1,243 research outputs found

    Change in Social Capital – a Case Study of Collective Rice Farming Practice in the Mekong Delta, Vietnam

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    This paper describes how the social capital of rice farmers of the Mekong delta of Vietnam - manifested in the tradition of collective farming practice, changed from the 1940s to 1990s. The reason this collective rice farming had existed for decades, irrespective of critical events that challenged its continuation, was the co-existence of two key factors – high need for collective farming to ensure subsistence, and the availability of a closely knit social network that facilitated the exchange of labor. Despite its longevity, the practice of a cohesive and spontaneous collective farming, particularly in terms of labor exchange and labor participation in farming activities, was not maintained under the influence of agrarian reforms which aimed to improve rural livelihood. Land reform resulted in individual rice farming, making mobilization for spontaneous collective action, at the community level quite challenging. The assessment arose in the context of the need to mobilize collective action for implementation of a Community Trap Barrier System (CTBS), an ecologically-based rodent pest management system. It is concluded that successful restoration of social capital in the form of collective farming practices at the field level may depend on government intervention strategies at both local and national policy levels.social capital, rice, Mekong, farming practice, agrarian reform

    Secular non-secular master equation

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    Redfield non-secular master equation governing relaxation of a spin in weak interaction with a thermal bath is studied. Using the fact that the relaxation follows the exponential law, we prove that in most cases the semi-secular approximation is sufficient to find the system relaxation rate. Based on this, a "secular" form of the non-secular master equation is for the first time developed which correctly set up one of most fundamental equations in relaxation investigation. This key secular form allows us to derive a general formula of the phonon-induced quantum tunneling rate which is valid for the entire range of temperature regardless of the basis. In incoherent tunneling regime and localized basis, this formula reduces to the ubiquitous incoherent tunneling rate. Meanwhile, in eigenstates basis, this tunneling rate is demonstrated to be equal to zero. From this secular form, we end the controversy surrounding the selection of basis for the secular approximation by figuring out the conditions for using this approximation in localized and eigenstates basis. Particularly, secular approximation in localized basis is justified in the regime of high temperature and small tunnel splittings. In contrast, a large ground doublet's tunnel splitting is required for the secular approximation in eigenstates basis. With these findings, this research lays a sound foundation for any treatments of the spin-phonon relaxation under any conditions provided that the non-secular master equation is relevant.Comment: 9 pages, 0 figure
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