Vietnam Journal of Science, Technology and Engineering

10-18

Authors: M. Peeraiah*, K. Nagamalleswara Rao, B. Balakrishna

Nanofluids are a type of emerging heat transfer fluid with great promise for thermal engineering due to its high heat transfer coefficients. Improving heat transmission remains an ongoing task in engineering fields as diverse as semiconductor technology and high-performance vehicles. This paper investigates and compares the jet impact heat transfer coefficient, thermal conductivity, and viscosity of nanofluids with those of a base fluid in an automobile radiator with nozzle plate spacing. Aluminium oxide (Al2O3) and deionised water were selected as the working fluids, and they were used in varying quantities ranging from 0 to 1 volume percent. The nanofluids were prepared using a two-step method with the aid of an ultrasonic homogeniser. The results reveal that the heat transfer coefficient increased by 11.68% at a nanofluid concentration of 1% when nanoparticles were suspended in the base fluid. Furthermore, a 45-49% improvement in the heat transfer coefficient was recorded using a nanoparticle volume concentration of 1% compared to the base fluid.

27-32

Authors: Hung Duc Nguyen*, Tan Quang Tu, Mau Hoang Chu

Saponins are naturally occurring compounds ubiquitously present in various organisms, predominantly in plants. They are noted for forming colloidal solutions in water, which foam on shaking and precipitate cholesterol. Several in vitro and in vivo tests on mixtures and individual saponins have revealed a broad spectrum of biological and pharmacological activities, including cancer-related activity, antiphlogistic and antiallergic, immunomodulating, antihepatotoxic, antiviral, hypoglycemic, antifungal and molluscicidal activities. The Dracaena genus is renowned for an abundance of steroidal saponins utilized in treating digestive and hematological disorders. Previous studies on this genus revealed the presence of steroidal saponins, some of which showed cytotoxic activities against cultured tumor cells and interesting biological activities. This study procured steroidal saponin from the foliage of D. dracoL. using various chromatographic techniques and 1D and 2D nuclear magnetic resonance (NMR) spectroscopic analysis. The structure was deduced as 26-O-β-D-glucopyranosyl-22-O-methylfurosta-5,25(27)-diene-1β,3β,22α,26-tetrol 1-O-{O-α-L-rhamnopyranosyl-(1→2)-α-L-arabinopyranosyl}; a compound previously isolated from the underground parts of Ruscusaculeatus in Japan. Future evaluation of the saponin’s biological activity is imperative to enhance chemotaxonomic data concerning the chemical composition and biological functionality of D. draco L. and, by extension, the Dracaena genus.

52-60

Authors: Bhim Kumar Dahal*, Jun Jie Zheng

This study evaluates the index, microstructural, and mechanical behaviour of cement-stabilised soft soil. The marine soil dredged from Hangzhou is taken for the study. Different percentages of ordinary Portland cement (OPC)by dry mass were added to the soils during reconstitution, i.e., 5, 10, 15, and 20%. The reconstituted samples were analysed in the laboratory to determine basic properties such as moisture content, void ratio, density, specific gravity, consistency limits, and particle size distribution. The microstructures of the reconstituted samples were also evaluated through scanning electron microscopy. Results inferred a significant impact on the physical properties of the soil. An increase in cement content increases the consistency limits. Additionally, the specific gravity, plasticity index, and density of the treated soil initially decreased but increased upon further addition of cement content. The microstructure of the soil transformed from a dispersed to a flocculated structure, with larger and denser particles. The change in microstructure was also evident in the particle size distribution, with an increase in cement content leading to larger size particles. Finally, the unconfined compression test conducted on the reconstituted soil indicates a substantial enhancement in strength with higher cement content and prolonged curing periods.

69-75

Authors: Thi-Hoan Luong, Huu-Khanh-Tan Tran, Woo-Jin Jung, Van-Viet Nguyen, Dang-Minh-Chanh Nguyen*

In this study, the authors aim to determine the chemical compositions of the essential oil from Ocimum tenuiflorumleaves and to evaluate its antioxidant and antifungal activities. The essential oil used in this research, extracted by hydrodistillation, was chemically profiled using gas chromatography/mass spectrometry (GC/MS) analysis. Methyl eugenol (46.07%), caryophyllene (15.65%), eugenol (11.83%), β-elemene (4.33%), β-copaene (4.18%), caryophyllene oxide (3.18%), and α-copaene (1.95%) were identified as major components of the essential oil. The results indicated that the essential oil of O. tenuiflorum leaves possessed relatively high 2,2-diphenyl-2-picrylhydrazyl (DPPH) and 2,2’-azinobis-(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) radical scavenging activities with IC50 values of 53.5 and 55.1 μg/ml, respectively, compared with 67.2 and 63.2 μg/ml, respectively, for the positive control. The reducing powers of O. tenuiflorum essential oil and butylated hydroxytoluene (BHT) at a concentration of 200 μg/ml were 0.95 and 0.73, respectively. Additionally, the essential oil of O. tenuiflorum at a concentration of 200 μg/ml strongly inhibited the mycelial growth of Rhizoctonia solani.

82-88

Authors: Manh Cuong Nguyen*, Thi Thuy Hang Le, Thanh Nam Do, Thai Son Pham, Hoang Long Trinh, Thi Bich Thuy Phung, Yen Thi Hoang, Quang Khai Tran

Influenza, a historical and contemporary public health challenge, is an acute respiratory infection caused mainly by influenza A or B viruses. This descriptive case series describes 194 children treated for seasonal influenza at the Department of Pediatrics, 103 Military Hospital, Vietnam Military Medical University, from May 2022 to May 2023. Influenza primarily occurred during winter and early spring, peaking in December and January, 57.2% were aged 12-60 months, boys. Vaccination coverage was limited (36.3%), especially post-COVID-19. Complications were seen in 75.3% of the cases, including febrile seizures (42.3%), bronchopneumonia (40.2%), respiratory failure (8.2%), acute myocarditis, influenza-associated encephalopathy, and septic shock. The study reveals bacterial coinfections, affected 20% of the cases, mainly by Streptococcus pneumoniae and S. aureus, and atypical bacteria Mycoplasma pneumoniae. Non-vaccinated children faced significantly higher risks of complications, oseltamivir within 48 hours reducing the risks of complications. Influenza predominantly affects 12-60 month-olds, males, and peaks annually in winter. Severe conditions stem from bacterial coinfections, emphasizing the importance of vaccination and prompt antiviral treatment to mitigate complications. The study highlights a critical need for increased vaccination, especially in the post-COVID-19 era, to manage influenza in children effectively.

101-106

Authors: Nguyen Quang Huy*, Pham Quynh Trang, Nguyen Thi Loi

This study aimed to investigate the occurrence of potential pathogenic bacteria from surface water samples collected at 30 stations along Ha Long Bay, Vietnam. Among 116 bacterial isolates identified, the composition analysis indicated 24 distinct bacterial genera, with Vibrio (29.3%), Pseudomonas (23.3%), Staphylococcus (8.6%), and Bacillus (6.0%) being the most dominant. The taxonomic analysis revealed 61/116 (52.6%) isolates as potential pathogens (risk group 2) belonging to 21 bacterial species. Potential pathogens were detected in 28/30 (93.3%) sampling stations, with the most common pathogens including Vibrio alginolyticus (n=25), Vibrioparahaemolyticus (n=5),Enterobacter cloacae (n=3), Pseudomonas mendocina (n=3), Aeromonas hydrophila (n=2), Enterobacter asburiae (n=2), Klebsiella oxytoca (n=2), Bacillus cereus (n=2),and Staphylococcus haemolyticus (n=2). The selected pathogens were highly resistant to Amoxicillin (100%), Piperacillin (100%), Amoxicillin + Clavulanate (85.7%), Ticarcillin (71.4%), Cefoxitin (54.4%), Kanamycin (50%), and Fosfomycin (50%), and less resistant to Trimethoprim + sulfamethoxazole, Fusidic Acid, Tetracycline, Erythromycin, Pristinamycin, Dalacin, and Rifampicin (<25%), and susceptible to the remaining antibiotics. Notably, 12/23 (52.2%) isolates were resistant to at least three antibiotics and were multidrug-resistant bacteria. Our findings underline that the occurrence of pathogenic antibiotic-resistant bacteria in the marine environment of Ha Long Bay presents a potential threat to human health. Further genomic surveillance studies are necessary to manage and control the emergence and spread of pathogenic-resistant bacteria in this area.

114-120

Authors: Muslim Babatunde Aminu*, Femi Ologunaye

We present the results of a multi-frequency ground-penetrating radar (GPR) survey over a university road in south-western Nigeria that has experienced persistent failures. The goal was to evaluate causes of failure to aid remediation efforts. Data was collected concurrently at 250, 500, and 1000 MHz using a UTSI electronic trivue system. Data were processed and interpreted using Reflex-Win. Visual observations of major features apparent on the road surface including failed sections were noted. Imaged features included possible bases of the surface course, base course and sub-base, subsurface projections of an outcropping and buried basement rocks, three deeply cut and back-filled sections that lie beneath sections of the road that have experienced persistent failure, and the ringing effects and rebar-associated reflection hyperbolae of two reinforced concrete drains. Indications of preferential wetting of the shallow subsurface beneath much of the failed sections suggest that failure is due to excessive moisture content in these sections. These failed sections generally correspond to regions of deep cut and backfill, and regions cut and filled for the construction of reinforced concrete drains. Apparently, the backfills at these locations have failed to prevent water influx into the subsurface and more effective remediation measures need to be deployed.

10-15

Authors: Nguyen Tri Tuan*, Tong Thi Hao Tam, Nguyen Tu, Do Quang Trung, Nguyen Van Du, Tran Minh Tien, Vu Thi Hang, Nguyen Trong Tuan, Nguyen Van Quang, Manh Trung Tran

In this study, we successfully synthesized europium-doped TiO2 (TiO2:Eu3+) nanomaterials (NMs) with crystalline sizes ranging from 6.5 to 71.7 nm through a sol-gel method. Analysis of X-ray diffraction (XRD) patterns and ultraviolet-visible (UV-Vis) spectra indicates that the substitution of smaller-sized Ti4+ ions (0.745 Å) by larger-sized Eu3+ ions (0.947 Å) was more efficient at higher doping concentrations and annealing temperatures. Photoluminescence (PL) and photoluminescence excitation (PLE) spectra of the synthesized TiO2:7%Eu3+NMs exhibit a strong red emission band peaking at 613 nm and remarkable absorption in the blue light region centered at 463 nm, making them suitable for use in white light-emitting diode (WLED) applications. Our findings reveal that both annealing temperature and doping concentration significantly influence the structure and properties of these materials. Besides, the research team has seen, under the experimental conditions, the TiO2:7%Eu3+ sample annealed at 800°C exhibits the highest PL intensity. These results underscore the potential of the synthesized TiO2:Eu3+ NMs as red-emitting materials for WLED applications.

24-33

Authors: Thi Lan Phung*, Thi Kim Giang Nguyen, Phuong Hien Ho, Thanh Nga Pham

In this study, cellulose was produced by activating peanut shells with 5% NaOH as an alkaline agent and bleaching with 5 wt.% H2O2. Before being modified with chitosan, the cellulose was slightly oxidized with ammonium persulfate to introduce carboxyl groups. The equilibrium and kinetics of nickel adsorption on the as-prepared material were investigated. Langmuir, Freundlich, and Temkin isotherm models were used to describe the equilibrium isotherms. The Langmuir and Temkin adsorption isotherms were better fits to the equilibrium data than the Freundlich equation. The Langmuir monolayer adsorption capacity of nickel ions on cellulose from peanut shells modified with chitosan was found to be 25.70 mg/g. The Temkin adsorption constant was calculated as 0.45 kJ/mol. Therefore, the interaction between nickel ions and the surface of the as-prepared material are assumed to be weak. Kinetic data were evaluated by pseudo-first-order and pseudo-second-order models, and rate constants were determined. Simulations demonstrated that the pseudo-second-order equation could adequately describe the adsorption of nickel ions.

46-52

Authors: Dang-Minh-Chanh Nguyen*, Thi-Hoan Luong, Van-Viet Nguyen, Woo-Jin Jung

In the present study, we investigated the antifungal activity of a methanolic extract of Glycyrrhiza uralensisFisch. root, which inhibited the growth of the plant pathogens Fusarium oxysporum and Phytophthora capsici. The EC50 values of the G. uralensis Fisch. extract three, six, and nine days after treatment were 113.4, 150.6, and 191.4 μg/ml for F. oxysporum and 84.7, 148.6, and 190.1 μg/ml for P. capsici, respectively, and the antifungal activity exhibited a dose-dependent response. The MIC value of G. uralensis Fisch. extract was found to be 100, 200, and 400 μg/ml at three, six, and nine days after treatment for F. oxysporum. In contrast, for P. capsici, the MIC value was 50, 100, and 100 μg/ml at three, six, and nine days after treatment. After three days of incubation with 400 μg/ml G. uralensis Fisch. extract, the hyphae of F. oxysporum exhibited abnormalities and atrophy, leading to mycelial collapse. In contrast, the hyphae of P. capsici displayed swelling with increased branching. These results furnish valuable insights into the antifungal metabolites present in G. uralensis Fisch. extract, contributing to the development of environmentally friendly products aimed at controlling the growth of pathogenic fungi.

59-76

Authors: Long Hoang*, Mai T.T. Nguyen, Doan. N.Q. Nguyen, Kim Hoang, Clair Hershey, Reinhardt Howeler

Vietnamese cassava varieties constitute the fundamental and pivotal element in the sustainable development programme for cassava. This article aims to encapsulate the advancements made over nearly five decades in breeding and enhancing Vietnamese cassava varieties. It delineates the suitable cassava variety structures for each period and ecological region. The selection of cassava varieties exhibiting high starch yield and disease resistance, coupled with the establishment of a suitable and efficient cassava cultivation model, exemplified by 10T for Vietnamese cassava varieties KM568, KM539, KM537, KM569, and KM94, stands as a cornerstone for sustaining cassava development over the years. Presently, we advocate for farmers to cultivate promising cassava varieties such as KM568 or KM539 (an enhanced version of the International Center for Tropical Agriculture (CIAT) cassava variety C39, refined through multiple breeding cycles from 2004 onwards), KM537, KM569, or HN1 (originally known as TMEB419), alongside popular cassava varieties: KM440, KM419, KM94, KM7, STB1, KM414, KM98-7, KM140, KM98-5, KM98-1. We have conducted Distinctness, Uniformity, and Stability (DUS) and Value for Cultivation and Use (VCU) tests, showcasing outstanding cassava varieties in large-scale farming, thereby providing compelling evidence for the prudent conservation and sustainable development of cassava. Vietnamese cassava progression (1975 to date) has traversed six stages, with five waves of restructuring cassava varieties, aligning with target orientations, farming conditions, and market demands, culminating in 16 popular cassava varieties and four promising cassava varieties KM568, KM539, KM537, and KM569.

84-89

Authors: Dinh Toi Chu, Hue Vu Thi*, Ngoc Hoan Le

The RNeasy Mini Kit and the TRI Reagent protocol are commonly employed techniques for extracting total RNA and are widely utilised in research pertaining to the expression of adipose biomarkers. This study was undertaken to establish and determine an appropriate method for isolating RNA from frozen adipose tissue, with the objective of analysing adipose biomarkers. Total RNA was extracted from frozen white adipose tissues of mice (-80oC) using both the RNeasy Mini Kit and the TRI Reagent protocol. The concentration and purity of the RNA were assessed using NanoDrop. One-step RT-qPCR was employed to quantify the mRNA expression levels of three adipose biomarkers: MEST, SFRP5, and SCD1. The results of this investigation indicated that the RNeasy Mini Kit yielded a higher RNA concentration when compared to the TRI Reagent method. Furthermore, the RNeasy Mini Kit provided RNA samples with superior purity, as evidenced by a higher 260/230 ratio. Although RNA extracted using the TRI Reagent exhibited slightly elevated mRNA expression levels for the three biomarkers, these differences did not reach statistical significance. In summary, both methods are suitable for total RNA extraction, but the RNeasy Mini Kit is recommended for obtaining higher RNA concentration and purity. The choice of method should be contingent upon the intended downstream application of the RNA.

96-103

Authors: Van-Hoai Bui, Hong-Tham N. Vo, Thanh-Tuan Duong, Se-Kwon Kim, Dai-Nghiep Ngo*

The aim of the present study is to investigate the anti-inflammatory effect of gallic acid grafted onto COS chains (GA-COS), focusing on the reduction of nitric oxide production, downregulation of inflammatory signals such as inducible nitric oxide synthase (iNOS), gene expression of cytokines such as TNF-α, IL-1β, IL-6, and nuclear factor kappa B (NF-κB) signalling, including the p50 and p65 subunits. The anti-inflammatory effect is mediated through the reduction of nitric oxide production and downregulation of inflammatory proteins such as inducible nitric oxide synthase (iNOS), gene expression of cytokines like TNF-α, IL-1β, IL-6, and nuclear factor kappa B (NF-κB) signalling, including the p50 and p65 subunits. Target proteins were identified by western blot analysis with specific monoclonal antibodies. The levels of gene expression were determined by the RT-PCR method. The results demonstrate that GA-COS effectively reduces nitric oxide generation and downregulates iNOS protein and cytokine expression and NF-κB signalling in lipopolysaccharide (LPS) -induced RAW 264.7 cells. GA-COS exhibits significantly enhanced anti-inflammatory activity compared to the free chitooligosaccharide chain. This study lays the groundwork for future research to demonstrate that GA-COS holds significant potential as a novel compound for the prevention of inflammatory diseases.

111-119

Authors: Minh Hieu Vu, Doan Hong Ngoc Tran, Minh-Anh Dang-Trinh, Huynh Chan Khon*

The Coronavirus (SARS-CoV-2) is an enveloped RNA virus that caused a dangerous COVID-19 pandemic following an outbreak in Wuhan, China in 2019. In response to the pandemic, the development of lateral flow assays (LFAs) has been crucial for the detection of viruses, commonly targeting the spike (S) or nucleocapsid (N) protein in nasopharyngeal swab (NS) specimens. COVID-19, caused by the SARS-CoV-2 virus, predominantly manifests as a respiratory tract infection-like illness, characterized by symptoms such as fever, dry cough, upper airway congestion, runny nose, sore throat, myalgia, headache, and exhaustion. This study presents the development of an LFA targeting the N protein to detect the coronavirus in saliva specimens, using a sandwich format. The use of 80 nm gold nanoparticles (AuNPs) has been investigated, and the application of horseradish peroxidase (HRP) and TMB substrate has been employed to enhance the limit of detection (LOD). The results demonstrate a significant 200-fold improvement in LOD, from 10 to 50 pg/ml, for N protein spiked in saliva samples after the application of HRP-TMB. This finding highlights an important advancement towards the utilization of saliva samples in diagnostic applications.

11-13

Authors: Tuan Hoang Ho, Tung Thanh Nguyen, Tran Hoang Bao Ngo, Nam Thanh Son Phan*

Using amino acids for synthesis of heterocycles is a synthetically promising field. However, developing the practical methods for transformations of amino acids into heterocycles is still challenging. Given that alpha amino acids are abundant or easily prepared, herein we report a method for annulation of benzylic C-H bonds in derivatives of 2-phenylglycine with 1-(2-nitroaryl)pyrroles. The reactions proceeded well in the presence of iron(III) acetylacetonate catalyst and potassium carbonate base. Scope of pyrrolo[1,2-a]quinoxalines was studied. Regardless of electronic properties of substituents, the pyrrolo[1,2-a]quinoxaline de-rivatives were successfully isolated, as yields varied from 42% to 52%. Pyrrolo[1,2-a]quinoxalines substituted with heterocycles at C4 positions as pyridine and thiophene were competent substrates. Reaction mechanism was proposed to start with a decar-boxylative/deaminative sequence of 2-phenylglycine to afford benzaldehyde. The iron catalyst was presumed to facilitate the re-duction of 1-(2-nitroaryl)pyrroles to furnish the corresponding aniline. Imine condensation followed by cyclisation and oxidation would yield the pyrrolo[1,2-a]quinoxaline. Our method would offer a convenient tactic to transform abundant alpha amino acids into synthetically useful heterocycles.

25-28

Authors: Hoai Nam Quach, Dinh Hao Duong, Thanh Nhut Pham, Huu Huy Ho, Hong Chuong Pham, Van Hao Pham, Hung Tra Tran*

Copper-aluminum hybrid connectors play a crucial role in electric vehicles, but welding these metals together poses a significant challenge due to their distinct physical and mechanical properties. Friction stir welding, a solid-state welding technique, proves to be suitable for joining dissimilar metals. In this study, friction stir welding was employed to create a joint between pure copper 1100 and aluminum 1050 plates, each with a thickness of 5 mm. The fabricated results showed that a significant amount of copper was dispersed into the aluminum side to establish the bonding. The bonding strength was evaluated through tensile testing, while the macrostructure and fracture paths of the joints were monitored using an optical microscope. Despite efforts, eliminating defects in the joint proved challenging, with most defects attributed to vacancies. Increasing the tool rotation speed resulted in greater mixing intensity between the aluminum and copper. The interface between the copper and aluminum was found to be prone to crack propagation. The tensile strength of the joint improved with higher tool rotation, reaching up to 88 MPa. For further analysis, stress within the joint under tensile loading was simulated.

36-41

Authors: S. Panimalar, P. Kumaresan, S. Nithiyanantham*, K. Selva Sambath Kumar, R. Mohan

Pure thiourea barium chloride (TBC) crystals were synthesised using a slow cooling rate (0.05°C/day) and gradual evaporation from an aqueous solution. The growth process occurred over more than 19 days at a temperature of 39°C. Natural bond orbital (NBO) analysis has proven beneficial for studying charge transfer and conjugative interactions in molecular systems. Moreover, it sheds light on intermolecular bonding, and the interactions between these bonds have implications for optical applications. Additionally, the charge transfer interactions within the molecule that influence its catalytic activity can be elucidated by a lower HOMO and LUMO energy gap. This energy difference can be an indicator of a compound’s excitability; the more readily a compound can be excited, the narrower the energy gap. The energy gap might be significantly affected by the influence of thermal energy. The non-linear optical (NLO) efficiency of methyl orange-doped (MOD) TBC crystals was contrasted with that of the pure form, and the doped version exhibited greater efficiency, particularly for high-frequency applications.

48-53

Authors: Thi Loan Pham*, Duy Thanh Trinh, Thi Hoai Thu Nguyen, Trong Quang Do, Phan Anh Nguyen

Sustainability in building construction is an inevitable aspect of future construction projects. The justification of sustainability is highly appreciated by comparing 3D concrete printing technology with conventional construction. However, the 3D printing concrete system has limitations and challenges in industrial applications. The reason is that this process was initially used in small non-structural applications and is now being adopted for large-scale structures. Thanks to concrete printing machines, a wide variety of web frames are also available - something completely impossible to achieve using traditional formwork for pouring concrete. In this study, the girder web is designed in the style of truss beams. Three wide beams with different amounts of polypropylene (PP) fibre were printed, and 3-point loading tests were conducted. The failure mode, load-bearing capacity, and deflection were reported in this study. According to the results, applying concrete printing technology in civil and industrial construction is entirely feasible. The printing process successfully produced models with a nozzle diameter of 22 mm and layer height of 10 mm, ensuring sufficient adhesion force between the printing layers. Using a PP fibre content of about 0.25% yielded the best results in terms of concrete compressive strength and beams’ flexural strength, while a PP fibre content of about 1.00% tended to increase the ductility of the member. Although the failure mode is brittle, the beams exhibited deflection before fracture far beyond the allowable deflection value of a flexural member. Therefore, the application of printed components to construction is feasible.

62-70

Authors: Anh Mai Que, Tuan Ngan Tang, Tam Phan Thi Thanh, Thanh Tu Duong, Thanh Binh Vu, Van Khiem Nguyen, Hoan Ngoc Doan, Hiep Thi Nguyen*

In the management of burn wounds, antimicrobial and wound healing properties are crucial. In this study, we prepared a three-layer electrospun poly(ε-caprolactone) (PCL) membrane for burn wound dressing. The hydrophobic electrospun PCL layer, embedded with silver nanoparticles (SNPs) (PCL-Ag), was coated with another layer of electrospun plasma-treated PCL-Ag to enhance the wettability of the membrane. This enhancement was to facilitate the absorption of the hydrophilic chitosan oligomer (COS) - the third layer of the dressing. The resultant membranes were characterised and tested for different properties to demonstrate their applicability as wound dressing materials. The combination of COS and SNPs of the fabricated membrane supports the healing process and reduces burn severity due to the healing capacity of COS and the antibacterial activity of SNPs, without compromising mechanical strength. We conducted several in vitro and in vivo experiments to evaluate its applicability for burn wound healing. The PCL-Ag/COS sample demonstrated outstanding in vitro biocompatibility and excellent antibacterial activity against Staphylococcus aureus strains. We used the membrane to treat burns on rabbits in the laboratory over 30 days, and consistently observed positive outcomes. This research offers insights into the development of bioactive dressings for wound healing and opens up opportunities for practical applications of COS-incorporated materials.

77-83

Authors: Cong Vinh Kieu, Ho Le Thi*

The Thap Muoi district in Dong Thap province, Vietnam, is renowned as the largest rice producer, cultivating 112,762 hectares and specialising in three rice crops per year, with some areas achieving 3.5 annual crops. However, changing farming practices, low-quality rice seeds, and mechanisation have led to the emergence and spread of weedy rice (Oryza spp.) in Thap Muoi and the broader Mekong delta. This comprehensive assessment of weedy rice outbreak risks in Thap Muoi provides a vital foundation for effective management strategies to prevent its spread in the Mekong delta. Sixty questionnaires were collected from rice-farming households. Approximately 80% of farmers reported the appearance of weedy rice approximately five years ago. Alarmingly, 95% of surveyed farmers (57 individuals) reported weedy rice infestations, with 40% of them encountering infection levels ranging from 11 to 20 plants/m2. To distinguish weedy rice from cultivated varieties, seven distinct types were identified based on various morphological characteristics, including growth time, leaf blade structure, plant height, leaf/stem colour and shape, grain beard/tail, seed/husk colour, grain length, ripening time, and seed dispersal potential. However, all seven weedy rice varieties exhibited short growth cycles and the capacity to produce seeds, posing significant challenges to rice production management in Thap Muoi. This research underscores the critical importance of assessing weedy rice outbreak risks in Thap Muoi and understanding its morphology and prevalence. This understanding is essential for developing effective preventive measures to mitigate the threat of weedy rice outbreaks across the entire Mekong delta in Vietnam.

94-100

Authors: Pham Thi Mien*, Dao Viet Ha, Cornelis Verduyn

Docosahexaenoic acid, or Docosahexaenoic acid (DHA), plays a pivotal role in biological functions and is beneficial for both humans and animals. Traditionally, DHA is sourced from fish and fish oil. Due to the disadvantages associated with these sources, such as marine pollution and variable composition, there is a pressing need to explore alternative, reliable sources for DHA. Aurantiochytrium sp. has been identified as a promising candidate for DHA production. The primary aim of this study was to cultivate three strains in previously published media and, subsequently, to develop defined or semi-defined media for Aurantiochytrium sp.. These strains were grown in the selected media, and the dry weight of the cells was measured. Total fatty acids were extracted and analysed using gas chromatography. All three strains demonstrated satisfactory growth in media that incorporated glucose as a carbon source and monosodium glutamate as a nitrogen source. Strain B072 achieved the highest DHA concentration, with a peak of 5.0 g/l, and could accumulate lipids up to 57.57% (w/w). The DHA content in the biomass was 21.43% (w/w), with a biomass yield of 23.35 g/l. Vitamins and trace elements positively influenced the growth and DHA production of Aurantiochytrium sp.. Furthermore, strain B072 efficiently utilised ammonium for growth and fatty acid production.

8-13

Authors: Nhu Cuong Nguyen, Bao Anh Hoang, Trung Kien Do, Thanh Tung Bui, Duc Trinh Chu, Quang Loc Do*

A passive wireless sensor system integrated with capacitive fluidic flow detection is proposed and developed based on the printed circuit board (PCB) technique. The capacitive sensing structure consists of PCB-based electrodes enclosing an insulating pipe that contains the fluidic flow of interest. The conductivity of the fluidic flow and the appearance of foreign objects within the flow can be determined by analysing the resonant frequency of the detection path in the proposed system. Experimental results demonstrate that the resonant frequency increases according to the increase in electrical conductivity of the fluidic flow. In ad-dition, the sensing performance is also confirmed by the detection of sizes and electrical conductivities of NaCl droplets passing through the detection zone. Furthermore, this work indirectly verifies the effectiveness and feasibility of the integration of passive wireless sensing technique into the fluidic flow detector by using the PCB fabrication technique and demonstrates great potential for use in various applications in biomedical and chemical fields, especially in biomedical applications.

21-26

Authors: Trung Thanh Nguyen*

The durability of an acrylic-melamine (AC-ML) based varnish containing Tinuvin 292 when exposed to 100 cycles of accelerated exposure testing in fluorescent UV and condensation was investigated. Fourier-transform infrared (FT-IR) spectroscopy, thermal gravimetric analysis (TGA), and scanning electron microscope (SEM) were used to evaluate the changes between the initial and aged coatings. The obtained results showed that gloss loss, adhesion, flexibility, impact resistance, and relative hardness of the AC-ML varnish were enhanced with 2.5 wt.% of Tinuvin 292. FT-IR spectrums of the initial and aged samples without Tinuvin 292 illustrated strong changes in intensity of CH2 and C=O (ester) groups. AC-ML varnish with 2.5 wt.% of Tinuvin 292 exhibited changes in the peaks of the CH2 and ester groups after accelerated exposure testing. SEM images showed that the surface of the aged AC-ML varnish without Tinuvin 292 was rougher than that of the coating with Tinuvin 292. TGA results also showed that 2.5 wt.% of Tinuvin 292 had improved thermal oxidation stability of the AC-ML based varnish.

32-38

Authors: Phan Thi Tuyet Mai*, Nguyen Hai Linh, To Phuong Linh, Vu Tien Manh, Ngo Hong Anh Thu, Pham Ngoc Lan, Luu Thi Hue

In this study, cellulose and hemicellulose were successfully extracted from pineapple leaf waste at yields of 58.8 and 16.1% by dried weight, respectively. Carboxymethyl cellulose (CMC) was synthesised from pineapple leaf cellulose by an esterification process using sodium hydroxide (NaOH) and monochloroacetic acid (MCA) with isopropanol as the supporting medium. Preparation of CMC was investigated by varying three free factors, namely, NaOH concentration, MCA dose, and cellulose size. The carboxymethylation process was optimised to produce CMC with differing degrees of substitution (DS). The highest DS of CMC (0.86) was obtained with 15% (w/v) NaOH solution, 0.6 g of MCA/g cellulose, and 50 μm cellulose. The obtained CMC were characterised by FTIR spectroscopy, SEM images and XRD diffractions. Moreover, the thickening performance of obtained CMC was also determined. The influence of the CMC’s molecular weight and degree of substitution on the viscosity of 1% (w/v) aqueous solution was tested. The experimental results suggest that the viscosity of the solution increases with increasing molecular weight and degree of substitution of CMC.

44-49

Authors: Thi Hai Yen Pham*, Thi Kim Ngan Nguyen, Thi Thu Hien Chu, Thi Thu Ha Vu, Quoc Hung Le

This study investigates the modification of pencil lead graphite electrodes with polyglutamic acid using an effective and fast static method to develop a sensor for the detection of enrofloxacin (ENR). The successful fabrication of pGA on the electrode surface was confirmed by scanning electron microscopy, energy dispersive X-ray analysis, and Fourier-transform infrared spectroscopy. The conditions of electrochemical modification, including the applied potentials and number of cycles in the potentiostatic process, were systematically investigated to determine their effects on the ENR electrochemical response. The pH of the electrolyte media was also explored to elucidate the electrochemical reaction mechanism of ENR. The developed electrochemical sensor was evaluated using square wave stripping voltammetry for ENR detection. Under optimal conditions, the sensor demonstrated good reproducibility with a relative standard deviation of 4.3% (from five measurements) for ENR signal detection. A linear relationship between ENR concentration and its peak current was observed in the concentration range of 0.1 to 5 μM, with a high correlation coefficient of 0.9988. The limit of detection for ENR using the sensor was 0.12 μM. Our findings provide valuable insights into the design and optimisation of pencil lead graphite electrode-based sensors for ENR detection in aqueous media.

59-65

Authors: Florieza Mangubat*, Cerela Looc, Fretzel Mad

Calcium, obtained from various sources, is essential to fulfil the dietary requirements of birds. Oyster shells are excellent sources of calcium and are widely used in bird diets. Calcium is a critical factor in eggshell deterioration, affecting its absorption. Consequently, this study aimed to determine the combined effects of powdered oyster shell and lemongrass on the growth, development, and egg quality of birds, specifically using 5, 10, and 15 grams of oyster shell powder as a calcium source. A completely randomised design was used to assess the efficacy of varying amounts of powdered oyster shell. Results revealed that there was no significant change in growth development at different inclusion levels of oyster shell powder and lemongrass solution. However, egg quality exhibited a significant variance at different inclusion levels of oyster shell powder. Similarly, lemongrass solution as a supplement for laying quails demonstrated a significant difference. Therefore, supplementing the calcium source with a blend of 15 g of oyster shell powder and 300 ml lemongrass solution enhanced egg performance and eggshell quality of laying quail by 5%.

75-79

Authors: Do Thi Thuy Nga*, Nguyen Manh Cuong, Phung Thi Bich Thuy, Tran Minh Dien

A prospective, descriptive study was conducted on 382 pediatric patients diagnosed with pertussis at Vietnam National Children’s Hospital over a two-year period, from January 1st, 2019, to December 31st, 2020. Of all patients participating in this study, children with severe conditions accounted for 30.1% (115/382). Several factors were found to be associated with the risk of this condition with odds ratios (OR) and 95% confidence intervals (CI), including a decrease in the duration of the onset phase by 5 days [OR 1.53, 95% CI: 1.002-2.34], fever [2.49, 1.18-5.24], cyanosis [9.59, 2.9-31.7], pneumonia [14.45, 6.06-34.5], pulmonary hypertension [4.15, 1.02-16.83], an increase of 10 g/l in white blood cell (WBC) count in the full blood count (FBC) test [1.39, 1.05-1.84], a 5-cycle reduction in Cycle threshold (Ct) value in the pertussis real-time PCR test [1.36, 1.01-1.84], and superinfection [3.94, 1.84-8.48 times]. A WBC count in FBC of ≥30 g/l could be used as a prognostic factor for the risk of severe illness condition (sensitivity 46.1%, specificity 90.6%), the requirement for mechanical ventilation (sensitivity 57.1%, specificity 88.5%), and mortality (sensitivity 100%, specificity 91%).

85-90

Authors: Bui Thanh Tung*, Pham Thi Kim Dung, Nguyen Nhu Son, Nguyen Bao Kim, Nguyen Hai Ha, Nguyen Thanh Tra

The epidermal growth factor receptor (EGFR) belongs to the HER/erbB receptor tyrosine kinase (RTK) family, serving as a crucial target for cancer treatment. Anti-EGFR drugs, used as a primary treatment for patients with advanced EGFR gene mutations such as T790M, C797S, and L858R, have shown greater efficacy and safety compared to standard chemotherapy. This study aimed to screen alkaloid compounds with anticancer activity, extracted from the Selleckchem database that inhibit EGFR enzyme activity. The structure of the EGFR receptor was retrieved from the Protein Data Bank, whilst compounds were gathered from the alkaloids library within the Selleckchem database, with their structures downloaded from the PubChem database. Molecular docking was performed using Autodock Vina software. Lipinski’s rule of five was employed to distinguish between compounds with drug-like and non-drug-like properties. The pharmacokinetic parameters of potential compounds were evaluated using the pkCSM tool. Our research indicates that amongst the screened alkaloids, four compounds - peiminine, sanguinarine chloride, dauricine, and irinotecan - are the most promising inhibitors of the EGFR receptor for the treatment of lung cancer. These compounds exhibit high binding affinity for the active sites of EGFR, thus inhibiting its activity. All aforementioned compounds adhere to Lipinski’s rule and possess pharmacokinetic properties (absorption, distribution, metabolism, excretion, and toxicity - ADMET) that render them suitable for development into drugs.

10-14

Authors: Cuong Huynh Le Huy*

This study presents synthesis results of catalysts made of perovskite-like oxide La2-xSrxCuO4 (x=0.0, 0.5, 1.0) using the citrate method and crystallisation at 800°C. The structure of the catalysts was characterised by X-ray diffraction (XRD). The perovskite-like oxide catalyst activity was enhanced with gold (Au) and platinum (Pt). Au was mounted on the perovskite-like oxide catalysts by the sol-gel method. The activity of the perovskite-like oxide La2-xSrxCuO4 (x=0.0, 0.5, 1.0) and the perovskite catalyst LaMnO3/LaCuO3 was evaluated by complete oxidation of volatile hydrocarbons (HCs) in a mixture of toluene and methyl ethyl ketone (MEK) and carbon monoxide (CO) in a microflow analysis system combined with gas chromatography. The results showed that the light-off temperature (the 50% conversion temperature of the catalysts) of the Pt, Au/perovskite catalyst samples decreased significantly. The light-off temperature of the Au/LaSrCuO4 Au nanoparticle catalysts in the complete CO oxidation reaction reached a temperature of 150°C, lower than the Pt/LaSrCuO4 catalyst (170°C), allowing replacement of previous Pt catalysts with Au nanoparticle catalysts. The LaSrCuO4 catalyst had better oxidising activities than the La2CuO4 catalyst, indicating that the addition of strontium (Sr) has increased the catalyst activity, and demonstrates the potential for application in catalytic converters in motorcycles.

20-25

Authors: Ngoc Tu Nguyen*, Quang Huy Trinh, Thi Thu Ha Nguyen, Van Duc Tran, Thi Thuy Hang Ho

This study was carried out to produce a complex coagulant containing aluminum and iron salt from coal fly ash by H2SO4 acid. An application of this extracted solution as a coagulant was also investigated by the jar-test process. Fly ash collected at the Electrostatic precipitation (ESP) system in Mong Duong thermal power plant are mainly round and fine particles with diameters ranging from 0.2-8 μm, containing aluminum and iron of 15 and 6% respectively. At a room temperature of 25oC, with 1 M H2SO4 acid solution and the retention time of 20 minutes, the maximum contents of around 60.16 mg.l-1 of Fe and 4.37 mg.l-1 of Al were the most favorable to convert aluminum and iron from mineral forms to sulfate salt-based forms. The produced complex coagulants from fly ash of the Mong Duong power plant are proved to be effective for total suspended solids (TSS) removal from wastewater where the highest efficiency achieved 83.6% at the coagulant solution ratio of 5% (w/w) with a concentration of TSS in the initial wastewater was 60 g.l-1. The positive results from this study open a meaningful approach toward a huge of fly ash produced from thermal power plants as well as other coal-burn-related activities in Vietnam.

30-36

Authors: Minh Ly Nguyen*, Ton Nu Bao Tien Huyen

Isolated microspore culture is a useful tool to produce pure, fully homozygous parental lines in a short time. This study evaluated factors including the microspore developmental stage, cell culture density, and heat treatment influencing callus formation from melon microspores (Cucumis melo L.). The results showed that the obtained number of calli induced was highest (11.00±1.02) when cultivating flower buds with sizes 7.0-7.9 mm that contained microspores at middle-to-late uninucleate stages. The optimal microspore density for culture is4×104 cells. The cultured medium was NLN, containing 130 g/l of sucrose at pH 5.8. Heat treatment at 40ºC for 48 hours was best suited for callus induction of all flower bud sizes. The survival rate of microspores after 7 days of culture was lower than before inoculation and was only 75.6%. The development of the microspores and the arising of calli and embryos have been observed and evaluated for morphological cell characteristics. However, in this study, no mature embryo formation or seedling regeneration was observed.

42-46

Authors: Nguyen Thanh Binh*, Bui Thi Kim Anh, Nguyen Van Thanh, Dang Dinh Kim, Nguyen Minh Phuong

Constructed wetlands (CWs) have been widely used for wastewater treatment due to advantages such as low cost and easy operation. However, pollutant concentrations directly affect treatment efficiency by inhibiting plant and microbial growth. This study aims to evaluate the relationship between pollutant concentrations, tolerance of plants, and treatment efficiency of horizontal subsurface flow (HSF) CWs receiving synthetic wastewater. The results showed that Cyperus alternifoliusL. grew well in conditions with concentrations of chemical oxygen demand (COD) and NH4+ up to 75 and 125 mg/l, respectively, and pH 5-8. The lowest treatment efficiency was 56.7% at an initial COD concentration of 1000 mg/l. There were several dead plants in the CWs with a NH4+ concentration of 200 mg/l. When the initial COD and NH4+ concentrations were in the range of 500-750 and 75-125 mg/l, respectively, the treatment efficiencies of organic matter (COD) and NH4+ were 82.5-85.1 and 31-69.7%, respectively. The pH value was stable at a neutral level during the treatment process. The concentration ranges of COD (500-750 mg/l) and NH4+ (75-125 mg/l) were the optimal thresholds for pollution control while also ensuring normal plant growth. This study serves as a basis for considering wastewater characteristics in the design of HSF CW systems in practice.

54-58

Authors: Canh Viet Cuong Le*, Phuong Ha Tran, That Huu Dat Ton, Tuan Anh Le, Thi Loi Nguyen, Thi Kim Thu Vo, Thi Quynh Chi Vu

Solanum melongena is a member of Solanum genus that widely cultivated as fruit vegetable in Vietnam. According to Vietnamese traditional medicine, the fruits and whole plants are used to treat toothache, turgescence, pruritus, and haemorrhoids. As part of our project to study the chemical composition and bioactivity of Solanum genus in Vietnam, five flavonoid glycosides including kaempferol-3-O-β-D-glucopyranoside (1), isovitexin (2), kaempferol 3-O-β-D-glucoside-7-O-α-L-rhamnoside (3),kaempferol 3-O-β-D-sophoroside-7-O-α-L-rhamnoside(4), and kaempferol 3-O-β-D-sophoroside (5) were isolated from the methanol extract of the leaves of Solanum melongenagrowing in Thua Thien Hue province, by using various chromatography methods. Their chemical structures were determined by detailed analysis of 1D- and 2D-NMR and HR-ESI-MS data as well as comparison with the literature. Compounds (2) and (5) were isolated from Solanum melongena for the first time while compounds (3) and (4) were the first isolated from the Solanum genus. Besides, compounds 2-4 showed weak anti-inflammatory activities against NO production in RAW 264.7 macrophage line with IC50 values ranging from 54.28 to 91.37 μg/ml.

65-70

Authors: Khac Ky Lam, Thi Bao Tran Nguyen, Thi Huynh Nhu Nguyen, Thi Thanh Lai Le, Sao Mai Dam, Minh Hiep Dinh, Dai Hung Ngo*

Cordyceps neovolkiana DL0004 is a group of insect parasitic fungi collected at an altitude of 1650 m above sea level at the top of Langbiang Mountain, Lam Dong province, Vietnam. C. neovolkiana DL0004 has been used in traditional medicine and possesses numerous biological effects such as anti-cancer, anti-inflammation, antioxidant properties. In this research, the fungi biomass and fruiting body of C. neovolkiana DL0004 were cultured and examined for their antioxidant properties using test methods such as reducing power, scavenging 2,2’-diphenyl-1-picrylhydrazyl (DPPH) free radical, neutralizing 2,2’-azinobis(3-ethylbenzothiazonline-6-sulfonate (ABTS) free radical, and inhibiting xanthine oxidase (XO). The results showed that all 7 extracts of the biomass were more active than the fruiting bodies of C. neovolkiana DL0004. Furthermore, the ethyl acetate (EtOAc) extract of C. neovolkiana DL0004 biomass showed DPPH, ABTS, and XO free radical scavenging with IC50 values (the concentration of the sample required to inhibit 50% of radical) of 107.01 μg/ml, 111.91 μg/ml, and 106.2248 μg/ml, respectively. Moreover, the reducing power of the EtOAc from C. neovolkiana DL0004 biomass was 0.184 at 1000 μg/ml.From the obtained results, the biomass EtOAc fraction extract of C. neovolkiana DL0004 was demonstrated to contain antioxidant compounds with potential applications in the production of functional foods.

79-87

Authors: Thi Thanh Ngoc Nguyen, Thi Thanh Tam Phan, Thi Hiep Nguyen*

To comprehensively manage wound infection, tri-layer fibre membranes have been designed with two antibacterial agents, including silver nanoparticles (AgNPs) and chitosan oligosaccharide (COS), and their antibacterial properties were evaluated using qualitative and quantitative tests. While the first polycaprolactone (PCL) silver layer and the second plasma-treated PCL layer were fabricated by electrospinning, the third COS layer was constructed via coating and heat-vacuum drying. The formation of the membranes and their fibrous and porous structures were examined using scanning electron microscopy (SEM). The antibacterial activities of the membranes against Pseudomonas aeruginosa, Escherichia coli, and Staphylococcus aureus were examined by disk diffusion and percentage reduction assays, which were performed simultaneously as per the certificates from the Ministry of Health Institute of Public Health in Ho Chi Minh city. The tri-layer membranes, named PCLAg50/PT (plasma treatment)/COS and PCLAg500/PT/COS, achieved desirable antibacterial results with extensive inhibition zones and bacterial reduction rates ranging from 99-100%. In addition, while the PCLAg500 membrane exhibited broad inhibition zones and reduction rates ranging from 94.6-97%, the PCLAg50 membrane achieved reduction rates ranging from 67.5-82.1% despite the absence of inhibition zones. As a result, the fabricated tri-layer membranes could reduce local and opportunistic infections. Depending on infectious risks, the concentration of silver utilsed as an infection-prevention agent must be adjusted from 50 to 500 ppm to ensure safety.