Thesis (M. Arch.)--University of Hong Kong, 2004. / Includes special report study entitled: Perception of space. Also available in print.

Inaug.-diss.--Giessen. / Lebenslauf. "Literaturverzeichnis": p. [5]-8.

Since their discovery Neanderthals were described as having a marked degree of anteroposterior curvature of the femoral shaft. Although initially believed to be pathological, subsequent discoveries of Neanderthal remains made femoral curvature as well as the lateral curvature of the radius to be considered derived Neanderthal features. Femoral curvature has previously been used in racial identification in modern humans but its functional significance is poorly understood. A recent study on Neanderthals and early modern humans found no differences in femoral curvature, but did not consider size-corrected curvature. Therefore, the objectives of this study were to 1) use 3D morphometric landmark and semi-landmark analysis to quantify bone curvature (femur, ulna, radius) in Neanderthals, Upper Palaeolithic and recent modern humans, 2) compare adult bone curvature between these populations, and 3) test hypotheses on the effects of climate, body size, and activity patterns on curvature. Comparisons between and within populations were made using geometric morphometries (3D landmarks) and standard multivariate methods. Comparative material involved all available Neanderthal and Upper Palaeolithic modern human femora, ulnae and radii, archaeological (Mesolithic, Neolithic, Medieval) and recent human populations representing a wide geographical and lifestyle range. The study found that there are significant differences in the anatomy of the femur, ulna and radius between Neanderthals and modern humans. Neanderthals have more curved femora and radii than modern humans. Early modern humans are most similar to recent modern humans in their anatomy. Recent modern human analyses indicate that femoral curvature and forearm curvature are responses to disparate influences. Femoral curvature is a good indicator of activity level and habitual loading of the lower limb. Curvature of the forearm is a consequence of cold adaptation and its purpose is to maintain biomechanical function of the forearm despite its foreshortening.

In this thesis I examined the effects of task switching on people's ability to ignore irrelevant distractors. Load theory proposes that distractor interference critically depends on the availability of executive control to minimise the effects of irrelevant stimuli (e.g. Lavie, 2000). Much work on task switching suggests that task switching demands executive control in order to prepare for and implement a switch between tasks (e.g. Monsell, 2003 Rubinstein, Meyer, & Evans, 2001). I therefore hypothesised that the executive demand of a task switch will result in reduced ability to reject irrelevant distractors in selective attention tasks. The research reported provided support for this hypothesis by showing that task switching results in greater distractor interference as measured with the "flanker task" (e.g. Eriksen & Eriksen, 1974) and with the attentional capture task (e.g. Theeuwes, 1990), even when there was no overlap between the stimuli and responses for the two tasks, and when task-repeated and switch trials were presented within the same block (in AAABBB designs). This research also showed that dissociable executive demands were involved in switching tasks (AAABBB), compared with mixing tasks (ABAB versus AAA), and these executive demands were found to control rejection of distractors in the flanker task and attentional capture task, respectively. In addition, task switching reduced internal distraction by task-unrelated thoughts. The contrast between the effects of task switching on internal versus external sources of distraction further supported the involvement of executive control in task switching. Finally, individual differences in operational span capacity predicted the magnitude of task switching costs and flanker interference effects, suggesting the involvement of executive control in both abilities. Overall, this research highlights a new consequence of task switching on selective attention and distractibility, supporting predictions derived from prevalent views on the role of executive control in task switching and selective attention.

The development of hydrogen as an energy transfer mechanism is of great importance to alleviate environmental damage and economic destabilisation caused by over-reliance on oil, as long as the hydrogen can be generated renewably. To be suitable for road transport applications, safe and compact hydrogen storage systems need to be developed, the primary technological motivation for this PhD project which investigates hydrogen absorbed into graphite intercalation compounds (GICs), to gain a fundamental physical understanding of the sorption processes to improve such materials' capacity for hydrogen storage. Literature searching has led to a principal investigation, primarily using neutron scattering and thermogravimetry, of potassium and calcium-GICs with hydrogen. Inelastic neutron scattering on hydrogenated KC24 has shown hydrogen sorption in this system to be quantitatively different from its analogues RbC24 and CsC24. A consistent model of the H2 sites and dynamics has been proposed. Time-resolved structural data on the hydriding phase transition in KC8Hx have been obtained. A calcium-ammonia intercalate has shown most promise for hydrogen storage, with uptake of 3.2 wt.% H2 at 77 K and 2 bar, a signifcant amount of the 6 wt.% target set by the US DoE. It is concluded that available internal volume and donor charge in GICs are critical parameters for optimising hydrogen uptake.

In recent years, the experiences of sportspeople living with a chronic illness/disorder have seen an emergence within the narrative literature (Smith, 1999; Carless & Sparkes, 2008; Stone, 2009). However, epilepsy has been noticeably absent. As epilepsy and exercise research is mostly quantitative and medico-scientific in nature (Arida, Guimares de Alameida, Cavalheiro, & Scorza, 2013; Dubow & Kelly, 2003; Nakken, 1999; Wong & Wirrell, 2006), there is no qualitative research to show the experiences of sportspeople exercising with epilepsy. Although exercise has shown to be beneficial for most people with epilepsy (Arida, Scorza, & Cavalheiro, 2010; Eriksen, Ellertsen, & Hestad, 2002; Nakken, 1999), research reveals that people with epilepsy often refrain from exercise (Ablah et al., 2009; Nakken, 1999; Sirven, 2009). Furthermore, exercise-induced seizures (EIS) provide a frustration as well as an incentive to refrain from physical activity (Nakken, 1999; Sturm, Berkovic & Reutens, 2002). Therefore, the aim of this research was to provide a glimpse into the narrative experience(s) of a sportsperson/people with epilepsy (SWE) over the course of one year. Using four semi-structured interviews with four participants, differences in experience over time as well as across athletic identity, sport type, and seizure type and frequency were represented. A holistic-content approach and structural analysis were used to analyse the narratives (Carless & Sparkes, 2008; Frank, 1995; Lieblich, Tuval-Mashiach, & Zilber, 1998). Results have shown the importance of time in the narrative construction of the SWE. Presenting a new narrative type, vicious cycle, these narratives also portrayed similar findings as was shown in Lieblich et al. (1998) (e.g., the steady, progressive, and trial and error narrative). The participants expressed a sense of freedom, body control, and mental clarity linked to exercise. These positive benefits encouraged the participants to continue even if hampered by uncontrolled seizures. Furthermore, outside variables (e.g., time, seizure frequency and type, social support, stigma, and athletic identity) have shown to have an affect on the thoughts/ actions of SWE in regards to exercise. Through this research, SWE will have a voice within research. Through this research, the SWE’s story will be told. In turn, it is desired that this new insight leads practitioners to develop and implement more effective ways for SWE to cope with the transition of diagnosis.

Class of 2013 Abstract / Specific Aims: The objective of this study is to evaluate the effect of early blood glucose correction in the Emergency Department (ED) on hospital length of stay. Methods: This study has received institutional review board approval. This is a retrospective cohort study conducted in an academic medical institution. Diabetic patients with hyperglycemia in the ED between June 1st, 2011 and June 30th, 2012 were included. Patients were excluded if they were less than 18 or greater than 89 years of age, not admitted, had diabetic ketoacidosis or hyperglycemic hyperosmolar state, treated with insulin for hyperkalemia, trauma patients, or had an initial blood glucose value of 200 mg/dL or less. Patients were categorized into two groups based on blood glucose control achieved within the first 24 hours from triage. The primary outcome of this study was to compare hospital length of stay between the groups. Main Results: A total of 161 patients were included in this study. Baseline demographics between groups were statistically similar with the exception of gender (p=0.635), ethnicity (p = 0.149), and co-morbidities calculated by the Charlson Co-Morbidity Score (p = 0.112). Blood glucose values in the ED did not statistically correlate to hospital length of stay (p = 0.299), however, co-morbidities were predictive of hospital length of stay (p = 0.025). Conclusion: Early correction of blood glucose values in the ED are not associated with hospital length of stay.

Radio Frequency Interference (RFI) is a massive problem for radio observatories around the world. Due to the growth of telecommunications and air travel RFI is increasing exactly when the world's radio telescopes are increasing significantly in sensitivity, making RFI one of the most pressing problems for astronomy in the era of the Square Kilometre Array (SKA). Traditionally RFI is dealt with through simple algorithms that remove unexpected rapid changes but the recent explosion of machine learning and artificial intelligence (AI) provides an exciting opportunity for pushing the state-of-the-art in RFI excision. Unfortunately, due to the lack of training data for which the true RFI contamination is known, it is impossible to reliably train and compare machine learning algorithms for RFI excision on radio telescope arrays currently. To address this stumbling block we present RFIsim, a radio interferometry simulator that includes the telescope properties of the MeerKAT array, a sky model based on previous radio surveys coupled with an RFI model designed to reproduce actual RFI seen at the MeerKAT site. We perform an indepth comparison of the simulator results with real observations using the MeerKAT telescope and show that RFIsim produces visibilities that mimic those produced by real observations very well. Finally, we describe how the data was key in the development of a new state-of-the-art deep learning RFI flagging algorithm in Vafaei et al. (2020.) [69] In particular, this work demonstrates that transfer learning from simulation to real data is an effective way to leverage the power of machine learning for RFI flagging in real-world observatories.

In this thesis we study the chaotic behavior of multidimensional Hamiltonian systems in the presence of nonlinearity and disorder. It is known that any localized initial excitation in a large enough linear disordered system spreads for a finite amount of time and then halts forever. This phenomenon is called Anderson localization (AL). What happens to AL when nonlinearity is introduced is an interesting question which has been considered in several studies over the past decades. Recent works focussing on two widely–applicable systems, namely the disordered Klein-Gordon (DKG) lattice of anharmonic oscillators and the disordered discrete nonlinear Schr¨odinger (DDNLS) equation, mainly in one spatial dimension suggest that nonlinearity eventually destroys AL. This leads to an infinite diffusive spreading of initially localized wave packets whose extent (measured for instance through the wave packet's second moment m2) grows in time t as t αm with 0 < αm < 1. However, the characteristics and the asymptotic fate of such evolutions still remain an issue of intense debate due to their computational difficulty, especially in systems of more than one spatial dimension. Two different spreading regimes, the so-called weak and strong chaos regimes, have been theoretically predicted and numerically identified. As the spreading of initially localized wave packets is a non-equilibrium thermalization process related to the ergodic and chaotic properties of the system, in our work we investigate the properties of chaos studying the behavior of observables related to the system's tangent dynamics. In particular, we consider the DDNLS model of one (1D) and two (2D) spatial dimensions and develop robust, efficient and fast numerical integration schemes for the long-time evolution of the phase space and tangent dynamics of these systems. Implementing these integrators, we perform extensive numerical simulations for various sets of parameter values. We present, to the best of our knowledge for the first time, detailed computations of the time evolution of the system's maximum Lyapunov exponent (MLE–Λ) i.e. the most commonly used chaos indicator, and the related deviation vector distribution (DVD). We find that although the systems' MLE decreases in time following a power law t αΛ with αΛ < 0 for both the weak and strong chaos cases, no crossover to the behavior Λ ∝ t −1 (which is indicative of regular motion) is observed. By investigating a large number of weak and strong chaos cases, we determine the different αΛ values for the 1D and 2D systems. In addition, the analysis of the DVDs reveals the existence of random fluctuations of chaotic hotspots with increasing amplitudes inside the excited part of the wave packet, which assist in homogenizing chaos and contribute to the thermalization of more lattice sites. Furthermore, we show the existence of a dimension-free relation between the wave packet spreading and its degree of chaoticity between the 1D and 2D DDNLS systems. The generality of our findings is confirmed, as similar behaviors to the ones observed for the DDNLS systems are also present in the case of DKG models.

Includes bibliographical references. / The focus of the dissertation was to provide an in depth investigation towards the fatigue performance of Carbon Fiber Reinforced Polymers (CFRP) which were externally bonded onto concrete beams as a repair and strengthening technique for internally corrosion damaged RC beams. It was identified that more research concerning the fatigue performance of externally bonded CFRP laminates used as a composite material for originally damaged concrete structures was required. Therefore, there was a need to study the failure mechanisms between the externally bonded CFRP, corrosion damaged internal steel, and patch repaired section and the original substrate concrete with respect to the long term performance, whilst treating the system (CFRP, substrate concrete, patch repair and bonding agents) as a composite material. The methodology of the dissertation included the introduction of accelerated corrosion techniques to degrade the internal steel reinforcement. The damaged RC beams were repaired by removing the damaged concrete, treating the corroded internal steel reinforcement, replacing the damaged concre te section removed with a rapid-hardening high strength patch repair mortar, and finally externally bonding CFRP laminates along the patch repaired section and entire tensile face to restore the bending capacity lost due to the reduction of internal steel and subsequent patch repair. Two of the six RC beams which were patch repaired and CFRP strengthened, were subjected to a monotonic load in order to establish the ultimate static load at failure for the RC beams. The ultimate static load at failure was then used to derive the maximum imposed cyclic fatigue loading that was applied. The remaining four RC beams were then subjected to constant sinusoidal cyclic loads at varying amplitudes, the range of amplitude dependent on the corresponding static load at failure for the identical RC beam. The aim of the cyclic load tests was to determine the long term behaviour of the repaired and strengthened RC beams at different degrees of loadings . The test specimens were tested until fatigue failure was reached. At utimate fatigue failure, the RC beams exhibited excessive concrete cracking, but eventual fatigue failure was determined when the CFRP finally delaminated along a portion or the entire length of the tensile face. It was evident that once fatigue failure occurred due to concrete cracking, the fully laminated CFRP would then withstand a large majority of the tensile stresses still being applied. The CFRP momentarily restored the overall strength of the repaired and strengthened RC beam until ultimate failure occurred at the point of CFRP delamination. The outcome of the dissertation observes and describes the failure mechanisms during RC beam and CFRP fatigue failure. The results obtained from the extensive testing plot a failure curve for each RC beam which had been corroded, patch repaired and finally CFRP strengthened. The cumulative results captured display a predicted failure curve graph. This graph indicates the percentage of ultimate cyclic load applied which was a function of the corresponding ultimate static load applied for an identical RC beam versus the number of cycles applied until failure. This curve can be used as a guideline to predict the number of cycles until failure for a repaired and CFRP strengthened RC beam of similar dimensions for a specific percentage of static loading, this loading being dependent on the increased ultimate static load at failure for a patch repaired and externally strengthened CFRP reinforced concrete beam. The predicted failure curve clearly indicates that for repaired and CFRP strengthened RC beams experiencing low fatigue cyclic amplitudes equaling 45% of the corresponding total static loading at failure, the fatigue performance is significantly increased versus the identical test specimens with increased loading of approximately 55 % and 67% of the corresponding ultimate static loads, these beams exhibit considerably decreased long term performance. The static load tests also indicated that the influence of the accelerated corrosion on the ultimate capacity of the RC beam is minimal since the addition of the externally bonded CFRP doubled the ultimate static capacity of the identical RC damaged beams. The experimentation was also able to capture the failure mechanisms for each tested beam throughout the cyclic loading phase. Identifying the failure mechanisms was useful when conducting on site investigations which focused on the long term performance of either the reinforced concrete beams that were patch repaired and strengthened or not As expected, the combination of combining a high strength patch repair mortar and external CFRP strengthening scheme significantly increased the long term performance of the RC structure. Finally, due to the investigations performed in this dissertation, the increased long-term performance of a patch repaired and CFRP strengthened RC beam can now be empirically quantified and the failure mechanisms physically observed.