Vietnam Journal of Science, Technology and Engineering

3-9

Authors: Hue Thi Dao*, Tung Duc Vu

Building an integrated river delta basin and coastal management plan in the context of climate change requires suspended sediments data, which plays an important role and is the key component for understanding the hydrology regime in the delta region. Sediments are responsible for carrying a considerable amount of nutrients and contaminants. Most sediment discharge data is acquired by surveys/data collection activities or by mathematical modelling. However, these methods are costly, time-consuming, and complex. Therefore, in this study, the authors investigate the potential use of satellite observations (MODIS reflectance) to detect suspended sediment flux in the Red river delta (RRD) of Vietnam. The relationships between discharge (Q), suspended sediment concentration (SSC), and total load (L) collected from the three in-situ stations Son Tay station (ST), Thuong Cat station (TC), and Hanoi station (HN) in the RRD are determined by regression analyses of reflectance data (R) obtained from MODIS bands 1-2 (250-m resolution). The results present a close connection between the monthly average of SSC and R and a good statistical relationship between the monthly average of Q and R in HN. At TC and ST, a lower correlation was found compared to HN because of the cloud cover and the position where data was collection in the river. The coefficient of determination ranged from 0.11 to 0.40 for the R-SSC and R-Q relationships. A method of estimating SSC and L at a single point along the river using data from Q and R was proposed based on the relationship correlation results.

15-18

Authors: Nguyen Thanh Le*, Huu Giap Tran, Thi Kim Oanh Vu, Thuy Duong Pham, Ngoc Thuc Dinh, Anna Stojakowska, Bich Ngan Truong

Maesa membranacea A. DC. (Myrsinaceae) has been traditionally used for the treatment of fever and hepatitis. The phytochemical investigation of Maesa membranacea stems has led to the isolation of six compounds including kaempferol (1), (-)-epicatechin (2), betulinic acid (3), p-hydroxybenzoic acid (4), vanilic acid (5), and protocatechuic acid (6). The chemical structures of these compounds have been determined by nuclear magnetic resonance (NMR), mass spectrometry (MS) data, and by comparison with previously reported works. This is the first report of a chemical study on Maesa membranacea as compounds 1-6 listed above were found from the Maesa genusfor the first time.

26-32

Authors: Thi Tuyet Mai Phan*, Ho Viet Cuong, Pham Ngoc Lan

Carboxymethyl cellulose-graft-poly(acrylic acid-Sodium acrylate-acrylamide) SAPs have been prepared by the free-radical grafting solution polymerization of acrylic acid (AA) and acrylamide monomers (AM) onto carboxymethyl cellulose (CMC) in the presence of N,N′-methylenebisacrylamide as a crosslinker (MBA) and ammonium persulfate (APS) as an initiator. Various factors influencing the water absorbency of the polymer were studied. These include the weight ratio of APS, MBA, and CMC compared to the monomers. The optimal conditions were found as follows: 1% APS, 0.25% MBA, and 10% CMC (weight ratio to monomers). The maximum absorbencies for distilled water and 0.9 wt.% NaCl solution were 406 g/g and 69 g/g, respectively. The structure of the synthesized polymer was confirmed by Fourier Transform Infrared spectroscopy (FTIR). Additionally, the water absorption and water retention behavior of the polymer in soil were investigated. The results showed that this polymer could be employed as a suitable moisture-holding additive in soil for cultivation purposes.

38-44

Authors: Vu Thi Thu Nga*, Gilbert Teyssedre

Cable technologies have evolved in different ways for applications using high voltage alternating current (HVAC) and high voltage direct current (HVDC) over the last 40 years. Since the 1950s, mass-impregnated paper was progressively replaced by extruded insulation made of polyethylene and then cross-linked polyethylene (XLPE). The switch from paper insulation to extruded cables went on continuously while cables were designed with ever increasing voltage requirements. However, regarding space charge build-up and field redistribution, particularly at polarity reversal stages in thyristors, the behaviour of extruded cables under such DC stress is not fully understood. For this reason, material improvement, characterization, and modelling are still intensively researched for cables, accessories, and power conversion equipment. The weaknesses and methods used to simulate the characteristics of insulation are presented and compared in this work through the simulation results of the macroscopic and fluid model.

49-55

Authors: N.N. Quynh*, B.H. Hieu, N.N. Dang, N.H. Quang, To Vinh Cuong

n recent years, the construction of upstream reservoirs and the extraction and structural construction activities on the river banks and beds have caused downstream changes in river morphology and hydrological regime of the Red river system, which has especially accelerated from 2000 to 2018. These dramatic variations have significantly changed the morphological characteristics and relationship between the flow and morphology that are a fundamental parameter to evaluate the stability of the channels. In this study, the morphological characteristics and relationship between flow and morphology over some periods as well as under current conditions were analysed. This work provides basic river training parameters for studying river training planning of the Red river system in general and for the Red and Duong river sections in Hanoi in particular.

62-67

Authors: Ha Duc Chu*, Quynh Thi Ngoc Le, Yen Hai Thi Hoang, Thu Phuong Pham, Hong Viet La, Nguyet Minh Thi Nguyen, Anh Xuan Duong, Thao Duc Le, Linh Hung Le, Hoi Xuan Pham

SWEET (Sugars Will Eventually be Exported Transporter) proteins are well known to play pivotal roles in the growth and development of plants. Here, we report the presence of 43 members of the AhSWEET family in peanut (Arachis hypogaea) and determine their general characteristics including chromosomal localization, gene structure, and numerous physical and chemical features of the proteins. We found that the AhSWEET genes were unevenly distributed among the peanut’s 20 chromosomes. The AhSWEET proteins were hydrophobic with a grand average hydropathicity >0 while a majority of the proteins were basic with isoelectric points >7.0. Additionally, most of the AhSWEET genes contained 6 exons and 5 introns. The expression profiles of the AhSWEET genes were explored based on the previous transcriptome atlas. Interestingly, we found that the AhSWEET genes exhibited differential expression patterns across various organs and tissues during the growth and development of peanut plants. Our study provides a solid foundation of the AhSWEET gene family for further functional characterization of AhSWEET genes in the regulation of peanut growth and development

70-75

Authors: Vu Xuan Tao*, Tran Bao Tram, Nguyen Thi Hien, Thai Hanh Dung, Tran Van Tuan

Vietnam possesses an abundant and highly diverse resource of plants. Therefore, the search and evaluation of bioactive compounds extracted from these plants are a potential research direction to support developing products that improve human health. The purpose of this study is to assess the antifungal activity of some essential oils produced by materials harvested in Vietnam such asKing orange peel (Citrussinensis),lemongrass (Cymbopogonflexuosus), peppermint(Mentha arvensis), and betel leaf (Piperbetle). The antifungal effect of these essential oils was determined by the Kirby-Bauer disc diffusion technique. In addition, the antifungal properties of the essential oils were also assessed through their effects on the reproduction ofC. albicansand the spore germination, mycelium elongation, and sporulation ofA. fumigatus. The results demonstrated that all peppermint, lemongrass, and betel leaf essential oils showed antifungal activity againstC. albicansandA. fumigatus. Especially, betel leaf essential oil could perform antifungal activity at a low dilution concentration of 10% and could also inhibit the reproduction of C. albicansand the spore germination, mycelium elongation, and sporulation of A. fumigatus. Meanwhile, orange peel essential oil did not exhibit any antifungal properties.

83-89

Authors: Thuong Quoc Thinh, Truong Tran Nguyen Sang, Tran Quoc Viet, Le Thi Minh Tam, Nguyen Phuoc Dan, Emilie Strady,Kieu Le Thuy Chung*

Microplastic pollution has become a global issue in recent years. Since the early 2000s, scientists have investigated the occurrence of microplastics (MiPs) in the environment. While research on marine MiPs is more advanced at present, there are immense gaps of knowledge regarding continental MiPs. Airborne MiPs are one source of MiPs in the aquatic environment. In the scientific literature, there have been only three publications on presence of MiPs in atmospheric fallout. In developing countries, where plastic waste management is weak, studies on the presence of MiPs in this area are limited. This current study presents a preliminary assessment of the presence of MiPs in atmospheric fallout sampled from the Phuoc Hiep landfill, Ho Chi Minh city (HCMC). The results of this work show that MiP concentrations vary between 1,801 items m-2d-1 and 913 items m-2d-1 in the dry and rainy seasons, respectively.