This paper investigates Vietnam's scientific publications between 1996 and 2013 from Scopus database, focusing on international collaboration. The total scientific output of the country increased about 16 publications per year during 1996-2001 and quickly increased 20 % per year during 2002-2013. However, the share of international collaboration was about 77 % of the total output. Biological and agricultural science, medicine dominated the total output, but 80-90 % of these publications are from international collaboration. In contrast, mathematics is the only field that domestic output is larger than collaboration output. Japan is the largest collaborating country, followed by United States, France, South Korea and United Kingdom. Analyzing titles of publications with these collaborating countries, we found high frequency of ''Vietnam'' or ''Vietnamese'' words. This result suggested that many study subjects of these research collaborations were from Vietnam. Furthermore, corresponding authors of these research collaborations are mainly from collaborating countries, which suggested that these research collaborations mainly led by foreign authors. Although the total output was quickly increased, especially collaboration output, Vietnamese researchers should be aware about their low contribution to these collaborations.

The larvicidal activity of essential oils (EOs) extracted from Cymbopogon citratus, Cymbopogon winterianus, Eucalyptus citriodora, and Eucalyptus camaldulensis aromatic plants grown in Vietnam was evaluated on Aedes aegypti larvae. The EOs were hydro-distilled in a Clevenger-type apparatus. The EOs were analyzed by gas chromatography-mass spectrometry (GC-MS). The mortality rates obtained from the bioassays were used to calculate the lethal concentrations (LC 50 ) of the EOs by the probit analysis method. These essential oils exhibited toxicity to the larvae of Aedes aegypti. Results were obtained for Cymbopogon citratus (LC 50 = 120.6 ppm), Cymbopogon winterianus (LC 50 = 38.8 ppm), Eucalyptus citriodora (LC 50 = 104.4 ppm), and Eucalyptus camaldulensis (LC 50 = 33.7 ppm). The essential oils of Eucalyptus camaldulensis and Cymbopogon winterianus were found to be the most efficient, and their respective values of LC 50 were 33.7 ppm, 38.8 ppm. In conclusion, this research adds to the growing body of literature on natural larvicides from essential oils against Aedes aegypti mosquitoes.

Recent studies have found elevated dioxin levels inside some U.S. military former air bases in Vietnam, known as hotspots. Many studies of Agent Orange have been done in U.S. veterans; however, there is little known about Vietnamese men. In 2010, we collected blood samples from 97 men in a hotspot and 85 men in an unsprayed area in Northern Vietnam. Serum concentrations of not only TCDD but also other dioxins (PCDDs), furans (PCDFs), and nonortho polychlorinated biphenyls (PCBs) were significantly higher in the hotspot than in the unsprayed area. In the hotspot, three subareas were demarcated, based on their proximity to the air base. The total toxic equivalents (TEQ) of PCDDs/PCDFs+PCBs was 41.7 pg/g lipid in the area closest to the air base, while it was around 29 pg/g lipid in the other two subareas. In the unsprayed area, the dioxin levels were no different between men who went to the South during the Vietnam War and those who remained in the North, with TEQs PCDDs/PCDFs+PCBs of around 13.6 pg/g lipid. Our findings suggested that people living close to the former U.S. air bases might have been exposed to both Agent Orange and other sources of dioxin-like compounds.

Dengue is one of the most dangerous vector-borne diseases transmitted by Aedes mosquitoes. The use of mosquito repellents to protect human hosts and insecticides to reduce the mosquito population is a crucial strategy to prevent the disease. Here, we reported larvicidal and repellent activities of Mentha arvensis L. essential oil against Aedes aegypti, the main vector of the disease. The essential oil was extracted by hydro-distillation from the aromatic plant grown in Vietnam. The yield was 0.67% based on the weight of fresh leaves. The essential oil was analyzed by gas chromatography-mass spectrometry (GC-MS). The main components were menthol (66.04%), menthyl acetate (22.19%), menthone (2.51%), and limonene (2.04%). Toxicity test on Aedes aegypti larvae showed that the median lethal concentrations, LC50 and LC90 were 78.1 ppm (part per million) and 125.7 ppm, respectively. Besides, the essential oil showed excellent repellency on Aedes aegypti mosquitoes. At 25%, 50%, and 100% concentration, the respective complete protection times (CPTs) were 45 min, 90 min, and 165 min. When adding 5% vanillin to the essential oil (25%), the complete protection time of the essential oil increased up to 120 min. In conclusion, the EO from Mentha arvensis L. has been shown to be a promising natural larvicide and repellent against Aedes aegypti mosquitoes.