601 research outputs found
The development of a combustion temperature standard for the calibration of optical diagnostic techniques
This thesis describes the development and evaluation of a high-temperature combustion
standard. This comprises a McKenna burner premixed flame, together with a full
assessment of its temperature, stability and reproducibility. I have evaluated three
techniques for high-accuracy flame thermometry: Modulated Emission in Gases
(MEG), Rayleigh scattering thermometry and photo-acoustic thermometry.
MEG: Analysis shows that MEG is not usable in this application because the sharp
spectral features of the absorption coefficient of gases are represented within MEG
theory as an average absorption coefficient over the optical detection bandwidth. A
secondary difficulty arises from the lack of high power lasers operating at wavelengths
that coincides with molecular absorption lines in the hot gas.
Rayleigh Scattering: Applying corrections for the temperature-dependence of the
scattering cross-section, it has been possible to determine the temperature of the
combustion standard with an uncertainty of approximately 1%. The temperature
dependence of the scattering cross-section arises from changes in the mean molecular
polarisability and anisotropy and can amount to 2% between flame and room
temperatures. Using a pulse Nd-YAG laser operating at 532 nm and high linearity
silicon detectors, the Rayleigh scattering experimental system has been optimised.
Temperatures measured over a three-month interval are shown to be reproducible to
better than 0.4% demonstrating the suitability of the McKenna burner as a combustion
standard.
Photo-Acoustic: By measuring the transit time of a spark-induced sound wave past two
parallel probe beams, the temperature has been determined with an uncertainty of
approximate 1%.
Flame temperatures measured by the photo-acoustic and Rayleigh scattering
thermometry system show good agreement. For high airflow rates the agreement is
better than 1% of temperature, but for low airflow rates, photo-acoustic temperatures are
approximately 3.6% higher than the Rayleigh temperatures. Further work is needed to
understand this discrepancy
Biological applications of multimodal imaging involving Raman and 4Pi Raman microscopy
Raman microscopy is becoming an increasingly important label-free imaging technique. It proved to be a viable tool for life science applications allowing to analyze bacteria, cells, and tissues at the molecular level. Combining Raman microscopy with complementary imaging modalities and techniques is explored here to: (1) analyze mild traumatic brain injury (mTBI) in a combination with magnetic resonance imaging (MRI) for detecting mild, and invisible to medical imaging techniques, brain tissue damage; (2) reveal complementarity of Raman and fluorescence microscopy approaches for investigating and tracking bovine lactoferrin inside calf rectal epithelial cells in the presence of enterohemorrhagic Escherichia coli (EHEC); (3) apply Raman microscopy along-side the molecular analysis approaches (such as scanning transmission electron microscopy-energy dispersive X-ray (STEM-EDX), low energy X-ray fluorescence (LEXRF), nanoscale secondary ion mass spectrometry (Nano-SIMS)) to uncover the origin of the long-range conductance in cable bacteria; (4) develop multifunctional surface enhanced Raman scattering (SERS) platform based on calcium carbonate particles for enhancing a weak Raman scattering signal of biomolecules as well as to apply Raman microscopy for particle detection in vivo in Caenorhabditis elegans (C. elegans) worms; and (5) combine Raman microscopy and atomic force microscopy (AFM) to track Chlamydia psittaci in cells. Analysis of described above samples and phenomena is based on Raman molecular fingerprint images, where, similarly to fluorescence light microscopy, the resolution is limited by diffraction of light. Therefore, efforts are also put to enhance the resolution of Raman microscopy-based imaging by adding a 4Pi configuration to a confocal Raman microscope. As a result, a possibility to enhance the axial (also called longitudinal) resolution is investigated by constructing a 4Pi confocal Raman microscope, which is also applied to study bacteria inside cells. Results presented in this work emphasize the added value of multimodal microscopy approaches, particularly involving Raman microscopy, in a broad range of applications in bioengineering, biomedicine, and biology
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