No description available.

<p>Multiphase flows, such as liquid/gas and solid/gas, dominate many different areas of life, including the medical, agricultural, propulsion, and chemical industries. Gaining insight into the dynamic processes that drive these multiphase flows can therefore have far-reaching impact in many sectors of scientific research. Of key interest is the non-invasive tracking of important state properties such as the mass and temperature distributions in high optical depth multiphase flows. To accomplish this, X-ray diagnostic approaches are utilized due to their ability to probe complex phenomena without being hampered by multiple scattering that arise from complex interactions at the flow surface boundaries.</p> <p>This work accomplishes the measurement of mass distribution through time-resolved tomographic reconstructions of the liquid mass distributions in fuel sprays within liquid/gas flows. The developed diagnostic tool shown here uses a novel multiple line of sight tube source tomography setup to obtain simultaneous time-resolved two-dimensional radiographs of different spray geometries at various perspectives. Through tomographic reconstruction, these radiographs are converted into volumetric reconstructions to give a true sense of mass distribution—where exactly is the liquid mass located in the <em>x</em>, <em>y</em>, <em>z</em> spatial extents at a specific moment in time <em>t</em>? This technique is first showcased in a simple spray as a feasibility test and later applied to a more complex spray geometry and compared against other state-of- the-art diagnostics for a full quantitative understanding of the developed technique. Outside of tomography, improvements in decreasing the uncertainties in line of sight averaged mass distribution measurements in radiography imaging experiments are also showcased through source characterization efforts both for tube source and synchrotron source experiments.</p> <p>Efforts in ascertaining the temperature distributions in liquid/gas flows is done through an application of wide angle X-ray scattering, a technique that is commonly used in the materials, chemistry, and biology sciences but has yet to be widely used in the propul- sion community. These newly developed X-ray scattering measurements are accomplished through the use of a focused monochromatic beam available at the Advanced Photon Source synchrotron facility, and is applied first in calibration jets and later towards more complex dynamic sprays and multi-species liquid solutions.</p>

Metastable austenitic and duplex stainless steels are widely used materials in industrial anddomestic applications, owing to their attractive characteristics such as good corrosion resistanceand favorable mechanical properties. Both types of steel experience enhanced mechanicalproperties during plastic deformation due to the formation of the martensite phase from theparent austenite phase, this is called deformation-induced martensitic transformation (DIMT).It is therefore of technical interest to study the transformation mechanism and its impact onmechanical properties for a better understanding and ultimately for developing new materialswith improved performance in certain applications. In the present thesis, two austenitic stainless steels (201Cu, HyTens® 301) and two duplexstainless steels (FDX25®, FDX27®) were investigated. Samples were tensile tested during insitusynchrotron radiation experiments performed at the Cornell High Energy SynchrotronSource (CHESS), Ithaca, USA. Tests were performed at both room temperature and at elevatedtemperatures. The collected diffraction data were then processed by software such as Fit2D andMATLAB. Quantitative phase fraction analysis based on the direct comparison method wasperformed successfully. Microstructural analysis of samples before deformation and after thefull tensile testing was also performed using electron microscopy. The deformation induced martensitic transformation took place in HyTens 301, FDX25 andFDX27, but in 201Cu the austenite was stable during the tensile tests conducted here. The a’-martensite formed in a significantly higher fraction than the ε-martensite in all alloys. At roomtemperature, the critical stress levels for martensitic transformation were 490 MPa, 700 MPaand 700MPa for HyTens 301, FDX25 and FDX27, respectively.

Die vorliegende Arbeit behandelt die radiometrische Nutzung von Wellenlängenschiebern an Elektronenspeicherringen. Die grundsätzlichen Aspekte der Radiometrie, der technischen Voraussetzungen und des Einflusses von Wellenlängenschiebern auf den Speicherring werden am Beispiel eines bei BESSY installierten Gerätes aufgezeigt. Ein Großteil der Rechnungen wurden mit dem Programm WAVE durchgeführt, das im Rahmen der Arbeit entwickelt wurde. WAVE erlaubt die Berechnung der Synchrotronstrahlung von Wellenlängenschiebern mit einer relativen Unsicherheit von 1/100000. Maschinenphysikalische Eigenschaften eines Wellenlängenschiebers und eine Erzeugenden-Funktion für symplektische Tracking-Rechnungen können ebenfalls mit WAVE berechnet werden. Letztere wurden in den Tracking-Code BETA implementiert. Damit lassen sich die Einflüsse von Insertion Devices auf die dynamische Apertur und die Emittanz des Speicherringes untersuchen. Die Ergebnisse dieser Studien führten zum Konzept alternierender High- und Low-Beta-Sektionen, die den Betrieb supraleitender Insertion Devices bei BESSY-II ohne signifikante Störung der Speicherringoptik ermöglichen. Um auch die experimentelle Seite der Radiometrie an Wellenlängenschiebern zu untersuchen, wurde ein Programm auf der Basis des Monte-Carlo-Codes GEANT4 entwickelt. Es erlaubt die Simulation der radiometrischen Messung und der Absorptionseigenschaften des Detektors. Mit den entwickelten Programmen wurden erste radiometrische Messungen der PTB analysiert. Ein Vergleich zwischen Messungen und Rechnung zeigt eine zufriedenstellende Übereinstimmung mit Abweichungen von ca. fünf Prozent für Messungen im Energiebereich zwischen 40 keV und 120 keV hinter einem 1-mm-Kupferfilter. Eine bessere Übereinstimmung wurde im Bereich von 20 - 80 keV ohne Kupferfilter erzielt. In diesem Fall stimmen die gemessenen Daten im Rahmen der systematischen Unsicherheiten von zwei Prozent mit den Rechnungen überein. / Subject of this thesis are the operation of wave-length shifters at electron storage rings and their use in radiometry. The basic aspects of the radiometry, the technical requirements, the influence of wave-length shifters on the storage ring, and results of first measurements are presented for a device installed at BESSY. Most of the calculations are carried out by the program WAVE, which has been developed within this thesis. WAVE allows to calculate the synchrotron radiation spectra of wave-length shifters within an relative uncertainty of 1/100000. The properties of wave-length shifters in terms of accelerator physics as well as a generating function for symplectic tracking calculations can also be calculated by WAVE. The later was implemented in the tracking code BETA to investigate the influence of insertion devices on the dynamic aperture and emittance of the storage ring. These studies led to the concept of alternating low- and high-beta-sections at BESSY-II, which allow to operate superconducting insertion devices without a significant distortion of the magnetic optics. To investigate the experimentel aspects of the radiometry at wave-length shifters, a program based on the Monte-Carlo-code GEANT4 has been developed. It allows to simulate the radiometrical measurements and the absorption properties of detektors. With the developed codes first radiometrical measurements by the PTB have been analysed. A comparision of measurements and calculations show a reasonable agreement with deviations of about five percent in the spectral range of 40 - 60 keV behind a 1-mm-Cu filter. A better agreement was found between 20 keV and 80 keV without Cu filter. In this case the measured data agreed within a systematic uncertainty of two percent with the results of the calculations.

Inhalt dieser Arbeit ist die Design-Studie für einen kompakten Niederenergie-Elektronenspeicherring für die Radiometrie. Im Ring sollen Elektronen mit Energien im Bereich von 200 MeV bis 600 MeV gespeichert werden können, wobei die Emittanz möglichst klein und die Strahllebensdauer über den gesamten Energiebereich bei einem Strom von 100 mA mindestens eine Stunde sein sollten.Diese Vorgaben wurden in Abstimmung mit einem der potentiellen Hauptnutzer, der Physikalisch-Technische Bundesanstalt (PTB), festgelegt und sollen den Speicherring zu einer optimalen Synchrotronstrahlungsquelle für die Radiometrie im ultravioletten und vakuumultravioletten Spektralbereich mit Photonenenergien zwischen etwa 5 eV und 200 eV machen. Im Rahmen dieser Arbeit werden die aus physikalischer Sicht wichtigsten Teilsysteme eines Speicherringes konzeptioniert: Magnetoptik, Hochfrequenz-, Vakuum-, Diagnose- und Injektionssystem sowie die Magnetauslegung. Außerdem werden die zu erwartenden Synchrotronstrahlungsspektren berechnet. Der entworfene Speicherring hat einen Umfang von 34.2 m und besteht aus zwei "Triple Bend Achromat"-Bögen, die durch gerade Strecken miteinander verbunden sind. In eine dieser geraden Strecken kann ein maximal 5.6 m langes "Insertion Device" eingebaut werden, die andere ist durch die Injektionselemente und das Hochfrequenz-Cavity belegt. Insgesamt können mit dem Design des hier vorgestellten Speicherringes alle gestellten Anforderungen erfüllt werden: die natürliche Emittanz ist vergleichsweise niedrig und liegt bei günstigen linearen und nichtlinearen Eigenschaften der Magnetoptik nah an ihrem minimal möglichen Wert. Mit der gewählten Auslegung von Magnetoptik, Hochfrequenz- und Vakuumsystem beträgt die Strahllebensdauer mit einem Speicherringstrom von 100 mA bei niedrigen Elektronenenergien zwischen (200...300)MeV etwas über eine Stunde und steigt auf mehr als sechs Stunden bei der Maximalenergie von 600 MeV. Die Strahllebensdauer übertrifft damit im gesamten Energiebereich die Vorgabe. / The subject of this work is the preparation of a design study for a compact low energy electron storage ring for radiometry in the ultraviolet and vacuum ultraviolet spectral range. Electrons with energies between 200 MeV and 600 MeV are to be stored. A small natural emittance is desired and the lifetime of a stored electron beam of 100 mA should not be less than one hour in the considered energy range. These major guidelines have been fixed in cooperation with one of the potential main users, the Physikalisch Technische Bundesanstalt (PTB), to optimize the storage ring for radiometric applications in the ultraviolet and vacuum ultraviolet spectral range with photon energies from approximately 5 eV to 200 eV. In this work the physical layout for the most important subsystems is given: magnet optics, rf-, vacuum-, diagnostic and injection system as well as the main magnet design. Additionally the expected synchrotron radiation spectra are calculated. The storage ring has a circumference of 34.2 m and consists of two Triple Bend Achromat cells, connected by two long straight sections. In one of these straight sections a 5.6 m long insertion device can be build in. The other one is occupied by the injection elements and the rf-cavity. All aspired guidelines are feasible with the presented storage ring design: the natural emittance is comparably small and with good linear and nonlinear optical properties close to its minimum value. With the presented solution (magnet optics, rf- and vacuum-system) the electron beam lifetime with 100 mA ring current is slightly above one hour at energies between (200...300) MeV and increases to more than 6 hours at the maximum energy of 600 MeV. Thus beam lifetime exceeds the guidelines at all energies.

Gesunder humaner Knochen unterliegt einem permanenten Umbau, um sich den mechanischen Anforderungen anzupassen, Mikrofrakturen zu reparieren und das Mineraliengleichgewicht zu erhalten. Dieser Umbauprozess wird durch Osteoblasten- und Osteoklastenaktivität realisiert, den knochenbildenden bzw. knochenresorbierenden Zellen. Gesteuert wird dieser Prozess durch Osteozyten, dessen Netzwerk mechanosensorische Fähigkeiten zugesprochen werden. Bisphosphonate (BP), hemmen die Osteoklastenaktivität und erhöhen somit die Knochenumsatzzeit. Im ersten Teil dieser Arbeit wurden morphologische Eigenschaften der Osteozyten-Lakunen (OL) in humanem Knochen mittels Synchrotron-µCT untersucht. Dabei wurden sowohl gesunde als auch mit BP behandelte Spender verglichen. Anschließend haben wir Synchrotron-Nano-CT in Kombination mit Phasenkontrast angewandt, um unsere Untersuchungen auf die Morphologie des lakuno-kanalikulären Netzwerkes (LKN) und die Gewebeeigenschaften in der Umgebung des LKN auszuweiten. Wir nahmen an, dass der sekundäre Mineralisierungsprozess mittels eines Diffusionsprozesses durch die Grenzfläche der extrazellulären Flüssigkeit im LKN stattfindet, was zu Gradienten der Massendichte in der Umgebung des LKN führen sollte. Unsere Untersuchungen haben gezeigt, dass sowohl in der Umgebung der OL als auch der Kanäle Massendichtegradienten existieren. Daraus schließen wir, dass der Mineralienaustausch zwischen der extrazellulären Flüssigkeit und der mineralisierten Matrix an der gesamten Oberfläche des LKN stattfindet. Wir schätzten, dass die Kapazität, unter Berücksichtigung des gesamten LKN, Mineralien auszutauschen etwa eine Größenordnung höher ist, gegenüber der Annahme, dass der Austausch lediglich an den Grenzflächen der OL stattfindet. Zukünftige Studien sollten nicht nur die peri-LKN Gewebeeigenschaften während der sekundären Mineralisierung untersuchen, sondern auch Schwankungen der Mineralienkonzentration bei hohen Kalziumanforderungen des Körpers berücksichtigen. / Under healthy conditions human bone undergoes permanent remodeling to adjust to mechanical demands, to repair micro-cracks and to maintain mineral homeostasis. This process of remodeling is performed by osteoblasts and osteoclasts: bone-forming and bone-resorbing cells. The activity of osteoclasts and osteoblasts is triggered by osteocytes, the most frequently occurring type of bone cell, via mechanosensation processes. Bisphosphonates (BP) prescribed during treatment for osteoporosis or bone metastasis inhibit osteoclast activity and thus decrease the bone turnover. In this work, the distribution and morphology of osteocyte lacunae of human cortical jaw bone was investigated in 3D, and a comparison between healthy and BP-treated donors was performed using synchrotron radiation (SR) µCT. In a second approach, we used SR nano-CT with phase contrast to investigate the morphology of the canalicular network and the bone tissue properties in the vicinity of the lacuna-canalicular network of human jaw bone, originating from both healthy subjects and patients treated with BPs. We hypothesized that secondary mineralization takes place via a diffusion process through the fluid-matrix interface at both the lacunar and the canalicular surfaces. This should result in mass density gradients with respect to the distance to the pore boundary. Such mass density gradients were indeed observed at both lacunar and canalicular interfaces. We concluded that mineral exchange between extracellular fluid and mineralized matrix occurs at all bone surfaces, including the canaliculi. Our data suggested that the capacity of the pore network to exchange mineral with the bone matrix would increase by one order of magnitude if the canalicular surface is taken into account. However, more studies should be performed, targeting not only the changes of tissue properties during secondary mineralization, but also during fluctuations of mineral concentration in periods of high mineral demand.

Das Ziel dieser Dissertation ist das Schließen der radiometrischen Lücke zwischen der klassischen Radiometrie und der Radiometrie im Bereich weniger und einzelner Photonen. In dieser Arbeit wurden dazu zwei wesentliche Themen bearbeitet. Erstens, die Charakterisierung und Validierung eines neuen radiometrischen Detektorprimärnormals für den Wellenlängenbereich von 400 nm bis 800 nm basierend auf Silizium-Photodioden. Dieses neuartige Primärnormal kann sowohl in der Radiometrie im Bereich weniger Photonen als auch in der klassischen Radiometrie eingesetzt werden, der sogenannte “Predictable Quantum Efficient Detector” (PQED). Der PQED wurde im Rahmen dieser Arbeit charakterisiert und experimentell validiert. Für die Validierung war es nötig, die relativen Unsicherheiten der klassischen Radiometrie und insbesondere der Kryoradiometrie, deutlich zu verringern. Mit der Inbetriebnahme eines neuen Kryoradiometers wurde das Ziel, in den Unsicherheitsbereich von ca. 10E−5 vorzudringen, erreicht. Zweitens, es wurde eine Kalibriermethode für Einzelphotonendetektoren eingesetzt, rückgeführt auf das internationale Einheitensystem, die auf den einzigartigen Eigenschaften von Synchrotronstrahlung basiert. Diese Methode kann benutzt werden um sowohl Freistrahl- als auch fasergekoppelte Einzelphotonendetektoren bei praktisch jeder gewünschten Wellenlänge zu kalibrieren und erreicht im Moment die weltweit geringsten Messunsicherheiten. Mit dem neuen Kryoradiometer, dem PQED und dem auf Synchrotronstrahlung basierenden Kalibrierverfahren sind die erreichbaren Messunsicherheiten in der Radiometrie im Bereich von wenigen Photonen bis zu Strahlungsleistungen im Milliwattbereich deutlich reduziert worden. / This thesis addresses the bridging of the radiometric gap in the transition from classical radiometry to the few and single photon radiometry. In this context, two main tasks were emphasised. First: A new radiometric primary detector standard for wavelengths between 400 nm and 800 nm, suitable for classical and few photon radiometry, the so-called “Predictable Quantum Efficient Detector” (PQED) was characterised and validated. For the validation of the PQED, the relative uncertainties achievable in classical radiometry and, in particular, with cryogenic radiometers had to be reduced to a level of 10E−5 with the commissioning of a new cryogenic radiometer facility. Second: A calibration method for single photon detectors in the visible and NIR has been used which is based on the unique properties of synchrotron radiation. This calibration method allows radiometric single photon detector calibrations with the lowest uncertainties reported so far. This method can be used to calibrate free space and fibre-coupled single photon detectors traceable to the international system of units at practically every desired optical wavelength. With the new cryogenic radiometer, the PQED, and the calibration method based on synchrotron radiation, the uncertainties in radiometry have been significantly reduced in the range from milliwatts of radiant power down to attowatts corresponding to a few photons per second.

NiTi-based shape memory alloys (SMAs) offer a good combination of high-strength, ductility, corrosion resistance, and biocompatibility that has served them well and attracted the attention of many researchers and industries. The alloys unique thermo-mechanical ability to recover their initial shape after relatively large deformations by heating or upon unloading due to a characteristic reversible phase transformation makes them useful as damping devices, solid state actuators, couplings, etc. However, there is a need to increase the temperature of the characteristic phase transformation above 150 °C, especially in the aerospace industry where high temperatures are often seen. Prior researchers have shown that adding ternary elements (Pt, Pd, Au, Hf and Zr) to NiTi can increase transformation temperatures but most of these additions are extremely expensive, creating a need to produce cost-effective high temperature shape memory alloys (HTSMAs). Thus, the main objective of this research is to examine the relatively unstudied NiTiZr system for the ability to produce a cost effective and formable HTSMA. Transformation temperatures, precipitation paths, processability, and high-temperature oxidation are examined, specifically using high energy X-ray Diffraction (XRD) measurements, in NiTi-20 at.% Zr. This is followed by an in situ XRD study of the phase growth kinetics of the favorable H-phase nano precipitates, formed in NiTiHf and NiTiZr HTSMAs, based on prior thermo-mechanical processing in a commercial NiTi-15 at.% Hf HTSMA to examine the final processing methods and aging characteristics. Through this research, knowledge of the precipitation paths in NiTiZr and NiTiHf HTSMAs is extended and methods for characterization of phases and strains using high energy XRD are elucidated for future work in the field.

No description available.

Lanthanide-based nanoparticles are of interest for optical displays, catalysis, telecommunication, bio-imaging, magnetic resonance imaging, multimodal imaging, etc. These applications are possible partly because the preparation of lanthanide-based nanoparticles has made tremendous progress. Now, nanoparticles are routinely being made with a good control over size, crystal phase and even shape. Despite the achievements, little attention is given to the fundamental physical chemistry aspects, such as crystal structure, architecture, cation exchange, etc. The results of the study on the crystal structures of LnF3 nanoparticles show that the middle GdF3 and EuF3 nanoparticles have two crystal phases, which has then been tuned by doping with La3+ ions. However, the required doping level is very different from the bulk. While the results for the bulk are well explained by thermodynamic calculations, kinetics is actually responsible for the results of the undoped and doped GdF3 and EuF3 nanoparticles. The attempt to make LnF3 core-shell nanoparticles led to the finding of cation exchange, a phenomenon that upon exposure of LnF3 nanoparticles to an aqueous solution containing Ln3+ ions, the Ln3+ ions in the nanoparticles are replaced by the Ln3+ ions in the solution. The consequence of the cation exchange is that LnF3 core-shell nanoparticles are unlikely to form in aqueous media using a core-shell synthesis procedure. It has also been verified that nanoparticles synthesized using an alloy procedure do not always have an alloy structure. This means that the core-shell and alloy structure of nanoparticles in the literature may not be true. The investigation of the architecture of nanoparticles synthesized in aqueous media is extended to those synthesized in organic media. The dopant ion distribution in NaGdF4 nanoparticles has been examined. It has been found that they don’t have the generally assumed statistical dopant distribution. Instead, they have a gradient structure with one type of Ln3+ ions more concentrated towards the center and the other type more concentrated towards the surface of the nanoparticles. With the understanding of these physical insights, lanthanide-based core-shell nanoparticles are prepared using the cation exchange. These core-shell nanoparticles containing a photoluminscent core and a paramagnetic shell are promising candidates for multimodal imaging. / Graduate