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.

5-9

Authors: Nhan Ba Dam, Van Tuan Chu, Anh Tuan Do, Quyet Thang Le

In this work, we study the influence of the substitution Si for Ni for the magnetic properties of LaNi5-xSix (x = 0-0.5) alloys. The structure of the alloy was tested by X-ray diffraction (XRD) measurements. The magnetic properties of the samples were carried out using a vibrating sample magnetometer (VSM) system. The results showed that when Ni was substituted for Si in alloys and after hydrogen absorption, LaNi5-xSix alloys retained their CaCu5 structure. The susceptibility (χ) of the alloys decreased when substituting Ni by Si increased. The original bulk samples showed a Pauli paramagnetism state after hydrogen absorption transformed into a superparamagnetic state. The results obtained showed that although measurements of magnetic characteristics are relatively simple, quantitative information about the microscopic processes occurring in the material was used as the negative electrode in Ni-MH rechargeable battery.

14-21

Authors: The Anh Nguyen, Truong Giang Vu, Thi Lan Nguyen, Quang Trung Pham, Thi Thao Ta

Honey is a natural, sweet, and syrupy fluid which has been used in Vietnam in a variety of ways; as a food supplement, beauty product, and natural drug. However, quality control and characterization of honey are blind problems. Consumers, and even market management committees, must believe in the producer’s quality standards without using any special techniques to evaluate the botanical origins of honey in the Vietnamese market. The chemical composition and physical properties of natural honey vary per plant species of which the honey bees scrounged. Longan flower-honey has a high price and is commercially produced in Yen Bai, Bac Giang, and the more well-known Hung Yen Province in Vietnam, and now is being confused with original flower honey. In this work, a total of 57 honey samples (longan and non-longan) from different geographic and botanical origins have been analysed in terms of 1H-NMR spectroscopy, coupled also with multivariate statistical analysis methods. Principal component analysis followed by icoshift algorithm analysis comes about as a proficient device in recognising 1H-NMR spectra of longan honey samples.

30-33

Authors: Chi Buu Bui, Thi Lang Nguyen

Although Vietnam is the second largest rice exporter in the world, the country has only recently met the demand for sustainable food supply at a national level, and not yet at a household one. In the early 1970s, the average rice yield in the Mekong River Delta (MRD) was 1.9 tons/ha and the annual production weighed 4 million tons. The current rice productivity and production has gained over 6 tons/ha and 24 million tons/year, respectively. This is a substantial increase. This progress in the MRD is in brief, due mostly to (1) Governmentpolicy, (2) Water management, and (3) Technological innovation and application with an emphasis on varietal improvement. As an impact of the ongoing El Nino Southern Oscillation (ENSO) phenomenon, severe droughts and salinity intrusion has been occurring in Vietnam’s MRD and has caused varying degrees of damage to agriculture, fisheries and the livelihoods of people in the region. New rice genotypes have been released via both conventional breeding and marker-assisted selection. The introgression of target genes from wild species viz. Oryza officinalis, O. australiensis, O. rufipogon into cultivars has been conducted successfully. Commercial rice varieties, which are currently growing in the MRD for export, are listed as Jasmine 85, OM3536, OM4900, IR64, OM6162, ST3, ST5...

39-42

Authors: Huu Hung Nguyen, Van Vang Luong, Thi Minh Tam Ngo, Hoai Son Vu, Xuan Thang Nguyen

This study was conducted at the Maize Research Instituteof Vietnam using 24 maize hybrids, identified as STM1 to STM24, at five different salt concentrations, which were 0, 50, 100, 150, and 200 mM NaCl. After seven days of germination at room temperature, seedlings were transplanted to nutrient-rich solutions salinized with salt. 17 day-old seedlings were then harvested to calculate their growth parameters of the day to seedlings fully wilt and degradation, root and shoot length, seedling dry matter production, and content. As the study results show, salt stress caused the reduction of plant growth in all hybrids, however, the STM10 and STM21 varieties showed the best salt tolerance, while STM17 and STM18 presented most salt-sensitive. The analyzed results for Na+ and K+ showed that among the hybrids, STM21 had lower Na+ and higher K+ contents in both roots and shoots of the seedlings than others.

48-52

Authors: Nhu Hiep Pham*, Huu Thien Ho, Anh Vu Pham, Hai Thanh Phan, Thanh Xuan Nguyen, Xuan Dong Pham, Tien Nhan Van, Nghiem Trung Tran, Trung Vy Pham, Si Doan Diem Tran, Trung Hieu Mai, Le Minh Chau Dao

Objective: Natural Orifice Transluminal Endoscopic Surgery (NOTES) is an important evolution in minimally invasive surgery (MIS) nowaday. This paper presents the techniques and early results of the pure transanal and transvaginal laparoscopies (NOTES) used for the treatment of colorectal cancer.Material and method: Prospective studies were conductedat Hue Central Hospital, Vietnam.Patients: From December 2013 to September 2015, 22 cololorectal cancer patients (18 rectum, 3 sigmoid tumors and 1 descending colon), adenocarcinoma, T≤ T3N1M0. Methods:The patients were placed in lithotomy and Trendelenburg positions, and the lone-star retractor was placed in the anus (rectum cancer) or vagina (sigmoid cancer). The surgical cavity was then inflated with CO2 and set at 12 mm/Hg. Dissection was continued until inside of the abdominal cavity (transanal technique). After that, the rectum was pushed into the abdominal cavity. The IMA and IMV were divided (TME included) in both techniques. After finishing dissection, the specimens were pulled out through the anus or vagina to prepare anastomosis. Coloanal and colorectal anastomosis were either hand-sewn (6 cases) or sealed with EEA staplers (16 cases). Results: 2 patients needed one more 5 mm umbilical port in RLQ, 2 patients needed two 5 mm trocars (post radiation hemorrhage, and urethral perforation). One patient converted to open and 1 patient converted to the HYBRID-NOTES procedure. The operation time was 258±40 (190-300) minutes. All patients required minimal analgesia. Bowel movement returned on the first day to 16 patients (average: two days, maximum: three days). The hospital stay was 7±2.8 (4-14) days. Kirwan classification (sphincter function) was very good (stage I: 18). Conclusions: Pure transanal and transvaginal laparoscopies for the treatment of colorectal cancer are feasible and safe. We believe that this is the first pure transvaginal laparoscopy (NOTES) for human in the world. A multicentric study in a large numbers of patients and a long follow-up is necessary.

56-61

Authors: Thi My Yen Nguyen, Xuan Quang Ngo*

Sub-tidal free-living nematodes in 12 stations along the Saigon River were investigated in both dry and rainy seasons during 2014 and 2015. In total, 157 nematode genera were found to belong to 59 families, and 11 orders of two classes of Enoplea and Chromadorea were identified. The trophic structure of free-living nematode communities was analysed spanning the overall seasons to see that deposit-feeders developed dominantly in the Saigon River indicating their association with food types including particles, bacteria, diatom, etc.. The dominance of deposit-feeders was contributed to a high abundance of genera in each station, including Theristus, Teschellingia, Monhystera, Thalassomonhystera, Paraplectonema, Daptonema, Aphanonchus, Sphaerotheristus, and Geomonhystera. Epistrate-feeder types were found as the second most abundant group. The remaining feeding types, such as chewers and suction-feeders, were in rather low proportion at most stations.

76-82

Authors: Hong Thien Van, Phi Nga Nguyen, Ngoc Toan Tran, Hong Truong Luu*

Alocasia rivularis (Araceae) is proposed as a new species from central Vietnam. The new species is morphologically similar to those of the Cuprea Group of Alocasia, but according to results of the trnL-trnF IGS and matK sequences, and based on morphological differences, it is clearly different from the closest congeners. Phylogenetic analysis, descriptions, and illustrations are provided.

88-91

Authors: Duc Ngu Nguyen*

This paper presents a summary of the results of a study into the effects of ENSO (El Niño and La Niña) on the frequency of cold fronts and tropical cyclones affecting Vietnam. The results show that, during the ENSO periods, cold air activities affecting Vietnam were reduced. The ratio of total positive anomalies to negative anomalies of front frequency was 68% in the case of El Niño, and 60% in the case of La Niña. The frequency of tropical cyclones affecting Vietnam decreased by 28% in the case of El Niño, and increased to 38% in comparison with the multi-year average in the case of La Niña. During the El Niño period, hurricanes affecting Vietnam were often evenly distributed or concentrated in the first half of the typhoon season, but during the La Niña period, hurricanes were concentrated in the second half of the hurricane season.

6-9

Authors: Anh Tuan Pham

Vietnam has spent a considerable amount of money to install a satellite exploration program. This article presents the most important achievements of the implementation of this program in Vietnam and gives recommendations for supportive policies that will allow for the development of space exploration in the future.

14-17

Authors: Van Nghia Tran

This paper presents the implementation of RGB↔YCbCr color space conversion circuits (IP-cores) necessary for many video designs. These IP-cores offer simplified 3x3 matrix multipliers used to convert three input color samples (RGB or YCbCr) to three output samples (YCbCr or RGB). The optimized structure of IP-cores uses only four multipliers (or XtremeDSP slices) to implement the RGB↔YCbCr transformation by taking advantage of the dependencies between coefficients in the conversion matrix. Parameterizable IP-cores are used to confirm compliance to multi-standards and optimize hardware implementation. IP-cores have been verified successfully using xilinx vivado system generator 2016.2 for visually inspected output results and for verification against known models in the MATLAB/Simulink software environment.

27-31

Authors: Anh Thu Quang, Cong Thanh Vo

In order to detect some of the determinants of rice flavor, an experiment was carried out that studied panicle primordia at the initial panicles of three aromatic varieties: Nang Thom Cho Dao mutation (NTCDm), Thom Bay Nui (TBN), and Jasmine-85, and IR28 was used as the control variety (non-aroma). The samples were dyed from the primordium stage to the ripe-pollen stage. Results showed that there were two key differences between the aromatic rices and the control. The first point of difference was at the primordium stage, and the second was after, as a consideration of the number of bivalents (pairs of homologous chromosomes). As for the three aromatic rice varieties, there appeared a lobe division at the branch primordium; at the diplotene stage of meiosis, and seven to eight stained bivalents appeared while the control had no lobe division and the number of stained bivalents achieved 11 to 12

36-42

Authors: Dinh Kha Le, Huy Thinh Ha

“Acacia hybrids” refers to the inter-specific hybrids of A. mangium and A. auriculiformis, including natural, artificial and polyploid ones. The superiorities of selected acacia hybrid are fast growth, straight stem form, small branches, high productivity, and high ratio of wood utilisation. Acacia hybrids are recognized as having a higher pulping potential and greater soil improvement ability than that of the parental species, which may be shown to have 2.5-13 times larger numbers of nitrogen - fixing nodules on its roots in nursery stage. Mass propagation technology using both cutting and tissue culture has been successfully developed for acacia hybrid, enabling large-scale clonal forestry to improve plantation productivity and quality. The area of acacia hybrid plantations up to 2016 was estimated to be 500,000 ha, with an annual increase of 30,000-35,000 ha, making it the most widely planted forest tree variety in Vietnam. Acacia hybrids and propagation technologies have also been introduced in Malaysia, Indonesia, Thailand, Laos, and Cambodia. The research and development of acacia hybrid breeding can be considered as a revolution in the forestry sector and has created new and advanced approaches for both research and training in tree breeding in Vietnam.

49-53

Authors: Ngoc Ha Le, Hong Son Mai, Van Nguyen Le, Quang Bieu Bui

Objective: To assess metabolic tumor response using 18F-FDG PET/CT scan in early stage non-small cell lung cancer (NSCLC) treated by CyberKnife radiosurgery. Materials and Methods: 30 patients were diagnosed proven by biopsy and inoperable stage I NSCLC, and were enrolled into this study. 18F-FDG PET/CT was performed prior to the program, and at three months following the radiosurgery treatment. The tumor maximum standardized uptake value (SUVmax) was recorded for each time point and the PERCIST criteria was applied to assess tumor response. Results: 30 patients with NSCLC, stage me after CyberKnife radiosurgery was followed-up after 12 months. The 1-year Kaplan-Meier local control estimate was 96.7%, the cut-off of SUVmax was 10, and revealed the local tumor control to have a statistically significant difference. Mean tumor SUVmax before treatment was 10.5±3.25 (range, 5.0 to 20). During early follow-up the mean SUVmax in the tumor remained high due to peritumoral radiation-induced pneumonitis visible on CT imaging. After radiosurgery for six months, 18F-FDG PET/CT images showed that 21 of 30 patients (70%) had a partial metabolic response, 8 of 30 patients (26.7%) had stabilized diseases, and one patient (0.3%) had disease progression. Meanwhile, CT could not reveal the progressed patient. Conclusions: Local control following CyberKnife radiosurgery for stage I NSCLC is acceptable. Transient increases in tumor SUVmax are likely related to radiation-induced pneumonitis. The value of 18F-FDG PET/CT imaging for early metabolic tumor response after stereotactic body radiation therapy (SBRT) could be higher than anatomic response on CT.

58-72

Authors: Van Hieu Nguyen

During the present decade application-oriented basic research on nanomedicine has rapidly developed in Vietnam. This work is a review of this development. It was directed towards following scientific topics: Biomedical utilization of PLA-TPGS and PLA-PEG, dendrimer-based anticancer drugs, special drug delivery nanosystems, various utilizations of nanocurcumin in nanomedicine, biomedical application of hydrogel nanocomposites, biosensors and biosensing methods, toxicity and antibacterial activity of different types of nanoparticles. Obtained scientific results demonstrated that although Vietnamese application-oriented basic research on nanomedicine began to develop only in this decade, it has achieved very promising successes.

79-87

Authors: Van Thang Nguyen, Van Khiem Mai, Van Thang Vu, Dang Mau Nguyen, Ngoc Bich Phuong Nguyen, Duy Diep Le, Truong Minh Ha, Nhat Linh Luu

This study represents the observed and projected changes in climate extremes in the context of climate change. A linear regression method was used to identify trends and variations of climate extremes in the past, while projected changes in climate extremes were detected based on dynamical downscaling and compared with the baseline period (1986-2005). The results show that daily maximum and minimum surface air temperatures (Txx, Tnn) increased considerably with the highest value of about 0.9oC/decade during the period of 1961-2014. The number of hot days increased across most observed stations, especially in Central Vietnam. Trends of extreme precipitation varied among the regions: decreasing across most stations in the Northwest, Northeast and Red River Delta; and increasing at other stations. In Vietnam, over the period 1959-2015, there were no obvious changes in the frequency of tropical cyclones causing landfall events, including typhoons and tropical depressions. However, the rate of occurrence of the very strongest typhoons are currently on the increase. In recent years, typhoon seasons tend to end later than in the past, and typhoons occur more frequently in Southern regions. Predicted results of climate extremes in the future for the periods 2046-2065 and 2080-2099, compared with the baseline period of 1986-2005 under the medium and high scenario (RCP 4.5 and RCP 8.5) show that temperature extremes will likely increase considerably in the future. The number of hot days will likely increase in both frequency and intensity, while the number of extreme cold days will likely decrease at most stations in the North. A maximum 1-day rainfall will also likely increase across all regions in Vietnam. Results from models show that the number of strong typhoons will likely increase in the mid- and late-century.

93-96

Authors: Ngoc Anh Nguyen

During the dry season of 2015-2016, the Mekong Delta had suffered the worst historic drought and salinity intrusion occurrence on record, causing heavy damages to nine coastal provinces (in total 13 provinces) of the Mekong River Delta. Just after the drought and salinity intrusion occurred, the media offered some different opinions suggesting possible solution which offer effective responses and stable development to coastal regions. The author suggests that in order to have sustainable development for the Mekong Delta in general and for the coastal zones in particular, Vietnam needs to have some basic short-term and long-term solutions, for each region as well as the whole delta, including drought-salinity intrusion and flooding programs, structural and non-structural works, and coverage for both the Mekong Delta and the whole Mekong River Basin.