Dissertations / Theses on the topic 'Electron rays'
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Prade, H. "Workshop on X-rays from electron beams." Forschungszentrum Dresden, 2010. http://nbn-resolving.de/urn:nbn:de:bsz:d120-qucosa-30011.
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Prade, H. "Workshop on X-rays from electron beams." Forschungszentrum Rossendorf, 2000. https://hzdr.qucosa.de/id/qucosa%3A21828.
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Nilsson, Daniel. "Zone Plates for Hard X-Ray Free-Electron Lasers." Doctoral thesis, KTH, Biomedicinsk fysik och röntgenfysik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-122161.
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Hard x-ray free-electron lasers are novel sources of coherent x-rays with unprecedented brightness and very short pulses. The radiation from these sources enables a wide range of new experiments that were not possible with previous x-ray sources. Many of these experiments require the possibility to focus the intense x-ray beam onto small samples. This Thesis investigates the possibility to use diffractive zone plate optics to focus the radiation from hard x-ray free-electron lasers. The challenge for any optical element at free-electron laser sources is that the intensity in a single short pulses is high enough to potentially damage the optics. This is especially troublesome for zone plates, which are typically made of high Z elements that absorb a large part of the incident radiation. The first part of the Thesis is dedicated to simulations, where the temperature behavior of zone plates exposed to hard x-ray free-electron laser radiation is investigated. It is found that the temperature increase in a single pulse is several hundred Kelvin but still below the melting point of classical zone plate materials, such as gold, tungsten, and iridium. Even though the temperature increases are not high enough to melt a zone plate it is possible that stresses and strains caused by thermal expansion can damage the zone plate. This is first investigated in an experiment where tungsten gratings on diamond substrates are heated to high temperatures by a pulsed visible laser. It is found that the gratings are not damaged by the expected temperature fluctuations at free-electron lasers. Finally, a set of tungsten zone plates are tested at the Linac Coherent Light Source where they are exposed to a large number of pulses at varying fluence levels in a prefocused beam. Damage is only observed at fluence levels above those typically found in an unfocused x-ray free-electron laser beam. At higher fluences an alternative is to use a diamond zone plate, which has significantly less absorption and should be able to survive much higher fluence. Damage in diamond structures is investigated during the same experiment, but due to a remaining tungsten etch mask on top of the diamond the results are difficult to interpret. Additionally, we also demonstrate how the classical Ronchi test can be used to measure aberrations in focusing optics at an x-ray free-electron laser in a single pulse. The main result of this Thesis is that tungsten zone plates on diamond substrates can be used at hard x-ray free-electron laser sources.QC 20130514
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Chandril, Sandeep. "In situ structural and compositional analysis using RHEED electrons induced x-rays." Morgantown, W. Va. : [West Virginia University Libraries], 2009. http://hdl.handle.net/10450/10641.
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Thesis (Ph. D.)--West Virginia University, 2009.Title from document title page. Document formatted into pages; contains ix, 97 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 95-97).
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Chighvinadze, Tamar. "A spectroscopic Compton scattering reconstruction algorithm for 2D cross-sectional view of breast CT geometry." Journal of X-Ray Science and Technology, IOS press, 2014. http://hdl.handle.net/1993/23846.
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X-ray imaging exams are widely used procedures in medical diagnosis. Whenever an x-ray imaging procedure is performed, it is accompanied by scattered radiation. Scatter is a significant contributor to the degradation of image quality in breast CT. This work uses our understanding of the physics of Compton scattering to overcome the reduction in image quality that typically results from scattered radiation. By measuring the energy of the scattered photons at various locations about the object, an electron density (ρe) image of the object can be obtained.
This work investigates a system modeled using a 2D cross-sectional view of a breast CT geometry. The ρe images can be obtained using filtered backprojection over isogonic curves. If the detector has ideal energy and spatial resolution, a single projection will enable a high quality image to be reconstructed. However, these ideal characteristics cannot be achieved in practice and as the detector size and energy resolution diverge from the ideal, the image quality degrades. To compensate for the realistic detector specifications a multi-projection Compton scatter tomography (MPCST) approach was introduced. In this approach an x-ray source and an array of energy sensitive photon counting detectors located just outside the edge of the incident fan-beam, rotate around the object while acquiring scattering data. The ρe image quality is affected by the size of the detector, the energy resolution of the detector and the number of projections. These parameters, their tradeoffs and the methods for the image quality improvement were investigated.
The work has shown that increasing the energy and spatial resolution of the detector improves the spatial resolution of the reconstructed ρe image. These changes in the size and energy resolution result in an increase in the noise. Thus optimizing the image quality becomes a tradeoff between blurring and noise. We established that a suitable balance is achieved with a 500 eV energy resolution and 2×2 mm2 detector. We have also established that using a multi-projection approach can offset the increase in the noise.
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Chen, Hai Ph D. Massachusetts Institute of Technology. "Precision measurement of electron and positron flux in cosmic rays with the AMS-02 Detector." Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/103243.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Physics, 2016.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 159-169).
The cosmic ray electron and positron flux measurement can address a series of astrophysics and particle physics questions. This thesis presents an analysis of electron and positron flux from 0.5 GeV to 1 TeV using the first 30 months of data taking( over 41 billion events), with the AMS-02 detector on the International Space Station(ISS) 330-410 km above earth. A precise calibration of the Electromagnetic Calorimeter(ECAL) signals is performed to obtain stable energy measurement. A reconstruction algorithm for electromagnetic showers is implemented to measure energy and achieve high particle identification accuracy of electron and positron separating them from the proton background. The result of combined electron and positron flux measurement shows a smooth spectrum with no sharp structure. The spectral index ... above 30 GeV is observed to be ... (energy scale). This provides precise measurement for cosmic ray electrons and positrons and can contribute to probing the origin of cosmic rays, informing the studies of new physics..
by Hai Chen.
Ph. D.
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Checchia, Caterina. "Study of cosmic-ray light nuclei on the ISS: identification of the interaction point in the CALorimetric Electron Telescope (CALET)." Doctoral thesis, Università di Siena, 2018. http://hdl.handle.net/11365/1054668.
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At present, Astro-particle Physics is one of the most interesting and alive fields in experimental physics. Direct measurements of cosmic rays will help answering many open questions about the sources and the processes of acceleration and propagation in the interstellar medium of high-energy particles (from GeV to PeV energy scale). For example, the measurement of both light and heavy nuclei spectra and their relative abundances for energies of tens of TeV/nucleon is one of the main topic to understand acceleration and propagation mechanisms in our Galaxy.
The CALorimetric Electron Telescope (CALET) is a Japanese-led international space mission by JAXA (Japanese Aerospace Agency) in collaboration with the Italian Space Agency (ASI) and NASA, designed to perform precise measurements of high energy cosmic rays. CALET reached the ISS on August 24th , 2015 and started a campaign of scientific observations on October 13th the same year. After the first two-year period of the mission, an extension has been approved for additional three years.
The broad scientific program of this space-based experiment includes many topics: the detection of possible nearby sources of high energy electrons; searches for signatures of dark matter in the spectra of electrons and γ rays; monitoring gamma-ray transients and solar modulation; long exposure observations of cosmic nuclei from proton to iron and trans-iron elements; measurements of the cosmic-ray relative abundances and secondary-to-primary ratios. The detector is composed by a Total Absorption Shower Calorimeter (TASC), an homogeneous calorimeter with a thickness of 27 radiation length (corresponding to 1.2 interaction length), a sampling IMaging Calorimeter (IMC) that adds 3 radiation length to the total thickness of the instrument and a CHarge Detector (CHD) for the identification of nuclear species in a wide dynamic range up to Z=40. The TASC detector has the function of measuring all the energy deposited by crossing particles. The IMC with its fine granularity allows for the reconstruction of the incident direction of particles with high angular resolution.
This thesis illustrates the study on light nuclear components (such as protons and helium nuclei) with the aim to reconstruct the interaction vertex in the CALET detector. In addition to a previously developed algorithm for the reconstruction of the interaction point inside the IMC, a completely new one has been developed and tested for the TASC detector. Knowing with high precision the starting point of a shower inside the IMC detector is of fundamental importance for the CALET experiment because it allows for a redundant measurement of the charge of incoming particles with the IMC detector, in addition to the independent one provided by the CHD. Studying instead the interaction taking place in the depth of the TASC can help to understand whether those events have to be taken into account for flux measurements.
The first chapter of this thesis is dedicated to a review of cosmic-ray physics with particular attention to acceleration and propagation mechanisms. Chapter 2 describes the CALET detector in detail, summarizes the architecture of the trigger system, provides the acceptance definition, and underlines the expected performance of the CHD detector, the electron/proton separation and the tracking reconstruction. Chapter 3 introduces the main scientific objectives of the CALET mission anticipating the expected measurements after five years of data taking. The original work of this thesis is described in chapters 4 and 5. The former contains the description of the interaction point reconstruction inside CALET while the latter shows how the potentiality of the algorithm can be exploited to observe energy deposits inside the TASC detector. Last, chapter 6 summarizes the results obtained by CALET after two years of data taking.
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Petersen, Timothy W. "Tabletop internal source ensemble x ray holography /." Thesis, Connect to this title online; UW restricted, 1997. http://hdl.handle.net/1773/9747.
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Reppart, William J. "Magnetic and crystallographic investigations of selected single crystal systems /." The Ohio State University, 1985. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487262513407635.
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Snavely, Richard Adolph. "Physics of laser driven relativistic plasmas, energetic X-rays, proton beams and relativistic electron transport in Petawatt laser experiments /." For electronic version search Digital dissertations database. Restricted to UC campuses. Access is free to UC campus dissertations, 2003. http://uclibs.org/PID/11984.
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You, Yan. "Pulsed Laser Injected Enhancement Cavity for Laser-electron Interaction." Phd thesis, Université Paris Sud - Paris XI, 2014. http://tel.archives-ouvertes.fr/tel-01011958.
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X-ray diffraction and scattering, X-ray spectroscopy, and X-ray crystallography are widely used in the life sciences, material science, and medical diagnosis. High-quality and high-brightness X-rays are a strong requirement to improve applications. Inverse Compton scattering (ICS) X-ray source has attracted great interests worldwide lately. To significantly enhance the average X-ray photon flux, a compact electron storage-ring combined with a high finesse optical enhancement cavity (OEC) can be utilized. In such a system, the collision rate between the electron beam and the laser pulse is greatly increased to the MHz range, enabling a photon flux up to 10¹³ph/s.In the first chapter, I describe the motivation behind the development of OEC based on ICS X-ray source. The characteristics of this kind of X-ray source are summarized, compared to those of the conventional low-repetition-rate Terawatt laser system based on ICS X-ray source. The latest progress and research status of OEC based on ICS X-ray source are presented. Pulsed-laser injected high-finesse OEC stacking theory and properties are discussed in Chapter 2. Not only does the OEC based on ICS X-ray source require the laser pulse repetition rate to be matched to the free spectral range (FSR) of the cavity, where both also have to match the electron storage-ring circulation frequency. In addition, we have to match the phase shift of the laser repetition rate to the phase offset introduced by the dispersion of the cavity mirrors, since our cavity finesse design value is quite high. The stacking theory is analyzed in the frequency domain. Cavity properties, including cavity mirror dispersion, finesse, and FSR, are discussed in detail. A laser frequency comb and OEC coupling is analyzed also. The laser source development is presented in Chapter 3. We constructed a mode-locked fiber laser based on nonlinear polarization rotation. The locking model, locking techniques, and the theory, simulations and experimental tests of tilt locking (TL) in the pulsed laser injected high-finesse OEC are discussed in Chapter 4. We succeeded in locking a pulsed laser to a high-finesse cavity with the TL technique. The experimental results show that the TL and the Pound-Drever-Hall techniques have the same performance: stable locking, high sensitivity, and the same power coupling rate for picosecond laser pulse case, while the test results for full spectrum TL locking show that it is uneasy to align the split-photodiode to the beam waist.Based on the above experimental study and tests, we design the OEC system for Tsinghua University X-ray project in Chapter 5. The expected X-ray flux is 10¹º to 10¹³ ph/s. We detail every subsystem requirement.
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Shabani, Juvet Malonda. "Synthesis of clay-based catalysts for bioethanol conversion." Thesis, Cape Peninsula University of Technology, 2016. http://hdl.handle.net/20.500.11838/2488.
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Thesis (MTech (Chemical Engineering))--Cape Peninsula University of Technology, 2016.For decades, clays have been applicable as commercial catalysts mostly for cracking in petroleum industries. Clays are also used for development of useful catalysts for various other industrial applications. Hence, this work was aimed to synthesize clay-based catalysts from clay minerals (Kaolin, bentonite and talc) that will be active for the conversion of bioethanol to fuel hydrocarbons. Catalyst characterisation techniques employed on the samples produced in this work include the Energy Dispersive Spectroscopy (EDS), Scanning Electron Microscopy (SEM) and the X-Ray Diffraction pattern (XRD). All catalytic reactions were carried out in a fixed bed reactor (at fixed reaction condition of 6 hour and 350 ⁰C) and corresponding reaction products (liquid and gaseous) were analysed through a Gas Chromatograph- Flame Ionisation Detector (GC-FID) and Gas Chromatograph Mass Spectrometer (GC/MS). The activity of clays in their non-modified state was studied and they were all found active for bioethanol conversion to hydrocarbons. Bentonite was the most active catalyst with bioethanol of 84.95 % and this through subsequent beneficiation and acid-modification approach, led to increased bioethanol conversion of 87.3 %. EDS/SEM characterisation of the catalyst in line to the above modification and increased catalyst activity, revealed that the structural morphology of bentonite and the concentration of basic structural elements (in terms of Si/Al ratio) was increased.
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Voigt, Bernhard. "Sensitivity of the IceCube detector for ultra-high energy electron-neutrino events." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2008. http://dx.doi.org/10.18452/15850.
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Zur Zeit wird das IceCube Neutrino-Teleskop am Südpol im Eis der Antarktis installiert, die Hälfte des Detektors ist bereits im Betrieb. Bei Fertigstellung im Jahr 2011 wird mehr als 1 km^3 Eis mit Photovervielfachern instrumentiert sein. IceCube bietet damit eine einzigartige Möglichkeit, die Quellen der kosmischen Strahlung mit Hilfe hochenergetischer Neutrinos zu finden. Im Rahmen dieser Arbeit wurde die Sensitivität des kompletten Icecube Detektors für den Nachweis eines diffusen Flusses von Elektronneutrinos bestimmt. Ziel war es, die Eigenschaften des Detektors für Energien oberhalb von einem PeV zu bestimmen. Besonderes Augenmerk wurde dabei auf die Simulation von elektromagnetischen Kaskaden gelegt, die in Neutrino-Nukleon-Wechselwirkungen auftreten. Da existierende Parametrisierungen die Unterdrückung der Wechselwirkungsquerschnitte durch den LPM-Effekt nicht beinhalten, wurde eine Simulation des Energieverlustes von elektromagnetischen Kaskaden für Energien oberhalb von 1 PeV entwickelt, die entsprechend modifizierte Wirkungsquerschnitte verwendet. Die Analyse, die in dieser Arbeit vorgestellt wird, nutzt die komplette Information des durch einen Photovervielfacher aufgezeichneten Ladungsverlaufes aus, die mit der Datennahme des IceCube Detektors zur Verfügung steht. Es werden neue Methoden entwickelt, um zwischen atmosphärischen Myonen-Hintergrund- und Signalereignissen von Kaskaden aus Neutrino-Nukleon-Wechselwirkungen zu unterscheiden. Die erreichbare Sensitivität innerhalb einer Laufzeit von einem Jahr ist 1.5*10^-8 E^-2 GeV/(cm^2 sr s) in einem Energiebereich von 16 TeV bis 13 PeV für den Nachweis von Elektronneutrinos eines diffusen Flusses. Eine Verbesserung von mindestens einer Größenordnung wird erwartet, wenn alle Neutrinofamilien in die Analyse einbezogen werden. Damit sollte eine Sensitivität erreicht werden, die auf dem gleichen Niveau einer diffusen Myonenanalyse liegt.IceCube is a neutrino telescope currently under construction in the glacial ice at South Pole. At the moment half of the detector is installed, when completed it will instrument 1 km^3 of ice providing a unique experimental setup to detect high energy neutrinos from astrophysical sources. In this work the sensitivity of the complete IceCube detector for a diffuse electron-neutrino flux is analyzed, with a focus on energies above 1 PeV. Emphasis is put on the correct simulation of the energy deposit of electromagnetic cascades from charged-current electron-neutrino interactions. Since existing parameterizations lack the description of suppression effects at high energies, a simulation of the energy deposit of electromagnetic cascades with energies above 1 PeV is developed, including cross sections which account for the LPM suppression of bremsstrahlung and pair creation. An attempt is made to reconstruct the direction of these elongated showers. The analysis presented here makes use of the full charge waveform recorded with the data acquisition system of the IceCube detector. It introduces new methods to discriminate efficiently between the background of atmospheric muons, including muon bundles, and cascade signal events from electron-neutrino interactions. Within one year of operation of the complete detector a sensitivity of 1.5*10^-8 E^-2 GeV/(cm^2 sr s) is reached, which is valid for a diffuse electron-neutrino flux in the energy range from 16 TeV to 13 PeV. Including all neutrino flavors in this analysis, an improvement of at least one order of magnitude is expected, reaching the anticipated performance of a diffuse muon analysis.
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Ablikim, Utuq. "Coulomb explosion imaging of polyatomic molecules after photoionization with X-rays and strong laser fields." Diss., Kansas State University, 2017. http://hdl.handle.net/2097/36252.
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Doctor of PhilosophyDepartment of Physics
Daniel Rolles
Imaging the structures of molecules, understanding the molecular dynamics in onization and dissociation processes and, most importantly, observing chemical reactions, i.e. the making and breaking of chemical bonds in real time, have become some of the most exciting topics in the atomic and molecular physics. The rapid advances of experimental tools such as synchrotron radiation light sources, free-electron lasers and continuing advances of tabletop femtosecond ultrashort lasers that provide laser pulses at a variety of wavelengths have opened new avenues for understanding the structure of matter and the dynamics of the chemical interactions. In addition, significant improvements in computational techniques and molecular dynamic simulations have provided complementary theoretical predictions on structures and chemical dynamics. The Coulomb explosion imaging method, which has been developed and applied in many studies in the last three decades, is a powerful way to study molecular structures. The method has mostly been applied to small diatomic molecules and to simple polyatomic molecules. In this thesis, Coulomb explosion imaging is applied to study the structure of isomers, molecules that have the same chemical formula but different chemical structures. Specifically, by taking inner-shell photoionization as well as strong-field ionization approaches to ionize and fragment the molecules and by using coincidence electron-ion-ion momentum imaging techniques to obtain the three-dimensional momentum of fragment ions, structures of isomers are distinguished by using the correlations among product ion momentum vectors. At first, the study aims to understand if the Coulomb explosion imaging of geometrical isomers can identify and separate cis and trans structures. Secondly, in order to extend the application of the Coulomb explosion imaging method to larger organic molecules to test the feasibility of the method for identifying structural isomers, photoionization studiesof 2,6- and 3,5-difluoroiodobenzene have been conducted. In addition, using the full three-dimensional kinematic information of multi-fold coincidence channels, breakup dynamics of both cis/trans geometric isomers and structural isomers, and in particular, sequential fragmentation dynamics of the difluoroiodobenzene isomers are studied. Furthermore, for each study, Coulomb explosion model simulations are conducted to complement the experimental results. The results of the Coulomb explosion imaging reseach in this thesis paves the way for future time-resolved Coulomb explosion imaging experiments aiming to understand the transient molecular dynamics such as photoinduced ring opening reactions and cis/trans isomerization processes in gas-phase molecules.
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Tao, Li. "Measurement of the cosmic lepton and electron fluxes with the AMS detector on board of the International Space Station. Monitoring of the energy measurement in the calorimeter." Thesis, Université Grenoble Alpes (ComUE), 2015. http://www.theses.fr/2015GRENY016/document.
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Le Spectromètre Magnétique Alpha (AMS) est un détecteur de particules installé à bord de la Station Spatiale Internationale ; il enregistre des données depuis mai 2011. L'expérience a pour objectif d'identifier la nature des rayons cosmiques chargés et des photons et de mesurer leur flux dans la gamme d'énergie du GeV au TeV. Ces mesures permettent d'affiner les modèles de propagation de rayons cosmiques, d'effectuer une recherche indirecte de matière noire, et de chercher l'antimatière primordiale (anti-hélium). Dans ce mémoire, les données des premières années ont été utilisées pour mesurer les flux d'électrons et de leptons (électrons + positons) dans la gamme d'énergie de 0.5 GeV à 700 GeV. L'identification d'électrons nécessite une séparation électrons/protons de l'ordre de 104, obtenue par l'utilisation conjointe des estimateurs de différents sous-détecteurs d'AMS, en particulier du calorimètre électromagnétique (ECAL), du trajectomètre et du détecteur à radiation de transition (TRD). Dans cette analyse, les nombres d'électrons et de leptons sont estimés par un ajustement des distributions de l'estimateur du calorimètre et vérifiés en utilisant l'estimateur du TRD : 11 millions leptons ont été sélectionnés et analysés. Les incertitudes systématiques sont déterminées en variant les coupures de sélection et la procédure d'ajustement. L'acceptance géométrique du détecteur et les efficacités de sélection sont estimées grâce aux données de simulation. Les différences observées sur les échantillons de contrôle issus des données permettent de corriger la simulation. Les incertitudes systématiques associées à ces corrections sont établies en variant les échantillons de contrôle. Au total, à 100 GeV (resp. 700 GeV), l'incertitude statistique du flux de leptons est 2% (30%) et l'incertitude systématique est 3% (40%). Comme les flux se comportent globalement en loi de puissance en fonction de l'énergie, il est important de maitriser la calibration en énergie. Nous avons contrôlé in situ la mesure en énergie du calorimètre en comparant les électrons des données de vol et les données de tests en faisceaux, en utilisant en particulier la variable E/p ou p est la quantité de mouvement mesurée par le trajectomètre. Une deuxième méthode de calibration absolue à basse énergie, indépendante du trajectomètre, basée sur l'effet de la coupure géomagnétique a été développée. Deux modèles de prédiction de la coupure géomagnétique, l'approximation Störmer et le modèle IGRF, ont été testés et comparés. Ces deux méthodes ont permis de contrôler la calibration en énergie à 2% et de vérifier la stabilité des performances du calorimètre dans le tempsThe Alpha Magnetic Spectrometer (AMS) is a particle detector installed on the International Space Station; it starts to record data since May 2011. The experiment aims to identify the nature of charged cosmic rays and photons and measure their fluxes in the energy range of GeV to TeV. These measurements enable us to refine the cosmic ray propagation models, to perform indirect research of dark matter and to search for primordial antimatter (anti-helium). In this context, the data of the first years have been utilized to measure the electron flux and lepton flux (electron + positron) in the energy range of 0.5 GeV to 700 GeV. Identification of electrons requires an electrons / protons separation power of the order of 104, which is acquired by combining the information from different sub-detectors of AMS, in particular the electromagnetic calorimeter (ECAL), the tracker and the transition radiation detector (TRD). In this analysis, the numbers of electrons and leptons are estimated by fitting the distribution of the ECAL estimator and are verified using the TRD estimator: 11 million leptons are selected and analyzed. The systematic uncertainties are determined by changing the selection cuts and the fit procedure. The geometric acceptance of the detector and the selection efficiency are estimated thanks to simulated data. The differences observed on the control samples from data allow to correct the simulation. The systematic uncertainty associated to this correction is estimated by varying the control samples. In total, at 100 GeV (resp. 700 GeV), the statistic uncertainty of the lepton flux is 2% (30%) and the systematic uncertainty is 3% (40%). As the flux generally follows a power law as a function of energy, it is important to control the energy calibration. We have controlled in-situ the measurement of energy in the ECAL by comparing the electrons from flight data and from test beams, using in particular the E/p variable where p is momentum measured by the tracker. A second method of absolute calibration at low energy, independent from the tracker, is developed based on the geomagnetic cutoff effect. Two models of geomagnetic cutoff prediction, the Störmer approximation and the IGRF model, have been tested and compared. These two methods allow to control the energy calibration to a precision of 2% and to verify the stability of the ECAL performance with time
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Engelbrecht, Monique. "The interaction between 6 MV X-rays and p(66)/Be neutrons with spherical gold nanoparticles to induce cellular damage." University of the Western Cape, 2016. http://hdl.handle.net/11394/5550.
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Magister Scientiae (Medical Bioscience) - MSc(MBS)Despite the advances in therapies such as chemotherapy and radiotherapy, tumours have been shown to be resistant to the treatments. Gold nanoparticles (AuNPs) have been recognized as effective radiosensitizers of low energy (e.g. 200–500 kV) X-rays, leading to the emission of Auger electrons that cause highly localised ionizing damage to cells. Spherical AuNPs were synthesised via the reduction of the chloroaurate ions by sodium citrate. Characterisation of AuNPs involved UV-visible spectrophotometry, zeta (Z) potential, dynamic light scattering (DLS) and polydispersity index (PDI) measurements for determination of surface plasmon resonance (SPR), surface charge and stability, as well as transmission electron microscopy (TEM) for hydrodynamic core sizes, size distribution width and shape of AuNPs. Both the 5 and 10 nm AuNPs were found to be anionic with λmax absorbance of 525 nm and uniform size distribution. DLS measurement at 38.12 nm and 48.50 nm, respectively for 5 nm and 10 nm AuNPs, points to aggregation of the AuNPs. However, TEM measurements confirmed the core size of the 10 nm AuNPs. Non-malignant Chinese hamster ovary (CHO-K1), brain endothelial (BEnd5), breast (MCF-10A), isolated human lymphocytes and malignant breast (MCF-7) cell lines were treated with 50 μg/ml of AuNPs, and irradiated with either 1, 2 or 4 Gy X-rays or 1 or 2 Gy p(66)/Be neutron radiation. The γ-H2AX foci assay, cytokinesis-block micronucleus assay, MTT assay and fluorescence-activated cell sorting (FACS) was used to determine that amount of double stranded breaks (DSBs) in isolated lymphocytes, the presence and number of micronuclei (MNi) within binucleated cells (BNCs), cell viability and cell cycle progression, respectively. Preliminary experiments that established the reliability of the study regarding the induction of DNA damage after the bombardment of AuNPs by scattered low kV X-rays, were carried out on lymphocytes. Combined treatment (AuNPs and radiation) resulted in more endogenous foci in comparison to lymphocytes that were treated with AuNPs only. The CHO-K1 and MCF-7 cells showed higher MNi frequencies after the combination treatment of AuNPs and radiation compared to the number of MNi in samples exposed to AuNPs and radiation separately. The AuNPs alone influenced the cellular kinetics of all cell types. Interaction indices, which is the enhancement factor of AuNPs in combination with radiation, for AuNPs and 6 MV 2 Gy X-rays of 1.6 to 1.7 and 1.3 to 1.4 have respectively been determined for CHO-K1 and MCF-7 cells, whilst that for the other cell types used in the study were not different from Unity. As expected, the interaction indices between AuNPs and p(66)/Be neutrons was lower than the interaction indices after 2 Gy X-rays, as p(66)/Be neutrons interact only with the nuclei of the AuNP's atoms and the X-ray photons interact with the orbital electrons of the atoms of the AuNPs leading to Auger electron emission. The cell viability assay showed that 50 μg/ml of AuNPs had an inhibitory effect on cellular proliferation, in all four cell linnes whereas the lower concentrations (2.5, 5 and 10 μg/ml) had no effect. Results in this study, revealed an increase in the accumulation of CHO-K1 an MCF-7 cells in the G₂/M phase of the cell cycle after being treated with AuNPs followed by X-ray radiation, suggesting that the cells have possibly been sensitised to the damaging effects of radiation. Further studies are required to quantify internalised AuNPs and to then link the possible concentration differences of the AuNPs to differences in radiation damage effects observed for the different cell types.
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Alpuche, Aviles Jorge Edmundo. "The Development and Validation of a First Generation X-Ray Scatter Computed Tomography Algorithm for the Reconstruction of Electron Density Breast Images Using Monte Carlo Simulation." Journal of X-ray Science and Technology, IOS Press, 2011. http://hdl.handle.net/1993/4970.
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Breast CT is a promising modality whose inherent scatter could be used to reconstruct electron density (rho_e) images. This has led us to investigate the benefits of reconstructing linear attenuation coefficient (mu) and (rho_e) images of the breast. First generation CT provides a cost-effective and simple approach to reconstruct (rho_e) images in a laboratory but is limited by the anisotropic probability of scatter, attenuation, noise and contaminating scatter (coherent and multiple scatter).
These issues were investigated using Monte Carlo (MC) simulations of a first generation breast scatter enhanced CT (B-SECT) system. A reconstruction algorithm was developed for the B-SECT system and is based on a ring of detectors which eliminates the scatter dependence on the relative position of the scattering centre. The algorithm incorporates an attenuation correction based on the (mu) image and was tested against analytical and MC simulations. MC simulations were also used to quantify the dose per scan.
The ring measures a fraction of the total single incoherent scatter which is proportional to ray integrals of (rho_e) and can be quantified even when electron binding is non negligible. The algorithm typically reconstructs accurate (rho_e) images using a single correction for attenuation but has the capability for multiple iterations if required. MC simulations show that the dose coefficients are similar to those of cone beam breast CT. Coherent and multiple scatter can not be directly related to (rho_e) and lead to capping artifacts and overestimated (rho_e) by a factor greater than 2. This issue can be addressed using empirical corrections based on the radiological path of the incident beam and result in (rho_e) images of breast soft tissue with 1% accuracy, 3% precision and a mean glandular dose of 4 mGy for a 3D scan. The reconstructed (rho_e) image was more accurate than the (rho_e) estimate derived from the (mu) image. An alternative correction based on the thickness of breast traversed by the beam provides an enhanced contrast image reflecting the breast scatter properties. These results demonstrate the feasibility of detecting small (rho_e) changes in the intact breast and shows that further experimental evaluation of this technique is warranted.
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Nndanganeni, Rendani Rejoyce. "Modelling of galactic cosmic ray electrons in the heliosphere / Nndanganeni, R.R." Thesis, North-West University, 2012. http://hdl.handle.net/10394/7034.
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The Voyager 1 spacecraft is now about 25 AU beyond the heliospheric termination shock and
soon it should encounter the outer boundary of the heliosphere, the heliopause. This is set to
be at 120 AU in the modulation model used for this study. This implies that Voyager 1, and
soon afterwards also Voyager 2, should be able to measure the heliopause spectrum, to be
interpreted as the lowest possible local interstellar spectrum, for low energy galactic electrons
(1 MeV to 120 MeV). This could give an answer to a long outstanding question about the
spectral shape (energy dependence) of the galactic electron spectrum at these low energies.
These in situ electron observations from Voyager 1, until the year 2010 when it was already
beyond 112 AU, are used for a comparative study with a comprehensive three dimensional
numerical model for the solar modulation of galactic electrons from the inner to the outer
heliosphere.
A locally developed steady state modulation model which numerically solves the relevant
heliospheric transport equation is used to compute and study modulated electron spectra from
Earth up to the heliopause. The issue of the spectral shape of the local interstellar spectrum at
these low energies is specifically addressed, taking into account modulation in the inner
heliosheath, up to the heliopause, including the effects of the transition of the solar wind
speed from supersonic to subsonic in the heliosheath. Modulated electron spectra from the
inner to the outer heliosphere are computed, together with radial and latitudinal profiles,
focusing on 12 MeV electrons. This is compared to Voyager 1 observations for the energy
range 6–14 MeV. A heliopause electron spectrum is computed and presented as a new
plausible local interstellar spectrum from 30 GeV down to 10 MeV.
The comparisons between model predictions and observations from Voyager 1 and at Earth
(e.g. from the PAMELA mission and from balloon flights) and in the inner heliosphere (e.g.
from the Ulysses mission) are made. This enables one to make conclusions about diffusion
theory applicable to electrons in the heliosphere, in particular the rigidity dependence of
diffusion perpendicular and parallel to the local background solar magnetic field. A general
result is that the rigidity dependence of both parallel and perpendicular diffusion coefficients
needs to be constant below P < 0.4 GV and only be allowed to increase above this rigidity to
assure compatibility between the modeling and observations at Earth and especially in the outer heliosphere. A modification in the radial dependence of the diffusion coefficients in the
inner heliosheath is required to compute realistic modulation in this region. With this study,
estimates of the intensity of low energy galactic electrons at Earth can be made. A new local
interstellar spectrum is computed for these low energies to improve understanding of the
modulation galactic electrons as compared to previous results described in the literature.Thesis (M.Sc. (Physics))--North-West University, Potchefstroom Campus, 2012.
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Way, Austin J. "Fabrication of a-Si and a-InGaN Photovoltaics by Plasma Sputtering." Ohio University Honors Tutorial College / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=ouhonors1398270155.
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Wu, Zhongming. "Diffraction studies of structure and growth of films absorbed on the AG(111) surface /." free to MU campus, to others for purchase, 1997. http://wwwlib.umi.com/cr/mo/fullcit?p9841195.
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Camacho, Garibay Abraham. "Dynamics of Highly Charged Finite Systems Induced by Intense X-ray Pulses." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-212203.
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The recent availability of X-ray Free Electron Lasers (XFELs) has opened a completely new and unexplored regime for the study of light-matter interactions. The extremely bright intensities delivered by XFELs can couple many photons into the target, turning well known interactions such as photoionization and scattering into new, non-linear, complex many-body phenomena. This thesis reports theoretical investigations aiming to improve the understanding of the fundamental processes and dynamics triggered by intense X-ray pulses, with a special focus in finite systems such as molecules and clusters.
Sequential multiple photoionization in atomic clusters was investigated, where previous observations were extended for higher charge states where direct photoionization is frustrated. Through a rate equation study and subsequent molecular dynamics simulations, it was found that frustrated ionization is partially responsible for the low-energy peak observed in the electron energy spectrum. The influence of plasma evaporation over the formation of the sequential low-energy peak was also investigated, identifying the effects of the system size and photon energy.
Multiple channel ionization was also investigated for the case of fullerenes. This is done through a series of studies, starting from a simplified rate equation scheme, and culminating with full molecular dynamics simulations. From these results, a good insight was obtained over the origin, physical meaning, and relevant parameters that give rise to the complicated features observed in the electronic spectra. The mechanisms responsible of all these features are expected to be present in other systems, making these results quite general.
Diffractive imaging of biomolecules was studied in a final step, with a particular focus on the influence of intramolecular charge transfer mechanisms. To this end a conformer of T4 Lysozyme was used, a representative enzyme with well known structure. Charge migration is found to allow for additional processes such as proton ejection, a mechanism which enables an efficient release of energy from the system. This mechanism considerably suppresses structural damage for heavy ions, improving the quality of the measured diffraction patterns.
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Henningsson, Anders. "Ion Insertion into Electrode Materials Studied with X-Ray and Electron Spectroscopic Methods." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis : Univ.-bibl. [distributör], 2002. http://publications.uu.se/theses/91-554-5268-X/.
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Iwan, Bianca. "Creating and Probing Extreme States of Materials : From Gases and Clusters to Biosamples and Solids." Doctoral thesis, Uppsala universitet, Molekylär biofysik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-180997.
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Free-electron lasers provide high intensity pulses with femtosecond duration and are ideal tools in the investigation of ultrafast processes in materials. Illumination of any material with such pulses creates extreme conditions that drive the sample far from equilibrium and rapidly convert it into high temperature plasma. The dynamics of this transition is not fully understood and the main goal of this thesis is to further our knowledge in this area. We exposed a variety of materials to X-ray pulses of intensities from 1013 to above 1017 W/cm2. We found that the temporal evolution of the resulting plasmas depends strongly on the wavelength and pulse intensity, as well as on material related parameters, such as size, density, and composition. In experiments on atomic and molecular clusters, we find that cluster size and sample composition influence the destruction pathway. In small clusters a rapid Coulomb explosion takes place while larger clusters undergo a hydrodynamic expansion. We have characterized this transition in methane clusters and discovered a strong isotope effect that promotes the acceleration of deuterium ions relative to hydrogen. Our results also show that ions escaping from exploding xenon clusters are accelerated to several keV energies. Virus particles represent a transition between hetero-nuclear clusters and complex biological materials. We injected single mimivirus particles into the pulse train of an X-ray laser, and recorded coherent diffraction images simultaneously with the fragmentation patterns of the individual particles. We used these results to test theoretical damage models. Correlation between the diffraction patterns and sample fragmentation shows how damage develops after the intense pulse has left the sample. Moving from sub-micron objects to bulk materials gave rise to new phenomena. Our experiments with high-intensity X-ray pulses on bulk, metallic samples show the development of a transient X-ray transparency. We also describe the saturation of photoabsorption during ablation of vanadium and niobium samples. Photon science with extremely strong X-ray pulses is in its infancy today and will require much more effort to gain more knowledge. The work described in this thesis represents some of the first results in this area.
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Kurata, Ryohei. "Studies on Electronic Properties of Nitrogen-and Boron-Containing π-Electron Systems." Doctoral thesis, 京都大学 (Kyoto University), 2017. http://hdl.handle.net/2433/225623.
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京都大学0048
新制・課程博士
博士(工学)
甲第20398号
工博第4335号
新制||工||1672(附属図書館)
京都大学大学院工学研究科分子工学専攻
(主査)教授 関 修平, 教授 今堀 博, 准教授 伊藤 彰浩, 教授 白川 昌宏
学位規則第4条第1項該当
Doctor of Philosophy (Engineering)
Kyoto University
DGAM
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Carlo, Hugo Lemes. "Influencia do conteudo volumetrico das particulas de cargas nas propriedades mecanicas de diferentes materiais de moldagem." [s.n.], 2008. http://repositorio.unicamp.br/jspui/handle/REPOSIP/288141.
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Orientadores: Mario Alexandre Coelho Sinhoreti, Carlos Jose SoaresTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba
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Resumo: Baseado no entendimento incompleto de como o conteúdo de partículas de carga influencia nas propriedades mecânicas dos materiais de moldagem este estudo avaliou quantitativa e qualitativamente o conteúdo de partículas de carga inorgânicas presente em cinco marcas comerciais de alginatos (Jeltrate; Jeltrate Plus, Jeltrate Chromatic Ortho, Hydrogum e Ezact Krom) e nove marcas comerciais de siliconas de adição e/ou condensação nas consistências massa e/ou fluida (Clonage, Elite HD+ Light Body, Express Light Body, Flexitime, Optosil P Confort/Xantopren VL Plus, Oranwash L, Reprosil A+, Silon 2 APS e Virtual Extra Light Body). Foram realizados testes para determinar recuperação elástica e deformação sob compressão dos alginatos e dos elastômeros e estabelecer, dessa forma, uma correlação entre os resultados para partículas de carga e os testes mecânicos. O conteúdo volumétrico das partículas de carga foi determinado pesando-se as amostras submersas em água antes e após a queima das mesmas durante 3h a 450°C (alginatos) e a 600°C (siliconas). Quantidades determinadas de materiais não polimerizados foram lavadas em acetona e clorofórmio e recobertas com ouro para avaliação da morfologia e tamanho das partículas em M.E.V. A composição foi determinada por EDX. A recuperação elástica e a deformação sob compressão foram determinadas de acordo as especificações ? 1563 (alginatos) e 4823 (elastômeros) da ISO. O alginatos Jeltrate e Jeltrate Plus apresentaram os maiores valores médios para quantidade volumétrica de partículas de carga (%) enquanto o material Hydrogum apresentou os menores valores. A silicone de adição Flexitime Easy Putty apresentou os maiores valores de quantidade volumétrica de partículas, enquanto que a silicone de condensação Xantopren VL Plus apresentou os menores. As partículas de carga dos alginatos apresentaram-se, de forma geral, como objetos esféricos e com perfurações. O material Hydrogum apresentou forma de bastões cilíndricos e perfurados. As siliconas apresentaram morfologias variadas ¿ partículas trituradas, esféricas, esferóides, bastões cilíndricos perfurados e bastões misturados a partículas usinadas. O alginato Ezact Krom apresentou os maiores valores médios de tamanho de partícula, enquanto que o alginato Hydrogum as menores. A silicone de condensação Clonage massa apresentou os maiores valores médios de tamanho de partícula, enquanto a silicone de adição Elite HD os menores. A análise da composição das partículas apresentou o silício como o elemento em maior quantidade. Com relação aos resultados de recuperação elástica, o alginato Ezact Krom e as siliconas Reprosil A+ massa e Flexitime fluida apresentaram os maiores valores de recuperação elástica, enquanto o alginato Jeltrate Plus e as siliconas Optosil P Confort e Clonage fluida apresentaram os menores. Os resultados de deformação sob compressão foram maiores para o alginato Jeltrate Plus e para as siliconas Silon 2 APS massa e fluida. Os menores resultados foram apresentados pelo alginato Ezact Krom e as siliconas Reprosil A+ massa e Xantopren VL Plus. Todos os materiais estão em conformidade com a norma ISO ?1563, mas nem todos estão em relação à norma ?4823
Abstract: Based on the incomplete understanding on how filler features influence the properties of elastomeric impression materials, the purpose of this study was to determine the inorganic filler fraction and size of five commercially available alginates (Jeltrate; Jeltrate Plus, Jeltrate Chromatic Ortho, Hydrogum e Ezact Krom) and nine addition/condensation silicones using the putty/light consistence (Clonage, Elite HD+ Light Body, Express Light Body, Flexitime, Optosil P Confort/Xantopren VL Plus, Oranwash L, Reprosil A+, Silon 2 APS e Virtual Extra Light Body). A SEM/EDX analysis was done to qualitatively characterize the materials. Soon afterwards elastic recovery and strain in compression of the alginates and some the silicones was carried. The inorganic particles volumetric fractions were accessed by weighing a previously determined mass of each material in water before and after burning samples for 3 hours at 450ºC (alginates) and 600ºC (silicones). Unsettled materials were soaked in acetone and chloroform and sputter-coated with gold for SEM evaluation of fillers¿ morphology and size. The filler composition was determined by EDX. Elastic recovery and strain in compression tests were conducted according to ISO specification number 1563 and 4823. Jeltrate and Jeltrate Plus presented the highest mean values of percentage content of inorganic particles in volume, while Jeltrate Chromatic Ortho presented the lowest values. Flexitime Easy Putty was the silicone with the highest mean value, while Xantopren VL Plus had the lowest value. The alginate fillers presented a circular appearance with helical form and various perforations. Hydrogum fillers looked like cylindrical, perforated sticks. SEM pictures of the silicone inorganic particles showed numerous morphologies ¿ lathe-cut, spherical, spherical-like, sticks, and sticks mixed to lathe-cut powder. Ezact Krom was the alginate with the highest values for diameter size, while Hydrogum had the lowest. Clonage Putty showed the highest values, while Elite HD+ Light Body presented the lowest values. The component in higher concentration in the materials is silicon. The alginate Ezact Krom, and the addition cure silicones Reprosil A+ putty and Flexitime Correct Flow had the highest mean values of elastic recovery, while the alginate Jeltrate Plus and the condensation cured silicones Optosil P Confort and Clonage Putty presented the lowest values. Strain in compression test showed the alginate Jeltrate Plus and the condensation cured silicones Silon 2APS Putty and Fluid as the materials with the highest values. The alginate Ezact Krom and the silicones Reprosil A+ Putty and Xantopren VL Plus had lowest values. All materials are in conformity with the requirements of ISO specification number 1563, but not all materials are in conformity with the requirements of ISO specification number 4823
Doutorado
Materiais Dentarios
Doutor em Materiais Dentários
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Chaudhry, M. A. "Electron and X-ray spectroscopy of electron-atom collisions." Thesis, University of Stirling, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.379507.
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Piccinardi, Rita. "X-Ray Free-Electron Lasers." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2016. http://amslaurea.unibo.it/10286/.
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Recenti sviluppi nella progettazione di impianti di luce di sincrotrone di quarta generazione riguardano la produzione di fasci di luce nella banda dei raggi X con elevate caratteristiche in termini di brillanza, coerenza e impulsi estremamente brevi ( femtosecondo ) . I principali schemi per la produzione della radiazione XFEL riguardano l’impiego di ondulatori con differenti modalità di seeding. L’utilizzo dei fasci di radiazione XFEL nelle linee di luce per applicazioni di imaging, spettroscopia e diffrazione, ha determinato un costante sforzo sia nello sviluppo di dispositivi ottici in grado di selezionare e focalizzare il fascio su dimensioni nanometriche, che nella sperimentazione di tecniche “lensless” in grado di superare i limiti imposti dall’utilizzo di tali dispositivi . I risultati ottenuti nella produzione dei fasci hanno consentito nuove possibilità di indagine nella struttura dei materiali su distanze atomiche nella definizione, senza precedenti di dettagli su scale temporali del femtosecondo, permettendo lo studio, non solo di strutture atomiche in condizioni di equilibrio stabile quanto di stati della materia velocemente dinamici e di non equilibrio.
CXDI e Spettroscopia Strutturale Ultraveloce risolte in tempo sono alcune delle tecniche in cui l’utilizzo della radiazione XFEL apre nuove possibilità di indagine agli stati transienti della materia permettendo la ricostruzione della dinamica di processi chimico –fisici su intervalli temporali finora inaccessibili .
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SILVA, NATALIA F. da. "Estabelecimento de um sistema padrão primário para raios X baixas com uma câmara de ionização de ar livre de energias." reponame:Repositório Institucional do IPEN, 2016. http://repositorio.ipen.br:8080/xmlui/handle/123456789/26382.
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Dissertação (Mestrado em Tecnologia Nuclear)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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Ray, Nicolas [Verfasser], and Oleg [Gutachter] Pankratov. "Phonon-induced electron scattering and electric conductivity in twisted bilayer graphene / Nicolas Ray ; Gutachter: Oleg Pankratov." Erlangen : Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 2018. http://d-nb.info/1152078976/34.
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Chauchat, Anne-Sophie. "Étude de la production de rayonnement X par diffusion Compton sur l’installation ELSA." Thesis, Paris 11, 2011. http://www.theses.fr/2011PA112010/document.
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La diffusion Compton est un moyen de produire des rayons X en réalisant des collisions entre un faisceau d'électrons relativistes et un faisceau laser. Par analogie avec le rayonnement synchrotron, le faisceau laser joue le rôle d'onduleur, ce qui entraîne les électrons dans un mouvement d'oscillation. Le rayonnement émis par les électrons en mouvement, dont certaines caractéristiques sont proches de celle du rayonnement synchrotron, peut être produit sur des machines relativement compactes. L'installation ELSA du CEA DAM DIF dispose d'un accélérateur d'électrons (17 MeV) et d'un laser (532 nm) dont les caractéristiques sont favorables à la réalisation d'une expérience de production de rayonnement X par diffusion Compton. La faible probabilité d'interaction et les petites dimensions des faisceaux (< 100 µm, 30 ps (LTMH)) obligent à optimiser avec soin le recouvrement spatial et temporel des impulsions. La visualisation des deux faisceaux en simultanée se fait grâce à un biseau en aluminium renvoyant les images des deux faisceaux vers les caméras CCD et à balayage de fente. La détection du rayonnement X produit (d'énergie < 11 keV) est réalisée par des écrans radio-luminescents à mémoire. Ces écrans, très sensibles au rayonnement de basse énergie, permettent de visualiser le profil du rayonnement et de réaliser la radiométrie du signal. Ces écrans ont également été utilisés en tant que scintillateurs couplés à un photomultiplicateur pour contrôler en temps réel le rendement de l'interaction. L'analyse des résultats expérimentaux obtenus confirme les résultats des simulationsCompton scattering by collisions between relativistic electron beam and laser beam is a way to produce X-rays. Laser beam is seen as an undulator which gives electrons a periodic waved motion. This radiation emitted by electrons motion has some characteristics close to those of synchrotron radiation but can be produced by smaller machines. ELSA facility at CEA DAM DIF is a linear electron accelerator (17 MeV) running with a photoinjector and a laser (532 nm). Characteristics of electrons and laser beam are favourable to a Compton scattering X-rays experiment. Small interaction probability and small beam sizes (< 100 µm, 30 ps (LTMH)) require a careful optimization of spatial and temporal pulses covering. An aluminium bevel-edge allows visualizing beams with CCD and streak cameras. Imaging plates are used as < 11 keV X-rays detectors. These detectors are very sensitive to low signal-to-noise ratio at low energy and give the beam profile. The imaging plates were coupled with a photomultiplier to manage the yield in real time. Experimental results are confirmed by simulations
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Cai, Zhongli. "DNA damage induced by secondary electrons and x-rays." Thèse, Université de Sherbrooke, 2005. http://savoirs.usherbrooke.ca/handle/11143/4204.
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X-rays are widely used in medical diagnosis and radiotherapy. The effects of X-rays on cells are dominated by their actions on the cellular DNA. The interaction of X-rays with DNA produces photoelectrons, Auger electrons, Compton electrons and large quantities of secondary electrons (SE), the majority of which have energies lower than 70 eV. This thesis aims to compare the DNA damage induced by SE and X-rays. A dosimetry method to measure the absorbed dose of Al[subscript k alpha] X-rays (1.5 keV) in ultrahigh vacuum chamber (UHV) using radiochromatic dosimetry films and a color scanner was developed. This provided the value for the absorbed dose in dry biological samples irradiated under UHV, allowing direct comparison of DNA damage induced by Al[subscript k alpha] X-rays and SE. The induction of covalent interduplex DNA crosslinks (CL) by X-rays was detected using restriction enzyme digestion and alkaline agarose gel electrophoresis. The G value for CL induction in DNA in UHV by Al[subscript k alpha] X-rays is 16 « 4 nmol J[superscript -1], 2.8 fold that of double strand breaks (DSB). G(CL) in air by soft X-rays (14.8 keV) is 3 « 1([gamma] [approximate] 6, [gamma] is defined as the number of water molecules per nucleotide,) and 3.2 « 0.4 ([gamma] [approximate] 21) nmol J[superscript -1], 61 and 89% of those for DSB. These results suggest that CL is an important type of DNA damage, possibly as important as DSB in radiobiology. A new method of studying SE-induced DNA damage in comparison to Al[subscript k alpha] X-rays under identical experimental conditions was developed, using thin and thick films of DNA deposited on tantalum. X-ray induced SE emission from the tantalum serves as a source of SE in UHV. The lower limits of G values for DNA SSB and DSB induced by SE were derived to be: 86 « 2 and 8 « 2 nmol J[superscript -1], respectively. These values are 1.5 and 1.6 times larger than those obtained with 1.5 keV photons. The enhanced DNA damage by SE emission from tantalum exposed to soft X-rays (14.8 keV) in air was studied as a function of DNA hydration levels. The enhancement factor for SSB, DSB and CL induced by SE vs X-rays were derived to be: 5.0 « 0.8, 3.6 « 1.0 and 9 « 4 at [gamma] [approximate] 6, and 8 « 1, 9 « 2 and 5.0 « 1.4 at [gamma] [approximate] 21, respectively. This study provides a molecular basis for understanding the enhanced interface biological effects during X-ray diagnostic examination and radiotherapy. A self-assembled monolayer (SAM) of a 5'-32 P-labelled 3'-thiolated oligonucleotide chemisorbed on gold was bombarded by low energy electrons (LEE) of 8 to 68 eV."--Résumé abrégé par UMI.
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Balducci, Lodovico. "Dynamics of hemeproteins by femtosecond X-ray techniques." Thesis, Rennes 1, 2019. http://www.theses.fr/2019REN1S115.
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Récemment, la mise au point de techniques de radiographie à résolution temporelle a ajouté la dimension temporelle à la recherche dans le domaine de la biologie structurale et celles-ci se sont avérées être d'excellents outils pour suivre l'évolution structurale des protéines lors d'une réaction. En particulier, les sources de rayons X de 4ème génération (appelées lasers à électrons libres et à rayons X), avec des impulsions de l'ordre de la femtoseconde et des fluences extrêmement élevées, sont capables de sonder des ensembles de molécules essentiellement gelées dans le temps dans des conditions physiologiques. Après un aperçu des études publiées dans la littérature scientifiques, une introduction de base des techniques utilisées est présentée, accompagnée d'une description du dispositif expérimental et du flux de réduction des données. Les deux derniers chapitres sont consacrés à la présentation des résultats obtenus au cours de deux séries d'expériences réalisées au LCLS (SLAC, Menlo Park, CA, USA), pour étudier les changements structuraux des protéines dans la réaction de photodissociation prototypique du monoxyde de carbone chez des hemoprotéines. Au cours de la première expérience, la modification structurelle globale de trois hemoprotéines a été sondée par une technique de diffusion à résolution temporelle, afin d'observer d'éventuelles différences dans ce que l'on appelle le ''protein quake'' lié à la structure de la protéine. Dans la deuxième expérience, le site actif de la myoglobine a été sondé au cours de la même réaction par absorption de rayons X. Les spectres XANES à résolution temporelle ont été comparés à des calculs théoriques, dans le cadre de la théorie de la diffusion multiple, afin d'obtenir une image détaillée de la dynamique ultrarapide. Un bref projet secondaire portait à mesurer précisément des modèles de diffusion statique de la carboxyhémoglobine, afin de définir ses structures d'équilibre multiple par comparaison avec des combinaisons linéaires de structures cristallographiques connues. En conclusion, dans cette thèse de doctorat, nous avons essayé d'apporter quelques petits éléments dans la compréhension de la dynamique ultrarapide des protéines, en appliquant à la fois des méthodes d'analyse standard (Guinier), mais aussi des méthodes presque inexplorées (calculs de diffusion multiple sur des données à résolution temporelle). Selon le système et le niveau de détail requis, ces méthodes, appliquées ici aux à des systèmes modèles, peuvent être considérées d'excellents outils dans la recherche ultérieure sur des protéines plus complexesRecently, the development of time resolved X-ray techniques has added the time dimension to structural biology studies, and have proven to be great tools to track proteins during the course of a reaction, or a specific conformational change. In particular the 4th generation X-ray sources (so called X-ray Free-Electron Lasers), with femtosecond pulses and extremely high fluences, are capable of probing ensembles of molecules essentially frozen in time under physiological conditions. After an overview of the past studies in the field, a basic introduction of the used techniques, the description of the experimental set-up and the flow of data reduction are presented. The last two chapters are devoted to present the results obtained during two separate sets of experiments, conducted at the XPP beamline of the Linac Coherent Light Source (SLAC, Menlo Park, CA, USA), to study the protein's structural changes, upon prototypical photo-dissociation reaction of carbon monoxide from heme proteins. During the first experiment, the global structural modification of three heme proteins has been probed by means of time resolved scattering technique, in order to observe eventual differences in the so called “protein-quake” depending on the protein's structure. In the second experiment, the active site of myoglobin was probed, during the same reaction, by X-ray absorption. The time resolved XANES spectra have been compared with theoretical calculations, in the framework of the multiple scattering theory, in order to retrieve a detailed picture of the ultra-fast dynamics. A further small side-project dealt with the precise measurement of static scattering patterns of carboxy hemoglobin with the goal of defining its multiple equilibrium structures by comparison with linear combinations of known crystallographic structures. In conclusion, in this Ph.D. thesis we tried to add some small pieces in the understanding of ultra-fast proteins dynamics by applying both standard (Guinier) and almost unexplored (multiple scattering calculations on time resolved data) analysis methods: depending on the system and the level of details required, these methodologies, here applied on model systems, can be considered excellent tools for further research on more complicated proteins
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Dupuy, Rémi. "Photon and electron induced desorption from molecular ices Spectrally-resolved UV photodesorption of CH4 in pure and layered ices The efficient photodesorption of nitric oxide (NO) ices : a laboratory astrophysics study X-ray photodesorption from water ice in protoplanetary disks and X-ray-dominated regions." Thesis, Sorbonne université, 2019. http://www.theses.fr/2019SORUS068.
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L’excitation électronique de molécules condensées sur des surfaces froides (10-100 K) peut mener à la désorption de certaines de ces molécules. Ce processus fondamental a des conséquences dans de nombreuses disciplines, dont deux ont guidé ce travail : l’astrochimie et la dynamique du vide dans les accélérateurs. La désorption induite par photons et électrons est étudiée pour des films amorphes de molécules condensées (glaces) telles que CO, H2O, NO ou CH4. Un objectif de cette thèse est la quantification de la désorption des différentes espèces, et d’explorer les paramètres pouvant affecter l’efficacité du processus. Le second objectif est de déterminer l’évolution et la relaxation des excitations électroniques initiales et par quel mécanisme cela mène à la désorption. La photodésorption est étudiée au LERMA en utilisant le rayonnement synchrotron dans la gamme du VUV (5-14 eV) et des X mous (520-600 eV). Cela permet d’obtenir une information spectrale cruciale pour la compréhension des mécanismes et pour l’implémentation dans les modèles. La désorption induite par les électrons est étudiée au CERN dans la gamme d’énergie 150-2000 eV. Les résultats obtenus étendent les données de photodésorption UV disponibles et permettent de déterminer la pertinence de la désorption par les électrons ou les rayons X pour l’astrochimie. Des progrès sont faits dans la compréhension des mécanismes, notamment sur le rôle du transport d’énergie ou de particules depuis l’intérieur de la glace vers la surface, ou sur la désorption indirecte. Un nouveau dispositif expérimental a aussi été mis en place au LERMA pour des expériences de désorption par laser et de spectroscopie laser, permettant d’obtenir l’énergie interne et cinétique des molécules désorbéesThe deposition of energy in the form of electronic excitations in molecules condensed on cold surfaces (10-100 K) can lead to the desorption of some of these molecules. This basic surface science process has consequences in a variety of fields, two of which are of concern here : astrochemistry and vacuum dynamics. Photon and Electron-Induced desorption are studied in this manuscript for thin films of condensed molecules (ices), e.g. CO, H2O, NO or CH4. The first objective is to obtain a quantification of the desorption of the various desorbing species, and to look for the parameters that affect the efficiency of the process. The second objective is to understand the mechanisms of evolution and relaxation of the initial electronic excitations that lead to desorption. Photon-induced desorption is studied at LERMA using synchrotron radiation in the VUV range (5-14 eV) and soft X-ray range (520-600 eV). This allows to obtain spectrally-resolved information, which is crucial both for model implementation and fundamental understanding of the mechanisms. Electron-induced desorption is studied at CERN in the 150-2000 eV range. The results expand the available data on UV photodesorption and allow to determine the relevance of electron or X-ray desorption for astrochemistry. Progress has also been made on the understanding of mechanisms, particularly on the role of energy or particle transport from the bulk to the surface of the ice, on indirect desorption, or on the desorption of ions in the soft X-ray range. A new experimental set-up has also been developed at LERMA for laser desorption and laser spectroscopy experiments, allowing quantum-state and kinetic energy resolved measurements of desorbed molecules
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Williams, Andrew James. "A water calorimeter for high energy x-rays and electrons." Thesis, University College London (University of London), 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.394541.
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Chervy, Pierre. "Caractérisation biophysique des interactions entre le Lanréotide et des membranes lipidiques." Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLS306.
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L’objectif de ce travail est de caractériser l’interaction entre le Lanréotide – un octapeptide dicationique – et des membranes composées de lipides. Bien que ce peptide soit très soluble, il possède des propriétés d’autoassemblage. Au-delà d’une concentration critique – qui est sensible à la température et à la force ionique – ce peptide s’auto-assemble en nanotubes dont la structure a été résolue par l’équipe. Ce travail de thèse comporte deux volets : d’une part l’étude de l’interaction entre le Lanréotide et des membranes anioniques, d’autre part l’étude de l’interaction entre le Lanréotide et des membranes neutres.Nous adoptons une approche structurale afin de caractériser les mélanges membrane-peptide : diffusion de rayons X, spectroscopie infrarouge (ATR-FTIR), microscopie électronique (coloration négative et cryofracture) ; ainsi qu’une approche quantitative (ultrafiltration et dosage) afin de déterminer la stœchiométrie des interactions. En présence de lipides anioniques, le Lanréotide interagit en totalité avec les membranes jusqu’à les saturer. Cette interaction, qui n’est pas abolie à forte force ionique (2M de NaCl ou de phosphate), provoque un autoassemblage du peptide à la surface des membranes. Ce phénomène génère des autoassemblages mixtes constitués d’un empilement de bicouches de peptide prises en sandwich entre des bicouches de lipides. Ces empilements s’enroulent selon une spirale d’Archimède, c’est-à-dire une spirale régulière dont le pas est constant. Dans ces assemblages mixtes le peptide est organisé dans un nouveau mode d’assemblage dont la structure est ici résolue.Dans le cas des mélanges membranes neutre-Lanréotide, un coefficient de partage du peptide entre l’eau et les lipides est mis en évidence. Ceci suggère que dans ces conditions le peptide peut traverser les membranes. Enfin l’interaction du Lanréotide avec ces membranes provoque une diminution de sa concentration critique d’assemblageThe aim of this work is to characterize the interaction between the Lanreotide – a dicationic octapeptide – and membranes composed of lipids. Even if the peptide is very soluble, it has self-assembling properties. Above the critical concentration – which is sensitive to both temperature and ionic strength – the peptide self-assembles into nanotubes whose structure has been solved by the team. The present work is divided into two parts: on one side the study of the interaction of the Lanreotide with anionic membranes, on the other one the study of the interaction of the Lanreotide with neutral membranes.We adopted a structural approach to characterize the membrane-peptide mixture: X-ray scattering, vibrational spectroscopy (ATR-FTIR), electron microscopy (negative staining and freeze-fracture) ; we also used a quantitative approach (ultrafiltration and peptide quantification) in order to determine the stoichiometry of the interaction. In the presence of anionic lipids, the peptide interacts with membranes until its saturation. This interaction, which is not abolished at high ionic strength (2M NaCl or phosphate), induces the self-assembly of the peptide at the surface of the membrane. This phenomenon generates mixed self-assemblies composed of a stack of peptide bilayers sandwiched by lipids bilayers. These stacks wrap into an Archimedian spiral which is a regular spiral with a constant step. In these mixed assemblies, the peptide is organized in a new architecture compared to the self-assemble nanotubes. This new structure has been characterized and solved in this study.In the case of neutral membrane-Lanreotide mixture, the peptide partitions between water and lipids. This observation suggests that in this condition the peptide is able to cross the membranes. The peptide-membrane interaction also decreases the critical concentration of the peptide
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Carducci, Michael David. "High-resolution probes of electronic states: Magnetic circular dichroism spectroscopy and electron density distributions by x-ray diffraction." Diss., The University of Arizona, 1994. http://hdl.handle.net/10150/186908.
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Magnetic Circular Dichroism spectroscopy (MCD) has been used to assign the optical spectra in high and low symmetry molybdenyl complexes. High resolution single crystal polarized absorption spectra of (PPh₄) (MoOCl₄) and (AsPh₄) (MoOCl₄(H₂O)) show two ligand field transitions whose polarization, MCD and vibronic fine structure are compatible with previously accepted assignments. In the case of (AsPh₄) (MoOCl₄(H₂O)), the splitting of the ²E by spin-orbit coupling is 810(2) cm⁻¹. The absorption and MCD spectra of LMoOX₂ complexes (where L is hydrotris(3,5-dimethyl-1-pyrazolyl)borate and X = O, Cl or S) can be interpreted within the same framework of ligand field and ligand π to metal transitions adopted for (AsPh₄) (MoOCl₄(H₂O)). For LMoO²⁺ complexes of ⁻SCH₂CH₂S⁻ and toluene-3,4-dithiolate, the features between ∼9000 and 16000 cm⁻¹ are assigned to transitions from sulfur out-of-plane π orbitals to d(xy) and overlapping ligand field bands. The pattern of intense MCD peaks between 17,000 and 35,000 cm⁻¹ is assigned to transitions from out-of-plane sulfur π orbitals to molybdenum d(xz,yz} orbitals. On the basis of these molybdenyl model complexes, an interpretation is proposed for the recently reported MCD spectra of DMSO reductase. The suitability of variable temperature MCD for identifying contributions due to paramagnetic molybdenum(V) in the presence of diamagnetic porphyrin centers was investigated. For a molybdenum(V):free-base porphyrin ratio of 5:1, the Mo(V) MCD could be clearly identified. In a sample of sulfite oxidase which contained about 25% Mo(V), the temperature dependent MCD signal was not significantly above background noise and not assignable as arising from Mo(V). The electron density distributions of two compounds were measured by high resolution, low temperature X-ray diffraction. As a working example of the technique, the deformation density of oxalic acid dihydrate was redetermined and compared to multiple reports. Positional and thermal parameters are in excellent agreement while deformation density and multipole populations differ, but are found to be within the ranges reported. Using the same techniques, the electron density of the macrocyclic thioether 1,4,8,11-tetrathiacyclote adecane (TTCD) was determined at 100 K.
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Hess, Robert. "Electron transport modelling in X-ray tubes." Thesis, University of Surrey, 1997. http://epubs.surrey.ac.uk/970/.
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Ogata, Daniela Yuri. "Efeito do tratamento superficial na devitrificação e dissolução da silica vitrea." [s.n.], 1997. http://repositorio.unicamp.br/jspui/handle/REPOSIP/264852.
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Orientador: Carlos Kenich SuzukiDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica
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Resumo: Neste trabalho procurou-se investigar a influência do tratamento da superficie (tensão/rugosidade provocado pelo processo de desbaste com pó abrasivo) na devitrificação e na dissolução da sílica vítrea. Para tanto, utilizou-se de métodos de caracterização de materiais, tais como difratometria de raios-X, espectroscopia de infravermelho, microscopia óptica e eletrônica e espalhamento de raios-X a baixo ângulo. Para o estudo da influência do tratamento superficial na devitrificação, os resultados de difração de raios-X e microscopia, mostraram que a devitrificação possui forte correlação com o tratamento superficial da sílica vítrea, onde amostras com maior rugosidade, apresentaram também uma maior devitrificação em comparação à outra com menor rugosidade. A dissolução da sílica vítrea por ácido fluorídrico ("etching") também foi estudado, e os resultados mostraram que a taxa de dissolução é dependente da rugosidade superficial, concentração do ácido e tempo de "etching". Resultados adicionais mostraram a formação de cavidades arredondadas na forma de "larvas" (padrão superficial) após "etching". Após um tempo de "etching" entre 33 e 88 horas, as amostras apresentaramum padrão superficial semelhante a "grãos" e no interior dos "grãos", outros "sub-grãos" da ordem de 4-10 'mu¿m, que denotam a existência de microtensões na estrutura amorfa. Neste trabalho, este resultado inédito foi denominado "grão ou sub-grão amorfo", que podem estar relacionados com heterogeneidades em nível atômico da estrutura da sílica vítrea
Abstract: The effect of surface stress and roughness, produced by polishing process with abrasive powder, was investigated on the devitrification and dissolution of silica glass. The characterization studies of the silica glass treated by grinding, polishing and etching and their effect on the devitrification were conducted by X-ray diffraction, optical and electronic microscopy, inftared spectroscopy and small-angle X-ray scattering. The samples were heat treated at 1250°C for a period of 15 min and 150 mino X-ray diffraction and optical microscopy observation showed more intense devitrification effect into a-cristobalite for higher degree of surface roughness, and the samples treated with HF etching presented the lowest devitrification effect. The silica glass surfaces exposed to the furnace atmosphere (air) presented a much bigger crystallization effect, inversely to the bottom surface in contact with a silica base. The dissolution of silica glass by chemical etching (HF solutions) was studied, and the results showed that dissolution rate is dependent on the surface roughness, HF concentration and etching time. For example, the dissolution rate of samples treated with SiC #320 and 'Ce IND. 2¿¿O IND. 3¿, were estimated as 0.16 'mu¿m/min and 0.14 'mu¿m/min, respectively. The results showthat sampleswith longtime etching(~1000 min) revealed grain-like etch pattern of 4 to 10 11min diameter, which suggests reveals the existence of micro-stress in the amorphous structure. This "amorphous grains or sub-grains" might be correlated with atomic into inhomogeneities of amorphous silica structure
Mestrado
Materiais e Processos de Fabricação
Mestre em Engenharia Mecânica
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Nunes, Claudia Carvalho. "Propriedades estruturais do material vitreo silica-titania produzido pelo metodo do aerosol em chama." [s.n.], 2008. http://repositorio.unicamp.br/jspui/handle/REPOSIP/264844.
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Orientador: Carlos Kenichi SuzukiDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica
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Resumo: O sistema binário sílica titânia, SiO2-TiO2,apresenta grande interesse tecnológico devido as suas propriedades: ultra-baixo coeficiente de expansão térmico e alto índice de refração. As propriedades são dependentes da quantidade de dopante presente no material. A SiO2-TiO2 é usada na indústria de componentes fotônicos, tais como, lentes, micro-lentes, espelhos e fibras ópticas especiais. Um importante material óptico para litografia no extremo ultravioleta (EUVL) é caracterizado por concentrações próximas a 8 % em peso de TiO2, com estrutura amorfa e transparente num amplo espectro da região UV, visível e IV. A indústria óptico-eletrônica necessita de fibras ópticas sensoras com alto índice de refração. Este tipo de fibra pode ser obtido através da fabricação de uma fibra de SiO2-TiO2. Amostras com concentrações que variam de 1 a 14 % em peso TiO2 fabricadas pelo método do aerosol em chama foram caracterizadas quanto a suas propriedades estruturais e ópticas. As amostras com concentrações superiores a 7,5 % em peso apresentaram-se translúcidas ou opacas, e com estrutura octaédrica segundo dados de XANES (Absorção de Raios-X próximo à estrutura da borda). A difração de raios-X identificou a fase anatásio da titânia como estrutura octaédrica. Através de tratamentos térmicos a altas temperaturas em chama (> 1500 ºC) obtivemos amostras transparentes no visível, amorfa, contendo 8,2 % em peso. Foi obtido um material com índice de refração de 1,48 para concentração de 10 % em peso de TiO2. Portanto a SiO2-TiO2 é viável para a fabricação de uma fibra com alto índice de refração
Abstract: The binary SiO2-TiO2 system presents a great technological importance due to its special properties: ultra low thermal expansion and high refractive index. The properties depend on the amount of dopant present in material. The SiO2-TiO2 is used for the components of photonic industries, such as lenses, mirrors and special fiber optics. As an important optical material for extreme ultraviolet lithography (EUVL), it is characterized by concentrations of ~ 8 wt. % of TiO2, with amorphous structure and transparent for a large UV, visible and IR spectra. The optoelectronic industries needs optical fiber sensor that presents high refractive index. This kind of fiber can be produce by SiO2-TiO2 fiber production. Samples with concentrations varying in the range 1 to 14 wt. % TiO2 made by flame aerosol technique were characterized in terms of structural and optical properties. As-consolidated samples with concentrations up to 7.5 wt. % TiO2 presented itself translucent or opaque with octahedral structure, according to XANES data (X-ray absorption near-edge structure). The anatase phase of titania was identified by X-ray diffraction patterns. However, by high temperature flame heat treatments (> 1500 ºC), it was possible to obtain transparent SiO2-TiO2 materials in the visible range with concentration up to 8.2 wt. % TiO2. The material presents refractive index 1.48 with concentration about 10 wt. % TiO2. Therefore SiO2-TiO2 is feasible to fibers fabrication with high refractive index
Mestrado
Materiais e Processos de Fabricação
Mestre em Engenharia Mecânica
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Lorentzen, Kirsten. "Duskside relativistic electron precipitation /." Thesis, Connect to this title online; UW restricted, 1999. http://hdl.handle.net/1773/6839.
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Suchánek, Jan. "Elektronový ray tracer." Master's thesis, Vysoké učení technické v Brně. Fakulta informačních technologií, 2019. http://www.nusl.cz/ntk/nusl-403130.
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This thesis is pointed on simulation of electron microscope. It uses knowledge from ray-tracing methods and physically based rendering with physics of electron microscopy. The main object of this thesis is to create realistic simulator for electron microscope which can generate satisfying realistic images. This output can be used for another research in range of machine learning or microscope application development. This method should replace long and more expensive way of getting test images from real system for those research activities.
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Cheung, Loi-ning. "Light and electron microscopic study of the mandibular joint in the rat." Thesis, Click to view the E-thesis via HKUTO, 1992. http://sunzi.lib.hku.hk/HKUTO/record/B38628326.
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SMITH, MARK SCOTT. "THE FORMULATION OF THE STREAMING RAY METHOD FOR ELECTRON TRANSPORT CALCULATIONS IN TWO DIMENSIONS." Diss., The University of Arizona, 1987. http://hdl.handle.net/10150/184222.
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In this work, the method of streaming rays have been expanded to two spatial dimensions (three phase space dimensions, x, y, and s) and was used as a basis for the development of the electron transport computer code SR2D. The streaming ray algorithm is an Eulerian-Lagrangian hybrid. Electrons are followed as they traverse the medium along specified streaming rays. Fluxes, however, are computed at the centers of the fixed cells. The development of the SR2D code required the specification of a Lagrangian streaming ray network overlaying a three dimensional Eulerian grid. In contrast to its one dimensional predecessor, the SR2D code accommodates non-uniform cell sizes and allows for arbitrary quadrature sets (S₂, S₄, S₆, S₈, S₁₂, or S₁₆). The critical aspect of the streaming ray method is the determination of the pathlengths of each and every streaming ray through all of the Eulerian cells. These values must be precalculated and stored because of the iterative nature of the solution scheme. Although the number of pathlengths may be exceedingly large, computer memory requirements are minimized, however, in the two dimensional algorithm by the symmetry of the geometry in each pathlength increment. The SR2D code was used to calculate the energy deposition profile for two kinds of sources, an isotropic point source and a monodirectional point at the periphery of a two dimensional medium. For each case, we chose aluminum with dimensions 0.01g/cm² thick by 0.02g/cm² wide as the medium and specified a grid of 5 by 10 uniform cells, respectively. The pathlength increment was 0.002g/cm² with 25 pathlength increments chosen. An S₈ quadrature set was selected for the monodirectional point source while an S₁₂ quadrature set was used for the isotropic point source. Both sources were normalized to one incident particle with an energy of 200 keV. SR2D results were compared with those from the electron/photon Monte Carlo code TIGER. The total energy deposited in the medium and peak cell was selected to facilitate the comparison. For the monodirectional point source SR2D results were within 1% for total energy deposited into the medium and peak cell energy. The total energy deposited for the isotropic point source was within 1%, but peak cell energy varied by 4%.
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Oreper, Daniel (Daniel G. ). "High resolution in-vivo electrode localization using microfocal X-rays." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/37082.
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Thesis (M. Eng. and S.B.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2006.Statement of responsibility "by Daniel Oreper" taken from abstract, p. 1. Leaf 109 blank.
Includes bibliographical references (leaf 108).
Neuroscientists lack the ability to perform in-vivo electrode localization with high accuracy, especially in deep brain structures. The design, implementation and testing of a microfocal x-ray stereo system that offers an efficient, accurate, and relatively low-cost solution this localization problem is presented. The results indicate the ability to localize a targets to within -50 microns, in a brain-tissue-based frame. This accuracy is approximately twice as good as than the existing gold standard in electrophysiology (microlesions), and, unlike the microlesion method, the stereo microfocal x-ray method has important advantages. In particular, while only tens of neuronal recording sites can be reliably reconstructed with the microlesion method, microfocal x-ray method can be repeatedly performed to accurately estimate an essentially unlimited number of serial penetrations, and the localization results are available in nearly real time without animal sacrifice.
M.Eng.and S.B.
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Lemos, Ana Cláudia Cavalcante Espósito [UNESP]. "Estudo histomorfométrico, ultraestrutural e da expressão de Wnt1, WIF-1 e ASIP na pele com melasma em comparação com a pele sã perilesional e retroauricular." Universidade Estadual Paulista (UNESP), 2017. http://hdl.handle.net/11449/151232.
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Fundo de Apoio à Dermatologia de São Paulo (FUNADERSP)
O melasma é hipermelanose crônica e adquirida decorrente de um complexo processo que envolve hipertrofia melanocítica e disfunção melanogênica. Acomete preferencialmente o sexo feminino e as lesões ocorrem nas áreas fotoexpostas, especialmente a face. Sua patogênese não é bem compreendida e os estudos clássicos avaliam apenas pele acometida e perilesional, mas pouco se sabe do comportamento da pele fotoprotegida, submetida aos mesmos fatores sistêmicos e genéticos. Neste estudo, objetivamos avaliar características histológicas, vias epidérmicas que influem na melanogênese (Wnt e ASIP) e características ultraestruturais da pele com melasma em comparação com a pele sã adjacente e retroauricular. Para a execução deste estudo transversal com controle intra-sujeito, foram coletadas três biópsias cutâneas (punch 3 mm) de onze mulheres com melasma facial. As áreas de coleta foram a pele com melasma, pele sã adjacente (distando no máximo 2 cm do limite da lesão) e pele retroauricular ipsilateral. Os fragmentos provenientes de dez participantes foram corados por hematoxilina-eosina, ácido periódico de Schiff, Fontana-Masson, picrosirius red, azul de toluidina e Verhöff; imunomarcados para CD34 e submetidos à imunofluorescência direta (IFD) de dupla marcação para proteínas Wnt1, WIF-1 e ASIP. Já os três fragmentos de uma das participantes foram processados para Microscopia Eletrônica de Transmissão (MET). Os dados obtidos foram comparados entre as topografias por modelo linear generalizado de efeitos mistos. As participantes eram fototipo III ou IV de Fitzpatrick, com idade média (desvio-padrão) de 42,9 (8,9) anos e apresentavam lesões há 16,7 (7,9) anos. Houve adelgaçamento da camada córnea na pele com melasma e na pele adjacente. Na pele com melasma houve maior compactação da córnea, maior pigmentação melânica epidérmica, maior heterogeneidade do colágeno, elastose solar, maior número de mastócitos, falhas da integridade da zona da membrana basal, melanócitos em pêndulo, bem como maior celularidade e vasos na derme superficial. IFD evidenciou maior intensidade de marcação de Wnt1 na pele com melasma em relação à pele adjacente e maior intensidade na pele retroauricular em relação à pele sã adjacente. Não houve diferença estatística significativa na intensidade de marcação de WIF-1 e ASIP entre as topografias. À MET, houve maior dano estrutural na lâmina lúcida no melasma, bem como maior número de melanossomas maduros e organelas citoplasmáticas nos melanócitos e queratinócitos basais. Tais resultados evidenciam que a pele com melasma apresenta, além da hipertrofia melanocítica, alterações na barreira epidérmica, na derme superior, zona de membrana basal e maior ativação da via Wnt, que diferem da pele fotoexposta adjacente e da retroauricular, configurando um fenótipo individualizado e não somente uma extensão do fotoenvelhecimento ou do envelhecimento intrínseco.
Melasma is a chronic and acquired hypermelanosis resulting from a complex process which involves melanocytic hypertrophy and melanogenic dysfunction. Melasma mainly affects females and lesions occur in the photoexposed areas, especially the face. Its pathogenesis is not well understood, and classical studies evaluate only the affected and perilesional skin, but little is known about the behavior of the non-sun-exposed skin, subjected to the same systemic and genetic factors. In this study, we aimed to evaluate histological features, epidermal pathways that influence melanogenesis (Wnt and ASIP) and ultrastructural characteristics of the skin with melasma in comparison to healthy adjacent and retroauricular skin. For the execution of this cross-sectional study with intrasubject control, three skin biopsies (punch 3 mm) were collected from eleven women with facial melasma. The areas of collection were the skin with melasma, adjacent healthy skin and retroauricular skin. Fragments from ten participants were stained with hematoxylin-eosin, periodic acid from Schiff, Fontana-Masson, picrosirius red, toluidine blue and Verhöff; immunomarked for CD34 and subjected to double-labeled direct immunofluorescence (DIF) for Wnt1, WIF-1 and ASIP proteins. The three fragments of one of the participants were processed for Transmission Electron Microscopy (TEM). The data obtained were compared between topographies by generalized linear model of mixed effects. Participants were Fitzpatrick's phototype III or IV; the mean age (standard deviation) was 42.9 (8.9) years and they had lesions for 16.7 (7.9) years. There was thinning of the corneal layer on the skin with melasma and adjacent skin. In the skin with melasma, there was more corneal compaction, greater epidermal melanic pigmentation, greater collagen heterogeneity, solar elastosis, more mast cells, defects of the basement membrane area, pendulum melanocytes, as well as greater cellularity and vessels in the superficial dermis. DIF showed a greater intensity of Wnt1 marking in the skin with melasma in relation to the adjacent skin, and greater intensity in the retroauricular skin in relation to the adjacent healthy skin. There was no significant statistical difference in the intensity of WIF-1 and ASIP marking between topographies. At TEM, there was more structural damage to the lamina lucida in melasma, as well as more mature melanosomes and cytoplasmic organelles in melanocytes and basal keratinocytes. These results show that melasma skin presents, in addition to melanocytic hypertrophy, alterations in the epidermal barrier, upper dermis, basement membrane zone and greater activation of the Wnt pathway, which differ from adjacent and retroauricular photoexposed skin, forming an individualized phenotype and not only an extension of photoaging or intrinsic aging.
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Батіщев, А. С. "Дослідження взаємодії гармонік дифракційно-черенковського випромінювання у багатозв’язних квазіоптичних системах з періодичними неоднорідностями." Master's thesis, Сумський державний університет, 2021. https://essuir.sumdu.edu.ua/handle/123456789/87400.
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Об’єктом дослідження дипломної роботи є гармоніки дифракційно-черенковсьго випромінювання у багатозв’язних квазіоптичних системах з періодичними неоднорідностями. Теоретичні методи дослідження, котрі використовуються в роботі, засновані на раніше досліджених класичних прикладах дифракційної електроніки в наближенні до заданого струму, та досліджена взаємодія гармоніки дифракційно-черенковського випромінювання у багатозв’язних квазіоптичних системах з періодичними неоднорідностями. Робота викладена на 84 сторінках, в тому числі включає 28 малюнків, 3 таблиці та список літератури з 45 джерел.
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Tarbutt, Michael Roy. "Spectroscopy of few-electron highly charged ions." Thesis, University of Oxford, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.365339.
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Skoglund, Lindberg Peter Anders. "Electron-Impact Liquid-Jet Water-Window X-ray Sources." Licentiate thesis, KTH, Biomedicinsk fysik och röntgenfysik, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-28622.
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This Thesis describes the development and characterization of a soft x-ray liquidjet-anode electron-impact source. With a water-jet target the primary emission is the O Kα line at 525 eV. This is close to the lower edge of the water-window, a spectral region lacking simple laboratory sources. In the hard x-ray regime electronimpact microfocus sources have matured and are simple, stable, reliable, and inexpensive. It would be beneficial if this source concept could be used also for soft x-ray generation. Spectral measurements of a 120 W, 30 keV electron beam focused on a 20 μm water jet show an x-ray intensity of up to 3.2 × 1012 ph/(s×sr×line). Combined with source size measurements up to 50 W a maximum brightness of 3.5 × 109 ph/(s×μm2×sr×line) is reported. This makes the brightness comparable to the compact discharge-plasma sources presently used for soft x-ray microscopy. The source appears to be scalable another order of magnitude which would make the brightness equal to that of the laser-plasma sources.QC 20110119
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Louca, P. "From X-ray structure factors to electron-density distributions." Thesis, University of Bristol, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.374638.
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Hicks, Leon James. "X-ray spectroscopy and electron microscopy of planetary materials." Thesis, University of Leicester, 2015. http://hdl.handle.net/2381/31986.
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The work described in this thesis features the study of planetary materials, including nakhlite martian meteorites, comet 81P/Wild2 grains, and asteroid Itokawa 25143 particles, using various electron microscopy techniques and X-ray spectroscopy. Transmission electron microscopy (TEM), Fe-K X-ray absorption spectroscopy (XAS) and in-situ Transmission X-ray Diffraction (XRD) have been used to determine the structure, ferric content and stoichiometry in the secondary phase mineral assemblages of the nakhlites. By measuring the energy position of the Fe-K XANES 1s→3d pre-edge transition centroid, the Fe3+-rich nature of these minerals has been shown. Analyses of the crystalline phyllosilicates in Lafayette found trioctahedral ferric saponite with a 2:1 T-O-T lattice structure and d001-spacings of 0.96 nm, as well as Fe-serpentine with a 1:1 T-O structure and d001-spacings of 0.7 nm. A ferric poorly crystalline or amorphous gel of similar composition to the phyllosilicates was found as fracture fills throughout the other nakhlites. XRD and Fe-K XAS also allow the mineralogical identification of comet Wild2 terminal grains. The terminal grains of Tracks #170 and #176 are Fe-metal, with hematite subgrain material in #170. The terminal grain of #170 also includes Cr-bearing silicate, similar to the Cr-bearing terminal grain of Track #177. Olivine was found amongst the terminal grains of Track #178 alongside magnetites. The presence of magnetite is consistent with low temperature water-rock interaction similar to a carbonaceous chondrite matrix. XAS has also been used to study Itokawa particles, finding ferrous olivines and pyroxenes, as well as studying other metals and Ni-bearing phases. Comparisons with the Tuxtuac meteorite showed the similarity of Itokawa particles to that of LL5 and LL6 chondrite materials. Measuring Fe-K XAS and XRD has proved to be an effective and non-destructive method for mineralogical characterisation of planetary samples, and determining the oxidation state of Fe-silicates, especially on a micron scale. These will be essential techniques for future sample return missions and meteorite finds.