Alcohol use in early adolescence is associated with numerous concurrent and future problems, including diagnosable alcohol use disorders. The trait of negative urgency, the tendency to act rashly when distressed, is an important predictor of alcohol-related dysfunction in youth and adults. The aim of this study was to test a model proposed by Cyders and Smith (2008) specifying a puberty-based developmental increase in negative urgency, which in turn predicts subsequent increases in early adolescent drinking. In a sample of 1,910 youth assessed semi- annually from spring of 5th grade through spring of 8th grade, we found support for this model. Pubertal onset was associated with both a mean increase and subsequent rises in negative urgency over time. Drinking frequency at any wave was predicted by prior wave assessments of drinking frequency, negative urgency, and pubertal onset. The slope of increase in drinking also increased as a function of pubertal onset. This model applied to negative urgency but not to other impulsivity-related traits. These findings highlight the importance of personality change in early adolescence as part of the risk matrix for early onset alcohol consumption.

Social cues, such as eye gaze and head-turns, can orient attention automatically. Social cue processing includes three sequential stages, namely cue selection, cue following and object recognition. In a typical social cueing task, a central face is presented and then attention is directed to potential target location by an eye gaze or head turn. In these paradigms, the standard finding is that despite the non-predictive nature of the cue (i.e., the target is as likely to appear at the validly cued location as the invalidly cued location), targets appearing at the validly cued location are detected and identified faster than targets presented at the invalidly cued location. The cueing effect starts to emerge at short cue-target stimulus onset asynchronies (SOA) (e.g., 105 ms) and diminishes at the long SOA (e.g., 1005 ms). However, because only one object was presented on one side of the center gaze cue in these paradigms, the social cueing effect could be interfered or abolished by the peripheral onset effect (i.e., the automatic orienting of attention by the abrupt appearance of a single object event). The goal of this dissertation was to develop a modified social cueing task to measure the temporal dynamics of social cue processing while eliminating the potential confounds from the peripheral onset effect. In the Cued Recognition Task, the peripheral onset effect is removed by simultaneously presenting a target and a distractor object following a non-predictive head-turn cue. Results from a series of experiments using the Cued Recognition Task showed that: (a) if the distractor was not presented on the opposite side of the target, the peripheral onset effect elicited by the target onset interfered with the social cueing effect elicited by the head-turn; (b) in the cued recognition paradigm, the reflexive attention orientation effect elicited by social cues could be inhibited at 0 ms of SOA, started to emerge at 105 ms of SOA, became stable at 300 and 600 ms of SOA and sustained at 1005 ms of SOA; (c) children with ASD showed equivalent magnitude of social cueing effect as TD controls, but they were slower across all conditions despite the fact that they were as fast as TD controls in object recognition. The Cued Recognition Model developed based on all the findings in this dissertation was described in order to provide an explicit explanation of how social cues influence everyday object recognition. / Graduate / 0633 / 0620 / 0623 / xubuyun@uvic.ca

Background: The causes of trends in asthma incidence are not fully understood. Objectives: This study examined trends in age and severity at asthma diagnosis for Ontario children. Methods: Multiple birth cohorts of Ontario children between 1992-2000 were created using health administrative data. Descriptive statistics and multivariable logistic regression examined changes in age and severity of asthma at diagnosis over time. Results: Age at asthma diagnosis decreased (p<0.0001) with a higher relative risk of asthma in children under age three (RR=1.5, 95% CI:1.47, 1.54). Predictors of asthma diagnosis before three included male sex, lower income quintile, and maternal asthma. ‘Severe onset asthma’ increased over time (p<0.0001), its predictors being male sex, lower income quintile, rural residence, comorbidity, low birth weight and age less than three. Conclusions: Observed trends in asthma incidence are not confined to mild disease and are secondary to variations in asthma rates in children under age three.

Background: The causes of trends in asthma incidence are not fully understood. Objectives: This study examined trends in age and severity at asthma diagnosis for Ontario children. Methods: Multiple birth cohorts of Ontario children between 1992-2000 were created using health administrative data. Descriptive statistics and multivariable logistic regression examined changes in age and severity of asthma at diagnosis over time. Results: Age at asthma diagnosis decreased (p<0.0001) with a higher relative risk of asthma in children under age three (RR=1.5, 95% CI:1.47, 1.54). Predictors of asthma diagnosis before three included male sex, lower income quintile, and maternal asthma. ‘Severe onset asthma’ increased over time (p<0.0001), its predictors being male sex, lower income quintile, rural residence, comorbidity, low birth weight and age less than three. Conclusions: Observed trends in asthma incidence are not confined to mild disease and are secondary to variations in asthma rates in children under age three.

This study explores the effects of manipulating vocal loudness and speech rate on voice onset time (VOT) in normal hearing children and two children with cochlear implants (CIs). 15 normal hearing participants and two participants with CIs produced all six stop consonants in the phrase “It’s a Cod again” while speaking normally, softly, loudly, slowly, and quickly. Consonants were grouped into voiced and voiceless categories for comparison. Results indicated that the group of normal hearing children produced longer VOTs for voiceless stops than voiced across all conditions. When speaking loudly or quickly, VOT values were shorter than at normal levels. When speaking softly or slowly, VOT values were longer than at normal levels. The two children with CIs performed in a similar manner to the normal hearing group; however, VOTs produced by the six-year old participant were consistently longer than those of the normal hearing group across all conditions. / Speech-Language Pathology

国立情報学研究所で電子化したコンテンツを使用している。

Liquid loading in gas wells is generally described as the inability of the well to lift the co-produced liquids up the tubing, which may ultimately kill the well. There is a lack of dedicated models that can mimic the transient features that are typical of liquid loading. Improved characterization of liquid loading in gas wells and enhanced prediction of future well performance can be achieved from the measurements and analyses resulting from this project. An experimental investigation was carried out to study the onset of liquid loading and the subsequent transient phenomena, using a large scale flow loop to visualize two-phase flow regimes, and to measure pressure and liquid holdup along a 42-m long vertical tube. From this investigation, it is possible to conclude that liquid loading should not be characterized based on onset criteria alone, and that it may not be a wellbore-only problem, as it would seem that the reservoir also plays a key role in determining if/when/how liquid loading manifests itself. Additionally, the results from the experimental campaign were used to compare the performance of different wellbore flow simulators. State-of-the-art simulators do not seem to fully capture the nature of liquid loading in vertical tubes. A simplified model is roposed here to evaluate the liquid transport during the transition from one flow regime to another, during the loading sequence.

This thesis reports voice onset time (VOT) of word–initial ejectives, implosives, and plain stops in Mopan, Itzaj, and Yukateko Maya. In this study, implosive bilabials and bilabial, alveolar, and velar ejectives and plain stops in word–initial position from Mopan, Itzaj, and Yukateko speakers were measured from the stop release to the onset of voicing of the following vowel, and results were compared to VOT of other languages with the same phonemes. All three languages have long average (negative) VOTs for implosives, contradicting Schumann–Galvez's claim that both Itzaj (2000) and Mopan (1997) have unaspirated rather than implosive voiced bilabials. Among other results, Yukateko had a very long VOT for plain velar stops, only slightly shorter than its velar ejective, and the average VOT of the plain bilabial voiceless stop in Mopan was actually longer than the corresponding ejective. Further study of these anomalies is warranted.

Doctor of Philosophy / Department of Mechanical and Nuclear Engineering / Hitesh Bindra / Helium-cooled, graphite moderated reactors have been considered for a future fleet of high temperature and high efficiency nuclear power plants. Nuclear-grade graphite is used in these reactors for structural strength, neutron moderation, heat transfer and, within a helium environment, has demonstrated stability at temperatures well above HTGR operating conditions. However, in the case of an air ingress accident, the oxygen introduced into the core can affect the integrity of the fuel graphite matrix. In this work a combination of computational models and mixed effects experiments were used to better understand the air ingress process and its potential effects on the heat removal capabilities of an HTGR design following an air-ingress accident. Contributions were made in the understanding of the air-ingress phenomenon, its potential effects on graphite, and in experimental and computational techniques. The first section of this thesis focuses on experimental and computational studies that were undertaken to further the understanding of the Onset of Natural Convection (ONC) phenomenon expected to occur inside of an HTGR following an air ingress accident. The effects of two newly identified factors on ONC – i.e., the existence of the large volume of stagnate helium in a reactor's upper plenum, and the possibility of an upper head leak – were investigated. Mixed-effects experimental studies were performed to determine the changes induced in nuclear grade graphite exposed to high-temperature, oxidizing flow of varying flow rates. Under all scenarios, the thermal diffusivity of the graphite test samples was shown to increase. Thermal conductivity changes due to oxidation were found to be minor in the tested graphite samples – especially compared to the large drop in thermal conductivity the graphite is expected to experience due to irradiation. Oxidation was also found to increase the graphite's surface roughness and create a thin outer layer of decreased density. The effects of thermal contacts on the passive cooling ability of an HTGR were experimentally investigated. Conduction cool down experiments were performed on assemblies consisting of a number of rods packed into a cylindrical tube. Experimental conditions were then modeled using several different methodologies, including a novel graph laplacian approach, and their results compared to the experimentally obtained temperature data. Although the graph laplacian technique shows great promise, the 2–D Finite Element Model (FEM) provided the best results. Finally, a case study was constructed in which a section of a pebble bed reactor consisting of a number of randomly packed, spherical fuel particles was modeled using the validated FEM technique. Using a discrete elements model, a stable, randomly packed geometry was created to represent the pebble bed. A conduction cool down scenario was modeled and the results from the FEM model were compared to best possible results obtainable from a more traditional, homogeneous 1–D approximation. When the graphite in the bed was modeled as both oxided and irradiated, the homogeneous method mispredicted the maximum temperature given by the 3–D, FEM model by more than 100°C.

OBJECTIVES: 1) To measure the prevalence of precipitating events in pediatric chronic pain patients and 2) to compare pain and functional disability outcomes at evaluation and 4-month follow-up by presence and type of precipitating event. METHODS: Precipitating events (e.g., injury) were coded from the medical record for 401 youth (6-19) who presented to a tertiary care chronic pain clinic. Four-month follow-up disability and pain were collected for 187 patients. In addition to frequency of events, we examined differences in pain and disability measures by event type at evaluation and follow-up using multiple statistical analysis strategies. RESULTS: Two-thirds of patients had a precipitating event prior to pain onset. Injury was the most common (55%), followed by chronic disease (23%), infection/illness (12.8%), and surgery (7.5%). Patients whose pain was triggered by injury reported the highest average pain levels, F(3, 340)=2.67, p<.05 and functional disability, F(3, 295)=3.54, p<.05. There were multiple cases of event groups that had significantly different baseline and follow-up psychological measures when compared to the rest of the patient population. Trajectories of pain and disability did not differ between patients with and without a precipitating event. Patients with injuries reported greater improvement in functional disability at follow-up (time x injury) F(1, 183)=4.88, p<.05 whereas patients with chronic disease reported less improvement in disability (time x chronic disease), F(1, 183)=5.49, p<.05. No other interactions were significant for disability or pain. CONCLUSIONS: A majority of patients had experienced some form of precipitating event prior to their pain onset, and the presence of a precipitating event had varied effects on the treatment outcomes of patients at four-month follow-up. Although patients with injuries presented with greater disability and pain, they had significantly more improvement, while chronic disease patients were less likely to improve in terms of functional disability. Type of precipitating event appears to be associated with treatment response and can inform clinical prognoses.