Published: 2017-03-31

Effect of crop rotation on the diversity of the bacterial community colonizing rice straw residues in paddy rice cultured soil in the Mekong Delta of Vietnam

Tran Van Dung, Cao Ngoc Diep
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In this study, the influence of crop rotation on the microbial diversity was investigated over a three crops. The studied crop rotation systems were rice-rice-rice (CRS1), rice-rice-baby corn (CRS2), rice-rice-mungbean (CRS3) and baby corn-rice-mungbean (CRS4).Litter bags containing rice stems were inserted into the soil and recollected at different time points for analysis and they were used to compare with the diversity of the bacterial community colonizing the rice straw by means of 16S rRNA gene based Denaturing Gradient Gel Electrophoresis (DGGE), UPGMA analysis and Shannon index (H) comparision. The results showed that the bacterial diversity colonizing rice straw residues were significantly different in composition in the (CRS4) rotation systemcompared to those in the 3 other systems.There were not significant differences in bacterial Shannon index during cultivation of crop I . In crop II and crop III, the CRS4 rotation system showed a H index higher than this of recorded in the CRS1, CRS2 and CRS3 treatments. The average H over the whole experiment was highest for the CRS4 system( H=1.13) and significantly different compared to the overall average H calculated for the other 2 systems CRS2(H=1.03) and CRS3( H=1.05) ,indicating that crop rotation with two upland crops was a vital key to the improvement of the Shannon index

Effect of different protein sources in the diets on feed intake, nutrient digestibility, growth and carcass value of californian rabbits (Oryctolagus cuniculus) in the Mekong delta of Vietnam

Nguyen Van Thu, Nguyen Thi Kim Dong, Truong Thanh Trung
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Sixty Californian rabbits (Oryctolagus cuniculus) at 45 days of age (470±7.93 g) were arranged in a completely randomized design with five treatments and three replications. Four rabbits (2 males and 2 females) were in one experimental unit. Five treatments were protein sources including the meals of soybean extraction, water spinach leave, fish, feather and blood corresponding to SEM; WLM; FM; FEM and BM treatments, respectively. Para grass (Brachiaria mutica) and Centrocema pubescens were a basic diet for rabbits. The dietary crude protein (CP) and metabolizable energy (ME) were formulated at the level of 19.0% and 11.6 MJ/kgDM in the different treatments. The apparent nutrient digestibility and nitrogen retention were observed when rabbits being at 12 weeks of age. The results showed that dry matter and CP intakes were significantly higher (P

Development of an efficient in vitro plant regeneration protocol for indica rice varieties (Oryza sativa L.) in the Mekong Delta of Vietnam

Tran Thi Xuan Mai, Tran Thi Cuc Hoa, Geert Angenon, Nguyen Thi Lien
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In this study, the effects of medium components and environmental conditions on callus induction and regeneration potential of two indica rice varieties (IR64 and MTL250) were evaluated.  Mature seeds were cultured on four different medium formulations including either Murashige and Skoog (MS) or Chu (N6) for callus induction. The MS medium was found more suitable than N6 medium in terms of callus induction frequency. The highest callus induction rate with good quality was obtained on MS medium containing 2mg/L 2,4D, 112mg/L B5 vitamin, 500mg/L proline,  500mg/L glutamine, 300mg/L casein hydrolysate, 30g/L sucrose and 4g/L phytagel. To investigate the best condition for callus growth, the influences of incubation temperatures and light conditions on callus induction of IR64 and MTL250 varieties were examined. The experimental results clearly showed that incubation temperatures at both 28oC and 32oC had no significant effects on callus induction in both varieties.  However, periodic illumination for 16 hours/day and complete darkness proved the best effect on callus induction in MTL250 and IR64, respectively. Among 07 different media used for shoot induction, the best results were obtained when calli of IR64 and MTL250 were cultured on medium containing MS including vitamins + 2.0 mg/L BAP + 0.5 mg/L NAA + 20g/L sucrose + 30g/L sorbitol + 6g/L phytagel. Shoot regeneration by using medium supplemented with kinetin, moreover, was very low or even failed in both varieties. This plant regeneration protocol is considered to be significant improved and promises to serve for breeding or genetic engineering of indica rice varieties in the Mekong Delta of Viet Nam.

Stock returns volatility persistence and spillover effects: Empirical evidence from Vietnam

Le Tin, Yolanda T. Garcia, Nguyen Huu Dang
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This study aimed to investigate stock returns volatility of the Ho Chi Minh and Ha Noi stock exchanges. The used data in the study were the daily stock indexes of the Vietnam stock market and nine global stock markets from the State Securities Commission of Vietnam (SSC) and Yahoo Finance website, respectively. The Generalized Autoregressive Conditional Heteroscedasticity (GARCH) model was performed to investigate the determinants of the persistence of volatility and volatility spillovers from foreign stock markets.  The results indicated that there are evidences of volatility clustering and persistence of volatility in the two stock exchanges of Vietnam. This study also showed that both Ho Chi Minh and Ha Noi stock exchanges are affected by major stock markets in Asia and the rest of the world. Specifically, the Vietnam stock market is mostly influenced by Singapore stock market.

Determinants of poor household income in Ca Mau province, Vietnam

Vuong Quoc Duy
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This paper investigates the determinants of poor household income in Ca MauprovinceofVietnam. Data used in the paper is 160 observations gathered from U Minh and Cai Nuoc districts in Ca Mau province. By using the descriptive statistics andOrdinary Least Squaremodel, the findings illustrate that the income of poor households in Ca Mau provine ofVietnamis statistically significant affected by various variables to the poor households’ characteristics as well as economical issues. Such factors are the age of households’ head, cultivated land area, and generated earning activities and the mean of productions. Among given variables, the age of household head is inverse U-shape affecting on the income of the poor households. 

Evaluating the impact of supply chain capabilities to the business success: A case study in small and medium food companies in Mekong Delta

Tran Thi Tham, Tran Thi My Dung
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Growing in the competitive environment, organizations need to find ways to improve their performance even better by ensuring that all key drivers are being developed and utilized effectively. The aims of this study is to examine the impact of supply chain capabilities on competitive advantages and business performance in small and medium food companies in Mekong Delta. The data were gathered from conducted surveys with 68 small and medium food companies in Mekong Delta, and were analyzed using Structural Equation Modeling (SEM). The empirical results show that supply chain capabilities play an important role in the business improvement. They have direct effects on competitive advantages and indirect effects on business performance through competitive advantages. 

Blending of vegetable oils and chemical modification by epoxidation followed by oxirane ring-opening reaction

Phan Hong Phuong, Dao Thi Kim Thoa, Nguyen Kim Trung, Hoang Chi Phu
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In this paper, vegetable oil as refined soybean oil, refined sunflower oil and their blends of different proportions have been investigated. The physicochemical properties such as viscosity, acidity value, iodine value and saponification value have been reported. From the result, the blend of vegetable oils with volume ratio at 20:80 has higher viscosity index than individual vegetable oil, as well as suitable acidity and saponification value. However, iodification of this blend is relatively high, indicating that this blend has a low oxidation stability. Hence, this mixture has been continually exposed to epoxidation reaction with the purpose of removing the presence of double bond C=C followed by oxirane-ring open reaction. The results indicate that temperature, time of reaction, molar ratio H2O2/C=C influence significantly on iodine value of obtained blend. The following conditions in epoxidation step: CH3COOH/C=C 1:1; time of reation 7h, temperature of reaction 60oC, stirring speed 500 rpm and H2O2/C=C 3:1 can reduce effectively iodine value, from 129.6 to 6.9. In the oxirane-ring open reaction, n-butanol is used as reagent and the final product has higher viscosity compared to epoxidized blend.

Phosphate solubilizing microorganisms isolated from manoa soil in Oahu, Hawai’i

Kim Lavane
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Phosphorus (P) is an important nutrient next to nitrogen. It is an essential element in the soil for plant development and growth of microorganisms. The common method to supply phosphate to plants is to add soluble mineral phosphate fertilizers into soil. However, this practice is not cost effective. This study attempted to isolate phosphate-solubilizing microorganisms which can solubilize insoluble rock phosphate to a soluble form. Soil microorganisms were isolated from root and soil samples at the rocky site of Waahila Ridge, Manoa area. Large numbers of fungi and bacteria were recovered. The microorganisms were purified by transferring twenty-four of single colonies to YMA agar. The isolates were then examined for their ability in rock phosphate solubilization. All isolates showed the positive activity and generated different levels of soluble phosphate concentration associated pH drop in the liquid medium. Two out of nineteen isolates showed the highest activity in solubilizing North Carolina rock phosphate and the soluble phosphate concentration in the liquid medium were 19.33mg/L and 18.1mg/L. This study demonstrated that selected soil microorganisms could convert insoluble phosphate to soluble form generally through the process of acidification.

Application of response surface methodology for optimizing transesterification of coconut oil

Le Thi Men, Luu Cam Loc, Nguyen Van Dat, Nguyen Quoc Chau Thanh, Ho Quoc Phong, Duong Nguyen Thach Thao, Trac Hue Phuong, Cao Dang Khoa, Phan Viet Hai, Do Vo Anh Khoa
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This work considered the use of coconut oil for the synthesis of renewable and environmentally friendly biodiesel as an alternative to conventional diesel fuel. Response surface methodology (RSM) with central composite design (CCD) was applied for the determination of optimum condition. The results showed that an optimum biodiesel yield of 93.03% could be obtained under the following reaction conditions: methanol content of 23.67% (by weight with respect to the oil), catalyst concentration of 0.5% (by weight with respect to the oil), and the reaction time of 120 minutes. These obtained results demonstrated the potential of coconut oil as good feedstock for biodiesel production in Mekong River Delta.

Sorption of As5+ from aqueous solution by lepidocrocit (γ-feooh) nanoparticle

Nguyen Dinh Trung, Truong Dong Phuong
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Abstractγ-FeOOH nanorods adsorbent for As5+ removal was prepared by a chemical co-precipitation method. The maximum adsorption capacities for As5+was 63.75 mg/g at pH= 6.0, higher than of Fe2O3, Fe3O4... The adsorption data accorded with Freundlich isotherms. At study pH, for arsen, the adsorption equilibrium was gained after 90 min. Kinetic data fitted well to the pseudo-second-order reaction model. Competitive ions hindered the adsorption according to the decreasing sequence sulfate, ammonium and chloride. The high adsorption capability and good performance on other aspects make the γ-FeOOH nanorods a promissing adsorbent for the removal of As (V) from groundwater.Keywords:As ; sorption; kinetic; γ-FeOOH nanoTOM TATγ-FeOOH dang nano dung lam vat lieu hap phu As5+ duoc dieu che bang phuong phap dong ket tua. Tai pH = 6,0, dung luong hap phu cuc dai cua vat lieu doi voi As5+ la 63,75 mg/g, cao hon so voi mot so vat lieu lam chat hap phu asen nhu Fe2O3, Fe3O4. Mo hinh hap phu dang nhiet Freundlich phu hop mo ta qua trinh hap phu As5+ boi γ-FeOOH, thoi gian dat can bang hap phu la 90 phut. Dong hoc hap phu tuan theo phuong trinh dong hoc hap phu bac 2. Xuat hien canh tranh cua cac ion la voi As5+ trong qua trinh hap phu tuan theo trat tu giam dan tu sulfate, amonium va chloride. Dung luong hap phu cuc dai cua vat lieu, cung nhu viec dieu che de dang, gia thanh thap cua γ-FeOOH, lam cho no tro thanh chat hap phu hap dan va day hua hen trong viec xu ly asen trong nuoc ngam.Tu khoa: As; hap phu; dong hoc hap phu; γ-FeOOH nano

Task-based language teaching and its impact on Vietnamese students’ use of self-regulated learning strategies in a writing classroom

Phuong Hoang Yen
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Over the past two decades, there has been an increasing emphasis on independent learning and students have been encouraged to take personality for their studies. In that context, self-regulation is seen as a vital ingredient to performance in educational setting ( Zimmerman, 1990, 2000; Wolters and Rosenthal, 2000). How to promote students’ self-regulated learning is a crucial question among educators since SRL does not take place automatically (Winne, 2005) and is not easily induced (Struyven et al., 2006). Therefore, research about the conditions that facilitate SRL attracts greater attention (Richardson, 2001). As such an attempt, the current empirical study investigates the extent to which task-based language teaching (TBLT) can help Vietnamese students increase the use of self-regulated learning strategies in a writing classroom. Sixty-nine students were instructed to write descriptive and argumentative paragraphs under task-based learning condition during a period of ten weeks. Results show that students significantly improved their overall scores of self-regulatory writing strategies, especially their scores of personal self-regulation.

Optimization of polyphenol, flavonoid and tannin extraction conditions from Pouzolzia zeylanica L. benn using response surface methodology

Nguyen Duy Tan, Le Quoc Viet, Vo Tan Thanh, Nguyen Minh Thuy
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In this study, the extraction of phenolic compounds from Pouzolzia Zeylanica L. Benn was conducted by using pure water as a solvent. The optimal conditions for the extraction of three phenolic compounds such as polyphenols, flavonoids and tannins were determined by using response surface methodology (RSM). A central composite design (CCD) was applied to investigate the effects of three independent variables, namely the ratio of water-to-dried material (20:1 to 30:1, v/w), temperature (70 to 90oC ) and time extraction (20 to 40 minutes). The dependent variables were total polyphenol content (TPC), total flavonoid content (TFC) and tannin content (TC). A second-order polynomial model was used for predicting the response. Optimized conditions for bioactive compounds extraction, water-to-dried material ratio, time and temperature extraction were 27 (v/w), 30 minutes and 81oC, respectively. The experimental values agreed with predicted values within a 95% confidence interval. Total polyphenol, flavonoid and tannin content extracted by these optimized conditions were achieved (521 mgGAE/100g dried material (DM), 363 mgQE/100g DM and 643 mgTAE/100g DM, respectively).

The kinetics study on 5- formyltetrahydrofolic acid degradation and 5,10- methenyltetrahydrofolic acid formation during thermal and combined high pressure thermal treatments

Nguyen Minh Thuy
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The effect of different pHs (3.4 to 7.0) on 5-formyltetrahydrofolic acid (5-CHOH4PteGlu) stability during thermal (80-110°C) and high pressure thermal (100-800 MPa/65-70°C) processing was studied. The results showed that (i) the degradation of 5-CHOH4PteGlu during treatments (in the presence of ascorbic acid) was not only due to oxidation but also due to a conversion to 5,10-methenyltetrahydrofolic acid (5,10-CH=H4PteGlu), (ii) multiple response analysis was successfully applied to describe the kinetics of 5-CHOH4PteGlu degradation during thermal and/or high pressure processing. 

An Ab initio study of cis-[PTCL2(Ipram)(Hpz)] binding to base purines guanine and adenine

Pham Vu Nhat, Bui Thuy Vy
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Quantum chemical calculations are employed to examine interactions of hydrolysis products of cisplatin and a novel derivative cis-[PtCl2(iPram)(Hpz)] with the purine base sites of DNA using guanine and adenine as model reactants. Thermodynamic parameters, electronic structures, bonding characteristics and spectroscopic properties of the resulting complexes are investigated in the framework of density functional B3LYP method along with correlation-consistent basis sets. The computed results show that these interactions are dominated by electrostatic effects, namely H-bond contributions, and there exists a flow charge from H atoms of ligands to the base. Another remarkable finding is that the replacement of ammine groups by larger ones accompanies with a somewhat moderate reaction between PtII and the nucleobases.

Synthesis of branched conjugated copolymers based on triphenylamine and 3-hexylthiophene units

Nguyen Thanh Trung, Nguyen Tran Ha, Nguyen Anh Thu, Nguyen Thi Le Thu
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Abstract            The branched conjugated copolymer based on triphenylamine and 3-hexylthiophene has been synthesized via Suzuki polycondensation reaction in the presence of Pd(PPh3)4 and K2CO3 as catalytic system. This conjugated polymer named poly(triphenylamine-branched-3-hexylthiophene) (P(TP-b-3HT)). The reaction was carried out at 100oC in 24 hours in the toluene media. The average molecular weight of obtained polymers was 42000 g/mol by gel permeation chromatography (GPC) with polydispersity index of 2.2. The structure of P(TP-b-3HT) was determined by 1H NMR, and optical properties of obtained polymer was characterized via UV-Vis.Tóm tát            Mot loai polyme dan dien moi voi cau truc mach nhanh duoc tong hop tren cac don vi triphenylamine va 3-hexylthiophene bang phan ung trung hop Suzuki trong su hien dien cua he xuc tac Palladium phosphine (Pd(PPh3)4) va muoi kalicarbonate (K2CO3). Polyme dan dien nay duoc dat ten la poly(triphenylamine-branched-3-hexylthiophene) (P(TP-b-3HT)). Phan ung trung hop polyme duoc tien hanh o 100oC trong 24 gio trong dung moi toluene. Trong luong phan tu khoi trung binh cua polyme thu duoc la 24000 g/mol duoc phan tich qua phuong phap sac ky cot (GPC), polyme co do da phan tan trong luong phan tu la 1.8. Cau truc hoa hoc cua polyme duoc xac dinh qua pho cong huong tu hat nhan proton (1H NMR), va tinh chat quang cua polyme duoc danh gia qua cac phuong phap phan tich nhu la pho hap thu UV-vis.

Social impacts of tourism development on local community: A case study at dong Hoa Hiep village, Cai Be district, Tien Giang province

Le Thi To Quyen
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In this research, the author conducted an investigation on both positive and negative social impacts of tourism development on Dong Hoa Hiep's villagers, Tien Giang province by five Likert scale surveyed questionnaires and in depth interviews. The questionnaires carried out a total of 400 local representative villagers used in statistical analyses. The study showed that tourism development created both positive and negative social impacts on local communitties, whereas the social advantages of tourism overweighed its drawbacks. The positive impacts were recognized such as improving in general infrastructures, and increasing the quality of life of local people, while the negative effects were seen rarely oppotunities for local people joining in planning and managing tourism activities of Dong Hoa Hiep village and the insistence of some needed children and vendors on tourists to buy products.

Sub-disciplinary variation in the move structure of English-medium research article introductions in applied linguistics

Do Xuan Hai
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This article reports on a recent corpus and genre-based investigation of the move structure in research article introductions (RAIs) in two constituent areas of inquiry in applied linguistics, namely language teaching & learning and pragmatics & discourse analysis. The corpus consists of 30 RAIs extracted from 30 parent empirical research articles written by English native speakers and published in high impact English-medium applied linguistics journals between 2011 and 2013. The analytical tool was developed both with reference to Swales’ (1990, 2004) CARS models and a preliminary examination of the corpus built for this particular study. Findings revealed sub-disciplinary corpus-based variations of this schematic structure, both at the move and step tiers.

Sustainability and livelihood opportunities for mangrove-shrimp farmers in the coastal areas of SocTrang province

To Lan Phuong, Nguyen Hong Tin, Roel Bosma, Lam Thanh Si, Dang Kieu Nhan
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This study aims to assess the sustainability of the integrated mangrove shrimp system and livelihood improvement opportunities for farmers in the coastal areas. A baseline assessment (focus group discussion-3 groups of 24 participants and households’ interviews of 35 farmers) and on-farm studies were carried out. Data and indicators related to sustainability including natural, financial and environmental aspects were gathered and analysed. Study results show that the integrated mangrove shrimp was sustainable system overtime. It has very low production costs and investment that suits to farmers’ existing resources. Farmers invested 3.6 ±0.9 million vnd per hectare of water surface a year, which could earn a net revenue approximately 24 million vnd/year. Beside shrimp as a primary main harvested product, the system also harvests several second products such as crab and other aquatic animals. Farmers in coastal areas could improve their livelihoods and income sources through intervening farming techniques and diversifying livelihood activities. Along with above achievement, the system is currently facing problems and challenges. On top of that, inaccessibility to good quality shrimp seeds, diseases on shrimp, sedimentation, climate change impacts, and policies limit to timbering, were key limiting factors to the integrated mangrove shrimp system. So far, technical intervention and flexible management on mangrove forest need to be considered and adjusted. 

The development of Cai Rang floating market tourism in Can Tho city, Vietnam: From policy to practice

Nguyen Thi Huynh Phuong
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In recent years, floating market tourism has been regarded as a unique and attractive form of tourism in the Mekong Delta, Vietnam. It combines eco-tourism together with cultural and community-based tourism to reach the ultimate goal of sustainable development. Floating markets can be looked upon as part of the river culture and eco-tourism of Vietnam rather than simply as a tourist attraction, as they play an important part in the river - based culture of Southeast Asia. There are approximately eleven floating markets in the Mekong Delta, yet Cai Rang attracts more visitors than those in the surrounding provinces. The reason might be due to the advantages the market possesses: geographical location, size, infrastructure and material, technical basis for tourism, services, and connection with other tourist attractions. Therefore, Can Tho city has increasingly received the interest from the government as seen through a number of documents for tourism development. This article aims to study, based on documentary, quantitative and qualitative research, the development of Cai Rang floating market tourism in Can Tho city. It is proposed that Vietnam’s policy on tourism has enabled favorable factors for the development of floating market in the Mekong Delta such as economic development plans, strategic orientations and specific objectives. Nevertheless, there is still a gap between policy and practice and this is a big challenge for the development of Cai Rang floating market tourism.