Cash-based versus water-based payment for environmental services in the uplands of northern Vietnam: potential farmers participation using farm modeling

The forested areas of northern Vietnam, mostly located in mountainous areas, have important watershed regulating functions. However, current land-use changes pose a threat to the continuing provision of environmental services. This chapter investigates two alternative payment for environmental services (PES) programs tailored to reestablish natural or productive forests in the uplands of northern Vietnam: “Payments for Forest” (PFF) and “Terraces for Forest” (TFF). Both programs involve setting aside sloping land for reforestation but they differ in the type and amount of compensation offered. PFF offers annual payments per area of retired land. TFF offers to convert a certain amount of the current sloping land into a terraced area, combined with annual payments per area of retired land. The main objective of the chapter is to compare the two types of programs in terms of potential participation (what type of farmers will likely participate?), and what impact it would have on their revenues. Using mathematical programming, we developed a set of farm models corresponding to typical farms of a mountainous district of northern Vietnam. We simulated the level of participation of different types of farms for the two types of PES programs. For each specific PES, we analyzed participation, measured by the area of land converted into forest land and its impacts on land use and household revenues. Results show that, given the assumptions of the models, increasing access to irrigated terraces as a way to compensate for land conversion to forest increases the participation of the poorest farmers. Therefore, our research suggests that PES schemes, when fine-tuned to a Southeast Asian context, may not only be used as a way to restore ecosystem services but also as a way to alleviate poverty. (Résumé d'auteur

Spatial Analysis of Drug-Susceptible and Multidrug-Resistant Cases of Tuberculosis, Ho Chi Minh City, Vietnam, 2020–2023

We characterized the spatial distribution of drug-susceptible (DS) and multidrug-resistant (MDR) tuberculosis (TB) cases in Ho Chi Minh City, Vietnam, a major metropolis in southeastern Asia, and explored demographic and socioeconomic factors associated with local TB burden. Hot spots of DS and MDR TB incidence were observed in the central parts of Ho Chi Minh City, and substantial heterogeneity was observed across wards. Positive spatial autocorrelation was observed for both DS TB and MDR TB. Ward-level TB incidence was associated with HIV prevalence and the male proportion of the population. No ward-level demographic and socioeconomic indicators were associated with MDR TB case count relative to total TB case count. Our findings might inform spatially targeted TB control strategies and provide insights for generating hypotheses about the nature of the relationship between DS and MDR TB in Ho Chi Minh City and the wider southeastern region of Asia

Computational study of radial particle migration and stresslet distributions in particle-laden turbulent pipe flow

Particle-laden turbulent flows occur in a variety of industrial applications as well as in naturally occurring flows. While the numerical simulation of such flows has seen significant advances in recent years, it still remains a challenging problem. Many studies investigated the rheology of dense suspensions in laminar flows as well as the dynamics of point-particles in turbulence. Here we employ a fully-resolved numerical simulation based on a lattice Boltzmann scheme, to investigate turbulent flow with large neutrally buoyant particles in a pipe flow at low Reynolds number and in dilute regimes. The energy input is kept fixed resulting in a Reynolds number based on the friction velocity around 250. Two different particle radii were used giving a particle-pipe diameter ratio of 0.05 and 0.075. The number of particles is kept constant resulting in a volume fraction of 0.54% and 1.83%, respectively. We investigated Eulerian and Lagrangian statistics along with the stresslet exerted by the fluid on the spherical particles. It was observed that the high particle-to-fluid slip velocity close to the wall corresponds locally to events of high energy dissipation, which are not present in the single-phase flow. The migration of particles from the inner to the outer region of the pipe, the dependence of the stresslet on the particle radial positions and a proxy for the fragmentation rate of the particles computed using the stresslet have been investigated