Assessing the risk and relative value of commercial mortgage-backed securities issued in South Africa

Includes bibliographical references (leaves 164-170).The aim of the research is to assess the risks and current pricing of single-borrower/multi-property and multi-borrower/multi-property commercial mortgage-backed securities in South Africa and make investors aware of the potential pitfalls of investing in these new bond instruments

The effects of refinery effluent on the invertebrate intertidal fauna and flora of Little Wick Bay, Milford Haven

The effects of continuous low level oil pollution from a refinery effluent, on intertidal fauna and flora in Little Wick Bay are investigated. A shore survey of the intertidal species on six transects at varying distances from the effluent discharge point, is carried out and the results compared with past surveys of the same transects. Any differences or similarities in the findings are related to the environmental agencies in operation since the first survey. A detailed investigation of the size classes and abundance of the Limpet Patella vulgata at each of the six transects and a quantitative analysis of Petroleum Oil Pollutants in P. vulgata by Infra red Spectrophotometry is carried out in an attempt to relate findings to the effluent discharge

On trend robustness and end-point issues for New Zealand’s stylised business cycle facts

We present new empirical evidence on trend robustness and end-point issues, utilising the macroeconomic data set investigated in McKelvie and Hall (2012). We consider the relative merits of non-robust Hodrick-Prescott (HP) and robust loess (LOcal regrESSion) trend filtering methods, and assess the sensitivity of HP1600 stylised facts to (i) the considerable “supply shock” deviations from trend associated with New Zealand’s 1992 power crisis, and (ii) an alternative HP100 specification and the loess approach. On end-point issues, we assess value-added from the use of seven-point triangular moving average and HP1600 filters, relative to insights from a 21-quarter uniform moving average filter

Low-dimensional models of the transition to turbulence

The transition to turbulence in shear flows such as pressure driven pipe flow or plane Couette flow presents an interesting theoretical problem: how do we understand the existence of chaos when the laminar flow is stable to infinitesimal perturbations? A number of approaches to the problem have been used in recent years and a great deal of progress has been made towards understanding the transition, often utilising low-dimensional models to generate hypotheses. In the first part of this thesis I study the behaviour of a system of partial differential equations based on the damped Kuramoto-Sivashinsky equation which exhibit a subcritical transition to turbulence as a control parameter is varied. Typical lifetimes of the system are measured and align with the scenario for shear flows; they have an exponential distribution for a given value of the control parameter, and the typical lifetime scale superexponentially with that parameter. Coherent structures are found numerically and the linear stability measured to create a bifurcation diagram which is reminiscent of the ones found in shear flows. In the second part of the thesis a link is drawn between the apparent dynamical role of the lower branch states of the extended KS equation and the current understanding of transitional turbulence as belonging to the universality class of Directed Percolation (DP). A novel DP model is introduced which has a third state which represents the behaviour of the lower branches and the critical exponents of the system are measured and found to agree with the expected exponents for 1+1 dimensional DP. A non-universal parameter is found which varies with the strength of the bouncing behaviour, although it is unclear if it is possible to measure this parameter in a meaningful way for a real flow. Finally, in the third part of the thesis the extended KS equation is studied in an extended spatial domain, to confirm the hypothesis that this system also belongs to the DP universality class. Critical exponents are measured and found to agree with 1+1 DP. This confirms that the system has a transition which reproduces many of the important features subcritical fluid flows like pressure driven pipe flow, or plane Couette flow

Are sleep difficulties associated with cognitive functioning following acquired brain injury in an in-patient neuro-rehabilitation population?

Background: Sleep loss can impair cognition in healthy adults (Waters & Bucks, 2011). Poor sleepers post head injury (HI) have significantly worse sustained attention than good sleepers post HI (Bloomfield et al., 2010, Sinclair et al., 2013). Aims: The present study explores the relationships between objective and subjective sleep measures and overall cognitive functioning, sustained attention, memory and executive functioning in people with an Acquired Brain Injury (ABI) who are currently participating in inpatient neurorehabilitation. Methods: This study has a correlational design with exploratory between groups analyses. Twenty participants were recruited and their sleep was assessed using a subjective (Pittsburgh Sleep Quality Index; PSQI) and an objective (Actigraphy) measure of sleep. Cognitive tests were completed to determine current cognitive functioning on specific cognitive domains. Results: Self-reported sleep difficulties were associated with better overall cognitive functioning (r=0.46, N=20, p=0.04) and memory domain scores (r=0.50, N=20, p=0.01). No associations were found between Actigraphy and cognitive performance. There were discrepancies between subjective and objective sleep measures in 45% of participants. 67% of participants with discrepancies between sleep measures under reported poor sleep and 33% over reported poor sleep when compared to an objective measure. Exploratory analysis of clearly good and poor sleepers, defined by congruent objective and subjective sleep measures, revealed poor sleepers have significantly better memory cognitive domain scores than good sleepers (t(9)=2.27, p=0.049;d=1.37). Conclusions/Recommendations: The phenomenon of poor sleep and better memory performance may be explained by poor sleepers having better memory for their difficulties post injury than good sleepers or increased awareness of their current sleep patterns because their memory is better preserved. Clinicians should adopt an objective measure of sleep in addition to subjective measures of sleep when assessing sleep difficulties in an inpatient neurorehabilitation population. Patients who do not report sleep difficulties may in fact be experiencing sleep problems that that could impact on their neurorehabilitation schedule

A feasibility study of paired Continuous Glucose Monitoring (CGM) intra-partum and in the newborn in pregnancies complicated by Type 1 Diabetes

Aim: To describe the continuous glucose monitoring (CGM) profiles of type 1 diabetes (T1D) offspring in the early neonatal period and its association with maternal intrapartum glucose control. Methods: A prospective observational study of T1D pregnant women and their neonatal offspring. Women had a CGM sensor inserted 2-3 days prior to delivery. Infants had a masked CGM sensor inserted as soon as possible following delivery. Maternal glycaemic outcomes were time-in-target (70-140 mg/dL [3.9-7.8 mmol/L]), hyperglycaemia >140 mg/dL (7.8 mmol/L) and mean CGM glucose during the 24 hours preceding delivery. Neonatal outcomes included lowest recorded blood glucose concentration, and CGM measures (glucose 140 mg/dL (7.8 mmol/L), and 9 (9) % time < 70 mg/dL (3.9 mmol/L) with mean (SD) CGM glucose 113 (9) mg/dL (6.3 [0.7] mmol/L). 15 infants (93.8%) had ≥1 blood glucose concentration < 47 mg/dL (2.6 mmol/L) and five had ≥1 blood glucose concentration < 18 mg/dL (1.0 mmol/L). The mean infant CGM glucose on days 1, 2, and 3 of life was 63 (14), 67 (13), 76 (11) mg/dL (3.5 [0.8], 3.7 [0.7], and 4.2 [0.6] mmol/L). Four infants (25%) spent more than 50% time with CGM glucose levels < 47 mg/dL (2.6 mmol/L) on day 1. Conclusions: CGM detected widespread neonatal hypoglycaemia, even among mothers with good intrapartum glucose control

Nonequilibrium capillary self-assembly

Macroscopic objects supported by surface tension at the fluid interface can self-assemble through the action of capillary forces arising from interfacial deformations. The resulting self-assembled structures are ordered but remain trapped in one of potentially many metastable states in the capillary energy landscape. This contrasts with microscopic colloidal self-assembly where thermal fluctuations excite transitions between geometrically distinct ground-state configurations. We herein utilize supercritical Faraday waves to drive structural rearrangements between metastable states of few-particle clusters of millimetric spheres bound by capillary attractions at the fluid interface. Using a combination of experiments and theoretical modelling, we demonstrate how the occupation probabilities of different cluster topologies and transition statistics are controlled by the level of the vibrational forcing and the spatial extent of long-range capillary forces. Our results demonstrate how self-assembly dynamics and statistics may be manipulated across scales by controlling the strength of fluctuations and by tuning the properties of the particle interaction-potential