Thesis (Ph. D.)--University of Hong Kong, 2007. / Also available online.

A well-developed body of literature has established the deleterious effects of chronic stress on children’s cognitive development. However, there has been almost no research examining the impact of acutely stressful experiences on children’s cognitive performance. This is surprising given evidence in adults that acute stress alters cognition and plausible links between stress system reactivity and cognitive function. Extending such temporally precise acute stress research to the childhood age range may be valuable for identifying new ways to support children’s function across contexts and elucidating how repetitive stress leads to pervasive alterations in cognitive development. The first chapter reviews the theorized links between acute stress and subsequent cognitive vulnerability as well as the possible role of biological stress systems (i.e. autonomic nervous system, ANS; Hypothalamic Pituitary Adrenal Axis, HPA) in supporting cognitive function. The second chapter serves to validate an in-laboratory stressor paradigm (modified from previous research) as effective at inducing biological reactivity across HPA and ANS systems. Validating this ‘matching task’ was important given the challenges of eliciting stress system reactivity in the early childhood age range. In the third chapter, the relevance of stress system reactivity to children’s concurrent performance on a cognitively challenging matching task was examined. This study was conducted to establish profiles of HPA and ANS (parasympathetic, PNS, and sympathetic, SNS, branches) associated with adaptive cognitive function, under stress. Results indicated that indices of both HPA and PNS reactivity were predictive of cognitive performance, with different results by gender. Finally, we examined the extent to which acute stress (versus control) altered children’s subsequent selective attention and inhibitory control performance. Largely consistent with the adult literature employing Go/No-Go tasks, stress-exposed children experienced selective attention impairment, but no inhibitory control change. Amongst stress-exposed children, higher maternal stress predicted selective attention impairment, which highlights the relevance of early caregiving to children’s stress regulatory ability. In contrary to hypotheses, this effect was not mediated by HPA or ANS reactivity. The final chapter concludes with a discussion of broad implications, limitations, and future directions for acute stress research in early childhood. / 10000-01-01

Concrete, a composite material consisting of aggregates bound together with cement paste, is the most widely used construction material. Concrete is relatively cheap, very versatile and has excellent compressive strength. However, its tensile strength is limited and for this reason steel rebars are often added to create reinforced concrete (RC). Cracking inevitably occurs in all RC materials and associated structures due to a variety of mechanical and environmental actions. The generation of tiny microcracks within concrete facilitates the flow of potentially aggressive fluids that can corrode the embedded steel rebars and, in extreme cases, lead to premature structural failure. Concrete, along with all cement-based materials, does possess some inherent self-healing capacity and is able to heal certain-size cracks autogenously. This self-healing capability is very limited and therefore researchers have attempted to improve upon it by using a variety of techniques. In particular, the use of engineered additions for autonomic self-healing has gained significant interest in the past two decades. An example is the addition of microcapsules that disperse throughout the hardened material subsequently providing reservoirs of healing agents. When cracks arise within the material, they rupture the embedded microcapsules causing a release of their contents into the crack volume. The released material then reacts to provide filling, sealing and healing of the crack. The primary aim of this research project was to investigate the autonomic self-healing performance of concrete containing microencapsulated sodium silicate. The effect of microcapsule addition on the fresh, hardened and self-healing properties of cement, mortar and concrete were all explored. Self-healing was monitored using a variety of techniques and results reveal the increased self-healing ability of microcapsule-containing cementitious materials as well as the efficacy of sodium silicate as a healing agent. Furthermore, the self-healing concrete field trial displays the great potential for microcapsules to be incorporated into large-scale self-healing concrete applications.

Ninety college Ss were first classically "conditioned" to color names and subsequently transferred to a dichotic listening task requiring shadowing of a five-minute prose passage. Embedded in the non-attended channel were previously shock-associated color words. In one condition (same pitch) both the shadowed and non-attended material was read by the same speaker. In the second condition (different pitch) the shadowed and non-attended channels were read by different speakers. Within conditions right/left ear of presentation of shadowing was factorially arranged. The dependent measure was phasic skin resistance changes in the non-attended channel to previously shock-associated stimuli. Autonomic responding was not affected by pitch characteristics. Ear of presentation showed a strong effect; autonomic responding to non-attended stimuli was enhanced by left ear presentation. The interaction of pitch by ear of presentation was significant; a left ear advantage was favored in the same pitch condition. Shadowing efficiency was not impaired at the time of responding to non-attended material nor was shadowing performance altered by pitch distinctions or ear of presentation. The above findings are discussed in terms of the Deutsch and Deutsch and Treisman theories of selective attention. / Arts, Faculty of / Psychology, Department of / Graduate

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Supervisory control and data acquisition systems are extensively used in the critical infrastructure domain for controlling and managing large-scale industrial applications. This thesis presents a security management structure developed to protect ICS networks from security intrusions. This structure is formed by a combination of several modules for monitoring system-utilization parameters, data processing, detection of known attacks, forensic analysis to support against unknown attacks, estimation of control system-specific variables, and launch of appropriate protection methods. The best protection method to launch in case of an attack is chosen by a multi-criteria analysis controller based on operational costs and efficiency. A time-series ARIMA model is utilized to estimate the future state of the system and to protect it against cyber intrusions. Signature and performance based detection techniques assist in real-time identification of attacks with little or no human intervention. Simulation results for Scanning, Denial of Service and Injection attacks are provided.

京都大学 / 新制・課程博士 / 博士(人間健康科学) / 甲第24543号 / 人健博第114号 / 新制||人健||8(附属図書館) / 京都大学大学院医学研究科人間健康科学系専攻 / (主査)教授 黒木 裕士, 教授 稲富 宏之, 教授 村井 俊哉 / 学位規則第4条第1項該当 / Doctor of Human Health Sciences / Kyoto University / DFAM

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