Switching Diffusions: Applications To Ecological Models, And Numerical Methods For Games In Insurance

Recently, a class of dynamic systems called ``hybrid systems containing both continuous dynamics and discrete events has been adapted to treat a wide variety of situations arising in many real-world situations. Motivated by such development, this dissertation is devoted to the study of dynamical systems involving a Markov chain as the randomly switching process. The systems studied include hybrid competitive Lotka-Volterra ecosystems and non-zero-sum stochastic differential games between two insurance companies with regime-switching. The first part is concerned with competitive Lotka-Volterra model with Markov switching. A novelty of the contribution is that the Markov chain has a countable state space. Our main objective is to reduce the computational complexity by using the two-time-scale formulation. Because the existence and uniqueness as well as continuity of solutions for Lotka-Volterra ecosystems with Markovian switching in which the switching takes place in a countable set are not available, such properties are studied first. The two-time scale feature is highlighted by introducing a small parameter into the generator of the Markov chain. When the small parameter goes to 0, there is a limit system or reduced system. It is established in this work that if the reduced system possesses certain properties such as permanence and extinction, etc., then the complex original system also has the same properties when the parameter is sufficiently small. These results are obtained by using the perturbed Lyapunov function methods. The second part develops an approximation procedure for a class of non-zero-sum stochastic differential games for investment and reinsurance between two insurance companies. Both proportional reinsurance and excess-of-loss reinsurance policies are considered. We develop numerical algorithms to obtain the approximation to the Nash equilibrium by adopting the Markov chain approximation methodology. We establish the convergence of the approximation sequences and the approximation to the value functions. Numerical examples are presented to illustrate the applicability of the algorithms

The Value Chain of White Leg Shrimp Exported to the U.S Market: The Case of Khanh Hoa Province, Vietnam

Three years since 2008, white leg shrimp have exhibited fabulous growth rate and become a popular livestock along with black tiger shrimp and pangasius. This gives rise to the interest to investigate the value chain of frozen white leg shrimp exported to the U.S from Khanh Hoa Province, Vietnam. Research findings showed that before exported to the U.S, white leg shrimp undergo farming, procurement, and processing. Shrimp farming comprises of pond cleaning, seed release, and caring. As shrimp attain harvestable size, middlemen come to perform the procurement including harvesting, preserving, and transporting. At the processing plants, shrimp are transformed into final products, packed, labeled preserved and stored waiting to be exported. During farming, farmers incur costs like seed, feed, labor, and other miscellaneous expenses. At the procurement stage, addition to purchasing shrimp from farmers, middlemen add some other costs like transport, labor, ice, and other inputs to transfer shrimp to the next stage. At the processing stage, direct material, labor, overhead, and other costs are added in accordance with the accounting format. Farmers, middlemen and processors experience positive profit in the 2008-2010 period. Based on costs and earnings data, some calculations were made to reveal the distributions of revenue, cost and profit of 1 kg frozen shrimp exported to the U.S. Revenue and profits were distributed in sync with incurred costs. The research also revealed reasons why farmers depend on middlemen to sell their harvest, that is, lack of facilities, delayed payment policy and risk aversion.Keywords: Special Topics, Posters and Game Demonstration Session and Reception, Fisheries EconomicsKeywords: Special Topics, Posters and Game Demonstration Session and Reception, Fisheries Economic

Climate Change Impacts, Vulnerability Assessment and Economic Analysis of Adaptation Strategies in Ben Tre Province, Vietnam

Scientific database has proven that Vietnam is one of the most affected countries due to climate change impacts on aquaculture and economies of rural communities. Ben Tre region has suffered immensely from recent salt water intrusion. Climate change generates sea level rise, increase in temperature and salt water intrusion. In 2005 losses had increased to US$37 million. We conducted three focus group discussions (FGDs) to assist in the identification of vulnerable sectors and households and community adaptation strategies to climate change. Households were also evaluated based on the levels of vulnerability. Residents have requested the construction of a water treatment plant and a dike system. CEA is employed as the tool for evaluating the two planned adaptations: Building a freshwater-supplying factory and Building a sea dike system. Total costs include initial investment and annual operating costs. We also conducted a benefit cost analysis since the outcomes of the strategies are different. The distribution of vulnerability index showed that 31% of households are highly vulnerable to climatic risk while 56% of households are not vulnerable at all. The sea dike is three times more expensive than the freshwater plant. In addition to the higher investment, it is more costly to keep the sea dike under operation annually. The water treatment plant is more cost effective in servicing the communities with freshwater but the dike has a higher benefit cost ratio when all costs are internalized and secondary benefits to agriculture and aquaculture are considered.EEPSEA and WorldFish Cente

Climate Change Awareness and Impacts on Aquaculture in Poor Rural Coastal Communities, Ben Tre Province, Vietnam

Vietnam has been ranked as one of the countries in Asia with the highest vulnerabilities to climate change impacts on fisheries and aquaculture. Eight of those ten provinces are located in the Mekong River Delta, including Ben Tre Province. We conducted a study to identify the impacts of climate change events on Ben Tre province poor rural coastal communities, to evaluate their awareness and the effects of climate change events on aquaculture. Farmers were aware of changing climatic conditions and pointed out indicators of these changes: (1) Changes in production and culturing patterns, (2) Changes in housing designs, (3) Improvement in drinking water collection and increase in water procurement, (4) Pumping of fresh water in the shrimp ponds, and (5) Building of dikes to prevent salt water intrusion. About 90 percent of respondents indicated that they suffered losses from salt water intrusion. Total losses generated by salt water intrusion amounted to VND 1,599,803,000, equivalent to USD 77,151. Age, education and previous effects from climate change events affected knowledge and perception of severity of climate change events. Farmers who were engaged in aquaculture were more likely to be prepared for climate change events than those who were not.EEPSEA and WorldFish Cente

The responsibility of C-terminal domain in the thermolabile haemolysin activity of Vibrio parahaemolyticus and inhibition treatments by Phellinus sp. extracts

The thermolabile haemolysin (tlh) of Vibrio parahaemolyticus (Vptlh) from V. parahaemolyticus is a multiple-function enzyme, initially describes as a haemolytic factor activated by lecithin and phospholipase A2 enzymatic activity (Shinoda, 1991; Vazquez-Morado, 2021; Yanagase et al., 1970). Until now, the tlh structure has hypothesized including N-terminal and C-terminal domain, but what domain of the Vptlh structure does the haemolytic activity has not been refined yet. In this study, a 450-bp VpTLH nucleotide sequence of the entire Vptlh gene encoded the C-terminal domain cloned firstly to examine its responsibility in the activity of the Vptlh. The C-terminal domain fused with a 6-His-tag named the His-tag-VpC-terminal domain was expressed successfully in soluble form in the BL21 (DE3) PlysS cell. Remarkably, both expression and purification results confirmed a high agreement in the molecular weight of the His-tag-VpC-terminal domain was 47 kDa. This work showed the His-tag-VpC-terminal domain lysed the erythrocyte membranes in the blood agar and the phosphate buffered saline (0.9%) media without adding the lecithin substrate of the phospholipase enzyme. Haemolysis occurred at all tested diluted concentrations of His-tag-VpC-terminal domain (p < 0.05), providing evidence for the independent haemolytic activity of the His-tag-VpC-terminal domain. The content of 100 μg of the His-tag-VpC-terminal domain brought the highest haemolytic activity of 80% compared to that in the three remaining contents. Significantly, the His-tag-VpC-terminal domain demonstrated not to involve the phospholipase activity in Luria-Bertani agar supplemented with 1% (vol/vol) egg yolk emulsion. All results proved the vital responsibility of the His-tag-VpC-terminal domain in causing the haemolytic activity without the required activation by the phospholipase enzyme. Raw extracts of Phellinus igniarus and Phellinus pipi at 10-1 mg/mL inhibited the haemolytic activity of the His-tag-VpC-terminal domain from 67.7% to 87.42%, respectively. Hence applying the His-tag-VpC-terminal domain as a simple biological material to evaluate quickly potential derivatives against the Vptlh in vivo conditions will accessible and more advantageous than using the whole of the Vptlh

Foodborne zoonotic trematode infections in Yen Bai, Vietnam : a situational analysis on knowledge, attitude, and practice (KAP) and risk behaviors

Publisher Copyright: © Copyright by Pacini Editore Srl, Pisa, Italy.Introduction. Foodborne Zoonotic Trematode Infections (FZTi) are neglected tropical diseases of public health concern in Vietnam. The transmission of FZTi is linked to human behavior patterns. The aims to investigate the knowledge, attitude, and practices regarding FZTi among local people. Methods. A cross-sectional study was conducted using a mixed method, which included a baseline survey and in-depth interviews. 375 participants were interviewed face-to-face in the survey, and 27 participants had the in-depth interviews. Results. The results showed that 36.3% passed the knowledge assessment, 86.7% passed the attitude assessment, and 24% passed the practical assessment. There were differences in average knowledge scores among gender (men higher than women, p = 0.006), ethnicities (Kinh higher than Dao and Tay, p < 0.001), and educational level (higher education, higher knowledge score, p < 0.001). There were differences in the frequency of eating raw fish between men and women (men higher than women, p < 0.001), and in the average practice score between men and women (women higher than men, p = 0.028). Eating raw fish and/or undercooked fish, raw vegetables, and drinking untreated water from Thac Ba lake in Yen Bai province were identified as FZTi risk behaviors. The occurrence of these risky habits can be explained by the lack of knowledge on FZTi, poor economic conditions and typical social features of local people. Conclusion. The current knowledge of local people in regard to safe eating practices is poor. They keep performing unsafe practices, which lead to infection with FZTi; therefore, an integrated control of FZTi is essential.Peer reviewe

Biflavones and megastigmane glycosides from the leaves of Antidesma bunius.

Two biflavones, podocarpusflavone A (1) and amentoflavone (2) and two megastigmane glycosides, byzantionoside B (3) and (6S,9R)-roseoside (4) were isolated from the methanol extract of the leaves of Antidesma bunius. Their structures were determined by spectroscopic methods and in comparison with the published data. Keywords. Antidesma bunius, Euphorbiaceae, biflavone, megastigmane

Can a Short Food Supply Chain Create Sustainable Benefits for Small Farmers in Developing Countries? An Exploratory Study of Vietnam

A number of studies have indicated that short food supply chains could create economic, social, and environmental benefits, but most of those chains were implemented in developed countries. This research aims to find out the characteristics of short food supply chains and their benefits to small farmers in Vietnam, which is a developing country, based on the survey results from 338 small farmers in the third quarter of 2020, with the support of Stata 14 software. The results showed that the short food supply chains in the survey sample in Vietnam were characterized by two main actors: small farmers and distributors. Farmers could sell products flexibly at the local market. There was some initial evidence to prove that these chains helped to stabilize the input, output price, and revenue; formulated sustainable income; and increased the satisfaction and confidence of farmers. They eliminated gender discrimination in rural areas and improved livelihood for ethnic minorities. These chains also enhanced the mindset on green, organic, and clean production of farmers, which in turn created environmental benefits. COVID-19 has posed a negative impact on the income of farmers and made them change their production and sales method. Therefore, the research could suggest some policies to sustainably develop the short food supply chains in Vietnam in the future

Safety and efficacy of fluoxetine on functional outcome after acute stroke (AFFINITY): a randomised, double-blind, placebo-controlled trial

Background Trials of fluoxetine for recovery after stroke report conflicting results. The Assessment oF FluoxetINe In sTroke recoverY (AFFINITY) trial aimed to show if daily oral fluoxetine for 6 months after stroke improves functional outcome in an ethnically diverse population. Methods AFFINITY was a randomised, parallel-group, double-blind, placebo-controlled trial done in 43 hospital stroke units in Australia (n=29), New Zealand (four), and Vietnam (ten). Eligible patients were adults (aged ≥18 years) with a clinical diagnosis of acute stroke in the previous 2–15 days, brain imaging consistent with ischaemic or haemorrhagic stroke, and a persisting neurological deficit that produced a modified Rankin Scale (mRS) score of 1 or more. Patients were randomly assigned 1:1 via a web-based system using a minimisation algorithm to once daily, oral fluoxetine 20 mg capsules or matching placebo for 6 months. Patients, carers, investigators, and outcome assessors were masked to the treatment allocation. The primary outcome was functional status, measured by the mRS, at 6 months. The primary analysis was an ordinal logistic regression of the mRS at 6 months, adjusted for minimisation variables. Primary and safety analyses were done according to the patient's treatment allocation. The trial is registered with the Australian New Zealand Clinical Trials Registry, ACTRN12611000774921. Findings Between Jan 11, 2013, and June 30, 2019, 1280 patients were recruited in Australia (n=532), New Zealand (n=42), and Vietnam (n=706), of whom 642 were randomly assigned to fluoxetine and 638 were randomly assigned to placebo. Mean duration of trial treatment was 167 days (SD 48·1). At 6 months, mRS data were available in 624 (97%) patients in the fluoxetine group and 632 (99%) in the placebo group. The distribution of mRS categories was similar in the fluoxetine and placebo groups (adjusted common odds ratio 0·94, 95% CI 0·76–1·15; p=0·53). Compared with patients in the placebo group, patients in the fluoxetine group had more falls (20 [3%] vs seven [1%]; p=0·018), bone fractures (19 [3%] vs six [1%]; p=0·014), and epileptic seizures (ten [2%] vs two [<1%]; p=0·038) at 6 months. Interpretation Oral fluoxetine 20 mg daily for 6 months after acute stroke did not improve functional outcome and increased the risk of falls, bone fractures, and epileptic seizures. These results do not support the use of fluoxetine to improve functional outcome after stroke