http://stdj.scienceandtechnology.com.vn/index.php/stdj/issue/feed Science and Technology Development Journal 2020-11-30T14:41:13+00:00 Phuc Van Pham pvphuc@vnuhcm.edu.vn Open Journal Systems http://stdj.scienceandtechnology.com.vn/index.php/stdj/article/view/2449 Triterpenoids and coumarins from the leaves of Sterculia foetida Linn. 2020-11-30T14:40:25+00:00 http://stdj.scienceandtechnology.com.vn/public/journals/2/article_2449_cover_en_US.png Pham Nguyen Kim Tuyen phamvanphuc2308@gmail.com Nguyen Thi Quynh Trang phamvanphuc2308@gmail.com Huynh Cong Doan phamvanphuc2308@gmail.com Pham Dinh Thuong phamvanphuc2308@gmail.com Nguyen Trung Duan phamvanphuc2308@gmail.com Tran Doan Duy Cuong phamvanphuc2308@gmail.com Huynh Bui Linh Chi phamvanphuc2308@gmail.com Nguyen Thi Anh Tuyet phamvanphuc2308@gmail.com Nguyen Kim Phi Phung phamvanphuc2308@gmail.com Thu Thi-Hoai Nguyen hoaithudhyd@gmail.com <p><strong>Introduction</strong>: Sterculia foetida Linn. is widely distributed in tropical countries. As the continuous study on the hexane and ethyl acetate extracts of Sterculia foetida leaves, the isolation and structural determination of four triterpenoids and two coumarins were addressed.</p> <p><strong>Method</strong>: The crude extract was prepared from dried power of Sterculia foetida leaves by maceration method in ethanol. This extract was then separated by liquid-liquid partition with n-hexane, chloroform, and ethyl acetate, respectively, to obtain the corresponding extracts. The hexane and ethyl acetate extracts were applied to multiple silica gel column chromatography to yield six compounds. Their chemical structures were determined by the NMR data analysis as well as the comparison their spectroscopic data and physical properties with those of reported literature.</p> <p><strong>Results</strong>: Four triterpenoid compounds, including betulinic acid (1), conyzasaponin G (2), taraxerol (3), and taraxer-14-ene- 1a,3b -diol (4), and two coumarins fraxetin (5), and aesculin (6) were identified.</p> <p><strong>Conclusion</strong>: To the best of our knowledge, they have not been reported in the leaves of Sterculia foetida before, and compound 2 was known to present in Sterculia genus for the first time.</p> 2020-10-25T14:36:53+00:00 ##submission.copyrightStatement## http://stdj.scienceandtechnology.com.vn/index.php/stdj/article/view/2442 Potential applications of waste lignin from the paper and pulp industry in Viet Nam 2020-11-30T14:41:13+00:00 http://stdj.scienceandtechnology.com.vn/public/journals/2/article_2442_cover_en_US.png Thanh Khoa Phung ptkhoa@hcmiu.edu.vn Quynh-Thy Song Nguyen songthyy204@gmail.com Khanh B. Vu vbkhanh@hcmiu.edu.vn Giang Duy-Le Vo vdlgiang@hcmiu.edu.vn Vinh Ngoc Nguyen nnvinh@hcmiu.edu.vn <p>The conversion of waste lignin from the paper and pulp industry is a potential process to produce chemicals and materials in the industry. With the development and the demand for the pulp and paper industry, the amount of waste lignin will increase remarkably. In Vietnam, the forest tree for the pulp industry is abundant, and the pulp industry has increased in recent years. In parallel, the government planned to develop the material resource and high-tech factories for this industry. In this work, we summarized the pulp and paper industry in Vietnam, then suggest the potential applications of waste lignin in several valuable products.</p> 2020-10-09T00:00:00+00:00 ##submission.copyrightStatement## http://stdj.scienceandtechnology.com.vn/index.php/stdj/article/view/2426 On the calm b-differentiability of projector onto circular cone and its applications 2020-11-30T14:40:59+00:00 http://stdj.scienceandtechnology.com.vn/public/journals/2/article_2426_cover_en_US.png Vo Duc Thinh vdthinh@dthu.edu.vn <p>In this paper, we study a concept on the calm B-differentiability, a new kind of generalized differentiabilities for a given vector function introduced by Ye and Zhou in 2017, of the projector onto the circular cone. Then, we discuss its applications in mathematical programming problems with circular cone complementarity constraints. Here, this problem can be considered to be a generalization of mathematical programming problems with second-order cone complementarity constraints, and thus it includes a large class of mathematical models in optimization theory. Consequently, the obtained results for this problem are generalized, and then corresponding results for some special mathematical problems can be implied from them directly. For more detailed information, we will first prove the calmly B-differentiable property of the projector onto the circular cone. This result is not easy to be shown by simply resorting to those of the projection operator onto the second-order cone. By virtue of exploiting variational techniques, we next establish the exact formula for the regular (Fréchet) normal cone (this concept was proposed by Kruger and Mordukhovich in 1980) to the circular cone complementarity set. Note that this set can be considered to be a generalization of the second-order cone complementarity set. In finally, the exact formula for the regular (Fréchet) normal cone to the circular cone complementarity set would be useful for us to study first-order necessary optimality conditions for mathematical programming problems with circular cone complementarity constraints. Our obtained results in the paper are new, and they are generalized to some existing ones in the literature.</p> 2020-10-10T00:00:00+00:00 ##submission.copyrightStatement## http://stdj.scienceandtechnology.com.vn/index.php/stdj/article/view/2455 Photocatalytic activity enhancement for removal of dye molecules based on plasmonic Ag grafted TiO2 nanocubes under visible light driven 2020-11-30T14:40:01+00:00 http://stdj.scienceandtechnology.com.vn/public/journals/2/article_2455_cover_en_US.png Ton Nu Quynh Trang tnqtrang@hcmus.edu.vn Le Thi Ngoc Tu lethingoctu87@gmail.com Tran Van Man tvman@hcmus.edu.vn Vu Thi Hanh Thu vuthihanhthu1979@gmail.com <p><strong>Introduction</strong>: Finding a novel photocatalyst for photocatalytic degradation operating in the wavelength range from UV to visible light has been considered a great potential for environmental remediation. Herein, TiO<sub>2</sub> nanocubics (NCs) decorated Ag nanoparticles (NPs) with various concentrations were developed.</p> <p><strong>Methods</strong>: The crystal structure, morphological and chemical characteristics of prepared photocatalysts were thoroughly analyzed by a series of main analyses (X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDX), and UVVis spectra).</p> <p><strong>Results</strong>: The results revealed that a significantly promoting visible-light photocatalytic behavior of TiO<sub>2</sub>NCs@Ag photocatalyst was observed. The photocatalytic methyl orange (MO) degradation of the as-synthesized Ag anchored TiO<sub>2</sub>NCs photocatalyst (85% and 62% under UV light and visible light, respectively) exhibited outstanding photocatalytic efficacy compared with pristine TiO<sub>2</sub> NCs. The achieved results could be assigned to the synergistic effects between TiO<sub>2</sub>NCs and Ag- NPs, leading to enhanced charge carrier separation and improved absorption ability in visible-light response.</p> <p><strong>Conclusion</strong>: This work facilitates designing and developing high-efficiency heterostructure photocatalysts for practical works related to environmental deterioration.</p> 2020-11-08T00:00:00+00:00 ##submission.copyrightStatement## http://stdj.scienceandtechnology.com.vn/index.php/stdj/article/view/2417 Comparing atmospheric trace element accumulation of three moss species 2020-11-30T14:40:13+00:00 http://stdj.scienceandtechnology.com.vn/public/journals/2/article_2417_cover_en_US.png Doan Phan Thao Tien phamvanphuc2308@gmail.com Le Hong Khiem phamvanphuc2308@gmail.com Trinh Thi Thu Trinh phamvanphuc2308@gmail.com Marina Vladimir Frontasyeva phamvanphuc2308@gmail.com Nguyen Thi Minh Sang phamvanphuc2308@gmail.com Son An Nguyen sonna@dlu.edu.vn <p><strong>Introduction</strong>: The intention of Vietnam to participate in the European-Asian Moss Survey in the framework of The United Nations Economic Commission for Europe - International Cooperative Programme on effects of air pollution on natural vegetation and crops (UNECE ICP Vegetation) necessitates choosing appropriate moss species that grow in the tropical and subtropical climate of Vietnam. The three selected moss species, divided into phytogeographical elements, were as follows: <em>Leucobryum (aduncum, albidum), Hypnum commutatum</em> and <em>Barbula indica</em>.</p> <p><strong>Methods</strong>: The present study focuses on Central Vietnam where 18 samples of the three above moss species were collected in the vicinity of Dalat and Hue cities. Elements in the moss samples were detected by neutron activation analysis (NAA) at the IBR-2 reactor of the Division of Neutron Activation Analysis, Frank Laboratory of Neutron Physics, Joint Institute for Nuclear Research in Dubna, Russia.</p> <p><strong>Results</strong>: The analytical results for twenty-three trace elements, which were used to study elemental accumulation abilities of the three moss species in the air, were Na, Mg, Al, Cl, K, Ca, Ti, V, Mn, Fe, Co, Zn, As, Br, Rb, Sr, Sb, I, Cs, Ba, La, Th, and U. The accumulation abilities were found to decrease in the following order: <em>Leucobryum &gt; Hypnum &gt; Barbula</em>. However, Leucobryum, because of its short stem, was not judged to be a suitable candidate for biomonitoring.</p> <p><strong>Conclusion</strong>: The element accumulation abilities of <em>Hypnum</em> moss were better than those for <em>Barbula</em>, but both were comparable and could be used as indicators for air deposition monitoring; however, <em>Hypnum</em> was not widely present in Vietnam. Thus, <em>Barbula indica</em> moss could be used for performance of atmospheric deposition monitoring in Vietnam.</p> 2020-11-08T00:00:00+00:00 ##submission.copyrightStatement## http://stdj.scienceandtechnology.com.vn/index.php/stdj/article/view/2432 Global research trends in coronavirus disease 2019 2020-11-30T14:40:40+00:00 http://stdj.scienceandtechnology.com.vn/public/journals/2/article_2432_cover_en_US.png Thai Thanh Tran thanhthai.bentrect@gmail.com Luu Thanh Pham thanhluupham@gmail.com <p><strong>Introduction</strong>: The outbreak of the novel coronavirus disease 2019 (COVID-19) is an ongoing global epidemic incident. The present study aims to bibliometrically analyze the global research trends of scientific papers related to COVID-19 with regard to the number of publications, subject categories, and prolific countries. A total of 47,061 publications, published during the last seven months, were collected and analyzed in this study.</p> <p><strong>Methods</strong>: The bibliometric data in this study, which was extracted from the LitCovid Hub from January 17 to July 31, 2020.</p> <p><strong>Results</strong>: Our results indicate that the number of publications on COVID-19 has increased significantly from January to July 2020, along with the rapid spread of the infection. China has produced the largest number of research papers on COVID-19 (5,751 articles, accounting for 12.2%), followed by the USA (2,005 publications, accounting for 4.3%) and Italy (1,374 publications, accounting for 2.9%). Most recent research papers have focused on prevention, treatment, and diagnosis. Our results reveal that although the most affected countries are the USA, Brazil, India, and many countries in Europe, their contribution to research about COVID-19 has been limited.</p> <p><strong>Conclusion</strong>: More research in the field of prevention, diagnosis, and treatment from highly affected countries is recommended. Overall, this study not only provides a global status update on COVID-19 scientific literature but also contributes to future research.</p> 2020-10-10T00:00:00+00:00 ##submission.copyrightStatement##