Science and Technology Development Journal 2019-05-21T00:38:21+00:00 Phuc Van Pham Open Journal Systems In vitro α-glucosidase inhibitory activity of compounds isolated from mangrove Lumnitzera littorea leaves 2019-05-21T00:38:21+00:00 Thuy Thi Le Nguyen Thuy Thi Pham Poul Erik Hansen Phung Kim Phi Nguyen <p><strong>Introduction</strong>: Lumnitzera littorea grown at CanGio Mangrove Forest has been investigated. The present study reports the isolation, characterization and evaluation of the alpha-glucosidase inhibitory activity of isolated compounds from Lumnitzera littorea leaves.</p> <p><strong>Methods</strong>: Their structures were elucidated by spectroscopic methods (including MS, 1D and 2D–NMR) and comparison with values from the literature. From the n-hexane extract, nine compounds including lupeol (<strong>1</strong>), betulin (<strong>2</strong>), betulinic acid (<strong>3</strong>), oleanolic acid (<strong>4</strong>), corosolic acid (<strong>5</strong>), -sitosterol (<strong>6</strong>), beta-sitosterol 3-O- beta-D-glucopyranoside (<strong>7</strong>), stigmast-5-ene-3beta-O-(6-O-hexadecanoyl-beta-D-glucopyranoside) (<strong>8</strong>), and stigmast-4-ene-3-one (<strong>9</strong>) were isolated and identified.</p> <p><strong>Results</strong>: The results of the alpha-glucosidase inhibitory activity showed thatcorosolic acid (5) and oleanolic acid (4) were the most potent, with IC<sub>50</sub> values of 17.86 +/- 0.42 and 18.82 +/- 0.59 ug/mL, respectively. Five of the other seven compounds exhibited inhibitory activity with IC<sub>50</sub> values below 100 ug/mL, and higher than the positive control acarbose (127.64 +/- 0.64 ug/mL).</p> <p>&nbsp;</p> 2019-01-07T00:00:00+00:00 ##submission.copyrightStatement## Physical and electrochemical properties of mixed electrolyte 1-ethyl-3-methylimidazolium Bis(trifluoromethanesulfonyl)imide and ethylene carbonate as electrolytes for Li-ion batteries 2019-05-21T00:38:17+00:00 Linh Thi-My Le Thanh Duy Vo Hoang Van Nguyen Quan Phung Man Van Tran Phung My Loan Le <p><strong>Introduction</strong>: Ionic liquids (ILs) have become a prospective candidate to replace the conventional electrolytes based on the volatile organic-solvents in lithium-ion batteries. However, the drawbacks of high viscosity and low ionic conductivity have restricted the high rate capacity and energy density in practical batteries. With the aims to resolve these problems and design a safe electrolytes with high electrochemical stability, mixtures of ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl) imide (EMITFSI) with different amounts of ethylene carbonate (EC) was prepared and characterized as electrolytes for Li-ion batteries.</p> <p><strong>Methods</strong>: In this work, we investigated four factors to demonstrate the performance of EMITFSI as electrolytes for Li-ion batteries. These factors include: thermal properties of mixed electrolytes (Mettler Toledo DSC1 Star -DSC, Q500-TGA), Conductivity (HP- AC impedance spectroscopy), Viscosity (Ostwald viscometer CANNON) and electrochemical window (cyclic voltammetry-MGP2 Biologic Instrument). All experiments were repeated three times with the exception of TGA-DSC methods.</p> <p><strong>Results</strong>: The study indicated that 20 % wt. ethylene carbonate (EC) when mixed with EMITFSI could significantly decrease the electrolyte viscosity while improving ionic conductivity and maintain similar electrochemical stability as pure ionic liquid. Lithium diffusion coefficient of mixed electrolytes was lower than commercial electrolytes based on conventional solvents, however, the thermal stability was enhanced.</p> <p><strong>Conclusion</strong>: EMITFSI can be used to replace conventional carbonate-based liquids as a high-performance electrolyte for Li-ion batteries.</p> <p>&nbsp;</p> 2019-02-25T00:00:00+00:00 ##submission.copyrightStatement## The necessary and sufficient conditions for a probability distribution belongs to the domain of geometric attraction of standard Laplace distribution 2019-05-21T00:38:14+00:00 Tran Loc Hung Phan Tri Kien <p>The geometric sums have been arisen from the necessity to resolve practical problems in ruin prob- ability, risk processes, queueing theory and reliability models, <em>etc</em>. Up to the present, the results related to geometric sums like asymptotic distributions and rates of convergence have been investigated by many mathematicians. However, in a lot of various situations, the results concerned domains of geometric attraction are still limitative. The main purpose of this article is to introduce concepts on the domain of geometric attraction of standard Laplace distribution. Using method of characteristic functions, the necessary and sufficient conditions for a probability distribution belongs to the domain of geometric attraction of standard Laplace distribution are shown. In special case, obtained result is a weak limit theorem for geometric sums of independent and identically distributed random variables which has been well-known as the second central limit theorem. Furthermore, based on the obtained results of this paper, the analogous results for the domains of geometric attraction of exponential distribution and Linnik distribution can be established. More generally, we may extend results to the domain of geometric attraction of geometrically strictly stable distributions.</p> <p>&nbsp;</p> <p>&nbsp;</p> <p>&nbsp;</p> 2019-03-29T05:16:25+00:00 ##submission.copyrightStatement## Physical-chemical and electrochemical properties of sodium ion conducting polymer electrolyte using copolymer poly(vinylidene fluoride- hexafluoropropylene) (PVDF-HFP)/ polyethylene oxide (PEO) 2019-05-21T00:38:12+00:00 Thanh Duy Vo Trung Minh Phung Hoang Quoc Duy Hoang Truong Linh Thi My Nguyen Oanh Hoang Nguyen Phung My Loan Le <p><strong>Introduction</strong>: Polymers acting as both an electrolyte and a separator are of tremendous interest because of their many virtues, such as no leakage, flexible geometry, excellent safe performance, and good compatibility with electrodes, compared with their liquid counterparts. In this study, polymer electrolyte membranes comprising of poly(vinylidene fluorine-co-hexafluoropropylene) [PVDF-HFP] were plasticized with different mass ratios of poly(ethylene oxide) (PEO) in 1 M NaClO4/PC solutions, and were prepared and characterized in sodium-ion battery.</p> <p><strong>Methods</strong>: Polymer electrolyte membranes were prepared by solution-casting techniques. The membranes' performance was evaluated in terms of morphology, conductivity, electrochemical stability, thermal properties and miscibility structure. The following various characterization methods were used: Scanning Electron Microscopy (SEM), impedance spectroscopy (for determination of electrolyte resistance), cyclic voltammetry, thermal degradation analysis, and infra-red spectroscopy (for determination of structure of co-polymer).</p> <p><strong>Results</strong>: It was indicated that the PVDF-HFP/PEO membrane with 40 % wt. PVDF-HFP absorbed electrolytes up to 300 % of its weight and had a roomtemperature conductivity of 2.75 x 10<sup>-3</sup> Scm<sup>-1</sup>, which was better than that of pure PVDF-HFP. All polymer electrolyte films were electrochemically stable in the potential voltage range of 2-4.2 V, which could be compatible with 3-4 V sodium material electrodes in rechargeable sodium cells.</p> <p><strong>Conclusion</strong>: The PVDF-HFP/PEO polymer electrolyte film is a potential candidate for sodium-ion battery in the potential range of 2-4.2 V.</p> <p>&nbsp;</p> 2019-03-29T09:00:04+00:00 ##submission.copyrightStatement## Stability of solution of a backward problem of a time-fractional diffusion equation with perturbed order 2019-05-21T00:38:15+00:00 Nguyen Minh Dien Dang Duc Trong <p>The aim of this paper is of studying the stability of solution of a backward problem of a timefractional diffusion equation with perturbed order. We investigate the well-posedness of the backward problem with perturbed order for t&gt;0. The results on the unique existence and continuity with respect to the fractional order, the source term as well as the final value of the solution are given. At t=0 the backward problem is ill-posed and we introduce a truncated method to regularize the backward problem with respect to inexact fractional order. Some error estimates are provided in Holder type.</p> <p>&nbsp;</p> 2019-03-29T00:00:00+00:00 ##submission.copyrightStatement## Chemical constituents of the lichen Dendriscosticta platyphylloides, Lobariaceae 2019-05-21T00:38:09+00:00 Dung Thi My Nguyen Lien Thi My Do Huynh Thi Ngoc Tuyet Minh Ky Quang Ho Hai Tuan Nguyen Jacques Mortier Phung Kim Phi Nguyen <p><strong>Introduction</strong>: Dendriscosticta is a new genus belong the Sticta wrightii group of the family Lobariaceae. This genus of foliose lichen is widely distributed in tropical regions worldwide. The lichen Dendriscosticta platyphylloides is very abundant in Bidoup forest, Lam Dong province, Vietnam.</p> <p><strong>Methods</strong>: The structure of these compounds was elucidated through the interpretation of their 1D and 2D-NMR and HR-MS data. The cytotoxic activities of these compounds against liver hepatocellular carcinoma (HepG2), human lung cancer (NCI-H460), human epithelial carcinoma (HeLa) and human breast cancer (MCF-7) cell lines was performed at the concentration of 100 mg/mL using the sulforhodamine B (SRB) assay.</p> <p><strong>Results</strong>: In this paper, we reported the isolation of six known compounds, including (<strong>1</strong>) 15a-acetoxyhopan-22-ol (<strong>2</strong>) hopane-15a,22-diol, (<strong>3</strong>) zeorin, (<strong>4</strong>) cerevisterol, (<strong>5</strong>) salvigenin, and (<strong>6</strong>) 5-hydroxy-3',4',7-trimethoxyflavone.</p> <p><strong>Conclusion</strong>: This is the first time that these compounds are isolated from Dendriscosticta genus. These compounds showed no cytotoxic activity against four cell lines.</p> <p>&nbsp;</p> 2019-03-31T12:44:24+00:00 ##submission.copyrightStatement## On chi-square type distributions with geometric degrees of freedom in relation to geometric sums 2019-05-21T00:38:10+00:00 Tran Loc Hung <p>The chi-square distribution with degrees of freedom has an important role in probability, statistics and various applied fields as a special probability distribution. This paper concerns the relations between geometric random sums and chi-square type distributions whose degrees of freedom are geometric random variables. Some characterizations of chi-square type random variables with geometric degrees of freedom are calculated. Moreover, several weak limit theorems for the sequences of chi-square type random variables with geometric random degrees of freedom are established via asymptotic behaviors of normalized geometric random sums.</p> 2019-03-31T00:00:00+00:00 ##submission.copyrightStatement## The impact of carbon additives on lithium ion diffusion kinetic of LiFePO4/C composites 2019-05-21T00:38:11+00:00 Thanh Dinh Duc Anh My-Thi Nguyen Tru Nhi Nguyen Hang Thi La Phung My Loan Le <p><strong>Introduction</strong>: LiFePO4/C composites were synthesized via physical mixing assisted solvothermal process. Different kinds of carbon materials were investigated including 0D (carbon Ketjen black), 1D (carbon nanotubes) and 2D (graphene) materials. X-rays diffraction patterns of carbon coated LiFePO4 synthesized by solvothermal was indexed to pure crystalline phase without the emergence of second phase. LiFePO4 platelets and rods were in range size of 80-200 nm and dispersed well in carbon matrix. The lithium ion diffusion kinetics was evaluated through the calculated diffusion coefficients to explore the impact of carbon mixing.</p> <p><strong>Methods</strong>: In this work, we studied the structure, morphologies and the lithium ion diffusion kinetic of LiFePO4/C composites for Li-ion batteries. Different characterization methods were used including powder X-rays (for crystalline structure); Transmission Electron Microscopy (for particle and morphologies observation) and Cyclic voltammetry (for electrochemical kinetic study).</p> <p><strong>Results</strong>: The study indicated LiFePO4/C composites were successfully obtained by mixing process and the electrochemical performance throughout the calculated diffusion coefficient was significantly improved by adding the carbon types.</p> <p><strong>Conclusion</strong>: The excellent ion diffusion was obtained for composites LiFePO4/Ketjen black (KB) and LiFePO4/CNT compared to LiFePO4/Graphene. KB could be a potential candidate for large-scale production due to low-cost, stable and high electrochemical performance.</p> <p>&nbsp;</p> 2019-03-31T00:00:00+00:00 ##submission.copyrightStatement## Phenolic compounds from Pamotrema dilatatum growing in Lam Dong province 2019-05-21T00:38:20+00:00 Huy Thuc Duong <p><strong>Introduction</strong>: Only chemical study on the lichen Parmotrema dilatatum was found so far in the world. The lichen Parmotrema dilatatum widely distributed in Lam Dong province, Vietnam has been studied about the isolation and elucidation of several metabolites.</p> <p><strong>Methods</strong>: Phytochemical study on the polar fractions of this lichen was carried out by using various chromatographic methods including thin-layer chromatography and normal phase silica gel chromatography.</p> <p><strong>Results</strong>: Eight phenolic compounds were isolated. The chemical structures of isolated compounds were unambiguously elucidated by NMR spectroscopy and comparison with the data in the literature. These are 8'-O-methylsalazinic acid, salazinic acid, 8'-O-methylprotocetraric acid, diffractaic acid, lecanorin, lecanoric acid, isolecanoric acid, and diorcinolic acid.</p> <p><strong>Conclusion</strong>: Among them, 8'-O-methylsalazinic acid was found as a new natural product.</p> <p>&nbsp;</p> 2019-01-26T02:30:05+00:00 ##submission.copyrightStatement## Long-term expansion enhances the expression of tumor suppressor genes in human bone marrow-derived mesenchymal stem cells 2019-05-21T00:38:16+00:00 Loan Thi Tung Dang Anh Thi Van Bui Nhat Chau Truong Huy Duc Van Phuc Van Pham <p><strong>Introduction</strong>: Mesenchymal stem cells (MSCs) are possibly the most potent type of stem cells for the treatment of many diseases since they possess many advantageous properties, such as abundant source, ease of isolation, and potential to differentiate and trans-differentiate into different types of cells. Although the therapeutic potential of expanded MSCs has been well proven, their biosafety features have not been fully understood. This study aimed to investigate some changes in phenotype and gene expression of bone marrow derived MSCs after long term expansion.</p> <p><strong>Methods</strong>: In this study, expanded mesenchymal stem cells derived from human bone marrow (hBMSCs) were identified for their characteristics (which included morphology, immunophenotype, and differentiation potential) at passages 5, 10 and 15. Moreover, they were evaluated for the expression of various tumor suppressor genes (PTEN, p16, and p53) by real-time RT-PCR.</p> <p><strong>Results</strong>: The results showed that the hBMSCs at passage 15 displayed a change in morphology and a slight reduction of the expression of CD44 and CD90, whereas their potential for adipogenic and osteogenic differentiation was maintained. Moreover, the expression of tumor suppressor genes in the hBMSCs increased after long-term culture.</p> <p><strong>Conclusion</strong>: It could be assumed that prolonged cultures of more than 15 passages drove the hBMSCs into senescence phase. Cultured hBMSCs below passage 10 seemed to be more effective in application because their properties were still preserved.</p> <p>&nbsp;</p> 2019-03-21T22:51:11+00:00 ##submission.copyrightStatement## Copolymerization of n-butyl acrylate/methyl methacrylate in xylene solvent 2019-05-21T00:38:19+00:00 Nguyen-Vu Viet Linh Nguyen Trung Duc Huynh Dai Phu <p><strong>Introduction</strong>: Copolymers are being used in a variety of fields because of their diversity and since any change could result in significant modifications. The butyl acrylate/methyl methacrylate copolymer is an extensively used polymer system with many advantages. This study aims to analyze some changes in copolymerization, from using different time or temperature of synthesis, in order to find an optimal process that can be applied in Vietnam.</p> <p><strong>Methods</strong>: Copolymerization of butyl acrylate/methyl methacrylate copolymer with different butyl acrylate/methyl methacrylate monomer ratios was done using Xylene solvent. Copolymer compositions were determined from the Proton nuclear magnetic resonance spectra and Gel permeation chromatography.</p> <p><strong>Results</strong>: The experimental results indicate that the copolymer was successfully synthesized. The highest molecular weight was 15,591 g/mol, with the lowest dispersity of 1.53 at 100<sup> o</sup>C after 6 hours of copolymerization.</p> <p>&nbsp;</p> 2019-02-17T00:00:00+00:00 ##submission.copyrightStatement## The forming mechanisms of Oligocene combination/stratigraphic traps and their reservoir quality in southeast Cuu Long Basin offshore of Vietnam 2019-05-21T00:38:08+00:00 Chuc Dinh Nguyen Xuan Van Tran Kha Xuan Nguyen Huy Nhu Tran Tan Thanh Mai <p>To date, most of the oil and gas production in Cuu Long Basin (CLB) is contributed from structural traps, making them more and more depleted after years of exploitation. Exploration activities in CLB, therefore, are shifting towards other traps, including stratigraphic and/or combination ones. The results of exploration and appraisal activities in recent years have increasingly discovered more hydrocarbons in the Oligocene section; some of them were discovered in combination/ stratigraphic traps. Many studies on Oligocene targets in Southeast CLB have been carried out but only a few mention nonstructural traps. This leads to uncertainty about the forming mechanisms and distribution, as well as unevaluated hydrocarbon potential of these traps. An integrated approach- utilizing methods of seismic sequence stratigraphy, seismic attribute interpretation, and petrophysical/ petrographical analysis- was applied in this research to identify the forming mechanisms of Oligocene combination/ stratigraphic traps in southeast area of CLB and to evaluate their reservoir quality. The research results show that the key forming factor for stratigraphic traps of sand body is lithology change and the one for pinch-out stratigraphic traps is tapering off of sand layers landward or toward the horsts. The reservoir quality of these traps ranges from moderate to good. By integratedly applying the methods, the forming mechanisms and reservoir quality of Oligocene stratigraphic traps could be delineated. In order to optimize the next-stage exploration strategy in CLB, detailed studies on petroleum system, especially top and bottom seals, and the hydrocarbon potential of these stratigraphic traps, need to be carried out.</p> <p>&nbsp;</p> 2019-04-10T13:25:49+00:00 ##submission.copyrightStatement##