The development of noncircular chainrings to improve cycling performance has been in progress since the 1980’s and continues apace. The aim of this study was to compare performance time and physiological responses in cycling using a standard circular chainring versus a noncircular chainring developed in 2005: the Rotor Q-Ring. Eight competitive male cyclists were pre-tested using the original circular chainrings and also on the initial week of testing. The intervention consisted of cycling with Rotor Q-Rings for four weeks. Post-testing occurred with the original chainrings for the final week of testing. Testing consisted of a maximal or submaximal graded exercise test followed by a 1 k time trial. Oxygen consumption, carbon dioxide output, heart rate, ventilation, respiratory exchange ratio, and perceived exertion were continuously measured during the tests. Blood lactate concentration was measured during the last 30 s of each three minute stage. Five minutes after the submaximal test, participants performed an “all out” 1 k trial for time as well as maximum and average power. The main findings were: 1) Participants were on average 1.6 seconds faster in the 1 k time trial with Rotor Q-Rings compared to a circular chainrings. 2) There was a significant increase in average power (26.7 watts) and average speed (0.7 kph) during the 1 k time trial with Rotor Q-Rings. 3) Oxygen consumption (during weeks 2-4) and heart rate (weeks 1-3) were significantly lower with Rotor Q-Rings during submaximal testing when compared to circular chainrings. However, in contrast to our hypotheses no benefits were observed for other submaximal dependent measures (i.e., CO2, VE, RER, RPE, GE, DE, and lactate).

Cycling has a long history as a mode of human transportation. It is highly recognised for its contributions in environmental protection, public health improvements and community vitalisation. Many international cities have accommodated cycling as a fundamental part of their own city planning. Such implementation of cycling city may not be fit into the city centres of Hong Kong due to its demographics and composition of the urban transport system. Nevertheless, many previous studies have identified the possibility to promote intra-city cycling in the new towns. This study has reviewed the concept of cycling and definition of sustainable mobility. The history of local cycling planning and development is also explored. Interview survey has been conducted in the subject new towns to retrieve valuable data from the local user’s perspective. These data are further analysed to identify the reasons for the current low utilisation rate of intra-city cycling. It was discovered that safe cycling environment and efficient cycle track maintenance contribute to higher cycling usage, while prosecution of illegal parking of bicycles deters cycling usage. Several recommendations on cycling planning and infrastructure improvements are provided for the future government policymaking. / published_or_final_version / Transport Policy and Planning / Master / Master of Arts in Transport Policy and Planning

No description available.

No description available.

No description available.

No description available.

European legislation has increased pressure on the use of land to represent the major disposal option for sewage sludge. Owing to their importance in regulating soil fertility, much research has been conducted into the effects of sewage sludge application on soil microorganisms. However, little knowledge is known about its effects on community dynamics of the beta-subgroup ammonia oxidising bacteria. This is despite the fact that nitrification activity of these bacteria plays an important role in soil nitrogen cycling. This investigation aimed to examine community dynamics of the beta-subgroup ammonia oxidising bacteria in sewage sludge amended soil by employing recently developed molecular based techniques. Firstly, a soil DNA extraction protocol was identified that allowed routine nested PCR amplification of 16S rDNA using beta-subgroup ammonia oxidiser directed primers. Reproducibility observed in denaturant gradient gel electrophoresis (DGGE) profiles suggested that 0.5 g samples used for DNA extraction allowed consistent detection of dominant beta-subgroup ammonia oxidiser community members. The effects of applying primary treatment sewage sludge to a variety of contrasting soils on (3-subgroup ammonia oxidiser community structure was unclear. This was partially hampered by lack of specificity of PCR primers for non ammonia oxidiser 16S rDNA sequences. Further, through measurement of net nitrification, there was no indication that sewage sludge addition stimulated the activity of nitrifier populations. Nevertheless, this study indicated the usefulness of DGGE for screening multiple environmental samples. A set of hierarchical oligonucleotide probes exhibiting specificity at the group, genus and cluster level were optimised using a non-radioactive system. These probes were used to assess the effects of application of aerobically digested sewage sludge to soil for 4 y on beta-subgroup ammonia oxidiser community structure. Despite significant changes in measurable soil parameters including net nitrification activity no changes were observed in beta-subgroup ammonia oxidiser community structure. This indicated resilience of these communities to change. A final study was conducted examining the effects of application of anaerobically digested sewage sludge to soil on beta-subgroup ammonia oxidiser community structure. Inhibition of nitrification by acetylene indicated the presence of a viable population of ammonia oxidising bacteria in continuously shaken samples of sludge. DGGE and oligonucleotide probing analysis provided evidence that sewage populations had the potential to outcompete indigenous soil populations of beta-subgroup ammonia oxidising bacteria. This was despite the fact that MPN enumeration suggested that soil populations of these bacteria were in some cases 10-fold greater than sludge populations. Evidence was also provided that suggested net nitrification to be an unreliable indicator of ammonia oxidiser activity in soil. It is possible to conclude that community structure of the beta-subgroup ammonia oxidising bacteria may be altered by application of sewage sludge to soil. The effects on community structure are likely to be influenced by both the type and level of sludge applied to soil.

The spring application of fertiliser N often fails to stimulate grass growth in improved grass pastures on peaty soils. Fertiliser utilisation efficiencies under these conditions have been found to be low, suggesting that available N is not taken up by the plant. Previous work has suggested that in this type of system, the soil microbial biomass may function as a strong sink for fertiliser N and therefore limit plant growth in the Spring. A series of laboratory based experiments utilising reconstituted and intact cores, and homogenised peat, was set up to identify the factors controlling the competition between N uptake by plants and N immobilisation by soil microorganisms following the addition of fertiliser N to peat. Microbial biomass N concentrations were determined in order to quantify the amount of N present in the microbial pool. The use of 15N labelled fertilisers and selective biocides provides a powerful tool with which to characterise the microbial population responsible for the immobilisation of N under these conditions. Improvement of a grass pasture at Sletill Hill has resulted in the formation of a distinct layer comprised of partially decomposed roots, underneath the surface vegetation and it was within this layer, that microbial immobilisation of fertiliser N was found to occur. Approximately 30% of applied N (equivalent to ca 50 kgN ha-1) was found within the microbial biomass in this layer, 30 days after the addition of fertiliser N. Intact cores were removed from Sletill Hill and maintained under controlled abiotic conditions. Water table level and temperature were found to be important in controlling the extent of microbial immobilisation of applied N. Lowering the water table level increased the quantity of N present in plant and microbial N pools, particularly at lower temperatures (8°C). At higher temperatures (20°C), plant uptake of N tended to be less due to a restriction on plant growth caused by 'droughty' soil conditions.

The mobilization and transformation of arsenic within the critical zone is a major cause of human suffering worldwide. Microorganisms, as they grow and utilize organic matter, accelerate redox processes that can transform and mobilize arsenic within aquifers on a large scale. As such, naturally occurring groundwater arsenic is a particularly hazardous problem that is chronically poisoning over 100 million people annually. Historically, groundwater arsenic research has been focused on the two principal inorganic arsenic species: arsenate [As(V)] and arsenite [As(III)]. Recently, organic arsenic species have garnered more attention due to their mobility, toxicity, and contemporary recognition of the ephemeral yet significant role they have in the global arsenic cycle. Here, I discuss laboratory and in situ experiments focused on exploring how microorganisms transform, mobilize, and sequester arsenic within a biogeochemically complex aquifer system. In my laboratory experiments, I collected aquifer sediments from a naturally contaminated bedrock aquifer and incubated a series of laboratory microcosms. Our results show that simultaneously robust iron and sulfate reduction temporarily mitigated arsenic contamination but then directed arsenic to an unstable adsorbed phase were it was later mobilized. Second, I discuss two aquifer injection experiments designed to examine in situ microbial redox processes and the further explore the potential to stimulate arsenic sequestration through arsenic-sulfide precipitation. Our results show that in situ stimulation of microbial metabolisms accelerated the reduction of arsenic bearing iron (oxy)hydroxides as well as sulfate and arsenic reduction. Within 3 weeks of these contemporaneously occurring redox reactions, 90% of the dissolved inorganic arsenic was removed (~2000 ppb) and an effective long-term, anaerobically stable, sequestration of arsenic was observed by way of a significant increase of arsenic-sulfide precipitate. Finally, using both the laboratory and field experiments, I explore the potential of organic arsenic production rates under stimulated conditions. We report new methylation rates that are consequential to the potential efficacy of enhanced, biologically-driven arsenic remediation and the reconsidered significance of biomethylation pathways in aquifers. These results expand our current understanding of the metabolic reach aquifer microorganisms potentially have over the fate of arsenic.

Graduation date: 1992