Vietnam Journal of Science, Technology and Engineering

3-16

Authors: P.N. Diep*, D.T. Hoai, N.B. Ngoc, P.T. Nhung, N.T. Phuong, T.T. Thai, P. Tuan-Anh

HD 163296 is one of the few protoplanetary discs displaying rings in the dust component. The present work uses ALMA observations of the 0.9 mmcontinuum emission, which have significantly better spatial resolution (~8 au) than previously available, to provide new insight into the morphology of the dust disc and its double ring structure. The disc is shown to be thin, and its position angle and inclination with respect to the sky plane are accurately measured as are the locations and shapes that characterise the observed ring-gap structure. Significant modulation of the intensity of the outer ring emission is revealed and discussed. In addition, earlier ALMA observations of the emission of three molecular lines, CO(2-1), C18O(2-1), and DCO+(3-2) with a resolution of ~70 au are used to demonstrate the Keplerian motion of the gas, which is found to be consistent with a central mass of 2.3 solar masses. An upper limit of ~9% of the rotation velocity is placed on the in-fall velocity. The beam size is shown to give the dominant contribution to the line widths, accounting for both their absolute values and their dependence on the distance to the central star

23-28

Authors: Thi Lan Nguyen, Tri Tin Nguyen, Hoang Tu Tran, Minh Dat Nguyen, Huu Hieu Nguyen*

In this research, graphene aerogel (GA) was fabricated by chemical reduction method, in which ethylenediamine (EDA) was used as a reducing and functionalising agent. The characterisation of GA was studied by density, field-emission scanning electron microscope, Brunauer-Emmett-Teller (BET) specific surface area, Fourier transform infrared spectroscopy, and X-ray diffraction. The results of the analysis showed that GA exhibits low density, ranging from 4-8 mg/cm3, high porosity, and BET specific surface area changes from 176 to 1845 m2/g. It was found that the suitable content of EDA on the synthesis of GA is 30 μl. The obtained GA was used as an adsorbent for removal of oils and methylene blue (MB) from aqueous solutions. The maximum adsorption capacities of GA for lubricant and crude oils are 160 g/g and 110 g/g respectively. The effecting factors including pH, contact time, and initial concentrations on the adsorption capacity of GA for MB were investigated. The adsorption process of MB onto GA followed the pseudo-second-order kinetic and well-fitted to Langmuir isotherm model. The maximum adsorption capacity for MB from linear Langmuir model was calculated to be 212.76 mg/g at pH 7. Accordingly, GA could be used as a potential adsorbent for removal of oils and MB from water

35-41

Authors: Nguyen Thi Hong Diep*, Thitinat Korsem, Nguyen Trong Can, Walaiporn Phonphan, Vo Quang Minh

Aquaculture is an important economic activity in the coastal zone of Vietnam. Thanh Phu is one the coastal districts in Ben Tre province that rears brackish aquaculture. In recent years, farmers could not grow shrimp because of salinity intrusion and market price fluctuation. This study aims to determine aquaculture and fallow aquaculture pond distribution by using the three indices of NDVI (Normalized Difference Vegetation Index), MNDWI (Modified Normalized Difference Water Index) and NDBaI (Modified Difference Bareness Index) on Landsat 8 imagery. The results reveal that remote sensing can support the detection of aquaculture and fallow ponds with a high accuracy of 77%. The total aquaculture area is approximately 13,093.65 ha, of which the total fallow area is 581.49 ha (roughly 4.44% of the total aquaculture area). Moreover, the fallow ponds are randomly distributed in all four ecological zones and mostly in the fourth ecological region (about 73.92%). In the fourth region, saline concentration in water is from 20 to 30‰, which directly influences cultured shrimp farms. The results also indicate the spatial distribution of aquaculture ponds and ineffective aquaculture locations using Landsat 8 imagery via index image analysis. The findings support the local management’s decision making on further aquaculture planning.

47-51

Authors: Duong Thi Nguyen*, Nguyen Thi Nhu Hoa, Le Thi Kieu Oanh, Dang Kim Tuyen, Nguyen Chi Hieu, Duong Son Ha, To Thi Ngan

Fusarium proliferatum has been identified as the causal pathogen of Fusarium root rot of Ba kich (Morinda officinalis) (FRRBK). No studies are available regarding the effectiveness of chemical treatments on the disease incidence of FRRBK. The efficacy of five active ingredients (metconazole, prochloraz, tebuconazole, kresoxim-methyl, and pyraclostrobin) from two chemical groups (demethylation inhibitors and quinone outside inhibitors) in reducing three isolates (BKVN, BKDT, and BKPL) of F. proliferatum mycelial growth was tested in vitro. The results indicate that only metconazole, prochloraz, and tebuconazole are highly effective in inhibiting the mycelial growth of F. proliferatum. These were selected for investigation of their efficacy with regard to the disease incidence of FRRBK in pot and in field conditions. Prochloraz and metconazole showed the highest efficacy and significantly suppressed the disease incidence of FRRBK in pot and in field conditions.

60-64

Authors: Ha Van Thieu*

Background: childhood overweight is increasingly common worldwide as are its consequences, which include increased risk of later cardiovascular disease and diabetes. Although metabolic syndrome (MetS) has been extensively studied in adults, not much is known about the condition in children and adolescents. MetS and its individual components are detectable during childhood, and both commonly persist throughout adolescence and adulthood.Objective: to determine the prevalence of MetS and cut-off values of waist circumference (WC) and body mass index (BMI) for predicting MetS in children with overweight and obesity. Methods: we conducted cross-sectional analysis of 510 children with overweight and obesity aged 10 to 15 years in Bien Hoa city, Dong Nai province (2012-2014). MetS diagnosis was defined according to the 2007 International Diabetes Federation definition. Results: a relationship existed between BMI and dyslipidaemia (p<0.05). Among all participants, 31.37% met the criteria for MetS (female>male, p>0.05). The most common manifestation of MetS in this study was WC-blood pressure-triglyceride (41.15%). The cut-off anthropometry values for predicting MetS were as follows: BMI of 25.00 in boys and 24.50 in girls, and WC of 82 cm in boys and 80 cm in girls. Conclusions: the prevalence of MetS was 31.37% among children with overweight and obesity. The cut-off values of WC and BMI in this study could be the optimal threshold for predicting MetS in such children aged 10 to 15 years.

71-78

Authors: Nguyen Van Thang, Vu Van Thang, Tran Dinh Trong*, Jerome Faucet

This paper explores the maximum amount of rainfall in the Central coastal provinces of Vietnam (Quang Binh case study) for return periods of 5 years, 10 years, 20 years, 50 years, and 100 years, which correspond to frequencies of 20%, 10%, 5%, 2%, and 1%, respectively. The results show that at a frequency of 20%, the maximum intensity of rain during a heavy rain spell can range from 636.6 to 696.0 mm, while the maximum one-day amount received was over 300 mm, which can occur many times in 5 years. At a frequency of 1%, the intensity of rain during a heavy rain spell can range from 1,197.9 to 1,268.3 mm, while the maximum one-day amount ranged from 487.4 to 521.9 mm. However, such values are very rare over the course of 100 years. In addition, in terms of annual rainfall, the spatial distribution of heavy rainfall in coastal areas was significantly smaller than that in mountainous areas. The highest one-day and five-day rainfall have the same pattern of spatial distribution as annual rainfall.

84-89

Authors: Dao Minh Trang, Huynh Thi Lan Huong*, Mai Van Trinh

This study aims to develop a method for calculating the carbon footprint of rice during its life cycle by combining Life Cycle Assessment (LCA) and the 2006 Guideline of the Intergovernmental Panel on Climate Change (IPCC) for National Greenhouse Gas Inventories (GL 2006) for paddy rice grown in Phu Luong commune, Dong Hung district, Thai Binh province, Vietnam. In the course of the study, a LCA survey that included activities in the upstream processes, the agricultural process, and the post-farm stage was conducted based on interviews with three groups of 30 farmer households that apply the conventional practice of rice production, the system of rice intensification (SRI), or the wide-narrow row method. These cultivation practices are applied for both the winter-spring crop and summer-autumn crop seasons. The emissions were calculated by multiplying the activity data by the default emission factors in GL 2006 or in other relevant studies. The emission factors of methane (CH4) from rice cultivation and nitrous oxide (N2O) from agricultural soil were adjusted using actual measurement results from the Institute of Agricultural Environment (IAE) in 2016. The results of the calculations show that the main sources of the emissions that constitute the carbon footprint of rice include: (i) CH4 emissions from rice cultivation; (ii) electricity generation for irrigation; (iii) diesel combustion for the operation of agricultural machinery, and (iv) fertiliser production. Emissions from other activities were negligible. The carbon footprint of spring rice is 2.69kgCO2e/kg of rice grown using the conventional paddy cultivation method, 2.35 kgCO2e/kg for rice grown using the SRI method, and 2.29 kgCO2e/kg for rice grown using the wide-narrow row method. In summer, the carbon footprint for rice grown using the conventional method is 3.72kgCO2e/kg of rice, 3.56 kgCO2e/kg of rice using SRI, and 3.3kgCO2e/kg of rice using the wide-narrow row method. Three mitigation options are proposed: integrated crop management for rice; alternate wetting and drying; and the substitution of urea fertiliser (CO(NH2)2) with ammonium sulphate ((NH4)2SO4).

3-8

Authors: Trung Kien Vu*, Hung Lan Le

In complex indoor environments, due to the attenuation of the signal and the changing surrounding environment, the censoring and multi-component problems may be present in the observed data. Censoring refers to the fact that sensors on portable devices cannot measure Received Signal Strength Index (RSSI) values below a specific threshold, such as -100 dBm. The multi-component problem occurs when the measured data varies due to obstacles and user directions, whether the door is closed or open, etc. By accounting for these problems, this paper proposes to model the RSSI probability density distributions using the Censoring Gaussian Mixture Model (C-GMM) and develop the Expectation-Maximization (EM) algorithm to estimate the parameters of this model in the offline phase of the Wi-Fi fingerprinting based Indoor Positioning Systems (IPS). The simulation results demonstrate the effectiveness of the proposed method.

14-22

Authors: Le Anh Tuan*, Guido Wyseure

Miscible displacement can be understood as a physical process in a porous medium whereby two or more fluids fully dissolve into each other when a fluid mixes and goes into the pore space occupied by other fluids without the existence of an interface. A physical model was made in Can Tho University, which included an electrical current system connecting nine groups of four-electrode probes for measuring the electrical conductivity of a potassium chloride solution flowing through a horizontal sand column placed in a firm frame. The experiments were performed with different volumetric flow rates and three types of sand (fine, medium and coarse). The breakthrough curves were analysed, and then the hydrodynamic dispersion coefficients were calculated. The hydrodynamic dispersion coefficient was one of the hydraulic and solute transport parameters used to design a constructed subsurface flow wetland. The research proves that the flows were laminar, and that mechanical dispersions dominated over molecular diffusions and that the dispersions were large enough to cause combined mixing and flowing processes.

30-35

Authors: Ngo Quang Huy, Mai Van Quan, Le Quang Man, Duong Thi Nguyen, Trinh Xuan Hoat*

Cassava (Manihot esculenta Crantz) is one of the most important crops in Vietnam for providing food, starch sources, and raw materials for the production of bio-ethanol and other purposes. Cassava bacterial blight (CBB)disease, caused by Xanthonomas axonopodis pv. manihotis (Xam), is one of the most important factors affecting cassava production in Vietnam. A rapid and sensitive molecular tool is required to support the traditional method, primarily based on biochemical reactions, that was considered less sensitive and time-consuming. In the present study, in order to detect Xam, the Polymerase Chain Reaction (PCR) technique was applied with the two primerpairs, rpoD_17F/rpoD_1005R and XgyrconpcrF1/Xgyrconrpcr1, to amplify partial sequences of rpoD and gyrBgenes, respectively. The primers directed the amplification of about 900 bp DNA fragments from CBB-infected leaf and stem tissues. All the amplified DNA sequences were identical in each gene and to the Xam reference strains (accession numbers KP265376 and KP265378 for the rpoD gene, and KP265387 and KP265388 for the gyrB gene) from GenBank. The representative sequences of rpoD and gyrB genes were deposited in GenBank with accession numbers MF774491 and MF774490, respectively. DNA and phylogenetic analysis based on the sequences of rpoD and gyrB genes have confirmed that Xam is the causal agent of CBB in Dong Nai, Vietnam. This is the first confirmed identification of the causal pathogen of CBBdisease in Vietnam using molecular tools, and this method is a reliable tool for the detection and identification of other plant bacterial pathogens.

41-44

Authors: Tam Vo, Ngoc Tuan Anh Dang*, Nhu Hiep Pham, Gia Khanh Pham

This study aims to assess the results of kidney retransplantations and the survival of second kidney allografts performed in our center. Methodology: of 550 kidney transplantations performed since July 2001, 26 were second kidney transplants. Many recipients were sensitized. All patients were treated with the same immunosuppressive regimen. Results: grafts were functionally effective in all patients with kidney retransplantations one month after the transplant. Graft survival was 100% after one year (17/17) and after five years (1/1). Graft survival was similar for second and primary kidney transplants performed during the same period of time. There were three cases of acute rejection, but all of these cases responded to the anti-rejection treatment. Conclusions: the rate of acute rejection was similar for both second and primary transplantations in our hospital, and the second graft outcome demonstrated effectiveness 12 months after transplantation

52-57

Authors: Thi Tham Nguyen, Thi Huong Nguyen, Thi Ngoc Que Nguyen, Thi My Tran, Thi Thu Huong Pham, Dinh Thang Nguyen, Thi Van Anh Nguyen*

This field study was performed to demonstrate that Bacillus aquimaris SH6 spores administered as a feed supplement in adequate amounts confer beneficial effects to the whiteleg shrimp. Shrimps were administered either B. aquimaris SH6 spores at 1×106CFU g-1 pellet (SH6 group) or a mixture of SH6 and B. subtilis SH23 spores at 5×105 CFU g-1 pellet for each strain (SH6-SH23 group). After a 28-day feeding period, the number of SH6 spores in the gut of whiteleg shrimp in the SH6 group and the SH6-SH23 group were 5.7×103 CFU gut-1 and 7.7×103 CFU gut-1, respectively. The total bacterial population of these two experimental groups increased about 10-75% compared to that of the control group. The astaxanthin level and red colour score were the highest in the SH6-SH23 group (1.66 μg.g-1 shrimp; 28-29), followed by the SH6 spore group (1.42 μg.g-1 shrimp; 27-28), and were the lowest in the control group (0.61 μg.g-1 shrimp; 26-27). Nevertheless, the growth rate of shrimps was similar (7.8-8%) among the three groups. In conclusion, feed supplements containing SH6 and SH23 spores co-effectively improved live counts and diversity of microbiota in shrimp guts, as well as improved astaxanthin level and red colour of whiteleg shrimps

62-67

Authors: Bich Thuy Thi Nguyen, Nghien Xuan Ngo, Ve Van Le*, Luyen Thi Nguyen, Ry Kana, Huy Duc Nguyen

The objective in this study is to investigate optimal culture conditions for mycelial growth and fruiting body formation of the Ling Zhi mushroom, Ganoderma lucidum strain GA3. The results of the study show that the optimal media and temperature for the mycelial growth are potato, glucose, and agar (PGA) supplemented with rice bran, and 25-300C, respectively. Strain GA3 is able to grow in a wide pH range, between 4 and 12.The most favourable substrate mixture for the formation and development of the fruiting body is 87% sawdust + 4% corn powder + 8% rice bran + 1% calcium carbonate (CaCO3)

74-81

Authors: Hung Pham*, Van Trung Le, Le Phu Vo

In recent years, activities related to socio-economic development have led to land cover (LC) changes in the upper part of the Dong Nai river basin. The use of remote sensing applications to analyse the impacts of these changes plays an important role in the managing the sustainability of theriver basin. This paper introduces a solution for analysing the impacts of LC changes on the water balancein the upstream catchment of the Dong Nai river in Lam Dong province. Landsat images were used for mapping and monitoring major changes over the last 20 years. Rainfall and water discharge data was collected from the local hydrometeorological stations to identify the impacts of the LC changes on the runoff in the catchment area. The results show that the forest area was reduced by more than 223,576 ha (23%). The main changes were an increase in the agricultural area from 18.2 to 31.3% and in water bodies from 0.9 to 2.2%. The latter was due to hydropower development projects in the catchment area. The LC changes caused by the changes in the hydrological conditions of the river basin have had a significant impact on water resources. The identification of the main LC changes in the catchment area could be useful for establishing a policy to protect the headwater forests and mitigate against future impacts.

92-96

Authors: Tran Dinh Hoa*, Do Hoai Nam

Increasing flood risks in a changing climate tend to put greater pressure on water-related infrastructure, existing operations, and management practices. This paper introduces preliminary research results on river information management and flood-risk reduction based on an early flood-release approach that has the goals of better reservoir operation, adapting to climate change, and ensuring dam safety in Vietnam. Early flood release is performed using inflow prediction information derived from a medium-range global numerical weather-prediction model. The results show that peak discharge and inundation areas are remarkably reduced, and are useful for improving the safety of dams and flood-risk management in downstream areas.

3-7

Authors: Thi To Yen Nguyen, Phung Anh Nguyen,Thi Thuy Van Nguyen,Tri Nguyen, Ky Phuong Ha Huynh*

In this work, the efficiency of a material prepared from red mud and rice husk ash (ZRM), in Cr(VI) absorption, without the use of acid to neutralize raw red mud (RM), was examined. The physico-chemical characteristics of the obtained material weredetermined by several methods, including BET nitrogen adsorption, XRD, SEM, and TEM. ZRM was employed in the adsorption of Cr(VI) in solution at 25oC with a Cr(VI) concentration of 20 ppm.The results showed that the nano particles of material were formed within the size range of 30-50 nm, and that the specific surface area of the material was 70.76 m2/g. The conditions of the adsorption process (i.e., the initial pH of the solution, the stirring rate, and the material content) were seen to significantly affect the efficiency of Cr(VI) adsorption at the material’s surface. The optimum conditions for Cr(VI) adsorption via ZRM were determined as pH=2, a stirring rate of 300 rpm, and a material content of 10 g/l. With these conditions, the maximum adsorption capacity for Cr(VI) in a solution of ZRM was found to be 23.32 mg/g.

15-18

Authors: Thien-Trong-Nguyen Le, Thanh-Dat Dinh, Dinh-Dai Nguyen, Thi-My-Chi Vo, Thanh-Son Dao*

Metal contamination and pollution are of human and environmental concern Phytoremediation is one of the suitable high-efficiency means to treat metal pollution. This study aims to observe the responses of Pisum sativum L. in its early life stage to three metals, arsenic (As), copper (Cu) and lead (Pb) in laboratory conditions. Seeds of P. sativum were treated with water containing 0, 50, and 500 μg/l of these metals over a period of 7 days. The results show that the germination of seeds is similar for the control and metal treatments, ranging from 90-100% after 4 days of watering. Shoot development of the seeds exposed to the metals and the control were not significantly different, except that the samples which had undergone the treatment with 500 μg Pb/l had longer shoots. Our results evidence a high capacity for metal tolerance in this plant in the early stages of its life. Therefore, P. sativum may be a promising candidate for the phytoremediation of metal contamination and pollution.

25-30

Authors: Nho Thuan Nguyen*, Vu Nguyen Doan, Ha Le Bao Tran

In recent years, three-dimensional (3D) in vitro tumor models have become more common in cancer research across the world. Selecting scaffolds, seeding cells into the scaffolds, and culturing them are pivotal for the morphologies and proliferation of cancer cell lines. Therefore, this experience has developed a 3D tumor model based on co-culturing MCF-7 cells and fibroblasts (3:1) into gelatin-alginate scaffolds (3x3x5 mm3). Quantity, proliferation, and morphologies of tumors were evaluated through cell yield on a scaffold, enzymatic assay, cell number, hematoxylin and eosin stains (H&E), and scanning electron microscope (SEM). The results indicate that the complex of MCF-7 cell lines and fibroblasts in scaffolds proliferated and increased in terms of cell mass number and cell mass size. Their morphologies align with those of the in vivo figures demonstrated previously. This research facilitates new opportunities for the study of cancer biology and drug screening in Vietnam.

39-44

Authors: Van Tho Le*, Van Tu Nguyen, Ngoc Diem My Tran, Damin Lee, Won Kim, Van Son Dang, Doan Dang Phan, Duc Thien Luong

Brachyuran crabs are the most diverse group of crustaceans. They are found in most marine habitats such as coral reefs, sandy beaches, rocky beaches, mangroves, and seagrass meadows. In this study, we investigated the species composition of brachyuran crabs at 10 sampling locations belonging to three habitats (mangrove forest, artificial dykes, sandy beaches) at Duyen Hai town on August (rainy season) and December (dry season) in 2017. We found that there were 22 species belonging to 10 genera of six families present in the research area. The Ocypodidae family is the most abundant, with 45.5% of the species, following by the Grapsidae (22.7%), Sesarmidae (13.6%), Portunidae (9.1%), Matutidae (4.5%), and Xanthidae (4.5%). The densities of brachyuran crabs ranged from 2.0±1.1 (inds/m2) to 17.2±4.3 (inds/m2). The mangrove forest habitat showed a greater diversity of species than the sandy beach and artificial dyke habitat. The rainy season supported greater diversity than the dry season.

52-58

Authors: Thi Kieu Oanh Pham, Van Cuong Pham, Thi Thuy Lai, Duc Long Tran, Thanh Thuy To*

The teleost fish medaka (Oryzias latipes) is currently used by laboratories worldwide as a model for many human diseases, including bone diseases. Our research group focuses on a medaka model for osteoporosis. To characterize the bone indexes of diseased animals, the bone development indexes of healthy wild-type fish are required for comparative analysis. Thus, this study examined the developmental and bone development indexes of wild-type medaka larvae at 11 and 16 days of age, the two developmental stages selected for the analysis of diseased patterns in osteoporosis-induced animals. The assessed parameters included the total body length of live larvae, number of caudal fin rays, vertebrae, and neural and hemal arches, as well as the total areas of mineralized vertebrae and lengths of mineralized arches. The obtained data are important for subsequent studies on bones using this fish model

66-70

Authors: Nguyen Van Thuan, Ngo Thi Thanh Thuy, Nguyen Hong Hai, Nguyen Cong Nguyen, Xuan-Thanh Bui*

Human urine is known as the excreta with a high concentration of nitrogen and phosphorus, causing eutrophicationin water bodies. In this study, human urine was used to feed microalgae (Chlorella vulgaris) in a membrane photobioreactor (MPBR) at various microalgae retention times (MRTs) and hydraulic retention time (HRT) of 2 days to evaluate its biomass production. The results indicate that MPBR was operated under MRT of 2 to 5 days and HRT of 2 days, which performed the optimum condition with biomass productivity from 146.43±8.52 to 151.93±15.05 mg.l-1.day. Moreover, the MPBR using the urine as a nutrient source demonstrated the high performance in biomass production and strong growth of microalgae.

78-81

Authors: Danh Quan Le, Thi Thuy Pham*, Hoang Giang Pham, Manh Khai Nguyen

This paper evaluates the adsorption capacity of iron-rich adsorbent to remove arsenic from groundwater in decentralised water supply treatment; a pilot-scale with a capacity of 5 m3/day has been investigated at Cu Da Nursery School in Hanoi city, in which the concentration of arsenic in groundwater is abnormally high (175-400 μg/l). The pilot system was designed to include a series of processes, such as aeration, sedimentation, sand filtration, and adsorption, using the iron-rich adsorbent and activated carbon from coconut shells. The pilot system was tested with three operated modes. The results demonstrate that the treatment efficiency of the overall treatment processes was significantly higher than that of the traditional treatment system used by local people. After aeration, sedimentation, and sand filtration, the water quality was discovered to respond substantially in reducing iron by over 96% (from 8-12 mg/l to less than 0.3 mg/l) arsenic by 55 to 60%, but after iron-rich adsorbent, the concentration of arsenic decreased to less than 10 μg/l, which fulfills Vietnam National technical regulations concerning drinking water quality

89-94

Authors: Xuan Hien Nguyen*, Xuan Trinh Nguyen, Hong Hanh Nguyen, Thanh Thuy Tran, Duc Quyen Le

This research utilizes the disaster risk concept developed by the Intergovernmental Panel on Climate Change (IPCC) to determine and assess the storm surge risk in aquaculture in the coastal area from Quang Ninh to Ninh Binh province. The results indicated that the highest level of risk occurred in Thai Thuy district (Thai Binh province) and Quang Yen town (Quang Ninh province). The second highest level or risks occurred in Tien Hai district (Thai Binh province), Mong Cai city and Hai Ha district (Quang Ninh province). The lowest level of risk transpires in Uong Bi city (Quang Ninh province) and Kien An district (Hai Phong city). The results provide a scientific basis to support local government in establishing proactive response plans to storm surges, reduce and prevent storm surge damage to aquaculture, assist policy making and establish suitable development priorities for the coastal areas in the Northern region

3-8

Authors: Thi Thu Huong Tran, Thi Tuyet Mai Phan*, Van Boi Luu, Ngoc Lan Pham

This research illustrates the results of a study on the synthesis of maleic anhydride-vinyl acetate copolymers (MAVA) with the monomer molar ratio of 1:1 by the radical polymerisation method in which benzoyl per-oxide was used as a catalyst. The structure and compo-sition of MAVA were characterised by FTIR, 1H-NMR and 13C-NMR spectra. The molecular weight of the co-polymers was determined by the viscosity method. The copolymers were then modified by the esterification reaction with hexadecanol - a long alkyl chain alcohol. The modified copolymer products (MAVAC) were used as additives to improve the cold flow properties of palm oil-based biodiesel through pour point temperature measurement according to standard ASTM-D97 and dynamic viscosity according to ASTM D445-97. The re-sults showed that the MAVAC additives with the comb-shape structure at the concentration of 1000 ppm could decrease the pour point temperature of palm oil-based biodiesel by 5.5oC and dynamic viscosity by 0.17 cPs.

13-18

Authors: Trinh Nguyet Tran, Huynh Xuan Phong, Bui Thi Thao Anh, Bui Hoang Dang Long, Nguyen Ngoc Thanh, and Ngo Thi Phuong Dung*

Acerola (Malpighia emarginata) vinegar is one kind of fruit vinegar produced using acetic acid fermented by acetic acid bacteria. In this study, Acetobacter senegalensis A28 was applied in acerola vinegar production at a high temperature. With 1.0% (v/v) of A. senegalensis A28 inoculum, the suitable conditions for production of acerola vinegar were determined to be pH 6.5, 20°Brix, 106 cells/ml, as well as 4.0% (v/v) of ethanol added to acerola juice. Moreover, a temperature of 35°C was found to be suitable for fermentation in both 100 ml and 2 litre working volumes. Total acid concentrations of 5.45% (w/v) and 4.90% (w/v), respectively, were achieved after 4 days of fermentation. Acid concentrations of 5.40% (w/v) and 4.70% (w/v) were obtained at 37°C after 5 days of fermentation in volumes of 100 ml and 2 litres, respectively. At pilot-scale fermentation of 20 litres at 37°C, acid concentration of 3.68% (w/v) was achieved after 5 days of fermentation.

26-32

Authors: Van Dang Tran*, Dong Tran, Marc Oudjene

Timber is highly anisotropic. It behaves differently in diverse directions. Tension and compression perpendicular to the grain present a low strength with respect to the ones parallel to the grain. To compensate for the lack, the self-tapping screw is an excellent choice for reinforcing the timber. This paper focuses on the notched timber beam with the experimental and numerical results. In the first part, the experimental results of the unreinforced notched beams and the screw reinforced notched beams under bending load will be presented. The second part describes a numerical study in which a 3D finite element (FE) model and a fast FE model of the notched beam reinforced by a self-tapping screw are realised. In particular, the fast FE model is simplified with the use of the screw’s model as a beam element having one translational degree of freedom. This model not only presents a good result in comparison with the experiment as well as the 3D FE model but also requires six times less computational times as compared to the 3D FE model.

37-41

Authors: Quoc Sinh Nguyen*, Chi Bao Nguyen, Thanh Long Le, Sy Vuong Ho, Thi Diem Huong Nguyen, Van Quoc Bao Vo, Van Toan Nguyen

Gamma(γ)-Aminobutyric acid (GABA), which provides a variety of health benefits, is an important bioactive component of tea (Camellia sinensis). A special tea product, GABA tea, contains high levels of γ-Aminobutyric acid which is produced by anaerobic fermentation. Tea fermentation is affected by a number of factors, including anaerobic conditions (vacuum, and the kind of gas used), temperature, and the duration of anaerobic fermentation. In this study, the levels of bioactive compounds in tea leaves produced by fermenting fresh tea leaves in nitrogen gas are investigated. The fermentation was conducted at different temperatures: room temperature (28±2), 35, and 40ºC; and for each temperature setting, the fermentation times were 6, 9, 12, and 15 hours. The results show that the GABA content increased significantly with fermentation temperature. The most appropriate temperature and time for the anaerobic fermentation to produce GABA and other bioactive compounds were, respectively, 40ºC and 9 hours. Under these conditions, GABA content reached the maximum value (202.77 mg/100 g of dry tea); that of total polyphenols was 22.30% of dry matter (DM); caffeine was 2.39% DM; and soluble solids were 36.25% DM.

48-54

Authors: Tran Thi Thuy Ha, Thai Thi Lam, Nguyen Thanh Huyen, Nguyen Xuan Canh*

To isolate and characterise free nitrogen-fixing bacteria, we collected randomly soil samples from different areas of Ha Noi. Nitrogen-fixing bacteria were isolated using Burk’s medium without nitrogen mineral supplement. The ammonia (NH4+) synthesis of these bacterial strains after biomass production was determined by means of Nessler reagent. Based on the results of isolation, we observed and evaluated colony and cellular morphology, pigment production, and metabolic activities of twenty-five isolates. Among the isolated bacteria, two bacterial strains (6.2 and 8.2) with high NH4+ concentration in the cultural medium were selected as the best strains for nitrogen-fixing ability. The optimal pH and temperature for their growth and nitrogen fixation are 7.0 and 30°C, respectively. Growth is best favored in the presence of sucrose. We sequenced the 16S rRNA gene of selected strains and compared the homology of them in GenBank using BLAST search. The result of the comparison shows that the 6.2 and 8.2 strains have 99% and 100% 16S rRNA-sequence similarity with Pseudomonas sp. and Bacillus sp., respectively

59-66

Authors: Hanh Dung Thai, Van-Tuan Tran*

The filamentous fungus Aspergillus oryzae, also named as the koji mold, is a preferred host for enzyme production due to its prominent secretion ability into the culture medium. Fungal laccases are widely used in different industrial processes, especially in removing environmental pollutants. Up till now, little was known about the roles of some laccase genes from the black mold Aspergillus niger. The McoD laccase gene from A. niger includes three exons interrupted by two short introns. The respective coding sequence of the gene is computationally predicted to encode a secreted laccase of 563 amino acids. In this study, a binary vector carrying the A. nigerMcoD gene was successfully constructed for heterologous expression in the edible fungus A. oryzae. This vector was transformed into A. oryzae using the Agrobacterium tumefaciens-mediated transformation method. The transformation efficiency was relatively high in two different auxotrophic A. oryzae strains, including RIB40∆pyrG and VS1∆pyrG. All the tested transformants possess in their genomes the construct for expression of the McoD laccase gene under control of the strong A. oryzae amyB promoter. The selected transformants were examined for the laccase activity using the ABTS substrate. The results showed that in comparison to the wild-type fungal strains, the transgenic strains could oxidise ABTS to form the sea green colour, which can be seen directly on the agar plate

74-80

Authors: Le Anh Tuan*

The Vietnamese Mekong river delta (MD) is recognised as the biggest agriculture and aquaculture region of Vietnam. The MD plays an important role in ensuring food security for the country. The MD also has many sensitive ecosystems reliant on the ecology of the Mekong river basin. However, during the last decade, many electricity generation plants, both renewable and non-renewable power projects, have been built and some will be built in the near future in the MD. These energy plants’ construction and operation may prove to be a challenge to the national energy strategy.This paper is a monograph review of two sides of energy sector industrialisation in the MD with a focus on ‘green’ and ‘grey’ socio-economic development (as ‘xanh’ and ‘xám’ in Vietnamese respectively). ‘Green’ energy is understood as the electricity generated from inexhaustible sources and known as renewable energy. It emits fewer greenhouse gases and causes less harm to habitats in comparison to traditional fossil fuels and hydropower. ‘Grey’ energy is another word for non-renewable energy or polluting energy, which can have negative effects on human health, environment, and climate. This paper finds that the MD’s energy development plans at present might not be as ‘green’ as expected, due to more ‘grey’ power plans in the planning pipeline. This paper also considers an outlook on energy prices and impacts on long-term sustainable development of the MD.

89-96

Authors: Mau Nguyen-Dang*, Truong Nguyen-Minh, Hidetaka SASAKI, Izuru TAKAYABU

This article presents analyses of changes in the seasonal characteristics of the far future climate (2080-2099) across Vietnam as projected by the Non-Hydrostatic Regional Climate Model (NHRCM) in terms of the RCP 8.5 (Representative Concentration Pathways 8.5) scenario. The results show significant changes in seasonal rainfall in Vietnam compared with the 1982-2003 baseline period. Specifically, the June-August rainfall is projected to increase in South Central (SCVN), Central Highlands (CHVN), and South Vietnam (SVN), but to decrease by approximately 50% in North Central (NCVN) and off the Central coast. In the September-November season, the NHRCM detects an increase in rainfall of about 50% in North Vietnam (NVN) and CHVN. The increase and decrease in rainfall are due to the convergence and divergence of moisture flux that might be associated with the westward expansion of the Northwestern Pacific High Pressure in the far future

3-6

Authors: Thi Thuy Duy Nguyen, Hoang Phuong Tran*

The rapid and green procedure for the Knoevenagel reaction between aromatic aldehydes and diethyl malonate was developed by using 1-butyl-3-methylimidazolium hydroxide, [Bmim]OH, as an efficient catalyst. The condensations showed good yields with a wide range of aromatic aldehydes in solvent-free condition and short reaction times. [Bmim]OH was easy to recover and could be reused several times without significant loss of catalytic activity.

16-23

Authors: Van Quang Le*, Quang Minh Do, Minh Duc Hoang, Hoc Thang Nguyen

In this study, the alkaline solutions (NaOH) with concentrations from 1M to 18M, red mud (RM) and silica fume (SF) were used as reactors in geopolymer reactions. RM contains 7.40% SiO2 and 13.65% Al2o3and SF has 94.50% SiO2, but only the active oxides can participate in the geopolymer reactions. The activity of the oxides was investigated by determining the compressive strength of the samples under different curing conditions. The characteristics of the geopolymer samples were determined by using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermo-gravimetric analysis (TGA)/differential thermal analysis (DTA) and nuclear magnetic resonance analysis (NMR). The experimental results indicate that active silica mainly exists in SF. In the structure of geopolymers, the silicon can bond directly with each other (Si-Si) or be linked through ‘bridging’ oxygen (Si-O-Si) to form independent polymer chains, while aluminium atoms can only replace the silicon atoms in Si-O-Si polymer chains to form Si-O-Al instead

30-43

Authors: Hieu T. Nguyen*, Huong T.T. Le, Liem T. Nguyen, Hua Lou, Thomas La Framboise

Next-generation sequencing (NGS) is a high throughput sequencing technology, which has revolutionized both basic and clinical research of the human genetic disorders. This technology is also called massively parallel sequencing (MPS) due to its ability to generate a huge amount of output data in a cost- and time-effective manner. NGS is widely utilized for different sequencing applications such as targeted sequencing (a group of candidate genes), exome sequencing (all coding regions), and whole genome sequencing (the entire human genome). With NGS, a variety of genomic aberrations can be screened simultaneously such as common and rare variants, structural variations (amplifications and deletion), copy-number variation, and fusion transcripts. NGS technologies combined with advanced bioinformatic analysis have tremendously expanded our knowledge. On the one hand, the basic research area involves direct use of NGS to identify novel variations and determine human disease mechanisms. On the other hand, clinical research is being advanced by high-throughput genetic tests with high resolution and clinically relevant genetic information for molecular diagnoses of human disorders. In this communication, we introduce NGS technologies and review a few key areas where NGS has made a significant impact, with an emphasis on the application of NGS to the identification of the molecular bases of human genetic diseases.

51-55

Authors: Ngo Tat Trung*, Dao Thanh Quyen, Phan Quoc Hoan, Thirumalaisamy P.P. Velavan, Le Huu Song*

Background/aims: It has been shown that quinolone resistance arises due to mutations in the quinolone resistance-determining regions of the drug targets. This study aimed to optimise a multiplex PCR assay to track plasmid-mediated low-level quinolone resistance profiles.Subjects and methods: A multiplex PCR-based-method in which the primers were already established by our team. About 44 samples were collected from 44 patients who enrolled in this study by using surgical site infection (SSI).Results: By targeting the conserved domains of qnrA, qnrB, qnrS and the qnrVC gene families, the primer number was reduced significantly to only four pairs in one multiplex PCR. Using multiplex PCR, 3/44 SSI samples were found to be carrying fluoroquinolone-resistance genes (qnrA, qnrB, qnrS, qnrVC).Conclusion: A multiplex PCR for detecting pathogens as well as identifying quinolone resistance genes all in one reaction was successfully established

57-67

Authors: Van Canh Doan, Duc Nhan Dang*, Kien Chinh Nguyen

The origin and chemistry of the groundwater in the middle Pleistocene (qp23), lower Pleistocene (qp1), upper Pliocene (n22), lower Pliocene (n21), and the Miocene (n13) in the Mekong river delta (MKRD) were investigated by using isotopic and geochemical techniques. The origin of the groundwater was evaluated based on the composition of the water stable isotopes (d2H and d18O) in the local precipitation, in water from the rivers system, and in the groundwater samples. The hydraulic interaction between the surface water and the groundwater as well as between the aquifers was assessed by a statistical treatment for the mean and standard deviation of the d18O signature and based on the 14C-ages of the water samples taken from different aquifers. The salinization of groundwater in the deep aquifers was investigated using the d18O signature combined with the geochemical composition of the water samples. It was revealed that the groundwater in the deep aquifers in the MKRD could be divided into two groups. The first group is fresh and represents the regional precipitation with the long traveling time ranging from older than 100 years to older than 40 ka BP (kilo years Before Present). The second group is the regional precipitation that is recharged from the remote areas mixed with the seawater. Statistical treatment with the mean d18O using the Mann-Whitney test showed that the water from the Mekong river system did not or very weakly recharged the deep aquifers. The groundwater in the deep aquifers in that region was likely to be connate, so that fresh groundwater resource in the region seemed to be limited. The chemistry of the groundwater in the study region is controlled by the incongruent dissolution of the Mg-calcite as well as sulfate and iron oxy-hydroxide reductions by organic matters presented in the aquifer sediment. The groundwater in the deep aquifers in the MKRD from some locations was saline, but the salinity in most aquifers was thought to result from the migration of saline water entrapped in the marine sediment pores to the fresh water in the aquifers. Meanwhile, in other locations, the salinity was suggested to result from the salt intrusion due to the over-abstraction rate, as it was evident from the d18O vs. [Cl-] relationship, or due to the up conning of saline water from the deeper aquifers to the upper ones. Particular measures must be developed for the better management of groundwater in the MKRD to ensure a sustainable resource of freshwater being supplied to the local population in future

73-77

Authors: Lam Nguyen, Xuan Thi Trinh, Hien Trinh, Dang Hung Tran, Cuong Nguyen*

The development of next-generation sequencing tech-nologies has helped sequence large genomes easily, producing a huge number of short-reads - small frag-ments of DNA. Despite the existence of many developed alignment tools, mapping short-read datasets to the reference genome, a crucial step of genome analysis, still remains a challenge. In this study, we develop a short-read alignment program, BWTaligner, based on the Burrows-Wheeler transform compression - exact and inexact matching. We tested it on the paired-end read data simulated from chromosome 9 of the rice genome to compare the alignment and single-nucleo-tide polymorphism (SNP) calling between our aligner and BWA - the preferred alignment program. The re-sults showed that the BWA delivers higher recall and F-score, while BWTaligner has better precision in high coveragedepth

84-91

Authors: Van Doanh Vu*, Ha Phong Doan, Thi Thu Trang Bui

Nam Dinh province is located in the Red river delta with a relatively flat terrain. The North East of Nam Dinh is bordered by the Red river and the southwest by the Day river and has a coastline of approximately 80 km. Given the geographical location, Nam Dinh has favourable conditions for agricultural and aquaculture production. Climate change creates a large number of potential risks for Nam Dinh. This includes sea level rise, typhoons, flood tide, etc. According to the climate change and sea level rise scenario in 2016, if the sea level rises by 100 cm, the flood risk area in coastal districts such as Hai Hau would be 67.34%, Giao Thuy 64.6%, Nghia Hung 81.61% and Xuan Truong 59.3% [1]. According to the monitoring data from Vietnam Institute of Meteorology, Hydrology and Climate Change (IMHEN), the salinity intrusion area due to sea level rise is likely to widen, which degrades and affects the area of the mangrove ecosystem [2]. In addition, the sea level rise may reduce the resilience of irrigation system due to the changes in estuarine and coastal dynamics such as water levels, flows, waves, etc. Through synthesising the local and international guidelines and in combination with expert consultation and field surveys, this paper develops an assessment procedure for sea level rise that causes economic damage to agricultural land use in order to quantify the impact of sea level rise in 4 coastal districts of Xuan Truong, Giao Thuy, Hai Hau and Nghia Hung in Nam Dinh province.