Vietnam Journal of Science, Technology and Engineering

7-13

Authors: Quoc Hung Nguyen*, Van Hai Chu, Ngoc Cuong Hoang, Van Huong Pham

The production of natural latex is limited, and the related demand for terrestrial transportation has increased. The synthesis of rubber has become necessary and the resulting synthetics’ properties must be known. Thermo-oxidative degradation of synthetic rubbers 1,4- and 1,2-polybutadienes caused by heating the compounds at 100°C in the air, was monitored. The volatile compounds released during the degradation were identified using coupled modern physical methods, including NMR, TGA, MS, FTIR, etc.. Thermal gravimetric analysis showed that oxidation occurred for both 1,4 and 1,2-PB. Below 400°C, major functional groups were formed, including peroxides, ketone, aldehyde, ester, etc.. Oxidation was found to start on the methylene (CH2) carbon of 1,4-PB and on the methylene (CH2) and methine (CH) carbons of 1,2-PB. The polycyclohexane-like structures were identified resulting from the oxidation of 1,2-PB. Above 400°C, the main resulting compounds were carbon dioxide, carbon monoxide, water, and some hydrocarbons and aromatics. Radical mechanisms for thermo-oxidative degradation of 1,4 and 1,2-PBs were proposed.

20-24

Authors: Thi Thao Nguyen*, Masayoshi Sawamura

A refined analytical method has been developed for the determination of the isotope ratio of oxygenated compounds in essential oils, using high-resolution gas chromatography-mass spectrometry (HRGC-MS), has been developed. Thirty-three samples of yuzu fruits from different production areas in Japan and South Korea were collected and prepared for cold-pressed peel oils. The oils were analysed by HRGC-MS for linalool concentration and isotope ratio based on the peak intensities of (M+2)+, (M+1)+ and M+ ions. A significantly lower isotope ratio m/z 156/154 and m/z 155/154 were observed for the yuzu essential oil from Goheung and Kyoto areas. Statistical analysis showed the isotope ratio of linalool to be useful in the discrimination of yuzu essential oils from different geographical origins.

32-38

Authors: Thanh Vu Pham*, Hieu Trung Nguyen, Tuan Huy Vuong, Pham Dang Tri Van, Quang Tri Le

Agriculture is a primary source of livelihood in the Vietnamese Mekong River Delta with different land use activities. There are different potential conflicts in agricultural land use, including: water resources use and interests. Therefore, establishing feasible land use planning (LUP) in an area needs an in-depth participation and discussion among stakeholders (including: governments at different levels, local farmers, and national and international scientists). Indigenous knowledge of local farmers plays an important role in making land use decision, which can support solving land-use conflicts to achieve the most sustainable management of land resources. In this study, we integrated local knowledge into a land use planning process to assess the suitability of land use types and to project potential impacts of climate change conditions on land use decisions in the Tra Hat hamlet, one of the climate-smart village (CSV) sites in the Vietnamese Mekong River Delta. A total of two consultation meetings, using simple tools (resources mapping, timeline, seasonal calendar, wealth ranking, Venn diagram, pair wise ranking, and key informants’ interviews), were conducted, and 130 households were interviewed during a field visit in 2015. As a result, a participatory land use planning (PLUP) was implemented with active participation of the concerned communities to establish a suitable land use planning and identify the potential adaptation techniques in the near future (2020). Land use planning at the hamlet was discussed to get the agreement and the coordination among local governments, farmers and scientists on adaptation practices.

44-47

Authors: Thi Nguyen Duong*, Thanh Van Dao

Cinnamon (Cinnamomum cassia B.) is an important crop in Vietnam for domestic consumption and exportation. In recent years, a disease known as cinnamon witches’ broom (CinWB) has been discovered on cinnamon grown in Tra Bong district - Quang Ngai province. The typical symptoms of CinWB were the formation of small tumors on the stems, branches, petioles, and veins of plants. The tumors become long squid-like tassels giving the appearance of a witches’ broom. Infected plants are stunted, with delayed growth and development, causing a high reduction in the yield and quality of farmed cinnamon. In the present study, nested-PCR was applied with the universal primer pairs P1/P7 and R16F2n/R16R2. PCR products of an approximate size of 1200 bp were amplified from the twelves CinWB-showing samples collected from Tra Bong district, Quang Ngai province. All PCR products were directly sequenced in both directions using R16F2n and R16R2 primers. A BLAST search indicated that DNA sequences of all 12 PCR products were identical and show 99% identity with phytoplasma sequences of the 16SrXIV group. And the CinWB phytoplasma isolated from the CinWB-showing cinnamon from Tra Bong district - Quang Ngai province (QQNVN) was deposited in GenBank under an accession number JX413793.

53-59

Authors: Huu Tho Ho*, Nguyen Quynh Anh Vu, Tram Anh Do, Dinh Ung Nguyen, Thi Thu Hang Dinh, Tien Sy Bui, Dao Chinh Hoang, Minh Ky Le, Truong Phong Vu, Thanh Tung Ngo, Kim Luu Nguyen, Truong Sinh Luu, Van Ba Nguyen, Anh Son Ho, Van Luong Hoang, Duc Thuan Nghiem

In Vietnam, nasopharyngeal carcinoma (NPC) is the eighth most common cause of death from cancer. Cell-free Epstein Barr virus DNA (cf-EBV DNA) was reported to be present in almost all NPC patients. However, currently available assays in Vietnam can detect cf-EBV DNA in only 67.6% of NPC patients, thus leaving 32.4% of cancer cases undetected. Therefore, in this study, we aim to develop a highly sensitive quantitative PCR (qPCR) assay that measures the load of cf-EBV DNA for the purpose of early detection of NPC, and then evaluate the sensitivity and the specificity of the developed qPCR assay on the clinical samples. The major methods used in this study include primer/TaqMan probe design, cf-DNA extraction, optimization of qPCR assay and statistical analysis. Using an international standard panel from the Chinese University of HongKong, the linear range of developed qPCR assay is from 50-150,000 copies/ml (R2 = 0.99613) and the detection limit has been shown to be 25 copies/ml. The developed assay could detect cf-EBV DNA with a sensitivity of 96.9% (31/32 NPC patients) and cf-EBV DNA has not been detected in 103 out of 105 healthy controls, which corresponds to a specificity of 98%. Consequently, the performance of the optimal assay has achieved remarkably high sensitivity and specificity. Moreover, the detection limit of our optimal qPCR assay is 25 copies/ml of plasma, which is at least ten times better than other assays tested in recent studies in Vietnam. This developed qPCR assay will also form the basis for further studies in Vietnam and will open many new applications in management of NPC.

65-70

Authors: Minh Hoang Cu*, Khac Hoan Phung, Hai An Le

Southeast Asia has 11 countries: Brunei, Cambodia, East Timor, Indonesia, Laos, Malaysia, Myanmar, Philippines, Singapore, Thailand, and Vietnam. Southeast Asia is considered one of the most active economic development regions in the world, with high demand for energy development, cultural diversity, and language. These countries and Vietnam have good relationships in diplomacy and cooperation and in other fields; therefore, it is very convenient for Vietnam to invest in oil and gas exploration and exploitation in the region. On the basis of evaluating the criteria of natural conditions, geological features, sedimentary basins, exploration and exploitation status as well as investment environment of each country in Southeast Asia, this article will introduce the most comprehensive information about the potential and the overall picture of the oil and gas industry in Southeast Asia and in individual countries, thereby providing information and orientation for investment opportunities of each country in the region

85-90

Authors: Quoc Huy Le, Thuc Tran, Xuan Hien Nguyen*, Van Uu Dinh

Our study applied the Ensemble Empirical Mode Decomposition (EEMD) method to analyze intraseasonal variability (ISV) of sea surface temperature (SST) and wind speed using a 22-year monitoring data set from 10 coastal stations. Results show that the El Niño and Southern Oscillation(ENSO) significantly affected the ISO Quasi-Biennial Oscillation (QBWO) 10-20 day periods and Madden-Julian Oscillation (MJO) 30-60 day periods of SST and wind speed at the coastal stations. As seen with MJO, the effects of ENSO on SST tend to increase from the north to south, whereas its impact on wind speed decreases from the north to south of Vietnam’s coastal areas. In contrast, with QBWO, the effect of ENSO on SST reduces moving from the north to south, whereas its impact on wind speed increases from the north to south of Vietnam’s coastal areas.