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A major waste byproduct of oil sands in situ extraction is oil sands tailings, which are a mixture of water, clay, and residual bitumen. These tailings represent a huge ecological footprint in the form of tailings ponds, which not only render large land areas unusable but also prevent reuse of water. The slow dewatering of the tailings ponds poses a major challenge to the industry. The presence of complex inorganic−organic bitumen−clay mixtures in these tailings contributes to this problem. Hence, understanding the nature of the bitumen−clay association and the effect of bitumen on clay particle−particle interactions is important for the development of more effective chemicals or processes to accelerate particle aggregation and sedimentation during dewatering. Previous studies that investigate these interactions used techniques that are sensitive only toward inorganic clay but not sensitive towards organic bitumen. Here, we use a high-resolution total internal reflection fluorescence (TIRF) microscopy to help identify the accurate location and distribution of bitumen in mature fine tailings (MFT) samples. We report the first adaptation of TIRF beyond cell biology for visualization of bitumen and its interaction with clay. The high signal-to-noise ratio of TIRF microscopy and a high contrast between the clay and residual bitumen provide images that reveal a wealth of information about the bitumen coverage on clay as well as clay−clay aggregates and how the bitumen positions itself within these aggregates. These images confirm the presence of hydrophobic fine clay agglomerates along with the hydrophilic clay particles in MFT. It is also observed that bitumen coats clay particles, bridges clay agglomerates, and is mostly absent as free bitumen in the bulk of the MFT sample. Our work paves the way for the use of nanophotonic tools in oil sands imaging and provides strategic suggestions for the development of better methods for clay sedimentation and bitumen recovery.

Optical tomographic reconstruction of a 3D nanoscale specimen is hindered by the axial diffraction limit, which is 2-3 times worse than the focal plane resolution. We propose and experimentally demonstrate an axial super-resolution evanescent wave tomography (AxSET) method that enables the use of regular evanescent wave microscopes like Total Internal Reflection Fluorescence Microscope (TIRF) beyond surface imaging, and achieve tomographic reconstruction with axial superresolution. Our proposed method based on Fourier reconstruction achieves axial super-resolution by extracting information from multiple sets of three-dimensional fluorescence images when the sample is illuminated by an evanescent wave. We propose a procedure to extract super-resolution features from the incremental penetration of an evanescent wave and support our theory by 1D (along the optical axis) and 3D simulations. We validate our claims by experimentally demonstrating tomographic reconstruction of microtubules in HeLa cells with an axial resolution of ∼130 nm. Our method does not require any additional optical components or sample preparation. The proposed method can be combined with focal plane super-resolution techniques like STORM and can also be adapted for THz and microwave near-field tomography.Optical tomography is a major tool in threedimensional visualization of sub-micrometer scale specimens in biology, material sciences and nano-fabrication technology [1][2][3]. Tomographic reconstruction is done by optical sectioning of the object in the focal plane followed by 3D stitching of the acquired z-stack of focal plane images. Resolution of the 3D tomographic reconstruction of an object is therefore governed by the focal plane resolution and the axial resolution of the underlying optical image acquisition. A wide range of well advanced fluorescence based super-resolution microscopy techniques have been reported and are currently in practice [4]. Super-resolution [12] have increased the resolution in the axial direction with an almost spherical PSF. More recently a triple-view capture and fusion approach [13] has been reported to improve volumetric resolution by a factor of two. However, these * sarang.pendharker@ualberta.ca techniques require imaging and illuminating the same focal plane from both sides of the sample and depend on extensive optical components and precise optical phase matching. 3D STED [1] and 3D STORM [2, 3] for threedimensional localization have also been reported. Axial super-resolution can also be achieved by placing a reflective mirror behind the sample to squeeze the PSF in the axial direction by interference from the reflected STED beam [14,15]. However, STORM and STED impose constraints on properties of the fluorescent probes, limiting their applicability to image photo-switchable fluorophores and samples with a sharp emission spectrum, respectively. Evanescent wave illumination techniques like Total internal Reflection Fluorescence (TIRF) microscopy [16,17], Plasmon enhanced TIRF [18], variableangle TIRF [...

Purpose: Presence of shields obscures the radiographic visualization of dummy sources by coplanar imaging. In this study a reconstruction method, using non‐coplanar images, is tested for clinical use. Method and Materials: An isocentric dedicated imaging system with L&C‐arm rotation and networked to a treatment planning system (TPS) is used for filmless planning. Testing done by (1) using a ‘test phantom’ having radiopaque markers separated by known distance (2) using single straight applicator for standardization (3) by orienting the Fletcher‐Suit applicator with non‐shielded and shielded colpostats to simulate clinical situation. Source position reconstruction was done using orthogonal algorithm for coplanar images and ‘IBU reconstruction’ algorithm for coplanar & non‐coplanar images. Treatment length settings & active dwell positions were pre‐fixed . Spatial orientation of dummy source positions, dose‐volume histogram, dwell times, total treatment time were all generated. TPS calculated and delivered dose accuracy for both algorithms was checked for the straight applicator by using a 0.13cc ion chamber in a water phantom at various distances. Results: Distance variation using ‘test phantom’ for IBU method was found to be <1mm in the central region & <1.5mm in the corners of the fluoroscopic image and is comparable to the conventional orthogonal method. IBU method was also found to agree with the orthogonal method applicator with respect to source position co‐ordinates (<0.5mm), dwell time (<0.3%), total treatment time (<0.3%) and dose‐volume histogram analysis. The ratio of measured dose by both algorithms at various distances was close to unity. Reconstructed geometry of shielded colpostats by IBU non‐coplanar method was found to visibly match with the “three dimensional” projection. Conclusion: Non‐coplanar IBU algorithm provides an unambiguous reconstruction method when using shielded colpostats and allows for rapid filmless planning procedure.

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