Polygenic adaptation in response to selection on quantitative traits is thought to be ubiquitous in humans and other species, yet this mode of adaptation remains poorly understood. We investigate the dynamics of this process, assuming that a sudden change in environment shifts the optimal value of a highly polygenic quantitative trait. We find that when the shift is not too large relative to the genetic variance in the trait and this variance arises from segregating loci with small to moderate effect sizes (defined in terms of the selection acting on them before the shift), the mean phenotype's approach to the new optimum is well approximated by a rapid exponential process first described by Lande (1976). In contrast, when the shift is larger or large effect loci contribute substantially to genetic variance, the initially rapid approach is succeeded by a much slower one. In either case, the underlying changes to allele frequencies exhibit different behaviors short and long-term. Over the short term, strong directional selection on the trait introduces small differences between the frequencies of minor alleles whose effects are aligned with the shift in optimum versus those with effects in the opposite direction. The phenotypic effects of these differences are dominated by contributions from alleles with moderate and large effects, and cumulatively, these effects push the mean phenotype close to the new optimum. Over the longer term, weak directional selection on the trait can amplify the expected frequency differences between opposite alleles; however, since the mean phenotype is close to the new optimum, alleles are mainly affected by stabilizing selection on the trait. Consequently, the frequency differences between opposite alleles translate into small differences in their probabilities of fixation, and the short-term phenotypic contributions of large effect alleles are largely supplanted by contributions of fixed, moderate ones.

This study aims to understand tourism carrying capacities of diving sites in Hong Kong and Malaysia. Specifically, ecological, psychological and social carrying capacities were assessed. Methodology involved photo quadrat transect survey, questionnaire survey and visual experiment survey. Over a period of two calendar years (2013 and 2014), 13, 12 and 9 photo quadrat transect surveys were conducted in Sharp Island, Tsim Chau and Mabul Island (Ray Point and Eel Garden) respectively to provide data for ecological carrying capacity assessment. In addition, 455 and 342 questionnaires were collected in Hong Kong and Mabul Island respectively to assess divers' satisfaction with diving attributes of the respective dive sites. Regarding social carrying capacity assessment, 247 and 158 visual experiment questionnaires were collected to assess crowding as perceived by divers in the two sites.;The ecological carrying capacity of Sharp Island lies between 172 and (less than) 825 divers every quarter in the absence of better solutions. At Tsim Chau, diving activity is not the most important factor in influencing the coverage of sea anemone. In addition, the use of additional (subjective) data was necessary to define the ecological carrying capacity of Tsim Chau and possibly Sharp Island. In Mabul Island, the results show that the ecological carrying capacity is about 16800-17200 divers per year at Ray Point and about 15600-16800 divers per year at Eel Garden. Based on the findings, it is likely that the usage of the diving sites on Sharp Island, Ray Point and Eel Garden have already exceeded the social carrying capacity. Regarding the psychological carrying capacity, this study found that the most important factor that influences divers' willingness to return to Hong Kong diving sites is "the quality of corals". In Mabul Island, the most important factor is "the value for money of Mabul diving". However, no studied diving sites have exceeded their psychological carrying capacities. Regarding the social carrying capacity, on both Hong Kong and Mabul Island diving sites, the "number of divers" was found to be the most influential factor for divers' perceived crowding. In Hong Kong, divers' begin to feel unacceptably crowded if 78̃ divers are visible to them at one time whereas in Mabul Island, divers would start to feel unacceptably crowded if 8 to 9 divers were visible to them at one time. Based on this, it is likely that the usage of both Hong Kong and Mabul Island diving sites have already exceeded the social carrying capacity.;With the increasing popularity of diving in recent years, divers and diving trips operators around the world need to be aware of divers' impact on coral reef, divers' satisfaction and underwater crowding problem. Finally, a series of management and policy measures to minimise the impact of diving activity on coral, improve divers' satisfaction and mitigate divers' crowding perception in underwater environment are proposed for sustainable use of diving sites in Hong Kong and Mabul Island.

Magister Psychologiae - MPsych / Substance use and abuse has been a persistent challenge facing many communities around the world. In more recent times there has been particular focus on the gradual, yet alarming increase in the use and/or abuse of substance use among the students who are currently enrolled in institutions of higher learning. On the strength of such findings, relevant stakeholders and policy makers have since demarcated university students as being one of the most high-risk groups within a society when it comes to substance use and abuse. While substantial research has been done on the issue of alcohol use among adolescents on both a local and global scale, very little is known about the prevalence of substance use among university students in South Africa.

Across the academic sphere, much research has been conducted into the development of water-sensitive elements to address issues around urban water management. However, these elements are commonly investigated in isolation, with little consideration for initiatives from other disciplines that may support their success. This research aims to demonstrate the value that an architect may bring in incorporating ideas drawn from various disciplines to create a water- sensitive design solution with multiple ecosystem benefits, taking into account the human experience of space and place-making. In doing so, the design demonstrates that a water-sensitive building is aesthetically pleasing, viable and achievable. The feasibility of water-sensitive designs has been noted as a focus area by the South African Water Research Commission; one which is particularly pertinent in our present water-scarce environment in South Africa. This applied study is based on a previous Master of Architecture (Professional) dissertation building design, which is used as the unit of analysis. The building focuses on restoring the quality of water in the Liesbeek River in Cape Town using passive filtration methods. The objective of this study is to gain new insights into the design process and planning of water-sensitive architectural buildings, which assists in understanding when collaborating across disciplines. The research is guided by Deep Ecology, phenomenology and Ecological Urbanism. Research by Design is used as the method of the study, in which different design iterations based on the raw data of the original building are investigated and analysed, as well as evaluated by specialists from various disciplines in order to create a best-fit design solution. The revised building takes into account the practical, site-specific and architectural qualities of a water-sensitive design to create a people-centred building that incorporates ecological and engineering demands in greater detail. Key outcomes of the study include a typical design process for a WSAD and architectural guidelines for water-sensitive buildings, grounded in the diverse values of water and its relationship to people and nature. The dissertation aims to contribute to the academic discourse around water-sensitive design. Further, the guidelines developed may be used to inform the design of conventional buildings.

Philosophiae Doctor - PhD / The increasing evidence of chemicals of emerging concern (CECs) in water bodies is causing major concern around the world because of their toxicological effects upon humans and aquatic organisms. The release of wastewater to the aquatic environment is most likely to introduce some trace levels of organic contaminants, some of which may be toxic, carcinogenic, or endocrine disruptors, as well as, persistent in the environment. These compounds are often persistent but not regularly monitored because they are mostly still excluded from environmental legislation. Their fate and persistence in the environment are not well understood. / 2022-02-24

No description available.

The purpose of this study is to qualitatively explore how physical activity engagement is initiated and maintained in adult patients with congenital heart disease (ACHD). The rising number of aging ACHD patients means they could need more healthcare resources for lifelong treatments to maintain their health. One cost-efficient and natural way to maintain the health of ACHD patients is through physical activity participation. Unfortunately, though, ACHD patients tend to be sedentary, and research has yet to adequately explore the factors influencing physical activity behaviour within this population. To gain a better understanding on this topic, this study combines the transtheoretical model and social ecological model to uncover factors influencing physical activity behaviour in ACHD patients who are at different levels of motivation. This study utilizes a qualitative research design: over six months, 27 participants took part in three individual semi-structured interviews for a total of 78 interviews (three participants did not complete all three interviews). The study revealed that several factors influenced physical activity behaviour in ACHD patients at different stages of motivation. In addition, findings on the characteristics of participants in each stage, meanings of physical activity and strategies for promoting physical activity for ACHD patients are also presented, as well as practical findings (i.e., physical activity program for ACHD patients). This thesis is important for healthcare professionals as it could facilitate the development of stage-specific interventions designed to increase physical activity behaviour in ACHD patients.

The 178,000-acre Grassland Ecological Area in California’s San Joaquin Valley is managed to provide overwintering habitat to waterfowl on the Pacific Flyway. The major management activity is the fall flooding and spring drawdown of wetlands, timed to optimize the availability of forage vegetation and invertebrates for ducks and shorebirds. Wetland drainage contains salt, boron, and trace elements that are, in part, derived from imported surface water but also concentrate during storage in the wetland impoundments. The spring drawdown drainage contributes to occasional water quality violations in the San Joaquin River (SJR) during dry years. Compliance with water quality objectives may be improved by delaying the traditional wetland drawdown period approximately one month to coincide with high SJR salt assimilative capacity during mid-March to mid- April when reservoir releases are increased to aid salmon migration. However, this delayed drawdown may affect the quality and quantity of wetland vegetative forage, increase wetland soil salinity, and possibly alter the concentrations of algae, invertebrates, and pollutants in the wetlands. In the research presented herein, initial data were collected on the effects of delayed drawdown on algae, invertebrates, and wetland water quality. The experimental sites chosen were three pairs of matched wetland basins (20-100 acres each) that are part of the larger Modified Hydrology Study being conducted in the Grassland Ecological Area. For each pair, one wetland was managed with a traditional March drawdown; while for the second wetland, drawdown was delayed approximately one month to coincide with the period of high SJR assimilative capacity. During the second year of the study, two drainage sites were sampled to characterize drainage flowing to the SJR from an aggregated wetland area. Soil and water column samples were collected during the flooded periods at the inlets, outlets, and along transects within the wetlands. Water quality analyses included total/volatile suspended solids, conductivity, nitrogen (NH4 +, NO2⁻+NO3⁻, organic), phosphorus (total, PO4 3-), organic carbon, alkalinity, turbidity, temperature, and pH. Planktonic and benthic invertebrates were identified and enumerated. Data were collected between February and April in 2007 and again in 2008. Identified phytoplankton were predominantly chlorophytes and diatoms. Zooplankton that feed on phytoplankton were found in abundance and consisted mostly of Cladocera. Benthic invertebrate densities were also measured to help explain the differences in algal concentrations between ponds. Benthic invertebrates were found to be predominantly Chironomidae. Seasonal loads of volatile suspended solids, total dissolved solids, and total organic carbon were estimated at the two aggregate drainage sites and at one delayed drawdown wetland during the 2008 season. For volatile suspended solids, the discharged load was 1500 lbs at the Buttonwillow drainage site, 2500 lbs at the Los Banos 38 drainage site, and upstream of those sites, 770 lbs were discharged from the Mud Slough 4b wetland. For total dissolved solids, the discharged load was 290 tons, 520 tons, and 26 tons, respectively, for the same locations. Of the factors potentially limiting phytoplankton concentrations, invertebrate grazing was likely the most important. Nutrients were not limiting in either the traditional or modified wetlands, as indicated by sufficient N and P content in the algae biomass. Likewise, inorganic C was not limiting, as indicated by pH (most <9.0 pH). Sunlight intensity was not significantly attenuated by water depth or turbidity, and thus light limitation was not indicated.

Nature reserves in the City of Tshwane are under threat from ecological and historically significant decay due to the less defined nature of these landscapes. Architecture in form, function and technology can be developed in the in-between of nature and urban to act as conservator for these nature reserves. Utilizing the natural resources of nature to produce products for the urban dweller within a space that conserves the historical protective layers of the site. The space of interaction between nature and urban becomes the conservator, acting as active protector in terms of sustainable production, education and urban dweller interaction with the nature reserve and its continuous history of protection. / Natuurreservate in die stad Tshwane word bedreig deur ekologiese en historiese betekenisverval weens die minder gedefinieerde aard van hierdie landskappe. Argitektuur in vorm, funksie en tegnologie kan ontwikkel word in die tussen ruimte van natuur en stedelike gebiede om as natuurbewaarder vir hierdie natuurreservate op te tree. Die natuurlike hulpbronne van die natuur kan gebruik word om produkte vir die stedelike inwoner te produseer binne ‘n ruimte wat die historiese beskermende lae van die terrein laat voortduur. Die ruimte van interaksie tussen natuur en stedelike word die bewaarder, wat optree as ‘n aktiewe beskermer in terme van volhoubare produksie, opvoeding en stedelike inwoner interaksie met die natuurreservaat en sy voortgesette geskiedenis van beskerming. / Mini Dissertation (MArch(Prof))--University of Pretoria, 2018. / Architecture / MArch(Prof) / Unrestricted

The thesis is a part of an ongoing research on taxonomy, ecology, and the distribution of epiphytic bryophytes particularly within the Orthotrichaceae family, based on collected bryofloristic records. The database now contains 6500 records. I have analysed interspecific differences in habitat preferences between species, namely their associations with particular phorophytes, pH of phorophyte bark, altitude, and the position on the phorophyte. Individual species differed in their occurrence according to altitude, phorophyte, and pH, though altitude was the most important factor. All analysed species have been shown to represent obligate epiphytes. Some species reveal a tendency to occur preferrentially on northern or western side of the phorophyte, but this tendency is not by any means universal. I discuss these findings in the context of the knowledge of species autecology and current changes in their distribution.