Magnetic Resonance Imaging (MRI) has been used to provide high-resolution tomographic information, valuable in the study of static vocal tract. However, speech does not present a static behaviour but relies on the continuous and dynamic interaction of the vocal tract articulators and neighbouring tissues. Thus, this could make real-time MRI (rt-MRI) an essential tool to assess speech, with numerous advantages over the current clinical techniques. However, using rt-MRI to image the upper vocal tract remains challenging; the motion of the articulators, including the velum is fast while MRI data acquisition is slow thus inherently limiting temporal resolution. Additionally, an intrinsic loss in SNR, spatial resolution and/or visual image quality is present. The main focus of this thesis is to increase clinical reliability of rt-MRI in speech by investigating novel methodologies for the imaging of velopharyngeal motion. Firstly, commercial rt-MRI protocols at 1.5 T and 3 T were compared, regarding image quality and temporal resolution compromise. Optimal imaging protocols were suggested for both eld strengths. This provided a starting point for future clinical translation and the use of commercial and currently available protocols to image velopharyngeal motion. Furthermore, imaging of velopharyngeal motion was further improved with non-standard acquisition methods, such as non-Cartesian sampling and more advanced reconstruction schemes. An improved imaging protocol for the assessment of velopharyngeal motion was suggested. This was based on a highly accelerated radial trajectory with a novel parallel imaging reconstruction method (radial tt-GRAPPA). The suggested protocol not only allowed for improved image quality and image sharpness,but it was also viable for future clinical translation regarding o offline computation times compared to other reconstruction methodologies also investigated in this thesis. In summary, this thesis added some novel insights into the eld of speech rt-MRI, presenting improved and time effcient imaging protocols, adequate for the assessment of velopharyngeal motion.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Physics, 1981. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE. / Bibliography: leaves 55-56. / by Willie R. Mackey. / Ph.D.

Exact and distance-independent expressions for beam-shape coefficients (BSC's) in various cases are obtained. For a weakly focused beam in the two-dimensional (three-dimensional) case, the expression is shown equal (linearly related) to the value of the beam field at the distance of m/k ( ll+1 /k) from the origin, where m( l) is the azimuthal (principal) angular momentum number and k is the wavenumber. This provides a rigorous foundation for and a better understanding of the localization principle of van de Hulst. Furthermore, it gives corrections to the principle if the beam is more focused. With the knowledge of the asymptotic behavior of the positions and widths (or quality value) for the morphology-dependent resonances (MDR's) in Mie's scattering, the results are applied to discuss and answer questions regarding the excitation of high-Q MDR's by good collimated wave beams focused at positions essentially off the surface of the sphere. / Fu, Pengpeng = 波東形狀係數、局域化原理及米氏散射中的共振激發 / 傅芃芃. / Adviser: Hon Meng Lai. / Source: Dissertation Abstracts International, Volume: 72-04, Section: B, page: . / Thesis (Ph.D.)--Chinese University of Hong Kong, 2010. / Includes bibliographical references (leaves 75-81). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. Ann Arbor, MI : ProQuest Information and Learning Company, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese. / Fu, Pengpeng = Bo dong xing zhuang xi shu, ju yu hua yuan li ji Mi shi san she zhong de gong zhen ji fa / Fu Pengpeng.

Assembly of noble metal nanocrystals gives rise to extraordinary plasmonic properties that are distinct from those of isolated ones. We have prepared clusters that are composed of two-dimensionally-ordered gold nanocubes on flat substrates and investigated their plasmonic properties. It is found that the plasmon resonances of the nanocube clusters are highly dependent on both the number and ordering of the nanocubes in the clusters. FDTD calculations reveal that the rich plasmon modes in the clusters originate from the interparticle couplings in the cluster and the couplings between the entire clusters and the substrate. / I believe that my research work has provided an in-depth fundamental understanding of the localized surface plasmon resonances of gold nanocrystals and will have a number of implications for the applications of metallic nanostructures in optics, optoelectronics, and biotechnology. / Noble metal nanocrystals have attracted much interest due to their rich optical properties, which arise from the localized surface plasmon resonances, the collective oscillations of free electrons confined on the nanoscale. Under resonant excitation by light, noble metal nanocrystals exhibit extremely large light scattering and absorption, as well as large near-field enhancements. These fascinating properties bring about a variety of applications, including plasmonic sensing, plasmonic waveguiding, surface-enhanced Raman scattering, plasmon-enhanced fluorescence, photothermal cancer therapy, and plasmonic-enhanced energy harvesting. Among various noble metal nanocrystals, gold nanocrystals exhibit high chemical stability and large biological compatibility. Moreover, their plasmon resonance wavelengths can be synthetically tuned from the visible to near infrared spectral regions. In this thesis, a systematic study on the localized surface plasmon resonances of gold nanocrystals is presented, both experimentally and theoretically. / Photothermal conversion of gold nanocrystals can be applied in the areas of photothermal polymerization, photothermal imaging, drug release from capsules, and photothermal therapy. We have investigated the photothermal conversion properties of different gold nanocrystals and their composites. The studies show that the plasmon wavelength, particle volume, shell coating, and assembly of gold nanocrystals all play important roles in their photothermal conversion efficiency. / The refractive index sensitivity of gold nanocrystals is a key factor in their practical sensing applications. I will first introduce the systematic studies on the dependence of the index sensitivity on the shapes and sizes of gold nanocrystals that have varying plasmon resonance wavelengths. The index sensitivity has been found to generally increase as the plasmon resonance wavelength for a fixed nanocrystal shape becomes longer and as the curvature of the nanocrystals gets larger. I have further studied the dependence of the index sensitivity on the different shapes of gold nanocrystals that have the same longitudinal plasmon resonance wavelength. The refractive index sensitivities have been found to vary with the nanocrystal shape. Finite-difference time-domain (FDTD) calculations have been performed on these nanocrystals to reveal the origin of this dependence. A linear relationship is found between the index sensitivity and the product of the electric polarizability with the curvature. On the basis of these studies, a novel plasmonic optical fiber device has further been fabricated to detect small changes in the local dielectric environment. / When fabricating plasmonic devices, such as waveguides, optical switches, plasmonic sensors, and plasmon-enhanced solar cells, one needs to attach metal nanocrystals onto different substrates. The interactions between gold nanocrystals and the substrates can strongly modify the plasmonic responses of the nanocrystals and therefore need to be taken into account when designing of various plasmonic devices. We have further investigated the coupling between gold nanocrystals and substrates with different dielectric properties, including insulating, semiconducting, and metallic ones. It is found that the substrates play an important role in both the scattering patterns and scattering spectra of the supported gold nanocrystals. Specifically, Fano-type resonances can be observed for large nanocrystals sitting on silicon substrates that have a large dielectric constant. / Chen, Huanjun. / Adviser: Jianfang Wang. / Source: Dissertation Abstracts International, Volume: 72-04, Section: B, page: . / Thesis (Ph.D.)--Chinese University of Hong Kong, 2010. / Includes bibliographical references. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. Ann Arbor, MI : ProQuest Information and Learning Company, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.

Pang Kam Moon. / "June 2000." / Thesis (Ph.D.)--Chinese University of Hong Kong, 2000. / Includes bibliographical references (p. 134-137). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese. / Pang Kam Moon.

Introduction: The Elastography Software Library (ESL) was developed to achieve clinically feasible, super-resolution (SR) Magnetic Resonance Elastography (MRE). ESL was created by accomplishing four objectives: 1. perform a critical analysis of MRE inversion, using discrete-time Fourier transform (DTFT) methods, to enable selection of the wave inversion approach most suitable to high- and SR MRE (Chapter 2) 2. develop a new method for real-time 4D phase unwrapping, to enable large acquisitions to be processed in clinical work ow (Chapter 3) 3. develop a new inversion pipeline that recovers fine features in elastograms (Chapter 4) 4. extend this pipeline with a novel interpolation technique to achieve super-resolution (Chapter 5) The results of these experiments were combined to make the ESL. Over the course of the work, two objectives also resulted in software applications in their own right (PhaseTools for phase unwrapping, and Elastography Software Pipeline (ESP) for fine feature elasticity map recovery). Methods: Critical Analysis: Two-filter cascades were designed to model the signal processing pipelines found in the present MRE literature. These models were subjected to DTFT-based analysis to determine the relative advantage of various mathematical approaches to the MRE inverse problem. Phase Unwrapping: A test data set was developed to measure algorithm performance in 4D on data sets with varying levels of wrap, gradient and noise. The algorithms that performed most accurately and efficiently on test data were then applied to in vivo brain, liver, and muscle data, of both moderate and severe wrap, and inspected for wrap failure. Fine Feature Recovery: A new MRE image processing pipeline was developed that incorporates wavelet-domain denoising, image-driven noise estimation, and feature detection. ESP was first validated using simulated data, including viscoelastic Finite Element Method (FEM) simulations, at multiple noise levels. ESP images were then compared with Multifrequency Dual Elasto-Visco Inversion (MDEV) pipeline images in three ten-subject cohorts of brain, thigh, and liver acquisitions. Finally the proportion of spectral energy at fine frequencies was quantified using the Reduced Energy Ratio (RER) for both ESP and MDEV. Super-Resolution: An extension of the ESP pipeline was developed that incorporated a new image fusion technique to combine non-redundant information. The algorithm was validated on an analytic simulation program developed for the study. An in vivo cross-validation was performed between 1X, 2X and 4X magnification levels measuring both spectral gains and shear modulus values. Results: Critical Analysis: The more complex, heterogeneous FEM models were found to only outperform Algebraic Helmholtz Inversion (AHI) in very low noise, with Gaussian smoothing of σ > 0:8px or Butterworth low-pass cutoffs of < 0:8π negating any advantages from assumption of local heterogeneity. Phase Unwrapping: Three algorithms were determined to perform with sufficient robustness in real-time on 4D data sets with challenging phase wrap. These algorithms were then applied to in vivo brain, skeletal muscle, liver and phantom data and shown to successfully resolve heavy phase wrap within a \real-time" criterion of under 3 minutes. Fine Feature Recovery: For FEM inversions, mean values of background and soft target simulated results remained within 8% of prescribed up to σ = 10% for both jG*j and ϕ, though inspection of the ϕ image showed scatter- and boundary-related artefacts around the soft target. Hard target results showed jG*j means within 7% of prescribed up to σ = 5% but unreliable ϕ means, and inspection showed showed scatter- and boundary-related artefacts. For the in vivo cohorts, ESP results showed mean correlation of R = 0:83 with MDEV and liver stiffness estimates within 7% of Local Frequency Estimation (LFE) results. Finally, ESP showed statistically significant increase in fine feature spectral energy as measured with RER for both jG*j (p < 1X10-9) and ϕ (p < 1X10-3). Super-Resolution: At 4X SR, both brain and liver cohorts showed a highly significant (p ≤ 10-6) increase in both number of recovered frequencies and normalised spectral energy in those recovered frequencies. Both the 2X and 4X SR techniques showed a decrease in stiffness estimate from the original resolution (mean decrease of 11.6% and 14.0%) respectively; however cohort correlations between SR and original values were upwards of R = 0:988. Discussion: Established as a technique highly sensitive to important tissue changes, MR Elastography is now also a finely-featured super resolution technique in two parameters, enabling new clinical and research applications. Future work includes statistical mapping of both localised and diffuse soft tissue changes, rapid computation on heterogeneous processing architectures, and two-parameter super-resolution MRI-based lesion mapping.

The content of this thesis is based upon the interaction of light with metallic nanoparticles arranged in different array geometries. An incident electric field (light) can force the conduction electrons of a metallic nanoparticle to oscillate. At particular frequencies, in the optical regime for gold and silver particles, absorption and scattering of the light by the particle is enhanced, corresponding to the particle plasmon resonance. The spectral position and width of the particle plasmon resonance of an isolated single particle may be tuned by adjusting its size and shape, thus changing the surface charge distribution. Periodic arrays of particles offer additional control over the frequency and width of the resonance attributed to the re-radiating (scattering) property of plasmonic particles. By fabricating arrays with a pitch comparable to the wavelength of an isolated single particle plasmon resonance, a coherent interaction between particles may be produced, known as surface lattice resonances (SLRs). The electromagnetic coupling between in-plane particle plasmon modes for different particle array geometries is explored through experiment and theory. Firstly, SLRs in square, hexagonal and honeycomb arrays are investigated by normal-incidence extinction measurements and compared to a simple-coupled dipole model. Secondly, to verify the nature of the coupling between the scattered electric field associated with particle resonances, the incident electric field polarization-dependence of the extinction of rectangular arrays and chains is studied. Thirdly, the optical response of square arrays with a symmetric two-particle basis is investigated, particularly the retardation of the scattered electric field between particles in a pair. Fourthly, square arrays with an asymmetric two-particle basis are fabricated to explore the symmetric (dipole moments of both particles are parallel) and anti-symmetric (dipole moment of both particles anti-parallel) SLRs, excited by normal-incidence light.

Neurophysins (NPs) make up a relatively small, stable, and highly soluble class of proteins. They have physiological roles of storage and stabilizing' of peptide hormones oxytocin and vasopression within the posterior pituitary neurosecretory granules. At the concentration of NP found within the granules, NP would exist as a dimer in the absence or presence of bound peptide. The NP monomer-monomer interface involves B-sheet/ B-sheet contact, which can be modulated by the presence of cosolvent. This remarkable feature of NP makes it a model for Alzheimer's disease. One of the characteristics of Alzheimer's disease is the presence of plaques of B-amyloid protein that are deposited on the brain. The plaques are rich in B-structure. Being water-insoluble makes them impossible to be directly studied by solution-state NMR. The purpose of this study was to modify the solvent system to lower the NP dimerization constant and characterize the nature of solvent on dissociation of dimer. A set of cosolvents was selected to try to reduce NP dimerization at relatively high concentration of NP. The organic cosolvents included deuterated methanol, dimethyl sulfoxide, ethyl acetate, propionitrile, and acetonitrile. Also, the protein unfolding reagents, deuterated urea and guanidine monohydrochloride, were tried. The interaction between bromophenol blue and NP was also studied because this dye binds predominately to the dimer form of NP. Highresolution NMR techniques were used to sense the NP-I dimer I monomer equilibrium. Among the organic cosolvents used, only acetonitrile and propionitrile were found shift the dimer ~ monomer equilibrium significantly toward monomer. The cosolvent probably changed the character of the solvent system, penetrated the monomer-monomer interface and interacted with the interface residues, caused the break up of dimer. The unfolding reagents were found to partly unfold the NP simultaneously with dissociation of the dimer. Bromophenol blue binds to NP-I at low pH, but the solubility of NP-dye complex is too low to be studied extensively by solution-state NMR methods.

How do we maintain our own authentic voice while still being a productive member of a group? How do we not lose our voice and our meaning to the collective? This thesis is a series of stories that examines one student's experience with the intersection of music, education, technology, and personal life. It is a document of resonance, identifying interdisciplinary events and ideas that amplify each other, helping the student to extract and apply meaning in times of hope and challenge, peace and chaos, and serenity and sorrow, using the Scholarly Personal Narrative (SPN) approach. The chapters shape the explorations. The first chapter of this thesis expresses the importance of Listening to our own voice. Chapter 2 explores Dissonance, the tension that challenges us to examine what we believe to be true in our own voice. The third chapter examines Empowerment, looking to the head, heart and gut, carried on our breath, to find success by using our own authentic voice. Chapter 4 looks at Liberation, and the steps we take to reclaim our voice when it is being suppressed. Chapter 5 shares the healing power of music, examining its relationship to Memory. The last chapter attempts to pull all of these ideas together by exploring the relationship between personal Identity and Belonging.

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