Vietnam Academy of Science and Technology: Journals Online
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Fort-Dauphin beach sands, south Madagascar: natural radionuclides and mineralogical studies
No full textThe Fort-Dauphin beach sand placer occurs as black sands on the East-South of Madagascar. The placer contributes 2/3 of the total heavy mineral resources of this country. The major minerals of the deposit are monazite, zircon, quartz, garnet, spinel, sillimanite as non-refractory minerals; ilmenite, anatase, rutile, titanite, leucoxene, pseudorutile and as a refractory one. The average concentration of the ilmenite, monazite, zircon and other minerals is 66.72%, 2.3%, 2.8%, and 28.18% respectively. Ilmenite contains 63 wt.% of TiO2, Zircon - 44 wt.% of ZrO2, Monazite contains 53 wt.% of oxide rare earth elements (REE) and up to 2 wt.% of UO2 and 9 wt.% of ThO2. The total REE in the studied samples was observed high concentration up to 16000ppm and a high ratio of Σ LREE/Σ HREE31. The principal natural radionuclide in this placer is 232Th with the concentration of 232Th from 2710 to 6000 ppm, 3620 ppm on average while for the 238U from 124 to 340 ppm, 237 ppm on average which are higher than the average of their in Earth’s crust 360 and 70 times respectively
Towards a sustainable economic governance in the East Sea
No full textThe East Sea and its resources play a crucial role in Vietnam’s 2030 and vision to 2045 development agenda. This new “marine economy” model brings with its enormous opportunities, but also challenges that need to be address for its effective implementation especially under the complex geopolitical situation in the East Sea. Based on information from the last three decades, this paper describes the status and potential of marine economic sectors in Vietnam and suggests steps to maximize benefits and towards a sustainable development. It outlines options for responding to the challenges at national, regional and international levels. They include: (i) Coordination of coastal and marine economic sectors, integrated ecosystem - based management practices, and a broad consensus among Vietnamese public, (ii) Mutually beneficial cooperation for the development of marine economic sectors and programs among ASEAN countries, and finally, (iii) Compliance with international law and conventions. Such an approach will contribute to a harmonious and sustainable use of the East Sea for the benefit of the people in ASEAN nations, and of the world at large
Impact of the precise ephemeris on accuracy of GNSS baseline in relative positioning technique
No full textFor advanced geodesy tasks that require high-accuracy, such as tectonics, surveying services usually use not only long-baselines but also the duration of tracking GNSS satellites in a long (e.g., 24/7). The accuracy of these baselines in baseline analysis is dominated by inaccuracy satellite positioning and orbit, leading to specified accuracy may not be adequate. One way to overcome this problem is to use the final precise ephemeris, provided by IGS. The objective of this study is to investigate the impact of precise ephemeris on the accuracy of GNSS baselines in relative positioning techniques in two aspects: baseline length and duration of tracking GNSS satellites. To this end, 197 baselines were generated from a total of 88 CORS stations in South Korea, and then thirteen testing cases were constructed by grouping baseline lengths from under 10 km to over 150 km. Besides, data for one day of each CORS was divided into the different duration, such as 1, 2, 3, 6, and 24 hours. The GNSS measurements have been processed by TBC software with an application of the broadcast and precise ephemerides. The precision of the baseline processing from two types of ephemeris was analyzed about baseline lengths and time of data. The obtained results showed that using precise ephemeris significantly improved the accuracy of baseline solutions when the length of the baseline larger than 50km. In addition, this accuracy is independent of the length of baselines in the case of the precise ephemeris. Finally, the result of the testing baselines was enhanced when the duration of tracking data increases
Diversity of micro-fungi associated with aerobic composting process of organic wastes
No full textOrganic waste is gradually degraded during composting process, producing carbon dioxide, water, heat, and humus, the relatively stable end product. The degradation process is carried out by living organisms, of which fungi appear to have the most important role since they break down tough debris (cellulose, lignin, and other resistant materials), enabling other microorganisms to continue the decomposition process. In Binh Duong province, municipal organic wastes, recently, being treated by aerobic composting process at industrial scale. In order to properly control the biological composting process and maximize its efficiency, the understanding of involved microorganisms is essential. Therefore, the objective of this study was to isolate and identify the fungi associated with large scale municipal biosolid waste composting process in Vietnam. In this study, we have isolated 10 morphologically different fungal strains from the composting materials, and classified based on morphological characteristics and 18S rDNA sequences. The results showed that these fungal strains belonged to four different genera, including Aspergillus, Penicillium, Monascus, and Trichoderma. Our observation is in consistent with previous study, which found that Aspergillus, Penicillium are dominant fungi in composting materials due to their able to survive high temperatures and break down variety of bio-solid wastes. Beside of that, the two other genera Trichoderma and Monascus are widely known for their ability to break down lignin-rich materials which difficult for biodegradation. The results would be a useful reference for further studies of diversity, and functions of fungi that involved in municipal biosolid waste composting process in Vietnam environmental conditions
Efficiency of shoot regeneration and micropropagation of purple passion fruit (Passiflora edulis Sims.) via internodal longitudinal thin cell layer culture
No full textThe thin cell layer culture technique (TCL) has been used for the effective tissue culture of several dozen plants with commercial importance such as field crops (rice, cereals), horticultural commodities (fruits, vegetables, ornamental plants), medicinal plants and herbs (Panax vietnamensis Ha et Grushv.), and even forestry trees (Pinus sp.), and woody fruit plants (Citrus spp., apple). In the present, TCL was used to evaluate the efficiency of shoot regeneration and propagation for purple passion fruit (Passiflora edulis Sims.). The internodes were cut longitudinally (lTCL) and was used as an initial material. The results showed that the shoot regeneration rate and number of shoots from internode-lTCL depended on position of internodes (1, 2, 3, 4 and 5) and the plant growth regulator (BA and NAA). After 8 weeks of culture, internode-lTCL derived from 3rd internode of P. edulis cultured on MS medium supplemented with 1.5 mg/L BA in combination with 1.0 mg/LNAA gave the highest shoot regeneration rate (83.33%), and number of shoots (3.00 shoots/explant). These shoots were cultured on modified MS (MSM) medium supplemented with 1.0 mg/L BA showed higher efficiency of shoot multiplication (3.56 shoots/explant and 6.67 cm height) than the other BA treatments. In addition, the highest rooting rate was 76.67% when cultured on MSM medium containing 2.0 mg/L IBA. The survival rate of plantlets was 83.33% when transferred into greenhouse condition after 10 weeks. The results of this study were the initial success in establishing an effective in vitro regeneration and propagation of Passiflora edulis Sims. through internode-lTCL
Effects of in vitro maturation media on in vitro fertility of porcine oocytes and early development of embryos
No full textIn pigs, embryo productivity is still lower than that in other livestocks. One of the reasons is incomplete maturation of porcine oocytes in in vitro conditions. Therefore in vitro maturation (IVM) plays a crucial role in in vitro production of porcine embryos. It provides prerequisite condition to in fertilization and subsequent development of porcine embryos. In a previous study, effects of NCSU-37-based medium and TCM-199-based media supplemented with porcine follicular fluid (pFF) or Fetal Bovine Serum (FBS) on in vitro maturation of Landrace oocytes collected in Vietnam have been compared, suggesting that NCSU-37 medium supplemented with 10% of porcine follicular fluid (pFF) had the highest rate of oocytes reach to metaphase II stage in comparison to those of the other two TCM-199-based media. In the present study, further experiments were carried out to evaluate the contribution of IVM media on fertilization capability and developmental competence. Porcine oocytes matured in vitro in 3 media: NCSU-37 supplemented with 10% pFF, TCM-199 supplemented with either 10% pFF or 10% FBS were subjected to in vitro fertilization and subsequent in vitro culture to monitor fertility and embryo development. The results showed that penetration and normal fertilization rates in both TCM-199 groups are both higher than that of NCSU-37 group. Moreover, the cleavage and blastocyst rates, and cell numbers of blastocysts which is a criterion for embryo quality were all higher in TCM-199 groups, especially in the group supplemented with pFF. It might be concluded that TCM-199 media supplemented with either pFF or FBS are suitable for effective in vitro maturation of Landrace porcine oocytes collected in Vietnam
Increasing the somatic embryogenesis frequency of Panax vietnamensis Ha et Grushv. by disinfection of leaf explant using nano silver and the addition of nano silver in culture medium
No full textSomatic embryo is a developmental method for mass multiplication of valuable medicinal plants. In this study, leaf explants of Ngoc Linh ginseng were disinfected with nano silver at different concentrations and exposure times to eliminate infectious agents and induce embryogenic callus for the production of somatic embryos. The results show that the lowest contamination rate (20.00%) was observed when leaf explants were treated with 0.5 g/L nano silver for 15 minutes while the highest embryogenic callus induction rate (72.22%) and fresh weight (0.77 g) was determined at 0.2 g/L nano silver for 20 minutes. High frequency of somatic embryogenesis formation and germination were occurred on MS medium supplemented 1.0 mg/L 2,4-D; 0.5 mg/L NAA; 0.2 mg/L Kin and 1.6 mg/L nanosilver. After 8 weeks of culture, the number somatic embryos derived from nano silver treated-leaves was increased 2 times than non-treated explants. Addition of 1.0 mg/L NAA and 1.2 mg/L nano silver was showed the highest shoot and root length, root number, fresh and dry weight of plantlets. This research showed that pre-treatment and supplement of nano silver in culture medium is potentially useful for improving embryogenesis frequency, and plantlet formation of Ngoc Linh ginseng cultured in vitro
Effects of explant type, plant growth regulator and cultivation system on multiplication of Polygonum multiflora Thunb. cultured in vitro
No full textPolygonum multiflora Thunb. (Belongs to Polygonaceae family) is a medicinal plant of economic value and should be protected, according to the Red Book of Vietnam. Many studies have shown that P. multiflora Thunb. was effective for many diseases such as hair loss, premature gray hair, lower back pain, knee weakness, muscle weakness, hemiplegia, nervousness, dizziness, insomnia, etc. Propagation and preservation of this herbal species are significantly important because of increased demand. Adventitious root biomass culture has been successful on a number of plant species, and that it has potential for P. multiflorum breeding. In this study, the effect of explants, plant growth regulators and different culture systems on adventitious root formation was investigated. The adventitious roots were induced from the explants and the optimum culture medium were transferred to four different culture systems (3-liter triangular flask, shaking triangle, bioreactor self-made and Korean bioreactor) containing 5 g adventitious roots per 1 liter medium. The results showed that the leaf cultured on SH medium supplemented with 1.5 mg L-1 IBA, 30 g L-1 sucrose, 8.5 g L-1 agar and pH 5.8 gave the higher of adventitious root regeneration rate (100%), root number/explant (25.33 roots), fresh weight (131.67 mg) and dry weight 13.35 mg) compared to those cultured on other condition after 6 weeks of culture. The adventitious root multiplication in the Korea bioreactor system is more effective than other culture systems shown in the fresh biomass (17.04 g), dry biomass (1.56 g) and proliferation rate (3.40 fold) after 6 weeks of culture
On the estimates for the elastic moduli of random Voronoi triclinic polycrystals
No full textOur major new results and the previous ones on the bounds for elastic random polycrystals, and most advanced 3D finite element results for random 3D Voronoi polycrystals are resumed and analysed (together for the first time). Recently obtained numerical Dirichlet and Neumann simulation results for the effective elastic moduli of a large 10000-grain-size random Voronoi polycrystal representative volume element (RVE) for a number of triclinic and monoclinic base crystals (Mursheda and Ranganathan, 2017) are compared critically with the bounds on the moduli. Though major parts within the simulation results fall within the bounds of Pham (2011), some Dirichlet upper estimates still lie outside the bounds. Many more RVEs are needed to represent the Voronoi polycrystal on the same RVE-size-level, and larger RVEs are needed for checking the convergence and comparisons with the bounds