Viet Nam National University Ho Chi Minh City Journal (tên cũ: Science and Technology Development Journal)
Tạp chí của Đại học Quốc gia Tp. Hồ Chí Minh
Viet Nam National University Ho Chi Minh City
An Overview of the Tectonic Evolution of the Indochina block and Granitoid Emplacement, particularly in the central and south Vietnam
Introduction: Vietnam is mainly located within the Indochina block in Southeast Asia. Asmall northern part of Vietnam belongs to the South China block, the southwest part liesadjacent to the Sibumasu block and opens to the East Sea on the east side. Tectonicactivities in Vietnam were very complicated they relate to intense interactions betweenmany geological blocks at different times. Magmatic emplacement is the final and instantproduct of tectonic activities. Methods: Geochemical data analysis from rock samples withinVietnam collected by other researchers has been reused in the scope of this study to verifythe relation between tectonic evolutions and their granitic magmatism. GCD (GeochemicalData Toolkit), an R language program for handling and recalculation of geochemical data. Results: Geochronology and geotectonic model derived from rock analysis have beenascertained main tectonic evolutions of the Indochina. The current granitoidclassification in Vietnam mostly based on petrographical studies. The Nui Cam granitoid isbeing classified as Deo Ca, Dinh Quan granitoid. However, based on trace elements, they aredifferent. They may belong to different granitoid system. Conclusion: Major tectonic eventswithin the Indochina block are well supported by the nature of granitoid emplacements. Petrological studies of these magmatic rocks would bring out valuable information toconfirm and clearly understand the tectonic evolutions of the region. Igneous rocksclassification must based on tectonic fundamental instead of petrographical studies
SECTION: SCIENCE OF EARTH AND ENVIRONMENT
A review on convenience and pollution caused by baby diapers
The one-time use and throw material are both alluring and alarming. One such is a baby diaper that takes more than 400 years to degrade in a landfill. The industry is embracing nonwovens (pads, wipes, napkins) and single-use materials to cater to the huge demand from the consumer community. Hence, to combat this diaper pollution, awareness of both the sectors is important. The toxicity associated with a product loaded with chemicals and a conscious choice that is to be made between convenience and pollution is briefed here. The paper addresses the history, nature, market share of one-time disposals with a special focus on baby diapers. The pollution and challenges in recycling diapers along with sustainable brands and commercially successful companies making eco-friendly products are identified. The latest buzz, including biopolymers and circular economy, are also discussed to give a complete perspective on the topic.
Correction: Identify factors affecting foreign direct investment capital in the southern key economic region
Article “Identify Factors Affecting Foreign Direct Investment Capital In The Southern Key Economic Region” (DOI: https://doi.org/10.32508/stdj.v22i2.1051) by Tran Thi Kim Dao, Nguyen Van Luan is added the acknowledgement section as below: ACKNOWLEDGEMENT This research is funded by Vietnam National University Ho Chi Minh City (VNU-HCM) under grant number C2019-34-02.
Risk Factors of Lung Cancer Patients: A Survival Analysis with R
Introduction: This paper studies risk factors which can have effects on the survival time of lung cancer patients during the treatment. Methods: The Cox proportional-hazards model has been applied for investigating the association between the survival time of patients and the predictors such as age, gender, the weight of patients, meal, the ECOG, and Karnofsky scores. Results: In the study, we find that the ECOG score, the Karnofsky score evaluated by doctors and the gender are the top three factors that significantly affect the hazard rate. Also, we utilize the estimated model to predict survival probability for the patients. Conclusion: In this article, we intentionally present a complete and detailed guide on how to perform a R-based package in survival analysis step by step as well as how to interpret all output results
Phenolic compounds from the leaves of Ricinus communis Linn
Introduction: Ricinus communis Linn. (Castor oil plant) is a monotypic species of Ricinus genus (Euphorbiaceae) and widely distributed in all tropical countries. Phytochemical data of this plant are scarce. As part of ongoing research on a survey of Vietnamese medicinal plants, the investigation of this plant was performed. The isolation and structural determination of five phenolic compounds isolated from the leaves of R. communis Linn. growing in Binh Phuoc province were addressed. Method: The dried power of R. communis Linn. leaves was macerated in ethanol to afford the crude extract, which was then separated by liquid-liquid extraction with n-hexane, chloroform, and ethyl acetate, respectively to obtain the corresponding extracts. These extracts were applied to multiple silica gel column chromatography and thin-layer chromatography to yield five compounds. Their chemical structures were determined by spectroscopic methods and by comparison of NMR data with literature values. Antioxidant evaluation of 1 was carried out using 1,1- diphenyl-2-picrylhydrazyl radical (DPPH) free radical scavenging assay. Results: Five phenolic compounds, including one coumarinolignan cleomiscosin A (1), two flavonol glycosides kaempferol3-O-β-D-glucopyranoside (2) and kaempferol-3-O-β-D-xylopyranoside (3), and two aromatic acids gallic acid (4) and vanillic acid (5) were identified. Conclusion: Compound 1 was determined for the first time in Ricinus genus and exhibited weak DPPH radical scavenging activity with an SC50 value of 403.23 µg/mL.
Quantitative analysis of fresh tomatoes (Solanum lycopersicum) for trace of pesticide residues from markets in Peshawar, Pakistan, using High Performance Thin Liquid Chromatography technique
Background: Vegetables and fruits are vital constituents of human diet, as it provides necessary minerals and nutrients to human body to carry out biological reactions and provide protection against various diseases and injuries. Solanum lycopersicum (tomato) is consider as cash crop in Asian countries and are fine source of vitamin C, potassium, folate, vitamin K, and other bioactive compounds including, phenolics, flavonoids, carotenoids, and alkaloids. Similar to other crops, tomato quality and yield is also affected by pests. Globally, approximately 37.8% of tomato yield is spoiled due to pests. To maintain the vegetable quality and attain more yields, pest management approaches are applied, though extensive use of toxic pesticides are becoming a part of our food chain and causing adverse effects. Methodology: The present research is intended to evaluate the levels of toxic pesticides in different tomato varieties collected from four vegetable markets (Hayatabad Phase 1, Chargano Chowk, Kohat Road and Tarnab farm) in Peshawar, Pakistan. After collection of tomato samples, level of pesticide residues (Cyhalothrin, Cypermethrin, Chlorpyrifos, Bifenthrin, and Imidacloprid) were detected using high performance thin liquid Chromatography (HPTLC). Results: After detection, level of pesticides in sample was compared with Maximum residue levels (MRLs). The magnitude of pesticides in samples was lesser to the Maximum residue levels (MRLs) provided by United State Drug Agency (USDA), though the quantity of Lambda Cyhalothrin present in the sample was almost equal to MRL (0.097 mg/kg). Conclusion: HPTLC is an efficient approach to detect pesticide traces in fruits and vegetables. Research work should be focused on it, to identify and control farmer practices which are highly linked to pesticide contamination in tomatoes and use of biopesticides should be encouraged. The cultivation of transgenic tomatoes can also be an efficient approach to elude the utilization of toxic pesticides
Highly efficient sers performance from the silver nanoparticles/graphene nanoribbons/ cellulose paper
Introduction: Metal/graphene heterojunction structure has been one of the most crucial tools in the growth of high-performance Surface-enhanced Raman spectroscopy (SERS) platform, which is appropriate for sensing applications. In this research, we developed a SERS platform, graphene nanoribbons (GNRs) decorated silver nanoparticles (AgNPs) on cellulose paper substrate, in which GNRs was synthesized by wet chemical based on unzipping process of Multi-walled carbon nanotubes (MWCNTs), then GNRs hybridized with AgNPs through magnetron sputtering method. Methods: The morphology of graphene nanoribbons coated-Ag (AgNPs@GNRs) was analyzed by field emission scanning electronic microscopy (FESEM) and transmission electron microscopy (TEM). The quality and thermal stability of GNRs were characterized using thermogravimetric analysis. Besides, its structure and quality were also characterized by Raman spectroscope. Results: The results show that the unzipping process of MWCNTs to form GNRs was strongly affected by dispersing time and stirring temperature. The suitable condition creating the Graphene Nanoribbons using MWCNTs was the dispersing time of 10 mins in an acid environment, stirring in 30 mins at room temperature and in 45 min at 100◦C. Moreover, SERS platform of AgNPs@GNRs exhibit the outstanding SERS signal enhancement with rhodamine 6G (R6G) low concentration of 10−5 M compared with pristine graphene and silver thin film. This could be attributed to the synergistic effect between AgNPs, GNRs and analyze molecules based on the enhancement of electromagnetic mechanism (EM) and chemical mechanism (CM), which plays a vital role in promoting the improvement SERS behavior. Conclusion: Ag NPs assembled onto graphene nanoribbons/ cellulose paper substrate could also serve as SERS active substrates for practical applications in various fields at trace levels
New method for preparing purity β-D-glucans (beta-Glucan) from baker’s yeast (Saccharomyces cerevisiae)
Introduction: β-D-glucans (beta-Glucan), a water-soluble polysaccharide with diversity physiological activities for applications in food and pharmaceutical industries. Methods: In this paper, we report the use of ionic liquid 1-butyl-3-methyl-imidazolium chloride [BMIM]Cl on the extraction and isolation of β-glucan from baker's yeast Saccharomyces cerevisiae. The β-D-glucans precipitated by adding water into the solution and obtained by filtration or centrifugation were pure, cleaned, and free of cell membranes. Results: The beta-glucan was obtained as white precipitates after adding water into the mixed solution. The 1D and 2D-NMR spectrum and titration methods applied for qualitative and quantitative determination showed that the beta-glucan product contained 78.2% 1,3-β-D glucan with 98.4% purity. Conclusion: This method can be used to prepare purified beta-glucan from baker's yeast.
Generating and characterizing the anti-human CD45 monoclonal antibody
Introduction: CD45 is a common marker of leukocytes. Anti-human CD45 monoclonal antibody (MAb) has been used widely in diagnosing and monitoring hematologic diseases. The aim of this study was to generate an anti-human CD45 MAb, which can be used in research and diagnosis. Methods: Recombinant human CD45RO antigen was expressed from E. coli BL21 (DE3), purified and analyzed by SDS-PAGE and Western blotting. The purified CD45RO antigen was used to immunize Balb/c mice. Spleen cells from immunized mouse were collected and fused with P3X63Ag8.653 myeloma cells to form hybridoma. Anti-CD45 antibody-secreting capacity of hybridoma clones was evaluated by ELISA assay. Anti-CD45 MAb from the culture supernatant of the chosen hybridoma clone was purified by affinity chromatography. The MAb was characterized the biochemical characteristics and biological activity. Results: Recombinant human CD45RO antigen was expressed and purified from E.coli BL21 (DE3). Injection of purified CD45RO antigen provoked the immune response in Balb/c mice. Hybridoma clones were generated successfully by the fusion of spleen cells from the selected immunized-mouse and myeloma cells. Among these hybridoma clones, one with the highest yield of MAb production was identified. The isotype of the anti-CD45 MAb created in this work is IgG2b, while its the light chain is kappa (k) type. The affinity of this MAb with CD45RO antigen is high with Kd value at the picomolar level. The anti-CD45 MAb can interact with CD45 naturally expressed on the surface of Jurkat cells in Western blotting and fluorescent immuno-staining assay. Conclusion: We have developed successfully an anti-human CD45 MAb using hybridoma technology, which can recognize CD45 in ELISA, Western blotting, and fluorescent immuno-staining analysis. Although further investigations are necessary, obviously, our anti-human CD45 MAb is potential for research and diagnosis applications.
The effect of content and thickness of chitosan thin films on resistive switching characteristics
Introduction: Nowadays, a resistive switching memory using biological, transparent, and environmentally friendly materials is appreciated as the tendency of science and technology, especially in the field of electronic devices. Chitosan (CS), having dominant characteristics such as non-toxic, biocompatible and large capacity, plays as a switching medium in resistive random access memory devices (RRAM). Methods: In our study, CS film was fabricated onto a commercial substrate (FTO) using a simple spin coating method, and the top electrode (Ag) was deposited by a directcurrent sputtering technique. Results: The Ag/CS/FTO devices shown the bipolar switching behavior when applying sequence voltage from -1.5 to 2V with the set process in the negative bias and the reset process in the positive bias. The content (0.2, 0.5, and 0.8 wt%) and thickness (100, 300, 500 nm) of chitosan film significantly affect the resistive switching performance. The devices with 0.5 wt%/v concentration and 300 nm-thickness of CS have shown better efficiency than the others with endurance over 100 sweeping cycles and ON/OFF ratio at ca. 2x10 times. Conclusions: It is found that the chitosan material has a large potential candidate for applications in optoelectronic devices
SrTiO3 nanocubes doped with ir as photocatalytic system for enhancing H2 generation from water splitting
Introduction: Designing an effective photocatalyst for hydrogen (H2) performance under visible irradiation with a decrease the bandgap energy of semiconductor has been considered as an essential aspect in boosting the performance of photocatalytic reactions for hydrogen performance from the water-splitting process. Herein, we focus on evaluating the role of doping with Ir into SrTiO3 structure fabricated by the hydrothermal method for H2 generation. Methods: The crystalline characteristics of the Ir-SrTiO3 photocatalyst were carried out via X-ray powder diffraction (XRD) and field emission scanning electron microscopy (FE-SEM). The chemical composition and the optical properties of the Ir-SrTiO3 were classified by energy-dispersive X-ray spectroscopy (EDX) and UV-Vis spectra, respectively. Results: The results showcased that the dramatically improved absorbing performances of Ir/SrTiO3 specimen were observed. This could be governed by the presence of Ir impurity states in the forbidden energy gap, causing a decrease in the energy gap of SrTiO3. This work also revealed that Ir doped into SrTiO3 nanocube structure exhibited excellent photocatalytic H2 evolution compared with pristine SrTiO3 (~454 and ~325 mmol.h−1 .g−1 H2 production under UV and visible light irradiation, respectively). A rational photocatalytic mechanism is projected to be able to provide significant awareness for further research. Conclusion: The results are believed to be the role of Ir states and nanocube structures of SrTiO3 as a new approach in renewable energy resources.
Synthesis and evaluation of α-glucosidase and tyrosinase inhibitory activities of ester derivatives of usnic acid
Introduction: Usnic acid isolated from lichen was a potential bioactivity compound. It has a broad spectrum bioactivity, including antiviral, anti-inflammatory, anticancer… However, low solubility in water limited its application. Many researchs have done to overcome the restriction. Recent results showed that usnic acid derivatives bearing triazole, enamine, pyrazole and benzylidene groups had strong antiviral and anticancer activities. Thus, investigation of usnic acid derivatives synthesis was an attractive aspect due to the diversity of bioactivities of usnic acid derivatives. Methods: Usnic acid was isolated from lichen, six ester derivatives of usnic acid were synthesized from usnic acid with acetyl chloride and benzoyl chloride under stirring at room temperature. The products were evaluated α-glucosidase and tyrosinase inhibitory activities. Results: All the ester derivatives were created with good yields. All derivatives exhibited the same or higher activity comparing with usnic acid. Ester of usnic acid bearing benzoyl group showed excellent α-glucosidase activity with IC50 26.7±0.57 and 68.8±0.15 µM. Conclusion: Among the ester derivatives, UE1 and UE6 were reported as as new compounds. Interestingly, all products displayed the same or higher biological activity than the starting material, usnic acid when evaluated against α-glucosidase and tyrosinase
Effects of pH, temperature and oxygen-limited condition on the virulence of Vibrio parahaemolyticus
Introduction: Vibrio parahaemolyticusis a popular Gram-negative bacterium in the marine and estuarine regions. It can cause Early Mortality Syndrome (EMS), now named Acute Hepatopancreatic Necrosis Disease (AHPND), which resulted in severe losses to the shrimp culture. This study aimed to investigate the effect of pH, temperature, and oxygen-limited condition on the extracellular enzymatic activity of V. parahaemolyticus. Methods: V. parahaemolyticus XN9, an AHPND-causing strain, was cultured in Brain Heart Infusion (BHI) medium at different pHs (7.5, 8.0, 8.5 and 9.0), temperatures (25oC, 30oC, and 35oC) and different oxygen conditions (either 120rpm shaking or static with the presence of oxygen absorber packages). The activity of five extracellular enzymes, includingcaseinase, lecithinase, chitinase, gelatinase, and lipase, was assessed using the agar-based method with the corresponding media. Results: When pH was increased from 7.5 to 9.0, caseinase and lipase activity was decreased significantly by 88% and 44%. In contrast, gelatinase activity increased markedly from 0 to 1.38 ± 0.17 (+) mm, and lecithinase reached the highest activity, which was 2.96 ± 0.13 mm (++) at pH 8.5. Regarding effect of temperature, highest activity of caseinase (0.85 ± 0.13 mm (+)) and gelatinase (1.37 ± 0.25 mm (+)) was obtained at 350C, lecithinase at 30oC and lipase at 25oC. Regarding the effect of oxygen level, the activity of most tested enzymes decreased significantly following the decrease of oxygen level. The highest activity of caseinase, gelatinase, and lipase was observed when the bacteria were cultured and tested in a fully oxygenated condition while lecithinase showed the highest activity when the bacteria were cultured in oxygenated condition but tested in oxygen-limited condition. No chitinase activity was observed in any of the tested conditions. Conclusion: Our data suggested that extracellular enzymatic activity of V. parahaemolyticus is significantly influenced by environmental conditions.No particular testing condition resulted in the highest activity for all tested enzymes. However, warm temperature (30/ 35oC), mildly alkaline pH (pH 8.0), and fully oxygenated condition could increase the overall extracellular enzymatic activity of V. parahaemolyticus, thus increase its potential virulence.
Application of anthracnose resistance-associated molecular markers in the detection of resistant chili pepper cultivars in Vietnam
Introduction: Colletotrichum species is responsible for anthracnose, a worldwide serious disease, causing an important loss in chili pepper production. Therefore, screening disease resistant and sensitive chili pepper cultivars in Vietnam is important not only for in-depth studies of disease resistance-associated molecular mechanisms but also for chili production improvement via molecular marker-assisted breeding in Vietnam. Methods: To this end, in this study, two Colletotrichum isolates were obtained from the infected fruits collected from chili pepper (Capsicum annuum) fields in Tra Vinh province. According to the morphology analysis and the sequencing results of the internal transcribed spacer (ITS) regions, these isolates were identified as C. scovillei and C. acutatum. In order to identify the anthracnose-resistant chili pepper cultivars, the pathogenicity test was conducted by infecting fully developed green fruits of eleven chili pepper cultivars with the two isolated Colletotrichum strains. Results: CN404 and HNCS were the two strongest anthracnoseresistant cultivars. Two chili pepper cultivars, TV3 and PN400, showed different resistance tendencies to each Colletotrichum isolates. Four different SSR molecular markers were used in this study to identify the potential molecular markers associated with anthracnose resistance traits in chili pepper cultivars. Among the four examined markers, HpmsE126 was detected in two anthracnoseresistant chili pepper cultivars, suggesting its close relation to the anthracnose resistance trait in chili pepper. Conclusion: Given that two of the three most anthracnose-resistant cultivars, CN404 and TV3, possess HpmsE126 marker, this marker can be used to detect anthracnose-resistant lines in chili pepper breeding in Vietnam.
Effect of electrospinning parameters on the morphology of polyurethane/polycaprolactone fibers
Introduction: Electrospinning is now being widely used as a potential tool for tissue engineering to manufacturing tissue grafts, wound dressings, medical fabrics, and drug delivery systems. Regarding biomaterials, polyurethane (PU) and polycaprolactone (PCL) and their combination are prospective candidates for the fabrication of electrospun membranes used in tissue engineering due to their suitable biocompatibility, biodegradability, and mechanical properties. Thus, this study investigates how to manipulate the electrospinning process of PU/PCL to obtain nanofibers with desired features. Methods: PU/PCL dissolved in N,N-Dimethylformamide, and tetrahydrofuran were electrospun with various applied voltages, tip-to-collector distances, and flow rates. The collected membranes were observed using a scanning electron microscope to evaluate the effect of electrospinning conditions on their morphology and fiber diameters. Results: Slower flow rate, longer tip-to-collector distance, and higher voltage all led to smaller, more uniform fibers. By manipulating these factors, the study yielded a non-woven, porous membrane with uniform, separated nanofibers at the condition set of 12 cm tip-to-collector, 20 kV applied, and 0.5 mL/h flow rate. Conclusion: The study determined the effect of electrospinning parameters on the morphology of polycaprolactone/polyurethane fibers and obtained membrane with suitable properties for further research.
Deriving formulations for forecasting the ultimate strength of locally dented ring-stiffened cylinders under combined axial compression and radial pressure loads
Introduction: This paper focuses on the derived equations to evaluate the ultimate strength of ring-stiffened cylinders with local denting damage under combined loadings. The damage generation scenarios in this research are representing the collision accidents of offshore stiffened cylinders with supply ships. Methods: Numerical analysis of structures are performed using Abaqus software after validation against the experiments from the authors. The responses from seventeen cylinder specimens are analyzed to develop the numerical methods. Results: Good accuracy results were achieved when comparing the test results and the simulation results. Parametric studies are then performed on design examples of ring-stiffened cylinders when considering both intact and damaged conditions for assessing the reduction factor. Then, the novel simple design equations to assess the residual strength of ring-stiffened cylinders after ship collision are derived based on the regression analysis. These equations have good accuracy with mean value Xm (Uncertainty modeling factor) around 1.0 and together with COV (Coefficient of Variation) lower than 5.3%. Conclusion: The accuracy and reliability of the derived equations are validated by comparing it with the existing test data in open access. It is concluded that the proposed equations have high accuracy and reliability, and convenient application for the purpose of checking the residual strength of dented offshore cylinder under ship collisions.
Using an LQR active anti-roll bar system to improve road safety of tractor semi-trailers
Introduction: Tractor semi-trailer vehicles are playing an increasingly important role in the global freight chain. However, due to the heavy total load and height of the center of gravity, this type of vehicle is often at a higher risk of instability than other vehicles. This paper focuses on improving the vehicle roll stability by using an active anti-roll bar system. Methods: The Linear Quadratic Regulator (LQR) approach is used for this purpose with the control signal being the torque generated by the active anti-roll bar system. In order to synthesize the controller, the roll angle of the vehicle body and the normalized load transfer at all axles of the tractor semi-trailer vehicle are considered as the optimal goals. Results: The simulation results in time and frequency domains clearly show the effectiveness of the proposed method for the active anti-roll bar system, because the reduction of the desired criterias is about 40% less when compared to a vehicle using the passive anti-roll bar system. Conclusions: The effectiveness of the active anti-roll bar system on improving the vehicle roll stability, has been verified in this theoretical study with the LQR optimal controller. This is an important basis for conducting more in-depth studies and future experiments
The global textile business is now gearing towards greener alternatives to combat pollution and avoid synthetics in production. Ironically, there is an increased awareness among consumers on the quality of the product and choices they make in their shopping. The natural and synthetic fibres have set limitations, which has made manufacturers look out for other alternative fibres. Bamboo, banana, milk, and corn are experimented for its commercial capabilities to perform as a textile material. To add on to the list, orange, the popular, and the most preferred fruit are known for its refreshing flavour. The peels after consumption/ processing of the fruit are discarded in the landfill, which is an organic waste with immense potential. This paper details the successful brand `Orange fibre', its journey from scratch, and the properties of textiles made from processing orange peel waste. The current areas of research have also been covered in a brief way, to invite more scholars to create solutions for the hitherto pollution orange peel waste
Removal of methyl orange by heterogeneous fenton process using iron dispersed on alumina pillared bentonite pellet
Introduction: Heterogeneous Fenton is one of the Advanced Oxidation Processes (AOPs) and has been proven to be effective on azo dye degradation. However, a low-cost catalyst and factors affecting the processes of this system were further investigated. \ Methods: In this study, pellets of iron alumina pillared bentonite (PFeAPB) were prepared by dispersing iron ions on alumina pillared bentonite pellet. Catalyst activity and lifetime were investigated via efficiencies of Methyl Orange (MO) decolorization and Chemical Oxygen Demand (COD) removal, a typical dye type of textile wastewater. Characteristics of the PFeAPB catalyst were examined by X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) surface area, and X-ray fluorescence (XRF). Results: Results of batch experiments showed that specific surface area of the PFeAPB catalyst was 111.22 m2 /g higher than its precursor by 2 times (57.79 m2 /g). Goethite, Hematite and Maghemite phases with approximately 11.5% of iron elements containing in the catalyst were detected via XRD and XRF. Experimental conditions of pH, initial MO solution, Hydrogen Peroxide concentration, reaction time and catalyst loading were 2.0 ± 0.1, 12.7 mmol/L, 150 min and 20 g/L, respectively, to achieve 88.68 ± 5.69% of MO decolorization and 50.27 ± 6.05% of COD removal while dissolved iron in this heterogeneous Fenton process was below standard limit (2 ppm). Catalyst activity decreased by 5.22% in decolorization efficiency after the two first reusages. Conclusion: These primary results showed the potential of applying PFeAPB catalyst in heterogeneous Fenton process with low iron leaching into water
SCIENCE OF EARTH AND ENVIRONMENT - RESEARCH ARTICLE
Relationship between water temperature and phytoplankton communities in Ba Lai river, Viet Nam
Introduction: Phytoplankton which can affect higher trophic levels play a pivotal role as primary producers. Phytoplankton structure and diversity may, besides other factors, be controlled by the changing of water temperatures. Hence, the present study aimed to determine some relationship between phytoplankton assemblage and water temperature in Ba Lai River, Vietnam. Methods: In this research, sample data along the Ba Lai Estuary during two surveys were carried out in rainy season (September, 2017) and in dry season (March, 2018), and analyzed by Spearman's correlation and Linear regression analysis to find the correlations. Results: The results showed that the temperature of surface water in Ba Lai River was quite stable spatially. A total of 128 species belonging to 5 groups- namely cyanobacteria, diatoms, green algae, euglenids and dinoflagellates- were recorded in which diatoms were clearly dominant. Additionally, multiple stepwise linear regression revealed that phytoplankton assemblage correlated significantly with the temperature of surface water. The water temperature had a significant positive correlation with chlorophyll-a concentration but was negatively correlated with Margalef's diversity index in the rainy season. Moreover, the significant negative association of water temperature with biomass of phytoplankton and biomass of diatoms, which was principal in species number, were determined in the dry season. Conclusion: This study investigated the phytoplankton communities and found their correlation with environment in the area, and demonstrated advantages of phytoplankton which warrant their further research.
Fusion-fission in the reactions of the 58Ni + 251Cf and 64Zn + 248Cm combinations
Introduction: In the present study, we evaluate the nucleon evaporation, alpha decay, and fission widths in the fusion-fission of the 58Ni+251Cf and the 64Zn + 248Cm reactions for the synthesis of the super-heavy 309,312126 nuclei. Methods: The feasibility of the synthesis of the 309,312126 isotopes via the mentioned systems is investigated based on the widths. The widths in the excitation energy range of E∗ = 10 – 100 MeV are calculated in the scope of the statistical model, in which the level density is calculated by using the Fermi-gas model. By employing the LISE++ code, the level densities the compound nuclei, 309,312126 nuclei, are calculated to be about 105 – 1050 (MeV−1 ) in the energy range of interest. Results: The lifetime of the compound nuclei, 309,312126 nuclei, which are estimated based on the total width, is about 10−22-10−20 s. The fission has the largest width compared to those of the alpha decay and nucleon evaporations. Hence, the 58Ni+251Cf and the 64Zn + 248Cm combinations are appropriate to the study of the mass distribution. In addition, the large alpha decay widths suggest the 309,312126 isotopes be the alpha-decay nuclei. Conclusion: The results are expected to be useful for considering measurements at facilities in the near future.
Secretory expression of the recombinant FGF-2 protein in Pichia pastoris carrying multiple copies of target gene
Introduction: Fibroblast growth factor-2 (FGF-2) is a multifunctional protein that plays an important role in the regulation of proliferation, differentiation and migration of a variety of cells. The recombinant human FGF-2 (rhFGF-2) is currently used in stem cell culture, medicine and cosmetic products. In this study, we aim to produce secreted rhFGF-2 protein from a Pichia pastoris strain containing multiple copies of the fgf-2 gene to eliminate the disadvantages of intracellular expression systems. Methods: The recombinant Pichia pastoris carrying the fgf-2 gene was cloned by using homologous cloning method. The recombinant strains were screened by PCR reactions using specific primers for the target gene and the AOX1 promoter sequence. Moreover, the copy number of the fgf-2 gene inserted into the P. pastoris genome was identified by semi-quantitative PCR method. The secreted rhFGF-2 protein was collected in the induced BMMY medium at a final methanol concentration of 0.5%, and purified by one-step heparin affinity chromatography. The quantity and biological activity of the purified protein were determined by competitive ELISA method and MTT assay on NIH-3T3 cell line, respectively. Results: Various recombinant P. pastoris clones carrying different copy numbers of the fgf-2 gene were obtained and categorized into 3 groups: the low copy strains (4-5 copies), medium copy strains (8-11 copies), and high copy strains (more than 20 copies). Among those strains, the 4-copy one produced the rhFGF-2 protein at the highest expression level. After purification, the purity of rhFGF-2 protein reached 98.8%, and the recovery yield was 179.2 µg of protein from 200 mL of flask culture (equivalent to 850 µg/L). The purified rhFGF-2 protein showed similar biological activity on NIH-3T3 cell line with the commercial FGF-2 protein. Conclusion: The recombinant FGF-2 protein was successfully secretory expressed from Pichia pastoris, and successfully purified by only one-step chromatography.
Evaluation of low energy X-ray depth dose distribution by gafchromic film for dosimetry in food irradiation
Introduction: Dosimetry is of crucial importance in radiation processing of food. Among others, plastic film has been widely used for dosimetry in radiation therapy since its density is quite similar to the equivalent biological materials. In this study, the depth dose distribution was estimated by using gafchromic film for the purpose of dosimetry in food irradiation. Experimental: The HD-V2 gafchromic dosimetry film was employed to measure the interested dose instead of ion chamber. A stack of 19 PMMA (polymethyl methacrylate) sheets interleaved with 20 pieces of gafchromic film was made. The phantom was applied in the low energy X-ray beams (maximum 100 keV) to obtain the depth dose profile. Results: A significant correlation between absorbed doses (D) and color level or optical density (O.D.) of irradiated dosimetry films was observed. The fitting function has the form of O.D = a + b D−c , where a, b, c are the parameters to be fitted. The depth dose distribution in the 30 mm thickness phantom was inferred from the calibration. Conclusion: The present method and the depth dose profile to be obtained are very meaningful in the processing of foodstuffs by radiation
ENGINEERING AND TECHNOLOGY - METHODOLOGIES
Factors affecting acrylamide mitigation in fried potatoes
Introduction: Recent findings of acrylamide, a carcinogenic agent to humans, in foods have led to great efforts to elucidate the mechanisms of acrylamide formation and its mitigation. The acrylamide was generated during the browning process by the Maillard reaction of amino acid asparagine and reducing sugars at temperatures above 120 ◦C. Asparagine was determined to be a precursor of acrylamide formation. Therefore, asparagine reduction in raw materials can be taken into account to limit the acrylamide level in prepared foods. L-asparaginase has been used to consume acrylamide precursor by catalyzing the conversion of asparagine into aspartic acid and ammonia. Several factors including enzyme concentration, pH, temperature and frying time can influence the efficiency of acrylamide mitigation by enzyme. In the present work, we selected potatoes as raw materials to investigate the effects of factors on the acrylamide mitigation in fried potatoes. Methods: By pre-treating potato strips in different conditions of enzyme concentrations, pH, temperature and frying time, the effects of these parameters on acrylamide levels in fried products were evaluated by measuring UV-Vis spectra of sample solutions containing acrylamide. The maximum absorbance values at 224 nm were used to determine the acrylamide concentrations by calculation from a calibration curve. Experimental data were statistically analyzed by one-way ANOVA. Colorspace measurements were performed to describe the differences in colors of the fried products after various frying times. Results: A calibration curve was established to determine the acrylamide content of sample solutions via their maximum absorbance values. Pre-treatment of potato strips with a solution of 1.0 IU/mL asparaginase at 37 ◦C, pH 7.3, for 30 min led to a 45.6% reduction of acrylamide in French fries compared to a solution without enzyme. The optimum pH value for the most efficient enzyme activity was 7.3. Frying time ranging from 1.0 to 6.0 min increased acrylamide content and induced a darker appearance product. Conclusions: By using UV-Vis measurements, we demonstrated the effects of factors on L-asparaginase based acrylamide mitigation in fried potatoes. The conditions which gave the lowest acrylamide concentrations were assessed. The results could be applicable for commercial processes to minimize acrylamide content in prepared potatoes.
ENGINEERING AND TECHNOLOGY - RESEARCH ARTICLE
An explicit topology optimization method using moving polygonal morphable voids (MPMVs)
Introduction: Conventional topology optimization approaches are implemented in an implicit manner with a very large number of design variables, requiring large storage and computation costs. In this study, an explicit topology optimization approach is proposed by moving polygonal morphable voids whose geometry parameters are considered as design variables. Methods: Each polygonal void plays as an empty-material zone that can move, change its shapes, and overlap with its neighbors in a design space. The geometry parameters of MPMVs consisting of the coordinates of polygonal vertices are utilized to render the structure in the design domain in an element density field. The density function of the elements located inside polygonal voids is described by a smooth exponential function that allows utilizing gradient-based optimization solvers. Results & Conclusion: Compared with conventional topology optimization approaches, the MPMV approach uses fewer design variables, ensure mesh-independence solution without filtering techniques or perimeter constraints. Several numerical examples are solved to validate the efficiency of the MPMV approach
Improved error of electromagnetic shielding problems by a two-process coupling subproblem technique
Introduction: The direct application of the classical finite element method for dealing with magneto dynamic problems consisting of thin regions is extremely difficult or even not possible. Many authors have been recently developed a thin shell model to overcome this drawback. However, this development generally neglects inaccuracies around edges and corners of the thin shell, which leads to inaccuracies of the magnetic fields, eddy currents, and joule power losses, especially increasing with the thickness. Methods: In this article, we propose a two-process coupling subproblem technique for improving the errors that overcome thin shell assumptions. This technique is based on the subproblem method to couple SPs in two-processes. The first scenario is an initial problem solved with coils/stranded inductors together with thin region models. The obtained solutions are then considered as volume sources for the second scenario, including actual volume improvements that scope with the thin shell assumptions. The final solution is, to sum up, the subproblem solutions achieved from both scenarios. The extended method is approached for the h-conformal magnetic formulation. Results: The obtained results of the method are checked/compared to be close to the reference solutions computed from the classical finite element method and the measured results. This can be pointed out in a very good agreement. Conclusion: The extended method has also been successfully applied to the practical problem (TEAM workshop problem 21, model B).
Enthusiastic discussions on solid physic and material science at SPMS2019
At 11th National Conference of Solid Physics and Material Science (SPMS2019), to which eminent scientists (5 plenary speakers and 16 invited speakers) were invited, most of the discussion focused on solid physic and material science. Around 300 researchers interested in the subject attended the conference and actively participated in the discussion. There were more than 200 reports with five specialized subcommittees: (A) Physics and magnetic materials, (B) Semiconductor and dielectric physics, (C) Materials - semiconductor components - dielectric, (D) Biomedical materials - agriculture, energy - environment, (E) Composite materials - metals - ceramics. Besides, numerous reports submitted to the Journal of Science and Technology (Vietnam Academy of Science and Technology), full-text reports sent to the Organizing Committee, after a critical review process, had been summarized and published in the Collection of conference reports.
Bio-Electro-Fenton: a novel method for treating leachate in Da Phuoc Landfill, Vietnam
Introduction: Leachate is a noticeable pollution problem because it contains a considerable amount of persistent organic pollutants (POPs). If leachate isn't treated thoroughly, its leak will negatively affect the environment. Therefore, appropriate treatment technologies are required to remove them. Bio-Electro-Fenton (BEF) is a new method using microorganisms such as electrolytes to convert chemical energy into electricity to help create H2O2 support advanced oxidation process (AOPs). Realizing the potentials that BEF brings, this study applies BEF to assess the effectiveness of leachate treatment at Da Phuoc landfill (operation period > 12 years), Ho Chi Minh City, which to save costs and energy for Fenton process. Methods: The BEF pilot scale model (30 x 10 x 10 cm) is divided by a proton exchange membrane (PEM) (Nafion®112) into two chambers (anode and cathode). Cathode chamber used a graphite electrode, the anode chamber used a carbon fabric electrode. The experiments aimed to determine the optimal conditions of parameters affecting the BEF system by determining the efficiency of COD removal and BOD5/COD ratio in leachate. Results: At optimal conditions of the model including pH 3, [Fe2+ ] = 4g/L, current intensity = 1A, reaction time 60 minutes and airflow = 12 L/min, as a result COD was reduced by 68.2 ± 1.04 % from 4950 ±14 mgO2/L to 1574.1 ± 51.4 mgO2/L, the ratio of BOD5/COD = 0.1 Conclusion: The study result showed thatBio-electro-Fenton process is effective for wastewater with high concentrations of pollutant and difficult to treat as leachate suggesting that the appropriate method for pre-treatment processes support the thorough elimination of pollutants.
Forecasting of saline intrusion in Ham Luong river, Ben Tre province (Southern Vietnam) using Box-Jenkins ARIMA models
Introduction: Ham Luong River is a branch of Mekong River located in Ben Tre Province, which has played a crucial role in supporting livelihoods of local residents and the province's economic development. However, the saline intrusion has been expanding in Ham Luong River, which seriously affects the productive agriculture, aquaculture, and further causes tremendous difficulties for local people's lives. Thus, it is crucial to have research for forecast the saline intrusion in Ham Luong River. Our aim was to develop mathematical models in order to forecast the saline intrusion in Ham Luong River, Ben Tre Province. Methods: The Auto regressive integrated moving average (ARIMA) model was built to forecast the weekly saline intrusion in Ham Luong River, which has been obtained from Ben Tre Province's Hydro-Meteorological Forecasting Center over eight years (from 2012 to 2019). Results: The saline concentration increased from January to March and then decreased from April to June. The highest salinity occurred in February and March while the lowest salinity was observed in early June. Moreover, the ARIMA technique provided an adequate predictive model for a forecast of the saline intrusion in An Thuan, Son Doc, and An Hiep station. However, the ARIMA model in My Hoa and Vam Mon might be improved upon by other forecasting methods. Conclusion: Our study suggested that the nonseasonal/seasonal ARIMA is an easy-to-use modeling tool for a quick forecast of the saline intrusion
Xao Tam Phan (Paramignya trimera) methanol extract induced apoptosis in hepatocellular carcinoma HepG2 cell line in vitro
Introduction: Xao Tam Phan (Paramignya trimera) has long been used in Viet Nam as an herbal medicine for the treatment of Hepatitis, hepatocellular carcinoma, and diabetes. This study aimed to determine the anti-proliferation effect of Paramignyatrimera extract(P.trimera extract) on HepG2 hepatocellular carcinoma cells. Methods: AlamarBlue assay was used to determine the IC50 values of P. trimera extract on HepG2 cells. Adipose-derived stem cells (ADSCs) was used as normal cell control. For apoptosis examination, P. trimera extract-treated HepG2 cells were incubated with Annexin V/Propidium iodide (PI). Then they have been analyzed their expression of Annexin-V and PI by flow cytometry. The cell nuclear degradation also was evaluated by PI/Hoechst 33342 staining assay. Results: Doxorubicin and P. trimera extract IC50 values on HepG2 cells were 55.13 ± 2.028 ng/ml and 582.533 ± 16.521 µg/ml, respectively. Those on ADSCs were 5.96 ± 0.56 ng/ml and 268.976 ± 19.325 µg/ml, respectively. Side effect index value (SEI) of P. trimera extract was 2.175 ± 0.12, and the SEI of doxorubicin was 8.71 ± 0.36. Flow cytometry analysis indicated significant apoptosis on P. trimera extract-treated HepG2 cells at a dose of 500 µg/ml (32.39 ± 2.28% apoptotic cells, and 14.63 ± 1.59% necrotic cells). Nuclear aggregation and degradation was seen on 500 µg/ml P. trimera treated HepG2 cells. Conclusion: P. trimera extract could inhibit HepG2 hepatocellular carcinoma cell proliferation by inducing apoptosis