Published: 2017-07-31

Effects of nitrogen fertilizer types and alternate wetting and drying irrigation on rice yield and nitrous oxide emission in rice cultivation

Vo Thanh Phong, Nguyen Thi Anh Dao, Nguyen My Hoa
Abstract | PDF
Improvements on nitrogen (N) efficiency in rice cultivation have been increasingly concerned till now with using new types of N fertilizer. Aims of the study were to investigate the effect of N fertilizer types and alternate wetting and drying irrigation on rice yield and N2O emission in rice cultivation in the Mekong Delta of Vietnam. The design of experiment was split plot with two water management regimes in main plots which were (1) alternate wetting and drying (AWD) and (2) farmer practice (FP); and four N fertilizer types in sub-plots were (1) urea (2) N-(n-Butyl) Thiophosphoric Triamide (nBTPT) urease inhibitor, (3) NPK briquette deep placement technique and (4) Isobutylidene Diurea (IBDU) slow N-release. N2O emission was investigated every three days from 10 to 60 days after sowing (DAS). The results showed that AWD treatment had higher rice yields (5.14 t.ha-1) than FP treatment (4.68 t.ha-1), but rice yields of the new fertilizer type treatments were not significantly different compared with that of urea treatment. Concentrations of N2O increased after broadcasting fertilizer in treatments of urea and urea-nBTPT and then decreased thereafter in both FP and AWD irrigations. In treatments of NPK briquette and NPK IBDU, N2O fluxes remained low throughout crop although the fluxes increased in times  of soil drainage under AWD regime. Cumulative N2O emissions of urea-nBTPT, NPK briquette or NPK IBDU treatments (1.67, 1.47 or 1.29 kgN2O.ha-1, respectively) were significantly lower than that of urea treatment (2.47 kgN2O.ha-1). The results suggested that application of urea-nBTPT, NPK briquette and NPK IBDU were effective in mitigating N2O emission in rice fields which contributes to attenuate the greenhouse effect.

Disease-reducing effects of antagonistic soil bacteria on Fusarium basal rot of shallot caused by Fusarium oxysporum in Vĩnh Châu, Sóc Trăng

Nguyen Dac Khoa, Tran Viet Quyen, Chau Hoang Trung Tin
Abstract | PDF
Fusarium basal rot caused by Fusarium oxysporum is one of the most important diseases of shallot (Allium cepa var. ascalonicum). This study aims at isolating soil bacteria from Vinh Chau (Soc Trang) and testing for their antagonistic and disease-reducing effects which could be used for biological control of the disease. A number of 224 isolates were collected and tested for their antagonistic effects on mycelial growth and conidia germination of the pathogen. Among those, three isolates exhibited the strongest effects. These isolates were tested for their disease-reducing effects under greenhouse conditions using two application methods, i.e., bulb coating and soil drenching. Two treatments using ATB-24 and ATA-33 (108 CFU/mL) showed the highest effects on disease incidence and severity; their effects remained through all assessment time points (until 65 days after planting). The results suggest the applicability of the ATB-24 and ATA-33 isolates as biological control agents for Fusarium basal rot of shallot.

Disease-reducing effects of aqueous leaf extracts of annona glabra and wedelia calendulacea on fusarium basal rot of shallot caused by fusarium oxysporum

Nguyen Dac Khoa, Nguyen Van Vinh, Lam Tan Hao
Abstract | PDF
Fusarium basal rot (Fusarium oxysporum) of shallot is a destructive disease, which constrains the production and quality of this crop in Vinh Chau (Soc Trang, Vietnam). This study aims at screening wild plants with antimicrobial activities to bio-control the disease. Among aqueous extracts of 49 commonly found plant species in Vietnam, the 4% (w/v) leaf extracts of Annona glabra and Wedelia calendulacea exhibited strongest inhibitory effects on the mycelial growth of F. oxysporum (up to 35.3% and 25.7%, respectively) in disc diffusion assays. Furthermore, incubating the conidia in A. glabra extract (4%) resulted in a significant suppression in germination (up to 95.3%). Under net house conditions, soil drenching of both extracts at 4% and 5% concentrations showed an equivalent reducing effects on both disease incidence and severity in shallot plants compared to the chemical treatment. Thus, A. glabra and W. calendulacea show their potentials for large-scale applications to sustainably control Fusarium basal rot of shallot.

Metformin - An agent stimulating motility and acrosome reaction in chicken sperm

Nguyen Thi Mong Diep
Abstract | PDF
Sperm are germinal cells whose main functions, motility and acrosome reaction, promote its essential role: the oocyte fertilization. Currently, many chemicals are added to the media to enhance sperm quality during artificial insemination. Metformin, which is commonly used for the treatment of type II diabetes, possesses properties impacting cell metabolism control that have not been assessed yet in sperm. The aims of this experiment were to: (a) determine the effects of Metformin on fresh chicken sperm motility and ability to perform acrosome reaction: (b) evaluate its effects on the functions of cryopreserved sperm. These experiments have shown that the presence of Metformin in fresh semen has a positive impact on the quality of sperm and help reducing the gradual decline in sperm motility caused by cryopreservation. 

Molecular characterization of infectious bronchitis virus (IBV) isolated from commercial chicken farms

Tran Ngoc Bich, Nguyen Thi Cam Loan, Pham Hoang Dung, Nguyen Phuc Khanh
Abstract | PDF
Infectious bronchitis virus (IBV) primarily causes a highly infectious bronchitis (IB) in commercial chickens. Virus isolation and identification is necessary for diagnosis of the disease. In this study, a total of 5 IBV isolates that isolated from commercial poultry farms were isolated by inoculation in 9 day-old embryonated SPF eggs. After few passages, the embryos showed typical lesions of IB such as stunted and curled cross with feather dystrophy. Then, the 5 IBV isolates were characterized by RT-PCR followed by DNA sequencing of partial S1 gene. The phylogenetic analysis shows that the 5 IBV isolates distinctly clustered into 3 groups. Group 1 including IBV1/15, IBV2/15 and IBV3/15 shared more than 99% similarity with IBV genotype 793/B. Group 2 consisting of isolate IBV4/15 was closely related to genotype QX-like with the similarity of 98%.Interestingly, group 3consisting of IBV5/15 had genetic distance ranged from 8% to 10% with other reported IBV genotypes such as 793/B, Massachusetts-type, Taiwan-type and QX-like viruses whilstIBV5/15 shared about 99% similarities with a nephropathogenic Malaysian IBV isolate.

A navigation and identificationsimulated chemicals using autonomous mobile robot with ceiling camera and onboard micro-spectrometer

Luu Trong Hieu, Tran Thanh Hung
Abstract | PDF
This paper proposes a method for controlling a mobile robot using decentralized control based on signal from ceiling camera to remotely recognize simulated chemicals by color sensing. This camera recognizes a robot tag, which put on the robot, to specify the coordinate of the target and sends back to master computer. Based on this signal, the master computer controls the robot to the central of the coordinate where a chemical is put. Whenever moving to the expected position, the robot will open the gripper and grip the target. A slave computer analyzes the signal from an on-board spectrometer to recognize the target and send the result to the master one’s. Experiment results are proved to the applying ability of mobile robots to identify unknown targets.

Engineering properties of unfired building bricks incorporating various industrial wastes

Huynh Trong Phuoc
Abstract | PDF
This paper studies the possibility of using a mixture of class-F fly ash (FA) and residual rice husk ash (RHA) for producing unfired building bricks (UBB) with the application of densified mixture design algorithm (DMDA) method. In this investigation, little amount of cement (5–10%) was added into the mixtures as binder substitution. Especially, unground rice husk ash (URHA) was used as a partial aggregate replacement (10–20%) in the mixtures. By following Vietnamese standard (TCVN 1451:1998), solid bricks of 220×105×60 mm in size were prepared for testing hardened properties including compressive strength, flexural strength, water absorption, and bulk density. The forming pressure of 35 MPa was applied to form the brick samples in the mold. Test results reveal that all of the brick samples achieved good mechanical properties. Additionally, compressive strength, flexural strength, and water absorption of brick samples were respectively in the range of 13.8–19.7 MPa, 2.3–3.3 MPa and 9.7–14.8% while the other properties of the bricks were well-conformed to corresponding Vietnamese standards. Furthermore, it was definitely proved many potential applications of FA and RHA in the production of the UBB.

Electrospun CuO/Ag nanofibers for nonenzymatic glucose sensors

Nguyen Minh Tri, Doan Van Hong Thien, Tran Thi Bich Quyen, Vo Ngoc Han
Abstract | PDF
Nonenzymatic biosensors based on Ag/CuO nanofibers have been successfully investigated. PVP nanofibers loaded AgNO3/Cu(NO3)2 were successfully synthesized by an electrospinning method. The conditions of electrospinning included 8% PVP solution, feed rate of polymer solution of 0.5 mL/h, applied voltage of 20 kV, and the tip-to-collector distance of 8 cm. The nanofibers were carbonized at 300, 450, and 600 oC to obtain Ag/CuO nanofibers. The Ag/CuO nanofibers were characterized by SEM, TEM, and XRD analyses to confirm the morphology as well as the formation of copper oxide and silver. The Ag/CuO nanofibers were used to construct a nonenzymatic glucose sensor. The Ag/CuO NFs-IGZO electrode was applied to detect glucose by cyclic voltammetry (CV). The direct oxidation of glucose in sodium hydroxide medium at Ag/CuO nanofiber modified electrodes has been investigated. 

Factors influencing group work of students in learning English as a foreign language (EFL): A case study at a Vietnamese university

Le Thi Nhan Duyen, Nguyen Buu Huan
Abstract | PDF
Group work has been largely used as an effective teaching strategy in English as a foreign language (EFL) classroom contexts to develop students’ communicative proficiency in English. Although several studies on group work examined  EFL teaching at universities in Viet Nam and in the world,  the question as to what factors influence EFL students’ group work in classroom in the Mekong Delta remains unanswered.  This paper therefore reports on a case study at a university in the Mekong Delta of Vietnam, which explores the factors that influence EFL students’ group work in classroom contexts as well as the difficulties students encountered in group work activities. Data were collected from the questionnaire surveys and interviews. The findings showed that four factors influencing students’ group work in class include classroom context, student interactions, the role of the teacher and the tasks. Of the four factors, student interaction was ranked the most important factor. Moreover, challenges while working in groups were reported as students’ mixed abilities, difference in viewpoints, use of Vietnamese during discussion, time limitation and topic difficulty levels. 

Factors inhibiting teachers from research engagement: A review

Luu Bich Ngoc, Phuong Hoang Yen, Ly Thi Bich Phuong, Vo Phuong Quyen
Abstract | PDF
Teachers’ research capacity has long been considered an important component that contributes to their own professional development as well as teaching practice. Specifically, teaching effectiveness will be improved significantly when teaching is integrated with research activities (Healey, 2005). However, various factors have prevented teachers from involving in as well as conducting research activities. Basing on existing literature, the current study reviews five common factors that prevent language teachers from research engagement. These factors include non-collaborative school culture; limitations in teachers’ awareness, beliefs, skills and knowledge; limited resources; demotivators and economic factors. 

A Phenomenological study of challenges encountered by mountainous high school students in Vietnam

Le Thi Hong Cam, Phuong Hoang Yen
Abstract | PDF
English writing skills have received considerable attention from Vietnamese Ministry of Education and Training with their decision of involving the skills in the national examination for General Certificate of Secondary Education (GCSE) for the past two years. However, many high school students in mountainous areas in Vietnam are encountering challenges of writing in English, which results in their low marks in writing tests, or even their avoidance of writing assignments. With such phenomenon, this paper aims at investigating challenges that high school students in mountainous areas encounter in English writing. This is a descriptive survey with a 5-point Likert scale questionnaire. To collect research data, the sample of the study includes five hundred twenty Grade 12 students from three high schools in mountainous areas, Vietnam. The results of the study revealed that high school students in mountainous areas encountered many challenges related to English writing. It is obviously proved that poor spelling, inadequate mastery of grammatical structures, the first language interference, lack of vocabulary, and poor understanding of a well- organized presentation are the most common challenges. The study will be the first step to assist high school teachers to achieve in-depth understanding of students’ challenges in English writing as well as to prepare for the textbook changes in Vietnam in 2018.

Effects of photoperiods on growth and quality of white leg shrimp (Litopenaeus van-namei) in biofloc system

Tran Ngoc Hai, Le Quoc Viet, Tran Minh Phu, Truong Van Ngan
Abstract | PDF
This study aims to determine suitable photoperiod for growth of white leg shrimp in supper-intensive tank culture system applying biofloc technology. The experiment was randomly designed indoor with different photoperiod treatments, including (i) 24 hours Dark; (ii) 6 hours Light: 18 hours Dark; (iii) 12 hours Light: 12 hours Dark; (iv) 18 hours Light: 6 hours Dark and  (v) 24 hours Light. The lighting treatments, it was set with a 55w compact fluorescent (light intensity ~ 6000 lux). Shrimp with initial weight at 0.84g and 4.45cm of body length were cultured at density of 150 inds/m3 in Biofloc system (C:N=15:1), with 300L of water volume, 15‰ of salinity. Results showed that after 90 days of culture, water quality were in suitable range for shrimp growth. Body weight (BW) of shrimp among treatments were from 18.28 to 22.96 g. In which, BW of shrimp in completely dark condition was the lowest and significantly different compared to the others (p3), not significantly different compared to 18 hours Light (2,23kg/m3 ) but significantly different compared to the others. Besides, shrimp in the treatments with Light showed stronger color compared to shrimp in completetly dark condition.

Effect of germination on antioxidant capacity and nutritional quality of soybean seeds (Glycinemax (L.) Merr.)

Ha Thanh Toan, Duong Thi Phuong Lien, Phan Thi Bich Tram
Abstract | PDF
The purpose of the current study was to investigate the effects of germination for 0, 12, 24, 36, 42, 48, 60 and 72 hours on nutritional and antioxidative characteristics of germinated soybean seeds (Glycine Max L. Merr.). After germination at 25oC in dark condition, germinated seeds were freeze dried and used for determination the nutritional as well as antinutritional components such as protein, SDS-PAGE protein patterns, fat, phytic acid (PA) and trypsin inhibitor (TI). In addition, the antioxidant capacity of germinated soybean seeds, namely total phenolic content (TPC), total flavonoid content (TFC), vitamin C, α–tocopherol and DPPH radical scavenging activity in terms of IC50 were detected. Results indicated that germination caused significant (P≤ 0.05) increases in protein content. The SDS-PAGE patterns showed the proteins in the samples during 60 hours of germination were unchanged. However, oil content, antinutritional factors (PA and TI) significantly (P≤ 0.05) decreased. It was found that TPC, TFC, vitamin C and α–tocopherol increased during germination and tended to reach the maximum values when  germinated for 60 hours. Germinated seeds had lower IC50 or higher antioxidant capacity. So the present study revealed that germination significantly affects the nutritional and antioxidant properties of soybeans.

Effect of controlled atmosphere and storage temperature on the weight loss and cap colour of fresh mushrooms (Agaricus bisporus)

Phan Thi Thanh Que, Bert Verlinden, Bart Nicolaï
Abstract | PDF
The effects of O2, CO2 concentrations and storage temperature on the quality of fresh mushrooms (Agaricus bisporus) were investigated. Eight different gaseous atmospheres were used in the combinations of 3, 12, 16.5 and 21% of O2 and 0, 3, 6 and 12% of CO2. The storage temperatures for each gas condition were 1°C, 6°C and 12°C. Measurements extended over a storage period of 9 days. After storage under controlled atmosphere, the influence of O2, CO2 and temperature on the weight loss and cap colour was analysed. The results showed that the weight loss of fresh mushrooms in all gas combinations increased with an increase in temperature and storage period. A model for colour loss following an exponential law described the effect of temperature and gas composition on the quality of mushrooms. Oxygen concentration has a less pronounced effect on the cap colour of mushroom as compared to CO2 concentration and temperature.  In order to maintain an extended lifetime of colour under controlled atmosphere, mushrooms should be stored at < 6°C. At higher temperatures, CO2 concentration must be maintained at the highest level as compared with the control.

Optimization of carriers (maltodextrin, arabic gum) for spray-drying of Pouzolzia zeylanica extracts using response surface methodology

Nguyen Duy Tan, Nguyen Minh Thuy
Abstract | PDF
Pouzolzia zeylanica is a medicinal source that the people of Asia countries have used to treat various kinds of diseases by traditional method. Many research showed that Pouzolzia zeylanica extract contains many bioactive compounds with antioxidant, antimicrobial and antifungal properties. In spray drying process, the carrier was significant effect on physico-chemical characteristics. The Response Surface Methodology (RSM) with central composite design (CCD) was applied to optimize maltodextrin (5÷15%) and arabic gum percent (0.06÷1.0%) during spray drying of Pouzolzia zeylanica extract. The physico-chemical characteristics of spray dried powder (bioactive compounds, moisture content as well as particle size distribution) were analyzed.The results showed that the optimum concentrations of maltodextrin and arabic gum were 8.743% and 0.083%, respectively. At these optimal conditions, the anthocyanin, flavonoid, polyphenol, tannin, moisture content and particle size of obtained spray dried powder were 7.411 mg CE/100g; 30.931 mg QE/g; 27.296 mg GAE/g; 24.654 mg TAE/g, 6.540% va 6.029 mm, respectively. 

Improving of bread quality from frozen dough using ascorbic acid and α-amylase

Nguyen Thi Thu Thuy, Nguyen Nhat Minh Phuong
Abstract | PDF
To improve the capability and convenience of dough’s usage in bread making, this report investigated the effects of thawing-frozen processing, dough improver (e.g. ascorbic acid) and α-amylase on bread quality. The results indicated that the quality of bread was less changed in comparison with the control if frozen doughs were defrosted in room temperature for 30 minutes before fermentation at the conditions of 40oC, 2 h and baking at 180-200oC during 22 min. The addition of ascorbic acid of 0.01%, α-amylase of 0.01% or combining 0.01% ascorbic acid and 0.01% α-amylase (based on flour weight) into doughs significantly improved dough strength and loaf volume.   

Characterization of lactic acid bacteria isolated from pickled vegetables as potential starters for yogurt preparation

Nguyen Van Thanh, Nguyen Minh Thuy, Nguyen Xuan Cuong, Nguyen Thi My Tuyen
Abstract | PDF
The process of preliminary isolation and selection of lactic acid bacteria from Vietnamese traditional fermented vegetables is done on the basis of (i) isolation and (ii) qualitative and quantitative analysis of lactic acid as the basis for the inspection and selection of lactic acid bacteria with strong antibacterial characteristics. The selected lactic acid bacteria were applied for yoghurt fermentation with different bacterial densities (104-108 CFU/ml). The changes in pH value during fermentation time and sensory quality of product were evaluated. The research results showed that 48 strains were isolated from Vietnamese traditional fermented vegetables. Among them, 35 isolates (33 rod-shaped and 2 spherical-shaped) met the criteria of lactic acid bacteria. There were 15 isolates that were able to produce the highest amount of lactic acid, in which the rod-shaped bacteria has higher lactic acid production than that of the spherical-shaped. Four strains (S 1.2, S 5.5, S 5.7, XK 1.4)  of these 15 strains that were tested antimicrobial activity based on the agar spot test and agar well diffusion test, could produce bacteriocin against Bacillus subtilis. Based on the result of DNA sequencing method, strains XK 1.4 and S 1.2 with strong antibacterial production belonged to Lactobacillus plantarum (similarities 97% and 99%). The yoghurt that was prepared by inoculating 108 cfu/mL of starter cultures (strains XK 1.4 and S 1.2) had the pH value of 4.5 after incubating for 7 hrs, and achieved the good sensory quality.

Molecular dynamics simulation of rutile - anatase heterojunction

Ca Nguyen Anh Khoa, Huynh Anh Huy
Abstract | PDF
Density Functional based Tight-Binding (DFTB) method is used to study the structural properties and electronic structure of heterojunction between anatase (100) and rutile (100) surface. The near coincidence site lattice (NCSL) theory is used to construct initial models. The interfaces have been annealed from 0K to 2250K in the linear ramp of 10 ps, followed by equilibration at the constant temperature of 2250 for 5 ps and cooled down 0K with an exponential ramp of 15 ps. Interface structures have been investigated via the partial radial distribution functions (PRDF), coordination number, bond-angle distributions and interatomic distances. We found that both structures have the slightly disorder at the interfaces and the presence of four-coordinate Ti atoms, band offsets are 0.45 eV in the conduction band (CB) and 0.51 eV in the valence band (VB) with rutile is higher than anatase. Electrons migrate  from rutile to anatase, while holes migrate in the opposite direction.

Chemical examination on the ethyl acetate extract of the bark of Oroxylum indicum (L.) Vent

Ton Nu Lien Huong, Minh Trieu Lam, Giang-Tien Vo Nguyen
Abstract | PDF
This paper presents new resulst of the study about the bark of Oroxylum indicum (L.) Vent, collecting in An Giang provine, Vietnam. Three compounds as oroxylin A 7-O-β-D-glucopyranoside (1), baicalein 7-O-β-D-glucopyranoside (2) and verbascoside (3) were isolated from the ethyl acetate extract. The structures of these compounds have been elucidated by modern spectroscopic methods: NMR and MS.

Trends and determinants of compulsory land recovery on households’ income in industrialized and urbanized areas: A case study of My Phuoc town - Ben Cat district - Binh Duong province

Thai Thanh Phong, Ha Thuc Vien
Abstract | PDF
The main purpose of this article is to examine trends and determinants of compulsory land recovery on households’ income in Binh Duong Province through a case study of My Phuoc industrial zone development project. More precisely, it aims at investigating what impacts of compulsory land recovery have on farm households’ livelihoods and how new livelihood strategies adapted and what factors determine on making their income both ante- and ex- land recovery periods of time. The qualitative and quantitative analysis methods were applied in this study. Research findings figure out households’ livelihoods have been drastically transformed due to compulsory land recovery towards diversifying their income and shifting into non-farm activities. This livelihood adjustment was strongly determined by both ante- and ex - land recovered farm households’ livelihood assets. More importantly, research findings insist that ex-land recovered farm households’ income has been improved, but unstable and highly vulnerable to external conditions. Determinants of ante- and ex-land recovered farm households’ income were significantly different. It comes to conclude firmly that farm households’ livelihood transformation due to compulsory land recovery for the industrialization and urbanization process is both adaptive and coping strategies.

Determinants of income diversification and its effects on rural household income in Vietnam

Ho Thi Ngoc Diep, Ha Thuc Vien
Abstract | PDF
  ABSTRACT This article aims at examining determinants of income diversification among rural households in Vietnam and the impacts of diversification on household income. The Poisson and Tobit regression methods are applied. The data for this empirical study is detached from Vietnam Household Living Standard Surveys (VHLSS) conducted from 2002 to 2010. The regression results show socio-economic factors have strong influence on household income diversification and in turn, income diversification has positive impact on household income growth. It implies that income diversification is an important strategy to improve household livelihoods while access to and resource availability determine household income diversification.  Keywords: Determinants, impacts, income diversification, Possion, Tobit, Vietnam.