Science and Technology Development Journal - Natural Sciences 2020-09-18T13:42:24+00:00 Phuc Van Pham Open Journal Systems A review of COVID-19: Molecular basis, diagnosis, therapeutics and prevention 2020-09-18T13:42:21+00:00 Mai T. N. HUYNH Phuc H. T. NGUYEN Hieu H. C. PHAN Nghia T. H. PHAN Kong H. LE Nhu T. H. TRUONG Khanh LE Dung V. HO Vy T. NGUYEN Ha L. B. TRAN Hieu V. TRAN Hoang H. NGUYEN Nhan T. NGUYEN Thuoc L. TRAN <p>Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the confirmed viral pathogen of COVID-19, a pandemic originated from Wuhan, China at the end of 2019. Since then, SARS-CoV-2 has rapidly spread across the globe with over 8 million confirmed cases and more than 430.000 deaths worldwide as of mid-June 2020. Similar to other strains of coronavirus, the envelope of SARS-CoV-2 comprises of three structural proteins: S protein (spike), E protein (envelope) and M glycoprotein (membrane). SARS-CoV-2 capsids are spherical or pleomorphic. Each capsid contains a positive-sense single-stranded RNA (+ssRNA-Class IV-Baltimore) associated with nucleoprotein N. The viral RNA genome is approximately 30 kb in length and contains 14 open reading frames (ORFs). The binding affinity of the viral S protein to the ACE2 (angiotensin-converting enzyme 2) receptor facilitates the attachment of SARS-CoV-2 to human epithelial cells. Upon binding, SARS-CoV-2 spike protein is cleaved and activated by TMPRSS2 (transmembrane protease, serine 2) or by cathepsin L at the cleavage site S2', and also by furin at the cleavage site S1/S2. The furin cleavage motif RR_R is a notable feature, firstly found in SARS-CoV-2 S protein, which may increase virus transmission rate. This feature and many others might result from several evolution events in SARS-CoV-2 genome. These events could occur when coronaviruses, including SARS-CoV-2, spread from one host to another. They can be causative to high virulence and transmission rate of future coronavirus strains, which may require the development of newer vaccine generations. To understand of SARS-CoV-2’s structure, infection mechanism, diagnosis, treatment, and vaccine development strategies, a review of current literature is of highly importance to disease control in Vietnam.</p> 2020-07-01T00:00:00+00:00 ##submission.copyrightStatement## The second-order composed radial derivatives of perturbation mappings of parametric set-valued optimization problems 2020-09-18T13:42:24+00:00 Phạm Lê Bạch Ngọc Nguyen Thanh Tung Nguyen Huynh Nghia <p>In the paper, we study the generalized differentiability in set-valued optimization, namely stydying the second-order composed radial derivative of a given set-valued mapping. Inspired by the adjacent cone and the higher-order radial con in Anh NLH et al. (2011), we introduce the second-order composed radial derivative.&nbsp; Then, its basic properties are investigated and relationships between the second-order compsoed radial derivative of a given set-valued mapping and that of its profile are obtained. Finally, applications of this derivative to sensitivity analysis are studied. In detail, we work on a parametrized set-valued optimization problem concerning Pareto solutions.&nbsp; Based on the above-mentioned results, we find out sensitivity analysis for Pareto solution mapping of the problem. More precisely, we establish the second-order composed radial derivative for the perturbation mapping (here, the perturbation means the Pareto solution mapping concerning some parameter). Some examples are given to illustrate our results. The obtained results are new and improve the existing ones in the literature.</p> 2020-07-01T00:00:00+00:00 ##submission.copyrightStatement## Heterologous expression of human KGF/FGF7 (Keratinocyte growth factor) in Pichia pastoris 2020-09-18T13:42:23+00:00 Thư Anh Nguyễn Phạm Trang Thị Thuỳ Nguyễn Nghĩa Hiếu Nguyễn Thao Thi Phuong Dang <p>Keratinocyte Growth Factor (KGF) is a paracrine-acting and epithelium-specific growth factor produced by cells of mesenchymal origin, play an important role in promoting proliferation, differentiation, motility of epithelial cells and stimulating regeneration of damaged epithelial tissues. Recent studies indicated that recombinant KGF is produced in many different expression systems such as bacteria, insect cells, plant and mammalian cells. However, KGF’s yields obtained from these systems is low and production’s cost is high especially in mammalian cells. In this study, the yeast <em>Pichia pastoris</em> was chosen as a host for KGF expression through induction of methanol by promoter AOX on pPICzαA vector system. The results demonstrated that the <em>Pichia pastoris</em> X33:<em>kgf</em>&nbsp; transformants secreted KGF directly into BMMY medium after inducing by 0.5% methanol. The recombinant protein was purified by heparin affinity chromatography with the yield of 1.35 mg/l and the purity of 99.89% showed by SDS-PAGE. In addition, MTT assay showed the purified recombinant KGF had a proliferation effect on A549 cell line since A549 known as a cell has KGF’s receptor.</p> 2020-07-01T00:00:00+00:00 ##submission.copyrightStatement## Synthesis of various 2-benzylbenzoxazole derivatives catalyzed by deep eutectic solvent-supported onto magnetic nanoparticles 2020-09-18T13:42:19+00:00 The Thai Nguyen Phuong Hoang Tran <p>Magnetic nanoparticle supported deep eutectic solvents have been synthesized by preparing and grafting [Urea]<sub data-id="subscript-1">4</sub>[ZnCl<sub data-id="subscript-2">2</sub>] deep eutectic solvent onto the surface of silica-coated Fe<sub data-id="subscript-3">3</sub>O<sub data-id="subscript-4">4 </sub> magnetic nanoparticles using 3‐ chloropropyltrimethoxysilane as a linker. DES@MNP was fully characterized using scanning and transmission electron microscopies, Fourier transforms infrared, energy-dispersive X-ray spectroscopies, vibrating sample magnetometer X-ray diffraction, and thermogravimetric analysis. In this study, we have developed the synthesis of 2-benzylbenzoxazole via condensation reaction of 2-nitrophenols and acetophenones using a magnetic nanoparticle supported [Urea]<sub data-id="subscript-5">4</sub>[ZnCl<sub data-id="subscript-6">2</sub>] deep eutectic solvent as a novel, green and efficient catalyst. In the presence of 1,4-diazabicyclo[2.2.2]-octane, elemental sulfur acted as an excellent reductant in promoting oxidative rearranging coupling in this reaction. The reaction has been conducted via the stirring method and the reaction conditions were surveyed (16 h, 130 °C, acetophenone, 2-nitrophenol, DABCO and sulfur molar ratio of 2:1:1:3, 10 mol% DES@MNP catalyst). Six 2-benzylbenzoxazole derivatives have been synthesized via this method with good yield (86-91%). The structure of the pure product has been confirmed through FT-IR, <sup data-id="superscript-1">1</sup>H NMR, <sup data-id="superscript-2">13</sup>C NMR, and GC-MS methods. More importantly, DES@MNP has been separated from the reaction mixture by a magnet and reused over five consecutive runs without significant loss of catalytic activity.</p> 2020-08-14T00:00:00+00:00 ##submission.copyrightStatement## Performance of non-orthogonal multiple access downlink system using the Log-Likelihood ratio 2020-09-18T13:42:18+00:00 Khoa Le Dang Thanh Hai Ngo Nghia Thai Cong Nguyen <p>Non-orthogonal multiple access (NOMA) is one of the potential technologies for fifth generation (5G) cellular networks. This technique can combine with other techniques such as Orthogonal Frequency Division Multiplexing (OFDM) and Multiple Input Multiple Output (MIMO). In NOMA downlink, signals from multiple users are superposed in time-frequency domain. Hence, NOMA systems have a larger throughput than orthogonal multiple access systems. There are several schemes for NOMA detection. The successive interference cancellation (SIC) is commonly used to decode desired signals at the receivers. Some NOMA schemes with SIC are ideal SIC, symbol-level SIC and codeword-level SIC. The previous studies showed that the log-likelihood ratio (LLR) has a performance as ideal SIC. In this paper, we derive the bit error rate for a NOMA downlink system with 2 users (UE) using LLR receiver. This study considers the system over a Rayleigh fading channel and the presence of Additive White Gaussian Noise. The closed-form equations have been proposed for each user with QPSK mapping. The simulation results show that the performance of the system is consistent with the proposed formula</p> 2020-08-16T00:00:00+00:00 ##submission.copyrightStatement## Determining facies distribution trend in order to update geological modeling ILBH 5.2 reservoir, lower miocene, Rong Trang Field, Block 16-1 Cuu Long Basin 2020-09-18T13:42:13+00:00 Nguyễn Tuấn Trần Văn Xuân Trần Văn Trị Phan Vương Trung Đỗ Quang Khánh Trương Quốc Thanh Nguyễn Xuân Khá Phạm Việt Âu <p>Dòng dầu khí thương mại được phát hiện tại tập cát kết 5.2U, mỏ Rồng Trắng lô 16-1 trầm tích Miocen hạ bể Cửu Long. Tuy nhiên tầng chứa thường là tập hợp các vỉa mỏng, bất đồng nhất. Trên cơ sở xác định nguồn gốc của vật liệu, điều kiện biến đổi của môi trường, chế độ động lực của quá trình vận chuyển, bối cảnh địa hóa môi trường lắng đọng và tạo đá, công trình làm sáng tỏ quy luật phân bố tướng đá tầng chứa. Việc áp dụng phương thức tiếp cận tổng hợp địa chấn, tài liệu thạch học, mẫu lõi và địa vật lý giếng khoan kết hợp với ứng dụng mô hình địa chất phân giải cao cho phép chính xác hoá quy luật phân bố tướng đá của tập ILBH 5.2. Kết quả nghiên cứu tập đã phân loại thành công tướng đá chủ yếu ứng với môi trường thành tạo: Môi trường sông gồm tướng tướng trầm tích lòng sông, trầm tích vỡ đê và trầm tích ven sông phân bố theo phương từ Tây – Đông đến Bắc Tây Bắc – Nam Đông Nam, trong đó vùng Bắc – Tây Bắc đá chứa có chất lượng tốt nhất, theo phương Đông Nam là các tướng trầm tích lòng hồ, trầm tích cát ven bờ và trầm tích cát xa bờ được hình thành trong môi trường hồ và tại ranh giới giữa 2 môi trường đá chứa có chất lượng cao hơn cả. Cơ chế hình thành thành hệ trầm tích chứa dầu khí tuổi Miocen của lô 16-1 nói riêng, khu vực Trung Bộ phức tạp, để có thể dự đoán xu thế phân bố tiềm năng của thành hệ này, cần tiến hành đánh giá vai trò của phức hệ macma trong quá trình thành tạo thành hệ chứa dầu khí tuổi Miocen.</p> 2020-09-06T13:55:29+00:00 ##submission.copyrightStatement## Antioxidant and hepatoprotective potentials of miliusa velutina stem bark extract 2020-09-18T13:42:17+00:00 Đái Thị Xuân Trang Hieu Le Trung Bui Linh Chi Tran Danh Thai Luu Tuan Trong Nguyen <p>Miliusa velutina (MV) stem bark has various medicinal uses, but its hepatoprotective effect has not yet been studied. This study investigated the antioxidant and hepatoprotective activity of the ethanol extract of MV stem bark against carbon tetrachloride (CCl<sub>4</sub>)-induced liver injury. The ethanol extract of MV stem bark was evaluated for in vitro antioxidant activity which exhibited good antioxidant activity in terms of ferric reducing-antioxidant power assay (EC<sub>50, FRAP</sub>=4.04±0.00 µg/mL), total antioxidant capacity assay (EC<sub>50, TAC</sub>=8.73±1.08 µg/mL) and 1,1-diphenyl-2-picrylhydrazyl (EC<sub>50, DPPH</sub>=9.33±0.07 µg/mL) radical scavenging assay. Mice were pretreated with CCl<sub>4</sub> (2.5 mL/kg body wight per day) in 4 consecutive weeks. After one hour taking CCl<sub>4</sub> by oral administration, mice were treated with the ethanol stem bark extract of MV at various concentrations of 100, 200, and 400 mg/kg body weight. The MV stem bark at the dose of 400 mg/kg body weight effectively reduced the level of alanine transaminase (38±6.78 U/L) and aspartate transaminase (AST) in serum. Besides, the MV stem bark at the dose 400 mg/kg body weight reduced the malondialdehyde (3.12±1,19 nM MDA/g tissue) level, and increased the activity of reduced glutathione (896.21±22.69 nM GSH/g tissue) in liver. The observation of the microscopic cross section of liver tissue also revealed that the mice treated with stem bark extract of MV at the dose of 200 and 400 mg/kg body weight had significantly improvement in liver tissues compared to the non-treated control group. Histological analyses of the MV-treated group exhibited reducing inflammatory process and preventing liver necrosis and fibrosis. In summary, the hepatoprotective effect of MV stem bark was seemingly associated with its antioxidant activity.</p> 2020-08-16T00:00:00+00:00 ##submission.copyrightStatement## Evaluating the possibility of color treatment of Tarcon Blue 2BLN dye by coagulating materials PGa21Ca, polyaluminium chloride, iron (II) sulfate heptahydrate and aluminium sulfate octadecahydrate 2020-09-18T13:42:16+00:00 Le Thi Xuan Thuy Le Thi Suong <p>This article presented the results of color treament ability of Tarcon Blue 2BLN dye with some flocculation chemicals such as PGa21Ca, polyaluminium chloride (PAC), iron (II) sulfate heptahydrate (FeSO4.7H2O) and aluminium sulfate octadecahydrate (Al2(SO4)3.18H2O). Our results showed that conditions for treatment the color to reach column B, QCVN 13: 2015 / BTNMT (national technical regulation on textile and dying industry) by different flocculation chemicals were the same exposure time (10 minutes), sedimentation time (30 minutes), but different in parameters of concentration (% mass), stirring speed and pH. Specifically: PGa21Ca (0.02%), PAC (0.01%), aluminium sulfate octadecahydrate (0.003%) can handle color at the initial pH of the solution (pH = 6), with the stirring speed corresponding to each flocculation chemical at 120 rpm, 45 rpm and 45 rpm respectively. In contrast, with iron (II) sulfate heptahydrate (0.02%), only the color treatment reaches column B, QCVN 13: 2015 / BTNMT when the pH of the wastewater raises to 10 and stirring speed is 120 rpm. Compared with PAC, aluminium sulfate octadecahydrate and iron (II) sulfate heptahydrate, PGa21Ca has the advantage of contributing to raise the pH value in the acid solution, which reduces the pH in the base environment, and not changing the pH when the concentration of PGa21Ca increases. Test results on actual wastewater samples taken from Hoa Khanh Danang Textile Joint Stock Company (DANATEX) showed that the ability of treating color of these chemicals on actual wastewater samples is lower than the ability on water samples blended with Tarcon Blue 2BLN dye.</p> 2020-08-16T00:00:00+00:00 ##submission.copyrightStatement## Effects of some precursors and elicitors on the growth and α-glucosidase inhibitory activity of in vitro Urena lobata L. hairy roots 2020-09-18T13:42:12+00:00 Phuong Thi Bach Vu Dai Minh Cao Phuong Ngo Diem Quach <p>Recent studies have demonstrated the potential of <em>in vitro</em> <em>Urena lobata</em> L. hairy roots to inhibit α-glucosidase for supporting the treatment of type 2 diabetes. To increase the productivities of hairy roots with α-glucosidase inhibitory activity in <em>in vitro</em> culture conditions, this study focus on the effects of some metabolic factors such as precursors (L-phenylalanine, L-tyrosine) and elicitors (chitosan, methyl jasmonate, salicylic acid). They were added to the culture media to investigate the growth and α-glucosidase inhibitory activity of <em>Urena lobata</em> L. hairy roots. The results showed that for the effects of precursors, only phenylalanine (1 µM) increased root biomass with the highest of α-glucosidase inhibitory activity on the 25th day of culture. In contrast, tyrosine did not play any role in increasing the biomass and α-glucosidase inhibitory activity in <em>Urena lobata</em> L. hairy roots. For the effects of elicitors, only chitosan (50 mg/L) resulted in hairy roots with α-glucosidase inhibitory activity higher than the control after 3 days in culture medium. Other elicitors such as methyl jasmonate, salicylic acid had lower α-glucosidase inhibitory activity than the control. The results of this study demonstrated the potential of phenylalanine and chitosan in increasing the productivity of <em>in vitro</em> hairy roots with higher α-glucosidase inhibitory activity in <em>Urena lobata</em> L.</p> <p>&nbsp;</p> 2020-09-11T01:40:16+00:00 ##submission.copyrightStatement## The ultrasound accelerated solvent-free synthesis of ethyl 7-methyl-5-phenyl-5H-thiazolo[3,2-a]pyrimidine-6-carboxylate through Biginelli reaction catalyzed by Amberlyst-15 2020-09-18T13:42:15+00:00 Công-Thắng Dương Xuan Thi Thi Luu <p>Multi-component reactions (MCRs) played an important role to produce complex molecular structures in a one-step process. Among all MCRs reported, Biginelli reaction was one of the most well-known and used in organic synthesis to constitute pyrimidine scaffolds. Therefore, a solvent-free Biginelli reaction of 2-aminothiazole, benzaldehyde and ethyl acetoacetate catalyzed by Amberlyst-15 (A-15) had attracted us to pay attention and to do research in order to highly obtain a desired product, a frame of thiazolo[3,2-a]pyrimidine being present in many active biological compounds. Amberlyst-15, polystyrene resin regarded as a green acidic solid, available commercial, inexpensive and reusable catalyst had been firstly and successfully developed for solvent-free Biginelli reaction under ultrasound irradiation to form thiazolo[3,2-a]pyrimidine. Most factors which had influenced on the reaction conversion and yield such as the molar ratios between 2-aminothiazole, benzaldehyde and ethyl acetoacetate, the amounts of catalyst A-15, and reaction time had been investigated. Consequently, the yield of ethyl 7-methyl-5-phenyl-5H-thiazolo[3,2-a]pyrimidine-6-carboxylate had been also found to depend on the amount of the acidic solid catalyst and little excess amounts of the two reactants, e.g. 2-aminothiazole and ethyl acetoacetate. The maximum yield has been obtained 76% after six-hour ultrasound irradiation at 80oC with the molar ratio of 2-aminothiazole : benzaldehyde : ethyl acetoacetate (1.4:1.0:1.4) and 50 mg of catalyst A-15. The results showed that Amberlyst-15 had high capability of recovery and recycling owing to the inconsiderably changes of product yields after two recycle runs.</p> 2020-08-24T00:00:00+00:00 ##submission.copyrightStatement##