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Dissertations / Theses on the topic 'X-rays'

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Published: 4 June 2021
Last updated: 21 September 2024

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1

Puls, Joachim. "Discussion : X-rays." Universität Potsdam, 2007. http://opus.kobv.de/ubp/volltexte/2008/1800/.

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2

Torney, Martin. "Modelling cometary x-rays." Thesis, University of Strathclyde, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.436835.

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3

Osborne, Michael James. "Higher order parametric x-rays." Thesis, Monterey, California. Naval Postgraduate School, 1991. http://hdl.handle.net/10945/26574.

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4

MOSTACCI, DOMIZIANO VALERIO. "X-RAY EMISSION FROM LASER-HEATED SPHERICAL PLASMAS." Diss., The University of Arizona, 1985. http://hdl.handle.net/10150/188093.

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A model has been developed for calculating x-ray line emission from spherical plasmas. The main features of this method are: (1) Plasma parameters are obtained from a one-dimensional Lagrangian hydrodynamics and heat flow code. (2) Multi-frequency groups: the line structure can be reproduced with the desired accuracy by adjusting the number of frequency groups. (3) Self consistent, time dependent excited level populations and radiation fluxes: the code starts with coronal populations, calculates the ensuing radiation flux and then recalculates the populations and so on, iterating until convergence is reached. (4) Goemetrical groups of rays groups by spherical impact parameters. (5) Line broadening due to ionic thermal agitation and Doppler shift due to the net plasma flow velocity. Inclusion of the flow velocity shift would be different without the multi-frequency group treatment. The method has been applied to an aluminum target, and the results are in good agreement with previous experimental work. The total energy, summed over all lines, as well as the line intensity ratios (which are a sensitive measure of agreement with experiment) were predicted with good accuracy. The pictures that would be seen by a pinhole camera are also calculated by the code.
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5

Wallyn, Justine. "Stealth nanoparticles for preclinical X-rays imaging and multimodal X-rays/MRI (magnetic resonance imaging) imaging." Thesis, Strasbourg, 2017. http://www.theses.fr/2017STRAF074.

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L’imagerie biomédicale est aujourd’hui un outil essentiel pour établir un diagnostic grâce à l’observation des tissus et des fluides biologiques. L’usage d’instruments à imagerie combinée avec des produits de contraste est la clé pour réussir à distinguer précisément un tissu ciblé via l’accumulation de produit de contraste dans le tissu. Les deux principaux appareils à imagerie utilisés sont le scanner à rayons X et l’imagerie à résonance magnétique (IRM). Ils sont fréquemment employés en complément de l’un et l’autre. Typiquement, de petites molécules iodées hydrophiles sont utilisées comme produit de contraste pour la radiographie à rayons X tandis que l’IRM implique des matériaux magnétiques tels que des nanoparticules d’oxyde de fer. Dans le cadre de ce projet doctoral, nous avons donc proposé deux nouveaux produits de contraste dont le premier visait à constituer une alternative aux produits iodés dont la rapide élimination et la toxicité rénale forment deux problèmes récurrents et un second produit, cette fois-ci bimodale, afin de faciliter les procédures d’imagerie bimodale. Pour le premier point, des nanoparticules de polymères iodés pour l’imagerie à rayons X ont été formulées et ce, par une technique de nanoprécipitation. Les paramètres de formulation ont été élucidés de telle sorte que les nanoparticules possédaient une distribution de taille adaptée pour l’administration par voie intraveineuse et une teneur en iode suffisante en iode pour contraster sous rayons X. Une étude in vivo a révélé le potentiel du produit de contraste à visualiser distinctement le foie et la rate et ce, tout en ne présentant pas les principaux problèmes des produits iodés commerciaux. La seconde étude a eu pour but de formuler des nano-véhicules lipidiques capables de générer un contraste pour l’imagerie à rayons X et l’IRM de par l’incorporation d’huile iodée et de nanoparticules d’oxyde de fer dans le coeur de nano-émulsions. Ceci avait pour objectif de fournir une plateforme nanoparticulaire bimodale pour réaliser efficacement et rapidement des procédures d’imagerie multimodale. Nous avons réussi à produire un efficace agent de contraste bimodal permettant d’observer distinctement le foie et les reins par IRM et le foie et la rate par imagerie à rayons X. La pharmacocinétique de la substance administrée a ainsi pu être mise en avant grâce à la bimodalité de l’agent. Employer l’IRM a permis de montrer qu’une fraction de la dose injectée était éliminée par voie rénale tandis que l’imagerie à rayons X a confirmé que les deux tissus, foie et rate,étaient passivement ciblés par l’agent de contraste. Ces deux études ont donc fournies de potentielles solutions pour répondre aux besoins en produits pour l’imagerie à rayons X et en formulations facilitant l’imagerie bimodale des tissus mous
Biomedical imaging is nowadays an essential tool to establish a diagnosis by means of observation of tissues and biological fluids. Combination of imaging instrument with contrast enhancers is a key to obtain clear delineation of a desired tissue by accumulation of a contrast agent into this specific target. The two main imagers are the X-ray scanner and the magnetic resonance imaging (MRI).These imagers are frequently used in conjuncture. Typically, small hydrosoluble iodinated molecules are used as contrasting material for radiography whereas MRI involves magnetic materials like iron oxide nanoparticles. In this work, we proposed two novel contrast agents, the first one was aiming to form an alternative to iodinated contrast agents suffering from fast excretion and causing renal toxicity whereas the second one was aiming at providing bimodal contrasting ability to facilitate access to bimodal imaging procedure in clinics. In the first case, iodinated polymeric nanoparticles, serving for preclinical X-ray imaging were formulated by nanoprecipitation technique. Parameters of formulation were elucidated to provide nanoparticles with size distribution suitable for in vivo administration and high iodine content for contrast enhancement. In vivo study revealed the efficacy of our nanoparticles to clearly visualize liver and spleen and limiting current issues associated with marketed radiopaque contrast agents. The second work achieved was aiming at formulating bimodal lipids-based nanocarriers capable of yielding contrast enhancement for X-ray imaging and MRI by combining iodinated oil and iron oxide nanoparticles within a nano-emulsion core. This would provide bimodal nanoparticulate platform to carry out fast and efficient dual modal imaging procedures. In this context we succeeded to generate efficient dual modal contrast agent yielding clear visualization of liver and kidney by MRI and liver and spleen by X-ray imaging. Pharmacokinetic profile was so determined thanks to bimodal imaging. Using MRI allowed to show that kidneys eliminated a fraction of the dose whereas X-ray imaging confirmed that both tissues, liver and spleen, were passively targeted. These two studies proposed solutions limiting current issues of radiopaque contrast agents and novel formulations to facilitate bimodal imaging for soft tissues imaging
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6

Mishra, Shrawan Kumar. "Polarized X-rays and magnetic interfaces /." kostenfrei, 2010. http://opus.kobv.de/tuberlin/volltexte/2010/2546/.

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7

Franka, Nathan Paul. "Visualizing fluidized beds with X-rays." [Ames, Iowa : Iowa State University], 2008.

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8

De, Filippis Elisabetta. "Clusters of galaxies in x-rays." Thesis, Liverpool John Moores University, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.275933.

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9

Bischi, Matteo. "X rays from laser-plasma accelerators." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2015. http://amslaurea.unibo.it/8163/.

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Uno dei maggiori obiettivi della ricerca nel campo degli acceleratori basati su interazione laser-plasma è la realizzazione di una sorgente compatta di raggi x impulsati al femtosecondo. L’interazione tra brevi impulsi laser e un plasma, a energie relativistiche, ha recentemente portato a una nuova generazione di sorgenti di raggi x con le proprietà desiderate. Queste sorgenti, basate sulla radiazione emessa da elettroni accelerati nel plasma, hanno in comune di essere compatte, produrre radiazione collimata, incoerente e impulsata al femtosecondo. In questa tesi vengono presentati alcuni metodi per ottenere raggi x da elettroni accelerati per interazione tra laser e plasma: la radiazione di betatrone da elettroni intrappolati e accelerati nel cosiddetto “bubble regime”, la radiazione di sincrotrone da elettroni posti in un ondulatore convenzionale con lunghezza dell’ordine dei metri e la radiazione ottenuta dal backscattering di Thomson. Vengono presentate: la fisica alla base di tali metodi, simulazioni numeriche e risultati sperimentali per ogni sorgente di raggi x. Infine, viene discussa una delle più promettenti applicazioni fornite dagli acceleratori basati su interazione tra laser e plasma: il Free-electron laser nello spettro dei raggi x, capace di fornire intensità 108-1010 volte più elevate rispetto alle altre sorgenti.
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10

FERNANDEZ, FELIX EUGENIO. "MULTILAYER REFLECTORS FOR SOFT X-RAYS." Diss., The University of Arizona, 1987. http://hdl.handle.net/10150/184211.

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Current technology has made possible the fabrication of multilayered optical elements for soft x-ray radiation. These structures find a variety of important applications. Difficulties in the design and fabrication of multilayers for soft x-rays are related to the lack of information about the properties of materials in the very thin layers (~5-100 Å) required. Imperfections cause the measured optical properties of the multilayers to deviate strongly from ideal behavior. Realistic calculations of reflectance must take these imperfections into account. We review the pertinent theory, with attention to the problem of including non-ideal properties. We also review characterization techniques suitable for the measurement of relevant structural and stoichiometric parameters of the multilayer. A detailed characterization procedure is presented. This procedure is capable of accurately determining the layer thicknesses, material densities, interfacial rms roughness or diffusion values, crystalline structure, concentration of contaminants, and extent of surface oxidation. The techniques used included low-angle x-ray θ-2θ diffraction with parallel-beam and Bragg-Brentano geometries, wide-film Debye-Scherrer ("Read") camera and Seemann-Bohlin diffractometer, Rutherford backscattering spectroscopy, and transmission electron microscopy. Si/W multilayer mirrors were designed for normal-incidence 210 Å radiation. Samples were fabricated using a magnetically-confined-plasma dc-triode sputtering technique. Our characterization procedure was applied to these samples. To our knowledge, this is the first time such a comprehensive set of characterization techniques has been applied to a multilayer x-ray optical element. The same samples were tested with synchrotron radiation over a wide spectral range, and for several incidence angles. The measured reflectance is in excellent agreement with curves calculated using the information obtained from the characterization results, with no adjustable parameters. The Si/W combination is shown to have good layering characteristics. The near-normal reflectance of the multilayers was 20 to 30 times better than the reflectivity of the best single-surface mirrors at the same wavelengths.
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11

Calle, Pérez Ignacio de la. "Detection of high energy gamma rays from X-ray selected blazars." Thesis, University of Leeds, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.270857.

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12

Beckmann, Volker. "Unification of Active Galactic Nuclei at X-rays and soft gamma-rays." Habilitation à diriger des recherches, Université Paris-Diderot - Paris VII, 2010. http://tel.archives-ouvertes.fr/tel-00601042.

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Through the work on X-ray and gamma-ray data of AGN I contributed significantly to the progress in the unification of AGN since I finished my PhD in 2000.

The study of the evolutionary behaviour of X-ray selected blazars (Beckmann & Wolter 2001; Beckmann et al. 2002, 2003b; Beckmann 2003) shows that their evolution is not as strongly negative as indicated by previous studies. The overall luminosity function is consistent with no evolution in the 0.1−2.4 keV band as seen by ROSAT/PSPC. There is still a difference compared to the luminosity function of FSRQ and LBL, which seem to show a positive evolution, indicating that they have been more luminous and/or numerous at cosmological distances. We indicated a scenario in order to explain this discrepancy, in which the high luminous FSRQ develop into the fainter LBL and finally into the BL Lac objects with high frequency peaks in their spectral energy distribution but overall low bolometric luminosity.

Studying the variability pattern of hard X-ray selected Seyfert galaxies, we actually found differences between type 1 and type 2 objects, in the sense that type 2 seemed to be more variable (Beckmann et al. 2007a). This breaking of the unified model is caused by the different average luminosity of the absorbed and unabsorbed sources, as discussed in Sect. 4.7.3. This can be explained by a larger inner disk radius when the AGN core is most active (the so-called receding disc model).

The work on the sample characteristics of hard X-ray detected AGN also led to the proof that the average intrinsic spectra of type 1 and type 2 objects are the same when reflection processes are taken into account (Beckmann et al. 2009d). This also explains why in the past Seyfert 2 objects were seen to have harder X-ray spectra than Seyfert 1, as the stronger reflection hump in the type 2 objects makes the spectra appear to be flatter, although the underlying continuum is the same.

Further strong evidence for the unification scheme comes from the observation of a fundamental plane which connects type 1 and type 2 objects smoothly (Beckmann et al. 2009d). In addition, in the case of the Seyfert 1.9 galaxy MCG-05-23-016 I showed that the spectral energy distribution of this source and its accretion rate is similar to that of a Galactic binary (Beckmann et al. 2008a).

Throughout the studies I have shown that the intrinsic spectral shape appears to be very stable on weeks to year time scale (Beckmann et al. 2004d, 2005b, 2007b, 2008a). This implies that the overall geometry of the AGN over these time scales did not change dramatically. The variations in intensity can then be explained in two ways: either the amount of material emitting the hard X-rays varies, or the amount of plasma visible to the observer varied, e.g. through different orientation of the disk with respect to the observer. In an upcoming paper we will show though, that NGC 4151 indeed also shows different spectral states, similar to the low-hard versus high-soft spectra in Galactic black hole binaries (Lubinski et al. 2010). A similar result seems to emerge from our INTEGRAL studies on NGC 2110 (Beckmann & Do Cao 2011). For INTEGRAL's AO-8 I have submitted a proposal in order to study spectral states in the Seyfert 2 galaxy NGC 2992, which seems to show a state change over the past 5 years as seen in Swift/BAT longterm monitoring.

The work on the luminosity function of AGN at hardest X-rays (Beckmann et al. 2006d) had a large impact on our understanding of the cosmic X-ray background. As this was the first study of its kind, it showed for the first time that indeed the fraction of highly obscured Compton thick AGN is much lower than expected before the launch of INTEGRAL and Swift. The X-ray luminosity function we revealed is indeed not consistent with the source population seen by INTEGRAL (Beckmann et al. 2006a, 2009d; Sazonov et al. 2007) and Swift (Tueller et al. 2008) being the only contributors to the cosmic hard X-ray background. Thus other sources outside the parameter space observable by these missions have to contribute significantly to the cosmic X-ray background. Our work on the luminosity function triggered several other studies on this issue. The subsequent derived luminosity functions by other groups (Sazonov et al. 2007; Tueller et al. 2008; Paltani et al. 2008) are consistent with our findings.

This also gave rise to an increased interest in the exact shape of the Cosmic X-ray background around its peak at 30 keV, triggering several attempts to a new measurement. Background studies were presented based on a Earth-occultation observation by INTEGRAL (Churazov et al. 2007, 2008; Türler et al. 2010) and by Swift (Ajello et al. 2008).

The understanding of the emission processes in AGN requires knowledge over a wide range of the spectral energy distribution (SED). In studies using CGRO/EGRET and Fermi/LAT data I derived the SED for blazars and non-blazars towards the gamma-ray range (Beckmann 2003; Beckmann et al. 2004b, 2010b). The work on the LAT data not only presented the gamma-ray detection of five gamma-ray blazars (QSO B0836+710, RX J1111.5+3452, H 1426+428, RX J1924.8-2914, and PKS 2149-306) for the first time, but also showed the potential in the combination of INTEGRAL and Fermi data. In the case of Cen A I derived the total energy output of the inverse Compton component based on the combined LAT, ISGRI, and JEM-X data, showing evidence for a spectral break at several hundred keV (Beckmann et al. 2010b).
In addition I successfully showed that gamma-ray blazars can be predicted through the study of their synchrotron branch at energies below 2 keV (Beckmann 2003 and this work).

Contributions of mine to research in fields other than AGN include the study of INTEGRAL detected gamma-ray bursts (e.g. Beckmann et al. 2003a, 2004a, 2008b, 2009a). Here and in collaboration with other colleagues I showed the potential of INTEGRAL data on GRB research. In the field of Galactic X-ray binaries I published one of the first Swift results on a newly discovered highly absorbed HMXB, IGR J16283-4838 (Beckmann et al. 2005a, 2006b). I also contributed significantly to analysis of many other Galactic sources, as shown in Section 4.6.1.

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13

Pfeifer, Thomas. "Adaptive control of coherent soft x-rays." Doctoral thesis, [S.l. : s.n.], 2004. http://deposit.ddb.de/cgi-bin/dokserv?idn=976064227.

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14

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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15

Kulcsár, Gábor. "Intense picosecond x rays from structured targets." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0008/NQ41453.pdf.

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16

Allerton, James John. "A scanning microscope for hard x-rays." Thesis, Royal Holloway, University of London, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.416451.

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17

Prade, H. "Workshop on X-rays from electron beams." Forschungszentrum Rossendorf, 2000. https://hzdr.qucosa.de/id/qucosa%3A21828.

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18

Sinangil, Mehmet Selcuk. "Estimation of crystal size and inhomogeneous strain in polymers using single peak analysis." Thesis, Georgia Institute of Technology, 1996. http://hdl.handle.net/1853/19096.

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19

Chadwick, Mary Paula. "Very high energy cosmic gamma rays from radio and X-ray pulsars." Thesis, Durham University, 1987. http://etheses.dur.ac.uk/6720/.

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This thesis is concerned with the detection of very high energy cosmic gamma-rays from isolated pulsars and X-ray binary sources using the atmospheric Cerenkov technique. A general introduction to gamma ray detection techniques is followed by adscription of the properties of atmospheric Cerenkov radiation and a discussion of the principles of the atmospheric Cerenkov technique. The Mark I and Mark II gamma-ray telescopes operated in Dugway, Utah by the University of Durham between 1981 and 1984 are briefly described. There follows a discussion of the results from observations at many different wavelengths of Cygnus X-3. This object was observed by the Durham group between 1981 and 1983 in Dugway Utah and also in Durham during autumn 1985. The detection in the Dugway data of the 4.8 hr X-ray period and the possible detection of a19.2 day intensity variation are considered. The discovery of a 12.59 ms pulsar in data taken on Cygnus X-3 in 1983 is described. Evidence is presented which suggests this periodicity is also present at a weaker level in earlier data and also in the data taken in Durham in 1985.Results from observations of PSR1937+21 , PSR1953+29and six radio pulsars , are presented. The design and construction of the Mark III telescope, now operating in Narrabri , N.S.W. , is described in detail. Preliminary results from observations with the Mark III telescope of three objects, LMC X-4, the Vela pulsar and CentaurusX-3, are presented, with particular reference to periodicities inherent in the sources. An observation of the supernova in the Large Magellanic Cloud is discussed. A brief discussion of the mechanisms by which V.H.E. gamma-rays may be produced in isolated pulsars and X-ray binary pulsars is given, followed by a description of the future prospects for the Mark III and Mark IV telescopes.
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20

Westphal, Maximillian. "Investigation of low energy, alternative X-ray sources and their interactions with multi-Z materials for theranostics." The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1571133365330023.

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21

Nagpal, Akanksha. "Crystal Structures of Nitroalkane Oxidase: Insights into the Structural Basis for Substrate Specificity and the Catalytic Mechanism." Diss., Available online, Georgia Institute of Technology, 2005, 2005. http://etd.gatech.edu/theses/available/etd-07172005-152826/.

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Thesis (Ph. D.)--Chemistry and Biochemistry, Georgia Institute of Technology, 2006.
Dr. Allen M. Orville, Committee Chair ; Dr. Loren D. Williams, Committee Member ; Dr. Donald F. Doyle, Committee Member ; Dr. Dale E. Edmondson, Committee Member ; Dr. Giovanni Gadda, Committee Member.
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22

Medin, Zach, Marina von Steinkirch, Alan C. Calder, Christopher J. Fontes, Chris L. Fryer, and Aimee L. Hungerford. "MODEL ATMOSPHERES FOR X-RAY BURSTING NEUTRON STARS." IOP PUBLISHING LTD, 2016. http://hdl.handle.net/10150/624031.

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The hydrogen and helium accreted by X-ray bursting neutron stars is periodically consumed in runaway thermonuclear reactions that cause the entire surface to glow brightly in X-rays for a few seconds. With models of the emission, the mass and radius of the neutron star can be inferred from the observations. By simultaneously probing neutron star masses and radii, X-ray bursts (XRBs) are one of the strongest diagnostics of the nature of matter at extremely high densities. Accurate determinations of these parameters are difficult, however, due to the highly non-ideal nature of the atmospheres where XRBs occur. Observations from X-ray telescopes such as RXTE and NuStar can potentially place strong constraints on nuclear matter once uncertainties in atmosphere models have been reduced. Here we discuss current progress on modeling atmospheres of X-ray bursting neutron stars and some of the challenges still to be overcome.
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23

Cederström, Björn. "A multi-prism lens for hard X-Rays." Doctoral thesis, KTH, Fysik, 2002. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3423.

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This thesis describes a new type of refractive lens for hardx-rays. It is shown that a linear array of prisms, slightlyinclined with respect to the optical axis, will form a linefocus at a certain distance from the lens. Hence, the namemulti-prism lens. These lenses are free from sphericalaberration and are similar to planar parabolic compoundrefractive lenses in terms of performance. However, theydistinguish themselves in that only planar surfaces need to befabricated. A special feature is that the focal length can beeasily varied by adjusting the inclination angle. Theoretical calculations, based on geometrical and physicaloptics, are used to characterize the lenses. Aberrations arediscussed, as well as the sensitivity to fabricationimperfections, and insufficient flatness is identified as apotential problem. Ray-tracing is used to test theapproximations and assumptions used in the theory. Applicationsin x-ray microscopy and mammography are discussed. Lenses have been made of beryllium, silicon, epoxy anddiamond using different methods. Results from measurements ofsurface roughness and figure error show that the imperfectionsof the silicon and epoxy lenses should have a small impact,while the beryllium lenses should suffer from strongscattering. Experiments were performed at the EuropeanSynchrotron Radiation Facility and sub-µm focal linewidths, close to theoretical expectations, were measured forsilicon and epoxy lenses at 30 keV and 14 keV, respectively.Insertion gains up to 40 were reached. Two crossed lenses wereused to obtain focusing in two dimensions and a point focus.The smallest measured focal spot size was 1.0 µm by 5 .4µm, and an insertion gain exceeding 100 was achieved usingepoxy lenses. The diamond lenses suffered from voids in the materialformed in the chemical vapor deposition process, butnevertheless provided focal lines less than 2 µm in width,albeit at at relatively low insertion gain of 13. Due to theirexcellent thermal properties, these lenses are put forward ascandidates for optics at the next generationultra-high-intensity synchrotron beams and x-ray free electronlasers. Keywords:x-ray, optics, refractive, lens, mammography,synchrotron.
QC 20100524
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24

Gunnarsson, Annicka, Eva Lindros, and Jeff Winter. "Viewing patients' x-rays in the radiologist's home." Thesis, Blekinge Tekniska Högskola, Institutionen för programvaruteknik och datavetenskap, 2002. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-2264.

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Our assignment was to present a report to the radiology clinic at the County Hospital in Blekinge, evaluating the risks inherent in transferring patient information via Internet between the radiologist?s home and the hospital and presenting suggestions to the clinic for mechanisms by which the privacy and personal health of the patient can be ensured. Our aim was to investigate how to maintain an acceptable level of security to ensure that the patient?s privacy and security are not threatened. We wanted to present a list of measures that the clinic should take to ensure that security is maintained. We have used several different methods during our investigation: literature studies; a case study at Blekinge County Council?s x-ray clinic that includes interviews with the head of the clinic, the System Manager and System Administrators and e-mail interviews with other relevant personnel. Using these methods, we have concluded that the present working method does not fulfil the requirements stated in the theories concerning medical security. To ensure a level of computer security in accordance with the recommendations made in this thesis, it is necessary to take certain measures, which we have listed here. These include the introduction of single session login, the formulation of explicit security policies, a program for user education, the encryption of transmissions, and the use of the audit trail to track system use. All of these measures concern the intended new working method with the introduction of an outside connection; some of them concern the existing system and working method. A system fulfilling these measures will however always encompass risks, even in the safest distributed system. With today?s technologies is there always a risk that could threaten the patient?s privacy or security. This does not mean that a sufficient security level cannot be reached. By following the recommendations presented in this thesis, the x-ray clinic can maintain an acceptable level of security, when the radiologists on back-up duty are viewing x-rays and making diagnoses from home.
Vår uppgift var att presentera en rapport till röntgenavdelningen på Blekingesjukhuset, som undersöker vilka risker som uppstår när patientinformation skickas mellan röntgenpersonalens hem och sjukhuset via Internet. Vi ville presentera ett förslag till kliniken innehållande mekanismer för att skydda patientens personliga integritet och fysiska säkerhet. Vårt mål var att undersöka hur en acceptabel säkerhetsnivå kan upprätthållas, för att säkerställa patientens integritet och säkerhet. För att göra detta ville vi presentera en åtgärdslista som kliniken måste vidta för att upprätthålla säkerheten. Vi har använt oss av flera metoder i vår undersökning: litteraturstudier; en Case Study på Blekinge Sjukhusets röntgenklinik, med tillhörande intervjuer med klinikchefen, systemägare och systemadministratörerna samt e-postintervjuer med andra nyckelpersoner. Genom att använda dessa metoder har vi kommit fram till att det nuvarande arbetssättet inte uppfyller kraven som ställs enligt teorier gällande medicinsk säkerhet. För att säkerställa en nivå i enlighet med rekommendationerna som vi presenterar i denna uppsats är det nödvändigt att vidta vissa åtgärder som vi har listat här. Denna inkluderar införande av engångslösenord, formulering av en explicit säkerhetspolicy, ett program för användarutbildning, kryptering av kommunikationer samt användandet av loggade filer för att spåra systemanvändandet. Alla dessa åtgärder gäller det föreslagna nya arbetssättet, som introducerar en koppling utåt från landstingets intranät till röntgenpersonalens hem via Internet; vissa av de gäller det befintliga systemet och arbetssättet. Även om alla krav är uppfyllda så kommer ändå, med dagens teknologi, vissa risker att kvarstå. Detta innebär emellertid inte att tillfredsställande säkerhet inte kan uppnås. Genom att följa rekommendationerna som vi har presenterat i detta arbete kan röntgenkliniken ändå uppnå tillräcklig säkerhet när röntgenpersonalen med jour i hemmet undersöker röntgenbilder och ställer diagnoser hemifrån.
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25

Ghiringhelli, Giacomo. "Resonant spectroscopies with circularly polarised soft X-rays /." Berlin : dissertation.de, 2002. http://www.gbv.de/dms/goettingen/34137007X.pdf.

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26

VIEIRA, MARCO ROGERIO. "DEVELOPING A VERSATILE MONOCHROMATIZATION SYSTEM FOR X-RAYS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2009. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=15703@1.

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CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO
FUNDAÇÃO DE APOIO À PESQUISA DO ESTADO DO RIO DE JANEIRO
A investigação da dinâmica da interação de raios-X de alta energia e moléculas de interesse biológico impõe que a energia dos raios-X seja bem definida, de modo que se possa estabelecer a dependência entre os padrões de ionização e fragmentação molecular com a energia do feixe incidente. Com este objetivo, um sistema versátil foi projetado, construído e caracterizado para ser utilizado como monocromador do feixe de amplo espectro produzido por um tubo de raios-X modelo ISOVOLT 160 M2. O sistema de monocromatização consiste de um par de cristais montados sobre duas mesas transladoras fixadas a um goniômetro de alta precisão, fabricados pela Newport Corporation. Esta configuração permite movimentos de translação independentes para os dois cristais, associados a um movimento de rotação do sistema como um todo com respeito à direção de incidência do feixe de raios-X. Estes movimentos, juntamente com uma escolha conveniente do par de cristais para uma dada faixa de energia - o que depende do material e da orientação dos cristais -, permitirão a cobertura de uma região muito extensa de energias de raios-X, de alguns até cerca de 100 kV. Quando este sistema se encontrar totalmente operacional, será possível realizar uma grande variedade de experiências nos campos da Física de Colisões e das Radiações, tais como, fragmentação molecular induzida por raios- X, fluorescência e difração seletivas em cristais, avaliação em tempo real de danos induzidos por raios-X em tecidos biológicos, testes não destrutivos em materiais, dentre muitas outras aplicações.
The investigation of the dynamics of the interaction of high-energy X-rays and molecules of biological interest requires the energy of the X-rays to be well defined, so that one can establish the dependence of the molecular ionization and fragmentation patterns as functions of the incident beam energy. For this purpose, a versatile system for the monochromatization of the broadband beams produced by an ISOVOLT 160M2 X-ray tube has been designed, constructed and characterized. The monochromator consists of a pair of crystals mounted on two translator tables fixed on a high-precision goniometer, all manufactured by Newport Corp. This configuration allows independent translational motions for the two crystals, associated to a rotational motion of the whole system in respect to the direction of the incident X-ray beam. These motions, together with a convenient choice of the pair of crystals for a given energy range - which depends on the material and orientation of the crystals -, will allow us to cover a wide range of X-rays energies, roughly from few to around 100 keV. However, it has not yet been possible to distinguish energy-defined X-ray peaks with the complete two-crystal system. Some of the possible causes may be related to the large angular dispersion of the incident beam and to the need of more accurate adjustments of the parallelism between both crystals. When this system is fully operational, it will be possible to perform a large variety of experiments in the fields of collision and radiation physics, such as, molecular fragmentation by Xrays, selective fluorescence and diffraction in crystals, real-time evaluation of Xray- induced damage in biological tissues, non-destructive testing of materials, among many other aplications.
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27

Haiderbhai, Mustafa. "Generating Synthetic X-rays Using Generative Adversarial Networks." Thesis, Université d'Ottawa / University of Ottawa, 2020. http://hdl.handle.net/10393/41092.

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We propose a novel method for generating synthetic X-rays from atypical inputs. This method creates approximate X-rays for use in non-diagnostic visualization problems where only generic cameras and sensors are available. Traditional methods are restricted to 3-D inputs such as meshes or Computed Tomography (CT) scans. We create custom synthetic X-ray datasets using a custom generator capable of creating RGB images, point cloud images, and 2-D pose images. We create a dataset using natural hand poses and train general-purpose Conditional Generative Adversarial Networks (CGANs) as well as our own novel network pix2xray. Our results show the successful plausibility of generating X-rays from point cloud and RGB images. We also demonstrate the superiority of our pix2xray approach, especially in the troublesome cases of occlusion due to overlapping or rotated anatomy. Overall, our work establishes a baseline that synthetic X-rays can be simulated using inputs such as RGB images and point cloud.
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28

Schlotter, William F. "Lensless fourier transform holography with soft x-rays /." May be available electronically:, 2007. http://proquest.umi.com/login?COPT=REJTPTU1MTUmSU5UPTAmVkVSPTI=&clientId=12498.

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29

Grätz, Matthias. "Characterisation and application of a laser-based hard X-ray source." Lund : Lund Institute of Technology, 1998. http://catalog.hathitrust.org/api/volumes/oclc/68945036.html.

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30

Dowthwaite, J. C. "Very energetic gamma rays from binary X-ray sources and other astronomical objects." Thesis, Durham University, 1987. http://etheses.dur.ac.uk/7064/.

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This thesis describes the observation of a number of astronomical objects using the University of Durham Atmospheric Cerenkov light detectors. The array of telescopes was used to study the Very High Energy (V.H.E.) gamma-radiation from these objects from June 1981 until November 1984.The general features of Gamma-ray astronomy are briefly discussed, and a review of the main results of previous gamma-ray observations is given. The basic theory and general characteristics of Atmospheric Cerenkov Effect experiments are reviewed. Details of the design, operation and performance of the University of Durham facility are presented in addition to details of the improvements achieved in the development of a new telescope. In particular, the new optical system is described. The main analysis procedures are explained. The adaptation of statistical techniques used to analyse the intensity of the Cerenkov light flash is described in some detail. A discussion of the problems involved in conducting an extensive search for periodicity in the data collected from Cygnus X-3 is given. A procedure for testing for transient pulsed gamma-ray emission from the Crab Pulsar is also described. The results of the observations from several objects are presented., the binary X-ray sources, Cygnus X-3, Hercules X-l and 4U0115+63, the Crab pulsar and the Galactic Plane. In addition, the preliminary results from observations of seven radio pulsars and seven other objects are given. A review of the main production mechanisms of V.H.E. gamma-radiation is given with particular emphasis on the models proposed for the high energy processes in Cygnus X-3, other binary-ray sources and pulsars.
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Ueno, Masaru. "Supernova remnants selected with X-rays : contribution to the galactic cosmic-ray acceleration." 京都大学 (Kyoto University), 2005. http://hdl.handle.net/2433/145075.

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Kyoto University (京都大学)
0048
新制・課程博士
博士(理学)
甲第11307号
理博第2865号
新制||理||1428(附属図書館)
22950
UT51-2005-D58
京都大学大学院理学研究科物理学･宇宙物理学専攻
(主査)教授 小山 勝二, 教授 今井 憲一, 教授 中村 卓史
学位規則第4条第1項該当
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32

Bufanda, E., D. Hollowood, T. E. Jeltema, E. S. Rykoff, E. Rozo, P. Martini, T. M. C. Abbott, et al. "The evolution of active galactic nuclei in clusters of galaxies from the Dark Energy Survey." OXFORD UNIV PRESS, 2017. http://hdl.handle.net/10150/623206.

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The correlation between active galactic nuclei (AGNs) and environment provides important clues to AGN fuelling and the relationship of black hole growth to galaxy evolution. In this paper, we analyse the fraction of galaxies in clusters hosting AGN as a function of redshift and cluster richness for X-ray-detected AGN associated with clusters of galaxies in Dark Energy Survey (DES) Science Verification data. The present sample includes 33 AGNs with LX > 1043 erg s(-1) in non-central, host galaxies with luminosity greater than 0.5L(*) from a total sample of 432 clusters in the redshift range of 0.1< z <0.95. Analysis of the present sample reveals that the AGN fraction in red-sequence cluster members has a strong positive correlation with redshift such that the AGN fraction increases by a factor of similar to 8 from low to high redshift, and the fraction of cluster galaxies hosting AGN at high redshifts is greater than the low-redshift fraction at 3.6 sigma. In particular, the AGN fraction increases steeply at the highest redshifts in our sample at z > 0.7. This result is in good agreement with previous work and parallels the increase in star formation in cluster galaxies over the same redshift range. However, the AGN fraction in clusters is observed to have no significant correlation with cluster mass. Future analyses with DES Year 1 through Year 3 data will be able to clarify whether AGN activity is correlated to cluster mass and will tightly constrain the relationship between cluster AGN populations and redshift.
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高樹豐 and Shu-fung Ko. "Emission morphologies and phase-resolved spectrum of gamma ray pulsar." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2001. http://hub.hku.hk/bib/B31224489.

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Ko, Shu-fung. "Emission morphologies and phase-resolved spectrum of gamma ray pulsar /." Hong Kong : University of Hong Kong, 2001. http://sunzi.lib.hku.hk:8888/cgi-bin/hkuto%5Ftoc%5Fpdf?B23476370.

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35

Feng, Zhenxing 1982. "Experimental and theoretical investigation of the coherent x-ray propagation and diffraction." Thesis, McGill University, 2006. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=101122.

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Coherent X-ray diffraction and X-ray Intensity Fluctuation Spectroscopy (XIFS) are ideal methods and techniques to perform measurements on the dynamics of fluctuations in condensed matter materials. To investigate more systems and faster fluctuations by being able to tune the coherence length, we use a zone plate to change the coherence length and beam size but keep most of the intensity. Using the zone plate, experiments were carried out to measure the properties of the focused beam. We applied a formalism to calculate the effect of optics on coherence. We tested our results by doing measurement at Advanced Photon Source. We measured the focal properties of the zone plate, speckle sizes and contrast, obtained by using coherent X-ray diffraction from an disordered Fe3Al crystals. Our theoretical calculations are compared with the experimental results.
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Chase, Michael B. "Boro-silicate polycapillary lens for collimation of x-rays." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1997. http://handle.dtic.mil/100.2/ADA334008.

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Thesis (M.S. in Applied Physics) Naval Postgraduate School, June 1997.
Thesis advisor(s): Xavier K. Maruyama, R.M. Harkins. "June 1997." Includes bibliographical references (p. 77-78). Also available online.
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Costantini, Elisa. "Scattering and Absorption of X-rays by Interstellar Dust." Diss., lmu, 2004. http://nbn-resolving.de/urn:nbn:de:bvb:19-22821.

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38

Omanovic, Maja. "Matching of Dental X-rays for Human Forensic Identification." Thesis, University of Waterloo, 2006. http://hdl.handle.net/10012/2939.

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Dental records have been widely used as tools in forensic identification. With the vast volume of cases that need to be investigated by forensic odontologists, a move towards a computer-aided dental identification system is necessary. We propose a computer-aided framework for efficient matching of dental x-rays for human identification purposes. Given a dental x-ray with a marked region of interest (ROI), we search the database of x-rays (presumed to be taken from known individuals) to retrieve a closest match. In this work we use a slightly extended Weighted Sum of Squared Differences (SSD) cost function to express the degree of similarity/overlap between two dental radiographs. Unlike other iterative Least Squares methods that use local information for gradient-based optimization, our method finds the globally optimal translation. In 90% of the identification trials, our method ranked the correct match in the top 10% using a database of 571 images. Experiments indicate that matching dental records using the extended SSD cost function is a viable method for human dental identification.
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39

Perkins, Simon. "Identification and Reconstruction of Bullets from Multiple X-Rays." Thesis, University of Cape Town, 2004. http://pubs.cs.uct.ac.za/archive/00000136/.

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The 3D shape and position of objects inside the human body are commonly detected using Computed Tomography (CT) scanning. CT is an expensive diagnostic option in economically disadvantaged areas and the radiation dose experienced by the patient is significant. In this dissertation, we present a technique for reconstructing the 3D shape and position of bullets from multiple X-rays. This technique makes us of ubiquitous X-ray equipment and a small number of X-rays to reduce the radiation dose. Our work relies on Image Segmentation and Volume Reconstruction techniques. We present a method for segmenting bullets out of X-rays, based on their signature in intensity profiles. This signature takes the form of a distinct plateau which we model with a number of parameters. This model is used to identify horizontal and vertical line segments within an X-Ray corresponding to a bullet signature. Regions containing confluences of these line segments are selected as bullet candidates. The actual bullet is thresholded out of the region based on a range of intensities occupied by the intensity profiles that contributed to the region. A simple Volume Reconstruction algorithm is implemented that back-projects the silhouettes of bullets obtained from our segmentation technique. This algorithm operates on a 3D voxel volume represented as an octree. The reconstruction is reduced to the 2D case by reconstructing a slice of the voxel volume at a time. We achieve good results for our segmentation algorithm. When compared with a manual segmentation, our algorithm matches 90% of the bullet pixels in nine of the twelve test X-rays. Our reconstruction algorithm produces an acceptable results: It achieves a 70% match for a test case where we compare a simulated bullet with a reconstructed bullet.
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40

Watts, Philip. "Parametric study of vapor explosions using flash x-rays." Thesis, McGill University, 1994. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=22682.

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The effect of fluid properties on the fragmentation behavior of a single molten metal drop interacting explosively with coolant has been investigated experimentally with high-speed regular photography and flash x-ray radiography to visualize the bubble dynamics and drop fragmentation, respectively. Single (0.5 g) drops of tin, bismuth, gallium and Cerrolow heated to between 600-800$ sp circ$C interacting with water at 70$ sp circ$C were investigated. Comparison of the x-ray radiographs shows that in each case the fragmentation occurs in two stages (corresponding to two bubble oscillations). Similar vapor explosions were also observed for molten tin drops interacting with 1-propanol, although the period and amplitude of bubble oscillations both decreased. For 0.1 g aluminum drops heated to 900$ sp circ$C and dropped in water, only a single large interaction was observed.
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Willatt, A. J. "Specular reflection of neutrons and X-rays from interfaces." Thesis, University of Oxford, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.235074.

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42

Wilson, Colin David. "X-rays from Compton scattering around accreting black holes." Thesis, Durham University, 2002. http://etheses.dur.ac.uk/4097/.

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Compton scattering is one of the most important radiation processes from accreting compact objects. Hard X-rays can be produced by Compton upscattering of soft seed photons from the accretion disk. Here we use both theoretical and observational methods to investigate the hard X-ray emission around accreting Black Holes. We attempt to observationally constrain the geometry of the accretion flow using the observed spectra from the outburst of a transient black hole. The rapid rise of the hard X-ray flux is almost certainly associated with most of the disk mass moving inwards, so the optically thick disk should not extend down to the last stable orbit until the outburst peak. The low/hard state is seen at the start of the rise showing that this is probably associated with a truncated disk. Attempts to derive the inner disk radius from reflection model parameters are inconclusive due to the effects of ionization. We describe a new approach to numerically modelling Compton scattering around accreting sources by solving the distribution functions. This approach (based on work by Guilbert 1981) involves breaking the scattering into individual segments of space and time. We show how a coarse angle grid can be adapted to mimic an arbitrarily fine grid with very little increase in run-time. The resulting code automatically includes time dependent behaviour. We extend the code to calculate the time dependent, self consistent electron distribution resulting from the Compton cooling. This can be used even where the Compton cooling time is shorter than the light crossing time. We show that any system in which the seed photons are dominated by reprocessing should produce soft lags of the order of the light crossing time. Future observations, with more sophisticated satellites, may be able to identify this lag.
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43

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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44

Shand, Matthew. "Microstructured Optical Arrays for use with soft X-rays." Thesis, King's College London (University of London), 2012. https://kclpure.kcl.ac.uk/portal/en/theses/microstructured-optical-arrays-for-use-with-soft-xrays(14a67e6f-2564-4c1d-afd5-96d5e748892b).html.

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Zone plates are commonly used in soft X-ray microscopy due to the high spatial resolutions achievable, however the performance is somewhat limited due to their small numerical aperture, combined with chromatic aberration and the multiple diffraction orders that are produced. Microstructured Optical Arrays (MOAs) have been proposed as an alternative method of focusing soft X-rays, using grazing incidence reflections from an array of channels, with the cumulative effect producing a small focused spot. The development and focusing properties of MOAs are described and simulated within this thesis, with comparison made to zone plates and other methods of focusing X-rays. -- Experimental characterisation of MOAs and zone plates was achieved using a microfocused electron bombardment X-ray source. Necessary developments required to examine MOAs using the X-ray source and detector system are described, along with current calibration measurements, providing insight into the overall performance of the source. -- The use of a CCD detector with the microfocus source has allowed comparison to be made between experimental measurements made to characterise the optical performance of MOAs and computer simulation.
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45

Hemantha, Rao Kavya. "Laser produced plasmas for the generation of X-rays." Thesis, Griffith University, 2019. http://hdl.handle.net/10072/385616.

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Laser Produced Plasmas (LPP) are a better source to increase the energy cut-off of the harmonics generated due to their larger ionisation potential than the conventional neutral gas media, if optimised properly. The experiments detailed in the thesis aim towards the use of LPP as a medium for the generation of bright coherent EUV/XUV table-top sources. A detailed spatio-temporal characterisation of LPP's generated from Al and Cr targets via non-invasive optical emission spectroscopy (OES) and time-resolved plume imaging are performed to investigate plasma features and optimise them. While ns LPP's are spatio-temporally optimised for Al IV/Al III with the irradiation energy as the control parameter, the ps LPP's are optimised for Al III using the single pulse (SP) and double pulse (DP) schemes. Experiments on Cr plasmas are also performed and the changes in plume morphology upon implementing SP and DP schemes are investigated via plume imaging and the abundance of various species in the plume were investigated via time-resolved OES. The DP schemes are investigated in detail to find out the influence of parameters such as the polarisation, delay between the two pulses, energy in the first pulse and the ambient pressure on the plume morphology. Building and extending the experimental setup to conduct the proposed experiments aiming towards increasing the energy cut-off of the harmonics using LPP as the nonlinear medium comprises the second part of the thesis. A High-order Harmonic Generation (HHG) set up is built and tested using harmonics generated in Ar gas. The HHG system developed here would further be modified to take care of the plasma fluorescence as well as to accommodate higher order harmonics. These spatio-temporally optimised LPP's together with the set-up are anticipated to produce HHG sources with higher brilliance than the commercial tabletop sources, adding energy tunability to these sources. Additional experiments on the angle resolved X-ray emissions in the range of 30 keV to 150 keV from LPP from metals (Al and Cr) and their alloys (Al-Cr) are carried out and detailed here; which can also be used as a source of X-ray radiation.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Environment and Sc
Science, Environment, Engineering and Technology
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46

Dutcher, John Robert. "Low temperature x-ray diffraction studies of TaS₂ and LixTiS₂." Thesis, University of British Columbia, 1985. http://hdl.handle.net/2429/24632.

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A low temperature x-ray powder diffraction attachment for use on the vertical goniometer of a diffractometer is described. We have found that diffraction patterns obtained with the attachment mounted on the goniometer are of comparable quality to those obtained on the goniometer itself. Using this attachment, the lattice parameter discontinuities associated with a charge density wave phase transition in 1T-TaS₂ near T=200K are measured with an accuracy greater than that of any previous results. Electrochemically prepared samples of Li xTiS₂ near x=0.16 are studied at room temperature and below. Clear evidence for the formation of a stage two superlattice at low temperatures was not obtained.
Science, Faculty of
Physics and Astronomy, Department of
Graduate
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47

Negusse, Ezana. "X-ray characterization of buried layers and interfaces in EuO based spin-filter tunnel junctions." Thesis, Montana State University, 2008. http://etd.lib.montana.edu/etd/2008/negusse/NegusseE0508.pdf.

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Spin filtering tunnel junctions provide a convenient method for controlling and manipulating the spin of electrons in spintronic devices. In a tunnel junction, the tunneling current depends exponentially on the thickness of the tunneling barrier. Ultrathin (~20 angstroms) barriers are highly desirable because they lower the junction resistance. In addition to the barrier thickness, the spin filtering efficiency of the junction depends on the tunneling barrier\'s magnetic properties and the nature of the barrier-electrode interfaces. EuO\'s high TC (69 K) and large exchange splitting (2 ΔE = 0.54 eV) in the conduction band make it a material of choice for achieving a spin-polarized tunneling current. We examined the properties of ultrathin EuO films of different thicknesses with different electrodes. The chemical and magnetic characterization of buried layers and buried interfaces was done using interface sensitive x-ray techniques with element specificity and magnetic contrast. Of the many materials studied, we found that yttrium overlayers are the best electrodes to protect the EuO barrier and prevent formation of Eu2O3, a stable nonmagnetic oxide, at the top (EuO-electrode) interface. We examined the electrode-EuO interfaces of EuO films with Cu bottom electrode deposited on Cr/Cu buffer layer. We found that the roughness of the top and bottom interfaces (above and below the EuO layer) is random and nonconformal in nature. EuO films grown on Cr/Cu buffer layer have smoother top interfaces compared to those deposited directly on Si substrate or Al bottom electrode. Moreover, compared to the Cr/Cu or Cu/EuO interfaces, the top (EuO-electrode) interface is smoother. Here we present results from chemical and magnetic characterization of ultrathin EuO film and the impact of reduced barrier thickness on the magnetic properties of the ferromagnetic tunneling barrier.
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48

Armstrong, Nicholas. "Application of the maximum entropy method to x-ray profile analysis /." Electronic version, 1999. http://adt.lib.uts.edu.au/public/adt-NTSM20031204.135221/index.html.

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49

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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50

Tangouna, Liambo Bissa Marie-Louise. "Host-guest compounds : structure and thermal behaviour." Thesis, Cape Peninsula University of Technology, 2016. http://hdl.handle.net/20.500.11838/2442.

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Thesis (MTech (Chemistry))--Cape Peninsula University of Technology, 2016.
Inclusion compounds of two hydroxyl hosts with a variety of guests have been investigated. These host compounds are bulky molecules and have the ability to interact with smaller organic guests to form new compounds. The host 9-(1-naphthyl)-9H-xanthen-9-ol (H1), forms inclusion compounds with pyridine (PYR), N,N-dimethylacetamide (DMA), morpholine (MORP) and N-methyl-2-pyrrolidinone (NMP). The crystal structures of H1•NMP, H1•DMA and H1•MORP1 were successfully solved in the triclinic space group PĪ, whereas the inclusion compound H1•PYR crystallised in the monoclinic space group P21/c. A different inclusion compound involving morpholine, H1•MORP2 resulted from dissolution of H1 in a 1:1 molar ratio of MORP: DMA. H1•MORP2 crystallised in the space group PĪ. All of the abovementioned inclusion compounds demonstrated a host: guest ratio of 1:1 except for H1•MORP1 (host: guest ratio = 1: ). H1 interacts with pyridine and morpholine guests via (Host)O-H•••N(Guest) hydrogen bonds and via (Host)OH•••O(Guest) hydrogen bonds with N-methyl-2-pyrrolidinone and N,N-dimethylacetamide.
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