Published: 2017-11-29

The genetic diversity and the antibacterial activity of Ageratum conyzoides Linn

Huynh Kim Dieu, Nguyen Thi Han Ni
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fourteen samples of Ageratum conyzodes

Selection of thermotolerant lactic acid bacteria producing high antibacterial activity and production of biomass from tofu sour liquid

Huynh Xuan Phong, Huynh Nguyen Nhu Thu, Bui Hoang Dang Long, Takeshi Zendo, Kenji Sonomoto, Ngo Thi Phuong Dung
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The objectives of this study were to select a number of thermotolerant lactic acid bacteria for their application in biomass production at high temperature and to study the genetic relation of these selected strains by using 16S ribosomal DNA sequences. All 16 tested strains of thermotolerant LAB were found to possess the antibacterial ability and the capability of bacteriocin production against Bacillus subtilis. As a result, all 16 LAB strains had an antibacterial ability and produced bacteriocin against indicator. Ten selected strains having the strongest antibacterial ability were identified as Lactobacillus plantarum, L. casei, and L. delbrueckii. The L. plantarum L54 was selected for the experiment of the optimum conditions for biomass production because of its strongest antibacterial ability with the diameter of inhibitory zone in “agar spot test” and “well-diffusion agar” were 13.76 mm and 17.33 mm, respectively. Based on statistical analysis, the optimum conditions for biomass production by L. plantarum L54 at 39°C were 5.99% (w/v) of glucose concentration, 6.37% (v/v) of bacterial inoculum concentration, and pH 6.0.

Managerial human resource quality of firms in the Mekong Delta, Vietnam

Nguyen Pham Thanh Nam, Le Khuong Ninh
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This paper aims to provide an in-depth examination of the managerial human resource quality of firms in the Mekong River Delta (MRD) using a primary data set directly collected from 450 firms, in addition to a secondary data set provided by relevant organizations. Based on the findings, the paper proposes solutions to develop firms in the region by improving the quality of their managerial human resources.

Design a model of glass cleaning device

Nguyen Van Khanh, Nguyen Chi Ngon, Nguyen Huynh Anh Duy
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Design and create a supportive automatic device for labors working on cleaning vertical glasses on the skyscrapers has been one of the concerned topic in the issue of occupational safety recently. This study will recover briefly the main points of designing mechanical structure with a new idea after referring the previous works in glass cleaning robot. The trapezoidal velocity profile (TVP) method is mentioned in order to control the velocity of the device; and the movement strategy for cleaning glass is considered carefully while manufacturing the model of the device. The experiment has been conducted on a dirty glass with the size of 1.45m x 0.85m, this proved a good initial result which has met the expected requirement for a low-power device.

Isolation and identification of lipid-degrading yeast from wastewater of canteens and restaurants in Ninh Kieu district, Can Tho city

Nguyen Ngoc Tan, Cao Ngoc Diep
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Abstract. High lipid (fats and oils) concentration contained in wastewater from restaurants and canteens released into environment directly, leading to be pollutant water and logging drainpipe systems. The lipid-degradation capability of lipid-degrading yeast was investigated for possible application in treatment of lipids-contaminated wastewater. Twenty-eight yeast isolates were isolated from 11 lipid-contaminated wastewater samples from many restaurants and canteens in Ninh Kieu district of Can Tho city, Vietnam. There were 15 isolates produced halo zones on Tw20 agar medium and  determined to have ability of lipid-degradation, three of which (B1, ST, Da2a isolates) were found to have the high ability of lipid-degradation by measuring development of halo zone diameter during 72 hours and identified by ITS-PCR technique and DNA sequencing. After 7 days of cultivation, the rate of the degradation of lipid contaminated in wastewater by strain B1, ST, Da2a were 74.14%, 83.03% and 80.7%, respectively. The results of DNA sequencing were compared with GenBank database of NCBI by BLAST N software. The sequences from selected isolates showed high degrees of similarity to those of the GenBank references (between 97% and 99%). Isolates of B1 and ST were 99% of similarity with Candida palmioleophila and Meyerozyma quilliermondii, respectively. Da2a isolate was 97% of similarity with Candida tropicalis.Keywords: Candida, canteens and restaurants, lipid-contanminated wastewater, lipid-degradation yeast, lipid degradion, vegetable oil

Improvement of tap water quality for domestic use by membrane process

Bui Xuan Thanh, Vo Thi Dieu Hien, Cao Ngoc Dan Thanh, Truong Minh Hong, Vo Thi Kim Quyen
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Nowadays, clean water supply demand is increasing day by day in Ho Chi Minh city (HCMC) due to the rapid increase of population. It has gained concerns about water supply management and improving tap water quality of domestic use. Moreover, the results achieved from laboratory analysis of those tap water samples did not comply with the water quality standard due to low pH, high hardness and high ammonia concentration. In order to improve the water quality, low pressure reverse osmosis membrane system was proposed to polish quality of tap water. The pollutant removal of membrane system analyzed on NO3--N, NH4+-N, total Fe, hardness and residue Cl- were 41 ± 17.6 %, 18 ± 16.9 %, 47 ± 26 %, 39 ± 6 % and 94 ± 6.9 %, respectively. The results show that the low-pressure reverse osmosis membrane could achieve effective improvement of water supply quality for domestic use and satisfy the demand of clean water in HCMC. 

Drama-based role play activities to impact on students’ speaking performance

Do Thi Ngoc Nhi, Nguyen Buu Huan
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This article investigates the impact of drama-based role play activities on three domains of speaking performance – accuracy (vocabulary and grammar), pronunciation and interactive communication of English as foreign language (EFL) students at An Giang University, Vietnam and examines students’ attitudes towards the use of role-play activities in a speaking class. The experimental study was conducted with thirty freshmen who were assigned as one control and one experimental group. This paper draws on data collected as part of a larger project including pre-and post-speaking tests and interviews. The quantitative analysis reveals that students in the treatment group made progress in their speaking performance whereas the level of speaking performance among students in the control group remained unchanged. Notably, interactive communication was significantly gained compared to accuracy and pronunciation within the intervention group. The qualitative analysis from interviews indicates that students held positive attitudes towards the implementation of drama-based role play activities. 

Leadership styles of Vietnamese higher education leaders: Transformational, transac-tional, or laissez-faire

Pham Dinh Xuan Thu, Hitendra Pillay, Amanda Mergler
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Significant reforms are currently underway in Vietnamese higher education since it is in the phase of transformation to improve the higher education system. In implementing higher education reforms, leaders play a key role. The paper reports on phase two of a multi-method research: a quantitative approach using the multifactor leadership questionnaire to investigate the Vietnamese high education leaders’ leadership styles (i.e., transformational, transactional, and laissez-faire leadership) to support the quality improvement in Vietnamese higher education. The multifactor leadership questionnaire was administered to 190 senior managers in State institutions in Mekong Delta region in Vietnam (nine of colleges and universities). The psychometrics of the multifactor leadership questionnaire for the Vietnamese sample confirmed the reliability and validity of the instrument with a Cronbach’s alpha of 0.779. A principal component analysis was conducted, and all factor structures were stable and consistent. The findings from the multivariate analysis of variance showed that the leadership styles of Vietnamese higher education leaders were not largely different based on their gender, but the educational background. The descriptive statistics analysis on the demographic items indicated a trend that transformational and transactional leadership were more preferable than laissez-faire leadership in higher education leaders’ performance. 

Promoting learner autonomy: Lesson from using project work as a supplement in English skills courses

Nguyen Van Loi
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This study reports the impact of project work in teaching English skills courses on the learner autonomy of students on an English Language Teacher Education program. The study involved 50 English-majored second-year students in project work over two semesters. Two instruments were employed to assess their learner autonomy: a self-assessment questionnaire, and two group interviews. The result showed that the students gained higher degrees of learner autonomy after one year participating in project work. However, the gain was largely due to an increase in self-decisions about learning. Other aspects of learner autonomy such as self-regulated learning actions, self-responsibility, and attitudes to social interaction remained unchanged.

Reading strategy instruction to Vietnamese young language learners: Teachers’ prac-tices and perceptions

Tran Thi Be Ba, Nguyen Buu Huan
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There has been a growing interest in involving teaching English to young learners in Vietnam in recent years. However, teaching English for children, especially reading is not an easy job although reading is widely known as one of the most important skills in language learning and teaching.  To overcome this difficulty, teachers are likely to implement various reaching strategies that help motivate students to read and involve students in the lessons. This article examines the reading strategies that English as Foreign Language (EFL) teachers reported using in young language learners’ classes and explores teachers’ views of reading strategy types that can attract students’ interests. In this quantitative and qualitative research study, the data were collected through questionnaires and interviews. The results from the questionnaires suggest that of eleven reading strategies, using context clues was the most frequently used. The interview data reveal that four most favorite reading strategies that enhance students’ interests in reading include games, pair work, group work, and role play.

Isolation and selection of lactic acid bacteria that can antagonize Vibrio parahaemolyticus causing acute hepatopancreatic necrosis disease in whiteleg shrimp (Penaeus vannamei)

Nguyen Thi Truc Linh, Nguyen Trong Nghia, Dang Thi Hoang Oanh, Huynh Thanh Phong, Truong Quoc Phu
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This study was conducted from March to June, 2015 to select lactic acid bacteria (LAB) strains that can antagonize V. parahaemolyticus for further studies on prevention of acute hepatopancreatic necrosis disease (AHPND) in shrimp. LAB strains were isolated from different resources including: (1) gut of white leg shrimp (Penaeus vannamei); (2) gut of nile tilapia (Oreochromis niloticus) and (3) shrimp pond sediment in Tra Vinh, Ben Tre, and Soc Trang provinces. Isolated LAB strains were identified by using morphological, physiological and bio-chemical characteristics and then determined their antagonism toward V. parahaemolyticus by using agar well diffusion method. A total of 94 LAB strains were selected for this study (30, 39, 25 isolates from Tra Vinh, Ben Tre, Soc Trang provinces, respectively). For antimicrobial activity, 13 strains could weakly antagonize V. parahaemolyticus with inhibition diameter smaller than 11.0 mm. However, 81 remaining LAB strains could antagonize V. parahaemolyticus with inhibition diameter around 11.0–18.5 mm. Of the 94 strains above mentioned, three strains RP6.5, RP5.4.1 and RP5.5.1 had the biggest inhibition diameters (17.3±0.58 mm, 18.5±0.289 mm and 18.00±0.00mm, respectively). These trains can be used for further studies to evaluate the effect of LAB in prevention AHPND in shrimp.

Effect of associated bacteria on gnotobiotic Artemia performance

Huynh Thanh Toi
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Bacteria naturally occurring in Artemia culture systems act as direct food for the culture organism and also promoter food digestion. However, in the open culture conditions Artemia consume plenty of food sources availability in the pond makes it difficult to evaluate the role of associated bacteria in growth enhancement. So that, this study was conducted under gnotobiotic culture conditions to evaluate the effect of associated bacteria on growth performance (in term of survival and individual length) of Artemia. Bacteria-free baker´s yeast Saccharomyses cerevisiae strain wild-type (WT) was used as a main food source for bacteria-free Artemia nauplii in 6-day culturing. Nine unidentified bacteria strains (HT1-HT9), isolated from culture water of well performance Artemia in our preliminary test, some of these isolates had proven as a diet for Artemia, were added to Artemia culture only one time at a pre-tested concentration of 5x106 cells/mL. The results of this study showed that Artemia performance increased in almost cultures where isolate added as compared to that obtained in Artemia fed WT solely. Especially, the total length of Artemia/tube was obtained nearly double in the culture where HT1, HT3, HT5 and HT7 added, compared to that obtained in WT fed Artemia solely. The results of this study indicated that Artemia not only act as a direct food and the presence of them in the cultures also improvement of Artemia performance.

Giant freshwater prawn (Macrobrachium rosenbergii de Man, 1879) farming in brackish water areas of the Mekong Delta, Vietnam

Tran Ngoc Hai, Nguyen Thanh Phuong, Le Quoc Viet, Huynh Kim Huong, Do Thi Thanh Huong
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Giant freshwater prawn (Macrobrachium rosenbergii de Man, 1879) is one of important aquaculture species in Vietnam, especially the Mekong Delta. Farming of giant freshwater prawn has been so far very well-known in the freshwater area with some important systems, typically the alternative rice-prawn farming system. However, this industry has recently expanded rapidly and largely to the brackish water area. Currently, there is 15,270 ha of prawn culture in the Mekong Delta with total production of 5,306 tons, of which coastal provinces cover for 90.1% of total culture area and 64.8% of total production. Two important systems for prawn culture in the brackish water area are (1) Prawn and rice farming alternatively with tiger shrimp culture on the rice field; and (2) Prawn culture in pond alternatively with tiger shrimp culture. The survey on 108 households in Bac Lieu and Tra Vinh provinces found that while the system (1) is in extensive management with average yields 110 kg/ha/crop and net income of 11.5 millions VND/ha/crop, the system (2) is considered the semi-intensive farming system with average yield and net income of 886 kg/ha/crop and 68 million VND/ha/crop, respectively. A trial on prawn culture in 9 brackish water ponds in Tra Vinh province was also carried out which improved the yield up to 988-1342kg/ha/crop. Prawn culture contributed significantly to the total income of the farming systems. The success of these new farming systems together with a large area of brackish water surface in the Mekong Delta gives the industry a great potential for further development.Key words:

Flocculation efficiency and quality of flocculated algae with chitosan at different pH values

Ngo Thi Thu Thao, Dang Thi Thuy An, Tran Thi Ngoc Hanh
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This study was conducted to determine the effects of different pH values on the flocculation efficiency of chitosan and using flocculated algae as diet for nursing sweet snail larvae. In 1st experiment, Chaetoceros algae were flocculated by chitosan at three pH levels: 1).Control (maintaining at pH=9.0); 2). Adjust to 7.0 and 3). Adjust to 5.0. In 2nd experiment, flocculated algae were stored at temperature of 4oC in 15 days to determine the viability and ability to growth after re-inoculation. In 3rd experiment, flocculated algae were used for feeding sweet snail larvae in 20 days. Algae flocculation reached the highest efficiency (91%) after 4 hours at pH 5.0. At control pH treatment (pH 9.0) Chaetoceros obtained highest cell viability (52.23%). After re-inoculation at initial density of 500,000 cells/mL, the highest cell density was obtained at day 15 in pH 7 (8,750,000cells/mL). After 20 days feeding with different flocculated Chaetoceros, the sweet snail larvae in control pH obtained not only highest survival rate (72.52%) but also the highest shell length and height (1938.89 and 1041.67µm, respectively). Our findings indicated that it was necessary to remain pH value from 7.0-9.0 in order to obtain the high algal cell viability after flocculation with chitosan and effectiveness for using as diet for sweet snail larvae.


Nguyen Thi Thu Tram, Huynh Du Tuyet, Quach Nhat Minh
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A phytochemical study on petroleum ether-diethyl ether (v/v 1:1) extract led to the isolation of one sterol with unsual side chain, 22-dehydro-24-isopropylcholesterol (1) and one common triterpenoid oleanolic acid (2). Compound 1 has been previously identified as a marine invertebrates sterol, here we report the first time its appearance in terrestrial source Polyscias fruticosa. Their structures, including absolute configuration, are elucidated unambiguously by X-ray diffraction, spectroscopic data and comparison with literature.

Fuzzy cluster analysis for probability density functions based on width criterion

Vo Van Tai, Pham Toan Dinh, Nguyen Hoang Yen
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Based on the cluster width of probability density functions (WCD), we establish algorithms for fuzzy cluster analysis and for determining the suitable number of cluster. In addition, determining WCD for two and more than two probability density functions has been also considered by our Matlab produces. The numerical examples in both synthetic and real data are given not only to illustrate the reasonable of proposed algorithms and programs but also to show their advantages in comparing with existing ones.

Determination of coke on promoted zirconium oxide catalysts in the isomerization re-action of pentane and hexane mixture at high pressure

Luu Cam Loc, Nguyen Dien Trung, Nguyen Tri
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A series of bifunctional catalysts: sulfated zirconia, tungstated zirconia and alumina-supported zirconia as effective supports for Pt was been prepared. The structure and the surface property of denatured zirconium oxide catalysts were characterized by using physico-chemical methods such as XRD, BET, SEM, TEM and TPR. Their catalytic activity in isomerization reaction and stability of catalysts was tested by GC. The coke deposited on catalyst surface was determined by a burn-off method. The mass of coke formed on Pt/ZrO2-g-Al2O3 (Pt/ZrAl), Pt/ZrO2-SO4 (Pt/ZrS) and Pt/ZrO2-WO3 (Pt/ZrW) was 5.23%, 4.06% and 1.23% respectively. 

Soil diazotrophic community structure altered in rice crop rotated with mungbean or maize in Cai Lay district, Tien Giang province

Do Thi Xuan, Vo Thi Guong, Anna Rosling, Qiong Wang, Sadhna Alström, Nils Högberg
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Nitrogen availability is often one of the limiting factors for intensive rice (Oryza sativa) cultivation. Rotation of rice with upland crops partially reduces nutrient depletion. This study was carried out at CaiLay district, Tien Giang province with the aim to investigate the effect of alternating the rice crop with maize (Zea mays) and mungbean (Phaseolus aureus)in different rotational systems on the diazotrophic community in soilusing pyrosequencing of the nifH genes. The results showed that the community structure of the diazotroph communities in soils were different when rice crop was alternated with either maize or mungbean crop than that in rice monoculture. The nifH sequences were highly diverse and assigned to eleven bacterial phyla and one Archaeal phylum. Proteobacteria and Firmicutes were the most common phyla carrying the nifH gene. The propotion of the Archaea, Betaproteobacteria, Cyanobacteria, Deltaproteobacteria, Firmicutes, Gammaproteobacteria and Nitrospira was significantly different among the treatments. The relative abundances of Anaeromyxobacter, and Geobacter were greater in RRR than in the RMgR treatment while Heliobacterium and Desulfosporosinus were higher in the RMgR than those in the RRR and RMR treatment.

Environmental and human resource development issues in Vietnam: The case study of the Mekong Delta

Ngan Collins, Sandra Jones, Pauline Stanton, Nguyen Hong Tin
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The Mekong Delta in Vietnam was identified by the International Panel on Climate Change as one of the three most vulnerable deltas in the world to rising sea levels. A study by the International Centre for Environmental Management (ICEM) indicated that about 38% of the Mekong Delta will be submerged if the sea water rises by one metre, resulting in 90% of the agriculture land being flooded, and saline water intrusion increasing by 70%. The impact would be to increase the insecurity of this highly dense populations whose livelihood are dependent on agriculture. In response the Vietnam government has been implementing potentially adaptive strategies, including support for internal migration from the Mekong Delta to urban areas and industrial zones. However, without new skills and knowledge these internal migrants limited employment opportunities. Furthermore those migrants who manage to obtain work face the stress of adapting to industrial working environments and how to obtain knowledge about the industrial relations systems and human resource management processes that regulate their employment. This paper uses secondary data to presents an overview of the challenges for human resources from the internal migration of the climate affected Mekong Delta to urban areas. In doing so the paper pioneers an interdisciplinary approach that links research in environmental issues to research into human resources issues related to skills need.

An investigation into the tale values on the legends of Nguyen Anh (king Gia Long) in the southern region of Vietnam

Le Thi Dieu Ha
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Legend is a genre reflecting the historical figures and events of locals and nations. The historical war between the Tay Son and Nguyen Lords in the Southern battlefield being associated with local historic and cultural imprints has become abundant materials for the formation of an array of legends of Nguyen Anh in the Southern region. This article provides an overview of tale system and its values in terms of content and techniques.

Exploring drivers influencing consumers’ attitude towards mobile marketing

Huynh Nhut Phuong, Nguyen Thuy An
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In the technology era, mobile marketing seems to be an effective tool for companies in delivering promotion message to their customers, for example smartphone. Besides, business entities are faced with challenges of deciding efficient mobile marketing channels in order to attract more potential customers by demonstrating a positive attitude towards this type of modern-day marketing. Therefore, the purpose of this article is to examine the drivers influence customers’ attitude towards mobile marketing via various forms such as Short Message Service (SMS), Multimedia Message Service (MMS), Quick Response (QR) Codes, social networks, games, shopping applications in the case of Can Tho city. By employing the methodologies of Exploratory Factors Analysis (EFA) and regression analysis, the analysis points out that perceived usefulness, perceived enjoyment affect positively customers’ attitude while irritation influences negatively on customers’ attitude. In addition, the study fails to explore a positive relationship between demographic factors and attitude towards mobile marketing. Some suggestions for further study in term of investigating a specific group of customer and a particular type of mobile marketing form are also addressed.