Alginate is a popular biomaterial in tissue engineering. When crosslinked with calcium ions (Ca2+), alginate forms a hydrogel which provides necessary mechanical support as a scaffold. The material properties as well as the biological properties of alginate scaffold are of great importance. In this thesis, the aim is to use traditional methods, such as scanning electron microscopy (SEM) and light microscopy, and emerging X-ray imaging techniques, such as micro-computed tomography (micro-CT) and synchrotron radiation (SR) X-ray imaging, to characterize the alginate scaffolds. Firstly, the material properties of freeze-dried alginate scaffolds were evaluated using micro-CT, as it is a non-destructive and non-invasive imaging method, and can provide three-dimensional information. Alginate scaffolds made with different sodium alginate concentrations and frozen to different temperatures were scanned and analyzed in micro-CT. Results indicated that lower freezing temperature and higher sodium alginate concentration lead to smaller pore size and porosity. Secondly, cell culture experiments were carried out to study the biological properties and the interactions of alginate hydrogel with cells. A Schwann cell line was either blended with alginate solution before crosslinking with calcium chloride (CaCl2) or put around alginate gel in the culture dish. Light microscopy of sectioned slices showed that cells surrounding the alginate gel could not grow into the gel, while cells blended with alginate solution before crosslinking could proliferate inside the hydrogel. Cells grown inside a thin slice of alginate gels appeared to be in better condition and were larger in size and also grew in clusters. Thirdly, in order to image soft tissue buried inside alginate gels, such as brain slices, novel imaging methods based on synchrotron radiation (SR) were applied, such as absorption and phase contrast imaging, diffraction-enhanced imaging (DEI) and also combined with computed tomography (CT). Synchrotron-based monochromatic X-ray imaging proved to be good at distinguish objects of similar density, especially biological soft tissue samples, even without any staining material, such as osmium tetroxide (OsO4). These three pieces of research work show the potential in applying the emerging X-ray imaging in soft tissue engineering.

The second report from the Project-Group ESRF-Beamline of the Forschungszentrum Rossendorf covers the period from July 1999 until December 2000. The ROssendorf BeamLine (ROBL) at the European Synchrotron Radiation Facility (ESRF) in Grenoble, France performed quite well during this time. In the beamtime used by the FZR and collaborating institutes 44 scheduled experiments were performed, while in the ESRF scheduled beamtime 12 experiments. Additionally, a distinct amount of beamtime was devoted to in-house research of the FZR and methodical experiments. Since February 2000 ROBL is part of the European Commission's programme "Access to Research Infrastructure" which supports user groups from member and associated states of the EU during experiments at ROBL. In the year 2000 ROBL hosted 6 groups for experiments. The report is organised in three main parts. The first part contains extended contributions on results obtained at ROBL. The second part gives an overview about the scheduled experiments, publications, guests having visited ROBL with support of the EC, and some other information. Finally, the third part collects the experimental reports of the user groups received.

Current treatments for spinal cord injury (SCI) are extremely limited due to the fact that the central nervous system lacks the intrinsic ability to regenerate, and constitutes a poor environment for regenerative axon growth. Nerve tissue engineering is an emerging field with the aim of repairing or creating new nerve tissues to promote functional recovery by using artificial tissue repair scaffolds. The design of a stable and consistent animal model of SCI is essential to study the effectiveness of scaffolds in promoting nervous system repair. In this study, a partial transection animal model was created with a three dimensional lesion at T8-T9 that disrupts axonal pathways unilaterally in the dorsal columns of the rat spinal cord. Alginate hydrogel scaffolds incorporating living Schwann cells were fabricated to evaluate the abilities of those scaffolds to foster axonal regeneration. The surgical technique was improved to provide better outcomes related to bleeding during surgery, weight control, neurological function and surgery duration. The survival rate of animals during the surgical procedure and post-surgery period was ultimately increased to 100%. Histology and immunohistochemistry results indicated that implanted alginate scaffolds may induce larger cavities and extenuate harmful inflammation responses, but that effect was ameliorated by inclusion of Schwann cells in the scaffold. However, neither plain alginate scaffolds nor scaffolds containing living Schwann cells were able to improve regeneration of identified axon tracts in the spinal dorsal columns. This research also employed a synchrotron based x-ray phase contrast imaging technique coupled with computed-tomography to visualize the low optical density structural features of scaffolds and spinal cord tissues in formaldehyde fixed specimens. The imaging results suggest that this is a promising method for analyzing the structure of tissue repair scaffolds within the spinal cord. This degree of structural characterization, potentially applicable to living tissue, is not afforded by other conventional image analysis techniques.

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Macroscopic properties of rocks are functions of pore-scale geometry and can be determined from laboratory experiments using rock samples. Macroscopic properties can also be determined from computer simulations using 3D pore geometries derived from various imaging techniques. Using 3D imagery and computer simulations, we can calculate the porosity, permeability, formation resistivity factor and cementation exponent in reservoir drill cores. The objective of this thesis was to develop a workflow using Synchrotron X-ray Computed Microtomography (CMT) images and commercially available software in order to determine the macroscopic properties in reservoir drill cores for Midale Marly (M0) and Vuggy Shoal (V6) rocks. The workflow started by using CMT data that provided three-dimensional images of the reservoir rocks taken from drill cores in the Weyburn oil field. The resulting CMT grey scale images were used to isolate the pore space in the rock image. A three-dimensional mesh, representing the pore space, was then used to obtain the solution of the Navier-Stokes equations for an incompressible fluid and Laplace's equation for electrical current flow. Solutions of the Navier-Stokes equations were computed with different inlet pressures for the same pore geometry in order to confirm a direct proportionality between the mass fluid flux and pressure gradient as Darcy’s Law specifies. Previously measured laboratory transport properties were compared with my calculated transport properties on a smaller sub-volume of the same rock core imaged using 0.78 µm resolution CMT images. For the Midale Marly rock, the calculated permeability ranged from 0.01 to 3.53 mD. The formation resistivity factor ranged from 29.3 to 309.43 and the cementation exponent ranged from 1.99 to 2.10. The sample was verified to be nearly isotropic as the permeability was similar for three orthogonal fluid flow directions. Even though the sub-volume analyzed was smaller than a Representative Elementary Volume (REV), the results are within an order of magnitude of the previously calculated laboratory results as completed by Glemser (2007) and fall on the same power law trend. A Vuggy (V6) sample was investigated after the sample had been exposed to CO2, and dissolution within the rock matrix resulted in large visible pore spaces. Using 7.45 µm resolution CMT images, the permeability for a large isolated pore could not be calculated using the previous workflow due to computer memory limitations. Resampling enabled the data to fit into the available computer memory. The permeability values ranged from 2.66x10^5 to 8.59x10^5 mD for resampling the CMT images from 2x to 10x.

One of the main risks that exposed and unvegetated tailings pose to the environment and human health is airborne dust that may be inhaled or ingested. In the case of Pb-bearing dust, both particle size and the identity of the Pb-hosting minerals affect the degree of risk. Finer dusts (<5µm diameter) have a higher potential of being ingested deeper into the human lung causing possible tissue damage and toxic effects. We have collected size-fractionated airborne dust and near-surface pH-neutral tailings at New Calumet Mine, Quebec, Canada, a former Pb-Zn mine. Bioaccessibility describes how much of a substance can be dissolved by body fluids and become available for absorption by the body. The most bioaccessible Pb compounds are PbCO3 (cerussite), Pb3(CO3)2(OH)2 (hydrocerussite) and PbO, followed by PbSO4 (anglesite), PbS (galena) and Pb5(PO4)3Cl (pyromorphite). Airborne dust samples were collected on the tailings piles using a PIXE Cascade Impactor which separates aerosol fractions onto nine impactor stages ranging from 16µm to 0.06µm. These stages were then analyzed by PIXE to obtain elemental concentrations. Samples of non-vegetated and vegetated near-surface tailings were collected for bioaccessibility tests as well as for total metal content, grain size distribution, and Pb speciation using ESEM and synchrotron techniques. Both airborne dust and near-surface tailings samples underwent synchrotron microanalysis including microXRD for identification of microcrystalline compounds and microXRF for element mapping and metal ratio evaluation. Despite extensive oxidation of iron sulfide minerals in the near-surface tailings, galena persists as the most abundant Pb-bearing phase in the pH-neutral tailings. However, rims of cerussite and hydrocerussite forming alteration rims on galena grains have been identified throughout the tailings. In vitro bioaccessibility testing of Pb in the tailings resulted in 0-0.05% bioaccessible Pb in lung fluid and 23-69% bioaccessible Pb in the gastric fluid. / Thesis (Master, Geological Sciences & Geological Engineering) -- Queen's University, 2012-02-28 21:09:08.432

High resolution molecular spectroscopic techniques are useful tools to accurately probe energy differences between quantum states of molecules. These energy levels are inherently dependent on the underlying potential functions, which ultimately govern the structures and dynamics of molecules. Thus, the detailed characterization of potential energy profiles through molecular spectroscopy provides important information about molecular properties. Given the increased structural and dynamic complexity of large molecules, small compounds serve as excellent prototypes to establish quantum mechanical models that accurately characterize quantum states and ultimately potential energy functions of various molecular classes. This thesis describes the use of rotational and rovibrational spectroscopy to probe one such class: four-membered heterocycles. Rotationally-resolved vibrational spectra of four-membered rings including β-propiolactone (c-C3H4O2), 3-oxetanone (c-C3H4O2), azetidine (c-C3H6N) and silacyclobutane (c-C3H8Si) were recorded below 1200 cm-1 using a Fourier transform infrared spectrometer (FTIR) with synchrotron light at the far infrared beamline of the Canadian Light Source (CLS). Additionally, Fourier transform microwave (FTMW) spectroscopy was used to study the pure rotational spectra of β-propiolactone and silacyclobutane for the first time. This allowed the accurate characterization of the ground vibrational state and molecular structure in support of the rovibrational analysis. The far infrared vibrational modes of these four molecules were analyzed individually initially and followed by a global fit of all observed transitions of each molecule. Unique spectroscopic signatures arising from Coriolis coupling(β-propiolactone, 3-oxetanone), tunneling motions (azetidine, silacyclobutane) and the large amplitude ring puckering vibration (3-oxetanone, azetidine, silacyclobutane) were revealed and treated. The resultant Hamiltonian models used for each molecule account for the observed spectra as the spectroscopic constants are consistent across the ground state and all vibrationally excited states studied. Collectively, these studies have provided a highly effective working protocol for the treatment of high resolution rovibrational data to model the dynamic behaviour of real molecules.

No description available.

Pressboard, a high density cellulose-based material used for insulation in high voltage power transformers, exhibits stress relaxation during compressive loading. Investigating the micro-mechanical mechanisms responsible for the relaxation can lead to modifications of the production process to control the behaviour of the material. This investigation can be done using Synchrotron X-ray micro Computed Tomography which provides sufficient temporal and spatial resolutions to capture the stress relaxation process. In the present thesis, a compression rig for in-situ mechanical loading during X-ray micro Computed Tomography was designed and constructed. Local tomography scans with sub-micrometre resolution were obtained at the TOMCAT beamline at the Swiss Light Source, Paul Scherrer Institut, Switzerland. Several fibre segmentation techniques are analysed, together with Optical Flow and Digital Volume Correlation (DVC), methods used for estimating displacement, strain and velocity vector fields. Suitability of the tested methods is evaluated, and it is found that segmentation of individual fibres in a cellulose material of such a high density is probably not possible using currently available segmentation techniques. The movements during relaxation are measurable at the used resolution, and can be estimated using Optical Flow. Further work into correction of image shift due to rig movement between scans, as well as image artefact reduction should allow for measurement and comparisons of displacement during relaxation as well as DVC-computed strain measurements during compression, recreating earlier results.