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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 38 for “"x-ray spectra"”.
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Theory of the x-ray spectra of metals
Submitted by Carolyn Mead (cmead2@illinois.edu) on 2011-06-16T14:11:56Z No. of bitstreams: 1 1982_mehreteab.pdf: 2291713 bytes, checksum: 6a38560b3183d8a25a1e2a1606cfd9aa (MD5)
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Many-Body Effects on the X-Ray Spectra of Metals
… and of disorder on the many-electron X-ray spectra of metals are evaluated in a change-of-mean-field approximation using a one-dimensional nearest-neighbor tight-binding model of a metal.
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Physics of Compton Scattering and X-Ray Spectra of Weakly Magnetic Accreting Neutron Stars
… and apply our results to understanding the X-ray spectra of weakly magnetic accreting neutron stars. We first derive the time-dependent radiative transfer equation that describes spontaneous and induced Compton scattering as well as absorption and emission by static and moving media. We …
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Modeling the high resolution X-ray spectra from the relativistic jets of the X-ray binary SS 433
… model of the relativistic jets in the galactic X-ray binary SS 433 that was proposed by Marshall et al. 2002 (Paper I) using additional observations from the Chandra High Energy Transmission Grating Spectrometer. These observations sample two new orbital/precessional phase combinations. In the …
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Determinations of the radii, redshifts, and atmospheric compositions of neutron stars from modeling their Chandra X-ray spectra
Fitting the X-ray spectra of thermal radiation from neutron stars with realistic atmosphere models provides a way to place constraints on their radii, surface gravities and compositions, and to test general relativity in the strong field limit. Such determinations allow us to constrain the the …
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Coronal properties of pre-main sequence stars in the Orion Trapezium Cluster
… Trapezium Cluster are much more peculiar in X-rays than expected, considering their structure, environment, and age. Highly resolved X-ray spectra provide many more details in order to study these peculiarities, specifically with respect to abundances and accretion signatures. We analyzed the …
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Using novel spectral-timing techniques to probe the rapid variability of X-Ray Binaries
X-ray spectral variability is a powerful probe of the relationship between the accretion disc and corona in accreting compact objects. In this thesis, I present the use of variability techniques to disentangle the different variable components of X-ray spectra. By examining correlated variability …
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QUANTIFICATION OF LOW ENERGY X-RAY DETECTION IN EDS DETECTORS
… an empirical parameter is computed from the x-ray spectra. This parameter represents absorption of lower energy x-rays by the EDS detector and depends on electron beam conditions and the specimen-detector configuration in the scanning electron microscope. The ease of computation of this …
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Spectral Comparisons of Neutron Star Low-Mass X-Ray Binaries with Black Hole X-Ray Binaries
The study of high-resolution X-ray spectra of neutron star low-mass X-ray binaries (LMXBs) allows the investigation of the innermost parts of the accretion disk and immediate surroundings of the compact object. The weak magnetic eld of old neutron stars present in such systems allows the accretion …
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X-ray and optical properties of X-ray luminous active galactic nuclei
… et al. (1962) discovered a diffuse cosmic X-ray background with rocket experiments when they searched for lunar X-ray emission. Later satellite missions found a spectral peak in the cosmic X-ray background at ~30 keV. Imaging X-ray satellites such as ROSAT (1990-1999) were able to resolve up …
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X and UV radiation from accreting non-magnetic degenerate dwarfs
… matter with the stellar surface. The resulting X-ray and UV spectrum gives vital clues about the nature of the underlying star and the extreme conditions of temperature and magnetic field strength that may exist in the emission region. While the X-ray spectra of many sources have been extensively …
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Spectra and variability of accreting black holes
… to this work are the accretion disc and X-ray emitting corona. We use various methods to help determine their location, properties and relation to each other. In chapters 2 and 3, we consider how thermal emission from the accretion disc is affected by the coronal emission. Chapter 2 …
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X-ray absorption by the intergalactic medium
… galaxy clusters and groups via the so-called "X-ray Forest" the X-ray absorption lines produced by the hot IGM. I gave a semi-analytic calculation of the X-ray forest distribution based on the Press-Schechter formalism. The warm-hot intergalactic medium - the IGM between 10⁵ - 10⁷ K - was …
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Modeling and simulations of low dimensional and nanostructured materials systems at the nanoscale
… while the third and the forth focus on X-ray spectra and electron holography simulations for which electronic structure calculations are needed. The present thesis gives a general overview on various computational approaches that are useful in modeling novel low dimensional and …
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Influence of photospheric back-scatter on flare hard x-ray diagnostics.
… of solar photospheric back–scatter on Hard X–Ray (HXR) flare diagnostics. Specifically the thesis presented is concerned with the effect of back–scatter photons upon the morphology of the Hard X–Ray photon spectrum and its effect on the inferred parent electron spectrum. I present a …
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The variability of warm absorbers in Active Galactic Nuclei
… Galactic Nuclei (AGN) using high-resolution X-ray spectra provided by the Chandra High Energy Transmission Grating (HETG). The first study is a single observation of the AGN MR 2251-178, which is known to have a highly variable warm absorber (WA). We find an unusually thin effective hydrogen …
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Understanding X-ray reflection as a probe of accreting black holes
The reflection of the X-rays emitted from a corona of energetic particles surrounding an accreting black hole from the accretion disc is investigated in the context of probing the structure of the central regions as well as the physical processes that power some of the brightest objects seen in the …
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Development of a Single-Crystal X-ray Spectropolarimeter and Application to Wire-Array Z-pinches
… usually inferred from the observation of hard x-ray bursts. Spectroscopy is the way to diagnose plasmas, and because anisotropies such as electron beams can lead to the partial polarization of the emitted radiation, polarization spectroscopy, or spectropolarimetry, can be used to diagnose these …
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Rotation studies in fusion plasmas via imaging X-ray crystal spectroscopy
… effort to meet these needs, a high resolution x-ray crystal spectrometer capable of making spatially resolved measurements has been designed, built, installed and operated on the Alcator C-Mod tokamak. By taking advantage of toroidal symmetry and magnetic flux surface mapping it is possible to …
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