Dissertations / Theses on the topic 'X-ray diffraction'
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1
Zora, J. A. "X-ray diffraction studies." Thesis, University of Sussex, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.374467.
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Hinrichsen, Bernd. "Two-dimensional X-ray powder diffraction." [S.l. : s.n.], 2007. http://nbn-resolving.de/urn:nbn:de:bsz:93-opus-33946.
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Genetu, Teggen Linda. "Material identification using X-ray diffraction." Thesis, Mittuniversitetet, Institutionen för elektronikkonstruktion, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:miun:diva-37122.
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This study reviews the theoretical and experimental aspects of the X-ray diffraction (XRD) technique and evaluates its use in identifying toxic elements or compounds in waste that has been incinerated. Many industries incinerate materials that contain large significant amounts of toxic elements, and these elements should be identified and re-moved to reduce environmental pollution. The aim of this project is to identify the elemental content of an incinerated ash sample, and to recommend a proper identification method when using XRD. Here, we test two ash samples (raw ash without any treatment and ash that has been stabilized by washing) using the software DIFFRAC.EVA that is integrated into Bruker’s diffractometer D2Phaser to match different diffraction patterns to identify the contents of the ash sample. Finally concluding the results XRF is more suitable than XRD for ash surveil-lance.
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R, N. C. Maia Filipe. "Ultrafast Coherent X-ray Diffractive Nanoimaging." Doctoral thesis, Uppsala universitet, Molekylär biofysik, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-122002.
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X-ray lasers are creating unprecedented research opportunities in physics,chemistry and biology. The peak brightness of these lasers exceeds presentsynchrotrons by 1010, the coherence degeneracy parameters exceedsynchrotrons by 109, and the time resolution is 105 times better. In theduration of a single flash, the beam focused to a micron-sized spot has the samepower density as all the sunlight hitting the Earth, focused to a millimetresquare. Ultrafast coherent X-ray diffractive imaging (CXDI) with X-ray lasers exploitsthese unique properties of X-ray lasers to obtain high-resolution structures fornon-crystalline biological (and other) objects. In such an experiment, thesample is quickly vaporised, but not before sufficient scattered light can berecorded. The continuous diffraction pattern can then be phased and thestructure of a more or less undamaged sample recovered% (speed of light vs. speed of a shock wave).This thesis presents results from the first ultrafast X-ray diffractive imagingexperiments with linear accelerator-driven free-electron lasers and fromoptically-driven table-top X-ray lasers. It also explores the possibility ofinvestigating phase transitions in crystals by X-ray lasers. An important problem with ultrafast CXDI of small samples such as single proteinmolecules is that the signal from a single measurement will be small, requiringsignal enhancement by averaging over multiple equivalent samples. We present anumerical investigation of the problems, including the case where samplemolecules are not exactly identical, and propose tentative solutions. A new software package (Hawk) has been developed for data processing and imagereconstruction. Hawk is the first publicly available software package in thisarea, and it is released as an open source software with the aspiration offostering the development of this field.
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Dicken, A. "Diffraction enhanced kinetic depth X-ray imaging." Thesis, Department of Engineering and Applied Science, 2013. http://dspace.lib.cranfield.ac.uk/handle/1826/8046.
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An increasing number of fields would benefit from a single analytical probe that can characterise bulk objects that vary in morphology and/or material composition. These fields include security screening, medicine and material science. In this study the X-ray region is shown to be an effective probe for the characterisation of materials. The most prominent analytical techniques that utilise X-radiation are reviewed. The study then focuses on methods of amalgamating the three dimensional power of kinetic depth X-ray (KDFX) imaging with the materials discrimination of angular dispersive X-ray diffraction (ADXRD), thus providing KDEX with a much needed material specific counterpart. A knowledge of the sample position is essential for the correct interpretation of diffraction signatures. Two different sensor geometries (i.e. circumferential and linear) that are able to collect end interpret multiple unknown material diffraction patterns and attribute them to their respective loci within an inspection volume are investigated. The circumferential and linear detector geometries are hypothesised, simulated and then tested in an experimental setting
with the later demonstrating a greater ability at discerning between mixed diffraction patterns produced by differing materials. Factors known to confound the linear diffraction method such as sample thickness and radiation energy have been explored and quantified with a possible means of mitigation being identified (i.e. via increasing the sample to detector distance). A series of diffraction patterns (following the linear diffraction appoach) were obtained from a single phantom object that was simultaneously interrogated via KDEX imaging. Areas containing diffraction signatures matched from a threat library have been highlighted in the KDEX imagery via colour encoding and match index is inferred by intensity. This union is the first example of its kind and is called diffraction enhanced KDEX imagery. Finally an additional source of information obtained from object disparity is explored as an alternative means of calculating sample loci. This offers a greater level of integration between these two complimentary techniques as object disparity could be used to reinforce the results produced by the linear diffraction geometry.
6
Kegel, Ingo. "X-ray diffraction from semiconductor quantum dots." Diss., [S.l.] : [s.n.], 2000. http://edoc.ub.uni-muenchen.de/archive/00000330.
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Escudero, Adán Eduardo Carmelo. "High resolution X-ray single crystal diffraction." Doctoral thesis, Universitat Rovira i Virgili, 2018. http://hdl.handle.net/10803/586278.
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Aquesta tesi doctoral descriu l'ús de dades d'alta resolució de difracció de raigs X de monocristall per a la
obtenció de mapes experimentals detallats de distribució de densitat de càrrega. Aquests mapes serveixen per
evidenciar experimentalment l'existència d'interaccions intra- i inter-moleculars febles dins de l'estructura
del vidre. Els mapes de densitat de càrrega s'obtenen mitjançant un refinament multipolar de l'estructura
cristal·lina. En concret, aquest treball se centra en evidenciar experimentalment les interaccions atractives no
covalent recentment descrites teòricament i que donen lloc a la formació d'enllaços de tipus "sigma i pi hole".
Els termes enllaços de Triel, tetrel, pnictogen i chalcogen van ser recentment introduïts per referir-se a aquestes
interaccions en funció del grup (14, 15 i 16) al qual pertany l'àtom implicat com a centre electrofílic. el
fet que aquestes interaccions siguin molt febles fa necessari l'obtenció de mapes de densitat electrònica
molt precisos. També s'han utilitzat aquests mapes de densitat electrònica per determinar experimental el
moment quadrupolar i el potencial electrostàtic molecular d'una sèrie d'anells de fenil amb diferents
substituents. Les dades experimentals obtingudes d'aquesta manera han servit per validar els resultats de càlculs
teòrics.Esta tesis doctoral describe el uso de datos de alta resolución de difracción de rayos X de monocristal para la obtención de mapas experimentales detallados de distribución de densidad de carga. Estos mapas sirven para evidenciar experimentalmente la existencia de interacciones intra- e inter-moleculares débiles dentro de la estructura del cristal. Los mapas de densidad de carga se obtienen mediante un refinamiento multipolar de la estructura cristalina. En concreto, este trabajo se centra en evidenciar experimentalmente las interacciones atractivas no covalente recientemente descritas teóricamente y que dan lugar a la formación de enlaces de tipo "sigma y pi hole". Los términos enlaces de Triel, tetrel, pnictogen y chalcogen fueron recientemente introducidos para referirse a estas interacciones en función del grupo (14, 15 y 16) al que pertenece el átomo implicado como centro electrofílico. El hecho de que estas interacciones sean muy débiles hace necesario la obtención de mapas de densidad electrónica muy precisos. También se han utilizado estos mapas de densidad electrónica para determinar experimental el momento cuadrupolar y el potencial electrostático molecular de una serie de anillos de fenilo con diferentes sustituyentes. Los datos experimentales obtenidos de esta forma han servido para validar los resultados de cálculos teóricos.
radiación de molibdeno para asignar la configuración absoluta de una serie de moléculas orgánicas. Las moléculas medidas fueron seleccionadas teniendo en cuenta que el elemento más pesado de su composición química fuera el oxígeno. Es bien conocido que la dispersión anómala de este tipo de compuestos es muy débil y dificulta la asignación de configuración absoluta mediante esta técnica. El resultados de este trabajo demuestran que la metodología empleada es muy efectivo para poder asignar inequívocamente la configuración absoluta correcta en este tipo de moléculas. This thesis uses high resolution single crystal X-ray diffraction data in order to obtain experimental detailed charge density distribution maps that can exhibit intra and intermolecular interactions. The charge density maps are obtained through the multipolar refinement. Particularly, this work focuses in lasts classified non-covalent attractive interactions due to sigma and pi holes, triel, tetrel, pnictogen and chalcogen bonds. The weakness of these interactions make necessary very accurate and precise maps. In the same manner, in this works they have been determined the quadrupolar moment and the molecular electrostatic potential of a series of phenyl rings substituted with different chemical groups. The experimental data obtained in this way have been used to validate theoretical predictions. Eventually in this work, high resolution single crystal X-ray diffraction data using molybdenum radiation has been employed to assign the absolute configuration of a series of organic molecules. The measured molecules were selected containing oxygen as heaviest atom since the anomalous dispersion of these kind of compounds is very weak. The use of high resolution data has been proved to be effective in order to unequivocally assign the correct absolute configuration in this kind of molecules.
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Anderoglu, Osman. "Residual stress measurement using X-ray diffraction." Texas A&M University, 2004. http://hdl.handle.net/1969.1/1507.
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This paper briefly describes the theory and methods of x-ray residual stress
measurements.
Residual stresses can be defined as the stresses which remain in a material in the
absence of any external forces. There are many stress determination methods. Some of
those methods are destructive and some are nondestructive. X-ray residual stress
measurement is considered as a nondestructive method.
X-ray diffraction together with the other diffraction techniques of residual stress
measurement uses the distance between crystallographic planes as a strain gage. The
deformations cause changes in the spacing of the lattice planes from their stress free
value to a new value that corresponds to the magnitude of the residual stress. Because of
Poissons ratio effect, if a tensile stress is applied, the lattice spacing will increase for
planes perpendicular to the stress direction, and decrease for planes parallel to the stress
direction. This new spacing will be the same in any similarly oriented planes, with
respect to the applied stress. Therefore the method can only be applied to crystalline,
polycrystalline and semi-crystalline materials.
The diffraction angle, 2θ, is measured experimentally and then the lattice spacing
is calculated from the diffraction angle, and the known x-ray wavelength using Bragg's
Law. Once the d-spacing values are known, they can be plotted versus 2 sin ψ, ( ψ is the
tilt angle). In this paper, stress measurement of the samples that exhibit a linear behavior
as in the case of a homogenous isotropic sample in a biaxial stress state is included. The
plot of d vs. 2 sin ψ is a straight line which slope is proportional to stress. On the other
hand, the second set of samples showed oscillatory d vs. 2 sin ψ behavior. The oscillatory
behavior indicates the presence of inhomogeneous stress distribution. In this case the xray
elastic constants must be used instead of E and ν values. These constants can be
obtained from the literature for a given material and reflection combination. It is also
possible to obtain these values experimentally. Calculation of the residual stresses for
these samples is beyond the scope of this paper and will not be discussed here.
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Falch, Thomas Løfsgaard. "3D Visualization of X-ray Diffraction Data." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for datateknikk og informasjonsvitenskap, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-18903.
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X-ray diffraction experiments are used extensively in the sciences to study the structure, chemicalcomposition and physical properties of materials. The output of such experiments are samples of thediffraction pattern, which essentially constitutes a 3D unstructured dataset. In this thesis, wedevelop a method for visualizing such datasets.Our visualization method is based on volume ray casting, but operates directly on the unstructuredsamples, rather than resampling them to form voxels. We estimate the intensity of the X-raydiffraction pattern at points along the rays by interpolation using nearby samples, taking advantageof an octree to facilitate efficient range search. The method is implemented on both the CPUand the GPU.To test our method, actual X-ray diffraction datasets is used, consisting of up to 120M samples.We are able to generate images of good quality. The rendering time varies dramatically, between 5 sand 200 s, depending upon dataset, and settings used. A simple performance model is developedand empirically tested to better understand this variation. Our implementation scales exceptionallywell to more CPU cores, with a speedup of 5.9 on a 6-core CPU. Furthermore, the GPU implementationachieves a speedup of around 4.6 compared to the CPU version.
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He, Baoping. "X-ray diffraction from point-like imperfection." Diss., This resource online, 1992. http://scholar.lib.vt.edu/theses/available/etd-09232008-144700/.
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Duke, Elizabeth Mary Helen. "X-ray diffraction studies on glycogen phosphorylase." Thesis, University of Oxford, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.336092.
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Karacan, Ismail. "X-ray diffraction studies of aromatic fibres." Thesis, University of Leeds, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.329219.
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Hubbard, Steven Robert. "X-ray diffraction studies of crystalline DNA." Thesis, University of York, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.259840.
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Welsh, Liam Christopher Oswin. "X-ray diffraction studies of filamentous bacteriophages." Thesis, University of Cambridge, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.627349.
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Ndieyira, Joseph Wafula. "X-ray diffraction studies of electrode surfaces." Thesis, University of Cambridge, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.624193.
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Palma, Joseph John. "X-ray Diffraction Studies of Amorphous Materials." Diss., Temple University Libraries, 2013. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/231213.
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PhysicsPh.D.
This thesis presents a study on two types of X-ray diffraction methodologies applied to the characterization of amorphous materials. The purpose of this study was to assess the feasibility of measuring the diffractive spectrum of amorphous materials by Energy-Dispersive X-ray Diffraction (EDXRD) utilizing Cadmium Zinc Telluride detectors. The total scattering intensity (coherent plus incoherent scatter) spectra precisely measured by high-energy Wide-Angle X-ray Scattering (WAXS) were compared to the EDXRD spectra to determine the level of agreement between the two techniques. The EDXRD spectra were constructed by applying a spectra fusing technique which combined the EDXRD spectra collected at different scattering angles rendering a continuous total scattering spectrum. The spectra fusing technique extended the momentum transfer range of the observed scattered spectrum beyond the limitations of the X-ray source and CZT detection efficiencies. Agreement between the WAXS and fused EDXRD spectra was achieved. In addition, this thesis presents the atomic pair correlation functions and coordination numbers of the first coordination shell for four hydrogen peroxide solutions of varying mass concentrations using Empirical Potential Structural Refinement (EPSR). The results are compared to the state-of-the art ad initio quantum mechanical charge field molecular dynamics (QMCF MD) model of the hydrogen peroxide in solution to support the model's predictions on why hydrogen peroxide is stable in water. The EPSR results using the coherent scattering intensity calculated from the WAXS data set predicts a hydration shell of 6.4 molecules of water surrounding hydrogen peroxide. The results also indicate that hydrogen peroxide is more likely to behave as a proton donor than acceptor. These findings are in agreement with QMCF MD model of aqueous hydrogen peroxide.
Temple University--Theses
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Majumder, Bimal. "X-ray diffraction studies on liquid crystals." Thesis, University of North Bengal, 1988. http://hdl.handle.net/123456789/667.
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Gorman, Martin Gerard. "X-ray diffraction studies of shock compressed bismuth using X-ray free electron lasers." Thesis, University of Edinburgh, 2016. http://hdl.handle.net/1842/25865.
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The ability to diagnose the structure of a material at extreme conditions of high-pressure and high-temperature is fundamental to understanding its behaviour, especially since it was found that materials will adopt complex crystal structures at pressures in the Terapascal regime (1TPa). Static compression, using the diamond anvil cell coupled with synchrotron radiation has to date been the primary method for structural studies of materials at high pressure. However, dynamic compression is the only method capable of reaching pressures comparable to the conditions found in the interior of newly discovered exo-planets and gas giants where such exotic high-pressure behaviour is predicted to be commonplace among materials. While generating extreme conditions using shock compression has become a mature science, it has proved a considerable experimental challenge to directly observe and study such phase transformations that have been observed using static studies due to the lack of sufficiently bright X-ray sources. However, the commissioning of new 4th generation light sources known as free electron lasers now provide stable, ultrafast pulses of X-rays of unprecedented brightness allowing in situ structural studies of shock compressed materials and their phase transformation kinetics in unprecedented detail. Bismuth, with its highly complex phase diagram at modest pressures and temperatures, has been one of the most studied systems using both static and dynamic compression. Despite this, there has been no structural characterisation of the phases observed on shock compression and it is therefore the ideal candidate for the first structural studies using X-ray radiation from a free electron laser. Here, bismuth was shock compressed with an optical laser and probed in situ with X-ray radiation from a free electron laser. The evolution of the crystal structure (or lack there of) during compression and shock release are documented by taking snapshots of successive experiments, delayed in time. The melting of Bi on release from Bi-V was studied, with precise time scans showing the pressure releasing from high-pressure Bi-V phase until the melt curve is reached off-Hugoniot. Remarkable agreement with the equilibrium melt curve is found and the promise of this technique has for future off-Hugoniot melt curve studies at extreme conditions is discussed. In addition, shock melting studies of Bi were performed. The high-pressure Bi - V phase is observed to melt along the Hugoniot where melting is unambiguously identified with the emergence of a broad liquid-scattering signature. These measurements definitively pin down where the Hugoniot intersects the melt curve - a source of some disagreement in recent years. Evidence is also presented for a change in the local structure of the liquid on shock release. The impact of these results are discussed. Finally, a sequence of solid-solid phase transformations is observed on shock compression as well as shock release and is detected by distinct changes in the obtained diffraction patterns. The well established sequence of solid-solid phase transformations observed in previous static studies is not observed in our experiments. Rather, Bi is found to exist in some metastable structures instead of forming equilibrium phases. The implications these results have for observing reconstructive phase transformations in other materials on shock timescales are discussed.
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Dicken, Anthony. "Diffraction enhanced kinetic depth effect X-ray imaging." Thesis, Cranfield University, 2011. http://dspace.lib.cranfield.ac.uk/handle/1826/8046.
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An increasing number of fields would benefit from a single analytical probe that can characterise bulk objects that vary in morphology and/or material composition. These fields include security screening, medicine and material science. In this study the X-ray region is shown to be an effective probe for the characterisation of materials. The most prominent analytical techniques that utilise X-radiation are reviewed. The study then focuses on methods of amalgamating the three dimensional power of kinetic depth X-ray (KDFX) imaging with the materials discrimination of angular dispersive X-ray diffraction (ADXRD), thus providing KDEX with a much needed material specific counterpart. A knowledge of the sample position is essential for the correct interpretation of diffraction signatures. Two different sensor geometries (i.e. circumferential and linear) that are able to collect end interpret multiple unknown material diffraction patterns and attribute them to their respective loci within an inspection volume are investigated. The circumferential and linear detector geometries are hypothesised, simulated and then tested in an experimental setting with the later demonstrating a greater ability at discerning between mixed diffraction patterns produced by differing materials. Factors known to confound the linear diffraction method such as sample thickness and radiation energy have been explored and quantified with a possible means of mitigation being identified (i.e. via increasing the sample to detector distance). A series of diffraction patterns (following the linear diffraction appoach) were obtained from a single phantom object that was simultaneously interrogated via KDEX imaging. Areas containing diffraction signatures matched from a threat library have been highlighted in the KDEX imagery via colour encoding and match index is inferred by intensity. This union is the first example of its kind and is called diffraction enhanced KDEX imagery. Finally an additional source of information obtained from object disparity is explored as an alternative means of calculating sample loci. This offers a greater level of integration between these two complimentary techniques as object disparity could be used to reinforce the results produced by the linear diffraction geometry.
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Heitner, Gabriele Heike. "Multiple scattering for diffraction enhanced X-ray imaging." [S.l. : s.n.], 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=976522632.
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Wrålsen, Arnt Joakim. "X-ray diffraction studies of InAs/GaAs heterostructures." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for elektronikk og telekommunikasjon, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-18348.
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Intermediate band solar cells (IBSC) is a proposed new type of solar cell device that has an intermediate energy band in the band gap. One possible implementation of IBSCs is by using arrays of nano-sized semiconductor particles known as quantum dots (QDs). InAs QDs can be grown on GaAs by using molecular beam epitaxy (MBE). As a part of this growth process, an InAs wetting layer (WL) is formed on which the InAs QDs grow. One possible method of determining the WL thickness is by using x-ray diffraction (XRD), which is a non-destructive analysis technique used to extract information about the structure and composition of crystalline thin films.An InAs/GaAs bilayer sample grown by MBE was investigated. This sample was grown without rotation, meaning the thicknesses of the deposited layers are expected to exhibit a gradient across the sample. Based on the geometry of the MBE machine, the variation in deposited thicknesses across the sample was estimated to be ±3.4% for InAs and ±4.2% for GaAs. XRD rocking curve measurements were performed around the 004 reflection in thirteen different locations on this sample. LEPTOS software was used to simulate XRD curves, and these simulations were fitted to the XRD measurements by varying the thicknesses of the simulated InAs and GaAs layers. It was found that the GaAs thicknesses across the sample varied as expected, while the variation in InAs thicknesses was much larger than expected. It was also found that the measured thicknesses of the InAs layer were significantly thinner than the nominal value. This is a strong indication that there are QDs on the sample, and that only the WL of the QDs contributes to the x-ray curve.LEPTOS was also used to simulate several cases of alloying of an InAs/GaAs bilayer. It was found that if the entire InAs layer is segregated into an InAs/GaAs alloy, this causes the diffraction peaks to weaken as the InAs/GaAs interfaces become less abrupt. It was also found that intermixing causes a significant change in the XRD curve because the amount of GaAs in the InAs/GaAs bilayer structure increases.
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Walker, Christopher John. "X-ray diffraction of some technologically important surfaces." Thesis, University of Leicester, 2001. http://hdl.handle.net/2381/30655.
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Surface X-ray diffraction (SXRD) has been used to study the effect of pressure and temperature on the Ni(110)-(2x1)-2CO reconstruction and the effect of temperature on the InSb(001)-c(8x2) reconstruction. The Ni(110)-(2x1)-2CO reconstruction was observed at a carbon monoxide pressure of 2.3 bar and has a structure unchanged from that at 1 x 10 -5 mbar. This structure was found to consist of CO molecules near short bridge sites in agreement with other recent studies in high vacuum conditions. Heating at 1 x 10-5 mbar causes a lifting of the (2x1) reconstruction due to desorption of the CO. In contrast, heating in 2.3 bar of CO leads to a massive rearrangement of the surface and the formation of {111} microfacets. The base of the microfacets is ≈100 A across and their surfaces are disrupted from the bulk terminated (111) surface. This is consistent with an enlargement of the lattice due to the dissolution of carbon in the facets. SXRD and LEED experiments on the c(8x2) reconstruction of InSb (001) show no structural changes on cooling from room temperature to 74K. Key features of the reconstruction are determined which are at variance with the recent model of Jones et al.
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Mancuso, Adrian P. "Experimental phase retrieval using coherent x-ray diffraction /." Connect to thesis, 2005. http://eprints.unimelb.edu.au/archive/00001775.
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Stewart, Alexander. "Reflections from muscle : an x-ray diffraction study." Thesis, University of Oxford, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.334921.
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Khudheyer, F. Y. "Study of X-ray photoelectron diffraction in crystals." Thesis, Swansea University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.637793.
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Photoelectron diffraction pattern is one of a number of surface-structure probes to knowledge of the atomic positions, identities and bonding mechanisms within few layers of the surface. The high-energy forward scattering version of photoelectron diffraction called X-Ray photoelectron diffraction (XPD). XPD features can be described theoretically by a simple single-scattering cluster model (SSC), which used either spherical wave (SW) or plane wave (PW) approximation. X-Ray photoelectron diffraction offers a direct method of determining interatomic bond directions in the surface region of a solid. Single Scattering Cluster theory with Plane Wave approximation (SSC-PW) is simple and reliable mean of interpreting XPD data, but it tends to overestimate the peak heights. The plane wave approximation developed by Lee and Fadley, but this developing is appropriate for photoemission from a s-core orbital. Parry modified this theory which takes account of the core sub-shell having non-zero orbital angular momentum lc. At typical XPD energies, k is large enough to make many partial waves phase shifts significant and this has encouraged use instead of scattering amplitudes as in Fadley's theory. This implies ignoring all terms in each Hankel function expansion, apart from the leading one eikr/r. The corrections become progressively more important with increasing l. We are investigating, in this thesis, the importance of including, order by order, successive non-asymptotic terms in each Hankel function expansion and to see if thereby a successful theory can be set up without having to modify mean free path, and possibly without the complication of Debye-Waller factors. The new technique needs phase shifts to describe all the scattering processes that arise. In this thesis, we give a description of our fitting method and tabulate the phase shifts in an appendix. Trial calculations on simple systems (C-C, Cu-Cu, Ni-Ni and Si-Si) have been made and compared with predictions of Fadley theory. This work include application to some simple well defined cases e.g. photoemission from monolayer of Cu on Ni substrate and sandwich structure. We compared the results with experiment results. Photoemission from single crystals of elements (Cu and Si), and binary compounds (NaCl, LiF, ZnSe and GaAs) has been studied by our new technique and comparison with another experiment data and theoretical calculations has been made.
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Griffiths, Jennifer Ann. "X-ray diffraction measurements for breast tissue analysis." Thesis, University College London (University of London), 2005. http://discovery.ucl.ac.uk/1444776/.
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Biological tissues exhibit elastic x-ray scatter properties unique to individual tissue types. It has been suggested that these properties could be exploited in the discrimination of tissues in diagnostic radiology, particularly in mammographic imaging. The work in this thesis investigates the elastic scatter from human breast tissues with a view to moving the Diffraction Enhanced Breast Imaging (DEBI) technique towards the clinical domain. Instrumentation was considered in terms of a suitable scatter detector and its associated collimation. A phosphor coated low-light-level CCD in conjunction with a parallel hole array collimator was introduced as a possible angular dispersive diffraction detector, and conically collimated HPGe was found to be a suitable detector for energy dispersive diffraction. Diffraction imaging was achieved using both planar and tomographic imaging techniques. The planar imaging considered the spatial resolution needed for clinically useful results and showed that depth information of the order of 1 cm can easily be obtained using diffraction imaging techniques. A micro-tomographic diffraction imaging technique was used to further present knowledge of the 'scatter signatures' of human breast tissue. The tissue is naturally inhomogeneous, so precise knowledge of a sample's composition is needed in order to accurately classify its scatter signature. A total of twenty seven breast tissue samples were examined, covering a range of tissue types, with nineteen of these samples being extensively studied. The microCT produced diffraction images of the inhomogeneous tissue samples and their diffraction signatures were related to the results of conventional histopathological analysis. A correlation was observed between the predominant tissue type in a sample and the ratio of the intensity of the sample's scatter at momentum transfers of 1.1 and 1.5 nm-1. A Student's t-test performed on these results gave the probability of a null hypothesis for correlation of less than 1%.
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Dower, C. Siobhan. "X-ray diffraction by near-perfect crystalline surfaces." Thesis, University of Edinburgh, 1994. http://hdl.handle.net/1842/13707.
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This thesis presents an investigation of the diffraction of x-rays by the types of disordered grating structure which are commonly present on near-perfect crystalline surfaces. Models to calculate the diffraction are developed with the intention of interpreting experimental measurements in terms of both the macroscopic grating structure and the atomic structure. The observability of interference effects from grating structures illuminated by partially coherent radiation is discussed. General kinematical expressions are developed describing the three-dimensional x-ray scattering profile associated with vicinal surfaces with terrace length disorder. Scattering profiles are calculated for specific examples of vicinal surfaces with statistically independent terrace lengths and correlations between terraces are discussed. The analysis of crystal truncation rod (CTR) intensities from vicinal surfaces is considered. The diffraction of x-rays by a reconstructed vicinal surface is investigated for the specific case of the Ge(001) (2x1) surface. It is proposed that an interference modulation of the reconstruction scattering can occur due to ordering in the registration of the reconstructed unit cells on different terraces; a model is developed to simulate the scattering profile. Subdomain structure due to lower symmetry reconstructions is also treated. Data from several Ge(001) surfaces is presented and interpreted in terms of the scattering models. An experimental study of the order-disorder c(4x2) → (2x1) phase transition in the Ge(001) surface reconstruction is described.
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Tian, Yu. "X-ray Diffraction Analysis of with Hydrogen Interstitials." Thesis, Uppsala universitet, Materialfysik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-353796.
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Barium Zirconate is a material valuable in many aspects. Among all the significant characteristics of (BZO), the possibility of hydrogen interstitials is of great importance. With the help of X-ray diffraction analysis, many kinds of structure-related information of a crystal sample can be collected. In this thesis, the XRD pattern of hydrogen induced expansion and contraction of oxygen atoms in the BZO perovskite lattice is investigated both experimentally and theoretically.
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Timonen, T. (Tero). "X-ray diffraction studies of VO₂ thin films." Master's thesis, University of Oulu, 2014. http://jultika.oulu.fi/Record/nbnfioulu-201410281952.
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Abstract. The aim of this work is to investigate the effect of strain in vanadium dioxide (VO₂) thin films. Vanadium dioxide undergoes a metal-insulator transition involving radical changes in the electrical conductivity, and strain is one of the parameters which can influence the transition characteristics. In form of a thin film, vanadium dioxide is subjected to strain which arises from the lattice mismatch between the substrate and the film. To study the effect of strain, a set of vanadium dioxide thin films with thickness from 20 to 240 nm were grown using pulsed laser deposition method, and the structure of the films were characterized using X-ray diffraction. The surface morphology of the thin films was also examined using atomic force microscopy.
In the insulating state, the films were composed of both M₁ and M₂ phases of vanadium dioxide. The transition was observed to be controlled by M₂ phase in films which were thinner than 100 nm and by M₁ phase in thicker films. The presence of M₂ phase was caused by strain. The metal-insulator transition occurred at much wider temperature range in thinner films which were more strained than the thicker films showing more abrupt transitions. The relaxation of the strain in thicker films resulted in misorientation of the crystallites and caused the surface roughness to increase with the film thickness.VO₂ ohutkalvojen röntgendiffraktiotutkimuksia. Tiivistelmä. Tämän työn tarkoituksena on tutkia venymän vaikutusta vanadiinidioksidi (VO₂) ohutkalvoissa. Vanadiinidioksidissa ilmenevä metalli-eriste transitio aiheuttaa suuria muutoksia aineen sähkönjohtavuudessa ja venymän on huomattu vaikuttavan transition ominaisuuksiin. Ohutkalvomuodossa vanadiinidioksidiin kohdistuu venymä, joka aiheutuu kalvon ja substraatin hilavakioiden epäsovituksesta. Venymästä aiheutuvien vaikutusten selvittämiseksi eri paksuisia (20–240 nm) vanadiinidioksidi ohutkalvoja valmistettiin pulssilaserkasvatuksella ja niiden rakennetta karakterisoitiin röntgendiffraktiolla. Myös ohutkalvojen pinnanmuotoa tutkittiin atomivoimamikroskopian avulla.
Eristetilassa kalvot koostuivat vanadiinioksidin M₁ ja M₂ faaseista, ja M₂ faasin huomattiin kontrolloivan transitiota kalvoissa, jotka olivat ohuempia kuin 100 nm, kun taas paksuimmissa kalvoissa transitiota kontrolloi M₁ faasi. M₂ faasin mukanaolo johtui venymästä. Metalli-eriste transitio tapahtui laajemmalla lämpötila-alueella ohuimmissa kalvoissa, joissa venyminen oli suurempaa kuin paksummissa kalvoissa. Paksuimmissa kalvoissa transitio olikin paljon voimakkaampi. Venymän relaksoituminen paksuimmissa kalvoissa johti kiteiden kallistumiseen aiheuttaen sen, että pinnan karheus kasvoi kalvon paksuuden mukana.
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Northey, Thomas. "Ab initio molecular diffraction." Thesis, University of Edinburgh, 2017. http://hdl.handle.net/1842/28772.
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In 1915, Debye derived his well-known equation for the X-ray scattering from a sample of randomly orientated gas-phase molecules. He approximated the molecular scattering by adding the contributions of isolated atomic constituents. This is known as the Independent Atom Model (IAM). However, it omits the redistribution of valence electrons due to bonding, and is limited to the electronic ground state. The main proposition of this thesis is that it is worthwhile going beyond the IAM when interpreting X-ray scattering data. In part, this is motivated by the arrival of new X-ray sources called X-ray Free-Electron Lasers (XFELs). A new method called Ab Initio X-ray Diffraction (AIXRD) is introduced. It calculates the elastic X-ray molecular scattering factor directly from wave functions calculated by ab initio electronic structure theory, for instance Hartree-Fock or multiconfigurational self-consistent field. In this way, the valence electrons are correctly taken into account, and calculations based on electronically excited wave functions become possible. The wave functions must be constructed from spatial orbitals made up of Gaussian-Type Orbitals (GTOs), giving an analytical solution to the Fourier transform integrals involved, and is key to computationally efficient and accurate results. This is compared to a fast Fourier transform (FFT) method, where the electron density is computed on a 3D grid and an FFT algorithm is used to obtain the elastic X-ray molecular scattering factor. Inspired by post-crystallography experiments such as serial femtosecond crystallography and single-particle imaging at XFELs, the AIXRD method is expanded to allow accurate X-ray diffraction calculations from large molecules such as proteins. To make the underlying ab initio problem tractable, the molecule is split into fragments. In other words, the electron density is constructed by a sum of fragment contributions, as is the corresponding molecular form-factor. In this way, it is analogous to the IAM approach except that instead of isolated atoms, there are isolated fragments. A pairwise summation of fragment contributions is also used to account for fragment-fragment interactions. Various fragment definitions are compared based on their effect on the X-ray diffraction signal, and are compared to the IAM method. Finally, X-ray diffraction from molecules in specific quantum states is calculated, revealing a distinct quantum fingerprint in the X-ray diffraction, and a comparison to experiment is made. In particular, the elastic X-ray diffraction is calculated from gas-phase H2 pumped to various electronic, vibrational, and electronic states. This is expanded upon for polyatomic molecules using the harmonic approximation for the vibrational states.
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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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Geraki, Kalotina. "Differentiating normal and diseased breast tissue using X-ray fluorescence and energy dispersive X-ray diffraction." Thesis, City University London, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.274458.
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Davydok, Anton [Verfasser]. "X-ray diffraction analysis of InAs nanowires / Anton Davydok." Siegen : Universitätsbibliothek der Universität Siegen, 2013. http://d-nb.info/1044457511/34.
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Biermanns, Andreas [Verfasser]. "X-ray diffraction from single GaAs nanowires / Andreas Biermanns." Siegen : Universitätsbibliothek der Universität Siegen, 2012. http://d-nb.info/1029241376/34.
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Mina, Golshan. "High-resolution X-ray diffraction studies of synthetic diamond." Thesis, Royal Holloway, University of London, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.271313.
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Lings, Benjamin B. "Ultrafast X-ray diffraction : coherent phonons in bulk semiconductors." Thesis, University of Oxford, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.432286.
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Bolz, Arne [Verfasser]. "X-Ray diffraction on InAs quantum dots / Arne Bolz." Aachen : Shaker, 2004. http://d-nb.info/1170529984/34.
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Rajkumar, Ganeshalingam. "X-ray diffraction analysis and modelling of polycrystalline fibres." Thesis, Imperial College London, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.487950.
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This thesis concerns the development of software techniques for polycrystalline fibre diffraction analysis and the application of the techniques to the determination of the structures of target molecules. Fibre diffraction analysis is one of a powerful method for determining the structure of polycrystalline fibres. However, one of the main shortcomings of this method is the paucity of intensity data; the observed intensities need to be modelled using suitable methods. This particular problem is further complicated by the fact that no direct Fourier synthesis methods can be used because of the cylindrical averaging inherent in fibre diffraction patterns. An attractive strategy is to use software programs for performing semi-automated data extraction from fibre diffraction patterns using refined method of data stripping and modelling. Even though there are some software packages available to do part of this, process the best one, the CCP13 suite, required a great deal of improvement and development. In this thesis, the design, development and applicability of such a software package, FibreFix, are described. Using several practical examples, we show how this software package has aided in solving practical structure-determination problems. Covered in the thesis are: (i) Development,of several techniques as part of the CCP13 software for performing data stripping and structure analysis; (ii) Design and development of a new integrated CCP13 software package, FibreFix, incorporating these techniques; (iii) Evaluation of FibreFix to show that the analysis and modelling processes in data reduction for fibre diffraction can be simplified substantially using the FibreFix software. To show this two different, but related, case studies are described: crystalline natural rubber and E-DNA. Our results show that the structures modelled by the software package are well above our threshold for satisfactory modelling. This claim is supported by very satisfactory X-ray amplitude fitness and in reduction in the R-factor of the models. We have analysed the structure of oriented natural rubber, obtaining a very good fit with the observed X-ray amplitudes and a best R factor of 0.18. We have also analysed different possible models for E-DNA. The R-factors indicate that 172 D-DNA-like models are better than 152 models. We have a found a satisfactory structure for E-DNA, which gives a good fit with the X-ray amplitudes and a best R-factor 0f 28%. This project has substantially, improved the CCP13 fibre analysis software, now all incorporated within FibreFix, which can be used for data stripping of many forms of fibre diffraction pattern. The structures of rubber and E-DNA have also been used as targets to utilize and enhance the capability of the LALS (linked atom least-squares) modelling and refinement program.
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Evans, Shaun Russell. "High-pressure X-ray diffraction studies of light lanthanides." Thesis, University of Edinburgh, 2010. http://hdl.handle.net/1842/7827.
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The (trivalent) lanthanides exhibit a common sequence of phases upon the application of pressure: hcp → dhcp → fcc → “distorted-fcc”. The “distorted-fcc”’ phase (d-fcc), observed in the light lanthanides is known to be related by geometric distortions to the fcc unit cell, yet the d-fcc phase has been reported to comprise of one or two structures, with no prevailing consensus as to the solution(s). This thesis contains a detailed study of the d-fcc phase of the light lanthanides Pr and Nd. High-pressure angle-dispersive powder-diffraction techniques were employed to systematically study the phases adopted by Pr (up to 25GPa) and Nd (up to 44GPa). Particular attention was paid to solving the d-fcc of each of these elements, the structure of which is very unclear in published work. In Pr, the d-fcc between 7 and 20GPa is shown to comprise of two phases, the solutions of which are shown to be hR24 (R¯3m) and oC16 (Ibam) for the regions 7-14GPa and 14-20GPa, respectively. The pressure dependence of each of these structures over their stability range is presented. Revisions to previously-published volume vs. pressure data are made, with a different value for the volume collapse at the 4f electron delocalisation transition reported. Similarly, the d-fcc phase of Nd, stable over the pressure range 16-40GPa, is studied in detail. Nd differs from Pr by undergoing a further transition, to a hP3 (P63) structure, on pressurisation above 40GPa, before transforming to a α-Uranium phase. The distorted-fcc phase is shown, like that of Pr, to comprise of two phases, hR24 (R¯3m) and oC16 (Ibam) for the pressure regions 16-26GPa and 26-40GPa, respectively. Data on Nd are presented up to the maximum pressure achieved, 44GPa. Data from a preliminary study of La are also presented, along with a brief report on attempts to prepare a single crystal of Pr within a diamond anvil cell, by laser annealing of a powder of Pr.
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Gandy, Jonathan Gerard. "An x-ray diffraction study of frog skeletal muscle." Thesis, University of Liverpool, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.243265.
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Hughes, David Stephen. "Polymorphs and solvates of sulfathiazole : X-ray diffraction studies." Thesis, University of Southampton, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.398893.
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Mao, B. W. "In-situ X-ray diffraction studies of electrochemical interfaces." Thesis, University of Southampton, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.378678.
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Leake, S. J. "Coherent X-ray diffraction imaging of zinc oxide crystals." Thesis, University College London (University of London), 2010. http://discovery.ucl.ac.uk/19345/.
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Zinc Oxide (ZnO) exhibits a plethora of physical properties potentially advantageous in many roles and is why it one of the most studied semiconductor compounds. When doped or in its intrinsic state ZnO demonstrates a multitude of electronic, optical and magnetic properties in a large variety of manufacturable morphologies. Thus it is inherently important to understand why these properties arise and the impact potentially invasive sample preparation methods have for both the function and durability of the material and its devices. Coherent X-ray Diffraction Imaging (CXDI) is a recently established non-destructive technique which can probe the whole three dimensional structure of small crystalline materials and has the potential for sub angstrom strain resolution. The iterative methods employed to overcome the `phase problem' are described fully. CXDI studies of wurtzite ZnO crystals in the rod morphology with high aspect ratio are presented. ZnO rods synthesised via Chemical Vapour Transport Deposition were studied in post growth state and during in-situ modification via metal evaporation processing and annealing. Small variations in post growth state were observed, the physical origin of which remains unidentified. The doping of a ZnO crystal with Iron, Nickel and Cobalt by thermal evaporation and subsequent annealing was studied. The evolution of diffusing ions into the crystal lattice from was not observed, decomposition was found to be the dominant process. Improvements in experimental technique allowed multiple Bragg reflections from a single ZnO crystal to be measured for the first time. Large aspect ratio ZnO rods were used to probe the coherence properties of the incident beam. The longitudinal coherence function of the illuminating radiation was mapped using the visibility of the interference pattern at each bragg reflection and an accurate estimate of the longitudinal coherence length obtained, \xi(L) = 0.66\pm 0.02 \mu m. The consequences for data analysis are discussed. The combination of multiple Bragg reflections to realise three dimensional displacement fields was also approached.
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Hughes, Darren John. "X-ray fibre diffraction studies on synthetic DNA analogues." Thesis, Keele University, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.318160.
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Harlow, G. S. "Surface X-ray diffraction studies of the electrochemical interface." Thesis, University of Liverpool, 2016. http://livrepository.liverpool.ac.uk/3003643/.
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This thesis describes the application of in-situ surface X-ray diffraction (SXRD) experiments to the study of electrochemical interfaces. Measurements performed at synchrotron radiation facilities are used to provide in-sight into the surface structure of electrodes and the electrochemical double layer. The impact of structural changes on electrochemical reactivity, and likewise the impact of electrochemical processes on electrode structure are discussed. Measurements of the Au (111) reconstruction in alkaline solution indicate that the presence of CO causes the partial lifting of the reconstruction; it is suggested that this leads to an increase in defects and this is the underlying reason for CO promoted gold catalysis. In-situ SXRD measurements with a non-aqueous electrolyte are presented, representing a technological advance in the study of electrochemical interfaces. Crystal truncation rods (CTRs) measured at the Pt (111) / non-aqueous acetonitrile interface are used to determine the structure of both the electrode surface and the electrolyte close to the interface. The results indicate that acetonitrile undergoes a potential dependant reorientation but, in the presence of molecular oxygen, the acetonitrile molecules close to the electrode are dissociated and therefore cannot reorient. Measurements of CTRs at the Pt (111) / electrolyte interface for several aqueous electrolytes are combined with CTRs measured in non-aqueous acetonitrile to explore the dependence of surface relaxation on adsorption. Fits to CTRs are also used to determine the double layer structure at aqueous Pt (111) / acetonitrile interfaces and how it varies with acetonitrile concentration. The results indicate that the acetonitrile adsorption increases with concentration and that the double layer region compresses.
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Krause, Lennard. "Assessment of Single Crystal X-ray Diffraction Data Quality." Doctoral thesis, Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2017. http://hdl.handle.net/11858/00-1735-0000-0023-3DD4-A.
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Wu, Chang-Hong. "X-ray diffraction study of aged copper beryllium alloys." Diss., This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-10022008-063043/.
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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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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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Brooks-Bartlett, Jonathan C. "Quantifying radiation damage in X-ray diffraction experiments in structural biology." Thesis, University of Oxford, 2016. https://ora.ox.ac.uk/objects/uuid:2f311eea-82bc-4200-846c-068ae26599ea.
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Quantitative studies of global radiation damage are presented for two different types of experiments in structural biology: macromolecular crystallography (MX) and small angle X-ray scattering (SAXS) MX is the most common technique to elucidate the atomic resolution structures of biological macromolecules. However, these molecules undergo radiation induced changes during the experiment that undesirably affect the data. Global radiation damage, which is characterised by an overall loss in the diffracted intensity of Bragg reflections, limits the amount of useful data that can be collected from a single crystal in an experiment. Furthermore, for experimental phasing experiments, the radiation induced intensity changes can be so significant that the phasing signal becomes undetectable, thereby hindering successful structure determination. This thesis investigates methods to track and correct the diffraction data that are affected as a result of global radiation damage. First, extensions to the diffraction weighted dose (DWD) metric are investigated for the ability of DWD to track the overall intensity decay of reflections. This metric then is combined with a new mathematical model of intensity decay to perform zero-dose extrapolation. An additional probabilistic extrapolation approach is incorporated into the traditional regression based approach to allow extrapolation of low multiplicity reflections. As an alternative approach, a new hidden Markov model representation of the data collection experiment is developed that allows the time-resolved calculation of structure factor amplitudes, with error estimates calculated explicitly. This method gives comparable refinement statistics to that obtained from data processed with the current data reduction pipeline, and improvements to the algorithm are proposed. SAXS, on the other hand, is a complementary structural technique that results in low resolution information about macromolecules. However it still requires the probing of the macromolecules with ionising radiation, so radiation induced changes are still a problem. Unfortunately the tools for assessing radiation damage in SAXS experiments are not mature enough for them to be used routinely. This thesis presents extensions to RADDOSE-3D to perform dose calculations for SAXS samples. Additionally, a free, open source Python library has been developed to allow the exploration and visualisation of the results of a similarity analysis of frames within a dataset. These tools are then used to determine the efficacy of various radioprotectant compounds at different concentrations to mitigate radiation damage effects.