Vietnam Journal of Science, Technology and Engineering

3-9

Authors: Hue Thi Dao*, Tung Duc Vu

Building an integrated river delta basin and coastal management plan in the context of climate change requires suspended sediments data, which plays an important role and is the key component for understanding the hydrology regime in the delta region. Sediments are responsible for carrying a considerable amount of nutrients and contaminants. Most sediment discharge data is acquired by surveys/data collection activities or by mathematical modelling. However, these methods are costly, time-consuming, and complex. Therefore, in this study, the authors investigate the potential use of satellite observations (MODIS reflectance) to detect suspended sediment flux in the Red river delta (RRD) of Vietnam. The relationships between discharge (Q), suspended sediment concentration (SSC), and total load (L) collected from the three in-situ stations Son Tay station (ST), Thuong Cat station (TC), and Hanoi station (HN) in the RRD are determined by regression analyses of reflectance data (R) obtained from MODIS bands 1-2 (250-m resolution). The results present a close connection between the monthly average of SSC and R and a good statistical relationship between the monthly average of Q and R in HN. At TC and ST, a lower correlation was found compared to HN because of the cloud cover and the position where data was collection in the river. The coefficient of determination ranged from 0.11 to 0.40 for the R-SSC and R-Q relationships. A method of estimating SSC and L at a single point along the river using data from Q and R was proposed based on the relationship correlation results.

15-18

Authors: Nguyen Thanh Le*, Huu Giap Tran, Thi Kim Oanh Vu, Thuy Duong Pham, Ngoc Thuc Dinh, Anna Stojakowska, Bich Ngan Truong

Maesa membranacea A. DC. (Myrsinaceae) has been traditionally used for the treatment of fever and hepatitis. The phytochemical investigation of Maesa membranacea stems has led to the isolation of six compounds including kaempferol (1), (-)-epicatechin (2), betulinic acid (3), p-hydroxybenzoic acid (4), vanilic acid (5), and protocatechuic acid (6). The chemical structures of these compounds have been determined by nuclear magnetic resonance (NMR), mass spectrometry (MS) data, and by comparison with previously reported works. This is the first report of a chemical study on Maesa membranacea as compounds 1-6 listed above were found from the Maesa genusfor the first time.

26-32

Authors: Thi Tuyet Mai Phan*, Ho Viet Cuong, Pham Ngoc Lan

Carboxymethyl cellulose-graft-poly(acrylic acid-Sodium acrylate-acrylamide) SAPs have been prepared by the free-radical grafting solution polymerization of acrylic acid (AA) and acrylamide monomers (AM) onto carboxymethyl cellulose (CMC) in the presence of N,N′-methylenebisacrylamide as a crosslinker (MBA) and ammonium persulfate (APS) as an initiator. Various factors influencing the water absorbency of the polymer were studied. These include the weight ratio of APS, MBA, and CMC compared to the monomers. The optimal conditions were found as follows: 1% APS, 0.25% MBA, and 10% CMC (weight ratio to monomers). The maximum absorbencies for distilled water and 0.9 wt.% NaCl solution were 406 g/g and 69 g/g, respectively. The structure of the synthesized polymer was confirmed by Fourier Transform Infrared spectroscopy (FTIR). Additionally, the water absorption and water retention behavior of the polymer in soil were investigated. The results showed that this polymer could be employed as a suitable moisture-holding additive in soil for cultivation purposes.

38-44

Authors: Vu Thi Thu Nga*, Gilbert Teyssedre

Cable technologies have evolved in different ways for applications using high voltage alternating current (HVAC) and high voltage direct current (HVDC) over the last 40 years. Since the 1950s, mass-impregnated paper was progressively replaced by extruded insulation made of polyethylene and then cross-linked polyethylene (XLPE). The switch from paper insulation to extruded cables went on continuously while cables were designed with ever increasing voltage requirements. However, regarding space charge build-up and field redistribution, particularly at polarity reversal stages in thyristors, the behaviour of extruded cables under such DC stress is not fully understood. For this reason, material improvement, characterization, and modelling are still intensively researched for cables, accessories, and power conversion equipment. The weaknesses and methods used to simulate the characteristics of insulation are presented and compared in this work through the simulation results of the macroscopic and fluid model.

49-55

Authors: N.N. Quynh*, B.H. Hieu, N.N. Dang, N.H. Quang, To Vinh Cuong

n recent years, the construction of upstream reservoirs and the extraction and structural construction activities on the river banks and beds have caused downstream changes in river morphology and hydrological regime of the Red river system, which has especially accelerated from 2000 to 2018. These dramatic variations have significantly changed the morphological characteristics and relationship between the flow and morphology that are a fundamental parameter to evaluate the stability of the channels. In this study, the morphological characteristics and relationship between flow and morphology over some periods as well as under current conditions were analysed. This work provides basic river training parameters for studying river training planning of the Red river system in general and for the Red and Duong river sections in Hanoi in particular.

62-67

Authors: Ha Duc Chu*, Quynh Thi Ngoc Le, Yen Hai Thi Hoang, Thu Phuong Pham, Hong Viet La, Nguyet Minh Thi Nguyen, Anh Xuan Duong, Thao Duc Le, Linh Hung Le, Hoi Xuan Pham

SWEET (Sugars Will Eventually be Exported Transporter) proteins are well known to play pivotal roles in the growth and development of plants. Here, we report the presence of 43 members of the AhSWEET family in peanut (Arachis hypogaea) and determine their general characteristics including chromosomal localization, gene structure, and numerous physical and chemical features of the proteins. We found that the AhSWEET genes were unevenly distributed among the peanut’s 20 chromosomes. The AhSWEET proteins were hydrophobic with a grand average hydropathicity >0 while a majority of the proteins were basic with isoelectric points >7.0. Additionally, most of the AhSWEET genes contained 6 exons and 5 introns. The expression profiles of the AhSWEET genes were explored based on the previous transcriptome atlas. Interestingly, we found that the AhSWEET genes exhibited differential expression patterns across various organs and tissues during the growth and development of peanut plants. Our study provides a solid foundation of the AhSWEET gene family for further functional characterization of AhSWEET genes in the regulation of peanut growth and development

70-75

Authors: Vu Xuan Tao*, Tran Bao Tram, Nguyen Thi Hien, Thai Hanh Dung, Tran Van Tuan

Vietnam possesses an abundant and highly diverse resource of plants. Therefore, the search and evaluation of bioactive compounds extracted from these plants are a potential research direction to support developing products that improve human health. The purpose of this study is to assess the antifungal activity of some essential oils produced by materials harvested in Vietnam such asKing orange peel (Citrussinensis),lemongrass (Cymbopogonflexuosus), peppermint(Mentha arvensis), and betel leaf (Piperbetle). The antifungal effect of these essential oils was determined by the Kirby-Bauer disc diffusion technique. In addition, the antifungal properties of the essential oils were also assessed through their effects on the reproduction ofC. albicansand the spore germination, mycelium elongation, and sporulation ofA. fumigatus. The results demonstrated that all peppermint, lemongrass, and betel leaf essential oils showed antifungal activity againstC. albicansandA. fumigatus. Especially, betel leaf essential oil could perform antifungal activity at a low dilution concentration of 10% and could also inhibit the reproduction of C. albicansand the spore germination, mycelium elongation, and sporulation of A. fumigatus. Meanwhile, orange peel essential oil did not exhibit any antifungal properties.

83-89

Authors: Thuong Quoc Thinh, Truong Tran Nguyen Sang, Tran Quoc Viet, Le Thi Minh Tam, Nguyen Phuoc Dan, Emilie Strady,Kieu Le Thuy Chung*

Microplastic pollution has become a global issue in recent years. Since the early 2000s, scientists have investigated the occurrence of microplastics (MiPs) in the environment. While research on marine MiPs is more advanced at present, there are immense gaps of knowledge regarding continental MiPs. Airborne MiPs are one source of MiPs in the aquatic environment. In the scientific literature, there have been only three publications on presence of MiPs in atmospheric fallout. In developing countries, where plastic waste management is weak, studies on the presence of MiPs in this area are limited. This current study presents a preliminary assessment of the presence of MiPs in atmospheric fallout sampled from the Phuoc Hiep landfill, Ho Chi Minh city (HCMC). The results of this work show that MiP concentrations vary between 1,801 items m-2d-1 and 913 items m-2d-1 in the dry and rainy seasons, respectively.

3-6

Authors: Xuan Quan Cao*, Ngoc Dung Hoang, Hoang Luong Nguyen

The development of a luminance responsivity standard is central to the study of photometry and radiometry at the Vietnam Metrology Institute (VMI). Today, two methods are used to determine luminance responsivity. The first method uses an integrating sphere light source, also known as a luminous intensity standard lamp, and the second method compares the luminance responsivity value to that of a known standard photometer. Using these methods, it is possible to identify small uncertainties. In this work, we analysed the luminance responsivity standard system (model: VMI-PR-006) based on the national standard system of luminance (model: V11.04.18). This system was used to calibrate the luminance responsivity scale of standard photometer and luminance standard integrating sphere.When using the national standard system (V11.04.18) to calibrate the luminance standard integrating sphere (model: LN3; S/N:05B840), an uncertainty of U=0.73% for k=2, where k is the *, was found [1]. On the other hand, we calibrated the luminance responsivity scale of a standard photometer system (VMI-PR-006) based on the national standard system of luminance (V11.04.18) and compared it to the luminance responsivity scale calibrated at NMIA (National Measurement Institute Australia) with En=0.13<1, where En is *. This standard system is used for the calibration and verification of measurement devices within the luminance measurement requirements specified by the Vietnam technical documents.

12-18

Authors: Huong Thi Le, Tien Anh Nguyen, Thu Hoang Vo, Michał Michalak, Tam Hoang Luu, Ha Tran Nguyen*

Lanthanum orthoferrite (LaFeO3) photocatalysts were synthesized by a facile and cost-effective co-precipitation method via the hydrolysis of La (III) and Fe (III). The characteristics of LaFeO3 were investigated through thermogravimetric analysis (TGA), X-ray diffraction (XRD), UV-Vis diffuse reflectance spectroscopy (DRS), vibrating sample magnetometry (VSM), and transmission electron microscopy (TEM). During the investigation of the applicability of LaFeO3 as a photocatalyst for the atom transfer radical polymerization (ATRP) of methyl methacrylate monomer under UV irradiation, the obtained poly(methyl methacrylate) exhibited a high molecular weight and narrow polydispersity index. In addition, the LaFeO3 can be recovered via application of a magnetic field and reused for the atom transfer radical polymerization process.

24-29

Authors: Thi Bich Van Pham, Minh Hao Hoang*

A coagulation cascade forms through proteolytic reactions and involves different factors. There are two coagulation pathways, including intrinsic and extrinsic mechanisms, which converge by the formation of factor Xa. Factor Xa plays a crucial role in the formation of the complex with factor Va in the presence of calcium ions and phospholipids. This complex converts prothrombin to thrombin, which leads to the formation of a very strong fibrin clot. Much effort has been devoted to the efficient interference of this enzyme cascade by the inhibition of factor Xa due to its important effect. (R)-3-amidinophenylalanine inhibitors are known inhibitors of factor Xa reported so far. In the present work, a two-dimensional quantitative structure activity relationship (2D-QSAR) was performed on 50 (R)-3-amidinophenylalanine inhibitors (the training set) with respect to their pKi values toward factor Xa, where pKi=-logKi, and Ki is the inhibition constant, to develop a mathematical model that depends on the physicochemical properties of the inhibitors. Partial least squares regression (PLSR) was used to yield a QSAR model containing molecular descriptors that significantly contribute to pKi values. The statistically significant parameters of the model, such as squared correlation coefficient, R2=0.834, root mean square error, RMSE=0.210, cross-validated Q2cv=0.789, and cross-validated RMSEcv=0.237, were obtained for the training set. The developed 2D-QSAR model was applied to predict the pKi values of the 62 inhibitors. Furthermore, the reliability of the model was also confirmed via statistically significant parameters obtained from validation on an external set.

34-37

Authors: Thi Thoi Bui*, Dai Quang Ngo, Van Loc Tran

The paper describes the preparation of new sulfonylurea derivatives from sulfonyl carbamate 6 with amino derivatives. The process for synthesis of the key compound 6 included three steps starting from compound 6-chloronicotinic acid 1, which are readily available chemicals. The compound 1 in the presence of triethylamine in anhydrous acetone solvent and ethyl chloroformate to obtain 6-chloronicotinic (ethyl carbonic) anhydride compound 3. The compound 3 were subsequently reacted with compound 4 to obtain compounds 5. The sulfonamides 5 was refluxed with ethyl chloroformate in present anhydrous potassium carbonate in dry acetone to obtain the key compounds 6. The total yield of the key intermediate compound 6 is about 81.35%, related to the starting materials. Finally, threesulfonylurea derivatives 7a-c were synthesized by condensation of 6 with various of amines in toluene. Their structures have been determined by IR, MS and 1H and 13C NMR spectroscopic methods,and their α-glucosidase inhibitory activity have been evaluated.

41-47

Authors: Ha Lan Nguyen, Viet Ky Nguyen, Van Ngo Dau, Thi Phi Oanh Tran*

Water is extremely important to all life currently, the Cu Chi district has been provided with one hundred percent clean water. However, due to long-standing habits and easy extraction, citizens are still using groundwater daily for water consumption and cooking.Therefore, in this study, the use of groundwater from the middle-upper Pleistocene aquifer in the Cu Chi district of Ho Chi Minh city, for domestic and drinking purposes was investigated. In terms of pH and Fe, NH4+, NO3-, As and Mn content, data were collected from central water supply stations under the operation of the Centre for Rural Water Supply and Sanitation (CERWASS). Furthermore, samples collected from 94 households and water supply stations were also evaluated for groundwater quality via pH and Fe, As, Hg, Cd, Pb, Cr6+ and CN- concentration. On the other hand, a human health risk assessment for carcinogenic substances (As) and non-carcinogenic substances (Mn) was performed by a variety of assessments including the susceptibility to contamination according to the DRASTIC index, which weights water risks by applying a semi-quantitative model. Because pollution is inevitable with today’s modernization and industrialization, these research results contribute to management and control measures deeply needed to achieve and maintain a safe water supply, thereby ensuring the health and safety for the communities in the Cu Chi district

56-64

Authors: Duy Tue Nguyen, Tri Nhut Do*

Solar energy is a free and nearly endless source of energy. Vietnam has the advantage of harnessing solar energy for many essential purposes because of its geographic location in the tropics. This allows electricity usage to be minimized in solar chemistry and energy conversion from solar energy into electricity; or to completely replace electricity usage in applications such as heating, cooling, ventilation, water treatment, cooking processes, and heating processes. In this paper, three solar water heating systems with a heat pump are designed for resorts located at three famous tourist destinations in Vietnam: Phu Quoc island and the towns of Bao Loc, and Sa Pa. These places represent the Southern, Central, and Northern regions of Vietnam, respectively. Ecotect and Grasshopper software applications are employed with the latest weather, heat, and radiation data and was obtained from climate.onebuilding.org. Data analysis is based on Ecotect software and the computational design is done in Grasshopper software. These software applications show that Phu Quoc island is the most efficient place to exploit solar energy, followed by Bao Loc, which is lower due to the fog, and Sa Pa, where solar radiation is low. In order to increase the water heating efficiency in places with very low solar radiation, a heat pump is considered along with a conventional solar water heating system and optimum azimuth angle of 180o South for the solar collector. This method is an efficient solution that can be applied in Sa Pa as well as in other places in Vietnam where there is a lack of solar radiation. The solar energy factor (SEF) is significantly increased from 14.37 to 57.47 and the solar fraction (SF) per year is increased from 93.5 to 98.3% using this method.

71-76

Authors: Le Thi Quyen, Nguyen Thi Minh Thu, Le Thi Minh Phuong, Nguyen Thi Trang*

The objectives of this work were to accurately evaluate testing kits that analyse sperm DNA fragmentation in infertile men and to provide a comparison of an improved testing kit (SSSperm testing kit) to the existing Halosperm testing kit in an analysis of sperm DNA fragmentation. A cross-sectional study was conducted on 300 semen samples from infertile men with a sperm concentration ≥1 million/ml using the Bland-Altman, T-test, and Pearson test for statistical study. The SSSperm testing kit had a coefficient of variation of CV%=2.26%<5% and ttn=0.970.05). In conclusion, the SSSperm testing kit for the analysis of sperm DNA fragmentation is qualified as determined from quantitative tests, and the SSSperm testing kit is equivalent to the Halosperm testing kit.

83-88

Authors: Van-Tuan Tran*, Tao Xuan Vu

Penicillium digitatum exists in nature as a causative agent of green mould disease in citrus fruits at the postharvest stages. Inspections of the molecular mechanism of the host invasion by P. digitatum usually require suitable selection markers for genetic manipulation. In this study, we recruited the phleomycin resistance gene as a selection marker for the genetic transformation of P. digitatum using Agrobacterium tumefaciens. The results showed that the growth of the wild strain P. digitatum PdVN1 from fungal spores is quite sensitive to phleomycin and is inhibited at a concentration of 50 μg/ml, whereas growth from fungal mycelium is more tolerant and completely suppressed at a concentration of 200 μg/ml. Under optimised conditions, the A. tumefaciens-mediated transformation (ATMT) efficiency of P. digitatum with the phleomycin resistance marker could reach over 1000 transformants per 106 spores. All the tested transformants presented the integration of T-DNA in their genomes and were mitotically stable for the phleomycin resistance. Furthermore, the results also revealed the success for heterologous expression of the DsRed fluorescent gene in the fungus, in which the strong red fluorescent signal could be observed over the whole fungal mycelium and spores. Our work demonstrates for the first time that the phleomycin resistance gene can serve as a reliable selection marker for A. tumefaciens-mediated transformation of the postharvest pathogen P. digitatum. This selection marker can be exploited for T-DNA insertional mutagenesis and for functional investigations of target genes involved in citrus decay by P. digitatum.

3-16

Authors: Vu Dinh Quang, Van Quang Doan, Van Nguyen Dinh, Nguyen Dinh Duc*

The shortage of reliable datasets and resource assessments, resource variations, and lack of marine planning are the technical challenges facing offshore wind energy development in Vietnam. This pioneering paper comprehensively addresses these challenges by first screening available datasets to select cross-calibrated multi-platform (CCMP) data and validating them with measurements. The resource is divided into four zones of 100 NM-width from the coastline. The wind energy density (WED) and capacity factor (CF) are calculated using an 8 MW reference turbine. The assessment of the zoned resource and infrastructures is based on the location of synchronous power sources and ports, along with the variation of WED and CF. Zone 3, comprising of the Binh Thuan and Ninh Thuan seas, the southern part of Zone 2 (Phu Yen and Khanh Hoa), and the northern part of Zone 4 (Ba Ria and Vung Tau) are found to have the highest wind energy potential, where the annual accumulated WED is 80 GWh/km2. The five year CF and average wind speed in Phu Quy island were 54.5% and 11 m/s, respectively. These zones, with moderate resource variation and excellent ports are the most suitable for offshore wind energy development. Zones 1 and 4 are recommended for far-offshore wind farms. This work is useful to various environmental groups and is a crucial input to marine and power planning

23-27

Authors: Thu Vo Hoang, Huong Thi Le, Nhung Thanh Thi Truong, Michał Michalak, Ha Tran Nguyen*

In this research, a novel organic photocatalyst of 10-(perylene-3-yl-10H-phenoxazine (PHP) has been successfully synthesized from perylene and phenoxazine via Buchwald-Hartwig C-N coupling. The chemical structure of catalyst was determined via FT-IR, proton nuclear magnetic resonance (1H-NMR) spectrum and optical properties were investigated through UV-Vis spectroscopy. The PHP has been used as the reducing photoredox catalyst for organocatalyzed atom transfer radical polymerrization (O-ATRP) under UV irradiation. The well controlled molecular weight of the methyl methacrylate polymers have been obtained nearly 80% with a low polydispersity index under 1.5.

32-37

Authors: Thi Tuyet Mai Phan*, Thi Sen Ngo

Pectin and cellulose were successfully extracted from passion fruit peel waste. The maximum pectin yield of the process was 12.60% at pH=2 for 1.5 h. The pure cellulose obtained from the passion fruit peel waste was prepared by refluxing of the passion fruit peel powder with 1 M NaOH and 1.25 M HNO3 solutions at 90°C for 1 h and 1.5 h, respectively. The passion fruit peel cellulose was converted to carboxymethyl cellulose (CMC) by etherification. The pure cellulose was soaked in a mixed solution of isopropyl alcohol and NaOH for 1.5 h. After that, it was reacted with cholroacetic acid at 70°C for 1.5 h. The optimum conditions for carboxymethylation were 5 g cellulose, 2.0 g cholroacetic acid, and 15 ml 20%w/v NaOH. The optimised product had a degree of substitution (DS) of 0.78 and was used as constituent in a biopolymer.

43-49

Authors: Pham Minh Xuan*, Le Hai Tran*, Huynh Ky Phuong Ha, Mai Thanh Phong, Van-Huy Nguyen, Chao-Wei Huang

Herein, a polyamide-based thin film composite (TFC) membrane was fabricated for the removal of arsenic (As) from water. The polyamide thin film was synthesized through interfacial polymerization (IP) onto a polysulfone porous substrate. A Box-Behnken design of response surface methodology was used to investigate the effect of preparation conditions, including piperazine (PIP) concentration, trimesoyl chloride (TMC) concentration, and reaction time on the As rejection and permeate flux of the synthesized membrane. The separation performance of the prepared membranes from 15 designed experiments was conducted with an arsenate (Na2AsHSO4) solution of 150 ppm at a pressure of 40 psi and a temperature of 25oC. The analysis of variance revealed the regression models to be adequate. From the regression analysis, the flux and As rejection were expressed by quadratic equations as a function of PIP concentration, TMC concentration, and reaction time. It was observed that the PIP concentration, TMC concentration, and reaction time had a significant effect on the flux and As rejection of the polyamide membrane. Moreover, a strong impact from the interaction of PIP and TMC was also observed on rejection of the resulting membrane. Using the desirability function approach to analyse the regression model, the optimal preparation conditions of the polyamide membrane were a PIP concentration of 2.5 wt.%, TMC concentration of 0.11 wt.%, and reaction time of 40 sec. The membrane exhibited a good As rejection of 95%.

55-61

Authors: Nguyen Xuan Thang*, Bui Manh Cuong, Dang Ngoc Ha, Do Van Dung, Sudha Nair, M.T. Vinayan, Gajanan Saykhedkar, Raman Babu, Doan Thi Bich Thao, Tran Quang Dieu, Nguyen Chi Thanh, P.H. Zaidi

The results of testing the International Maize and Wheat Improvement Center’s (CIMMYT’s) hybrid combinations, developed from hybrid 790 F2:3 lines and 10 parental lines, using two testers (CML451 and CLO2450) under optimal and managed drought conditions in Ninh Thuan, Vietnam, show that the average grain yield of the biparental (BP) groups of heterosis groups A and B is, respectively, 2.58-3.65 tons/ha and 2.56-2.76 tons/ha in drought conditions, and 4.24-5.02 tons/ha and 5.41-5.93 tons/ha in well-watered conditions, respectively. By genotyping eight BP populations with 39,846 single nucleotide polymorphism (SNP) markers, CIMMYT experts identified 15 important gene regions that regulate grain yield associated with 15 SNP markers on chromosomes 3, 4, 5, 6, 7, 8, 9, and 10 which is useful for applying molecular markers in breeding drought-tolerant maize. On that basis, the Maize Research Institute of Vietnam studied and genotyped three populations, including 450 F2 families, with 96 SNPs using the Kompetitive Allele Specific PCR (KASP) genotyping method. The result was that 57 SNP markers related to drought tolerance were found useful to these populations. In addition, 27 F2 families demonstrating drought tolerance and high grain yield were selected as primary materials for breeding maize hybrids tolerant to stresses and adaptive to climate change.

69-73

Authors: Minh-Tan Vo, Van-Tai Nguyen, Thi-My-Chi Vo, Thi-Nhu-Phuong Bui, Thanh-Son Dao*

In this study, the detrimental effects of trace metals on the growth of phytoplankton and the phytoremediation potential of microalgae from Vietnam are elucidated. Two green algae Scenedesmus accuminatus var biseratus and Scenedesmus protuberans, along with the diatom species Cyclotella sp., were exposed to chromium (Cr) and cadmium (Cd) at three distinct concentrations ranging from 5-761 μgl-1 and 18-667 μgl-1, respectively, over a period of 14 days. The results indicated that S. acuminatus var biseratus and Cyclotella sp. were relatively tolerant to Cr, even at the highest test concentration, while the growth rate of S. protuberans was significantly inhibited when exposed to 660 μgl-1 of Cr. Only Cyclotella sp. showed a high Cd tolerance, whereas Cd at concentrations of 493 and 607 μgl-1 prohibited the growth rate of S. acuminatusand S. protuberans, respectively. Moreover, at the concentrations tested, all three algal species could remove 90-100% of the Cr out of the test medium. The diatom Cyclotella sp. could reduce up to 99% of Cd whereas the two green algae could only do not remove more than 13% of Cd from the test medium.We strongly recommend the Cyclotella sp. as a candidate for phytoremediation in metal-contaminated water. Our results contribute vital information toward solutions that environmental experts and managers are searching for to resolve pollution caused by trace metal contaminants

85-89

Authors: Minh Nhat Phan, Nguyen Van Nhi Tran, Jimmy Yu, Tan Phong Nguyen*

Slaughterhouse wastewater (SWW) possesses very high organic and nutrient concentrations and its residues are moderately solubilized, which leads to pollution affecting the environment and human health. The objective of this study was to investigate the effective removal of ammonium in slaughter wastewater by up flow anaerobic sludge blanket (UASB) technology combined with an expanded granular sludge bed (EGSB) using anammox and PVA gel as the biomass carrier. Ammonium loading rates (NLRs) increased from 0.25 kgN-NH4+/m3.d to 0.75 kg N-NH4+/m3.d with hydraulic retention times (HRTs) of 12, 6, and 4h. The system was operated in 2 phases. In phase 1, the removal of ammonium by employing the combination of UASB technology and EGSB using anammox was examined. The removal efficiencies of nitrite were 52% (NLRs=0.25 kgN-NH4+/m3.d), 69% (NLRs=0.5 kgN-NH4+/m3.d) and 64% (NLRs=0.75 kgN-NH4+/m3.d). On the other hand, the removal efficiencies of ammonium were about 37% (NLRs=0.25 kgN-NH4+/m3.d), 64% (NLRs=0.5 kgN-NH4+/m3.d) and 55% (NLRs=0.75 kgN-NH4+/m3.d). In phase 2, a PVA gel was supplied to the EGSB as the biomass carrier for growing the anammox sludge. The result showed that the removal efficiencies of nitrite were about 55% (NLRs=0.25 kgN-NH4+/m3.d), 77% (NLRs=0.5 kgN-NH4+/m3.d), and 73% (NLRs=0.75 kgN-NH4+/m3.d). In addition, the removal efficiencies of ammonium were about 56% (NLRs=0.25 kgN-NH4+/m3.d), 68% (NLRs=0.5 kgN-NH4+/m3.d), and 60% (NLRs=0.75 kgN-NH4+/m3.d)

3-8

Authors: Le Minh Hieu*, Truong Thi Hieu Hanh, Dang Ngoc Hoang Thanh

We propose a new monotone finite-difference scheme for the second-order local approximation on a non-uniform grid that approximates the Dirichlet initial boundary value problem (IBVP) for the quasi-linear convection-diffusion equation with unbounded nonlinearity, namely, for the Gamma equation obtained by transformation of the nonlinear Black-Scholes equation into a quasilinear parabolic equation. Using the difference maximum principle, a two-sided estimate and an a priori estimate in the c-norm are obtained for the solution of the difference schemes that approximate this equation

14-28

Authors: Nguyen Thi Thao*, Mai Thuy Dung, Pham Vu Loc, Nguyen Thi Kim Ha, Pham Ngoc Diep, Pierre Darriulat

The Vietnam National Space Center has recently established an observatory in Hoa Lac, near Ha Noi. The observatory is equipped with a 50 cm diameter Ritchey-Chrétien optical telescope. The authors report on first measurements illustrating its performance and demonstrate its excellence as a training tool for university students at bachelor’s and master’s degree levels

35-39

Authors: Tran Thi Kim Ngan, Dao Nguyen Khoi*

The aim of the present study is to assess the effect of hydropower dams on the streamflow in the Be river basin using the Soil and Water Assessment Tool (SWAT). Model calibration and validation of SWAT were conducted using the historical data collected from two stream gauges, namely Phuoc Long and Phuoc Hoa, and the obtained results indicated that SWAT shows a good reliability in reproducing streamflow with R2>0.90 and NSE>0.70 for both periods of calibration (1980-1990) and validation (1991-1993). Considering the results of SWAT’s calibration, the hydrological impact on the streamflow needs to be taken into consideration. The study results show that the separate impact of each hydrological dam (Thac Mo reservoir, Can Don reservoir, and Srok Phu Mieng reservoir) significantly increases streamflow in the dry season (89-101%) and decreases it in the wet season (6-33%). Moreover, there is a considerable rise in the dry season (89%) and a significant decline in the wet season (33%) of streamflow under the combined impact of the three dams.

48-52

Authors: Tran Van Do

The production of fine roots (diameter ≤2 mm) contributes considerably to carbon cycling in forest ecosystems. Fine roots constitute a significant organic matter pool with high net primary productivity and turnover. In this study, fine root decomposition, mortality, and production were estimated at a Quercus serrata Murr. plantation in Japan by using rates of diameter-dependent root mortality, decomposition, and the thickening method employed. Sequential soil core and litter bag techniques were used to collect field data. The experiments were set up in a 20×20 m plot. The data were collected five times (May, August, November, and December 2013, as well as April 2014) during a one-year period, and fine roots were classified into ones with a diameter of ≤1 mm and others of 1-2 mm. The results indicate that fine root decomposition, mortality, and production in a Q. serrata plantation are season-dependent and are higher in the summer compared to the winter. In the summer, production reached 1.365 g m-2 day-1, while it was lower than 0.132 g m-2 day-1in the winter. The total fine root production of the Q. serrata plantation was 1.364 tonnes ha-1 year-1. The mortality was 0.440 tonne ha-1 year-1, and the amount decomposed to return nutrients to the soil was 0.108 tonne ha-1 year-1.

58-63

Authors: Chu Thanh Binh*, Tran Van Tuan, Tran Bao Tram, Bui Thi Viet Ha

The filamentous fungus Paecilomyces is currently being developed as a biocontrol agent against plant parasitic nematodes, which often cause black leaf disease in pepper and coffee trees. Nematode eggs and cuticles are the infection sites for biocontrol agents that penetrate those areas by the production of lytic enzymes. Paecilomyces variotii NV01 was isolated from pepper soil from the Dak Lak province. The purpose of this work is to study the activity of protease and chitinase in the strain Paecilomyces variotii NV01. The protease activity was determined to be 82.3 U/ml in a 0.65% casein substrate concentration after 84 hours of culture, which was 6 folds higher than with a basal medium (12.7 U/ml). Exo-chitinase activity was found to be 37.28 U/ml after 84 hours of culture in a chitin substrate concentration of 0.75%, which is 4 folds greater than the basal medium. It was found that adding Ca2+ to the medium drastically altered chitinase activity, increasing it by 10.5%.A 5 mM concentration of Ca2+ was found to affect chitinase activity but not protease activity. Furthermore, the percentage of Meloidogyne sp. nematodes killed by Paecilomyces variotii NV01after 96 hours of culture was 50.4%. Further study should be carried out in order to use this fungal strain to control plant parasitic nematodes.

70-75

Authors: Pham Thanh Luu

Harmful cyanobacterial blooms have become a global threat to human health and aquatic biota around the world. While the ecotoxicity of cyanobacterial toxins such as microcystins (MCs) has been studied extensively, the toxicity of non-toxin producing cyanobacteria has not been evaluated to the same extent. In this study, five strains of Microcystis wesenbergii were isolated from the Tri An reservoir and cultured under laboratory conditions. Microscopic observation was used for morphological identification. The MCs concentration was measured by high-performance liquid chromatography(HPLC). The microcrustacean (Daphnia magna) was exposed to different concentrations of crude extracts in a series of acute (48h) and sub-chronic (15 day) toxicity experiments. The acute assay showed that crude extract from all isolated strains of M. wesenbergii generated toxic effects on D. magna, but no variant of MCs was detected in the cultures of M. wesenbergii. The 48 h EC50 values of crude extracts of M. wesenbergii on D. magna ranged from 307.2-491.5 mg dry weight (dw)/l. Sub-chronic exposure of D. magna to the crude extract of M. wesenbergii at concentrations of 1, 10, 40, and 120 mg dw/l resulted in a decline of survival rates with dose dependence. Both maturation and reproduction of parent D. magna were inhibited with increasing concentrations of crude extract. This finding indicated that crude extracts from non-MC-producing M. wesenbergii isolated from the Tri An reservoir had significant acute and chronic toxic effects on D. magna

82-87

Authors: Le-Thu Quach, Thi-My-Chi Vo, Van-Tai Nguyen, Thanh-Son Dao*

Anthropogenic activities such as industrial production, mining, agriculture and transportation are among the main causes for the increase of trace metal concentrations in the environment, especially in water bodies. In this study, we evaluated the chronic impacts of lead (Pb) and arsenic (As) on Daphnia magna, a crucial organism to aquatic ecosystems, at several concentrations (0, 5, 25, 50, 150 and 250 μgl-1 of Pb and 0, 5, 25, 50 μgl-1 of As) for 21 days. The organism’s life history traits, including survivorship, maturation, and reproduction, were recorded daily. In addition, the survival rate of the offspring exposed to 50 μgl-1 Pb was also recorded when the animals were raised in (i) a Pb-containing medium and Pb-free medium for 8 days. The results showed that As, at all the test concentrations, did not only negatively affect the survival and cause a delay the maturation, but also reduced the reproductive performance of the animal, especially at the highest concentration. Compared to the control, the survivorship and reproduction of the D. magna exposed to Pb at the highest concentrations (150 and 250 μgl-1) declined dramatically, and it took a longer time to reach maturity. On the other hand, almost all of the recorded life history traits of the organisms exposed to 5, 25 and 50 μgl-1 of Pb were relatively similar to those from the control. However, Pb at the concentration of 50 μgl-1had detrimental effect on survival of Daphnia’s F1 generation after the 8-day experiment. An abnormality of the metal-exposed D. magna was also observed. An impairment of the daphnids was observed upon exposures to As and Pb at concentrations within the Vietnam guideline values for surface water safety. Hence, further investigations are suggested to adjust the guidelines related to As and Pd for the protection on environmental quality and ecological health.

3-8

Authors: R.S. Omar*, S. Hashim, S.K. Ghoshal

This paper reports on the synthesis and characterisation of Dy2O3-doped magnesium borate (MB) glasses containing different modifiers, lithium, calcium, and sodium oxides. Glasses composed of (70-z)B2O3-20Li2O; CaO; Na2O-10MgO-zDy2O3 (where 0.05≤z≤0.7 mol%) were prepared using the melt-quenching method. X-ray diffraction (XRD) pattern of the as-quenched samples verified their amorphous character. Differential thermal analysis (DTA) confirmed excellent glass-forming ability and thermal stability in the range of 0.60-0.67 and 0.18-0.82, respectively. The energy dispersive X-ray (EDX) spectra verified the precise elemental traces in the studied glasses. Furthermore, MB glasses doped with 0.1 mol% of Dy2O3 and modified with lithium oxide were found to have the best soft tissue equivalence (Zeff≈8.13). In short, the proposed MB glass system doped with dysprosium ions (Dy3+) was established as effective for accurate radiation detection in emergency situations.

12-15

Authors: Van Kieu Nguyen, Thuc Huy Duong*

This study entails a continuation of the phytochemical study regarding the lichen Usnea baileyi collected in Lam Dong province. Eight compounds, 8'-O-methylprotocetraric acid (1), protocetraric acid (2), virensic acid (3), subvirensic acid (4), barbatic acid (5), diffractaic acid (6), 4-O-demethylbabartic acid (7), and atranorin (8), were isolated using various chromatographic methods. Their chemical structures were elucidated through spectroscopic analysis as well as through a comparison of their data with that in the literature.

25-32

Authors: Thanh-Truc Nguyen, Minh-Vy Huynh, Thanh-Hai Le, Thi-Thu-Hien Pham*

Breast cancer is a well-known health issue that has been a major focus for healthcare professionals for quite some time. Still, the most common noninvasive diagnostic tool - mammography - results in a high false positive rate along with risks of exposure to radiation. These disadvantages are magnified and become more severe when screenings are done repeatedly. To tackle this problem, we introduce a novel framework for uncomplicated diagnosis of breast cancer. Our method utilizes the analytical technique of Mueller matrix decomposition and Stokes vector polarimetry from a polarized light system consisting of a helium-neon laser (wavelength of 632.5 nm), a quarter-wave plate, polarizers, and a Stokes polarimeter. Thus, this technique introduces no radiation. We extracted nine optical parameters of a breast cancer cell line - BT474 - and determined the relationshipand separation power of these parameters to cancerous cells and healthy cells. Specifically, the samples were designed as a two-dimensional cellular model of malignant breast tumours that combined a range of four cell densities - 104, 105, 106, and 107 cells - per an area of 9 cm2.Nine optical parameters - orientation angle of linear birefringence (α), retardance or linear birefringence (β), optical rotation angle or circular birefringence (γ), orientation angle of linear dichroism (θd), linear dichroism (D), circular dichroism (R), degrees of linear depolarization (e1 and e2), and degree of circular depolarization (e3) - were extracted from a total of 40 samples using the polarized light system. The results revealed the positive correlations between three cell densities (104, 105, and 106) and the orientation angle of linear birefringence (R2 = 0.8038), linear birefringence (R2 = 0.8627), and linear dichroism (R2 = 0.9662). Meanwhile, both the orientation angle of linear dichroism and circular dichroism illustrated the negative correlation with that range of cell densities with R2 = 0.9983 and 0.9447, respectively. This proves that the optical parameters measured demonstrate significant association with the cells’ characteristics and thus, the proposed method could pave the way for an accessible diagnosis of breast cancer

40-44

Authors: Dao Thi Anh Phan*, Nga Kieu Thy Vo, Huy Minh Tran, Phan Thi Cam Bui

Changes in melanosis, microbiology, and fat oxidation in Pacific white shrimps (Litopenaeus vannamei) when treated with Houttuynia cordata extract (designated E-DC) were monitored during cold storage for seven days at 20C. Whole shrimps treated with E-DC solution (0.025%, w/v) revealed slow growth of total aerobic microorganisms, Enterobacteriaceae and Pseudomonas aeruginosa, throughout cold storage in comparison to the control sample treated by water (p<0.05). The changes in pH, grey value, and TBARS value (thiobarbituric acid reactive substances) of shrimp samples treated with 0.025% E-DC solution were lower than those of control samples (p<0.05) and not different significantly in comparison to the 1.25% (w/v) sodium metabisulfite (SMS) samples (p>0.05). These results suggested the potential of using natural compounds from vegetable extraction as a safe and effective alternative for commercial chemical-derived preservatives in shrimp storage.

52-56

Authors: Tien Sang Trieu*, Van Khoa Tran, Ha My Nguyen, Thi Thu Ha Nguyen, Quang Tung Le, Minh Ngoc Phung, Minh Quang Diep, Huong Ly Vu

Bacterial vaginosis (BV) is one of the most common vaginal infections in women of reproductive age. If not treated promptly, the disease can lead to serious complications affecting the fertility and long-term health of women. Research on BV requires effort from a variety of disciplines and its treatment can only be determined by coordinated actions in research and treatment. Currently, BV diagnostic methods are often based on culture techniques and Gram staining. However, molecular biology research is developing and has proved to more advantageous for identifying key pathogens. Combining both methods, we conducted a study to develop a diagnostic procedure using multiplex polymerase chain reaction (M-PCR) for simultaneous and accurate detection of the bacterial species that cause BV, incurring minimal costs and time for testing.

61-70

Authors: Hoang-Dung Tran*, Thanh-Tri Do, Tuan-Loc Le, Minh-Ly Tran Nguyen, Cong-Hoat Pham, Michael Melkonian

The green microalga, Haematococcus pluvialis, is currently cultivated for natural astaxanthin in suspended systems. Immobilised cultivation in a twin-layer (TL) porous substrate bioreactor is a potential revolution in microalgal biotechnology worldwide. For the first time in Vietnam, small-scale (0.05 m2) and large-scale (2 m2) biofilm-based photobioreactor systems arranged at an angle of 150 were successfully designed, assembled, and operated; the temperature, humidity, air, and light conditions for H. pluvialiscultivation were successfully controlled. Studies were conducted of both systems to determine theoptimal storage time of algae after harvest from suspension before inoculation into the TL system, carbon dioxide supply method, light intensity, and initial cell density. In the 0.05 m2 and 2 m2 systems, dry biomass productivity reached 12 g m-2 d-1 (3% astaxanthin content in the dry biomass) and 11.25 g m-2 d-1 (2.8% astaxanthin) after 10 days of cultivation. The 2 m2biofilm-based photobioreactor system provides many advantages in scaling up astaxanthin production from H. pluvialis.

77-80

Authors: Nguyen Van Thang, Le Ngoc Cau*, Makoto Kato, Satoshi Sugimoto

This paper presents a multi-criteria assessment approach for the prioritisation of low-carbon technologies for the waste sector in order to enable the implementation of Vietnam’s nationally determined contributions (NDCs) in terms of the Paris Agreement. A four-step approach is developed for assessing and prioritising low-carbon technologies for the waste sector using this approach. A set of five criteria and indicators are defined for multi-criteria assessment. Based on mitigation options defined in the NDCs, a shortlist of 26 technological options are defined. The multi-criteria assessment and prioritisation is conducted based on the shortlist. The assessment results in eight prioritised low-carbon technologies. Of the eight technologies prioritised, semi-aerobic landfill, which is a low cost and relatively simpler technology than the other technologies evaluated and can contribute to greenhouse gas emission reduction, is given the highest priority. The technical, financial, and social and environmental feasibility of each of the technologies evaluated is presented.

90-96

Authors: Ngoc Diep Nguyen1, Thi Le Hang Tran, Van Der Heiden Dion, Diep Anh Tuan Dinh, Pham Dang Tri Van*

The research was conducted to assess the feasibility of the installation of a rainwater harvesting system for households facing difficulties in using tap water and groundwater for domestic purposes in a coastal area of the Vietnamese Mekong delta - the case study of the Vinh Chau town, Soc Trang province. Direct household interviews and literature review were executed to comprehend the current state of domestic water consumption. According to the research results, Vinh Chau was among the towns seeing moderate rainfall in the delta (~ 1,776 mm/year), and rainwater was used frequently by the local people. However, local households did not employ proper harvesting techniques, hence the harvested rainwater did not meet the required quality for domestic use. Additionally, difficulties in using tap water, groundwater, and surface water were notable. The quality of tap water was not suitable for household consumption because of the presence of aluminum, and the price was high relative to the household’s income. Salinization of surface and groundwater, as well as degradation in quantity of ground water, made water of acceptable quality scarce. The research results also indicated that the use of rainwater harvested by a proper system demonstrated a higher cost efficiency than that of other water resources. Therefore, the installation of a rainwater harvesting system for water supply should be encouraged in order to provide a safe and efficient alternative water source for domestic use, and to contribute to the relief of domestic water-related issues and pressure on groundwater extraction in the study area