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Over the past decade, graphene/nanomaterial hybrids have gained a great interest in various applications due to their unique optical properties. This work explores lanthanide doped upconverting nanoparticles (UCNPs)/graphene hybrid nanomaterials. Here, core/shell structures comprising β-NaGdF4:Y b3+(20%),Er3+(2%)@NaGdF4 and α-NaGdF4:Y b3+(20%), Er3+(2%)@NaGdF4 with oleate as capping agent were synthesized and characterized. The choice of lanthanide ions (Yb3+ and Er3+) and their concentrations plays an important role to make these nanoparticles undergo two optical processes (upcoversion and downshifting) capable to convert near-infrared excitation to visible and near-infrared emission. In order to make hybrid systems, these nanoparticles were combined with graphene films. The morphology and the optical behavior of the hybrid samples were studied by microscope and hyperspectral imaging. The multi-energy sublevels from the 4f electronic configuration of lanthanides, their long excited state lifetime and the high carrier mobility of the graphene expected to open an exciting possibility of interaction, however, UCNPs/Graphene hybrid nanomaterial exhibits a minimal response when subjected to 980 nm laser illumination.

<p>The aerodynamic excitation of the diametral acoustic modes of an axisymmetric cavity-duct system is investigated experimentally. The change experienced by the acoustic diametral modes with the increase of the mean flow Mach number is investigated numerically. The first objective of this research is to examine the ability of the axisymmetric free shear layer forming along the cavity mouth to excite the asymmetric diametral modes which do not have preferred azimuthal orientations. The dependency of the system aeroacoustic response on both the cavity length and its depth is investigated to determine the limitations imposed by the relative dimensions of the cavity on the excitation process. The azimuthal behaviour of the self-excited diametral modes is also characterized.</p> <p> An experimental set-up is designed to ensure the coincidence of the frequencies of the shear layer oscillation with the acoustic resonance frequencies. The selection of the test section dimensions is based on finite element simulation of the acoustic diametral modes for several geometries. To simulate the diametral modes at different flow Mach numbers, a finite difference code is developed based on a two-step computational aeroacoustic approach. This approach allows the simulation of the acoustic field, taking into account the convection effect of the mean flow.</p> <p>The experimental results show that the diametral modes are very liable to be self-excited when the mean flow Mach number is higher than 0.1. The level of acoustic pressure during the diametral mode resonance increases rapidly with the increase of the ratio of the cavity depth, d, to the pipe diameter, D. However, the maximum acoustic pressure during each resonance decreases with the increase of the ratio of the cavity length, L, to the pipe diameter, D. The selfexcitation of the diametral modes is sustainable with d/D as small as 1/12. Further reduction in this ratio may result in complete suppression of the resonance. For deep cavities, d/D>3/12, the first and second diametral modes are more liable to excitation than the higher order modes. This is attributed to the fact that the low order modes have relatively higher radial acoustic particle velocity amplitude at the cavity mouth compared to the higher order ones. For d/D=l/12, the higher order modes have relatively higher radial acoustic particle velocity amplitude and consequently their tendency to be self-excited increases. For long cavities, L/D>2/3, the duct longitudinal acoustic modes start to be excited and become more dominant as the cavity length is further increased. The excitation mechanism of these longitudinal modes has not been investigated in this work since sufficient details already exist in the literature.</p> <p>The azimuthal behaviour of the diametral modes is characterized for all the tested cases. For short cavities, the diametral modes are classified as spinning modes; while for long cavities, L/D> 1/2, the orientation of the mode changes randomly over time. Small imperfections in the axisymmetric geometry result in what is described as partially spinning modes. An analytical model is developed to describe quantitatively the spinning behaviour of the diametral modes. The free shear layer and the diametral modes are found to be fully coupled in the azimuthal direction. The random behaviour of the diametral modes in the case of long cavities is attributed to the increase of randomness in the turbulent shear layer </p> <p>The numerical simulations show that the diametral modes experience considerable changes with the increase of the mean flow Mach number. At the cavity mouth, both the amplitude and phase distributions of the acoustic particle velocity are altered with the increase of the Mach number. This demonstrates the importance of considering the effect of the mean flow on the acoustic power production process. Moreover, the resonance frequency of the diametral modes decreases with the increase of the Mach number.</p> / Thesis / Doctor of Philosophy (PhD)

<p> In this thesis, two inner shell excitation spectroscopy techniques, inner shell electron energy loss spectroscopy (ISEELS) and near edge X-ray absorption fine structure (NEXAFS) spectroscopy, were used to measure the C ls, N ls and 0 ls spectra of the amino acids, glycine, alanine, cysteine, phenylalanine, proline, threonine, tryptophan and the peptides, Gly-Ala, Lys-Trp-Lys (KWK), and Arg-Gly-Asp (RGD). The spectra are analysed with the aide of ab initio computations using the GSCF3 method. The characteristic spectral features of the specific side chains of amino acids are identified. Differences in the spectra of the gas and solid are related to differences between the neutral gas phase molecule and the zwitterionic solid form. A rationalization of observations of high degree of variability in theN ls spectra of amino acids is proposed. The characteristic spectral signatures of peptide bonds have been identified further by comparing the spectra of small peptides to the spectra of their subunit amino acids. A modified "building block" approach is showed to be very useful in modeling the inner shell excitation spectra of peptides through linear combinations of the spectra of the amino acids residues and peptide bonds. </p> / Thesis / Master of Science (MSc)

<p> The potential of a mode-locked semiconductor laser oscillator as a short pulse source for two-photon fluorescence microscopy is explored. Amplification of the 1075 nrn laser is performed with a single pass semiconductor optical amplifier or a ytterbium-doped fibre amplifier. The mode-locked diode oscillator amplified by the Yb-doped fibre amplifier has been shown to produce uncompressed pulses of 4-10 ps with an average power of up to ~0.8 W. Compression with a single pass modified grating pair compressor reduces the pulse duration to as short as 860 fs. The output power level can be easily scaled to higher values. </p> <p> The ability to tightly focus the Yb-doped fibre amplifier beam and semiconductor optical amplifier beam for the purpose of microscopy is studied. Results indicate that the fibre performs close to an ideal Gaussian laser beam source. The semiconductor optical amplifier beam does not focus as well. Measurements suggest that regions of the beam, when focused, do not significantly contribute to the generation of two-photon fluorescence. </p> <p> The efficiency of two-photon fluorescence generation of the two amplifiers is compared to that of the conventional two-photon excitation source: the mode-locked titanium sapphire laser. Results illustrate the need to improve certain operating parameters of the laser oscillator and two amplifiers to be considered practical for two-photon fluorescence microscopy. The mode-locked semiconductor laser oscillator amplified by the Yb-doped fibre amplifier is deemed to be close to being ready for two-photon imaging applications. </p> / Thesis / Master of Applied Science (MASc)

During an earthquake, unanchored equipment within a nuclear power plant facility can slide and interact with safety-critical systems and components. Previous studies on sliding have largely focused on the response due to unidirectional excitation, as computing the response of unanchored components in three dimensions can be complex and computationally expensive. As such, several prediction equations and a standardized approximate method as outlined in ASCE 4-16 have been developed to estimate the peak sliding displacement. This study investigates the effect of bidirectional horizontal interaction and the influence of vertical excitation on the sliding response of an unanchored object when the x, y, and z, components of earthquake excitation are applied simultaneously. The study also evaluates the approximate method detailed in ASCE 4-16. A suite of 40 floor acceleration histories obtained from response history analysis of a representative nuclear power plant facility are used as input for the sliding model. A wide range of friction coefficients is selected for analysis and the nonlinear sliding response of components is determined through the use of a Bouc-Wen type hysteretic model. Computed responses under uni-, bi- and tri-directional excitation reveal that the effect of bidirectional interaction and vertical excitation is greatest for sites with high shaking intensity. It is also concluded that the ASCE 4-16 approximate method is significantly overconservative in all cases. Additionally, the study expands the concept of multi-component excitation to intensity measures. Twelve intensity measures are selected and evaluated. It is found that most efficient intensity measures vary in efficiency depending on the coefficient of friction, and that the top intensity measures are not significantly affected by incorporating multiple components of excitation. / Thesis / Master of Applied Science (MASc) / Earthquakes can pose a huge risk to nuclear facilities. Unanchored objects within the facility may collide and interact with safety-critical equipment. Previous research on sliding behaviour lacks information on the response of an object subjected to earthquake excitation in both the horizontal plane and vertical direction simultaneously. Several prediction equations and an approximate method have been developed to estimate the sliding response as it becomes computationally expensive to solve. This research investigates the influence of simulatenous multi-component excitation on the sliding behaviour and evaluates the current standardized approximate method of estimating sliding displacement. Recommendations are given based on the friction coefficient between the object and the base. The research also explores which characteristics of earthquake ground motion (e.g. acceleration, velocity, energy) are most indicative of sliding behaviour.

La douleur peut exercer un effet inhibiteur sur l'excitabilité corticospinale. L'anticipation de la douleur et la douleur elle-même semblent également avoir des bases neuronales communes. Ce projet visait donc à caractériser l'effet de la douleur et de son anticipation sur l'excitabilité corticospinale. La stimulation magnétique transcrânienne a été utilisée pour mesurer l'excitabilité corticospinale chez 15 sujets sains. Cinq conditions expérimentales ont été testées à l'aide d'une thermode, soit une condition neutre, deux conditions d'anticipation (chaleur et douleur), ainsi que deux conditions d'application (chaleur et douleur). Seule la condition de douleur a produit une inhibition significative de la voie corticospinale. L'anticipation de la douleur n'a pas modifié de façon significative l'amplitude des réponses musculaires évoquées par la TMS. Le fait que la douleur faible et de courte durée puisse induire une inhibition motrice suggère que la douleur modérée peut interférer avec une fonction motrice optimale.