Environmental impact assessment of the pangasius sector in the Mekong Delta

In the past seven years the export of white pangasius fillets grew fast. The culture method shifted to intensive production of striped catfish (Ca Tra) in deep ponds because this is more efficient than the pen and cage culture of Ca Basa. Today, striped catfish comprises more than 90 % of the culture. The increased production was achieved by producers investing in large ponds. The market chain is gearing towards vertical integration. Most farms keep fish at relatively high densities of 15 to 25 fish/m3 in ponds having a depth of up to 4m, and are advised to exchange daily 20 to 40% of the water. The sustainability of the sector is threatened due to the increased environmental pressure, and hampered by the growing cost of inputs and reduced farm-gate prices of the fish. The Environmental Impact Assessment (EIA) intends to identify measures for preventing or mitigating the environmental impacts of catfish culture in the Mekong Delta. The EIA was a seven-step process during which we interacted twice with part of the main stakeholders. To build trust among the stakeholders from the sector, we conducted the scoping and goal setting with them

Potential benefits from the adoption of new groundnut varieties in northern Vietnam: An ex ante assessment

Enabled by land reforms and fuelled by technological change, agricultural production in Vietnam grew tremendously after the mid-1980s. Focusing on groundnut, an export-oriented cash and food crop, this paper provides estimates of potential benefits from the adoption of improved varieties in northern Vietnam. At farm level, switching over to improved varieties generates additional revenue of VND1.8 to 3.9 million per hectare (US$1 is equivalent to about VND15,969). The aggregate benefits for northern Vietnam are huge. With the groundnut area remaining unchanged, the annual value of benefits from the adoption of improved varieties in 80$35.8 million) at a real discount rate of 5%. These benefits will be 14% larger if the groundnut area continues to expand at the rate achieved in the recent past

Rainfall variability and internal migration: the importance of agriculture linkage and gender inequality

This paper investigates the extent to which exposure to climate volatility can in-fluence individual migration decisions in Vietnam, based on the historical rainfall data from 70 weather stations in Vietnam and the Vietnam Access to Resources House-hold Survey. Utilizing the exogenous variation in the rainfall deviation from the local norms within an individual fixed-effects framework, we uncover the negative associa-tion between rainfall and the probability of individual migration. Individual migration probability drops by 7.5 percentage points when the amount of rainfall relative to the long-run local average doubles. This reduction could potentially be driven by individ-uals who work in the agricultural sector and are less likely to migrate as more rainfall could increase their agricultural incomes. Furthermore, our heterogeneity analyses sug-gest that rainfall shocks could perpetuate gender inequality in Vietnam since women cannot cope with climatic shocks through migration. Policy-makers could shift their focus on flood control and water management in affected areas, where people’s liveli-hoods depend on agriculture, to efficiently address issues related to climate-induced internal migration

Stability of the Scalar Potential and Symmetry Breaking in the Economical 3-3-1 Model

A detailed study of the criteria for stability of the scalar potential and the proper electroweak symmetry breaking pattern in the economical 3-3-1 model, is presented. For the analysis we use, and improve, a method previously developed to study the scalar potential in the two-Higgs-doublet extension of the standard model. A new theorem related to the stability of the potential is stated. As a consequence of this study, the consistency of the economical 3-3-1 model emerges.Comment: to be published in EPJ C, 13 page

Generating Neutrino Mass in the 331 Model

A mechanism for generating small tree-level Majorana mass for neutrinos is implemented in the 331 Model. No additional fermions or scalars need to be added, and no mass scale greater than a few TeV is invoked.Comment: LaTex, 7 pages, no figures. Revised version to appear in Phys. Rev.

Two-body Z′Z' decays in the minimal 331 model

The two-body decays of the extra neutral boson Z_2 predicted by the minimal 331 model are analyzed. At the three-level it can decay into standard model particles as well as exotic quarks and the new gauge bosons predicted by the model. The decays into a lepton pair are strongly suppressed, with $Br(Z_2 --> l^+l^-) ~ 10^{-2}$ and $Br(Z_2 --> \bar{\nu}_l \nu) ~ 10^{-3}$. In the bosonic sector, Z_2 would decay mainly into a pair of bilepton gauge bosons, with a branching ratio below the 0.1 level. The Z_2 boson has thus a leptophobic and bileptophobic nature and it would decay dominantly into quark pairs. The anomaly-induced decays $Z_2 --> Z_1\gamma$ and $Z_2 --> Z_1Z_1$, which occurs at the one-loop level are studied. It is found that $Br(Z_2 --> Z_1\gamma) ~ 10^{-9}$ and $Br(Z_2 --> Z_1Z_1) ~ 10^{-6}$ at most. As for the $Z_2 --> W^+W^-$ and $Z_2 --> Z_1H$ decays, with H a relatively light Higgs boson, they are induced via Z'-Z mixing. It is obtained that $Br(Z_2 --> W^+W^-) ~ 10^{-2}$ and $Br (Z_2 --> Z_1H) ~ 10^{-5}$. We also examine the flavor changing neutral current decays $Z_2 --> tc$ and $Z_2 --> tu$, which may have branching fractions as large as $10^{-3}$ and $10^{-5}$, respectively, and thus may be of phenomenological interest.Comment: 14 pages, 3 figures, submitted to Physical Review

Chromomagnetic Dipole Moment of the Top Quark Revisited

We study the complete one-loop contributions to the chromagnetic dipole moment $\Delta\kappa$ of the top quark in the Standard Model, two Higgs doublet models, topcolor assited technicolor models (TC2), 331 models and extended models with a single extra dimension. We find that the SM predicts $\Delta\kappa = - 0.056$ and that the predictions of the other models are also consitent with the constraints imposed on $\Delta\kappa$ by low-energy precision measurements.Comment: 20 pages, 5 figures, Updat

Scalar Potential Without Cubic Term in 3-3-1 Models Without Exotic Electric Charges

A detailed study of the criteria for stability of the scalar potential, and the proper electroweak symmetry breaking pattern in some 3-3-1 models without exotic electric charges is presented. In this paper we concentrate in a scalar sector with three Higgs scalar triplets, with a potential that does not include the cubic term, due to the presence of a discrete symmetry. For the analysis we use, and improve, a method previously developed to study the scalar potential in the two-Higgs-doublet extension of the standard model. Our main result is to show the consistency of those 3-3-1 models without exotic electric charges.Comment: 19 page