Thesis advisor: Dawei Chen / We study the classes of several loci in the projectivization of the k-th Hodge bundle over the moduli space of genus g curves and over the moduli space of genus g curves with n marked points. In particular we consider the class of the closure in the projectivization of the k-th Hodge bundle over the moduli space of genus g curves with n marked points of the codimension n locus where the n marked points are zeros of the k-differential. We compute this class when n=2 and provide a recursive formula for it when n>2. Moreover, when n=1 and k=1,2 we show its rigidity and extremality in the pseudoeffective cone. We also compute the classes of the closures in the projectivization of the k-th Hodge bundle over the moduli space of genus g curves of the loci where the k-differential has a zero at a Brill-Noether special point. / Thesis (PhD) — Boston College, 2021. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Mathematics.

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Given a quiver flag variety Y equipped with a tilting bundle E, a construction ofCraw, Ito and Karmazyn [CIK18] produces a closed immersion f_E : Y -> M(E), where M(E) is the fine moduli space of cyclic modules over the algebra End(E).In this thesis we present two classes of examples where f_E is an isomorphism. Firstly, when Y is toric and E is the tilting bundle from [Cra11]; this generalises the well-known fact that P^n can be recovered from the endomorphism algebra of \oplus_{0\leq i \leq n} O_{P^n}(i). Secondly, when Y = Gr(n, 2), the Grassmannian of 2-dimensional quotients of k^n and E is the tilting bundle from [Kap84]. In each case, we give a presentation of the tilting algebra A = End(E) by constructing a quiver Q' such that there is a surjective k-algebra homomorphism \Phi: kQ' -> A, and then give an explicit description of the kernel.

Hemodialysis patients are at high risk of acquiring a blood stream infection (BSI), the second leading cause of death in this population. The purpose of this project was to create a clinical practice guideline (CPG) based on current evidence-based practice (EBP) that would bring a cohesiveness to the policies and provide an auditing tool to monitor infection control practices. Current literature supports the bundle approach, a small set of EBPs combined as a group of recommended interventions that apply to a specific patient population with the goal of improved delivery of care. The hemodialysis bundle project incorporated the theory of planned behavior to create a set of evidence-based interventions developed from an in-depth review of current, peer-reviewed studies. Three experts reviewed the CPG using the Appraisal of Guidelines for Research and Evaluation Instrument II; the scores from the 6 domains showed approval of the guideline as it was created with a score of greater than 90%. The three experts were chosen because they are responsible for updating and writing policies for the hemodialysis units. The creation of a CPG to improve infection control practices might benefit hemodialysis staff by providing an organized and cohesive method of following current policies. The new CPG might impact social change by applying current EBP to a clinical practice with end results of improving hemodialysis care and patient outcomes.

Hot-wire measurements of mean velocity and turbulence parameters were collected at the mid-point of a rod-wall gap and in the centre of a triangular subchannel in accelerating and decelerating flows through a large-scale (12.9:1) model of a 60\degree ~section of a CANadian Deuterium Uranium (CANDU) nuclear reactor 37-rod bundle. A method was developed to correct the axial velocity fluctuations for the effects of cycle-to-cycle variations, which were particularly significant during deceleration. Compared to values in stationary flows, the gap vortex street Strouhal number was slightly larger during accelerating flow and smaller during decelerating flow. The integral length scales of the axial velocity at both locations during both acceleration and deceleration were larger than the corresponding values in stationary flow. The Taylor microscale during transients was slightly larger than the stationary values. The turbulent kinetic energy dissipation rate was larger for accelerating flow and smaller for decelerating flow. The opposite was found to be true for the Kolmogorov microscale.

Vestibular hair cells are mechanotransducing sensory receptors in the vertebrate inner ear that detect movement and orientation of the head with respect to gravity. The morphologies of their ciliary bundles vary greatly for different species, endorgans, and within the same endorgan. Bundle morphology in the turtle utricle, like other species, demonstrates highly organized regional variations. These structural differences in bundles impact their mechanical behavior and the process of mechanotransduction. To further understanding of the mechanical behavior of hair bundles, this work experimentally measured the stiffness of bundles with differing morphology, the stiffness contribution of interciliary links and the mechanical properties of the kinocilium in the turtle utricle. The stiffness of hair bundles of varying structure and location along a medial to lateral transect of the utricle was examined. Bundle stiffness was greatest in the striola and demonstrated a systematic decline with location from the line of polarity reversal. The average stiffness of bundles in the striola and extrastriola were 82 ± 46 (n=48) and 9 ± 5 (n=25) µN/m, respectively. The stiff and weak bundles demonstrated characteristic morphologies. The stiffest bundles have short kinocilium, tall stereocilia, and ratios of kinocilium to tallest stereocilia height (KS) close to 1. In contrast, the compliant bundles have tall kinocilium, short stereocilia, and KS ratios ranging from 1.6 – 8. The stiffer bundles also tend to have longer array lengths and steeper slopes. Measurements of bundle stiffness in the turtle utricle are lower than those previously reported which may be attributed to morphological differences between species. The stiffness contributions of the interciliary links were also examined through their selective removal with exposure to the Ca²⁺ chelator BAPTA and the protease subtilisin. BAPTA treatment reportedly breaks tip, kinocilial and ankle links while subtilisin breaks the shaft and ankle links. Following BAPTA and subtilisin treatments, bundle stiffness reduced by 65 ± 10% and 63 ± 11%, respectively. The mechanical properties of the kinocilium were measured with novel techniques. Flexural rigidity (EI) was measure while the kinocilium was fixed at the height of the tallest stereocilia using a glass supporting probe. Through both force deflection and a high speed video technique, measured values of EI ranged from 1460 – 6150 pN·µm2. The rotational stiffness of the kinocilium about its apical insertion was also measured. Bundles were treated with BAPTA to break the kinocilial links and separate the kinocilium from neighboring stereocilia. Using a force deflection technique, the rotational stiffness of the kinocilium was measured as 120 ± 17 pN·µm/rad. / Ph. D.

Ventilator-associated pneumonia (VAP) is a serious complication in critically ill patients; it can prolong intubation, increase intensive care unit and hospital length of stay, and increase mortality to twice the level of patients who do not develop VAP. The purpose of this project was to determine the effect of an evidence-based educational program to prevent VAP on ICU nurses' actual and documented practices for preventing VAP. The research questions addressed whether an educational program focused on VAP prevention will affect critical care nurses' compliance with a VAP prevention bundle, and whether the education will result in maintenance of a rate of zero cases of VAP per 1000 ventilator days. Data will be collected from all ICU patients intubated more than 24 hours and will include: (a) the frequency of oral care, (b) head-of-bed elevation of 30-45 degrees, (c) daily sedation vacation, (d) assessment of readiness for extubation, and (e) whether prophylaxis for deep vein thrombosis and for peptic ulcer disease was ordered. Observations of care will verify the accuracy of nurses' documentation in the medical record. A survey will assess nurse satisfaction with the educational program. Paired t tests will be used to compare the compliance of the nurses with each element of oral care and hygiene practices before and after the intervention. Analysis of variance will be calculated on the mean duration of ventilation, mean ICU and hospital length of stay, mortality before discharge, patient acuity, and rates of VAP per 1000 ventilator days. The goal of this project is a compliance rate of 90% or greater with the elements of the VAP prevention bundle, leading to decreased ventilator and ICU days, decreased morbidity, decreased mortality, and lower emotional distress. Positive social change will be accomplished through an immediate improvement in the lives of VAP-prone individuals.

Two topics from nuclear engineering field are included in this dissertation. One study is the air-ingress phenomenon during a loss of coolant accident (LOCA) scenario, and the other is a 5-by-5 bundle assembly problem under a design of PWRs. The objectives are to investigate the Kelvin-Helmholtz instability of the gravity-driven stratified flows inside a coaxial pipe and the effects caused by two types of spacers at the downstream of the rod bundle problem. Richardson extrapolation is used for the grid independent study. Simulation results give good agreements with the experiments. Wavelet analysis and Proper Orthogonal Decomposition (POD) are used to study the flow behaviors and flow patterns. For the air-ingress phenomenon, Brunt-Vaisala frequency, or buoyancy frequency, predicts a frequency of 2.34 Hz, which is confirmed by the dominant frequency of 2.4 Hz obtained from the wavelet analysis between times 1.2 s and 1.85 s. For the rod bundle study, the dominant frequency at the center of the subchannel is given as 2.4 Hz with a secondary dominant frequency of 4 Hz and a much minor frequency of 6 Hz. Generally, wavelet analysis has much better performance than POD in the air-ingress phenomenon that is a strongly transient scenario; they both appropriate for the rod bundle study. Based on this study, when the fluid pair in a real condition is used, the time which air intrudes into the reactor is predictable.

ABSTRACT The flow-induced vibrations of tubes in a rotated triangular array subject to cross flow are investigated numerically and experimentally. The parameters are inlet velocity of cross flow, number of tube, and tube natural frequency. In the study, the instantaneous fluid forces on tube surfaces are computed numerically, the instantaneous displacement of the tubes due to the fluid forces is calculated, and thus the motions of the tubes in cross flow are described. Experiments are also conducted to compare the numerical results. The tube vibrations in a water tunnel are measured by two accelerometers. The amplitudes, spectra, and trace of tube motion are presented. The critical velocities of tube vibrations are then determined. Experimental results show that some tubes vibrate seriously when the flow velocity increases up to a critical value, and hysteresis of the tube vibrations is observed. In case of the seven-tube array, the tubes in the fourth row exhibit the most serious vibration. When the flow velocity is above the critical value, only one dominant frequency of the tube vibrations is detected, comparing to multiple dominant frequencies in subcritical condition. Furthermore, the tube in supercritical condition behaves like a limit cycle, especially when the natural frequency is equal to or near the vortex shedding frequency from the upstream tubes. It is also shown that the critical velocity decreases with more surrounding tubes in the upstream and does not change as more adjacent tubes are added in the downstream. However, the tube number seems to have no effect on the critical velocity when the tube natural frequency is far from the vortex shedding frequency.

Thesis (Ph.D.)--Virginia Commonwealth University, 2009. / Prepared for: Dept. of Pharmacology and Toxicology. Title from title-page of electronic thesis. Bibliography: leaves 84-94.