Vinylesters are termosets resins that have reactive double bond at the chain ends. They are produced by the reaction of various epoxies and acrylic acids by step growth polymerization. Vinylester chains are oligomers with molecular weight from 600 to 1200 g/mol. The resin viscosity is very high / therefore, diluent is used for easy application. The generally used diluent is styrene with, reactive double bonds to form a crosslink between the chains. The diluted resin viscosities are between 200 &amp / #8211 / 2000 cps. Peroxide initiators are used for network formation. The mechanical properties of vinylester resin are enhanced with reinforcements such as glass fiber, carbon fiber, Kevlar or nanoparticules to make composites. Various molecular weights of vinylester resins were synthesized and the samples were prepared with different styrene contents. The effects of the styrene content, temperature and molecular weight on the viscosity were measured and examined. The main effects were determined as styrene content and temperature, while the effect of molecular weight is negligible. The resins were characterized with IR and NMR spectroscopy. The molecular weights were determined by theoretical calculations, titration and H-NMR spectroscopy. Peroxide initiators were used to cure the resins with the cobalt complex accelerator. The resins were post-cured at different temperatures. The completion of the curing was monitored by the disappearance of the carbon-carbon double bonds of methacrylate (943 cm-1) and styrene (910 cm-1), by FT-IR spectrum. The effects of styrene content, post-cure conditions, and molecular weight on the mechanical properties were discussed. The glass transition temperatures were determined by DSC and DMA. The crosslink densities and rheological properties were determined by creep test. The important properties of vinylester resins, which are modulus, tensile and flexural strength, shrinkage, water absorption, glass transition temperature, HDT values and impact strength were investigated.

Analysing ecological communities as complex networks of interactions has become an important tool for ecologists. Understanding how these networks change through time, over landscapes, or in response to disturbances is a primary goal of community ecology. The number of interactions and the way in which those interactions organise themselves as individuals, small groups, and the whole community can play an important role in predicting how ecological communities will respond to disturbances. In this thesis, we investigated variation in network structure at several scales both empirically and in a theoretical context. Our first hypothesis was that the structural role of species in a variable system would show little variation, despite high levels of species turnover and a fragmented landscape. In a collaboration with Riikkaa Kaartinen and Tomas Roslin, we studied the distribution of species’ roles at three scales in host-parasitoid networks collected from a fragmented forest in Finland. We found that species’ roles were remarkably consistent through time and in the presence of species turnover. These results suggest that species’ roles may be an intrinsic property of species and may be predictable over spatial and temporal scales. Our second study investigated the structural variation of simulated ecological networks and the relationship between structural variation and whole-network measures of network organization, such as connectance, nestedness, and modularity. We quantified structural variation of networks at three scales, macro-scale, motif-scale, and participation scale. These scales represent whole-network measures (macro-scale), sub-network measures (motifs – small groups of interacting species), and individual measures (motif participation). We compared the variation in these structures to connectance, nestedness, and modularity. We found that at fixed levels of connectance, nestedness, and modularity, the motif profiles of networks and the distribution of species across those profiles showed remarkable dissimilarity. This result suggests that networks displaying similar macro-scale structural measures can be composed of vastly different motif- and participation-scale structures. Together, the work that makes up this thesis suggests that we should give more attention to the meso-scale structures of ecological networks. As the more detailed perspective of motifs can capture additional detail about the structure of empirical networks, and as a result, provide a clearer picture of ecological communities. In addition, we found that the particular species themselves can have a significant impact on the meso-scale structure and, in some cases, may impose strict limitations on what interactions can occur within a community. This has important implications for our understanding of how ecological networks are built and maintained, and thereby for our understanding of the stability and resilience of ecological communities.

Motivation: Cardiovascular disease (CVD) is one of the leading causes of mortality and morbidity in South Africa and worldwide. Dyslipidaemia and an increased coagulation state contribute to the development of CVD. The quality of fibrin network structure (FNS) may also contribute to the risk for CVD and thrombosis. Changes in fibrinogen concentration directly affect FNS. Management of these risk factors is important and dietary intervention forms an essential part of this management program. An increased intake of vitamin C can lead to a decreased susceptibility to infection and subsequently to decreased levels of haemostatic factors (that give rise to an anti-thrombotic state) and thus reduction in CVD and mortality. Furthermore, vitamin C may prove to be beneficial by increasing the pro-fibrinolytx activities of FNS (formation of thick fibrin fibers and more lysable clots) that could result in a reduction in atherosclerosis and subsequent CVD. Obiective: To investigate the effects of FoodState Vitamin C complex supplementation on haemostatic factors, FNS, serum lipids and lipoprotein (a) (Lp(a)) in hyperlipideamic adults. Methods: Thirty free-living hiperlipidaemic volunteers from the Lipid Clinic, Potchefstroom University for Christian Higher Education (CHE), participated in this randomised placebo controlled double blind crossover study. The subjects were randomly divided into two groups (A or B). After a run-in period of 4 weeks during which the subjects excluded all vitamin supplements, Group A received 2 tablets/day of FoodState Vitamin C complex (500mg vitamin C, 600mg magnesium food complex, 900mg vitamin B complex and 160mg bioflavonoids) and Group B received 2 tablets/day of placebo, for at least 8 weeks. A washout period of 8 weeks followed after which the treatments were crossed-over for a further 8 weeks. Fasting blood samples were drawn 8 times (two samples, one week apart at the beginning and end of each treatment). Results: FoodState Vitamin C complex supplementation did not significantly influence the levels of plasma fibrinogen, plasminogen activator inhibitor 1 activity (PAI-I act), tissue plasminogen activator antigen (tPA ag) or d-dimer. Serum lipids and Lp(a) were also not affected. Median plasmin-antiplasmin complex (PAP) and thrombin-antithrombin complex (TAT) levels, which are markers of plasmin (initiate fibrinolysis) and thrombin (initiate coagulation) generation respectively, were both significantly decreased compared to placebo (PAP: 4.05[-23.39, -0.231% vs 1.81[-8.95, 8.091%; TAT: -5.81[-18,47, 0.391% vs 0.12[-8.03, 13.51%). FoodState Vitamin C complex beneficially affected FNS by significantly increasing compaction (49.95[47.55,53.70]% to 51.85[48.55,56.65]%). Conclusion: The decreases in TAT and PAP are possibly an indication that the FoodState Vitamin C complex decreased the initiation of haemostasis, which in turn led to a compensatory reduction in fibrinolysis. FoodState Vitamin C complex may, therefore be protective of cardiovascular disease by causing a new reduced steady state of hemostatic balance and more lysable clots (increased compaction). / Thesis (M.Sc. (Nutrition))--North-West University, Potchefstroom Campus, 2004.

Adolescents are disproportionately affected by a wide range of STDs due to high level of personal risk behaviors and poor access to STD prevention services. As documented in numerous previous studies, STDs could lead to many serious consequences to adolescents’ health and the overall well being of society. One prominent concern is that STDs increase adolescent’s risk in acquiring HIV infection. Among all STDs, Chlamydia is the most prevalent in adolescents as well as in the general population. No previous studies have attempted to examine the social interaction of adolescent population heavily affected by Chlamydia. In this study, we would like to take a step forward to identify the difference in behavioral risk level between Chlamydia positive and negative adolescent social network and to describe any impacts of these groups on the transmission of other STDs using social network analysis of data collected from adolescent population in Dekalb County, Georgia. The results indicated highest behavioral risk in the negative girl index respondents’ contacts followed by those of positive boys, positive girls and finally negative boys. However STD prevalence in the contacts among these different groups did not follow the same pattern. Prevalence of STD is highest in the negative girls’ contact group followed by that of positive boys, negative boys; and interestingly positive boys’ contacts exhibit the lowest STD rate. As informed by the results, the presence of infection is not a sufficient indicator of risks; thus, network characteristic was also examined to accurately determine transmission dynamics in this population. Social and sexual network structures among these four different index groups and their contacts suggested low level of STD transmission.

Many dramatic and potentially powerful uses of information technology involveinterorganizational systems (IOS). These systems, defined as distributed computing systems thatsupport shared processes between firms, have become fundamental to business operations,spanning multiple activities in value/supply chains. They have opened avenues to unprecedentedcollaborative linkages between firms. As IOS-mediated relational networks are rapidly evolving,roles of IOS have progressively changed beyond those of efficiency and power functions.To fully appreciate modern roles of IOS in e-business, this dissertation addresses two keyresearch questions: (1) How do firms achieve competitiveness through IOS? (2) How do IOSinfluence competitive behaviors of the competing firms in intertwined electronic networks? Itdoes so by integrating three research streams – social network analysis, interorganizationalsystems, and competitive dynamics – into a model of competitive dynamics in electronicnetworks. This study focuses on the paired relationships between the three constructs of networkstructure, IOS use, and competitive action, and empirically investigates nine general hypotheses.Data collection focuses on second-hand data in the automotive industry. A total of 805collaborative relationships, 106 IOS technologies and applications, and 305 competitive actionsinvolving nine major automakers are collected. Data sources include databases, major tradepublications, Web sites, and industry indices. Data analysis includes network analysis, ANOVAtest, and correlation.Empirical results support the general contention that network structure and IOS use coevolveand influence competitive action. Building on these results, a framework characterizingIOS's roles in achieving firm competitiveness is concluded and advanced. This dissertation broadens our view of IOS's roles in e-business. It contributes to IS/IOS theory, methodology, and practice. First, this study examines IOS-mediated networks inmultiple levels, including firm-level, pair-level, and network-level. It provides new theoreticalconceptualizations of IOS's roles. Second, this study advances a new IT value measureaddressing limitations of the traditional measures. Third, it introduces a novel, usefulmethodology for data collection. Fourth, results from this study can guide a firm's e-businessinitiatives for using IOS as powerful tools for achieving firm competitiveness.

This study was designed to explore the possible connections between student peer relationships and individual students’ roles in a network as it pertained to outcomes such as self-reported academic achievement and personal satisfaction with the first year of college. The research question directing this inquiry is: How does a student’s role within a residential community of peers relate to success in college? Social network analysis was employed for examination of individual engagement within the context of a larger community. The vast learning community literature tells an interesting story: 1.) a history of co-curricular peer learning environments, 2) a tradition of research intended to assess the value of these programs, 3) a body of literature that provides theoretical explanations for why learning communities should work. The gap in the literature is found regarding what happens within the communities. To learn how individuals within community learn from one another, community of practice was utilized as a framework in this mixed-methods approach to examine the influence of relationships, and exchange, acquisition, & development of social capital within a living learning community While this network study indicated that popularity, relational ties to staff, and being someone sought-after for advice were not statistically significant predictors of higher GPA, the network analyses confirmed strong network density, cohesion, and proper structure for ideal capital flow. The results of this study confirm that this community is effective in establishing familiarity and even more so, providing an environment that fosters friendships among participants and staff. Furthermore, students developed the ability to construct knowledge alongside their peers. Given the density and relation-rich nature of this community, this positive environment is able to foster more complex and self-authored levels of meaning-making for the students involved. Building this scaffolding facilitated student development, which effectively created a student transformation from dependence on external authority to self-authorship. This study confirmed that the primary goals of a learning community have been met: a group of strangers developed into a network of friends who reap social and academic benefits by virtue of being together in a shared and successful living learning community environment.

Motivation: Cardiovascular disease (CVD) is one of the leading causes of mortality and morbidity in South Africa and worldwide. Dyslipidaemia and an increased coagulation state contribute to the development of CVD. The quality of fibrin network structure (FNS) may also contribute to the risk for CVD and thrombosis. Changes in fibrinogen concentration directly affect FNS. Management of these risk factors is important and dietary intervention forms an essential part of this management program. An increased intake of vitamin C can lead to a decreased susceptibility to infection and subsequently to decreased levels of haemostatic factors (that give rise to an anti-thrombotic state) and thus reduction in CVD and mortality. Furthermore, vitamin C may prove to be beneficial by increasing the pro-fibrinolytx activities of FNS (formation of thick fibrin fibers and more lysable clots) that could result in a reduction in atherosclerosis and subsequent CVD. Obiective: To investigate the effects of FoodState Vitamin C complex supplementation on haemostatic factors, FNS, serum lipids and lipoprotein (a) (Lp(a)) in hyperlipideamic adults. Methods: Thirty free-living hiperlipidaemic volunteers from the Lipid Clinic, Potchefstroom University for Christian Higher Education (CHE), participated in this randomised placebo controlled double blind crossover study. The subjects were randomly divided into two groups (A or B). After a run-in period of 4 weeks during which the subjects excluded all vitamin supplements, Group A received 2 tablets/day of FoodState Vitamin C complex (500mg vitamin C, 600mg magnesium food complex, 900mg vitamin B complex and 160mg bioflavonoids) and Group B received 2 tablets/day of placebo, for at least 8 weeks. A washout period of 8 weeks followed after which the treatments were crossed-over for a further 8 weeks. Fasting blood samples were drawn 8 times (two samples, one week apart at the beginning and end of each treatment). Results: FoodState Vitamin C complex supplementation did not significantly influence the levels of plasma fibrinogen, plasminogen activator inhibitor 1 activity (PAI-I act), tissue plasminogen activator antigen (tPA ag) or d-dimer. Serum lipids and Lp(a) were also not affected. Median plasmin-antiplasmin complex (PAP) and thrombin-antithrombin complex (TAT) levels, which are markers of plasmin (initiate fibrinolysis) and thrombin (initiate coagulation) generation respectively, were both significantly decreased compared to placebo (PAP: 4.05[-23.39, -0.231% vs 1.81[-8.95, 8.091%; TAT: -5.81[-18,47, 0.391% vs 0.12[-8.03, 13.51%). FoodState Vitamin C complex beneficially affected FNS by significantly increasing compaction (49.95[47.55,53.70]% to 51.85[48.55,56.65]%). Conclusion: The decreases in TAT and PAP are possibly an indication that the FoodState Vitamin C complex decreased the initiation of haemostasis, which in turn led to a compensatory reduction in fibrinolysis. FoodState Vitamin C complex may, therefore be protective of cardiovascular disease by causing a new reduced steady state of hemostatic balance and more lysable clots (increased compaction). / Thesis (M.Sc. (Nutrition))--North-West University, Potchefstroom Campus, 2004.

This thesis presents a comprehensive exploratory analysis of truck route choice diversity in the state of Florida, for both long-haul and short-haul truck travel segments. We employ six metrics to measure three different dimensions of diversity in truck route choice between any given origin-destination (OD) pair. These dimensions are: (1) number of distinct routes used to travel between the OD pair, (2) the extent of overlap (or lack thereof) among the routes, and (3) the evenness (or the dominance) of the usage of different unique routes. The diversity metrics were utilized to examine truck route choice diversity from over 73,000 truck trips that were derived from over 200 million GPS records of a large truck fleet. Descriptive analysis and statistical modeling of the diversity metrics offered insights on the determinants of various dimensions of truck route choice diversity between an OD pair. The results could be used to improve choice set generation algorithms for truck route choice modeling as well as in planning truck route policies and investments.

The expansion and diffusion of mobile phones globally has resulted in the provision of financial transactional services over the existing mobile phone platforms, generally referred to as mobile money. The supply end of mobile money services is an important factor in the success of the financial transactions offering. This research assessed vulnerabilities in the mobile money supply network that are inherently related to the existence of the principal – agent problem and their implications on availability and access to the services. The research study was conducted using a qualitative approach. Qualitative information was collected through interviews guided by open – ended questionnaires. Thematic analysis approach was followed to systematically analyse the data and generate findings of the study. Agent transactional data was analysed to complement the findings from qualitative analysis The findings suggest that the principal agent problem permeates the mobile money delivery network mainly after businesses joining as agents and manifests as moral hazard. Moral hazard is the dominant feature of the principal – agent problem, with adverse selection very low. Drivers of moral hazard are demonstrated by the influences and demands of agents’ core businesses and challenges in agent monitoring and training. The existence of the principal – agent problem has limited or no implications on access and availability of services. However, overtime the combined vulnerabilities identified related to the principal agent problem are likely to manifest into risks that are likely to affect access and availability of mobile money services. Regulators, Mobile Network Operators and agent enterprises must collectively review monitoring approaches for mobile money service providers to address challenges identified and increase the effectiveness of monitoring. Service provision standards should be reviewed to suit the various business environments the services are provided within. Mobile Network Operators and agent enterprises need to institute stronger partnership arrangements that enhance ownership and obligations for all parties, in particular agent enterprises. Agreements must enable application of different mobile money delivery models suitable to meet the demands and requirements of the agents’ core businesses. Innovations such as Near Field Communication (NFC) can be integrated with Point of sale (POS) applications and mobile money platforms to reduce the administration burden on agents and human error. Such applications must consider the cost implications of adoption from the agents’ business perspective.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第19742号 / 工博第4197号 / 新制||工||1647(附属図書館) / 32778 / 京都大学大学院工学研究科高分子化学専攻 / (主査)教授 吉崎 武尚, 教授 古賀 毅, 准教授 竹中 幹人 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM