Published: 2023-03-30

Molecular identification of Ralstonia pseudosolanacearum causing bacterial wilt in tomatoes from Da Nang by using Colony PCR

Nguyen Minh Ly, Toan Kieu Duc
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Ralstonia solanacearum species complex (RSSC) is the main pathogen causing bacterial wilt disease in tomatoes. This study applied the colony polymerase chain reaction (PCR) technique to rapidly screen and select RSSC strains from isolated bacteria of diseased tomatoes. This method directly used bacterial colonies on the Petri plate as templates to amplify with RSSC’s specific and multiplex primers. The results showed that the Vietnamese isolates were identified as R. pseudosolanacearum, phylotype I. Phylogenetic analysis of the 16S-23S rDNA sequencing also confirmed these results. Therefore, this is the first report to recognize R. pseudosolanacearum phylotype I as the cause of bacterial wilt disease in tomatoes from Danang.

Space Vector Modulation for Induction Motor on ARM-based Microcontroller

Ho Pham Thanh Tam, Thanh Hung Tran
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This article presents the review and the implementation of Space Vector Modulation (SVM) in a low-cost microcontroller-based motor drive system. The output three-phase voltages are obtained from a reference voltage vector in the polar coordinate system using the PWM technique; these voltages can reach up to the level of the DC voltage source (experimentally 16 VDC or practically 237 V with an inverter module). The article also provides a detailed presentation of the pre-calculations and the computations required for SVM on a STM32F1 ARM-based microcontroller. For achieving high frequency precision, a novel method for vector rotation based on the fixed-point arithmetic is proposed and tested. The experimental results highlight that the presented implementation including vector rotation can reach 1 Hz without significant error and it requires only 0.684 MIPS at 5 kHz computation rate for a 72 MIPS 32-bit microcontroller with single-cycle multiplication. The maximum instantaneous output phase-to-phase voltages could be as high as the DC voltage source.

Influence of internal curing on compressive strength and drying shrinkage of super-sulfated cement mortar

Tran Vu An, Nguyen Hoang Anh, Bui Le Anh Tuan
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The current study aims at assessing the effect of using cold-bonded fly ash based artificial lightweight aggregate (ALWA) as an internal curing (IC) agent on the compressive strength and drying shrinkage of a typical super-sulfated cement (SSC) produced with a mixture of 85% slag, 10% gypsum, and minor amount of 5% blended Portland cement (PCB). The ALWA was used as partial replacement of fine aggregate (FA) at values of 25, 50, 75, and 100 vol.%. Experimental results showed that the ALWA partially replacing FA in range of 25–100 vol.% significantly decreased both the unit weight and dried density of the fresh and hardened IC-SSC mortars at average values of 13.9% and 20.0%, when compared with the reference SSC mortar, respectively. The ALWA increment continuously reduced the compressive strengths of the hardened IC-SSC mortars. But, at 28 days of curing, the hardened IC-SSC mortar containing the ALWA amount partially replacing FA up to 50 vol.% showed compressive strength reaching 89.3%, and comparable or slightly lower drying shrinkage in comparison with the reference SSC mortar without the IC agent.

Evaluating household coal slag emissions in Binh Chanh District, Ho Chi Minh City, Viet Nam and recommended solutions

Tran Thi Thanh Ngoc, Thai Phuong Vu
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In Viet Nam, apart from coal-fired power plants, coal slag also emitted from households via coal burning activities. However, the quantity of slag emitted from households has been rarely determined, and most of it is not been well-treated. In addition, it is well-known that the untreated or mistreated coal slag can lead to severe impacts on both the environment and human health. Therefore, it is necessary to evaluate the emission of this slag, and thereafter to provide recommendations for improved management. In this study, the emission of household coal slag in Binh Chanh District of Ho Chi Minh City, Vietnam was investigated by undertaking a fact-finding survey coupled with GPS. Coal burning experiments were also performed for various fuels including large-sized honeycomb charcoal (3 kg/piece); small-sized honeycomb charcoal (1.7 kg/piece); charcoal (1 kg) and dried firewood with rice husk (1 kg) to estimate the quantity of household coal slag emissions slag, as well as to primarily examine the impact to the environment and human health. Results showed that the emissions of household coal slag in the study area was considerable, up to 146 tonnes per year,  almost 60% of which, was directly discharged into the environment. The burning coal for household purposes was found to dramatically change the quality of air with high concentration of pollutants including formaldehyde (HCHC), total volatile organic compound (TVOC), as well as particulate matters (PM2.5 and PM10) in exceedance of national standards which led to health effects. Finally, solutions for managing the slag were proposed.

Students’ perceptions of using note-taking in consecutive interpreting assignments

Phuong Hoang Yen, Lam Thi Cam Tu, Le Thanh Thao
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Note-taking is critical in helping interpreters memorize detailed information both quickly and accurately. Therefore, the present study was conducted as a questionnaire survey at a university in the Mekong Delta of Vietnam to investigate how students, specifically student interpreters, perceive note-taking in consecutive interpreting assignments. In detail, this study explores the students’ perceptions of the benefits and the challenges of using note-taking in consecutive interpreting assignments. The participants in this study comprised 160 students majoring in English Interpretation and Translation. Furthermore, they have taken consecutive interpreting courses and experienced taking notes in consecutive interpreting tasks. The findings of this study indicated that most students had good perceptions about note-taking used in consecutive interpretation and perceived its benefits and challenges. Moreover, some pedagogical implications for both students and teachers are made. Specifically, the study suggests that students should frequently practice it to acquire good note-taking skills. Teachers should make effective lecture designs to help students improve their note-taking skills and consecutive interpreting performance.

Evaluating different diets on the growth performance of mud crab (Scylla serrata)

Gabito Porfirio P., Baltar Christia C.
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The purpose of this study was to assess the potential of natural feeds for the sustainable grow-out aquaculture of mud crabs as an alternative to commercially available mud crab feeds. This study employed a completely randomized design that includes five  feed  treatments including trash fish, African land snail, horn snail, edible frog, and mud snail. There were three replicates for each treatment with three cages each located in a concrete tank with an area of 12m2. Each cage contained one lean crab. The crabs were fed twice a day, at 7 a.m. and 8 p.m. with an amount adjusted to 7% of the crab's body weight. After the first 21 days, all the crabs were harvested by draining out the tank water and the pincers of the crab were tied with a string to enable handling. The results showed that the highest growth performance in weight gain and condition factor was seen in African land snail feed with a feed conversion ratio of 1.38, indicating a high-quality feed. It also showed an impressive ROI of 96.8% which can be confirmed that this kind of feed might be a viable mud crab feed for both commercial scale and industry.

Investigating the leaching performance of ferric chloride solution for metallic alloys resulting from reduction smelting of spent lithium-ion batteries

Tran Thanh Tuan, Viet Nhan Hoa, Nguyen Thi Hong, Lee Man Seung
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Smelting reduction of spent lithium-ion batteries (LIBs) produces metallic alloys containing Co, Ni, Cu, Mn, and Fe. Finding suitable reagents in terms of efficiency, economics, and friendly environment for the dissolution of these metals from the alloys is very important for the recovery process of the metals. In this work, the employment of ferric chloride solution for the dissolution of the metals from the alloys was studied. The effect of parameters like FeCl3 concentration, temperature, time, and pulp density on the leaching efficiency of metals was investigated. Our results indicate that ferric ions in the leaching solutions act as oxidizing agents for the dissolution of the metals, while chloride anions as ligands for the formation of the complexes of the dissolved metal ions. The best conditions for the dissolution of full metals were 0.7 mol/L FeCl3, 12.5 g/L pulp density, 22oC, and 30 min. In comparison with HCl or H2SO4 leaching agents, ferric chloride shows some advantages like a decrease in the dosage of acids and oxidizing agents, fast reaction kinetics, and low energy consumption. With its advantages, ferric chloride solution is considered a potential leaching agent in the recovery process of valuable metals from spent LIBs.

Chemical composition and antibacterial property of Eclipta prostrata (L.) L.

Le Thi Bach, Trinh Minh Thanh Nam, Nguyen Trong Tuan, Hoang Trung Vinh, Le Tien Dung, Le Thi Thanh Xuan, Bui Thi Buu Hue
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Eclipta prostrata (L.) L. belonging to the Astearaceae family has been long used worldwide by various communities as a traditional medicine. We studied the antibacterial activity of different extracts from Eclipta prostrata (L.) L. against Aeromonas hydrophila, Aeromonas dhakensis, and Vibrio parahaemolyticus . The processing of this extract using repeated column and thin layer chromatographic techniques resulted in the isolation of three compounds including luteolin (1), kaempferol (2), and kaempferol-3-O-α-L-rhamnopyranoside (3), which were identified by NMR. Among them, kaempfreol-3-O-α-L-rhamnopyranoside was isolated for the first time and shows good antibacterial activity against Aeromonas hydrophila which is major pathogen for the aquaculture industry. The results demonstrate the beneficial effects of E. prostrata as an antimicrobial and bioactive compound for medicinal usages.  

Adsorption of Co(II) from the simulated solution by zeolite NaX derived from rice husk ash

Nguyen Thi Hong, Phan Thi Diem Trang, Tran Nguyen Phuong Lan, Luong Huynh Vu Thanh, Nguyen Dien Trung
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The adsorption of Co(II) from the simulated solution was investigated using zeolite NaX derived from rice husk ash as an alternative adsorbent. The adsorption behavior of Co(II) depended strongly on the equilibrium pH, Co (II) concentration, zeolite NaX dosage, and reaction time. The high adsorption efficiency of Co(II) by zeolite NaX was obtained under the conditions: pH 3.0, 100 mg/L of Co(II), 5 g/L of zeolite NaX, and a reaction time of 75 min. The loading behavior of Co(II) onto the zeolite NaX was well-fitted to the Freundlich adsorption isotherm and the Co(II) loading capacity by zeolite NaX was around 38 mg/g. The obtained results indicate that synthesized zeolite NaX from rice husk ash is a potential adsorbent to remove cobalt from waste solutions due to its high adsorption.

Identifying biofilm forming bacteria in cow milk in Mekong Delta, Viet Nam

Ngo Thanh Phong, Bui Huynh Lien, Pham Thi Binh Nguyen, Huynh Van Tien, Bui The Vinh
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Bacterial biofilms are agglomeration of bacterial cells, stuck to the material surfaces of material in wet environments and formed by a self-produced matrix. The formation of bacterial biofilms is a great risk for the milk processing industry, as the survival of many bacterial species in cow milk may lead to many problems such as microbial spoilage, deterioration in quality, and consumer health risks. This study aimed to identify biofilm formation bacteria from cow milk. The experiment included isolation; biofilm forming assay in 96-well microtiter plates and the identification of microbial isolates using classical and molecular biological methods. A total of 14 bacterial isolates from 10 cow milk samples were evaluated for their biofilm formatting ability. Among them, four isolates were identified as moderate and strong biofilm producers. These four isolates belong to the genera Serratia and Aeromonas. Out of the 4 isolates, Serratia marcescens VL41 was classed as a strong biofilm producer while Aeromonas veronii ST15, Aeromonas sp. ST17, Serratia marcescens VL13 were classed as moderate biofilm producers respectively. The findings of this study suggest that it is necessary to discover the contamination causes and prevention of genera Serratia, and Aeromonas into cow milk.

Isolation and identification of triterpenoid compounds from Couroupita guianensis Aubl.

Quoc Luan Ngo, Nguyen Phu Thach, Nguyen Van Minh Em, Nguyen Thi Ngoc Trinh, Phan Nhu Thao, Ngo Khac Khong Minh, Ngo Trong Nghia, Phan Nhat Minh, Nguyen Tan Phat
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In this report, the extracts from the fruit and leaves of Couroupita guianensis were isolated using chromatographic methods and investigated for chemical composition. Four triterpenoid compounds were isolated and identified as betulinic acid, oleanolic acid, β-amyrin and friedelin. Their chemical structures were interpreted based on modern spectra such as MS, NMR and compared with previously published spectral data.

The Object detection by the combination of generic roi extractor and dynamic R-CNN with side-aware boundary localization in aerial images

Bao Tran Nguyen, Tai Pham Tan, Doanh C. Bui, Nguyen D. Vo, Khang Nguyen
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Unmanned Aerial Vehicles (UAVs) have recently gained popularity due to their simplicity and effectiveness in traffic monitoring and potential for rapid delivery, and rescue support. Moreover, UAVs have been employed as a supporting machine in data collection for object detection tasks, in particular vehicle detection tasks in object recognition. Although vehicle identification is a tough problem, many of its challenges have recently been overcome by two-stage approaches such as Faster R-CNN, one of the most successful vehicle detectors. However, many critical problems still remain, such as partial occlusion, object truncation, object multi-angle rotation, etc. In this paper, we combine the Generic RoI Extractor (GroIE) method with Dynamic R-CNN and Side-aware Boundary Localization (SABL) for both testing and evaluation on a challenging dataset XDUAV. Overall, 4344 images in the XDUAV dataset, divided into 3 subsets: 3485 training images, 869 testing images and 869 validating images were used. These consisted of six object classes: 33841 “car”; 2690 “bus”; 2848 “truck”; 173 “tanker”; 6656 “motor” and 2024 “bicycle”. With the ResNet-101 backbone, our approach showed competitive results compared with the original GRoIE method, surpassed by 1.2% on mAP score and by about 2% on most classes AP scores, except for the class 'tanker'.

An Overview on Social Withdrawal-Hikikomori in Japan and Support in the Context of COVID-19 Pandemic

Nguyen Thi Phi
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The spread of the COVID-19 pandemic has affected every aspect of human life and lead many families to experience the pandemic as stressful. Due to Coronavirus lockdown, many people lost their livelihood and felt helpless, bored, or even depressed. The long lockdown might have led to social isolation and mental health problems, especially Hikikomori – a phenomenon of social withdrawal in Japan. Over 1 million Japanese who live as “Hikikomori” who had totally withdrawn from society, now face a dire situation, left alone and unable to cope. The government has supported them in many ways to bring them back to society. This support has played an important role in helping Hikikomori whose life is totally supported by their parents and relatives, to overcome the impacts of the crisis. However, factors contributing to Hikikomori’s reduced health and well-being should be investigated to find appropriate measures for the current situation.