Social and ecological challenges of market-oriented shrimp farming in Vietnam

Vietnam is one of the largest shrimp exporters in the world. Since 2010, Vietnam has earned about two billion dollars annually through shrimp exports. As a fertile area of greatest potential for agricultural production in Vietnam, the Mekong Delta has been a major contributor to the country’s achievements, especially in the agricultural sector. During recent decades, trade liberation along with various policies in support of aquaculture has accelerated the development of shrimp production in the Delta. Based on an ethnographic study of shrimp farming in the Mekong Delta of Vietnam, I assert that along with great rewards arising from the expansion of shrimp farming areas, productivity, and export value, the shrimp industry has brought various environmental, economic and social challenges. Consequently, shrimp farming is a risky business and local inhabitants have relied on various strategies to cope with these challenges. Risk mitigation in shrimp production and labor migration are the two important strategies of local inhabitants for securing their livelihoods. Water pollution and poor quality post-larvae shrimp are direct consequences of market-oriented production.

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http://repository.vnu.edu.vn/handle/VNU_123/33053

Efficient microencapsulation of a liquid isocyanate with in situ shell functionalization

We report on a one-pot, facile approach for the encapsulation of the liquid hexamethylene diisocyanate isocyanurate trimer in polyurea microcapsules formed via the oil-in-water interfacial reaction of an uretonimine- modified diphenyl methane diisocyanate trimer with triaminopyrimidine, with in situ shell functionalization/modification using different types of hydrophobic agents. Remarkably, the use of hexa-methylenedisilazane resulted in microcapsules of about 70 mu m in diameter, with a smooth outer surface and a high isocyanate core content up to 85 wt% as determined by quantitative online FT-IR analysis of the extracted core. On the other hand, the use of an alkylamine, fluorinated aromatic amine and/or perfluoride amine provided microcapsules of approximately 100 to 150 mu m in diameter containing around 65-75 wt% of the isocyanate core content, with the outer shell surface bearing pendant hydrophobic groups as confirmed by SEM-EDX. The effects of the functionalizing compound on the microcapsule properties such as shell morphology, size distribution and stability were assessed. After one day immersion in water, the initial isocyanate content of the microcapsules with a non-functionalized shell dropped rapidly from 49 to 15 wt%, whereas the ones with the modified shell structure maintained their core content, suggesting a significantly enhanced microcapsule stability.

This report is available at:

http://repository.vnu.edu.vn/handle/VNU_123/33076

Domino reaction of N-(cyanomethyl)-1,3-azolium quaternary salts with o-hydroxybenzaldehydes: scope and limitations

A route towards chromenes, annulated with an imidazo[5,1-c][1,4] thiazine core through a base-promoted domino reaction of thiazolium quaternary salts, has been developed. The synthesised compounds show high cytotoxic activity against human tumour cell lines.

This report is available at:

http://repository.vnu.edu.vn/handle/VNU_123/33081