Master of Science

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  • Publication
    Open Access
    Discovery of bioactive secondary metabolites from benthic filamentous marine cyanobacteria
    Nurul Farhana Salleh

    The main objective of this MSc research was to discover marine natural products from filamentous marine cyanobacteria. These marine cyanobacteria samples were collected from various islands around Singapore such as Pulau Hantu Kechil, Lazarus and St. John’s Islands. The preliminary analysis of the extracts from these samples indicated interesting chemistry based on NMR and preliminary cytotoxicity assays. Henceforth, the chemistry and biological activities of the compounds isolated from these samples will be further discussed in the following chapters.

    In Chapters 1 to 3, it covers an introduction on the importance of marine natural products, filamentous marine cyanobacteria, and molecular networking in a natural product research. These chapters would support the purpose of conducting investigations on marine natural products coming from filamentous marine cyanobacteria.

    Chapter 4 covers the marine natural products that have been isolated from Pulau Hantu Kechil, which are known compounds, lyngbyatoxin A (1), majusculamides A (2) and B (3) from the filamentous marine cyanobacteria Lyngbya majuscula. These compounds were then further investigated for its biological activities to determine if it supports literature. Further investigations by molecular networking were then conducted to determine if potential analogues of these compounds are present.

    Chapter 5 describes the discovery and structural elucidation of lazarusamate (4), which is a linear lipopeptide isolated from the filamentous marine cyanobacteria Symploca sp. collected from Lazarus Island. Biological activities of the compound are also reported in this chapter. Molecular networking analysis was also conducted for this compound to determine presence of potential analogues.

    The last working chapter, Chapter 6, then describes the discovery and structural elucidation of benderadiene (5), which is a cyclopropyl containing compound isolated from the filamentous marine cyanobacteria Lyngbya majuscula cf., collected from St John’s Island. Biological activities of this compound were also reported and discussed, and a preliminary molecular docking experiment was conducted on Swissdock to further support the biological activity which the compound exhibited.

    Last but not least, the final chapter concludes the thesis which summarises the discovery of filamentous marine cyanobacterial compounds and potential future works.

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  • Publication
    Spaces of valuations
    Lim, Mark Xian Jin
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  • Publication
    Habitat selection of terrestrial mammals using environmental data
    Wan, Joejyn Marcus
    It is important to have a good understanding of the habitat selection patterns of the fauna inhabiting a landscape, as it helps to guide wildlife management, conservation, and monitoring efforts. However, basic ecological knowledge of the distribution and micro-habitat preferences are lacking for many terrestrial mammals, despite the crucial role they play in maintaining ecosystem stability and function. Through camera-trap surveys, this study aims to investigate the habitat selection patterns of terrestrial mammals within the Central Catchment Area in Singapore by correlating their spatial distribution with the heterogenous environment they inhabit.

    To assist in the processing of the camera-trap images obtained, a convolutional neural network model was built to classify each image as either empty, containing a human, or containing an animal. The convolutional neural network model was trained using camera-trap images captured at various nature areas and habitats across Singapore to ensure accuracy of the model to Singapore’s landscape. The trained model was found to be effective in classifying camera-trap images, with an F1 score of 89.6% for the images captured at Central Catchment Nature Reserve. It also enabled 85.9% of the images at Central Catchment Nature Reserve to be filtered out of the manual identification process, saving significant manpower and time required for image processing.

    Single-season, single-species occupancy modelling was conducted using distance to trail, distance to edge, light detecting and ranging (LiDAR) scan point densities of the understorey vegetation, Normalised Difference Vegetation Index, and Inverted Red Edge Chlorophyll Index as environmental covariates. Occupancy modelling was conducted for the terrestrial mammals recorded on the camera traps set up within the Central Catchment Area. Both the effect direction and relative importance of each covariate was determined for each species, and model-averaged estimates of habitat use and detection probability were also calculated from the selected models.

    None of the environmental factors were found to be significant for all of the terrestrial mammals tested; instead, each species had a unique combination of environmental factors influencing its habitat selection patterns. Each environmental covariate was also found to have different effect directions and relative importance across the different species, showing that habitat selection patterns are unique to each species and should not be generalised across species groups. Comparing these results to another habitat selection study also conducted within the Central Catchment Area, habitat selection patterns of the lesser mousedeer, sambar deer, and wild boar were similar, except for the effect of understorey density, whereby it was found that understorey density was actually a significant environmental factor influencing the habitat selection patterns of the three abovementioned species.

    Estimated habitat use of each species across the entire Central Catchment Area suggests that the long-tailed macaque and wild boar use most of the available landscape (99.9% and 98.9%, respectively), compared to the other non-generalist species. Knowledge of such land use is important for wildlife managers, considering that these two species are conflict species in Singapore. Unfortunately, LiDAR data across the entire study site are currently unavailable, and this limits the identification of specific areas that are used for each species.
  • Publication
    Smyth powerdomains
    Jeremy Ibrahim Abdul Gafar
    The thesis is about the study of a new approach of de ning the quasicontinuous dcpos that was rst proposed by Heckmann and Keimel in their paper [8]. This method relies on de ning the quasicontinuous dcpos X as those whose Smyth powerdomain Q(X), i.e., the corresponding dcpos of nitely generated compact saturated subsets of X ordered by reverse inclusion (i.e., the Smyth-order v), are continuous domains. Such an approach facilitated many simpler proofs for the elementary results concerning quasicontinuous dcpos as well as the upper powerspace, endowed with the upper Vietoris topology.

    My undergraduate experience allowed me a rst taste of using topology in a special topic in number theory, i.e., Furstenberg's Proof of the In nitude of Primes. My interest in topology started since then, and I wanted to explore deeper into topology. Given my very meagre topological experience, I had to amass a huge volume of background knowledge in topology, particularly in non-Hausdorff topology, before I could even begin to embark on my journey to study Domain Theory. To say the least, the learning curve for me in acquiring this body of mathematical knowledge is very steep for me.

    Part of this thesis is devoted to building this background knowledge, which comprises of three components: (i) Topology, (ii) Order theory which is about studying ordered structures like posets, lattices, complete lattices, dcpos, etc., and (iii) the theory of continuous domains.
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  • Publication
    Exercise and fitness contents on Reddit : an exploratory analysis
    Aisyah Latib
    Health promotion professionals recognize that social media is an attractive literacy tool for use as part of physical activity, exercise, and fitness intervention (Nutbeam, 2017; Whitaker et al., 2017). However, therein lies questions as to how best to implement and achieve effective outcomes through such services (Moorhead et al., 2018). Past research has offered some insights. For example, Facebook support groups have influenced general physical and mental health (Frison & Eggermont, 2016; Wright et al., 2013). Public health authorities may see the use of social media platforms to guide and disseminate news to the nation in the near future (Eghtesadi & Florea, 2020). Public perceptions of exercise and fitness issues on Facebook have been analyzed (Jaggi et al., 2018; Carrotte et al., 2015). The discourse of fit bodies and specialized diets in females resonate closely in the Facebook narrative, and other research studies internationally (Wick & Harriger, 2018; Rojkowski & Schöps, 2021). Beyond doubt, there is an understanding among researchers that (1) social media content has influence on users and (2) the narratives on social media can affect users’ perception of exercise and fitness. While Facebook attracts millions of users, other social media platforms create different social understanding on fitness and exercise. Twitter users gather to discuss physical activity through fitness application and functions (Molina & Sundar, 2018; Vickey et al., 2013) Therefore, in pursuit of understanding exercise and fitness content and behaviour on social media, this brings about the importance of gathering and understanding information in various sources. Apart from one study which investigated the discussion on weight loss, there has been no other study analysing exercise and fitness discourse on Reddit. This study aims to be the first to explore, describe and analyze exercise and fitness content on Reddit community. Additionally, understanding what users browse and post on Reddit can allow better understanding of how the platform can be integrated into the realm of physical activity and exercise.

    Briefly, Reddit is a website where registered users anonymously follow and engage in communities (subreddits) of interest. From the perspective of health care professional and researchers, it would be beneficial to understand the key functionalities, use and structure of the Reddit portal which has more than 430 million monthly active users (Statista, 2021). Given that so little is known about the nature of information available in Reddit on fitness and exercise in the research realm, the aim of this dissertation is to unpack the existing information structure in Reddit and offer insights for future researchers interested in studying the Reddit data in a deeper fashion. Specifically, comments posted in the subreddit “fitness” will be examined in this thesis to understand the themes within.

    The foray into Reddit data through systematic research is not new outside of fitness. For instance, researchers have studied personal narratives, unique to Reddit, to detect mental disorders and stigmatic illnesses. (De Choudhury & De, 2014; Shen & Rudzicz, 2017; Tadesse et al., 2019). Such attempts involved analysing linguistic attributes manifested in the nature of the content and showed that registered users share more explicit information compared on other health forums, and social networking sites. Furthermore, Reddit scores can potentially create impact as posts with higher popularity and votes sits on a better position on the webpage, gaining more attention. Thus, there is value in exploring the types of themes that emerge based on the popularity of discussion threads and posts. The second study aims to explore the types of themes on Reddit using similar constructs to identify the role it potentially has in fitness and exercise. Most importantly, it aims to support the notion that social media enhance opportunities of impactful health intervention, and health effects (Carr et al., 2013). The study aims to explore Reddit’s capabilities of gauging the masses’ literacy of exercise and fitness hoping to determine the needs and interests of the masses for health professionals and future researchers to leverage. Four months of submissions accumulating to 143,996 posts were collected through an open Reddit API, in which the dataset comprises of a list of variables. The variables were further studied and thus were found to be capable of identifying discussion trees. Hence, 268 discussion trees were identified as contributing factors towards Reddit use in the “/r/Fitness” subreddit within the 4 months. Following this, the study identified distinctive topics in which drives Reddit users and the sentiments surrounding the discussion in this subreddit. Results indicated Reddit users discuss exercise and fitness in this subreddit and predominantly discussed about (1) diet in relation to the fitness workouts, (2) diet in relation to body composition and (3) exercise regimes and workouts (e.g., endurance and weight training). The diverse discussions are similar to other platforms (Karami et al., 2018) possibly due to the high volume of users (Statista, 2021). Additionally, the commonality for users to share information on workouts and exercise regimes resonates with the current literature which found that users do so to seek positive affirmation (Stagier & Merchant, 2013). As this further affirms the key functionality of Reddit, creating a community of users with the same interest, it is worth exploring future intervention in targeted populations. Secondly, discussions in the community tend to be generally neutral or positive. Contrary to findings on mental health communities, where posts were indicative of greater negative emotions (Shen & Rudzicz, 2017; Tadesse et al., 2019), users in this community very often were stories of own experiences and knowledge. This form of narrative is worth establishing as the users show engage in fitness and exercise with positivity or neutral rather than negativity. Interestingly, users in this community create a desired impression or behavior to exercise by sharing records such as fitness app use, playlists, or experiences. Given the current literature indicating great focus on disease prevention improvement in health status and disease prevention (Dieli-Conwright et al., 2018; Dasso, 2019; Rodriguez-Ayllon et al., 2018) or exercise prescription, and the tendency to engage in discussing non-acceptable health norms on social media (Jaggi et al., 2017), this finding comes new. Subsequently, the discussion of the current trends on the type of workouts, training modalities and apps used can allow researchers develop and implement fitness models. This study marks the first in developing a detailed description of the processes to collect, analyze, interpret, and structure Reddit datasets. Consequently, the study explored the discussions around the Fitness subreddit and characterize the sentiments in relation to the discourse. It is worth noting that this model can be reproduced to future works to produce a more robust description of the fitness and exercise discipline on social media.
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