Can Tho University
  • Cần Thơ, Vietnam
Recent publications
Artificial diets promised an economical way to mass-produce entomophagous arthropods for augmentative biological control. To date this promise generally has not been fulfilled and most of the commercial mass production of entomophagous arthropods is accomplished in vivo. Although many successful artificial diets have been published, these diet formulations have not progressed to commercial use. In some cases, the arthropods produced are of poor quality. In other cases, the diet formulations are expensive to produce and not commercially viable. Alternatively, the methods to produce arthropods in vitro are complicated and require too much labor for commercial application. In this chapter, we propose that most of the published artificial diets have not been fully developed to their potential and represent a continuous work in progress. A proposed pathway for moving artificial diet development to commercial application is presented in this chapter; the pathway consists of six levels of advancement based on the magnitude of capabilities to produce arthropods. This chapter makes evident that the process of artificial diet development is a multidisciplinary enterprise that will benefit from industry and government support and recent technological advancements.
Despite the well-known potential of earthworms to modify soil macroporosity and water infiltration through their burrowing activities, it is still difficult to predict which species are more effective in increasing water infiltration. We thus investigated the relationships between soil water infiltration, burrow network properties, morphology and anatomy of a diversity of earthworm species. We sampled 23 earthworm species in northern Vietnam and measured 16 morpho-anatomical traits a priori linked to their feeding, vertical distribution or burrowing behaviour. One individual was then incubated in a repacked soil core for four weeks under laboratory conditions, each in four replicates. After incubation, burrow network properties were assessed using X-ray computed tomography, and soil saturated hydraulic conductivity was measured using the falling head method. We found large differences among species belonging to similar or different ecological categories in their effect on soil saturated hydraulic conductivity. We observed neutral to positive effects with an increase of up to 30-fold compared to cores without earthworms. The effect of earthworms on soil hydraulic conductivity was well predicted by burrow network properties (volume and continuity of burrows) or morpho-anatomical traits (body weight, circular and longitudinal muscles thickness) using the random forest regression models (R² > 0.95 in both cases). Earthworms with a large body weight and circular and longitudinal muscle thicknesses have the highest probability of increasing soil saturated hydraulic conductivity compared to other species. In addition, we showed from the coinertia analysis that body weight and circular and longitudinal muscle thickness were positively associated with the volume and continuity of burrows. Our findings therefore illustrate the power of employing a trait-based approach to predict the effect of non-Lumbricidae earthworms on water infiltration in comparison to the classical ecological category approach. Such trait information could be used to prioritize practices that favour the expression of more desirable earthworm traits to increase soil water infiltration.
Purpose: Rheumatoid arthritis, a chronic and progressive inflammation condition in the joints, has significantly reduced the patient quality of life and life expectancy. Crucially, there is no complete therapy for this disease, and the current treatments possess numerous side effects. Thus, novel therapeutic approach is necessary. To that end, this study developed novel silk fibroin in-situ hydrogel containing Sesbania sesban L. extract, a plant with high anti-inflammatory actions that are beneficial for rheumatoid arthritis treatments. Methods: The hydrogels were manufactured using simple method of spontaneous gelation at different temperature. The gel properties of morphology, gelation time, viscosity, gel strength, stability, drug loading capacity, drug release rate, and in-vitro anti-inflammatory activity were investigated with appropriate methods. Results: The optimal formulation had highly porous structure, with a gelation time of 0.5 h at room temperature and bodily temperature of 37oC, a viscosity of 2530 ± 50 cP, a gel strength of 1880.14 ± 35.10 g, and a physical stability of > 6 months. Moreover, the hydrogel contained the Sesbania sesban L. leaf extract with a total phenolic content of 92.8 ± 8.30 mg GAE/g, and sustained the release rate for > 20 dạys, followed the Higuchi model. Regarding the in-vitro activities, all formulations were non-toxic to the RAW 264.7 cell line and demonstrated comparable anti-inflammatory activity to the free extract, in terms of the NO reduction levels. Conclusion: Conclusively, the systems possessed potential properties to be further investigated to become a prospective rheumatoid arthritis treatment.
The Vietnamese government has implemented many changes to improve the English competencies of the Vietnamese people. However, the results seemed unsatisfactory because the English as a foreign language teachers had been affected by many external factors. Thus, this study addressed two main research questions, including (1) What external factors affect EFL teachers’ responses to English language teaching pedagogical reforms? and (2) How these factors affect different groups of teachers in light of their backgrounds? This study was designed as a mixed-methods approach using a questionnaire and semi-structured interviews to answer those questions. The current study involved 102 EFL high school teachers working in the Southwest of Vietnam. The results showed that the factor on students’ learning outcomes was the most influential external factor. Besides, the influence level of external factors was differed by the teachers’ educational qualifications in the influence level of some external factors, namely previous educational policies, students’ learning outcomes, and school facilities. At the end of this paper, some critical discussions, educational implications, limitations, and recommendations for further research are presented.
Introduction Strategies for increasing rice production in the Asian Mega-Deltas have led to environmental degradation, resource overexploitation, and high greenhouse gas emissions. Certified sustainable production labels can support governments in their efforts to render rice value chains more sustainable by simultaneously fostering planetary and human health. Little is known, however, about how consumers trade off sustainability and health attributes in staple crops such as rice. This study aims to fill this knowledge gap by investigating Vietnamese consumers' preferences and willingness to pay for rice characterized by multi-attribute sustainability and health certification labels. Methods We collected empirical data from 410 supermarket consumers in Can Tho, Vietnam using a choice experiment survey. The results were analyzed using a mixed logit model to determine consumers' preferences for sustainability and health traits in rice. Four price levels were used to elicit willingness-to-pay for four certification labels: low-emission, eco-friendly, ethically produced, and low glycemic index rice. By separating the components that make up the concept of sustainability and by including a label related to personal health and diet preferences, we are able to gain an understanding of the value consumers place on attributes that benefit the common good vs. attributes that benefit the individual consumer. Results The results showed that consumers were willing to pay a price premium for all certification labels, with the highest marginal utility assigned to low glycemic index rice. Discussion Certification of eco-friendly and ethical production generated similar utility levels, while low-emission rice was valued lower, although it still fetched a significant price premium compared to the status-quo option of rice with no certifications. The results of this study can help policymakers and value chain actors develop rice value chains that integrate sustainable production practices as well as foster the nutrition and health of rice consumers.
The adsorption behaviour of the 5-fluorouracil (5FU) on small gold clusters Au N with N = 6, 8, 20 was evaluated by means of density functional theory using the PBE-D3 functional in combination with a mixed basis set, i.e. cc-pVDZ-PP for gold atoms and cc-pVTZ for non-metal elements. The binding energies between 5FU and gold clusters were determined in the range of 16–24 and 11–19 kcal/mol in gas-phase and aqueous media, respectively. The corresponding Gibbs energies were found to be around -7 to -10 kcal/mol in vacum and sigificantly reduced to -1 to -6 kcal/mol in water solution, indicating that both the association and dissociation processes are likely spontaneous. An analysis on the charge density difference tends to confirm the existence of a charge transfer from the 5FU molecule to Au atoms. Analysis of the surface-enhanced Raman scattering (SERS) spectra of 5FU adsorbed on the Au surfaces shows that the stretching vibrations of N−H and C=O bonds play a major role in the SERS phenomenon. A mechanism for the drug releasing from the gold surfaces is also proposed. The process is triggered by either the low pH in cancerous tumors or the presence of cysteine residues in protein matrices.
Prediction models for enteric methane (CH4) emissions from beef cattle proposed by various groups may not perform with similar accuracy for the low- and middle-income countries in South-east Asia (SE-Asia) because beef cattle in these countries are raised under different climatic conditions with diverse feeding systems, and have different CH4 emission characteristics. The objectives of this study were to: i) predict CH4 emission (g d⁻¹ animal⁻¹), yield [g kg⁻¹ dry matter intake; DMI)⁻¹], intensity [g kg⁻¹ average daily gain)⁻¹], and CH4 conversion factor (Ym) using an intercountry database of individual animal records from SE-Asia; ii) evaluate the impact of different dietary forage contents (all-, high- and low-forage) representing the diverse feeding systems on CH4 emission, yield, intensity and Ym in SE-Asia; and iii) cross-validate equations from this study with published data. A total of 398 individual animal observations of beef cattle from SE-Asia were used for this analysis. Linear models developed by incrementally adding covariates revealed that CH4 emission model using only DMI fitted to all data had a root mean square prediction error (RMSPE) of 16.9%. Subsets containing data with 100% forage in the diet (all-forage), 50–85% (high-forage) and < 50% (low-forage) had an RMSPE of 16.5%, 14.7%, and 17.4%, respectively. Linear multiple equation based on DMI and dietary NDF concentration (DMI + NDF_C, RMSPE = 15.2%; all-data) improved prediction accuracy over that of DMI alone. The DMI + NDF_C models for all-forage (RMSPE = 14.6%) and high-forage subsets (RMSPE = 13.3%) except for low-forage (RMSPE = 16.4%), improved the precision and accuracy of CH4 emission prediction. Methane yield and CH4 emission intensity could not be reliably modelled with the current database. The present study provides improved CH4 prediction models for beef cattle managed under diverse feeding systems in SE-Asia and affirmed that region-specific models are needed to reliably predict beef cattle CH4 emission at national or regional levels, particularly for low- and middle-income countries.
This study aimed to assess the current state of the shoreline and the effects of erosion on the shoreline in Vinh Chau Town, Soc Trang Province, Vietnam. Satellite image overlays were used to quantify the variation in the shoreline as a result of erosion caused by changes in wave action. In addition, the wave measurements were implemented at three representative shoreline protection sections (sea dike, mangrove forest belt, and the breakwater) to evaluate the wave height reduction at the shoreline. The results showed that erosion affected approximately 23 km (32%) of 72 km coastline of the study area. The erosion penetrates the land area from −16.9 to −3.0 m/year (Landsat images) and −11.68 to −7.95 m/year (Google Earth images); the coastline recession increases every year, leading to the gradual loss of mangrove forests and also farmland. The wave measurement shows the effectiveness in wave height reduction of the mangrove forest and the constructed breakwater to protect the sea dike. Wave height reduces more than 50% when passing through the mangrove forest belt, corresponding to a maximum height (Hmax) of 62.3%, 1/10 Hmax at 55.3%, and 1/3 Hmax at 54%. For the constructed breakwater, the wave reduction efficiencies recorded due to Hmean are 72.18% and 1/10 Hmax are 73.16% and reach 72.47% with 1/3 Hmax. The results are based on wave measurement over a short time period; thus, it is not possible to conclude about the wave reduction efficiency of the current measures in the long term. It is necessary to monitor continuously and with different wind seasons to have a more accurate assessment of wave reduction efficiency.
The present study investigates the crystallographic-texture effects on the improved fatigue resistance in the CoCrFeMnNi high-entropy alloys (HEAs) with the full-size geometry of the American Society for Testing and Materials (ASTM) Standards E647-99. We exploited X-ray nano-diffraction (XND) mapping to characterize the crystal-deformation levels ahead of the crack tip after stress unloading under both constant- and tensile-overloaded-fatigue conditions. The crack-tip blunting-induced much higher deformation level was concentrated surrounding the crack-tip which delays the fatigue-crack growth immediately after a tensile overload. The predominant deformation texture orientation in the Paris regime was investigated, using electron backscatter diffraction (EBSD) and orientation distribution function (ODF) analyses. The twinning formation-driven shear deformation gave rise to the development of the Goss-type texture within the plastic deformation regime under a tensile-overloaded-fatigue condition, which was attributed to enhance the crack deflection and thus the tensile-induced crack-growth-retardation period in the CoCrFeMnNi HEA. Our new findings address the quantitative discrepancy found in our earlier work.
The paper provides new evidence of the effect of temperature and precipitation on crop profit of farmers applying different farming systems across different seasons as well as geographical regions in Vietnam for the period 2004‐2016. The result finds that the effect of fluctuation in temperature and rainfall on the crop profit of farmers is not uniform across the three regions (North, Central, South) and also considerable variation across rain‐fed and irrigated farms. For the rain‐fed farming system: (i) rainfall in the dry season has a non‐linearly (Ո) association with the profit, but rainfall in the rainy season has no effect, (ii) dry season temperature and rainy season temperature have, respectively, Ո‐shaped and U‐shaped relationship with the profit. For the irrigated farming systems: the temperature in the dry season and rainy season have a U‐shaped relationship with the profit. The findings show that the irrigated farming systems have been effective in the long term in the face of climate change. Therefore, in preparation for adaptation to climate change, the Vietnamese agricultural sector needs a complete irrigation system at both farm and regional levels.
This study aimed to (i) evaluate purple nonsulfur bacteria (PNSB) strains possessing the highest phosphorus (P) solubilizing capacity in field and (ii) determine the efficacy of PNSB biofertilizers in improving soil quality, P uptake, growth, and yield of pineapple cultivated in acid sulfate soil (ASS). A field experiment was conducted in a completely randomized block design with two factors, including the first factor as P fertilizer levels (0, 50, 75, and 100% P) based on recommended fertilizer formula (RFF) and the second factor as supplementation of biofertilizers containing P solubilizing PNSB (no inoculated PNSB, Rhodobacter sphaeroides W48, R. sphaeroides W42, and a mixture of R. sphaeroides W48 and W42). The results indicated that the supplementation of PNSB biofertilizers led to an increase of 25.3–33.9% in soluble P concentration in soil compared to control treatment. Among the selected PNSB strains, R. sphaeroides W42 and a mixture of the PNSB in biofertilizers solubilized all insoluble P fractions (Fe-P, Al-P, and Ca-P) and strain W48 in biofertilizers for Fe-P and Al-P. Furthermore, the supplementation of biofertilizers from R. sphaeroides W48 and W42 individually and their mixture raised plant height by 3.56–4.10% and available P concentration by 25.3–33.9%. Total P uptake in pineapple treatments with biofertilizers from mixed PNSB was 42.9% higher than that in the control treatment ( p < 0.05 ). Application of mixed PNSB strains can reduce 25% P of chemical fertilizer, but the pineapple yield rose over 12.1%. Both R. sphaeroides W48 and W42 are potent for use as crop yield enhancers to obtain the sustainable pineapple cultivation under acidic stress.
Endolichenic fungi are considered a promising source of new materials. For further evaluation of some biological activities of the Trichoderma strains isolated from lichens Dirinaria spp. and Cryptothecia spp., their antifungal and antibacterial activities were screened by the methods of dual culture and environmental toxicity. Substrate degradation was evaluated using the qualitative enzyme assays. Fourteen strains of Trichoderma spp. were isolated from 60 lichen samples. All the isolates were able to inhibit the radial growth of tested fungal strains ( Bipolaris spp., Colletotrichum spp., Corynespora cassiicola , and Fusarium spp.). Otherwise, only 12/14 isolates were found capable of competing for substrates with Ralstonia solanacearum . The cell-free supernatant obtained from the cultures possessed both antifungal and antibacterial activities. The antagonistic activity of the isolates was selective. Most of the isolates were able to degrade at least one of the investigated substrates, namely cellulose, pectin, and starch. All strains could produce peroxidase; none of the isolates possessed laccase and tyrosinase. A potential antagonistic fungal strain VDT6 has been identified as Trichoderma harzianum . The assessment results indicated that the Trichoderma isolates could be used in agriculture as biological control agents.
Background. The characteristics of acid soil, often low pH and high toxicity, affect the growth and yield of plants. Aims. This study evaluates the effects of supplemented lime and microbial organic fertilizer on glutinous corn (Zea mays) and watermelon (Citrullus lanatus) yield, yield components, and economic efficiency on acid-sulfate soils. Materials and Methods. Two experiments were carried out in Phung Hiep District, Hau Giang Province, as a typical acid-sulfate soil area. The randomized complete block with four treatments and three replicates was designed for the experiment, in which supplemented fertilizers were 800 kg of lime/ha; 2,000 kg of microbial organic fertilizer/ha; and 800 kg of lime in combination with 2,000 kg of microbial organic fertilizer/ha, and treatment as farmer dose (FFT), without lime and microbial organic fertilizer. Results. As a result, using lime combined with microbial organic fertilizer increased the yield compared to using only lime or microbial organic fertilizer. Besides, the incomes increased to 12.0% and 13.8%, respectively, compared to farmer recommendations. Conclusion. To improve the yield of glutinous corn or watermelon and income on acid-sulfate soils, lime should be applied at 800 kg combined with 2,000 kg of microbial organic fertilizer/ha.
Craft village tourism plays an essential role in preserving and promoting local cultural values, contributing to local socio-economic development. This study aims to analyze the actual situation and propose solutions to develop tourism in Chau Giang brocade weaving village. The study collected data from 67 households in Chau Giang brocade weaving village. From the actual survey results and expert consultation, the study suggests several solutions for tourism development in Chau Giang craft village. (1) Strengthen the connection between tourism service suppliers with local authorities and travel agencies. (2) Invest in designing new and unique products to attract more tourists. (3) Improve the quality of tourism services by the professionalism of the community. (4) Develop suitable marketing strategies. Keywords: solution, Chau Giang brocade weaving village, craft village tourism.
We study the band valley modification induced by isotropic strain in monolayer WSe 2 using the non-local van der Waals density functionals theory including the spin–orbit coupling effect. The dominant contributions of orbitals to the band extrema, spin splitting, and exciton diversity in monolayer WSe 2 are visually displayed. The vertical shift of the d and p partial orbitals of W and Se atoms, respectively, at band edges under strain results in a notable reduction of the bandgap. Under tensile strain, the deformations of the band valleys lead to an additional appearance of optical excitons and the disappearance of momentum excitons. Therefore, the experimental observations of the changes in the radiation spectra such as the redshift of A and B excitons, blueshift of C and D excitons, enhancement of intensity, localization, and symmetrization of the exciton resonances can be explained thoroughly. Under compression, the band valley modification may lead to an additional appearance of momentum excitons and the disappearance of optical excitons. The compression is predicted to cause the blueshift of A and B excitons while it brings the redshift to C and D excitons. An asymmetric broadening and intensity de-enhancement of the exciton resonances are also found when a compression strain is applied. The modification of the band valleys can be explained by the enhancement/reduction of hybridization between orbitals under strain. These results offer new perspectives to comprehend the appearance/disappearance of the excitons in monolayer transition metal dichalcogenide materials upon mechanical perturbation.
Many studies on phenotypic antimicrobial resistance (AMR) of bacteria from healthy populations are conducted on freeze-stored samples. However, the impact of this practice on phenotypic AMR is not known. We investigated the prevalence of phenotypic AMR in Escherichia coli from chicken (n = 10) and human (n = 11) faecal samples collected from healthy subjects, subject to freeze storage (−20 °C and −80 °C) for 1, 2, 3, and 6 months. We compared counts of E. coli and prevalence of phenotypic resistance against five antimicrobials commonly used in chicken farming (ciprofloxacin, enrofloxacin, doxycycline, gentamicin, and florfenicol) with samples processed within 24 h of collection. Prevalence of phenotypic AMR was estimated by performing differential counts on agar media with and without antimicrobials. At −20 °C, there was a considerable reduction in E. coli counts over time, and this reduction was greater for human samples (−0.630 log10 units per 100 days) compared with chicken samples (−0.178 log10 units per 100 days). For most antimicrobials, AMR prevalence estimates decreased in freeze-stored samples both in humans and chickens over time. Based on these results, we conclude that results on the prevalence of phenotypic AMR on samples from freeze-stored samples are unreliable, and only fresh samples should be used in such studies.
Background Rigid talipes equinovarus (TEV) is a complex foot deformity in which the foot is fixed in a plantarflexed, inverted, and adducted position. This pathology has the potential to severely limit basic life activities, which can be devastating for patients in developing countries. The objective of this study was to present the outcomes of patients with mature bones presenting with severe rigid TEV deformity who were operated on during a humanitarian mission to Vietnam using a single lateral approach and a simple and inexpensive fixation technique. Methods This is a retrospective analysis of prospectively collected data. We analyzed the outcomes of patients who underwent surgery for a severe rigid TEV that prevented them from walking minimal distances unaided. All feet were fixed in a non-plantigrade position. The surgeries were conducted as part of two International Extremity Project (IEP) missions in Can Tho, Vietnam (2013 and 2018). Pre- and post-operative AOFAS scores were compared using the paired sample t-test. Results We operated on 14 feet of 12 patients, 6 (50%) of whom were males, aged 34.42 ± 11.7 (range 12 to 58). Four patients were followed for three months, two patients were followed for 12 months, and eight patients were followed for three years. On the final follow-up visit of each patient, all 14 operated feet were plantigrade with good alignment, and patients reported an improvement in daily activity. After 3 years of follow-up, the mean AOFAS score of eight patients with available data improved by 42.88 ± 3.91 points (95% CI 39.61 to 46.14, P < 0.01). Our patients also reported an improvement in mobility. At the final follow-up examination, no recurrence of the deformity was observed in any of the patients. Conclusions Using low-technical surgical modalities, we were able to achieve plantigrade and walkable feet in patients with mature bones who had fixed rigid equinovarus. Level of evidence Level IV- Case Series.
Background γ-aminobutyric acid produced from lactic acid bacteria can be an ideal component in food products due to its health functional properties. Objective This study aimed to isolate lactic acid bacteria (LAB) with the capacity of producing γ-aminobutyric acid (GABA) and evaluated its antimicrobial activities and application of Nem Chua (the traditionally fermented meat product). Methods LAB strains from 7 types of Nem Chua products were isolated and evaluated for their GABA-producing and antibacterial capacities. The Nem Chua product was prepared from the selected GABA-producing LAB strain and evaluated for its GABA content, pH, and lactic acid levels. Results Six strains (CP2, HC2, LV2, TP1, VL1, and XP1) were isolated being capable of producing GABA (1.234 – 1.568 mg/ml) after 24 h of fermentation. Among them, the strain VL1 was found to produce the highest GABA content and induce the highest antimicrobial activity against Bacillus Subtilis (19.7 mm in zone inhibition diameter). Strain VL1 was identified as Lactobacillus Plantarum and was used for the production of Nem Chua, which was found to contain 1.103 mg/g of GABA and 22 mg/g of lactic acid Conclusion The result showed the high feasibility of using GABA-producing strain L. Plantarum VL1 to develop functional products due to its health-beneficial effects.
Despite the considerable amount of work which has been conducted into teachers’ needs for professional development (PD) in mainstream education, this topic has been received little attention in the field of English language teaching (ELT). This paper presents findings from a phenomenological study investigating the perceived needs for PD of Vietnamese tertiary English as a foreign language (EFL) lecturers. Grounded in andragogy theory, this study found that EFL lecturers expressed a strong need for content-focussed, on-going, collaborative and career-stage specific PD activities in the future. The findings from this study shed light on key issues for academic managers and PD planners to focus on when planning, organising and implementing PD activities. This study contributes to current literature related to tertiary EFL lecturers’ PD needs within the Vietnamese higher education context and may be applied to other international contexts.
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6,974 members
Dang Thi Hoang Oanh
  • Department of Aquatic Biology and Pathology
Lam Phuoc Thanh
  • Department of Animal Sciences
Phu Tran Minh
  • College of Aquaculture & Fisheries
Le Van Hoa
  • Department of Biochemistry & Plant Physiology Department
Giang Huynh Truong
  • College of Aquaculture & Fisheries
Campus II, 3/2 street, Ninh Kieu district, Cần Thơ, Vietnam
Head of institution
Prof. Dr. Ha Thanh Toan