Ion selectivity of minerals has traditionally been utilized in industry as a catalyst, metal separation, and environmental reclamation/sequestration tool. There is an increased interest in understanding ion selectivity mechanisms of micro-porous minerals and mineral-like structures and how they can be applied in various industries: environmental and, potentially, pharmaceutical. This study seeks to understand the ion exchange mechanisms in micro-porous zirconosilicates using time-resolved Raman spectroscopy and X-ray diffraction. The thesis material was exchanged with H+, Na+, K+, and Cs+ in order to better understand structural changes as well as the influence of the H+-bonding during the exchange process. It is hypothesized that the host (H+) ion strongly influences the ion selectivity of the mineral by changing framework polyhedra and ring geometry, and the geometry of the interstitial the OH…H2O bond network to only allow cations of certain sizes through the channels. In addition, the H+ may repel cations with high charge densities from entering the extra-framework sites in the crystal structure by protonating the channel pathways.

Ultra-violet and visible light induced processes in small organic molecules play very important roles in many fields, e.g., environmental sciences, biology, material development, chemistry, astrophysics and many others. Thus it is of great importance to better understand the mechanisms behind these processes. To achieve this, a bottom-up approach is most effective, where the photo-induced dynamics occurring in the simplest organic molecule (ethylene) are used as a starting point. Simple substituents and functional groups are added in a controlled manner to ethylene, and changes in the dynamics are investigated as a function of these modifications. In this manner, the dynamics occurring in more complex systems can be explored from a known base. In this thesis, the excited state dynamics of small organic molecules are studied by a combination of time-resolved photoelectron spectroscopy and various computational methods in order to determine the basic rules necessary to help understand and predict the dynamics of photo-induced processes. The dynamics occurring in ethylene involve a double bond torsion on the ππ* excited state, followed by the decay to the ground state coupled with pyramidalization and hydrogen migration. Several different routes of chemical modification are used as the basis to probe these dynamics as the molecular complexity is increased. (i) When ethylene is modified by the addition of an alkoxyl group (-OCnH2n+1), a new bond cleavage reaction is observed on the πσ* state. When modified by a cyano (-CN) group, a significant change in the carbon atom involved in pyramidalization is observed. (ii) When ethylene used to build up small cyclic polyenes, it is observed that the motifs of the ethylene dynamics persist, expressed as ring puckering and ring opening. (iii) In small heteroaromatic systems, i.e., an aromatic ring containing an ethylene-like sub-structure and one or two non-carbon atoms, the type of heteroatom (N: pyrrole, pyrazole O: furan) gives rise to different bond cleavage and ring puckering channels. Furthermore, adding an aldehyde group (-C=O) onto furan, as a way to lengthen the delocalised ring electron system, opens up additional reaction channels via a nπ* state. The results presented here are used to build up a more complete picture of the dynamics that occur in small molecular systems after they are excited by a visible or UV photon, and are used as a basis to motivate further investigations. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 5: Manuscript. Paper 6: Manuscript.</p>

We present a time-resolved Kerr microscope, capable of measuring the magnetization dynamics of samples grown on transparent, double-side-polished substrates.The magnetization is excited by a current pulse, using a coplanar waveguide placed beneath the samples. The Kerr rotation is detected with the stroboscopic pump-probe technique, using a probing laser, synchronized with the current pulse.We report benchmark measurements of the time-resolved Kerr instrument for magnetization dynamics in thin permalloy and FePd films. The experimental results for ferromagnetic resonance peaks have been compared with the values predicted by Kittel. / Vi presenterar ett tidsupplöst Kerr-mikroskop, kapabel till att mäta magnetiseringsdynamiken hos magnetiska prov tillverkade på transparenta, dubbelsdigt polerade substrat. Magnetiseringen exiteras med en strömpuls via en koplanär vågguide placerad under provet. Kerr-rotationen detekteras med hjälp av en stroboskopisk ”pump-probe” teknik som använder en ”probing” laser synchroniserad med strömpulsen. Vi rapporterar prestandatest av det tidsupplösta kerr-instrumentet för magnetiseringsdynamiken i tunna permalloy - och FePd - filmer. De experimentella resultaten för de ferromagnetiska resonans-peakarna har jämförts med beräknade värden från Kittel.

Live-cell imaging with fluorescent protein-based sensors allows us to monitor many dynamic changes in situ. The first genetic manipulation of green fluorescent protein to increase brightness initiated a boom, with a myriad of fluorescent protein sensors now available that span the UV, visible and near-IR range; capable of detecting a great number of metabolites, ions, and other biological signaling components with increased spatial and temporal precision. Used for both steady-state and time-resolved approaches, fluorescent proteins can be used in a wide variety of quantitative approaches. Steady-state sensors are typically characterized as intensiometric or ratiometric; and intensiometric sensors are characterized by an increase or decrease in emission intensity in response to analyte. However, moving in vivo, concentration and intensity dependence of the fluorophore, sample thickness, and photobleaching are limiting factors. Ratiometric probes respond by an inverse change in excitation or emission profiles in response to analyte, normalizing for bleaching or protein expression effects. As an intrinsic property of fluorophores, fluorescence lifetime does not rely on protein concentration, method of measurement or fluorescence intensity. By monitoring changes in lifetime using fluorescence lifetime spectroscopy, no special ratiometric fluorophores are needed, opening up a wider selection of potential fluorescent sensors. Lifetime and other time-resolved approaches are becoming more and more popular due to ease of quantitation and increased signal to background. Here we present the in vitro and live-cell characterization of genetically encoded, ratiometric and lifetime optimized red fluorescent protein pH sensors, a methodology for quantifying receptor trafficking in real time, as well as a lanthanide time resolved imaging approach.

Photocrystallography is a relatively new and continuously developing technique used in the structure determination of metastable and transient species in the crystalline state. This thesis contains a description of investigations into photo-induced linkage isomerism reactions in the solid state with the use of single crystal and powder X-ray diffraction experiments to monitor structural changes at low temperature.

Time resolved imaging is concerned with the measurement of photon arrival time. It has a wealth of emerging applications including biomedical uses such as fluorescence lifetime microscopy and positron emission tomography, as well as laser ranging and imaging in three dimensions. The impact of time resolved imaging on human life is significant: it can be used to identify cancerous cells in-vivo, how well new drugs may perform, or to guide a robot around a factory or hospital. Two essential building blocks of a time resolved imaging system are a photon detector capable of sensing single photons, and fast time resolvers that can measure the time of flight of light to picosecond resolution. In order to address these emerging applications, miniaturised, single-chip, integrated arrays of photon detectors and time resolvers must be developed with state of the art performance and low cost. The goal of this research is therefore the design, layout and verification of arrays of low noise Single Photon Avalanche Diodes (SPADs) together with high resolution Time-Digital Converters (TDCs) using an advanced silicon fabrication process. The research reported in this Thesis was carried out as part of the E.U. funded Megaframe FP6 Project. A 32x32 pixel, one million frames per second, time correlated imaging device has been designed, simulated and fabricated using a 130nm CMOS Imaging process from ST Microelectronics. The imager array has been implemented together with required support cells in order to transmit data off chip at high speed as well as providing a means of device control, test and calibration. The fabricated imaging device successfully demonstrates the research objectives. The Thesis presents details of design, simulation and characterisation results of the elements of the Megaframe device which were the author’s own work. Highlights of the results include the smallest and lowest noise SPAD devices yet published for this class of fabrication process and an imaging array capable of recording single photon arrivals every microsecond, with a minimum time resolution of fifty picoseconds and single bit linearity.

Ultrafast carrier dynamics studies have been carried out on samples with single layers of self-assembled In0.4Ga0.6As/GaAs quantum dots (QDs). Measurements were made using femtosecond degenerate pump-probe differential reflectivity with an 800-nm, 28-fs Ti-sapphire oscillator as the source. The QDs were grown via modified Stranski-Krastanov growth. This modified growth process consists of two steps: low-temperature growth and high-temperature annealing. Specifically, the InGaAs QD structures are fabricated on n-type GaAs(001) using molecular beam epitaxy. The InGaAs layer is deposited at 350-3700C followed by QD self assembly at 420-4900C. Finally, these QDs are capped with 10 nm or 100 nm of GaAs. The measured width and height of these QDs are typically 25 nm and 8 nm, respectively. Dots annealed at higher temperature have larger base area (width and length) and reduced height, as compared to those annealed at lower temperature. We have used a model consisting of a linear combination of an exponential decaying function to describe the carrier dynamics and fit the reflectivity data, revealing trends in the carrier capture and relaxation times associated with the InGaAs layer versus laser excitation level and QD morphology. Capture times are ~ 1 ps for the 100-nm capped samples, but slightly shorter for the 10-nm capped thin samples, indicating carrier transport plays a role in dynamics. The carrier dynamics in 10-nm capped samples are correlated with sample annealing temperature, indicating QD morphology affects carrier capture. Versus laser intensity, and thus carrier excitation level, the dynamics generally become slower, suggesting state filling is important in both the capture and relaxation of excited carriers in these samples.

<p>Neutron stimulated emission computed tomography (NSECT) is a non-invasive, tomographic imaging technique with the ability to locate and quantify elemental concentration in a tissue sample. Previous studies have shown that NSECT has the ability to differentiate between benign and malignant tissue and diagnose liver iron overload while using a neutron beam tomographic acquisition protocol followed by iterative image reconstruction. These studies have shown that moderate concentrations of iron can be detected in the liver with moderate dose levels and long scan times. However, a low-dose, reduced scan time technique to differentiate various liver diseases has not been tested. As with other imaging modalities, the performance of NSECT in detecting different diseases while reducing dose and scan time will depend on the acquisition techniques and parameters that are used to scan the patients. In order to optimize a clinical liver imaging system based on NSECT, it is important to implement low-dose techniques and evaluate their feasibility, sensitivity, specificity and accuracy by analyzing the generated liver images from a patient population. This research work proposes to use Monte-Carlo simulations to optimize a clinical NSECT system for detection, localization, quantification and classification of liver diseases. This project has been divided into three parts; (a) implement two novel acquisition techniques for dose reduction, (b) modify MLEM iterative image reconstruction algorithm to incorporate the new acquisition techniques and (c) evaluate the performance of this combined technique on a simulated patient population. </p><p>The two dose-reduction, acquisition techniques that have been implemented are; (i) use of a single angle scanning, multi-detector acquisition system and (ii) the neutron-time resolved imaging (n-TRI) technique. In n-TRI, the NSECT signal has been resolved in time by a function of the speed of the incident neutron beam and this information has been used to locate the liver lesions in the tissue. These changes in the acquisition system have been incorporated and used to modify MLEM iterative image reconstruction algorithm to generate liver images. The liver images are generated from sinograms acquired by the simulated n-TRI based NSECT scanner from a simulated patient population.</p><p>The simulated patient population has patients of different sizes, with different liver diseases, multiple lesions with different sizes and locations in the liver. The NSECT images generated from this population have been used to validate the liver imaging system developed in this project. Statistical tests such as ROC and student t-tests have been used to evaluate this system. The overall improvement in dose and scan time as compared to the NSECT tomographic system have been calculated to verify the improvement in the imaging system. The patient dose was calculated by measuring the energy deposited by the neutron beam in the liver and surrounding body tissue. The scan time was calculated by measuring the time required by a neutron source to produce the neutron fluence required to generate a clinically viable NSECT image.</p><p>Simulation studies indicate that this NSECT system can detect, locate, quantify and classify liver lesions in different sized patients. The n-TRI imaging technique can detect lesions with wet iron concentration of 0.5 mg/g or higher in liver tissue in patients with 30 cm torso and can quantify lesions at 0.3 ns timing resolution with errors &#8804; 17.8%. The NSECT system can localize and classify liver lesions of hemochromatosis, hepatocellular carcinoma, fatty liver tissue and cirrhotic liver tissue based on bulk and trace element concentrations. In a small patient with a torso major axis of 30 cm, the n-TRI based liver imaging technique can localize 91.67% of all lesions and classify lesions with an accuracy of 88.23%. The dose to the small patient is 0.37 mSv a reduction of 39.9% as compared to the NSECT tomographic system and scan times are comparable to that of an abdominal MRI scan. In a bigger patient with a torso major axis of 50cm, the n-TRI based technique can detect 75% of the lesions, while localizing 66.67% of the lesions, the accuracy of classification is 76.47%. The effective dose equivalent delivered to the larger patient is 1.57 mSv for a 68.8% decrease in dose as compared to a tomographic NSECT system.</p><p>The research performed for this dissertation has two important outcomes. First, it demonstrates that NSECT has the clinical potential for detection, localization and classification of liver diseases in patients. Second, it provides a validation of the simulation of a novel low-dose liver imaging technique which can be used to guide future development and experimental implementation of the technique.</p> / Dissertation

Femtosecond time-resolved photoelectron spectroscopy (fsTRPES) experiments have been used to study the photoelectron energy spectra of simple molecules since the 1980’s. Analysis of these spectra provides information about the ultrafast internal conversion dynamics of the parent ions. However, ultraviolet pulses must be used for these pump-probe experiments in order to ionize the molecules. Since current solid state lasers, such as the Ti:sapphire laser, typically produce pulses centered at 800nm, it is necessary to generate UV pulses with nonlinear frequency mixing techniques. I therefore constructed an optical setup to generate the 3rd and 4th harmonics, at 266.7nm and 200nm, respectively, of a Ti:sapphire (Ti:sa) chirped-pulse amplified (CPA) laser system that produces 35fs pulses centered at 800nm. Thin Beta-Barium Borate (β-BaB2O4 or BBO) crystals were chosen to achieve a compromise between short pulse durations and reasonable conversion efficiencies, since ultrashort pulses are quite susceptible to broadening from group velocity dispersion (GVD). Output energies of around 11μJ and 230nJ were measured for the 266.7nm and 200nm pulses, respectively. The transform limits of the 3rd and 4th harmonic pulse lengths were calculated from their measured spectral widths. We found that the 266.7nm bandwidth was large enough to support sub-30fs pulses, and due to cutting at the lower-wavelength end of the 200nm spectrum, we calculated an upper limit of 38fs. The pulses were compressed with pairs of CaF2 prisms to compensate for dispersion introduced by transmissive optics. Two-photon absorption (TPA) intensity autocorrelations revealed fully compressed pulse lengths of 36 ± 2 fs and 42 ± 4 fs for the 3rd and 4th harmonics, respectively.

Femtosecond time-resolved photoelectron spectroscopy (fsTRPES) experiments have been used to study the photoelectron energy spectra of simple molecules since the 1980’s. Analysis of these spectra provides information about the ultrafast internal conversion dynamics of the parent ions. However, ultraviolet pulses must be used for these pump-probe experiments in order to ionize the molecules. Since current solid state lasers, such as the Ti:sapphire laser, typically produce pulses centered at 800nm, it is necessary to generate UV pulses with nonlinear frequency mixing techniques. I therefore constructed an optical setup to generate the 3rd and 4th harmonics, at 266.7nm and 200nm, respectively, of a Ti:sapphire (Ti:sa) chirped-pulse amplified (CPA) laser system that produces 35fs pulses centered at 800nm. Thin Beta-Barium Borate (β-BaB2O4 or BBO) crystals were chosen to achieve a compromise between short pulse durations and reasonable conversion efficiencies, since ultrashort pulses are quite susceptible to broadening from group velocity dispersion (GVD). Output energies of around 11μJ and 230nJ were measured for the 266.7nm and 200nm pulses, respectively. The transform limits of the 3rd and 4th harmonic pulse lengths were calculated from their measured spectral widths. We found that the 266.7nm bandwidth was large enough to support sub-30fs pulses, and due to cutting at the lower-wavelength end of the 200nm spectrum, we calculated an upper limit of 38fs. The pulses were compressed with pairs of CaF2 prisms to compensate for dispersion introduced by transmissive optics. Two-photon absorption (TPA) intensity autocorrelations revealed fully compressed pulse lengths of 36 ± 2 fs and 42 ± 4 fs for the 3rd and 4th harmonics, respectively.