Vietnam Academy of Science and Technology: Journals Online
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OPTIMIZATION AND PURIFICATION OF α-GLUCOSIDASE INHIBITOR FROM BACILLUS SUBTILIS YT20 ISOLATED IN VIETNAM
No full textAmong the treatments of type 2 diabetes, the α-glucosidase inhibitor has been drawing the researcher’s interest world-wide because of safe and convenient mechanism. However, recent α-glucosidase inhibitors have side effects, so alternative sources have been studied to limit the side effects and provide more options for the treatment of type 2 diabetes. In this study, after selecting morioorganism strains capable of biosynthesis of α-glucosidase inhibitor from the collection of Bacillus subtilis, we have isolated B. subtilis YT20 which inhibited α-glucosidase above 90%. In detail, this number increased multiply by 1.4 times after the optimization of culture conditions. The α-glucosidase inhibitor activity of B. subtilis YT20 yield the molecular weight of 163 Da after purified by a combination of salting out, filter membrane with pore size 1000 Da and 100 Da respectively, activated charcoal and chromatography column Sephadex G100, the efficiency peak at 16%. The spectral data indicated that the putative compound isolated from B. subtilis YT20 was 1-deoxynojirimicin. In the thin layer chromatography result, there was an appearance of a single band which corresponds to standard 1-deoxynojirimicin (Sigma), followed by a retention factor of 0.34 with a solvent system of isopropanol: acetic acid: deionized water (4:1:1)
The first list of amphibians and reptiles from Soc Son watershed protection forest, Ha Noi City, Vietnam
No full textBased on a new herpetological collection from four field surveys conducted in the Soc Son Watershed Protection Forest, Ha Noi City, from March 2017 to April 2018. We herein provide the first list of 42 species of amphibians and reptiles, in which, 12 species are newly recorded for the herpetofauna of Ha Noi City. In addition, morphological characters of these species are also provided. In terms of conservation concern, two species are listed in the IUCN Red List (2020), five species are listed in the Vietnam Red Data Book (2007), and two species are listed in the Governmental Decree No 06/2019/ND-CP.
Variation of phytoplankton community structure in Quang Ngai coastal waters during 2015–2019
No full textPhytoplankton in coastal waters are important for the evaluation of either biodiversity or environmental impacts because of this highly vulnerable ecosystem. Seasonal and annual changes in the phytoplankton community structure in Quang Ngai waters during the period 2015 to 2019 were analyzed to assess the phytoplankton diversity and reveal possible causes of these changes. A total of 366 phytoplankton taxa belonging to 10 classes were identified throughout this present study. The highest species number was found in 2019 with 295 taxa, followed by those in 2015 (247), 2017 (185), and 2018 (99). The waters of Ly Son transect showed the highest diversity and most stable phytoplankton communities in both dry and rainy seasons, whereas the stations of Quang Ngai coast revealed high variability of the communities. All diversity indices including Margalef, Pielou, Shannon, Simpson did not reflect well differences in average values but a certain degree of variances, indicating possible environmental impacts. During the study time, there were blooms of certain diatom species including Skeletonema spp. in 2015 and Pseudo-nitzschia spp. in 2019. Analysis of a diatoms index, Centric/Pennate ratio, indicated that the waters were in eutrophic status with a decreasing trend from the coast area to Ly Son island in 2015 and 2019. This research built up fundamental data on phytoplankton communities for Quang Ngai province. The Centric/Pennate diatom index and diversity would be used as indicators for environmental changes and their values provided warning of eutrophication in this coastal waters including the water surrounding Ly Son island
Photocurrents in Quantum Wires Including Excitonic Effects
No full textPhotocurrent induced by ultrashort laser pulses in [100]-oriented GaAs quantum wires with square cross section is investigated using the multiband semiconductor Bloch equations with the inclusion of electron-hole interaction. Influences of excitonic effects and quantum confinement effects on the photocurrent are evaluated and discussed
Supercontinuum Generation in Photonic Crystal Fibers Infiltrated with Liquids
No full textIn this paper we present the development of a new direction in so-called optofluidics , namely the research of photonic crystal fibers (PCF) infiltrated with liquids. In particular we concentrate on the flagship application of PCF, the process of Supercontinuum Generation (SG), in which injected monochromatic pulse may be dramatically broadened (spectrally), which creates a coherent beam generation of high brightness comparable to that of monochromatic lasers. The supercontinuum is formed when a collection of nonlinear processes act together upon a pump beam in order to cause severe spectral broadening of the original pump beam. Explanation of this process is based on numerical simulations for Generalized Nonlinear Schrödinger equation (GNLSE) which describes the rich nonlinear dynamics of pulse propagation in nonlinear dispersive media. All nonlinear phenomena involved in SG will be analyzed. We present specially activity of the Polish-Vietnamese Group from the beginning in 2016 to recent time in this domain
APPLICATION OF ULTRASONIC-ASSISTED ENZYMATIC EXTRACTION FOR POLYSACCHARIDES FROM VIETNAMESE RED GANODERMA LUCIDUM AND EXAMINATION OF ANTIOXIDANT ACTIVITY OF THE EXTRACT
No full textCommonly used in Vietnamese traditional remedies, Vietnamese red Ganoderma lucidum (G. lucidum) is an oriental fungus that has long been known for promoting health and longevity. In this study, polysaccharides (PS) were extracted from G. lucidum using ultrasound-assisted enzymatic extraction (UAEE) method, followed by the investigation of seven single-factor experiments namely enzyme ratio between viscozyme and chitinase, total enzyme volume, pH value, extraction temperature, solvent-to-material ratio, ultrasonic power, and extraction time. Based on ultraviolet-visible spectroscopy analysis, the highest PS content could be achieved with a value of 59.71 mg/mL under extraction conditions including the enzyme ratio between viscozyme and chitinase of 3:1, total enzyme volume of 100 µL, pH value of 5.5, extraction temperature of 45 solvent-to-material ratio of 1:25, ultrasonic power of 480 W, and extraction time of 30 min. The extract obtained was then evaluated antioxidant activities by using 2,2-Diphenyl-1-picrylhydrazyl radical scavenging method, showing that the half-maximal inhibitory concentration values were of 1729.64 ± 147.69 µg/mL. As a result, the UAEE method could be regarded as an efficient approach for antioxidant crude polysaccharides content extraction from Vietnamese red G. lucidum
Antioxidant activity of extract from some squid species in Khanh Hoa
No full textThe antioxidant activities against DPPH free radical of crude extracts using ethyl acetate and methanol from ink sac, muscles, and bones of 5 squid species (Uroteuthis chinensis, Uroteuthis sibogae, Uroteuthis duvaucelii, Sepia esculenta, Sepioteuthis lessoniana) collected in Khanh Hoa waters were investigated. These activities ranged from 4.21% (ethyl acetate extract from ink of U. chinensis) to 54.51% (methanol extract from muscle of S. esculenta.). The functional group analysis by infrared adsorption spectrum (FTIR) in these crude extracts revealed the absorption peaks of melanin in ink, polysaccharide in bone and protein in muscle extracts. In addition, the SDS-PAGE result of some methanol extracts showed the presence of proteins with a molecular weight of 30-150 kDa
Size effect of R-TiO (Micro- and Nano-) Particles on the Mechanical Property, Weathering Durability of Water-based Acrylic Coating
No full textThis work aims to clarify the difference between the influence of TiO particles at micrometer and nanometer sizes on the mechanical properties and weathering durability of water-based acrylic coatings. To prepare coatings, micro-R-TiO and nano R-TiO particles with 2 wt.% content were dispersed in the emulsion acrylic polymer by ultrasonic vibration. The coatings without TiO particles, with 2 wt.% micro R-TiO and with 2 wt.% nano R-TiO were tested for abrasion resistance, weathering aging in UV/CON accelerated weathering chamber. Weathering aging was assessed by IR quantitative analysis, the weight loss of the coating. The obtained results showed that the micro R-TiO with the 2 wt.% content enhanced simultaneously the abrasion resistance and weathering durability of water-based acrylic coatings but not as effectively as nano R-TiO. Incorporation of 2 wt.% micro-R-TiO increased slightly the abrasion resistance of coating from 78.4 to 98.9 lite/mil (26% increase) while with addition of nano-R-TiO at the same content, the abrasion resistance was significantly improved from 78.4 to 129.3 lite/mil (65% increase). After 48 aging cycles, the alkane CH groups and weight of the coatings without R-TiO particles, containing 2 wt.% micro-R-TiO, containing nano-R-TiO lost 34.2% and 17.4%; 23.8% and 13%; 13.7% and 13%, respectively
Harnessing Dark Energy in Five-dimensional Brans-Dicke Universe
No full textIn trying to explain the present accelerated expansion of the universe in the light of a five-dimensional Brans-Dicke theory, it is found that the fifth dimension itself here acts as a source of dark energy. It may be taken as a curvature-induced form of dark energy, in one case of which it behaves similar to that form of dark energy arising out of the cosmological constant which is the most commonly accepted form of dark energy. It is also found that this new type of dark energy is free from big rip singularity and may be taken as a viable form of dark energy which can explain some of physical mysteries of the universe