT, FLUKA e MCNPX. Esse último foi o utilizado neste trabalho para avaliar a perturbação no feixe incidente de prótons em um meio heterogêneo, composto por água e material simulador de osso compacto (interfaces perpendiculares ao feixe). Além de um modelo formado por água e PMMA (interfases paralelas ao feixe) para avaliar o uso de fantomas desses materiais. Foram estudadas energia, posição e ângulo de saída dos prótons considerando somente partículas primárias e também para todas as partículas
Cancer treatment by irradiation with protons has been widely developed so that each decade the number of centers based on this technology increases progressively. However, the planning of routine therapy is performed with images of X- rays, which can cause uncertainties as to the precise positioning of the proton beam on the tumor due to the difference in behavior when interacting with matter. Therefore, it is necessary studying the improvement of computed tomography with protons, whose main function, determine the position of the Bragg peak efficiently. Nevertheless, to develop this technique it is necessary to determine the exact path that the particle travels through the patient's body, which is possible with simulations based on Monte Carlo method. There are several programs that use Monte Carlo for different types of purposes, among which are meant for the transport of the proton: GEANT, FLUKA and MCNPX. The third one was used in this work to evaluate the disturbance in the incident beam of protons in a heterogeneous medium composed of water and equipment simulator compact bone (beam direction perpendicular to the interface) and water-PMMA (beam parallel to the interface). The output energy, position and angle of the protons were studied considering only primary particles and for all particles
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Tripp, Robert D. "Elastic scattering of high-energy polarized protons by complex nuclei." Berkeley, Ca. : Lawrence Radiation Laboratory, 2975. http://catalog.hathitrust.org/api/volumes/oclc/549450172.html.
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Reinhardt, Sabine. "Detection of laser–accelerated protons." Diss., lmu, 2012. http://nbn-resolving.de/urn:nbn:de:bvb:19-155620.
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Galand, Marina. "Transport des protons dans l'ionosphère aurorale." Phd thesis, Université Joseph Fourier (Grenoble), 1996. http://tel.archives-ouvertes.fr/tel-00724355.
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Les électrons et les protons suprathermiques, issus du soleil et précipitant dans l'atmosphère des hautes latitudes, constituent une source d'énergie de l'ionosphère terrestre. Ces particules interagissent avec le gaz thermique ambiant par collisions. L'équation de Boltzmann, fournissant les flux de particules en altitude, énergie et angle d'attaque, permet une description des plus complètes du transport de ces particules. Nous la redémontrons dans le cas dissipatif, le plus général, et nous proposons une résolution originale des équations de transport des protons et des atomes d 'hydrogène, équations couplées via les réactions de changement de charge. Cette résolution, fondée sur l'introduction de forces dissipatives pour décrire la dégradation énergétique des particules précipitant, permet la prise en compte des redistributions angulaires, d'origine collisionnelle ou magnétique, jusqu'alors négligées. Pourtant, leur effet a été observé, depuis le sol, sur les émissions des atomes d 'hydrogène, comme en témoigne la composante, décalée vers le rouge, du profil Doppler selon le zénith magnétique. La résolution adoptée ici est validée par comparaison avec un autre modèle, dans le cas classique sans redistribution angulaire. L'influence de l'effet de miroir magnétique est discutée: cet effet ne semble pas pouvoir expliquer, à lui seul, le décalage vers le rouge observé. La redistribution angulaire collisionnelle doit jouer un rôle significatif. Enfin, une comparaison de notre modèle avec les données de la fusée Proton 1 est proposée.
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Kar, S. "Application of MeV laser-driven protons." Thesis, Queen's University Belfast, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.426792.
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Mooser, Andreas [Verfasser]. "Der g-Faktor des Protons / Andreas Mooser." Mainz : Universitätsbibliothek Mainz, 2014. http://d-nb.info/1051353440/34.
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Johnson, Samantha. "Optimizing the ion source for polarized protons." Thesis, University of the Western Cape, 2005. http://etd.uwc.ac.za/index.php?module=etd&.
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Beams of polarized protons play an important part in the study of the spin dependence of the nuclear force by measuring the analyzing power in nuclear reactions. The source at iThemba LABS produces a beam of polarized protons that is pre-accelerated by an injector cyclotron (SPC2) to a energy of 8 MeV before acceleration by the main separated-sector cyclotron to 200 MeV for physics research. The polarized ion source is one of the two external ion sources of SPC2. Inside the ion source hydrogen molecules are dissociated into atoms in the dissociator and cooled to a temperature of approximately 30 K in the nozzle. The atoms are polarized by a pair of sextupole magnets and the nucleus is polarized by RF transitions between hyperfine levels in hydrogen atoms. The atoms are then ionized by electrons in the ionizer. The source has various sensitive devices, which influence beam intensity and polarization. Nitrogen gas is used to prevent recombination of atoms after dissociation. The amount of nitrogen and the temperature at which it is used plays a very important role in optimizing the beam current. The number of electrons released in the ionizer is influenced by the size and shape of the filament. Optimization of the source will ensure that beams of better quality (a better current and stability) are produced.
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Bezuidenhout, Jacques. "Pre-equilibrium helion emission induced by protons." Thesis, Link to the online version, 2006. http://hdl.handle.net/10019.1/1307.
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Inocente, Guilherme Franco [UNESP]. "Estudo teórico da relação entre número de CT de raios-X e Stopping Power de prótons." Universidade Estadual Paulista (UNESP), 2012. http://hdl.handle.net/11449/87806.
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000709627.pdf: 615342 bytes, checksum: ecb29e15c1848924480b318430ee4378 (MD5)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
Um dos métodos mais utilizados para tratamento de câncer e o uso da radiação. Nesse contexto surge a terapia com feixes de prótons em frente a radioterapia convencional. Sabe-se que com a protonterapia há mais vantagens para o paciente tratado quando comparada com os métodos mais convencionais. A dose distribuída ao longo do caminho percorrido, principalmente nos tecidos sadios - região vizinha ao tumor, e menor e a acurácia do tratamento é muito melhor. Para a realização do tratamento, o paciente passa por alguns procedimentos e um deles é realizar uma imagem para visualização e localização do volume alvo. O principal método para obter essas imagens e a tomografia computadorizada de raios-X (XCT). Para o tratamento com feixes de prótons essa técnica de imagem pode gerar algumas incertezas. A proposta deste estudo é analisar a viabilidade de se reconstruir imagens geradas a partir da irradiação com feixes de prótons, e com isso diminuir algumas imprecisões, já que ser a o mesmo tipo de radiação para planejamento como tratamento, é também para diminuir drasticamente alguns erros de localização, uma vez que o planejamento poder a ser feito no mesmo local e em instantes antes onde o paciente ser a tratado. Este trabalho tem por finalidade, obter uma rela ção entre a propriedade intrínseca da interação de fótons e prótons com a matéria. Para isso utilizaremos de simulação computacional baseada no método de Monte Carlo, com os códigos SRIM 2008 e MCNPX v.2.5.0, para reconstruir imagens através da técnica utilizada na tomografia computadorizada convencional
The radiation method is one of the most used for cancer treatment. In this context arises therapy with proton beams in front of conventional radiotherapy. It is known that with protontherapy there are more advantages to the patient treatement when compared with more conventional methods. The dose distributed along the path, especially in healthy tissues neighbor the tumor, is smaller and the accuracy of treatment is much better. To carry out the treatment, the patient undergoes a plan through images for visualization and location of the target volume. The main method for obtaining these images is computed tomography X-ray (XCT). For treatment with proton beam this imaging technique can to generate some uncertainties. The purpose of this study is to analyse the feasibility of reconstructing images generated from the irradiation with proton beams, thereby reducing some inaccuracies, as it will be the same type of radiation as treatment planning, and also to drastically reduce some errors location, since the planning can be done at the same place and just before where the patient is treated. This study aims to obtain a relationship between the intrinsic property of the interaction of photons and protons with matter. For this we use computational simulation based on Monte Carlo method with the code SRIM 2008 and MCNPX v.2.5.0, to reconstruct images using the technique used in conventional computed tomography
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Inocente, Guilherme Franco. "Estudo teórico da relação entre número de CT de raios-X e Stopping Power de prótons /." Botucatu, 2012. http://hdl.handle.net/11449/87806.
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Orientador: Joel Mesa HormazaBanca: Roberto Morato Fernandez
Banca: João Dias de Toledo Arruda Neto
Resumo: Um dos métodos mais utilizados para tratamento de câncer e o uso da radiação. Nesse contexto surge a terapia com feixes de prótons em frente a radioterapia convencional. Sabe-se que com a protonterapia há mais vantagens para o paciente tratado quando comparada com os métodos mais convencionais. A dose distribuída ao longo do caminho percorrido, principalmente nos tecidos sadios - região vizinha ao tumor, e menor e a acurácia do tratamento é muito melhor. Para a realização do tratamento, o paciente passa por alguns procedimentos e um deles é realizar uma imagem para visualização e localização do volume alvo. O principal método para obter essas imagens e a tomografia computadorizada de raios-X (XCT). Para o tratamento com feixes de prótons essa técnica de imagem pode gerar algumas incertezas. A proposta deste estudo é analisar a viabilidade de se reconstruir imagens geradas a partir da irradiação com feixes de prótons, e com isso diminuir algumas imprecisões, já que ser a o mesmo tipo de radiação para planejamento como tratamento, é também para diminuir drasticamente alguns erros de localização, uma vez que o planejamento poder a ser feito no mesmo local e em instantes antes onde o paciente ser a tratado. Este trabalho tem por finalidade, obter uma rela ção entre a propriedade intrínseca da interação de fótons e prótons com a matéria. Para isso utilizaremos de simulação computacional baseada no método de Monte Carlo, com os códigos SRIM 2008 e MCNPX v.2.5.0, para reconstruir imagens através da técnica utilizada na tomografia computadorizada convencional
Abstract: The radiation method is one of the most used for cancer treatment. In this context arises therapy with proton beams in front of conventional radiotherapy. It is known that with protontherapy there are more advantages to the patient treatement when compared with more conventional methods. The dose distributed along the path, especially in healthy tissues ���� neighbor the tumor, is smaller and the accuracy of treatment is much better. To carry out the treatment, the patient undergoes a plan through images for visualization and location of the target volume. The main method for obtaining these images is computed tomography X-ray (XCT). For treatment with proton beam this imaging technique can to generate some uncertainties. The purpose of this study is to analyse the feasibility of reconstructing images generated from the irradiation with proton beams, thereby reducing some inaccuracies, as it will be the same type of radiation as treatment planning, and also to drastically reduce some errors location, since the planning can be done at the same place and just before where the patient is treated. This study aims to obtain a relationship between the intrinsic property of the interaction of photons and protons with matter. For this we use computational simulation based on Monte Carlo method with the code SRIM 2008 and MCNPX v.2.5.0, to reconstruct images using the technique used in conventional computed tomography
Mestre
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Driant, Thomas. "On the role of protons in the reactivation of acetylcholinesterase : quantum and molecular mechanics studies." Thesis, Paris 6, 2017. http://www.theses.fr/2017PA066218/document.
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Le projet de cette thèse était l'évaluation du processus de réactivation et l'étude du site actif de l'AChE inhibée par un agent neurotoxique par des méthode computationnelles. L'objectif était de guider le design rationnel de nouveau réactivateurs. Une étude initiale avec un modèle QM tronqué a indiqué la nécessité de modéliser l'environnement enzymatique pour compenser la charge du Glu334. Elle a aussi confirmé le rôle du trou oxyanionique dans la stabilisation des états de transition de la réactivation. Des simulations QM/MM de la réactivation par le réactivateur classique 2-PAM, ainsi que par deux réactivateurs au coeur aromatique non chargé ont été effectuées. Il a été démontré que le Glu202, un résidu à proximité de la triade catalytique de l'AChE, doit être protoné pour que la réactivation ait lieu. Ces simulations ont aussi montré que le réactivateur peut être déprotoné dans le site actif de l'AChE par His447. Les réactivateurs au coeur aromatique non chargé sont plus nucléophiles que la 2-PAM et l'un d'entre eux est plus aisément déprotoné dans le site actif. Nos résultats indiquent que la capacité d'un réactivateur à être facilement déprotoné est plus importante que sa nucléophilie. Enfin, un mécanisme de migration de protons a été identifié par des calculs QM/MM et EVB. Il implique deux glutamates derrière le site actif, Glu450 et Glu452. La possibilité que ces deux protons soient temporairement protonés et donc impliqués dans une migration de protons a été confirmé par des calculs CpHMD. La migration de proton passe par la N-protonation d'une liaison amide, ce qui constitue un nouveau mécanismeThe project of this PhD was to investigate the reactivation process and the active site of nerve agent inhibited AChE by computational methodologies to gain insight about the rational design of new reactivators. An initial truncated QM model study provided some insight in the necessary compensation of Glu334 by the enzyme. It also confirmed the role of the oxyanionic hole in the stabilization of the transition state of the reactivation. QM/MM simulations of the reactivation with classical reactivator 2-PAM, as well as two non-pyridinium reactivators, were performed. It was shown that Glu202, a residue near the catalytic triad of AChE, needs to be protonated for the reactivation to occur. Those simulations also showed that the reactivator can be deprotonated in the active site of AChE by His447. Non-pyridinium reactivator were found to have a greater nucleophilicity than 2-PAM and, for one of them, to be easily deprotonated in the active site. Our results indicate that the capacity of a reactivator to be deprotonated in the active site of the enzyme is more important than its nucleophilicity. Finally, a proton relay mechanism was identified through QM/MM and EVB simulations. It involves two glutamate residues, Glu450 and Glu452, positioned behind the active site. The potential for these two residues to be transiently protonated and thus involved in a proton relay was confirmed by CpHMD simulations. This proton relay mechanism relies on the N-protonation of an amide which is a novel mechanism
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Audirac, Laurent. "Etude de la radioactivité 2-protons de 45Fe avec une chambre à projection temporelle." Phd thesis, Bordeaux 1, 2011. http://tel.archives-ouvertes.fr/tel-00659079.
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L'étude des noyaux exotiques est un outil important pour sonder la structure nucléaire des noyaux éloignés de la stabilité. Pour des noyaux situés à la drip-line proton, l'émission directe de protons a été prédite depuis le début des années 1960. Ce travail de thèse est focalisé sur l'étude de la radioactivité 2-protons du noyau 45Fe. Un modèle théorique récent, dit modèle à trois corps, prévoit les corrélations énergétiques et angulaires qui doivent exister entre les protons émis. Afin d'étudier le processus d'émission, une Chambre à Projection Temporelle a spécialement été conçue pour reconstruire en trois dimensions la trajectoire des protons. Elle a été utilisée pendant une expérience sur le séparateur LISE3 du GANIL pour l'étude de 45Fe. Pour la première fois, les deux protons émis ont pu être détectés individuellement. Des outils d'analyse spécifiques ont permis de calculer les corrélations énergétiques entre les protons, montrant qu'ils partagent équitablement l'énergie disponible, tel que le prévoient les différents modèles théoriques. Les corrélations angulaires ont été étudiées, mais le manque de statistique ne permet pas de trancher définitivement sur le processus d'émission mis en jeu même si les données sont en accord avec les prévisions du modèle à trois corps. L'expérience a également permis d'étudier l'émission retardée de protons de 43Cr. L'émission beta-2p a été identifiée ; les corrélations énergétiques et angulaires sont en faveur d'une émission séquentielle des deux protons. Enfin, et pour la première fois, l'émission retardée de trois protons a été observée pour ce noyau.
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Mussgiller, Andreas. "Identification and tracking of low energy spectator protons." [S.l.] : [s.n.], 2006. http://deposit.ddb.de/cgi-bin/dokserv?idn=983453950.
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Harwin, Michael John. "Soft hadron photoproduction at 20 GeV from protons." Thesis, Imperial College London, 1986. http://hdl.handle.net/10044/1/38029.
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KRAUSER, SABINE. "L'omeprazole, un inhibiteur de la pompe a protons." Université Louis Pasteur (Strasbourg) (1971-2008), 1990. http://www.theses.fr/1990STR15073.
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Berthet, Patrick. "Étude de la production cohérente de mésons [pi et êta] à grand transfert dans les collisions protons-deutons." Paris 11, 1986. http://www.theses.fr/1986PA112071.
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Les réactions pd→ 3Heπ° et pd→ 3Heη ont été étudiées pour des angles de production des mésons voisins de 180° (cm) avec des protons d’énergie cinétique comprise entre 0,92 et 2,6 GeV. Ces expériences ont été effectuées en détectant les héliums 3 produits au moyen du spectromètre SPES 4 du Laboratoire National Saturne. Les sections efficaces de production du méson ont des valeurs voisines et parfois même supérieures à celles de production du méson π°. Les fonctions d’excitation des deux réactions à θπ, η= 180° (cm) présentent des structures marquées. Aucun des modèles théoriques auxquels nos résultats ont été comparés ne donne une description satisfaisante de ceux-ci. Une interprétation qualitative de nos mesures met en évidence le lien entre les structures observées et l’excitation de résonnances baryoniques N*. Cette excitation pourrait avoir pour origine l’échange d’un méson η virtuel dans l’état intermédiaireThe production of [pi° and eta] mesons in the reactions [pd-> 3 Hepi° and pd-> 3 Heeta] has been studied at very backward angles for proton kinetic energies ranging from 0,92 to 2,6 GeV. The 3 He produced in these experiments were detected with the SPES 4 spectrometer at the labratoire national Saturne
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Blaikley, Helen. "Measurement of the proton structure from 1996 and 1997 radiative ep scattering data using the ZEUS detector." Thesis, University of Oxford, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.301844.
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Vanzella, Daniel Augusto Turolla [UNESP]. "Férmions em referenciais acelerados: desintegração de prótons e outras aplicações." Universidade Estadual Paulista (UNESP), 2001. http://hdl.handle.net/11449/102503.
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vanzella_dat_dr_ift.pdf: 540967 bytes, checksum: c3cbb698d9aaf73242c8a57a6258dfeb (MD5)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
Ao longo desta tese, modelamos alguns processos de Física de Partículas governados pela interação fraca introduzindo, para isso, o conceito de correntes semi-clássicas e acoplando-as a campos quânticos fermiônicos. Dessa maneira, analisamos a influência que a aceleração exerce sobre as desinte- grações de prótons e nêutrons segundo os processos P'SETA'NEPOT.+'''nü'IND.E' e N'SETA'PEPOT.-'''nü'IND.E', respectivamente, assim como descritas por observadores inerciais. Entre outros resultados, obtemos o tempo próprio de vida média de prótons e nêutrons uniformemente acelerados. Embora possa ser desprezada sob condições terrestres, mostramos que a desintegração de prótons acelerados e potencialmente importante em algumas situações astrofísicas. Utilizando técnicas de Teoria Quântica de Campos em Espaços Curvos, analisamos a desintegração de prótons e nêutrons uniformemente acelerados também sob a ótica de observadores co-acelerados. Uma vez assumida a validade do efeito Fulling-Davies-Unruh, conseguimos reconciliar as descrições inercial e co-acelerada para as transições P'SETA'N e N'SETA'P, embora as interpretações em termos de partículas elementares sejam drasticamente distintas. Como veremos, um ingrediente crucial para se obter tal consistência é a existência de partículas massivas livres que violam a equação de energia de Einstein, i.e., partículas livres com massa de repouso m e energia total E< M'CPOT.2', que é um aspecto geral da quantização em espaços curvos e referenciais acelerados. Abordamos, então,a questão da detecção de tais partículas, utilizando, para isso, uma corrente escalar semi-clássica como detector. Por fim, consideramos, utilizando um modelo simplificado, a influência que o campo gravitacional de estrelas de nêutrons pode exercer sobre o processo de neutronização P'Epot.-''SETA''ETA''nüIND.E' que é um...
In the present thesis, we model some weak interaction processes of Particle Physics by defining the concept of semiclassical currents and coupling them to fermionic quantum fields. In this context, we analyze the influence of acceleration on proton and neutron decays due to processes P'SETA'NEPOT.+'''nü'IND.E'and N'SETA'PEPOT.-'''nü'IND.E, respectively, as described by inertial observers. Among other results, we obtain the mean proper lifetime of uniformly accelerated protons and neutrons. Although it can be neglected under Earth conditions, we show that the decay of accelerated protons is potentially important in some astrophysical situations. By using Quantum-Field-Theory-in-Curved-Spacetimes technics, we analyze also the decay of uniformly accelerated protons and neutrons according to coaccelerated observers. Assuming the validity of the Fulling-davies-Unruh effect, we are able to reconcile and coaccelerated descriptions of P'SETA'N e N'SETA'P transitions, even though their elementary particle interpretations are pretty distinct. As we shall see, a crucial ingredient to obtain such consistency is the exixtence of free massive particles which violate the Einstein energy euation, i.e., free particles with mass m E< M'CPOT.2', which is a general feature of quantization in curved spacetimes and accelerated frames. Thus, we analyze the detectability of such particles using a semiclassical sclar current as detectot device. Finally, we consider, using a toy model, the influence of the gravitational field of neutron stars on the neutronization process P'Epot.-''SETA''ETA''nüIND.E' which is an important cooling mechanism...(Complete abstract click electronic access below)
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Cobigo, Yann. "Production de J/[psi] dans les collisions proton-proton et deuton-or à 200 GeV dans le centre de masse nucléon-nucléon." Lyon 1, 2004. http://www.theses.fr/2004LYO10156.
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Pour entreprendre l'étude du plasma de quarks et de gluons formé dans les collisions d'ions lourds ultra-relativistes, il est nécessaire de comprendre le comportement de la matière nucléaire froide. C'est dans cette optique que des collisions deuton-or à 200 GeV dans le centre de masse nucléon-nucléon ont été étudiées au collisionneur RHIC. La résonance J/[psi] est l'une des sondes proposées pour étudier le plasma. Nous avons étudié sa production via le canal de désintégration muonique à l'aide des spectromètres à muons de l'expérience PHENIX. Nous avons développé une méthode d'ajustement des traces et du vertex, basée sur l'algorithme de Kalman, pour analyser les données recueillies dans ces spectromètres. La production de la résonance J/[psi] a été examinée en fonction de différentes variables cinématiques et géométriques. La comparaison aux données recueillies dans les collisions proton-proton permet de mieux comprendre les phénomènes, tel le shadowing ou l'absorption, intervenant dans les collisions où le plasma de quarks et de gluons n'est pas formé
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Liu, Que. "The source and fate of protons in postischemic hearts." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0013/NQ59623.pdf.
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Benjaminsen, Bjørn Eirik. "Nanoflow of Protons and Water in Polymer Electrolyte Membranes." Thesis, Norges Teknisk-Naturvitenskaplige Universitet, 2013. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-20835.
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This master thesis studies the applicability of continuum mean-field theories such as the Poisson-Nernst-Planck equations and the Stokes equation. In particular, we investigate electro-osmotic flow of water and protons in infinite cylindrical nano-scale pores with a uniform surface charge density, representing pores in polymer electrolyte membranes. The impact of different modifications to the continuum theory is explored. Including finite-size ions in the Poisson-Boltzmann equation and spatially dependent profiles for permittivity and viscosity, values are found for the water drag coefficient and the pore conductivity. For surface charge densities sigma_s = -0.1 to sigma_s = -0.5 C m^-2, values of 2-5 are found for the water drag coefficient, compared to 7.5 to 22 for the unmodified equations. Similarly, values for the pore conductivity range from $5.5$-30 S m^-1 when including the modifications, compared to 13-100 S m^-1 for the unmodified equations. A final modification to the Poisson-Boltzmann equations is made by including a field dependent explicit model for the permittivity. This model yields a permittivity profile comparable to predictions based on microscopic simulations, but with a lower permittivity near the wall. The proton concentration exhibits pronounced saturation effects near the wall.
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Lantz, Mattias. "Investigations of Reaction Cross Sections for Protons and 3He." Doctoral thesis, Uppsala universitet, Institutionen för kärn- och partikelfysik, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-5813.
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The reaction cross section gives the probability that a particle will undergo a nonelastic process when passing through a nuclear medium. Therefore reaction cross section data are of importance both for theoretical studies and for applications in such diverse fields as medicine, biology, astrophysics and accelerator-driven transmutation of nuclear waste. There exist many data sets with angular distributions of elastic scattering, but very few measurements of the complementary reaction cross section have been performed. The measurement is in principle simple but has in practice proved to be very difficult to perform, and the relatively limited amount of experimental data displays some serious inconsistencies. Results from measurements of reaction cross sections are presented for: • 3He on 9Be, 12C, 16O, 28Si, 40Ca, 58,60Ni, 112,116,118,120,124Sn and 208Pb at 96, 138 and 167 MeV • protons on 12C, 40Ca, 90Zr and 208Pb at six energies in the energy range 80-180 MeV, and on 58Ni at 81 MeV. Experimental uncertainties were 3-9% for 3He and 1.5-8% for protons. The apparatus and the experimental method used for the measurements of reaction cross sections, using a modified attenuation technique, is described. The detection method enables simultaneous measurements of reaction cross sections for five different sizes of the solid angles in steps from 99.0 to 99.8% of the total solid angle. The final results are obtained by extrapolation to the full solid angle. Experimental results are compared with predictions from optical model calculations using phenomenological global optical potentials. Phenomenological parametrizations of reaction cross sections for scattering of projectiles on targets are presented. The parametrizations show that reaction cross sections are very sensitive to matter distributions at very large radii of both the projectile and the target. For protons the derived relations makes it possible to predict the reaction cross sections on targets for which no experimental data exist.
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Humières, Emmanuel d'. "Accélération de protons par interaction laser-plasma et applications." Paris 6, 2006. http://www.theses.fr/2006PA066047.
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GARDIC, FRANCK. "Etude de l'interaction des protons avec les composants microelectroniques." Paris 6, 1996. http://www.theses.fr/1996PA066155.
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La sensibilite des composants aux protons est etudiee de deux manieres. La premiere methode consiste a irradier les composants aupres d'accelerateurs. Cependant les conditions de tests sont generalement restrictives ne se sont pas representatives d'un environnement reel. Une autre methode, indirecte, consiste a determiner la sensibilite du composant aux ions lourds en fonction de l'energie deposee dans le volume sensible puis a ponderer celle ci par la probabilite qu'une reaction de spallation entraine un tel depot d'energie (spectres de depot d'energie). Cependant, une telle approche est basee sur l'hypothese que les mecanismes de collection de charge dans le cas des protons et des ions lourds restaient les memes. Afin d'etudier ces differents points, l'evolution de la sensibilite de composants electroniques soumis a des flux d'ions lourds et de protons a ete determinee en fonction de la technologie testee (niveau de durcissement, influence des structures parasites), des parametres d'irradiation (energie et angle d'incidence du faisceau) et de fonctionnement (regime statique, dynamique, tension d'alimentation). Les resultats obtenus mettent en evidence la specificite de l'interaction proton silicium, pour des protons d'energie superieure a 100 mev. Nous avons egalement developpe une methode de calcul des spectres de depot d'energie correspondant a des conditions quelconques d'irradiation. Une analyse des spectres en fonction des parametres caracteristiques des composants et des caracteristiques des reactions de spallation est proposee, permettant d'expliquer les resultats experimentaux obtenus. Les resultats experimentaux ainsi que l'etude des spectres de depot d'energie montrent que la notion de volume sensible n'est pas pertinente. Les limites du domaine de validite de la methode d'etude indirecte sont atteintes lorsque les structures bipolaires parasites interviennent de maniere non negligeable dans les phenomenes de collection de charges. Ce resultat est mis en evidence experimentalement. Il a egalement ete etudie par simulation d'un transistor mos de faible longueur de grille: le rapport charge collectee/charge deposee depend fortement des caracteristiques des fragments de spallations ainsi que du point d'emission des fragments. Cette influence des structures parasites ne peut donc etre apprehendee de maniere globale
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Esteves, López Natalia. "Etude du transfert de protons dans les systèmes moléculaires." Thesis, Aix-Marseille, 2017. http://www.theses.fr/2017AIXM0178/document.
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Une des meilleures sources d’énergie verte serait d’être capable de casser une molécule d’eau à partir du rayonnement visible fourni par le soleil, afin de générer du H$_2$. L’eau présente le don d’ubiquité sur terre puisqu’elle est présente, sous ses trois phases, dans les océans, la terre et l’atmosphère. Cependant, une énergie de 6.66 eV (VUV) est nécessaire pour rompre directement une des liaisons covalentes de l’eau. Dans ce travail, nous montrons qu’il est possible de dissocier l’eau si celle-ci est associée à un catalyseur photosensible de nature organique, dont les prototypes absorbent dans l’UV, comme la Pyridine (Py). Un récent travail théorique prédit que la Py peut jouer le rôle de ce photocatalyseur, suivant la réaction : Py-H$_2$O + h$\nu_1 \to$ Py*-H$_2$O $\to$ PyH$\bullet$ + OH$\bullet$Pour tester ce modèle théorique nous avons étudié le complexe Py-eau isolé dans un cluster moléculaire froid. Nous avons caractérisé la spectroscopie électronique du PyH$\bullet$ en phase gazeuse et nous avons mis en évidence cette réaction de photodissociation par irradiation UV de clusters Py-(H$_2$O)$_n$. Nous avons aussi testé ce système en matrices cryogéniques pour évaluer l’effet de la solvatation solide. La dernière étape du processus, la régénération du photocatalyseur par absorption d’un deuxième photon UV (PyH$\bullet$ + h$\nu \to$ Py + H$\bullet$) à été aussi prouvé. Il semblerait que seuls les radicaux PyH$\bullet$ chauds soient capables d’engendrer cette dernière réaction.A l’heure actuelle, nous explorons de nouveaux systèmes moléculaires prototypes susceptibles de conduire au même phénomèneA major challenge to generate green energy from sunlight would be to split water which is a ubiquitous molecule to produce H$_2$. However VUV light (6.66 eV) is needed to dissociate the H-OH covalent bond. In this work we will show that it is possible to dissociate water via photo-sensitisation with UVC light, using a simple organic catalyst.Recently, ab-initio calculations predict that pyridine (Py) can act as a photo-catalyst to split water by absorption of a UV photon, following the reaction:Py-H$_2$O + h$\nu_1 \to$ Py*-H$_2$O $\to$ PyH$\bullet$ + OH$\bullet$ To test this prediction, we studied the Py-H$_2$O complex in isolated cold molecular cluster and the system trapped in cryogenic matrices. We characterized the electronic spectroscopy of the PyH$\bullet$ in the gas phase and we evidenced the reaction through UV excitation of Py-(H$_2$O) $_n$ clusters. We have evidenced that the reaction leads PyH$\bullet$ as photoproduct of the reaction. We also evidenced that the surrounding conditions play an important role in the reaction.We have demonstrated that the UV excitation of Py-water clusters leads to the formation of PyH$\bullet$, thus we have evidenced the water splitting reaction. The last step of the process, that is the regeneration of the catalyst by absorption of a second UV photon (PyH$\bullet$ + h$\nu \to$ Py + H$\bullet$) has been studied and it seems that only hot PyH$\bullet$ molecules are able to follow this channel. In the present, we are studying other aromatic molecules which are expected to lead the photochemical dissociation of water
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Esteves, López Natalia. "Etude du transfert de protons dans les systèmes moléculaires." Electronic Thesis or Diss., Aix-Marseille, 2017. http://www.theses.fr/2017AIXM0178.
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Une des meilleures sources d’énergie verte serait d’être capable de casser une molécule d’eau à partir du rayonnement visible fourni par le soleil, afin de générer du H₂. L’eau présente le don d’ubiquité sur terre puisqu’elle est présente, sous ses trois phases, dans les océans, la terre et l’atmosphère. Cependant, une énergie de 6.66 eV (VUV) est nécessaire pour rompre directement une des liaisons covalentes de l’eau. Dans ce travail, nous montrons qu’il est possible de dissocier l’eau si celle-ci est associée à un catalyseur photosensible de nature organique, dont les prototypes absorbent dans l’UV, comme la Pyridine (Py). Un récent travail théorique prédit que la Py peut jouer le rôle de ce photocatalyseur, suivant la réaction : Py-H₂O + hν₁ → Py*-H₂O → PyH• + OH• Pour tester ce modèle théorique nous avons étudié le complexe Py-eau isolé dans un cluster moléculaire froid. Nous avons caractérisé la spectroscopie électronique du PyH• en phase gazeuse et nous avons mis en évidence cette réaction de photodissociation par irradiation UV de clusters Py-(H₂O)n. Nous avons aussi testé ce système en matrices cryogéniques pour évaluer l’effet de la solvatation solide. La dernière étape du processus, la régénération du photocatalyseur par absorption d’un deuxième photon UV (PyH• + hν → Py + H•) à été aussi prouvé. Il semblerait que seuls les radicaux PyH• chauds soient capables d’engendrer cette dernière réaction. A l’heure actuelle, nous explorons de nouveaux systèmes moléculaires prototypes susceptibles de conduire au même phénomèneA major challenge to generate green energy from sunlight would be to split water which is a ubiquitous molecule to produce H₂. However VUV light (6.66 eV) is needed to dissociate the H-OH covalent bond. In this work we will show that it is possible to dissociate water via photo-sensitisation with UVC light, using a simple organic catalyst.Recently, ab-initio calculations predict that pyridine (Py) can act as a photo-catalyst to split water by absorption of a UV photon, following the reaction: Py-H₂O + hν₁ → Py*-H₂O → PyH• + OH• To test this prediction, we studied the Py-H₂O complex in isolated cold molecular cluster and the system trapped in cryogenic matrices. We characterized the electronic spectroscopy of the PyH• in the gas phase and we evidenced the reaction through UV excitation of Py-(H₂O)n clusters. We have evidenced that the reaction leads PyH• as photoproduct of the reaction. We also evidenced that the surrounding conditions play an important role in the reaction.We have demonstrated that the UV excitation of Py-water clusters leads to the formation of PyH•, thus we have evidenced the water splitting reaction. The last step of the process, that is the regeneration of the catalyst by absorption of a second UV photon (PyH• + hν → Py + H•) has been studied and it seems that only hot PyH• molecules are able to follow this channel. In the present, we are studying other aromatic molecules which are expected to lead the photochemical dissociation of water
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OLIVEIRA, HENRIQUE B. de. "Modelos analiticos para o desenvolvimento de alvos metalicos de alta performance irradiados nos ciclotrons cyclone 30 e cyclone 18 do IPEN-CNEN/SP." reponame:Repositório Institucional do IPEN, 2009. http://repositorio.ipen.br:8080/xmlui/handle/123456789/9494.
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Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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Baccou, Claire. "Initiation de réactions nucléaires par des protons accélérés par laser." Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLX016/document.
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L’avènement des lasers de forte intensité ouvre une nouvelle voie pour la production de réactions nucléaires par laser. En particulier, les impulsions d’intensités supérieures à 10^18 W.cm-2 permettent d’accélérer des faisceaux de protons, et d’ions, caractérisés par un large spectre, une courte durée d’impulsion de l’ordre de la dizaine de picoseconde, un flux (nombre de particules par unité de temps) supérieur de plusieurs ordres de grandeurs aux flux obtenus dans les accélérateurs classiques et des énergies allant jusqu’à plusieurs dizaines de MeV. De telles énergies permettent d’initier des réactions nucléaires ayant des résonances autour de la centaine de keV, telles que la réaction de fusion p-11B qui libère trois particules alpha et ~8,7 MeV, ou encore des réactions à seuil qui produisent des radio-isotopes, utiles pour la médecine nucléaire. Cette thèse a été dédiée au développement d’une plateforme expérimentale sur l’installation laser ELFIE, du LULI (Ecole Polytechnique, France) pour étudier la production de réactions nucléaires dans le cadre du schéma laser suivant : un faisceau de protons est accéléré par laser sur une première cible, par mécanisme TNSA, puis une cible de bore est irradiée par ces protons pour produire les réactions nucléaires. Un second faisceau laser peut être déclenché pour ioniser la cible de bore. Un ensemble de diagnostics complémentaires a été développé pour mesurer et caractériser les produits de réactions. Différents paramètres tels que le flux de protons, le spectre de protons, l’état de la cible de bore (solide ou plasma) ou sa composition, ont été testés afin d’identifier les paramètres physiques qui permettent d’optimiser le nombre de réactions. La compréhension de la physique qui régit la production des réactions nucléaires dans ces conditions est indispensable pour envisager des applications en médecine, ou dans des schémas de fusion pour produire de l’énergieThe recent development of high-intensity laser beams has stimulated the advent of many schemes to produce nuclear reactions by laser. Laser pulses with intensity higher than 1018 W.cm-2 can particularly be used to accelerate proton and ion beams with interesting characteristics such as a broad spectrum, a short duration (~ 10ps), a large number of particles per picosecond and a high energy cut-off, up to tens MeV. Thus, nuclear reactions with resonances close to hundreds keV can be initiated, such as the p-11B fusion reaction which releases 8.7MeV and three alpha particles, or, such as threshold reactions with produce positron emitters, used in nuclear medicine. This thesis was dedicated to the development of an experimental platform at the ELFIE laser facility, at LULI (Ecole Polytechnique, France) to study the production of nuclear reactions using the following scheme: a proton beam is accelerated by the TNSA mechanism on a first target, and sent into a boron target to induce nuclear reactions. A second laser beam can be used to ionize and heat the boron target. A set of complementary diagnostics has been developed to measure and characterize the reaction products. Several parameters such as the proton flux, the proton spectrum, the boron target state (solid or plasma) and its composition were studied in order to identify the physics parameters that optimize the number of reactions. The understanding of the physics that govern the production of reactions in this scheme is necessary to consider applications in medicine or in fusion schemes, to produce energy
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André, Philippe. "Étude et modélisation des effets des protons sur les photopiles Ga Al As (p) / Ga As (n)." Toulouse, ENSAE, 1985. http://www.theses.fr/1985ESAE0011.
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Étude des effets des irradiations par flux de protons, de photopiles en arseniure de gallium dans les circonstances qu'elles peuvent rencontrer en ambiance spatiale. Étude expérimentale: irradiation par des flux de protons de différentes énergies, fluences et répartitions géométriques, puis caractérisation des dégradations. Étude théorique autour de la modélisation du fonctionnement d'une photopile, prenant en compte une répartition géométrique quelconque des défauts dans le matériau. Construction de la distribution de défauts dans le cas d'un flux multidirectionnel.
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Desfontaines, Hervé. "Etude du transport de protons par modes collectifs dans les chaînes à liaisons hydrogènes." Dijon, 1989. http://www.theses.fr/1989DIJOS019.
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Nous avons proposé un modèle discret de chaîne unidimensionnelle à liaisons hydrogènes pour décrire le phénomène de transport de protons dans certains systèmes à liaisons hydrogènes (glace IC, biomembrane,. . . ). Différentes solutions de grande amplitude de ce modèle ont pu être calculées dans la limite des milieux continus. Ce sont des ondes solitaires à deux composantes du type solitons kinks. La stabilité dynamique de ces solutions a été testée par simulations numériques. Celles-ci ont par ailleurs mis particulièrement en évidence, pour certaines vitesses, l'existence d'effets de réseau (ou de discrétisation) liés a l'étroitesse des solutions pouvant se propager dans les différents systèmes à liaisons hydrogènes cités auparavant. Ces effets se matérialisent par l'émission de petites oscillations dans le sillage des solitons kinks. Par la suite, nous avons montré que la réponse du réseau de protons à l'action d'un champ extérieur uniforme en présence ou non d'amortissement présente une non-linéarité et un cycle d'hystérésis (en présence d'amortissement). Ces deux caractéristiques sont amplifiées par une augmentation de l'intensité du couplage proton-oxygène et (ou) une diminution de l'amortissement dans la chaîne (celui-ci modélise l'énergie transférée dans les degrés de liberté exclus de notre modèle 1D). Enfin, nous avons présenté un autre modèle, plus complet, de chaîne a liaisons hydrogènes. Une étude analytique préliminaire a permis de calculer une solution du type soliton kink pour une vitesse particulière d'une part et des solutions du même type dans le cas ou le couplage proton-oxygène n'est plus pris en compte d'autre part. L'étude numérique de la stabilité dynamique de ces solutions débouche sur des résultats qualitativement assez voisins de ceux obtenus pour le modèle précédent. Ceci est encourageant et permet d'envisager une étude plus approfondie de ce modèle avant de
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Steyn, Douw. "Radiative proton capture to second harmonic giant dipole states in ¹³N." Master's thesis, University of Cape Town, 1990. http://hdl.handle.net/11427/17288.
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Bibliography: pages 56-57.Angular distributions have been measured for the radiative proton capture reaction ¹²C(p,ϒ)¹³N at beam energies from 40 to 54 MeV. Measurements were made with the new, large anticoincidence-shielded spectrometer HA GAR at angles from 30° to 150° to the beam direction. Differential and total cross-sections have been calculated from these data, and show evidence for resonant behaviour for the transitions to the ground state, the first excited state, and the unresolved second and third excited states. The total cross-sections for these transitions peak at a proton energy of about 46 MeV which is twice the centroid energy of the Giant Dipole Resonance (GDR) based on the ground state of ¹³N.
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Marchlenski, Donald G. "Helium-three and proton radiative capture studies at intermediate energies /." The Ohio State University, 1987. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487332636475414.
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Silva, Marcelo. "Carga superficial de agregados nanoestruturados." Florianópolis, SC, 2011. http://repositorio.ufsc.br/xmlui/handle/123456789/95447.
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Tese (doutorado) - Universidade Federal de Santa Catarina, Centro de Ciências Físicas e Matemáticas. Programa de Pós-Graduação em Química.Made available in DSpace on 2012-10-26T01:46:30Z (GMT). No. of bitstreams: 1 302711.pdf: 2939867 bytes, checksum: a1796629a3ea85f7577133e33f548d3f (MD5)
A adição de sais em soluções de surfactantes dipolares iônicos promove incorporação específica de ânions nas superfícies das micelas. Essa incorporação gera um caráter aniônico nas micelas que atrai eletrostaticamente íons H3O+ para a superfície micelar. A ordem de incorporação segue a série de Hofmeister e é ClO4- > Br- > Cl- > OH-. Este efeito atualmente é chamado de efeito camaleão. No presente trabalho calculou-se e usou-se o equilíbrio de protonação do 1-naftol (1NOH, pKa* = 2,47 e pKa = 9,33) e 2-naftol (2NOH, pKa* = 2,26 e pKa = 9,71), para investigar mudanças de pH ocorridas em superfícies de agregados micelares nanoestruturados formados por surfactantes dipolares iônicos de 1-propanosulfonato-N-tetradecil-N,N-dimetilamonio (SB3-14). Observou-se mudanças de mais de uma unidade de pH na fase micelar da SB3-14 pela adição de 0,04 M de NaClO4 e, as mudanças foram comparadas com aquelas na presença do surfactante aniônico dodecilsulfato de sódio, SDS. Cálculos teóricos das sondas 1NOH e 2NOH mostram que essas sondas adquirem uma acidez elevada no estado excitado. A reação de transferência de próton entre a sonda 2NOH* (no estado excitado) e diferentes ânions orgânicos como acetato, propionato, formiato, trifluoracetato e perclorato, foi estudada em água. As constantes de velocidades encontradas foram de kPT = 3,8 x 108 M-1 s-1 para os íons acetato, propionato e formiato que são derivados de ácidos com pKa > 2,26 e não observou-se reação para os íons trifluoracetato e ClO4- que possuem pKa(s) < 2,26. Também, foi estudada a reação de transferência de próton no estado excitado entre a sonda 2NOH e o íon acetato em D2O (KPT 2,1 x108 M-1 s-1), mostrando que a reação ocorre com participação de molécula(s) de solvente. Em soluções micelares de SB3-14 obteve-se kPT = 0,99 x 108 M-1 s-1, mostrando que a microviscosidade da micela dificulta as reações de transferência de prótons. Nas reações de transferência de prótons entre o íon H2PO4- e os ácidos 1-naftóico (1COOH) e 2-naftóico (2COOH) obtiveram-se, especificamente para o 2COOH um valor de kPT = 1,77 x 10-8 M-1 s-1, e, para o 1COOH o valor de kPT não foi quantificado, já que a reação procede numa escala de tempo menor que 1-2 nanosegundos (ns).
The addition of salts in zwiterionic micellar solutions promotes specific anion incorporation in the micellar surface. The incorporation results in an anionic character in the micelles which in turn electrostatically attracts ions H3O+ to the micellar surface. The order of incorporation follows the Hofmeister series ClO4-> Br-> Cl-> OH- and this effect is called the chameleon effect. In the present work was calculated the acid dissociation constants of 1-naphthol (1NOH, pKa*= 2.47 and pKa = 9.33) and 2-naphthol (2NOH, pKa* = 2.26 and pKa = pKa 9.71), to investigate changes in pH at the surfaces of nanostructured micellar aggregates formed by the zwiterionic surfactant N-tetradecyl-N,N-dimethylammonio-1-propanesulfonate, SB3-14. Changes of more than one pH unit at the micellar surface of SB3-14 were promoted by addition of 0.04 M NaClO4 and the results were compared with those in the presence of the anionic sodium dodecyl sulfate surfactant (SDS). Theoretical calculations of the probes 1NOH and 2NOH, showed that these probes become highly acidic in the excited state. Proton transfer reaction between the probe 2NOH * (excited state) and various organic anions such as acetate, propionate, formiate, trifluoroacetate and ClO4- were studied in water. The rate constant kPT = 3.8 x 108 M-1 s-1 was found for acetate, propionate and formate anions, all of which have pKa > 2,26 and, no reaction was detected for both trifluoracetate and ClO4-, which have pKa < 2,26. The rate constant for the proton transfer reaction in the excited state between acetate ion and 2NOH in D2O (kPT = 2.1 x108 M-1 s-1) is slower than the rate constant observed in water, showing that this reaction occurs with participation of the solvent. In micellar solutions of SB3-14, kPT = 0.99 x 108 M-1 s-1, showing that the microscopic viscosity of the SB3-14 micelle decreases the rate of the reaction. The proton transfer reaction between 2-naphthoic acid (2COOH) and the H2PO4- ion proceeds with kPT = 1.77 x10-8 M-1 s-1, and that of the 1COOH probe is still faster. The value of kPT could not be quantified because the temporal resolution (1-2 ns) is not sufficient to follow the reaction.
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Auduc, Stéphane. "Mesure de sections efficaces doublement différentielles de production de protons induites par un faisceau de protons de 62,9 MeV sur une cible de 208Pb." Nantes, 2001. http://www.theses.fr/2001NANT2089.
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Dans le contexte actuel du devenir des déchets nucléaires à vie longue, trois axes de recherches ont été mis en place. L'un d'eux concerne la séparation-transmutation des déchets. Ce procédé utilise un réacteur sous-critique alimenté en neutrons par l'intermédiaire d'un accélérateur de protons qui irradie une cible de spallation. Le flux de neutrons résultant entretient la criticité du réacteur et permet, dans le même temps, la transmutation des déchets placés au sein de celui-ci. Pour développer un tel système, de nombreuses études ont lieu. Notre thèse se place dans le cadre des mesures de données nucléaires. La limite supérieure actuelle des bases de données est de 20 MeV mais il est nécessaire de la faire évoluer à 150 MeV. Pour cela, il faut utiliser des codes théoriques qui ont un pouvoir prédictif avéré. Des nouvelles mesures de sections efficaces sont nécessaires afin de mieux contraindre ces codesIn the actual context of long life nuclear waste's future, three ways of research have been decided. One of them is about the separation-transmutation of wastes This process uses a sub-critical reactor feed in neutrons by a proton accelerator which irradiate a spallation target. The neutron flux entertains the reactor criticality and, in the same time, allows the transmutation of the wastes placed inside
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DOLOC, CRISTIAN MIRCEA. "Etude trajectographique de protons thermonucleaires : application a l'interaction entre les protons de fusion et les ondes injectees a la frequence hybride sur tore-supra." Orléans, 1995. http://www.theses.fr/1995ORLE2011.
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Cette these s'inscrit dans le cadre des recherches sur les produits de fusion charges pfc. Elle concretise les resultats de 30 mois de recherches sur le tokamak tore-supra au sein du departement de recherches sur la fusion controlee au cea a cadarache. Ce travail de these se propose comme but principal de mener une etude theorique et experimentale coherente sur la physique des protons de 3 mev, produits de fusion charges issus de la reaction d + d. L'etude du confinement de ces particules est tres liee a la connaissance de leurs trajectoires. Si les methodes experimentales permettent de determiner les caracteristiques d'energie, de flux et de position des pfc perdus par le plasma, la trajectographie de ces particules aide a connaitre leur histoire et donc les divers mecanismes qui agissent sur elles. Le travail experimental a ete effectue sur un des plus grands tokamak actuel en utilisant un systeme de detection des protons a 3 mev. Les recherches experimentales ont mis en evidence un fort phenomene de couplage entre les ondes a la frequence hybride (3. 7 ghz) et les protons thermonucleaires. L'elaboration d'un modele semi-analytique pour la trajectographie des pfc permet de donner une explication qualitative et quantitative au phenomene de couplage onde pfc, mais aussi de developper la classification des trajectoires et des transitions qui peuvent se passer entre elles. Une importance speciale a ete accordee aux transitions entre les divers types de trajectoires: confinees/non confinees, passantes/piegees
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Dieval, Catherine. "The solar wind protons inside the induced magnetosphere of Mars." Licentiate thesis, Luleå tekniska universitet, Rymdteknik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-25726.
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Mars is an unmagnetized planet. Mars has no intrinsic magnetic field but has local magnetic anomalies in the crust. The solar wind, which is the plasma flowing from the Sun at supersonic speed, interacts with the magnetic fields of the currents induced in the conductive Martian ionosphere, deviates and slows down to subsonic speeds. A void in the solar wind is formed around the planet as an induced magnetosphere.At the boundary of the induced magnetosphere, the plasma composition changes from being dominated by the major ion in the solar wind (protons) to being dominated by heavy ions of planetary origin. Also, the interplanetary magnetic field, being carried by the solar wind, starts to pile up against the planet to form a magnetic barrier on the dayside, drapes around the planet, stretches due to mass loading, and forms a magnetotail.The gyroradius of a heated proton in the magnetosheath is large in comparison with the size of the induced magnetosphere. Therefore, a fraction of the proton population penetrates the induced magnetosphere boundary, enters the upper layer of the atmosphere (the ionosphere) and subsequently neutralizes at low altitudes. We have conducted a detailed study of an event, in which the magnetosheath protons penetrate the Martian induced magnetosphere boundary (IMB). The spatial extent of the proton precipitation region reached several thousands of kilometers along the orbit of the Mars Express spacecraft.The interaction of the precipitating protons with the Martian atmosphere was modeled using a direct simulation Monte Carlo method. The inclusion of a horizontal magnetic field in the model significantly increased the backscattering of protons compared to the case without a magnetic field. More than 50% of the incoming energy is reflected backwards for a magnetic field of strength 30 nT, compared to 4% in the case of no magnetic field. We have also used hybrid modeling to study the spatial pattern of the precipitation onto the Martian atmosphere both for solar wind protons and protons originating from the planetary atmosphere. The solar wind protons and the exospheric (planetary) protons contribute 60% and 40%, respectively, of the deposition of mass at the exobase for the given input parameters. The precipitating flux decreases substantially at the subsolar point, due to the backscattering of the incoming protons by the more intense piled-up magnetic field.Godkänd; 2011; 20111101 (catdiv); LICENTIATSEMINARIUM Ämnesområde: Rymdteknik/Space Technology Examinator: Professor Stas Barabash, Institutet för rymdfysik, Kiruna Diskutant: Universitetslektor Maria Hamrin, Umeå universitet Tid: Fredag den 2 december 2011 kl 10.00 Plats: Sal C, Rymdcampus i Kiruna, Luleå tekniska universitet
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Reinhardt, Sabine [Verfasser], and Jörg [Akademischer Betreuer] Schreiber. "Detection of laser–accelerated protons / Sabine Reinhardt. Betreuer: Jörg Schreiber." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2012. http://d-nb.info/1033059692/34.
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Mahon, David Francis. "Deeply virtual compton scattering off longitudinally polarised protons at HERMES." Thesis, University of Glasgow, 2010. http://theses.gla.ac.uk/1924/.
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This thesis details the simultaneous extraction of three polarisation-dependent asymmetries in the distribution of real photons from the e p → e p γ interaction and its indistisguishable deeply virtual Compton scattering and Bethe-Heitler processes at the HERMES fixed-target experiment at Desy. The data analysed were taken using a longitudinally polarised 27.57 GeV positron beam incident on a longitudinally polarised hydrogen gas target. The extracted asymmetries include two single-spin asymmetries A_UL and A_LU which depend on the polarisation of the target and beam respectively, averaged over all other polarisation states. The double-spin asymmetry A_LL dependent on the product of the beam and target polarisations is extracted for the first time. The asymmetry amplitudes extracted relate to combinations of Generalised Parton Distributions (GPDs), predominantly H and Htilde. The extracted amplitudes will be presented across the HERMES kinematic range alongside theoretical predictions from a GPD model based on double distributions. Large sin phi and cos(0phi) amplitudes are observed for A_UL and A_LL respectively, with an unexpectedly large sin(2phi) amplitude for A_UL . The results for the A_UL and A_LL asymmetries are broadly compatible with theory predictions, and the extracted A_LU amplitudes are compatible with HERMES results extracted from a significantly larger data set. It is foreseen that these results will form input to future global data-based GPD models which aim to provide a better understanding of GPDs.
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Hembrador, Sheena (Sheena Marie C. ). "Dosimetry of ¹²⁵Iodine protons for in vivo mouse irradiation study." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/41590.
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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Nuclear Science and Engineering, 2006.Includes bibliographical references (leaf 47).
The biological effects of acute, high doses of radiation are well understood. However, the effects of chronic, low doses are not as clear. Mice irradiation experiments to study the correlation of biological effects with chronic low dose rates are underway in order to make conclusions about the effects of low doses. Yet, in order to do so, the level of dose provided to the animals must be determined. This paper examines methods of ascertaining the dose rate delivered to mice by photons from an 125Iodine filled flood phantom source. Two distinct methods were used. First, Optically Stimulated Luminescence (OSL) Dosimeters were placed in an array over an area slightly larger than the irradiation area. The dose equivalent they each reported was recorded weekly. Secondly, a series of simulations were performed using MCNP to calculate the expected dose equivalent reported by those dosimeters. Comparison of the dosimeters' recorded dose to MCNP's calculated dose showed agreement within experimental and statistical uncertainty for 82% of the measurements. This high level of agreement demonstrates that the MCNP simulation approach produces reliable results. After this was shown, other MCNP simulations were performed to determine the dose equivalent to the mice in cages placed above the 125I filled phantom. The simulation showed an average dose equivalent of 656 t 108 mrem per week, with a range of 866 t 33 mrem/week to 399 t 18 mrem/week. The dosimetry methods developed in this report are not unique to this dose level, and can be used in future mouse studies to determine dose rates at other orders of magnitude.
by Sheena Hembrador.
S.B.
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Van, der Meulen N. P. (Nicolas Philip). "The cyclotron production of selected radionuclides using medium energy protons." Thesis, Stellenbosch : Stellenbosch University, 2008. http://hdl.handle.net/10019.1/21914.
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Thesis (PhD)--Stellenbosch University, 2008.ENGLISH ABSTRACT: Radiochemical research involving ion exchange chromatography is of paramount importance to the future of radionuclide production at the Radionuclide Production Group (RPG) of iThemba LABS. It is required for the production of high-activity yields of radionuclides to effectively remove impurities and for the safety of the operators performing such productions. The radiochemical separations of some new products from their target material, as well as experiments to determine whether production is viable, are described. 67Ga is currently being produced at the RPG and makes use of zinc targets. With the production of ultra-pure 67Ga, it was necessary to remove any Fe(III) impurities from the final product, such that it may be possible to label peptides with this product. The use of Amberchrom CG161M for this purpose was found to be satisfactory. Interest was shown in 88Y by an overseas company for the manufacture of sources. While a method involving extraction of the radionuclide and the ion exchange thereof using Chelex 100 chelating resin had been published, problems with the production persisted. Three methods, using ion exchange chromatography, were devised to produce the radionuclide, with two of them being adopted for production purposes. Thick-target nuclear data have also recently been accumulated in collaboration with colleagues from ATOMKI, Debrecen, Hungary. There is a large demand for 82Sr for the manufacture of 82Sr/82Rb generators for medical use. A method was developed to manufacture this radionuclide with thicker (32 g) target material, bombarded in the Vertical Beam Target Station (VBTS), and to separate 82Sr from its target material with the use of Purolite S950 chelating resin. 68Ge/68Ga generators are becoming increasingly important in the world of radiopharmaceuticals. A project to develop a local generator was funded by the Innovation Fund and research was performed to produce 68Ge, such that the generator could be manufactured. This involved bombarding thicker Ga targets in the VBTS and performing the chemical separation using AG MP-1 anion exchange resin. The final product was loaded onto generators, although tests performed on different materials to the ones being marketed are also reported in this work. A project was initiated to study the cluster radioactive decay of 223Ac via 14C and 15N emission. To produce 223Ac for these observations, a Th target was bombarded. The 227Pa was separated from the target material using AG MP-1 macroporous anion exchange resin and used as a source, which decayed to 223Ac. The chemical separation and the drying of the final product onto a source plate were completed within approximately 70 minutes from the end of bombardment. The work was performed in collaboration with JINR, Russia, and University of Milan and INFN, Italy. 133Ba has a half-life of over 10 years and is an expensive radionuclide to produce. It has been used in medical and biological studies and there still appears to be a demand for it. A method was devised, utilizing AG50W-X4 cation exchange resin, to separate 133Ba from its CsCl target material. Agricultural specialists in the past have shown an interest in 28Mg, to determine the uptake of the element in fruit. It has long been regarded by some of the local researchers as an interesting project to investigate. It has been determined that the product can be produced in reasonable quantities using LiCl target material, with ten targets being bombarded in series using a 200 MeV proton beam delivered by the Separated Sector Cyclotron. A method, involving the use of Purolite S950 chelating resin, was devised to separate 28Mg from its target material.
AFRIKAANSE OPSOMMING: Radiochemiese navorsing, wat ioonuitruiling chromatografie behels, is van uiterste belang vir die toekoms van die produksie van radionukliede by die Radionukliedproduksiegroep (RPG) van iThemba LABS. Dit is nodig vir die hoë aktiwiteit opbrengs van radionuklied produkte om onsuiwerhede te verwyder en vir die veiligheid van die operateurs wat die produksies moet uitvoer. Die skeiding van nuwe produkte van hulle skyfmateriaal, sowel as eksperimente om vas te stel of ‘n produksie uitvoerbaar is, word in die werk beskryf. 67Ga word tans by RPG vervaardig en maak gebruik van sink as skyfmateriaal. Vir die produksie van “ultra-suiwer” 67Ga was dit belangrik om enige Fe(III) onsuiwerhede uit die finale produk te verwyder om sodoende peptiede merking te kan uitvoer. Die gebruik van Amberchrom CG161M hars was voldoende vir dié eksperiment. ‘n Oorsese maatskappy het belangstelling getoon in 88Y vir die vervaardiging van bronne. Alhoewel ‘n metode wat die ekstraksie van die radionuklied en die ioonuitruiling daarvan met die gebruik van Chelex 100 chelerende hars reeds gepubliseer was, het probleme met die produksie voortgeduur. Drie metodes is opgestel om 88Y te produseer, waarvan twee van die metodes tans gebruik word vir produksie doeleindes. Dik-skyf kerndata is ook versamel in samewerking met kollegas van ATOMKI, Debrecen, Hongarye. Daar is ‘n groot aanvraag vir 82Sr vir die vervaardiging van 82Sr/82Rb generators vir mediese doeleindes. ‘n Metode is ontwikkel om die radionuklied te vervaardig van dikker skyfmateriaal (32 g), in die Vertikale Bundelstasie gebombardeer, en om 82Sr van sy skyfmateriaal te skei met die gebruik van Purolite S950 chelerende hars. 68Ge/68Ga generators is besig om toenemend belangrik te word in die wêreld van radiofarmasie. iThemba LABS kry baie navrae om die produk te vervaardig. Die projek was ook deel van die voorlegging aan die “Innovation Fund” en ‘n manier is ondersoek om 68Ge te vervaardig, wat benodig word om so ‘n generator te laai. Dik Ga skyfmateriaal word in die Vertikale Bundelstasie gebombardeer en ‘n chemiese skeiding is uitgevoer deur gebruik te maak van AG MP-1 anioonuitruiling hars. Die finale produk is op die generators gelaai vir toetsdoeleindes. Toetse is ook op ‘n ander tipe generator uitgevoer en word in die werk beskryf. ‘n Projek is begin om “cluster” radioaktiewe verval van 223Ac, via 14C en 15N emissie, te bestudeer. ‘n Th-skyf is met protone gebombardeer om die 223Ac te produseer vir die eksperiment. 227Pa is vervaardig en geskei van die skyfmateriaal. Dit is gedoen met die gebruik van AG MP-1 makroporeuse anioonuitruiling hars en drooggemaak op ‘n bronplaat, waar dit verval het na 223Ac. Die chemiese skeiding en die droogmaak van die finale produk op ‘n bronplaat is uitgevoer binne 70 minute na Einde van Bombardering (EVB). Die werk is deel van ‘n samewerking met kollegas van JINR, Rusland, en die Universiteit van Milaan, sowel as INFN, Italië. 133Ba het ‘n halveertyd van oor die tien jaar en is ‘n duur produk om te vervaardig. Dit is al gebruik in mediese en biologiese studies en daar is deesdae ‘n redelike aanvraag daarvoor. ‘n Metode is uitgewerk om 133Ba te skei van die CsCl skyfmateriaal met die gebruik van AG50W-X4 katioonuitruiling hars. Spesialiste in landboustudies het in die verlede belangstelling getoon in 28Mg. Dit word gebruik om die absorpsie van dié element in vrugte te ondersoek. Die produk kan vervaardig word met die gebruik van LiCl skyfmateriaal: tot soveel as tien skywe (agter mekaar) word gebombardeer met ‘n 200 MeV protonbundel te iThemba LABS. ‘n Metode, wat Purolite S950 behels, is daargestel om 28Mg van die skyfmateriaal te skei.
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Moison, Jean-Marie. "Contribution à l'étude des semiconducteurs par photoémission à deux protons." Paris 11, 1985. http://www.theses.fr/1985PA112130.
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Ce travail présente une validation de la photoémission à deux photons pour l’étude de la bande de conduction des semiconducteurs et de la dynamique des électrons dans les états vides. Cette technique consiste à peupler ceux-ci optiquement, et à sonder la population excitée par photoémission dans son retour vers l’équilibre. Le flux d’électrons est alors proportionnel au carré du flux de photons, via un « rendement » caractéristique. La faiblesse de celui-ci impose une excitation pulsée très intense et oblige à maîtriser divers phénomènes (dégradation, échauffement, perturbation de la structure de bandes,…). Par ailleurs, la structure électronique des surfaces – Si (111) et InP (100) – (niveaux de Fermi et du vide, états de surface…) doit être déterminée in-situ, vu son importance pour l’interprétation des données. La loi quadratique de flux est alors vérifiée et le rendement, son spectre, et les distributions énergétiques et angulaires de photoélectrons associés sont obtenus. Divers mécanismes possibles sont discutés sur la base du modèle à étapes de la photoémission pour conclure que le mécanisme observé est bien celui décrit plus haut. On peut observer les électrons juste après leur excitation (« balistiques ») ou après leur relaxation dans une vallée latérale, ce qui fournit des renseignements sur la structure de la bande de conduction, les densités d’états et les durées de vie associées. L’influence de l’état de la surface de ces durées met en évidence des mécanismes de relaxation depuis la vallée latérale localisés en surface. Des mesures de photoluminescence permettent de corréler ceux-ci aux mécanismes de recombinaison localisés en surfaceWe present here a quantitative evaluation of two-photon photoemission as a probe for the conduction band of semiconductors and the dynamics of electrons in empty states. These states are populated optically, and the excited population is probed by photoemission along its return to equilibrium. The photoelectron flux is here proportional to the square of the photon flux, via a “two-photon yield”. Because of its very low value, the excitation must be provided by high-intensity pulsed lasers and many parasitic phenomena (optical damage, heating, band filling…) had to be evaluated and avoided. Because of its incidence on data interpretation, the electronic structure (Fermi level, vacuum level, surface states, etc) of the surfaces under study, (111)Si and (100)InP, has also been determined in-situ. The quadratic flux law is then clearly checked, and the yield, its variation with photon energy, and the related energy and angular distributions of the photoelectrons are obtained. The microscopic process is discussed on the basis of the “three-step-model” oh photoemission. It is concluded that the actual process is indeed a succession of two optical absorptions which excite then probe an electron population in the conduction band. This population is observed either just after its excitation (“ballistic” electrons) or after its relaxation in a lateral valley, which yields information on the structure of the conduction band and the related densities of states and lifetimes. The influence of the state of the surface on these data reveals processes involving relaxations out of the lateral valley localized at the surface. These processes are correlated to the surface-localized recombination processes which are determined by parallel photoluminescence studies
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MEDDAHI, MALIKA. "Effets faisceau-faisceau dans le collisionneur protons-antiprotons du sps." Paris 7, 1991. http://www.theses.fr/1991PA077062.
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Au cern, une etude experimentale, theorique et numerique a ete developpee pour le collisionneur protons-antiprotons du sps afin d'etudier les pertes de particules sur les resonances d'ordre eleve. Les interactions faisceau-faisceau generent en effet une excitation des resonances d'ordre eleve et une dispersion des nombres d'ondes. Cette dispersion, qui doit etre precisement connue pour confiner les particules entre les valeurs resonnantes des nombres d'ondes, a ete calculee dans les deux plans transverses pour des faisceaux non-ronds. Le role de la taille respective des deux faisceaux dans la force de l'interaction faisceau-faisceau a ete etudie experimentalement, ainsi que le processus de diffusion des particules. Il a ete ainsi prouve que la dispersion lineaire des frequences betatron n'etait plus un parametre suffisant pour quantifier la force de l'interaction faisceau-faisceau quand les faisceaux ont des tailles differentes. Une explication etroitement liee aux forces de resonance a ete developpee. Une simulation numerique a alors permis de completer l'etude de ces phenomenes de resonance et de diffusion. En appliquant une modulation du nombre d'ondes, on etudie les phenomenes responsables de la diffusion des particules (capture par resonance et formation de bandes stochastiques) en fonction de differents parametres comme la frequence et l'amplitude de la modulation. Si a une dimension, seul le phenomene de capture par resonance est important, a deux dimensions, les deux phenomenes conduisent a des pertes de particules
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Cadet, Ponce Laurette. "Diagnostic par rayonnement synchrotron des faisceaux de protons du LHC." Grenoble INPG, 2002. http://www.theses.fr/2002INPG0093.
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Pour réaliser le diagnostic transverse des faisceaux de protons du LHC, il est prévu d'utiliser un moniteur de lumière synchrotron. Afin d'optimiser les performances sur toute la gamme d'énergie du LCH (de 450 GeV à 7 TeV), une étude comparative des différents types de source a été entreprise. Tout d'abord basée sur des modèles analytiques permettant de déterminer la densité spectrale angulaire d'énergie émise par ces sources, puis sur des méthodes de calcul simplificatrices comme le modèle basse fréquence ou le calcul d'interférences entre sources, l'étude s'est prolongée par des simulations numériques pour évaluer les performances de sources proches des conditions réelles d'utilisation. Les résultats obtenus ont permis de proposer l'installation d'un onduleur supraconducteur, constitué de deux périodes de 28 cm et combiné à un dipôle de séparation pour permettre de mesurer des profils sur toute la gamme d'énergie. Enfin, l'évaluation des performances du moniteur est complétée par une analyse détaille du système optique. Les composants du télescope sont décrits de façon à évaluer le seuils de détection, puis les effets de diffraction et de profondeur de champ qui constituent les limites de résolution du système ont été étudiés numériquement. L'ensemble des résultats a permis d'aboutir à la construction d'un moniteur de rayonnement synchrotron permettant de satisfaire aux exigences du diagnostic des faisceaux du LHC.
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Poquet, Sandrine. "Un nouvel inhibiteur de la pompe à protons : le prantoprazole." Bordeaux 2, 1998. http://www.theses.fr/1998BOR2P047.
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Kozarev, Kamen Asenov. "Coronal shock acceleration and heliospheric transport of solar energetic protons." Thesis, Boston University, 2013. https://hdl.handle.net/2144/12799.
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Thesis (Ph.D.)--Boston University
PLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis or dissertation. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at open-help@bu.edu. Thank you.Solar flares and coronal mass ejections (CME) in the Sun's atmosphere produce highly energetic charged particles during violent bursts of activity. Protons, the most numerous and important species of these solar energetic particles (SEP), accelerate and propagate throughout the heliosphere, probing the interplanetary transport conditions. They also present a significant radiation hazard to space operations. Nevertheless, SEP acceleration in the low corona is currently not well constrained and poorly understood. In this dissertation, I examine off-limb extreme ultraviolet (EUV) wave dynamics between 1.3 and 2.0 solar radii in the corona, and I show that the EUV signatures are consistent with CME-driven shocks. Therefore, such shocks may form very low in the corona. I also develop a data-driven model for estimating the maximum energy to which protons may be accelerated in coronal shocks. I apply it to an observed shock and show that it may accelerate protons up to tens of MeV during its fast coronal passage, consistent with in-situ observations. To explore further coronal SEP acceleration by CME-driven shocks, I modify a global, 3D numerical model for interplanetary SEP transport for the coronal conditions, and adapt it to incorporate results from a realistic magnetohydrodynamic coronal and CME model. Furthermore, I apply a diffusive shock acceleration model, which explicitly treats proton energization at traveling shocks, to an MHD simulation of a real CME event. I find that the source population becomes strongly accelerated. In addition, I simulate the proton transport between the Sun and Earth, and find that the modeled fluxes are consistent with particle observations near Earth. Results suggest that CME-driven shocks in the corona may be the primary source of SEPs in solar storms. In addition, conditions along coronal shock fronts vary greatly, influencing the amount of acceleration. Finally, I model the global proton transport between Earth and 5 AU during a very large SEP event. I obtain radial gradients of peak fluxes and radiation doses for space weather applications, and I find that simulated and observed fluxes agree reasonably well. This suggests that most CME shocks are not efficient proton accelerators beyond 1 AU.
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Zerguerras, Thomas. "Etude de l'emission proton et de deux protons dans les noyaux légers déficients en neutrons de la région A=20." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2001. http://tel.archives-ouvertes.fr/tel-00002692.
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L'émission proton et de deux protons par des noyaux légers, déficients en neutrons, dans la région de masse A=20 a été étudiée. Un faisceau radioactif, constitué de 18Ne, 17F et de 20Mg a été produit au Grand Accélérateur National d'Ions Lourds, par fragmentation d'un faisceau primaire de 24Mg à 95MeV/A, et bombardait une cible de 9Be afin de former des états non liés. Le(s) proton(s) et le noyau issus de la décroissance étaient détectés dans l'ensemble MUST et le spectromètre SPEG, leurs énergies et angles d'émission mesurés pour reconstruire la masse invariante du noyau père.Les événements de coïncidence double entre un proton et les noyaux 17F, 16O, 15O, 14O et 18Ne ont été étudiés pour reconstruire les spectres en énergie d'excitation de 18Ne, 17F, 16F, 15F et 19Na. Les masses mesurées sont généralement en bon accord avec les résultats obtenus lors de précédentes expériences. Pour le noyau 18Ne, les distributions angulaires et en énergie d'excitation sont en bon accord avec un modèle de break up. A partir des coïncidences entre un proton et 17Ne, une première mesure expérimentale de l'excès de masse de l'état fondamental de 18Na donne 24,19(0,15)MeV.
L'émission de deux protons depuis des états excités de 17Ne et 18Ne, ainsi que depuis l'état fondamental de 19Mg, a été étudiée à partir des événements de coïncidences entre deux protons et respectivement 15O, 16O et 17Ne. Dans le premier cas, la distribution en angle relatif des deux protons dans le centre de masse a été comparée aux résultats de simulation. L'émission séquentielle depuis un état excité de 17Ne, au-dessus du seuil d'émission proton, via 16F, domine mais une contribution d'émission 2He ne peut pas être exclue. Aucune émission 2He depuis l'état à 1,288MeV de 17Ne ni depuis celui à 6,15MeV dans 18Ne, n'a été observée. Un seul événement de coïncidence entre 17Ne et deux protons a pu être enregistré car la section efficace de la réaction de stripping d'un neutron de 20Mg est plus faible que prévu.
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ZERGUERRAS, THOMAS. "Etude de l'emission proton et de deux protons dans les noyaux legers deficients en neutrons de la region a=20." Paris 6, 2001. http://www.theses.fr/2001PA066252.
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L'emission proton et de deux protons par des noyaux legers, deficients en neutrons, dans la region de masse a=20 a ete etudiee. Un faisceau radioactif, constitue de 1 8ne, 1 7f et de 2 0mg a ete produit au grand accelerateur national d'ions lourds, par fragmentation d'un faisceau primaire de 2 4mg a 95mev/a, et bombardait une cible de 9be afin de former des etats non lies. Le(s) protons et le noyau issus de la decroissance etaient detectes dans l'ensemble must et le spectrometre speg, leurs energies et angles d'emission mesures pour reconstruire la masse invariante du noyau pere. Les evenements de coincidence double entre un proton et les noyaux 1 7f, 1 6o, 1 5o, 1 4o et 1 8ne ont ete etudies pour reconstruire les spectres en energie d'excitation de 1 8ne, 1 7f, 1 6f, 1 5f et 1 9na. Les masses mesurees sont generalement en bon accord avec les resultats obtenus lors de precedentes experiences. Pour le noyau 1 8ne, les distributions angulaires et en energie d'excitation sont en bon accord avec un modele de break up. A partir des coincidences entre un proton et 1 7ne, une premiere mesure experimentale de l'exces de masse de l'etat fondamental de 1 8na donne 24,19(0,15)mev. L'emission de deux protons depuis des etats excites de 1 7ne et 1 8ne, ainsi que depuis l'etat fondamental de 1 9mg, a ete etudiee a partir des evenements de coincidences entre deux protons et 1 5o, 1 6o et 1 7ne. Dans le premier cas, la distribution en angle relatif des deux protons dans le centre de masse a ete comparee aux resultats de simulation. L'emission sequentielle depuis un etat excite de 1 7ne, au-dessus du seuil d'emission proton, via 1 6f, domine mais une contribution d'emission 2he ne peut pas etre exclue. Aucune emission 2he depuis l'etat a 1,288mev de 1 7ne ni depuis celui a 6,15mev dans 1 8ne, n'a ete observee. Un seul evenement de coincidence entre 1 7ne et deux protons a pu etre enregistre car la section efficace de la reaction de stripping d'un neutron de 2 0mg est plus faible que prevu.