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Vietnam is undergoing a forest transition stage with an overall increase in forest cover since the 1990s; however, deforestation and forest degradation of natural forests still occur in several areas, especially in the Central region of the country. In order to better manage and protect natural forests, predicting deforestation probability and understanding its associated factors are necessary. In the present study, we focused on the two mountainous districts (Nam Dong and A Luoi) in Central Vietnam as a case study. We used Landsat satellite images for identifying changes of natural forests over the period of 1989–2020. The logistic regression model showed a good performance in prediction of deforestation (testing AUC = 0.874) in the study area. Our data showed that deforestation probability of natural forests in the study area in the period of 1989–2020 could be influenced by 11 socio-economic and topographical factors. In particular, forest areas with low elevation, gentle slopes, nearby rivers and residential areas have a high deforestation probability. Production forest, forest areas not included in payment for environmental service (PFES) schemes, forest with no ownership and forest areas managed by private owners may also have a high deforestation probability. The total area of very high level of deforestation probability in A Luoi (8,988 ha) and Nam Dong (5,304 ha) districts occupied about 11.4% of natural forests in the study area. Our study suggests that protection activities should be focused on high deforestation probability-prone forest areas.

Porcine epidemic diarrhea (PED) is known as a serious disease infecting all ages of pigs, with a mortality rate of up to 100% in piglets. The spike protein (S) of porcine epidemic diarrhea virus (PEDV), in particular, the S1-CTD (C-terminal domain), which contains the conservative neutralizing epitopes CO­26K equivalent (COE) (aa 499–638), exhibits a high degree of genetic and antigenic diversity. We obtained 26 Vietnamese PEDV-S1-CTD sequences (630 bp) from samples collected from seven northern provinces from June 2018 to January 2019 and analyzed them with 35 sequences from previous studies, representing the G1a and 1b, G2a and 2b, and recombinant (G1c) genotypes, and PEDV vaccines. The majority (73.1%) of strains (19/26) belonged to the subgroup G2b. With strong nodal support (98%), seven strains were clustered into an independent, “distinct subgenogroup” (named dis-subG), separate from both G1a and G1b and other G2a, 2b, and 1c (recombinant strains). When compared with the prototype CV777 strain (AF353511), sequence analysis revealed distinct changes of 513T>S, 520G>D, 527V>(I/L/M), 591L>F, 669A>(S/P), 691V>I in the COE and S1D regions of the S1-CTD protein that were only identified in these Vietnamese strains. This cluster is a new antigenic variant subgroup and further studies are required to investigate its anigenicity. The results in this study revealed the continuous evolution in the S1 region of the Vietnamese PEDV strains, which emphasizes the need for frequent updates of the vaccines for effective protection.

Trade facilitation plays a key role in international trade and trade supply chains, which is also an important issue of the world in general and Vietnam in particular. The new WTO Trade Facilitation Agreement (TFA) is a significant step forward for the international trading regime, representing new hope for the relevance of the WTO Keywords

A clinical trial of measles and rubella combined vaccine (MR: MRVAC) produced by POLYVAC was conducted in Vietnam in 2016. A total of 756 subjects were enrolled, and 504 were allocated to MRVAC and 252 to control MR vaccine groups. Paired sera were obtained in 733, and the number of subjects was 403 aged 1 - 2 years, 164 aged 2 - 18 years, and 166 aged 18 - 45 years. Antibodies against measles and rubella viruses were evaluated by EIA. Most subjects had been immunized with a single dose of Expanded Programme on Immunization (EPI) measles vaccine at 9 months of age. Only 41 of 403 subjects aged 1 - 2 years were negative for measles antibody before vaccination, and all became seroconverted. A serological response of more than a 2-fold increase against measles was noted in 214 (47%, 95% CI; 42.4% - 51.6%) of 458 initially seropositive individuals immunized with MRVAC and 65 (28%, 95% CI; 22.3% - 33.8%) of 234 in the control group, and geometric mean titer (GMT) after vaccination was 25.49-5.60 in MRVAC and 25.03-5.24 in control group. Seroconversion against rubella virus after immunization with MRVAC was noted in 267 (98.5%, 95% CI; 97.1% - 100%) of 271 initially seronegative subjects, similar to that after immunization with control group. GMT after immunization with MRVAC was 24.88-5.11 significantly lower than that after immunization with control vaccine (25.59-5.80). Most subject ≥ 2 years of age had rubella antibody because of MR vaccination campaign and no significant serological response was observed in initially seronegatives. MRVAC was highly immunogenic and safe vaccine and the domestic production of MR vaccine would contribute to realizing the goal of eliminating measles and rubella.

Forward osmotic (FO) membrane is a new process for producing fresh water from salt water. The study of draw solute is essential in the development and application of FO technology; draw solution should be good at drawing water and easy at recovery. In this paper, three complex draw solutes such as ammonium iron (II) sulfate, ammonium iron (III) sulfate and ammonium iron (III) citrate with different concentrations were studied. The physical properties such as pH, conductivity and total dissolved solids (TDS) have simultaneously been investigated. The pH of most ammonium complexes was decreased whereas TDS increased with increasing of draw solution concentrations. We found that high water flux of these iron complexes was reported in the range of 8.88–11.24 LMH which was higher than the ammonium bicarbonate draw solution. In addition, more than 90% iron complexes draw solutions were recovered by NF-90 membrane, which plays an important role in the FO process to produce fresh water. This study provides direct evidence for the ability of permeate water from feed solution to draw solution, which shows the potential applications of iron complexes in FO process to produce fresh water from sea-, brackish or river water.

application/pdf, 学位記番号：論工第1628号, 主査：古田 雅一