Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 33 for “"Secondary electrons"”.
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Examination of secondary electrons generated by encapsulated gamma sources to improve contact dosimetry estimates
Secondary electron generation on the surface of encapsulated gamma sources can play a large role in the dose measured near the surface of the encapsulation. The National Council on Radiation Protection and Measurements (NCRP) Report - 40 contains contact dose rate conversion factors for …
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Penumbral Distributions For High-energy Radiotherapy Photon Beams: Experimental And Theoretical Determinations
… associated with the lateral spread of the second electrons and is strongly dependent on the beam energy and electron density of the medium of interaction.;Specially-designed cylindrical ionization chambers of varying inside diameters were used to determine the primary penumbral dose distributions …
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Surface Microstructure Evolution of Metallic Specimens Using the Large Chamber Scanning Electron Microscope
… for each individual specimen, and imaged using Secondary Electrons within the gauge length as well as near the grip position. Results will show progression of surface microstructures and nickel content of metallic specimens. Additionally, results will demonstrate the capability of the LC-SEM to …
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Direct ray tracing for low energy electron microscopy
… was also used to plot through-the-lens scattered secondary electrons in such systems, simulating their radial current distribution at a rotationally symmetric detector plane. Lastly, the direct ray tracing method was used to redesign the drift-tube in a dynamic chromatic correction scheme for …
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Structure of cathode-electrolyte interfaces and correlation with ionic conductivity in Solid Oxide Fuel Cell devices
… was carried out with X-ray Diffraction (XRD), Secondary Electrons Microscopy (SEM), X-ray microspectroscopy, X-ray Absorption Near Edge Structure (XANES) and electrochemical Impedance spectroscopy (EIS). XRD was used to evaluate the materials chemical reactivity through Rietveld analysis. SEM …
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Ferromagnetism of novel ultrathin films and multilayers: A study of Ru/C(0001) and Fe/Mn/Fe/Pd(100) using magneto-optic Kerr effect and spin-sensitive electron spectroscopies
… is studied using electron induced spin-polarized secondary electron emission (SPSEE). Below a surface Curie temperature of approximately 250K we find ferromagnetic order of the Ru monolayer. The growth mode of Ru on C(0001) is investigated by Auger electron spectroscopy (AES). We find, that the …
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High current ion emission in electrohydrodynamic spraying
… emitted ions, and the effect on the emission of secondary electrons and residual gas in the vacuum chamber. Some results for spraying from a negative polarity emitter and also for spraying of sodium iodide-glycerol are also reported. The experiments confirm the large effective size of the …
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Electron impact excitation-ionization of molecules
… in biological material like damage to DNA by secondary electrons, and plasma etching processes.</p><p>For the M3DW model, I will present results for electron impact single ionization of small molecules such as Water, Ethane, and Carbon Dioxide and the much larger molecules Tetrahydrofuran, …
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Electron-beam lithography towards the atomic scale and applications to nano-optics
… the role of spot-size, electron scattering, secondary electrons, and volume plasmons in the lithographic PSF by performing EFTEM, momentum-resolved electron energy loss spectroscopy (EELS), sub-10 nm EBL, and Monte Carlo simulations. Finally, we show two applications in nano-optics that …
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Investigation of the tunneling emitter bipolar transistor as spin-injector into silicon
… will be a ferromagnet. Spin-polarized electrons from the ferromagnet tunnel directly into the conduction band of the base of the transistor and are subsequently swept into the collector. The tunneling emitter bipolar transistor as a spin-injector allows for large spin-polarized currents …
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Immersed Finite Element Particle-In-Cell Modeling of Surface Charging in Rarefied Plasmas
… in dusty plasma. The second one concerns a secondary electron emission experiment. The simulation includes detailed experimental setup in a vacuum chamber and the results are compared against experimental data. The simulation is used to determine the facility error in experiments. The third …
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Mesure de sections efficaces absolues vibrationnelles pour la collision d’électrons de basse énergie (1-19 eV) avec le tétrahydrofurane (THF) condensé
… probabilities (cross sections) of low-energy electrons with an important biomolecule. The studied molecule is tetrahydrofuran (THF) which is a good model for the DNA backbone constituent deoxyribose. Knowing the important quantity of secondary electrons generated by the radiations passage …
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Computational Modelling of Radiosensitising Properties of Nanoparticles
… post administration. The transport of low-energy secondary electrons emitted by carbon ion-irradiated AuNP was calculated as a diffusion process and the radical production, due to inelastic collisions of the electrons inside the coating medium, was quantified. By varying the ion energy and coating …
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Low-Energy Electron Impact Fragmentations of the Polycyclic Aromatic Hydrocarbon Anthracene
… potentially in the interstellar medium where secondary electrons may be produced by UV-irradiation of interstellar dust grains. An effusive, molecular beam of anthracene, generated in a resistively heated oven, is crossed with a beam of low-energy electrons to form positively charged …
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Quantification of complex DNA damage by ionising radiation: An experimental and theoretical approach
… The ionisation density of low energy, secondary electrons produced by photons was assessed experimentally from the dependence of the yield of OH radicals escaping intra-track recombination on photon energy. As energy decreases the OH radical yield initially decreases reflecting an …
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Optimization of Gold Nanoparticles for Radiotherapy
… interact with ionising radiation to generate secondary electrons and reactive species that increase cellular damage. One of the most promising elements to use is gold, in the form of gold nanoparticles (AuNPs) because of its biocompatibility and amenability to surface modification. For …
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Electron Attachment To Small Molecular Clusters
A large number of secondary electrons with low energies (< 20 eV) is produced during irradiation of biological matter. It is known that such electrons lead to fragmentation of DNA via dissociative electron attachment (DEA). DEA happens via the formation of a resonance (transient negative ion). …
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Three dimensional modelling and optimisation of multistage collectors
… both the collector and the overall efficiency. Secondary electrons play a detrimental role in collector performance. Use of the asymmetric collector geometries and application of a magnetic field in the collector region have proved to be effective in recapturing the secondaries. A fully …
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Nuclear-Targeted Gold Nanoparticles Enhance The Effects of Radiation Therapy With and Without Liposomal Delivery
… of radiation via generation of short-range secondary electrons in the proximity of the DNA in aggressive cancer clones.</p> <p>To test nAuNPs as a radiosensitizing payload of the TSLs, a three-phase plan is presented. Phase I focuses on AuNP cellular distribution, demonstrating signal …
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Development of an Apparatus for the Study of Electron Impact Fragmentation of Molecular Clusters
… and this beam is crossed with a pulsed beam of electrons. The electron pulse is 1 μs to provide the necessary time-of-flight resolution. Ionised fragments are detected using a reflectron time-of-flight mass spectrometer with a microchannel plate detector. Neutral metastable fragments are …
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