Single Molecule and Nanoparticle Imaging in Biophysical, Surface, and Photocatalysis Studies

Single molecule and nanoparticle imaging has become a very important tool to investigate many biological and chemical processes. This dissertation presents the applications of single molecule and nanoparticle imaging in biophysical, surface, and photocatalysis studies using far-field optical microscopy. The work was mainly carried out under a differential interference contrast (DIC) microscope and a total internal reflection (TIR) microscope. First, a DIC microscopy-based single particle orientation and rotational tracking technique that allows for resolving the full three-dimensional (3D) orientation of single gold nanorod (AuNR) probes has been developed. The angular degeneracy was overcome by combining DIC polarization anisotropy with the image pattern recognition technique. The usefulness of this technique in biophysical studies was further verified by real time tracking of rotational motions of single AuNRs rotating on live cell membranes. Therefore, it is expected that this method will enable us to elucidate the comprehensive interaction mechanisms between the functionalized nanocargoes and the membrane receptors in live cells. Detailed in situ conformational information on how they bind on the cell membrane and how they move and rotate in live cells at single particle level would provide new avenues for the development of new generation of high efficient drug and gene delivery carriers. Second, a high-throughput focused orientation and position imaging (FOPI) technique with 3D orientation resolvability for single AuNRs deposited on a gold film has been developed for surface studies. The FOPI method presented in this dissertation provides a new approach using the interaction of AuNRs with their surrounding environment for resolving the 3D orientation of single AuNRs. Therefore, it is expectedthat this method can be used as a tool to study interactions of functionalized nanoparticles with functional gold surfaces. Last, single molecule TIRF imaging was successfully employed in photocatalysis study to reveal the nature and photocatalytic properties of the surface active sites on single Au-CdS hybrid nanocatalysts. Single-molecule photocatalysis with high-resolution super-localization imaging allowed us to reveal two distinct, incident energy-dependent charge separation mechanisms in single Au-CdS heterostructures. This finding will help us design and develop better metal-semiconductor heterostructures that are highly active for photocatalytic reactions under visible light. Furthermore, the finding will enable us to potentially engineer the direction of energy flows on the heterostructured nanomaterials at the nanoscale. Therefore, it is expected that the results presented in this dissertation have a potential impact on the development of better photocatalyst structures

Chronic rhinosinusitis with nasal polyps in older adults : clinical presentation, pathophysiology, and comorbidity

Purpose of Review Chronic rhinosinusitis and nasal polyps (CRSwNP) is a common condition that significantly affects patients' life. This work aims to provide an up-to-date overview of CRSwNP in older adults, focusing on its aging-related clinical presentations, pathophysiology, and comorbidity associations including asthma. Recent Findings Recent large population-based studies using nasal endoscopy have shown that CRSwNP is a mostly late-onset disease. Age-related changes in physiologic functions, including nasal epithelial barrier dysfunction, may underlie the incidence and different clinical presentations of CRSwNP in older adults. However, there is still a paucity of evidence on the effect of aging on phenotypes and endotypes of CRSwNP. Meanwhile, late-onset asthma is a major comorbid condition in patients with CRSwNP; they frequently present with type 2 inflammatory signatures that are refractory to conventional treatments when they are comorbid. However, as they are more commonly non-atopic, causative factors other than classical atopic sensitization, such as Staphylococcus aureus specific IgE sensitization, are suggested to drive the type 2 inflammation. There are additional comorbidity associations in older patients with CRSwNP, including those with chronic otitis media and head and neck malignancy. Age is a major determinant for the incidence and clinical presentations of CRSwNP. Given the heterogeneity in phenotypes and endotypes, longitudinal investigations are warranted to elucidate the effects of aging on CRSwNP

String dualities and superpotential

The main objective of this thesis is the computation of the superpotential induced by D5-branes in the type IIB string theory and by five-branes in the heterotic string theory. Both superpotentials have the same functional form which is the chain integral of the holomorphic three-form. Using relative (co)homology we can unify the flux and brane superpotential. The chain integral can be seen as an example of the Abel-Jacobi map. We discuss many structures such as mixed Hodge structure which allows for the computation of Picard-Fuchs differential equations crucial for explicit computations. We blow up the Calabi-Yau threefold along the submanifold wrapped by the brane to obtain geometrically more appropriate configuration. The resulting geometry is non-Calabi-Yau and we have a canonically given divisor. This blown-up geometry makes it possible to restrict our attention to complex structure deformations. However, the direct computation is yet very difficult, thus the main tool for computation will be the lift of the brane configuration to a F-theory compactification. In F-theory, since complex structure, brane and, if present, bundle moduli are all contained in the complex structure moduli space of the elliptic Calabi-Yau fourfold, the computation can be dramatically simplified. The heterotic/F-theory duality is extended to include the blow-up geometry and thereby used to give the blow-up geometry a more physical meaning