Graduation date:1979

Contamination of surface and ground water has emerged as one of the most important environmental issues in developed and developing countries. Bioremediation of groundwater takes advantage of bacteria present in the environment to transform toxic compounds to non-toxic metabolites. This biotechnology holds the potential for fast, inexpensive, and effective water decontamination. However, it is still poorly understood and usually not fully controlled due to the lack of information describing the natural phenomena involved. Therefore, a better understanding of the phenomena involved during bioremediation of groundwater could help in the design and implementation of more efficient technologies. The main objective of the present research is to assess how pore-scale physical factors, such as pore-scale velocity, affect the degradation potential of contaminants during transport in groundwater. The target chemicals studied were chlorinated ethenes because they are commonly found in contaminated groundwater sites. To achieve the research objective, the following were employed: a mathematical model that links pore scale processes to the macro-scale representation of contaminant transport; development of numerical tools to solve the mathematical model; and experimental elucidation of the influence of pore-scale flow velocity on the biodegradation of contaminants using column experiments. Results from the mathematical model and experiments were used to elucidate the inter-relationship between physical and biological phenomena at the micro scale. The influence of flow velocity through the porous media (a physical factor) on the biological structure (microbial community in the porous media) was assessed. The results of this investigation contribute to the bioremediation of contaminated groundwater understanding with new insights on the importance of physical transport factors on the biodegradation potential. For example, flow velocity is shown to have an important effect on the degradation potential of chlorinated ethenes. Additionally, the mathematical model and numerical tools have potential application to many other reactive transport problems, including: adsorption onto activated carbon, reaction in packed beds of catalyst, chemical transport in streambeds, and separation in chromatographic columns.

Contamination of surface and ground water has emerged as one of the most important environmental issues in developed and developing countries. Bioremediation of groundwater takes advantage of bacteria present in the environment to transform toxic compounds to non-toxic metabolites. This biotechnology holds the potential for fast, inexpensive, and effective water decontamination. However, it is still poorly understood and usually not fully controlled due to the lack of information describing the natural phenomena involved. Therefore, a better understanding of the phenomena involved during bioremediation of groundwater could help in the design and implementation of more efficient technologies. The main objective of the present research is to assess how pore-scale physical factors, such as pore-scale velocity, affect the degradation potential of contaminants during transport in groundwater. The target chemicals studied were chlorinated ethenes because they are commonly found in contaminated groundwater sites. To achieve the research objective, the following were employed: a mathematical model that links pore scale processes to the macro-scale representation of contaminant transport; development of numerical tools to solve the mathematical model; and experimental elucidation of the influence of pore-scale flow velocity on the biodegradation of contaminants using column experiments. Results from the mathematical model and experiments were used to elucidate the inter-relationship between physical and biological phenomena at the micro scale. The influence of flow velocity through the porous media (a physical factor) on the biological structure (microbial community in the porous media) was assessed. The results of this investigation contribute to the bioremediation of contaminated groundwater understanding with new insights on the importance of physical transport factors on the biodegradation potential. For example, flow velocity is shown to have an important effect on the degradation potential of chlorinated ethenes. Additionally, the mathematical model and numerical tools have potential application to many other reactive transport problems, including: adsorption onto activated carbon, reaction in packed beds of catalyst, chemical transport in streambeds, and separation in chromatographic columns.

Thesis (Ph. D.)--Johns Hopkins University. / Vita. Published also as no. 3 of the Johns Hopkins studies in philosophy and psychology, and as The Psychological review, v. 11, no. 4, whole no. 47.

Department of Biochemistry in HKU has been planning to implement virtual lab blended learning solution into their experiment related courses. Based on selected case, the study investigated whether the virtual lab would arouse more learning interests and improve the learning gains for students. Also, the study concluded some useful suggestions for virtual lab blended learning and generalized a few guidelines for instructional design on virtual lab. The study adopted mixed research methods with combination of quantitative and qualitative studies. With the ADDIE instructional design model, the researcher and his advisor constructed initial virtual lab in Second Life virtual design platform for selected class based on the teacher’s suggestions and course arrangements. Then chosen students participated in demonstration classes organized in two groups, one with Second Life virtual lab for teaching and learning (SL Group) while the other without(Non-SL Group). The students were given same quiz in the Moodle LMS to compare their basic academic learning outcomes. Meanwhile, researcher with other three observers recorded students’ class performances for each learning tasks by camera and observation forms. At the end of the class, surveys were delivered to them to collect their perceptions about learning with Second Life virtual lab and their suggestions for virtual lab design. The research findings indicate that students can basically accept the virtual lab blended learning solution. Compared with Non-SL Group, students from SL Group achieved higher average scores in academic quiz with more passions in class learning. They were more active in joining class activities and discussions in small team with more interactions between team members. However, they were also troubled by the use of virtual lab because of unclear instruction, technical problems, virtual learning activities design and virtual lab system issues. The paper argued the way of integrating the virtual lab into experiment courses in biochemistry teaching and learning. It discussed the proper ways to design the blended virtual lab learning system for learning purpose and questioned the virtual technologies used for learning design. Finally, it concluded some principles and guideline framework for blended virtual lab design and development in biochemistry teaching and learning, which can be also applied for similar design and development in health and medical education. / published_or_final_version / Education / Master / Master of Science in Information Technology in Education

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Plants collected in Wisconsin during September, 1970 were identified as P. ramosissimum and P. tenue according to the taxonomic characters established by Styles for European species of genus Polygonum and adapted for the North American species fo this genus by Mertens and Raven. The chromosome number for these two plants were determined to be 2n=60 for P. ramosissimum and 2n=30 or 32 for P. tenue. These counts were compared with chromosome numbers for Polygonum species for all of which the haploid count is either twenty or thirty. Chromatographic analysis of free amino acids and secondary substances further suggests that P. ramosissimum is properly assigned to section Polygonum while P. tenue should be placed in some other section of genus Polyyonum.

Although numerous hazard models exist to assess possible ash fallout from explosive volcanic eruptions around the world, these models frequently neglect to consider ash aggregation or use a simple percent proxy to represent aggregation, without considering the varying processes at work throughout the volcanic flow. Eruption dynamics are sensitive to ash aggregation, and ash aggregates are commonly found in eruptive deposits, yet few experiments have been conducted on aggregation phenomena using natural materials. In this work, experiments were developed to produce both probabilistic and process-based relationships for the efficiency of ash aggregation with respect particle size, collision kinetic energy, atmospheric water vapor and residence time. A synthetic ash proxy, ballotini, and ash from the 2006 eruption of Tungurahua, Ecuador, and the 1980 eruption of Mount St. Helens, WA, were examined for their aggregation potential. Two aggregation regimes, wet and dry, were identified based on their potential for aggregation. The wet flow regime occurs when particles are circulated in high relative humidity environments long enough to develop a water layer with a thickness that exceeds the particle roughness scale. Hydrodynamic forces control aggregation in the wet flow regime. The dry flow regime includes particles in low relative humidity environments as well as those that circulate too briefly in high humidity environments to fully develop a water layer. Electrostatic forces control aggregation in the dry flow regime. Aggregation efficiency in both regimes was dominantly controlled by collision kinetic energy; however, this effect is significantly dampened in the wet flow regime. Equations governing the relationships between aggregation efficiency, collision kinetic energy and the related forcings in the wet or dry flow regimes have been developed for implementation into large-scale numerical volcanic models. The results of this experimental work have been developed into a probability distribution that has been integrated and incorporated into a multifluid numerical model. The numerical simulation was tested on a range of explosive depths and overpressure estimates from the 1790 eruption of Kilauea volcano, HI. The model output was compared to field data collected on the deposit thickness moving away from the source and the distribution, including both size and density, of aggregates. The mass fraction of ash removed from the eruption column in the form of aggregates was also calculated to examine how efficiently aggregation processes remove ash throughout the eruption. Cumulatively, the work presented here furthers our understanding of aggregation processes and the role they play in volcanic eruptions.