Masters of Science in Medicine / The relationship between COPD and laryngopharyngeal sensitivity has not been previously determined. Limited research into the relationship between COPD and swallow function suggests that patients with COPD are at increased risk of aspiration. One possible mechanism for this is a reduction in laryngopharyngeal sensitivity (LPS). Reduced laryngopharyngeal sensitivity (LPS) has been associated with an increased risk of aspiration in pathologies such as stroke, however impaired LPS has not been examined with respect to aspiration risk in COPD. The Aims of this study were to investigate the effect of COPD on laryngopharyngeal sensation using Laryngopharyngeal Sensory Discrimination Testing (LPSDT) and to determine whether a relationship between LPS and swallow function in patients with proven COPD exists. Method: 20 patients with proven COPD and 11 control subjects underwent LPSDT utilising an air-pulse stimulator (Pentax AP4000) via a nasendoscope (Pentax FNL10AP). The threshold of laryngopharyngeal sensation was measured by the air pressure required to elicit the laryngeal adductor reflex (LAR). A number of further examinations were also completed for COPD subjects. These included respiratory function testing, self-reporting questionnaire on swallowing ability (SSQ), bedside clinical examination of swallowing (MASA) and endoscopic assessment of swallowing (EAS). Results: subjects with COPD had a significantly higher LAR threshold when compared to their normal healthy counterparts (p<0.001). Positive correlations were identified for the relationships between MASA score and EAS results for presence of laryngeal penetration / aspiration (p<0.04), vallecular residue (p<0.01) and piriform residue (p<0.01). Conclusion: Patients with COPD have significantly reduced mechanosensitivity in the laryngopharynx. Patients with COPD also have impaired swallow function characterised primarily by pharyngeal stasis. These changes may place patients with COPD at increased risk of aspiration.

Visual field testing, or perimetry, measures peripheral visual loss in eye diseases such as glaucoma. Rarebit Perimetry (RBP) is a new and novel perimetric method, introduced in 2002 by Lars Frisén (2002), with the aim of detecting low degrees of neural damage within the retina. / RBP is unlike conventional perimetric methods that measure levels of retinal sensitivity, but instead uses very bright (i.e. suprathreshold) and very small targets to detect tiny areas of absolute blindness within otherwise normal areas of vision. RBP thus claims to locate miniscule gaps in the receptive field matrix of neurons in the retina, with the assumption that dead neurons leave gaps in this matrix. The most useful application of this idea is to detect progressive eye disease in the earliest stages (Frisén, 2002). Current research shows that RBP correlates with other standard visual field tests (Brusini, Salvetat, et al., 2005; Frisén, 2003; Gedik, Akman, et al., 2007; Martin & Wanger, 2004), but may afford greater sensitivity by detecting very mild visual losses missed by other tests (Martin, Ley, et al., 2004; Martin & Nilsson, 2007; Nilsson, Wendt, et al., 2007). / To date, there are no studies that definitively test the theoretical basis of RBP, so in this thesis I aim to explore the proposed underlying mechanisms and assumptions of this test. In particular, the proposed mechanism of RBP leads to specific predictions as to how responses will alter when the luminances of the RBP targets are systematically decreased. I therefore compared RBP responses of mean hit rate as a function of target luminance and found results to be inconsistent with the proposed RBP mechanism. Mathematical simulations were performed to explore reasons for the differences between the two groups (Chapter Seven).

It is commonly assumed that the goal of stereovision is computing explicit 3D scene reconstructions. We show that very accurate camera calibration is needed to support this, and that such accurate calibration is difficult to achieve and maintain. We argue that for tasks like recognition, figure/ground separation is more important than 3D depth reconstruction, and demonstrate a stereo algorithm that supports figure/ground separation without 3D reconstruction.

This thesis seeks to identify locations in which errors in numerical model initial conditions may compromise skill in tropical cyclone (TC) track forecasts. Two major TCs that made landfall in 2008 are analyzed: Hurricane Ike and Typhoon Sinlaku. In order to examine the sensitivity of the TC to selected synoptic features, a vorticity perturbation technique is developed. Within a chosen radius and atmospheric depth, the vorticity is amplified or decreased, followed by a re-balancing of the fields. The following questions are proposed: (1) How does the TC track vary with respect to initial perturbations of differing amplitude, spatial scale and distance to the storm? (2) How does the evolving perturbation act to modify the synoptic environment surrounding the TC, and thereby the track? (3) Is it best to follow an objective technique to determine the sensitive areas, or is it better to use a subjective method based on fundamental synoptic reasoning? Utilizing the Weather Research and Forecasting (WRF) model, the ?control? simulation for each TC is found to replicate forecast errors evident in the operational global models. For Sinlaku, this includes a premature recurvature in the forecast. For Ike, this comprises a landfall too far south along the Texas coast due to no recurvature being forecast. The size, magnitude and location of vorticity perturbations to the control analysis are chosen subjectively. For Sinlaku, these locations include a large mid-latitude shortwave trough around 3000 km to the north-northwest, a smaller upper-level shortwave immediately to the north, a low-level monsoon trough to the west-southwest, a weak tropical storm to the northeast, and a local perturbation in the immediate environment. It is found that WRF forecasts of Sinlaku exhibit high sensitivity, with large modifications to its track arising from the perturbation of each selected targets in the synoptic environment. The greatest improvement in the track forecast occurs by weakening the vorticity associated with each of two shortwaves to the north of Sinlaku, suggesting that either or both of the shortwaves may have been initialized too strongly in the model analysis, thereby contributing to an erroneous recurvature. For Ike, the perturbation locations include a large mid-latitude shortwave trough 2500 km to its north, an upper-level cutoff low to the east-northeast, a low-level shortwave trough to the northwest, a tropical storm in the East Pacific, and a local perturbation in the immediate environment. In contrast to Sinlaku, the perturbation of synoptic targets around Ike produces less sensitivity, likely due to the fact that Ike is not in a position of imminent recurvature. The only perturbation that leads to an accurate 4-day forecast of recurvature and landfall in North Texas is the strengthening of the large mid-latitude shortwave trough, suggesting that the shortwave may have been initialized too weakly in the operational models. Finally, a comparison of targets selected objectively by the Ensemble Transform Kalman Filter (ETKF) versus the above subjectively-chosen targets suggests that while the ETKF effectively indicates similar target regions to those selected subjectively, it may be less effective in ranking the relative sensitivities of those targets. Overall, it is found that the TC track is more sensitive to perturbations of larger amplitude and spatial scale, and less so to the distance between the perturbation and the TC, and sensitivity is confined to specific regions of the flow. The perturbation methodology employed here may be used to offer suggestions of locations in which extra high-density satellite data may be assimilated.

Spectral properties of global surface temperature and uncertainties of global climate sensitivity are explored in this work through the medium of Energy Balance Climate Models (EBCMs) and observational surface temperature data. In part I, a complete series of 2D time-dependent non-orthogonal eigenmodes of global surface temperature are analytically derived and their geographic patterns are presented. The amplitudes of these modes have temporal characteristics and present exponentially decaying patterns. Theoretically, if the energy balance model is forced by white noise forcing in time, the autocorrelation functions of the mode amplitudes should present the same exponentially decaying patterns. When observed surface temperature data are projected onto these theoretical modes, the autocorrelation time scales of the mode amplitudes exhibit similar exponential decaying patterns. These modes are believed to be useful for surface temperature studies and model intercomparison. In part II, an objective means of deriving the probability density function (PDF) of global climate sensitivity is investigated. The method constrains the PDF by its fit to the present climate in terms of surface temperature. We found that a wide range of parameter combinations, which corresponds to a broad range of the sensitivity, shows equally good fits to the present climate. It means that the uncertainties in global climate sensitivity are very difficult to eliminate if climate models are tuned to fit observations of surface temperature alone. The origin of the skewness of the PDF is found in very simple terms.

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Current understanding of sensitivity and sensation experienced across the ocular surface remains limited. This project explored the regional variation of corneal sensitivity and transducer function, interaction of sensory and autonomic nerves in the lacrimal functional unit, and the ocular surface sensitivity in Dry Eye and with silicone hydrogel (SH) lens wear. Experiments were undertaken, using Belmonte esthesiometer to deliver pneumatic mechanical, chemical and thermal stimuli and Cochet-Bonnet esthesiometer for tactile stimuli, to the cornea and conjunctiva. Psychophysical methods were used to determine the thresholds of stimulus detection, and the magnitude of sensations to suprathreshold stimulation was estimated assuming Steven’s power law. Additionally, tear secretion in response to corneal sensory input was determined by tear meniscus height measured using Optical Coherence Tomography. Sensitivity to pneumatic cool and mechanical stimuli varied slightly across the cornea while chemical sensitivity was not different between regions. The transducer function was also similar between central and peripheral cornea but different between stimulus modalities. In comparison, the reflex tearing response to suprathreshold stimuli was greater with central corneal stimulation. Also, corneal and conjunctival hypersensitivity was found in the dry eye symptomatic group, and it appeared to be associated with symptom severity, tear film stability and corneal epitheliopathy. Refitting with SH lenses after an initial no-lens interval led to increased conjunctival pneumatic mechanical sensitivity, while corneal tactile sensitivity showed a decrease. In addition, corneal staining induced by certain lens-solution combination appeared to be accompanied by increased corneal and conjunctival sensitivity. In conclusion, the position-invariant corneal sensitivity to pneumatic mechanical, chemical and thermal stimuli suggests that the distribution of human corneal sensory fibres may be more homogeneous than previously hypothesised. The mechanisms mediating the sensory aspect of corneal nociception may be similar across the cornea, while, perhaps due to the importance of the visual axis, the tear reflex response to central and peripheral cornea seems to be driven by different neural circuitry, perhaps at the higher levels of the sensory processing pathway. It appears that alteration in sensory processing of the ocular surface occurs in Dry Eye and accompanies SH lens-solution-induced corneal staining. This altered sensitivity seems to be more prominent in the conjunctiva than in the cornea.

Addressing issues with sensitivity and specificity in TBI assessment this study compared the performance on neuropsychological tests and results from qEEG assessment between a heterogeneous TBI (N=20) group and a matched normal control group (N=20). The TBI group was performed worse on all measures. Significant differences in performance were found in the domains of information processing speed and executive function. Effect sizes of these differences were large. This was also true for the amplitude of the qEEG parameter P3NoGo along with P3Go latency and theta power in the temporal and frontal lobes. Binary logistic regression revealed higher sensitivity and specificity when combining neuropsychological tests and qEEG parameters, suggesting qEEG parameters in  combination with neuropsychological tests to be good assets in TBI assessment.

Current understanding of sensitivity and sensation experienced across the ocular surface remains limited. This project explored the regional variation of corneal sensitivity and transducer function, interaction of sensory and autonomic nerves in the lacrimal functional unit, and the ocular surface sensitivity in Dry Eye and with silicone hydrogel (SH) lens wear. Experiments were undertaken, using Belmonte esthesiometer to deliver pneumatic mechanical, chemical and thermal stimuli and Cochet-Bonnet esthesiometer for tactile stimuli, to the cornea and conjunctiva. Psychophysical methods were used to determine the thresholds of stimulus detection, and the magnitude of sensations to suprathreshold stimulation was estimated assuming Steven’s power law. Additionally, tear secretion in response to corneal sensory input was determined by tear meniscus height measured using Optical Coherence Tomography. Sensitivity to pneumatic cool and mechanical stimuli varied slightly across the cornea while chemical sensitivity was not different between regions. The transducer function was also similar between central and peripheral cornea but different between stimulus modalities. In comparison, the reflex tearing response to suprathreshold stimuli was greater with central corneal stimulation. Also, corneal and conjunctival hypersensitivity was found in the dry eye symptomatic group, and it appeared to be associated with symptom severity, tear film stability and corneal epitheliopathy. Refitting with SH lenses after an initial no-lens interval led to increased conjunctival pneumatic mechanical sensitivity, while corneal tactile sensitivity showed a decrease. In addition, corneal staining induced by certain lens-solution combination appeared to be accompanied by increased corneal and conjunctival sensitivity. In conclusion, the position-invariant corneal sensitivity to pneumatic mechanical, chemical and thermal stimuli suggests that the distribution of human corneal sensory fibres may be more homogeneous than previously hypothesised. The mechanisms mediating the sensory aspect of corneal nociception may be similar across the cornea, while, perhaps due to the importance of the visual axis, the tear reflex response to central and peripheral cornea seems to be driven by different neural circuitry, perhaps at the higher levels of the sensory processing pathway. It appears that alteration in sensory processing of the ocular surface occurs in Dry Eye and accompanies SH lens-solution-induced corneal staining. This altered sensitivity seems to be more prominent in the conjunctiva than in the cornea.

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