Thesis (M.U.D.)--University of Hong Kong, 1998. / Includes bibliographical references (leaves 89-94).

Thesis (M.U.D.)--University of Hong Kong, 1997. / Includes bibliographical references (leaves 93-96).

Thesis (M. Sc.)--University of Hong Kong, 1996. / Includes bibliographical references.

No description available.

published_or_final_version / Biological Sciences / Doctoral / Doctor of Philosophy

published_or_final_version / Public Health / Master / Master of Public Health

published_or_final_version / Dentistry / Doctoral / Doctor of Philosophy

Conventional land use change detections with remote sensing use annual remote sensing images because of the limitations of optical sensors that cannot collect data in bad weather and cloudy conditions. This limits its applications in rapidly developing areas which are cloudy, such as the Pearl River Delta in China. These areas also need to detect land use changes in short intervals, such as on a monthly basis, in order to monitor illegal land use changes and prevent irreversible land use changes that may damage the environment. The objective of the thesis is to examine short-interval land use change detection, especially the change from agriculture to built-up areas, using RADARSAT-1 images which can go through clouds. This thesis firstly examines the classification of RADARSAT-1 images with pixel-based and object-based classification methods respectively. Based on the classification results, post-classification change detection method are conducted in order to obtain the detailed information of land use changes for the analysis of short-interval land use change. Land use change detection accuracies can be improved as the number of the RADARSAT-1 images used in land use change detection increased. More images, which represent longer monitoring period, can obtain better results of land use change detection. For short-interval land use changes detection, four time periods is the maximum otherwise the period of monitoring will be too long. Agricultural activities such as planting and harvesting have significant effects on the monitoring of land use changes. In planting and harvesting months, the accuracies of the land use change detection are lower than other months because its land cover is often confused with other land uses, such as water and bare soils. The process of construction can be considered as a three-stage process and a combination of two land uses. However, construction sites are often confused with vegetation and bare soil in RADARSAT-1 images because the values of backscatter coefficients of construction sites and the two land uses are very similar. The land cover changes during the planting and harvest seasons are often confused with the process of construction. It is found that construction sites can be identified with their two stages of low values of backscatter coefficients, which is not found in the pattern curves of backscatter coefficients of other land uses. By the comparison of the accuracies of identifying construction sites using two, three and four RADARSAT-1 images, it is found that using three time periods can get better accuracies which is different from the result of general land use change detection. This thesis does not try to evaluate land use change detection methods or find the best method for monitoring land use changes. Instead, it focused on the analysis of confusions caused by the time periods of land use change detection and seasonal variation of vegetations. The main contributions of this study are as follows: 1) it explores the use of multi-temporal RADARSAT-1 images into the land use change detection to overcome the problems of cloudy conditions, making short-interval land use change detection possible for areas which are often covered by clouds; 2) pixel-based maximum likelihood method and the object-based classification method were compared for their accuracies in land use classification of RADARSAT-1 images; 3) it examines the optimal time periods for land use change detection; and 4) it examines the appropriate number of images that are needed for monitoring land use changes in different seasons in order to obtain the best accuracies. / published_or_final_version / Urban Planning and Design / Doctoral / Doctor of Philosophy

Atherosclerosis is the major cause of cardiovascular diseases, which constitute the top ten leading causes of death worldwide. Atherosclerotic plaque development initiates from the inflamed endothelium under an atherogenic environment – chronic low grade inflammation, hypercholesterolemia, endotoxemia, etc. The principal cause of such inflammation has yet to be defined – with growing evidence that microbial stimulants like lipopolysaccharide (LPS) and peptidoglycan (PGN), which can activate toll-like receptors (TLRs) and nuclear factor-kappaB (NFκB) signaling might be the plausible origins. The gastrointestinal tract is suggested to be the major site for absorption and translocation of such stimulants, where gut microbiota have been associated with systemic inflammation and is essential in generating atherogenic substances. Since probiotics have the potential to induce systemic anti-inflammatory effects and fortify gut barrier to reduce bacterial translocation, evaluation of whether probiotics can help reduce atherogenesis was done by feeding the disease model, ApoE-/- mice with high fat diet alone, with telmisartan (1 or 5 mg/kg/day, positive controls) or with probiotics VSL#3 (2.8 x 1011 CFU/day) and/or Lactobacillus rhamnosus strain GG (LGG) (1x108 CFU/day), or the combination of which for 12 weeks. All treatments reduced lesion size significantly; with some treatments reduced plasma endotoxin, cholesterol and various proinflammatory biomarkers. The gut microbiota assessed with PCR-amplified 16S rRNA gene sequences using 454 pyrosequencing and thereafter correlation studies revealed that at least 20 bacterial families that were significantly altered by high fat diet in apolipoprotein E knockout (ApoE-/-)mice correlated with atherosclerotic plaque size and related biomarkers including cholesterol, adipocyte fatty acidbinding protein (A-FABP), etc. Probiotics showed potential in improving atherogenic environment by immunomodulation and induction or inhibition of growth of bacteria correlated with the atherosclerotic plaque and biomarkers. The atherosclerotic condition was also improved by telmisartan, which correlated with the altered gut microbiota. The newly identified atherosclerosis-related gut bacteria will require further exploration into their properties and mechanisms, which will eventually lead to the potential of developing probiotics for the treatment or prevention of atherosclerosis, and thus may be used as an affordable and non-invasive alternative that brings health benefits worldwide. / published_or_final_version / Biological Sciences / Doctoral / Doctor of Philosophy

Background Sexually transmitted diseases (STDs) and the epidemic from Human Immunodeficiency Virus (HIV) have spread rapidly in China. Very few studies have investigated the barriers of condoms among adolescents in China Objectives To find out the barriers of condom use among Chinese adolescents according to reviewing primary studies’ outcome conducted recent 10 years and to give advise for improvement for public health policy makers. Methods Articles were searched by using electronic sources: “PubMed”, “Google Scholar”, “China Journal full-text data base”. Keywords are “China”, “adolescent (teenagers*)”, “sexual behavior”, “condom use”, “attitude”, combined with “AND”. Language used in PUBMED and Google Scholar is English, and Chinese is used in “China Journal full-text data base(CJFD)”. Results This literature review has 6 studies for evidence-based analysis.9 categories of barriers have been summarized according to primary studies. Embarrassment of getting condoms, affect feelings, money, trust crisis, occasional sex would not lead to pregnant are most common reasons. Conclusion The embarrassment of getting a condom, occasional sex would not lead to pregnancy, trust crisis and less sexual knowledge are the most common barriers of condom use according studies. Thus, school education, parent communication and community based sex education are demanded for promoting safe sex behavior for adolescents in china. / published_or_final_version / Public Health / Master / Master of Public Health