Vietnam Journal of Science, Technology and Engineering

7-12

Authors: Van phuc Dinh*

Pomelo fruit peel, an organic waste, was utilised as a biosorbent to remove Ni(II) from aqueous solutions. Some major factors influencing Ni(II) uptake such as pH, adsorption time, and initial Ni(II) concentration were examined. Several isotherm and kinetic models including the Langmuir, Freundlich, Sips, pseudo-first-order, pseudo-second-order, and intra-diffusion models were fit to the experimental data. Results showed that the Ni(II) uptake obtained an equilibrium at pH=6 after 80 min at 303 K. The Sips isotherm model described the Ni(II) adsorption better than other models and the monoadsorption capacity calculated from the Langmuir model was 9.67 mg/g. The adsorption of Ni(II) followed pseudo-second-order kinetic models with three stages.

20-24

Authors: Thi Hien Dinh*, Minh Hai Nguyen

The synthesis, structure, and luminescent propertiesof a samarium(III) complex (A2) containing benzoyltrifluoroacetone (HTFPB) and 1,2-bis[(anthracen-9-ylmethyl)amino]ethane (BAAE2) ligands are herein reported. The structure of A2 has been elucidated by infrared spectroscopy and single crystal X-ray diffraction. X-ray crystallographic analysis demonstrated that A2 has a mononuclear structure with a formula of Sm(TFPB)3(BAAE2) in which Sm3+ ion is coordinated to six O-atoms from three TFPB ligands and two N-atoms from one ancillary ligand (BAAE2). UV-Vis data show that A2 strongly absorbs in the region of 220-400 nm. Nonetheless, A2 gives poor emission due to a quenching effect of the anthracenyl moiety

32-38

Authors: Hai Thanh Le*, Hien Thi-Thu pham

Intravenous access for blood collection and other related therapies is one of the most frequently practiced procedures in the modern medical system. The procedure requires complex training and experience, as it might cause dangerous nerve damage and subcutaneous bleeding. This paper proposes a dorsal hand vein detection method utilising the near-infrared (NIR) imaging device to segment and visualise the subcutaneous vein patterns on the skin directly. Applying NIR light has received substantial attention because of its non-invasive and revealing substantially more information than the visible one. The proposed method is divided into the low- and high-level processes. The captured image is smoothed and enhanced to make the vein patterns clearer in the low-level process. The pre-processed image is then segmented step by step to extract the vein features and eliminate the pseudo-vein regions precisely. Lastly, the detected veins are thinned to reduce the thickness and projected back onto the acquired image in the high-level process. The proposed method performs effectively in detecting the clear dorsal hand veins through the experiment with a processing time of 0.61s for the high-resolution image.

45-51

Authors: Nhat Tam Le*, Nguyen Que Anh Huynh, Nhu Khue Doan, Thuy Xuan Uyen Phan, Ba Thanh Nguyen, Sao Mai Dam, Thi Van Thi Tran, Le phuong Lien Nguyen, Van Hai Chu, Huynh Anh Vu Truong

In this study, the sensory, microbiological, and biochemical qualities were used to examine the quality of Pacific white shrimps (Litopenaeus vannamei) preserved at 0°C during a 10-day period. The sensory quality was evaluated by a quality index (QI) that resulted from a quality index method (QIM) scheme. Meanwhile, the total viable count (TVC) and K-value were used to assess the microbiological and biochemical qualities of the shrimp. On day 9, the results from TVC and QIM have shown that the shrimp showed signs of spoilage, corresponding to a log CFU/g of 6.4 and a QI of 21.37, which is unacceptable to consumers. The QI increased linearly with storage days therefore the remaining shelf-life of the shrimp was estimated from a linear regression equation. In particular, this study found a linear relationship between QI, K-value, and hypoxanthine content. Furthermore, hypoxanthine itself could be considered as an independent quality index like the K-index. In conclusion, the quality of Pacific white shrimp was categorized into four different classes: excellent, good, acceptable, and moderately acceptable, based on its sensory and biochemical quality indicators.

58-63

Authors: Tran Thi Hoan, Tu Quang Hien*, Mai Anh Khoa, Tu Quang Trung

The purpose of this study is to determine the appropriate level of chicken manure for the green fodder M. oleifera grown for leaf meal production as a supplement into poultry diet to improve poultry product quality (i.e., meat and egg). The experiment was conducted at Thai Nguyen University of Agriculture and Forestry, Vietnam, for two years from 2018 to 2019. The experiment consisted of four treatments (NT) represented by four different levels of chicken manure, namely, 0 tons (NT1), 10 tons (NT2), 20 tons (NT3) and 30 tons/ha/yr (NT4). Each treatment was carried out over an area of 24 m2 with 5 replicates. The experiment was the complete randomised block design. Other factors such as plantation density, nitrogen, phosphate, potassium fertiliser levels, cutting height, and cutting intervals, etc., were similar among treatments. The results showed that the leaf dry matter yield of NT1 through NT4 was 6.919, 8.131, 8.975, and 9.494 tons/ha/yr, respectively. That of the leaf crude protein was 2.244, 2.694, 3.073, and 3.357 tons/ha/yr, respectively. Increasing manure levels from 0 to 30 tons/ha/yr decreased the dry matter content in the leaves by 1.43%, increased the crude protein in leaf dry matter basic by 2.93%, and decreased crude fibre in the leaf dry matter basic by 2.24%. Based on these results and data from statistical analysis, the most appropriate level of chicken manure application for M. oleifera was at 20 tons/ha/yr.

70-73

Authors: Le Nguyen Thanh*, Nguyen phuong Thao, Nguyen Tu Minh, Trinh Khanh Huyen, Vu Thi Kim Oanh, Dinh Ngoc Thuc, Tran Thi Ngat, Nguyen Thi Phuong Lien

A chemical study on the propolis of the stingless bee Lisotrigona cacciae collected from Hoa Binh province led to the isolation of four compounds including cycloartenol (1), cochinchinone A (2), α-mangostin (3), and isomangiferolic acid (4). Mangifera indica (Xoài) and Cratoxylum cochinchinense (Thành Ngạnh Nam) were suggested to be the resin sources of the propolis. The propolis EtOH extract showed good antimicrobial activity against the Gram (+) strains B. cereus with an MIC value of 8 μg/ml. Among the isolated compounds, α-mangostin (3) was the most active and displayed strong activity against the five strains B. cereus, E. feacalis, S. aureus, P. aeruginosa, and the fungus C. albicans with MIC values of 1-2 μg/ml.

81-88

Authors: Thanh-Tri Do, Bich-Huy Tran-Thi, Binh-Nguyen Ong, Tuan-Loc Le, Thanh-Cong Nguyen, Quoc-Dang Quan, Thuong-Chi Le,Dai-Long Tran, Michael Melkonian, Hoang-Dung Tran

The production of natural astaxanthin is usually accomplished by suspended cultivation of the microalgae Haematococcus pluvialis. In this study, for the purpose of cost reduction, H. pluvialis is grown in pilot scale angled twin-layer porous substrate photobioreactors with light energy from red/blue LEDs that can produce red light, blue light, or a combination of blue-red light. The total dry biomass of the microalgae reached a maximum of 40.74 g.m-2under blue-red LEDs. The early initiation of blue-red LED illumination (on day 2) after algae immobilization in the biofilm resulted in the highest accumulation of astaxanthin in the dry biomass, which reached a maximum of 1.3% (w/w) after 10 d of culture.

7-14

Authors: Quang Minh Do, Ngoc Tri Huynh Nguyen, Thi Hong Hoa Huynh, Hong Lien Pham, Thi Thu Ho, Do Trung Kien Kieu, Ngoc Minh Huynh

Glass ionomer cement (GIC) is a particular type of cement used in dentistry. One of the most critical properties of GIC is the ability to release fluoride, which can prevent recurrent tooth decay. This study simultaneously investigated the release of fluoride, the compressive strength, and the apparent density of three GICs in deionized water (DW) and artificial saliva (AS) environments. GICs with 3 different types of glass powders were used to study. Powder B (the original) was the glass powder based on the SiO2-Al2O3-CaF2-AlPO4-Na3AlF6 system, powder HA5 was powder B supplemented with 5 wt. % hydroxyapatite powder (HA), and powder Si2 was powder B surface-treated with 2 wt. % silane JH-S69. The results of this study showed the amount of fluoride ion (F-) released during 28 days in AS was lower in comparison to the DW environment, and the rate slowed down significantly after 1 d. The F- release rate at 1-d age tended to be high as the compression strength was low. In AS, the powder supplemented with 5 wt.% HA improved the compressive strength and the cumulative amount of F- released by the GIC. After 28 d, the F- release of the GIC materials were able to be recharged in a NaF solution with 1,018 ppm F- concentration for 3 min and further fluoride ions were released in both the DW and AS environments

21-29

Authors: Hoang-Quan Dinh*, Thanh-Bang Nguyen

Geopolymers are a class of new binder manufactured by activating aluminosilicate source materials in a highly alkaline medium. This binder is considered “environmentally friendly” due to the recycling of industrial waste sources such as fly ash and blast furnace slag. However, in order to be widely used, this binder has to ensure both quality and economic efficiency. This paper focuses on the optimization of the composition of ground granulated blast-furnace slag and fly ash-based geopolymers activated by sodium silicate and sodium hydroxide solutions. Statistical models are developed to predict the compressive strength and cost of 1 ton of binder using Response Surface Methodology (RSM). In this regard, the effects of three principal variables (%Na2O, Ms and %GGBS) were investigated in which: %Na2O - mass ratio of Na2O in the alkali-activated solution and total solids; Ms - mass ratio of SiO2 and Na2O in the activated solution; %GGBS - mass ratio of ground granulated blast-furnace slag (GGBS), and total binder. Quadratic models were proposed to correlate the independent variables for the 28-d compressive strength and cost of 1 ton of binder by using the Central Composite Design (CCD) method. The study reveals that Ms has a minor effect on the strength of mortar in comparison with %Na2O and %GGBS. The optimized mixture proportions were assessed using the multi-objective optimization technique. The optimal values found were %Na2O=5.18%, Ms=1.16, and %GGBS=50%, with the goals of maximum compressive strength, the largest amount of fly ash, and reasonable cost for one ton of binder. The experimental results show that the compressive strength of the samples ranged between 62.95-63.54 MPa and were consistent with the optimized results (the variation between the predicted and the experimental results was obtained less than 5%).

36-41

Authors: Nguyen Quang Thinh

Black gram (Vigna mungo L.) is a high nutrient pulse crop. Its seed quickly and easily deteriorates after harvest, resulting in poor planting material production that must be improved accordingly by seed enhancement methods. The blue-green microalgaeSpirulina platensis contains variously beneficial substances, including macro and micro nutrients, vitamins, amino acids and antioxidants. The aim of this study is to improve the vigour and germination of black gram by priming its seeds with Spirulina platensisextract to prevent seed deterioration. Medium vigour black gram seeds were subjected to hydropriming for three hours (T2); other seeds were primed with Spirulina platensis extract at 1.5% for three hours (T3) while unprimed seeds served as control (T1). Then, the seeds were artificially aged under 40±1oC and 95±5% relative humidity for five days. The results revealed that the hydropriming and control of black gram seeds were significantly lower in all physiological and biochemical seed quality parameters than seeds primed with Spirulina platensis extract at 1.5% for three hours. Consequently, Spirulina platensis extract can effectively enhance black gram seeds and use agents in.

47-53

Authors: Le Nhat Minh, Vo Trong Nhan, Thi Thao Do, Tran Thu Huong, Le Tri Vien, Phung Thi Kim Hue*

Cancer stem cells (CSCs) are the cancer cells that have abilities to self-renew, differentiate into defined progenies, and to initiate and maintain tumour growth. They also contribute to cancer metastasis and therapeutic resistance, both of which are the principal causes of cancer mortality. Therefore, finding efficient fluorescent materials for CSC labelling and basic research is an urgent need. Thus, this research is focused on using a rare-earth element, which is the fluorescent Tb3+ nano-ion, and the CD133 monoclonal antibody to create a CSC-targeting nanocomplex (LV3). Tb3+ nanorods were silica-surface treated and -NH2 activated before being conjugated with the monoclonal antibody (mAb) against CD133, a typical CSC surface marker. The use of robust fluorescent Tb3+nanorods was to decrease the toxicity of a high-dose prober while the CD133 mAb would increase the CSC’s specific binding capacity of the LV3. The fluorescent properties of the coupled LV3 complex were measured and CSC-targeting label activities on the pluripotent human embryonal carcinoma cell line (NTERA-2) were observed. The obtained results presented fluorescent images of LV3 exposed to NTERA-2 cells under microscopy. LV3 also demonstrated that it effectively labelled up to 99.68% of the tested NTERA-2 cells. By contrast, LV3 only labelled 1.44% of the CCD-18Co human healthy cells. On the other hand, LV3 exhibited anti-CSC activity, which inhibited 11.14% in vitro and 30.5% tumourspheroid growth of NTERA-2 cells. In conclusion, LV3 showed its efficiency in specific CSC target labelling and inhibition, which could be further applied to fundamental and preclinical research.

59-63

Authors: Hang Thi Nguyet Pham*, Hong Nguyen Tran, Xoan Thi Le, Khoi Minh Nguyen, Hiep Tuan Nguyen, Lap Thi Nguyen, Folk R. William

Centella asiatica (L.) Urb. is a nootropic that has been used medicinally for centuries. The present study investigates the anti-dementia effect of an n-butanol extract of Centella asiatica in a mouse model of neurodegeneration caused by trimethyltin (TMT). Mice were administered Centella asiatica extract (150 and 540 mg/kg) or a reference drug, tacrine (2.1 mg/kg), daily for one week before TMT injection and during tests to analyse spatial short-term and spatial working memory. The treatment of mice with TMT caused deficits in short-term spatial working memory and decreased the number of pyramidal cells in the hippocampal CA1 and CA3 regions elucidated by Nissl staining at 28 d post-TMT treatment. The administration of Centella asiatica extract or tacrine significantly attenuated the behavioural and histochemical changes caused by TMT. These results suggest that Centella asiatica extract improved memory deficits partly by protecting hippocampal neurons from TMT-induced damage

71-76

Authors: Hong Ha Bui, Lan Huong Nguyen*, Thanh Tri Nguyen, Phuoc Dan Nguyen

In this study, a co-digestion pilot scale study of a mixture of domestic wastewater and the organic fraction of food waste using an anaerobic membrane bioreactor was developed. The results show that the removal efficiencies of the chemical oxygen demand (COD) and total suspended solids (TSS) were high and reached more than 90%. However, the removal of nitrogen and phosphate was not remarkable. The daily biogas yield reached 2.12 m3/d. The obtained biogas per COD removed was 0.22 m3/kgCODremoved. The average generated methane yield was 1.33 m3/d, which is equivalent to 0.14 m3/kgCODremoved. A high efficiency of organic compound removal combined with a large amount of retained nutrients and high biogas yield suggests the results of this pilot scale study can be practically applied to the recovery of nutrients for agricultural use along with biogas for cooking. These benefits remarkably reduce environmental pollution, especially for decentralized residential areas and independent-stationed military units located far from concentrated wastewater treatment plants.

83-89

Authors: Nguyen Thanh Tung, Wilai Chiemchaisri, Chart Chiemchaisri*, Samunya Sanguanpak

A biofilter using organic (compost) and inorganic (pumice, porous silica pellet or poremat) media was applied to the removal of methane (CH4) and nitrous oxide (N2O) to minimize the impact of off-gasses from municipal solid waste disposal global. The objective was to determine the appropriate biofilter media for CH4 oxidation and N2O conversion. The off gas (59.6% CH4, 1.0% N2O) was fed simultaneously with air (1:3 ratio) into the biofilter. CH4 oxidation and N2O conversion rates were observed over a 101-day period through the analysis of gas concentration along the biofilter’s depth using gas chromatography. Higher CH4 oxidation in the biofilters containing organic and inorganic media was achieved, especially for the compost-poremat biofilter with 70.1 g CH4/m3/d realised. The most active methane oxidation zone was found near the gas inlet at the bottom of the biofilter. The presence of inorganic material helped promote aerobic conditions for CH4 oxidation, especially during the initial period. N2O was also more completely removed with the biofilter containing inorganic media. Higher methanotrophic activities in matured biofilter media and the presence of methanotrophs type I, which prefer oxygen-rich conditions, were confirmed.

8-17

Authors: Thi Nhu Ngoc Nguyen*, Thi Thanh Hang Huynh, Thi Hien To

In this study, batch and continuous-flow sorption experiments were conducted to evaluate the removal of methylene blue (MB) from aqueous solutions by Carica papaya wood (CPW) biosorbents. The effects of critical factors such as initial pH, particle size of the biosorbent, biosorbent dosage, initial dye concentration, contact time, and salt ionic strength were studied in batch experiments. The equilibrium data fit well to the Langmuir isotherm model with the highest monolayer adsorption capacity of 63.29 mg/gat an initial dye concentration of 50 mg/l, pH of 10,and contact time of 60 min. Batch desorption and regeneration studies using 0.1 M HCl as the desorbing agent indicated that the removal efficiency of MB lasted up to 5 cycles. Continuous-flow biosorption experiments were investigated to determine the practical applicability of the biosorbent. The dye removal efficiency increased with an increase in absorbent dosage and decreased with an increase in flow rate. The Thomas model was found to be in good agreement with all the experimental data collected from continuous flow sorption. It was concluded that this study presented CPW as a promising biosorbent material for the removal MB from aqueous solutions.

23-29

Authors: Van-Tai Nguyen, Manh-Ha Bui, Emilie Strady, Thuy-Chung Kieu-Le, Ba-Trung Bui, Thanh-Son Dao

Plastics, plastic additives, and their emission have attracted significant attention and concern both socially and scientifically. Di-2-ethylhexyl phthalate (DEHP) and bisphenol A (BPA) are two of the many plastic additives widely found in aquatic environments, which can have severe impacts on aquatic animals like micro-crustaceans. Therefore, this study assessed the chronic effects of DEHP and BPA, both individually and jointly, at environmental concentrations (e.g. 50 and 500 μg/l) on the survival rate, reproduction, and growth of the tropical micro-crustacean Ceriodaphnia cornuta. We found that each of the two plastic additives, and a mixture of the two, had some influence on the survivorship of C. cornuta. While DEHP marginally enhanced the reproduction of the animals, BPA strongly inhibited it. Additionally, the mixture of DEHP and BPA caused a synergistic effect on reproduction but an antagonistic effect on the growth of C. cornuta. Both DEHP and BPA induced a significantly longer body of C. cornuta when exposed to these plastic additives. Our results showed that the tropical micro-crustacean C. cornuta is more sensitive to DEHP and BPA than the temperate micro-crustacean D. magna in relation to body length development and reproductive characteristics. Our findings enrich the knowledge of DEHP and BPA toxicity to tropical micro-crustaceans. Besides, our results are also of significant value to freshwater monitoring and environmental risk assessments of plastic additives.

36-42

Authors: Thi Hong Diep Nguyen*, Trong Can Nguyen, Thi Ngoc Tran Nguyen, Thien Nhi Doan

An Giang is one of the provinces in the Mekong delta that is greatly affected by flood events, which brings damage and devastation to life and property. This study practices the application of Sentinel-1A images to monitor the distribution of flood depths in the An Giang province in 2019 as well as applies regression correlation and thresholding to scattering value analysis. The research results indicated the exponential regression model on the VV polarization images had correlation coefficients (r) in August, September, and October ranging from 0.8398 to 0.9764 and determination coefficients (R2) ranging from 0.7896 to 0.9533. Results from the map of current flood depth showed that the flood depth ranged from 0-250 cm, which corresponded to four flood levels. The flood area increased from August to October with the largest flooded area being 89,606.82 ha (accounting for 26.15%) mainly on rice lands and in eight urban districts including An Phu, Tinh Bien, Chau Thanh, Chau Phu, Phu Tan, Tri Ton, Chau Doc, and Long Xuyen city. The limit of flood depth determined by using the Sentinel-1A images was below 145 cm. Above this value, the scattering in the image is not significantly different from the actual submerged depth.

49-59

Authors: Kim Tran Thi, Huy Nguyen Dam Quoc, Phung Nguyen Ky, Bay Nguyen Thi*

Numerical models that calculate bed change are becoming increasingly popular because of their long-term forecast projections and their ability to identify causes of bed change. However, the reliability of the simulation results depends on the length of the data series and the algorithms in the model, in which the boundary condition method plays a critical role. The aim of this study is to assess the effectiveness of the HYDIST model to update wet and dry fronts as well as recalculate the wet boundaries of the hydraulic model before its input into the sediment transport model. The moving boundary theories (wet and dry fronts) of Zhao (1994) and Sleigh (1998) were applied. The velocity distribution of the wet boundaries was recalculated after every time step, then the outcomes of the hydraulic model were used as input for the sediment transport model. The results showed good agreement between the simulated and measured data in term of discharge, water level, and sediment concentration. At the same time, the HYDIST model can be successfully used to simulate sediment deposition and riverbank movement.

65-70

Authors: Diep Anh Tuan Dinh*, Thanh Loc Nguyen, Thi Ngoc Phuong Nguyen, Hieu Trung Nguyen

In the recent past, the quality of surface water for domestic use in the Vietnamese Mekong delta (VMD) has been seriously affected by severe water pollution and intense saltwater intrusion.This study aims to assess existing surface water sources in the provinces of Can Tho, Hau Giang, and Soc Trang. By assessing the existing salinity status to point out areas of low salinity frequency hazards, this work identifies suitable areas through water quality assessments. The results indicated that the Hau river and its tributaries from Ke Sach (in Soc Trang) toward inland has a lower risk of salinity. This indicated that water sources in Ke Sach could be a possible raw water source for water supply treatment plants in Soc Trang. Specifically, water sources including the Hau river’s mainstream, Cai Khe canal, Khai Luong canal, and Thom Rom canal in Can Tho city, the Hau river’s mainstream, the Mai Dam river in the Hau Giang province, and the Cai Con river, the Hau river’s mainstream in Ke Sach, and the Cai Vop and Cai Tram canals in the Soc Trang province, could be exploited for water supply. However, a treatment for pollutants such as BOD5, COD, TSS, and total coliform in these water sources musts be taken into consideration.

77-86

Authors: Nguyen Thi Thuy Trang*, Sangam Shrestha, Hiroshi Ishidaira, Pham Thi Thao Nhi

The goal of this study is to examine the responses of hydrology and water resource availability to future climate change in the 3S (Sekong, Sesan, and Srepok) river basin located in the tropical countries of Laos, Vietnam, and Cambodia. The calibrated the Soil and Water Assessment Tool (SWAT) model was used to investigate changes to the hydrological regime and water resources under various climate change scenarios. The climate change scenarios were designed based on an ensemble of 5 GCM simulations (HadGEM2-AO, CanESM2, ISPL-CM5A-LR, CNRM-CM5, and MPI-ESM-MR) for medium emission (RCP4.5) and high emission (RCP8.5) scenarios. The climate of the basin was prognosticated to be warmer and wetter with increased temperature and precipitation in the future. Future climate change causes an increase in stream flow from 29.0 to 45.0%, 2.0 to 8.3%, and 1.2 to 10.6% for the Srepok, Sekong, and Sesan rivers, respectively. Although the discharge is projected to increase in the future, the per capita water availability is projected to decrease to 48.5, 55.1, and 80.2% in the 2090s compared to 2010 for the Srepok, Sekong, and Sesan rivers, respectively, due to population growth. The Sekong and Srepok basins will experience the most serious decline in trend and absolute value of water availability, respectively. The results of this study will be helpful to water resource development, planning, and management under climate change scenarios in the 3S river basin (3SRB).

10-14

Authors: Thanh Dam Nguyen, My Linh Hoang, Hong Anh Duong, Hung Viet Pham*, Anh Tuan Do, Jean-Luc Vasel

Biochemical oxygen demand (BOD) and pH are two important parameters in environmental analysis that allow the assessment of water quality. Although the long-term determination of BOD and pH can provide more useful information about the wastewater characteristics, present commercial BOD devices do not usually meet this demand. This research has successfully developed a novel BOD/pH device based on the respirometric principle, which can simultaneously and continuously monitor both BOD and pH of wastewater for about 20 days. The performance of the proposed device is evaluated in the laboratory by comparison to that of a commercial device (BOD Trak II, HACH). This solution not only follows the variation of BOD and pH over a long period of time, but also shows low cost and high potential for a wide variety of applications in Vietnam.

19-25

Authors: Quang Hoang Hanh Le, Nguyen Ngoc Chau Tran, Thi Cam Tuyen Nguyen, Huong Giang Nguyen, Kien Trieu Lac, Thi Anh Pham, Pham Ngoc Son Chu

Agilent’s innovative EMR-Lipid and Captiva EMR-Lipid sorbents efficiently replace the traditional QuEChERS d-SPE clean-up products in selective lipid removal from fatty matrices, thus improving instrumental analytical reproducibility, reliability, and long-term use. These products have dual functionality; a hydrophobic interaction between the sorbent with long aliphatic lipid chains of the matrices, which allows for complete lipid retention, and a size exclusion property that does not retain analytes, thus this maximizes, in principle, analyte recovery in any sample. As most of the analytes under study were polar or not highly nonpolarand had a relatively large size, the examination of small-sized nonpolar or less polar compounds is necessary to check for partial retention by the sorbents and if any, further precautions should be taken when using these sorbents. These queries are answered in our present communication concerning the analytes Trifluralin (logP: 5.27), Fipronil (logP: 4.0), and Clenbuterol (logP: 2.63)

33-37

Authors: Dang Quang Vinh Nguyen, Tien Khoa Le, Thi Thanh Thuy Nguyen*

Recently, the vanadate species have been considered as promising inhibitor agents used for metal protection. Various metallic materials were treated in a vanadate solution in order to form a passivation coating. However, the use of solid vanadate compounds as inhibitor pigments in the formulation of anticorrosive primers is still limited. Therefore, in this work, solid zinc metavanadate pigments for application in paint primers were prepared by a simple route at various pH values and concentrations of monovanadate. According to the results, all samples showed a characteristic hexagonal structure with high anticorrosive abilities. Both the pH and monovanadate concentration strongly affected the morphology, the particle size, and the anti-corrosion power. Among the prepared samples, the best anticorrosive pigment was the sample prepared at pH 8 with a vanadate concentration of 0.2 M.

45-48

Authors: Tran Hung Tra*, Huynh Minh Tu

The influence of welding speed on the properties of friction stir welded aluminium alloy 5083 was explored. The effects of various welding regimes on the defect formation, hardness distribution, tensile strength, and bending strength of the joint were experimentally investigated. Kissing bond defects were prevalent in the joint, however, this kissing bond was eliminated at high welding rates. The welded zone was softened significantly; all the tensile specimens were fractured in the welding zone with shear mode. The tensile strength of the joint reached 85% of the base aluminium alloy 5083 while the bending ductility of the joint was higher than that of base aluminium alloy 5083.

56-61

Authors: Le Anh Tuan*

Water is the most important component of agriculture production, especially during the dry seasons when all water sources are scarce yet water needs are very high. The Mekong river delta in Vietnam is the largest agricultural and aquacultural region in the country where about half of the Delta’s land area is used for rice and upland crop cultivation. One key strategy to address the regional water utility problem is to estimate the net water requirement during the dry seasons. The needs for irrigation water discharge for rice and other upland crops during the dry seasons of the Delta were quantified using the Penman-Monteith equation for estimating reference crop evapotranspiration along with the CROPWAT model for calculating crop irrigation water requirements. In general, the total water taken from the Mekong river flow for irrigation requirements should be approximately 2,300-2,600 m3/s for normal yields in the current agriculture areas and under local cultivation conditions. Water diversion and upstream hydropower projects are challenging tasks, especially in the context of climate change, to satisfy the water needs for agricultural irrigation in the near future. All water stakeholders among the neighbouring countries that rely on the Mekong river must adjust their regional water-use planning as one of the mitigation solutions for the seasonal drought crisis.

68-69

Authors: Vu Tien Chinh*, Nguyen Quoc Binh, Tran Van Hai

A newly recorded species, Mycetia hirta Hutch. (Rubiaceae) was reported from Muong Phang district, Dien Bien province in northern Vietnam. It is distinguished from the closely related species, M. longifolia, by its hairy stem and leaf blades, much shorter corolla tube and hirtellous calyx and corolla. Morphological description and color photographs of M. hirta Hutch. are provided

76-82

Authors: Duan Dong Ta, Linh Dam Thi Mai, Hai The Pham*

In previous studies, a microbial fuel cell (MFC) was developed as a potential sensor that detects iron in water. However, to realize such an application in practice, the electrical signal generation of the MFC must be improved. Therefore, in this study, we investigated several measures to optimize the electrical signals of the MFC including (i) changing the anode spacing, (ii) testing different oxygen supply rates, (iii) testing different external resistances, and (iv) testing a new electrode material. An anode spacing of 2 cm was found to be optimal as the MFC generated a current that was at least 2-fold higher than any other anode spacing investigated. To limit oxygen diffusion from the cathode to the anode, an optimal cathode air flow rate of 1.8 ml min-1 was found, which corresponds to an oxygen supply rate of 0.286 mg min-1. By a polarization experiment, a 60-Ωexternal resistance ensured the most stable MFC-generated current , which is compulsory for the use of the device as a biosensor. Finally, activated carbon was shown to be an excellent material to improve electrical signal generation by 2-fold in comparison with graphite felt and graphite granules. These reported results will be the basis of further development of the MFC toward a practical biosensor

90-96

Authors: Van Doanh Vu*, Hong Tinh Pham, Thi Thu Trang Bui

Climate change and sea level rise (SLR) have greatly affected the coastal land use of the Nam Dinh province. It has especially impacted the mangrove forests in coastal plain areas. According to the monitoring data from management units, saline intrusion due to SLR tends to expand in scope, affecting and reducing the area of mangrove ecosystems. From this situation, it can be seen that the impact assessment and estimation of economic loss in coastal provinces such as Nam Dinh is incredibly necessary to help the localities proactively respond to climate change and SLR, which is in line with the national target program on climate change. This research, which uses methods of evaluating economic values, aims to quantitatively assess the extent of damage caused by SLR on an area of mangrove forests in Giao Thuy district, Nam Dinh province. The valuation of these impacts will provide a basis for scientists, research institutions, and localities to proactively mitigate and adapt to climate change. Research results show the damage of climate change and SLR to the coastal mangrove forests in Giao Thuy and the risk to agricultural land use in the Nghia Hung and Hai Hau districts. These results also provide warning of the potential damage caused by SLR to dike and irrigation systems in the coastal districts of the Nam Dinh province, which follow Xuan Truong, Giao Thuy, Hai Hau, and Nghia Hung.

7-11

Authors: Jean-Luc Vasel*, Hung Viet Pham

When the design or operation of wastewater treatment plans is considered, it is important to measure the polluting loads to be treated. These loads are calculated as the product of a daily volume of liquid waste and the average concentration of the pollutant. Of course, to do this, the sample must correctly represent the liquid effluent. Extensive analytical equipment can be used to characterize the numerous compounds contained within wastewaters with high accuracy but cheap, simple, and even sometimes mobile equipment are mostly used for the daily operations of treatment plans. In this regard, we present the use of a pH-respirometer, based on manometric methods, to characterize wastewaters that will be treated by aerobic biological systems. Another type of biological treatment system is based on anaerobic processes when the effluents have a high content of biodegradable organic compounds. Anaerobic digestion is very attractive as it is possible to produce a valuable gas (biogas) out of the waste instead of consuming energy and oxygen to realize an aerobic treatment. In this paper, we will present the meaning of biochemical methane potential (BMP) curves and compare those curves to respirometric curves such as biological oxygen demand (BOD) tests.

19-23

Authors: Lan Huong Nguyen, Hong Ha Bui*, Xuan Truong Nguyen

In this study, a continuous ammonium stripping lab-scale model of anaerobic co-digestion effluent from an organic fraction of food waste and domestic wastewater was used to investigate ammonium removal efficiency by air stripping. The effect of initial pH, liquid flow rate, and air-to-liquid ratio on the removal of ammonium from the effluent were examined in experiments. The operating parameters of the trials were established based on calculations from influent and effluent ammonia concentration and the theory of mass transfer. The results indicated that a pH value of 11, liquid flow of 0.25 l/min, and a ratio of air-to-liquid of 2925 gave a >90% ammonia removal efficiency and thus reached the allowable ammonia levels of wastewater discharged into receiving sources. The continuous stripping of nitrogen from anaerobic co-digestion of effluent had a huge significance in the removal of ammonium and recovery of ammonia gas , which aids in eutrophication prevention and fertilizer production.

30-33

Authors: Ngoc Thuc Dinh*, The Minh Do, Xuan Luong Ngo, Huan Trinh Thi, Huong Nguyen Thi, Ha Mai Vu Thi, Ngoc Mai Nguyen Thi, Thi Kim Oanh Vu

Rourea harmandiana Pierre is a species which belongs to the family of Connaraceae. This plant is found abundantly in central of Vietnam (Thua Thien - Hue, Da Nang). Chemical study on the ethyl acetate extract of Rourea harmandiana leaves has led to the isolation of four compounds including vomifoliol (1), boscialin (2), abscisic acid (3) and p-coumaric acid (4). The structures of these compounds have been identified by NMR, MS spectroscopic data and comparison with the reported literature. These compounds were isolated from Rourea harmandiana species as well as from the genus Rourea for the first time.

38-40

Authors: Hung Quang Pham, Thuy Thu Truong, Duc-Anh Song Nguyen, Le-Thu Thi Nguyen*

Polymers containing hydrogen bonds are of great significance as they have the potential to strengthen the mechanical properties of a material through non-covalent crosslinking, which is the basis for paint and self-healing materials. In this work we describe a method to obtain a novel polymer via the coupling reaction of cyanuric chloride and a di-amine. We investigate the reaction conditions to optimise the polymerization yield and molecular weight polydispersity. The polymerization process was characterised by gel permeation chromatography (GPC), nuclear magnetic resonance spectroscopy (NMR), and attenuated total reflection Fourier-transform infrared (ATR FT-IR) spectrometry.

48-55

Authors: Pham Quynh Nhu, Tran Thanh Uyen, Phan Minh Vuong, Phan Thanh Thao*

Yeast biomass enriched with iron is used in a profound and safe treatment for anaemia. In this work, response surface methodology (RSM) was used to survey the response of culture conditions (temperature, degrees brix, time, and initial iron concentration) to the bioaccumulation of ferric ion (Fe3+) in yeast (Saccharomyces pastorianus). On the other hand, the Box-Behnken design was used to determine the optimum conditions of 24oC, 13oBx of the culture solid content for 49 h incubation and 656 ppm of initial iron concentration. The total Fe3+ content in the biomass was significantly affected by the culture temperature and degrees brix (p<0.0001). Under optimum conditions, the maximum level of Fe (III) ions in the dry cell weight of S. pastorianus was 16.82±0.65 mg/g. The results from statistical analysis showed that the model was significant (p<0.0001) and adequate.

65-70

Authors: Quang Chon Nguyen*, Van Cuong Dinh, Minh Ngoc Truong

Variable charge soils (VCS) predominantly contain minerals with variable surface charge density, such as kaolinite, gibbsite, goethite, hematite and amorphous minerals. The charge characteristics differ between profile horizons, the topsoil normally possesses net negative surface charge whereas the subsoil may have net positive surface charge and are largely dependent on soil pH. The soils pose a particular challenge to sustainable management in terms of low cation exchange capacity (CEC) at soil low pH and may develop appreciable anion exchange capacity (AEC) under acidic conditions. A full understanding of the variation of charge with soil pH, before establishing strategies for sustainable management of these soils, is essential. This study has found that the VCS from the Central Highlands are extremely acidic (pH<4.5) and very low in CEC (<1.0 cmolc kg-1), these problems are more pronounced in the subsoil with exhibiting higher pH0 (4.63) than the existing soil pH (4.26) and higher point of zero net charge (PZNC) (4.88) than point of zero charge (pH0), and developing net positive surface charge (-0.62 cmolc kg-1). These properties are attributed to low total organic carbon (TOC) and Fe/Al hydrous oxides in the clay fraction that significantly affect pH buffering capacity and delta CEC. In addition, organic matter (OM) has a great influence on the pH0 of variable charge components, and thus on CEC.

77-82

Authors: Xoan Thi Le*, Xuyen Thi Phi, Duong Thi Thuy Nguyen, Hang Thi Nguyet Pham, Tai Nguyen Van, Olapoju Samuel O., Kinzo Matsumoto

This study investigated the angiotensin 1-converting enzyme (ACE) inhibitory activity of certain medicinal plants that have been traditionally used as an anti-hypertensive, diuretic, or related diseases treatment in Vietnam. Ten different medicinal plants were selected and screened for in vitro ACE inhibitory activity. A spectrophotometric assay was developed for the determination of ACE activity in the presence of ACE inhibitors using hippuryl-L-histidyl-L-leucine as the ACE-specific substrate. When the in vitro activities of ACE were assessed in the presence and absence of aqueous or ethanol extracts from each medicinal plant, 2 out of the 22 medicinal plant extracts inhibited the ACE activity by more than 90% at a concentration of 50 μg/ml. The estimated IC50 value of the L. rubraand U. sessilifructus were 1.31±0.44 and 12.86 μg/ml, respectively. These results suggest that the L. rubrarhizome and U. sessilifructus extract are potential anti-hypertensive drug-like candidates with ACE inhibitory activity.

89-96

Authors: Nguyen Phuoc Dan, Le Thi Minh Tam*, Vu Le Quyen, Do Hong Lan Chi

An experimental study to use a pilot vegetated submerged bed (VSB) wetland for the advanced treatment of effluent from the central wastewater treatment plant (CWWTP) of an industrial zone was carried out. The pilot VSB wetland included reeds (Phragmites australis), cattail (Typha orientalis), and blank cells in parallel. The constructed wetland was observed to be a suitable measure for wastewater reuse via the high performance of organic matter, turbidity removal, and detoxification. At loading rates of up to 250kg chemical oxygen demand (COD) ha-1d-1, both cells with emergent plants obtained high efficiency of contaminant removal. Suspended solids (SS) and turbidity removal reached 67-86% and 69-82%, respectively. The COD removal efficiencies of the reed and cattail cells at a loading rate of 130 kg COD ha-1d-1were 47 and 55%, respectively. At a high loading of 400 kg COD ha-1d-1, the toxicity unit (TU) reduced from 32-42 to 4.9 and 4.2 in the effluent of the cattail and reed cells, respectively. Especially at loadings of 70, 130, and 185kg COD ha-1d-1, the effluent TU was less than 3.0, corresponding to a non-toxic level to the ecosystem. The effluent quality met industrial or landscaped wastewater reuse at these loading rates