>Magister Scientiae - MSc / Somerset West and Strand in the Western Cape, South Africa, were developed on the Lourens River floodplain. This hardened the catchment and reduced the capacity of the river to transport and store floodwaters. The result was recurrent flooding of residential and industrial areas and a fear that this could lead to loss of human life. In response to these concerns, the City of Cape Town implemented flood alleviation measures with a ‘soft’ engineering approach that incorporated geomorphological and ecological principles into their design. This was one of the first engineer/ecologist collaborations in South Africa, which attempted to make better decisions for the river ecosystem within the constraints imposed on it by urban development; and in so doing to create a self-sustaining river that requires little ongoing manipulation. The aim of this dissertation was to assess the extent to which ecological considerations were incorporated into the flood alleviation works on the Lourens River and whether this improved physical habitat and the diversity of riverine biota. Physical habitat was mapped from 1:50 000 topographic maps and aerial imagery in a GIS, and cross-sectional profiles, diversity of hydraulic biotopes and subtsrate composition were surveyed in the field.

京都大学 / 0048 / 新制・課程博士 / 博士(エネルギー科学) / 甲第20484号 / エネ博第353号 / 新制||エネ||70(附属図書館) / 京都大学大学院エネルギー科学研究科エネルギー変換科学専攻 / (主査)教授 木村 晃彦, 教授 星出 敏彦, 教授 今谷 勝次 / 学位規則第4条第1項該当 / Doctor of Energy Science / Kyoto University / DFAM

京都大学 / 0048 / 新制・課程博士 / 博士(エネルギー科学) / 甲第21434号 / エネ博第376号 / 京都大学大学院エネルギー科学研究科エネルギー変換科学専攻 / (主査)教授 木村 晃彦, 教授 星出 敏彦, 教授 今谷 勝次 / 学位規則第4条第1項該当 / Doctor of Energy Science / Kyoto University / DGAM

Background. The pandemic outbreak commenced a large migration of employees from all kinds of industries from previously working in an industrial or office environment to working from home. The remote migration allowed many kinds of work to continue as usual even during a pandemic. A common tool to use when working remotely is a Virtual Private Network (VPN) that allows remote workers to connect to a Local Area Network (LAN) at the company office. Which further grants the remote worker secure access to organizations resources and services. This remote work setup has increased the complexity of the company networks and therefore also magnified the attack surface for cyber threat actors. Objectives. The objective of this thesis involves studying how the VPN security landscape looks like after the pandemic outbreak. Answering questions related to how the attacks on VPNs changed in numbers, which techniques and tactics the adversaries use against VPN security systems and then, for the thesis to “bite itself in the tail”, investigate countermeasures that can further improve the VPN security. Methods. One research method is used in two different fashions to satisfy the objectives. The research method is a Systematic Literature Review (SLR). The first SLR involves research on secondary data reports, published by cyber companies, cyber experts, or cyber departments of large IT organizations. The second SLR involves qualitative research by reading research papers related to how VPN security can be improved.  Results. In direct consequence of the remote work migration the number of VPN attacks have increased. The vulnerabilities found in VPN systems have been used extensively where even national cybersecurity organizations have urged companies to patch systems. Advanced Persistent Threat (APT) groups have leveraged the published vulnerabilities by exploiting unpatched systems and established persistent and defense-evasive access to networks that remote workers connect to with VPNs. To counter these threats and to harden the VPN systems and private networks, there are recommendations involving countermeasures such as enforced Multi Factor Authentication (MFA) and adding multiple defense layers in private networks. Conclusions. This thesis concludes that the covid-19 pandemic outbreak was the root cause to the huge remote work transition which in turn caught 99% of all organizations and home networks off guard when it comes to VPN security for remote workers. This caused huge opportunities for threat actors and state sponsored adversaries which is the main reason for the increased number of cyberattacks post covid-19 outbreak. Cyber adversaries exploited every vulnerability, bug, and misconfiguration they could find by conducting tactics and techniques like phishing, ransomware, exploiting VPN vulnerabilities and performing DDoS-attacks to the best of their abilities. This caused huge damage to organizations, governments, healthcare, and militaries all around the world. In order to increase VPN security for remote workers, small, medium or big organizations, we have developed a new VPN hardening framework.

Several native species of Lauraceae (e.g. sassafras) in the southeastern United States are being eradicated by laurel wilt disease. Laurel wilt is caused by a highly invasive and cryptic ambrosia beetle, Xyleborus glabratus, and its fungal symbiont. The symbiont pathogen is spread during colonization of native Lauraceae. Xyleborus glabratus and the pathogen are remarkably effective at colonizing and killing healthy populations of Lauraceae in a brief time period. Control methods have been unable to slow the spread of laurel wilt disease and X. glabratus populations have been spreading into northern latitudes. Presently, cold temperatures may be the only factor limiting establishment of the beetle in interior populations of sassafras. Empirically derived physiological data from this study were combined with climatic, microhabitat, and host data to model the invasive potential/hazard rate of X. glabratus and laurel wilt in sassafras forests of the United States. Sharing this model data will help land managers, forest health specialists, urban foresters, and landowners make informed proactive management decisions regarding laurel wilt disease.

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Temperature represents a major driving force in biology as it influences essential functions across multiple levels of biological organization. The role of temperature is especially important for ectothermic animals, whose biotic processes are dependent on both body and environmental temperature. Assessing the relationship between temperature and organismal performance represents an important research direction as temperatures continue to warm under anthropogenic climate change. Chapters two and three are focused on a recently colonized population of the invasive Mediterranean House Geckos at the northern edge of their invasion front. These chapters examine the ecological and physiological factors that enable these lizards to persist in a cooler and more temperate environment than their native range. The thermal breadth of a reptile greatly influences its ability to tolerate a thermally variable environment, particularly when environmental options are limited for behavioral thermoregulation. These chapters explore the thermal performance of this species, and the results show that the eurythermality of these geckos promotes their rapid colonization of novel environments despite experiencing prolonged periods of cool temperatures. Chapters four, five, and six, by contrast, shift focus to larval amphibians to explore the constraints and factors underlying plasticity in acclimation to temperature extremes. As habitats continue to warm with climate change, ectotherms with limited capacity to thermoregulate, such as larval amphibians in shallow ponds, will be under a heightened threat of heat stress and mortality. Resultantly, identifying different factors that can increase organismal heat tolerance would reduce the risk of overheating and promote survival. Chapters four, five, and six explore this topic by measuring the critical thermal maximum (CTmax) of larval wood frogs. Chapter four focuses on the tradeoff between basal CTmax and plasticity of CTmax and its consequences for how a larval anuran responds to an acute heat shock. Chapter five examines the role a viral pathogen, ranavirus, has on larval CTmax. Surprisingly, a lethal dose of ranavirus did not reduce CTmax which goes against the common pattern of pathogenic infections lowering host heat tolerance. Lastly, chapter six explores the relationship between the gut microbiota and host CTmax with a particular focus on cross-species microbiota transplants. In line with our prediction, transplanting the gut microbiota of a heat-tolerant donor species promoted greater CTmax in the heat-sensitive recipient species.

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