Vietnam Academy of Science and Technology: Journals Online
Vietnam Academy of Science and Technology: Journals OnlineNot a member yet
7064 research outputs found
Sort by
PRIMARY STUDY FOR EFFECTS ON TRANSDIFFERENTIATING RAT NEONATAL CARDIOMYOCYTES INTO PACEMARKER CELLS OF SEVERAL VIETNAMESE PLANT EXTRACTS
No full textCardiovascular diseases have been accounted for the highest mortality rate worldwide.
Synthesis and Electrochemical Characterization of NiCoS Nanosheets/reduced Graphene Oxide for Energy Storage Applications
No full textIn the present study, NiCo2S4-rGO (NCS-rGO) composites were fabricated by mixing active materials including NCS and rGO individually using polyvinypyrrolidone (PVP) as a binder to form a homogeneous mixture. Therein, rGO was prepared by modified Hummer’s method while NCS nanosheets were successfully synthesized by thermal decomposition method using 1-dodecanethiol (DDT) as a sulfur source. The NCS-rGO composites based electrode was then produced using 3D printing technique making easy to design electrodes with the desired shape. The architecture and elemental composition of electrode components are characterized by energy dispersive x-ray analysis (EDX) and scanning electron microscopy (SEM). The electrochemical activity of the NCS-rGO electrode were studied in three electrode configuration in 6M KOH electrolyte by CV, GCD and EIS measurement. The obtained results indicate that the combination of NCS nanosheets and rGO could improve the electrical conductivity of the individual materials, enhance electrochemical performance of electrode. The as-prepared NCS-rGO electrode posseses a high Csp of 1535.8 Fg-1 at 4 Ag-1 with excellent cycling stability even after 2500 charge-discharge cycles, demonstrating that the NCS-rGO nanocomposites are promising candidates for electrode materials for high-performance energy storage devices in the future
Dynamic crack propagation in specimens with a surface irregularity
No full textInitiation of cracks and their propagation in prescribed orientations on tubular specimens has been made possible on a dynamic fatigue testing rig developed at the University of Aberdeen. This rig was originally designed to perform experiments on single edge notched beams (SENB) [1,2]. Modifications have recently been made so as to accommodate experimental tests on tubular specimens with a range of sizes and other cross sections. Crack initiation at grooves on such specimens has been followed by crack growth. At the same time, lateral oscillations of cracked specimen have been measured, as well as accelerations of base excitation, masses above and below cracked specimen. Forces on these two masses have been observed by two load cells attached at positions close to specimen. These load cells facilitated the measurement of stresses in experiment. Crack length time histories have also been constructed by applying an alternating current potential difference (ACPD) method. Fatigue cracks were initiated at the pre-cut grooves in aluminium tubular specimens. Three specimens with different groove sizes were tested in fifteen individual experiments. A three-dimensional Finite Element model was established for each specimen so as to calculate the stress concentration factor (SCF). This formed the basis of determining the amplitude of forcing input made possible by an electromechanical shaker. The phase shifts of acquired time histories has provided some indication of energy transfer mechanism during fatigue and system dynamic response. Observations of cracked specimen displacement during experiments was compared against calculated displacement from elastic theory. Nonlinear responses were observed, suggesting nonlinear stiffness characteristics of the specimen due to discontinuities introduced by crack growth and plasticity effects. Comparison of damage combinations in experimental observation was made with predictions from BS EN 1999-1-3. All experimental observations of total damage combination were higher than predicted values by the latter code
Growth performance of Hydrangea macrophylla ‘glowing embers’ on culture medium with different macro-element concentrations and culture conditions
No full textHydrangeas are very popular shrubs thanks to their attractive, colorful flowers and foliage. Recently, they have been commercialized for cut-flower production. For mass propagation of this plant species using plant tissue culture, it is necessary to study the effects of culture medium and culture conditions on in vitro plant growth. In the first experiment, in vitro hydrangea shoots were cultured for 56 days on Murashige and Skoog (MS) media containing one among five different types of macro-elements. The half concentration of NH4NO3 on MS macro-elements significantly increased fresh and dry weights of hydrangea shoots in comparison with other treatments. The number of roots of in vitro plants in this treatment were the highest, resulting in better absorption of culture nutrient. Cross sections of the shoot base on day 14th showed that reducing only NH4NO3 on the MS medium enhanced the formation of adventitious roots. The experiment on culture conditions showed that photoautotrophic condition was suitable for the in vitro growth of hydrangea. Plants grown under photoautotrophic (PA) condition had increased fresh weight (341.39 mg/plt), increased dry weight (31.03 mg/plt) with leaf area (7.76 cm2) significantly greater than those grown under photomixotrophic (PM) condition (259.53 mg/plt, 38.22 mg/plt and 4.73 cm2 respectively). In addition, the net photosynthetic rate (Pn) of plants under PA condition was statistically higher and increased over the culture period while Pn of plants under PM condition remained constant. This study demonstrated that MS salts with half concentration of NH4NO3 and photoautotrophic culture method were appropriate for in vitro growth of hydrangea.
Production of monoclonal antibody against Ompa protein of Candidatus Liberibacter asiaticus causing citrus greening disease
No full textCitrus Greening, also known as HuangLongbing (HLB), is considered one of the most dangerous citrus diseases, and limiting the production of citrus trees all over the world. Production of antibodies against Ompa protein of Candidatus Liberibacter asiaticus (CLas) for detection of citrus greening disease is considered as promising research direction. In this study, for the purpose of producting antibodies against Ompa of CLas, we firstly used the camel VHH antibody library for screening VHH antibodies against Ompa using phage-display technique. Next, phages which had strong interaction with Ompa as shown in ELISA were selected for phagemid isolation and the DNA fragments encoding VHH antibodies were sequenced. The DNA fragment encoding the best VHH antibody was then selected and inserted into the expression vector pET-21a (+), then cloned in Ecoli DH5α strain and expressed in BL21 (DE3) strain. The expression of VHH antibodies against Ompa was optimized at different temperatures with an inductive concentration of 0.1 M IPTG. Anti-Ompa VHH antibodies were purified under denatured conditions then re-folded. The biological activity of the VHH antibody with Ompa antigen was assessed by indirect-ELISA reaction. Results indicated that the VHH antibody had a very strong interaction with the Ompa antigen. This opens up the prospect of applying VHH antibody in the detection of citrus greening disease
. Identification of CYP2C9, VKORC1 genotypes and recommendation of warfarin dose for Vietnamese cardiovascular patients
No full textWarfarin is a well-known anticoagulant that capable of reducing the activity of vitamin K-dependent clotting factors. It has been widely used for cardiovascular patients. However, patient’s genotype of CYP2C9 and VKORC1 remarkably affects the metabolism of warfarin. This study aims to identify the CYP2C9 and VKORC1 genotypes of 96 Vietnamese patients suffering cardiodynia or myocardial infarction and establish their daily warfarin dose. The PCR-RFLP method was used to identified the CYP2C9*2, CYP2C9*3 and VKORC1 alleles. The result indicated that allelic frequencies for CYP2C9*3 were observed at 3% of investigated patients while CYP2C9*2 alleles and genotypes were not detected in this study population. Allele frequency of VKORC1 (c. -1639GA) was observed at 84%. Base on the CYP2C9 and VKORC1 genotypes, we recommended the daily warfarin dose for of these patients
Enhanced bioremediation of crude oil polluted water by a hydrocarbon-degrading Bacillus strain immobilized on polyurethane foam
No full textDuring the production and transportation of petroleum hydrocarbons, unsuitable operation and leakage may result in contamination of water and soil with petroleum hydrocarbons. Petroleum contamination causes significant marine environmental impacts and presents substantial hazards to human health. Bioremediation of contaminated water and soil is currently the effective and least harmful method of removing petroleum hydrocarbons from the environment. To improve the survival and retention of the bioremediation agents in the contaminated sites, microbial cells must be immobilized. It was demonstrated that immobilized microbial cells present advantages for degrading petroleum hydrocarbon pollutants compared to free suspended cells. In this study, the ability of a Bacillus strain (designed as Bacillus sp. VTVK15) to immobilize on PUF and to degrade crude oil was investigated. The immobilized Bacilllus strain had the highest number (5.38 ± 0.12 Í 108 CFU/g PUF) and a maximum attachment efficiency of 92% on PUF after 8 days. Analysis by GC-MS revealed that both free and immobilized cells of Bacillus sp. VTVK15 were able to degrade 65 and 90% of the hydrocarbons in 2% (v/v) crude oil tested after 14 days, respectively. The results suggest the potential of using PUF-immobilized Bacillus sp. VTVK15 to bioremediate petroleum hydrocarbons in an open marine environment
Honeybee products as potential bioindicators of heavy metals contamination from Northern Vietnam
No full textContamination of heavy metals (As, Cd, Hg, Pb and Sn) in honeybee products (Apis cerana) from Northern Vietnam is determined. The study was carried out in two main harvesting seasons of beekeeper farms (April and October), over two years (2018-2019). A total of 72 samples from 24 honeybee hives from 8 provinces and one city were collected. The results showed that the quality of three products in nearly all research sites were met the standards in accordance with the national technical regulation on the limits of heavy metal contamination in food of the Vietnamese Health Ministry, except for the pollen and beeswax from HY2 site. The concentration of Pb was most notably value in this study, which was determined at fairly high levels in pollen (3,767 mg/kg) and beeswax (5,840 mg/kg) from HY2 site. This can be a warning for this metal significant contamination in the habitat. Specially, Hg was not detected in most samples or only recorded without significant. For the environmental types, the mean value of As and Sn in all honeybee’s product types in semi-rural area were higher than that in rural area. Thus, the detection of the heavy metals proves that honeybee’s products could be good indicators to detect the environmental contaminants and monitor the habitat quality of a particular are
STUDY ON SLUDGE TREATMENT BY THE AEROBIC STABILIZATION PROCESS COMBINES WITH BULKING AGENT AND HEATED AIR SUPPLY
No full textThe paper presents the results of the evaluation of sludge decomposition ability from a municipal wastewater treatment plant by an aerobic process on the Mishimax device (MK-50). The principle of the process was based on the microorganisms activated by the bulking agent as a bio-carrier to decompose organics composition and increase the evaporation by heating. An average sludge amount of 30 kg/day was added into MK-50, with the moisture of 80.2 – 83.6 %, with the C/N ratio of around 22 - 35. The heated air with 50 oC in temperature was supplied into a rotary bioreactor during the experiment period. After every 30 days of fermentation, the results from three experiments showed that the sludge volume decreased from 83 - 85 %, the stabilization efficiency by dry weight of sludge reached at 32 - 39 %, corresponding to the average decomposition rate is 12 g/kg.day, the evaporation efficiency was more than 95 %. Sludge after stabilization process had the colour of brown-grey, pH of about 6.5 - 7.2, the humus particles with the size of less than 1 mm accounted for over 60 %, the evaluation of product indexes according to nutrients like TOC, T-N meet the standard of 10TCN 526:2002/BNNPTNT. The stabilized sludge was used for growth plant test and compared to a market organic fertilizer under the same conditions of cultivation and monitoring. The initial results of this study were a basis for research of sludge treatment technology approaches to waste recycling orientation in urban areas in Vietnam
Comparision of several secondary metabolite and elemental ion contents of leaves from Kandelia obovata and Sonneratia caseolaris forests located in the Red River delta
No full textThe two mangrove species Kandelia obovata and Sonneratia caseolaris were widely planted in the Red River delta. Both K. obovata and S. caseolaris forests play an important role in the economic development and environmental protection of the delta. However, chemical responses of the common mangrove forests to different ecological conditions in the delta have not yet been described. In this study, we evaluated chemical responses of K. obovata and S. caseolaris through comparisons of the content of metabolites and element ions in leaves of mangrove plants located under different ecological conditions in the Red River delta. In the low salinity area (Thuy Truong), specific leaf areas of K. obovata and S. caseolaris were much lower while the succulent index was higher compared to those in the high salinity area (Kim Trung). In Kim Trung, both species had a lower ratio of chlorophyll a/chlorophyll b. K. obvata in lower light (under the S. caseolaris canopy) had lower levels of chlorophyll b, resulting in a higher Chla/chlb ratio. There was no difference in the Mg content of leaves between two areas. An increase in Na content in leaves of mangrove plants in the higher salinity area was evident. The high K/Na ratio in leaves were eveluated for both species in high salinity areas. Our results also showed better uptake of K in leaves of S. caseolaris growing in the low salinity conditions (Thuy Truong), i.e. Thuy Truong has more favourable ecological conditions for S. caseolaris. Carotenoid contents in leaves of both species growing in the higher salinity were lower.