Vietnam Journal of Science, Technology and Engineering

3-6

Authors: Xuan Quan Cao*, Ngoc Dung Hoang, Hoang Luong Nguyen

The development of a luminance responsivity standard is central to the study of photometry and radiometry at the Vietnam Metrology Institute (VMI). Today, two methods are used to determine luminance responsivity. The first method uses an integrating sphere light source, also known as a luminous intensity standard lamp, and the second method compares the luminance responsivity value to that of a known standard photometer. Using these methods, it is possible to identify small uncertainties. In this work, we analysed the luminance responsivity standard system (model: VMI-PR-006) based on the national standard system of luminance (model: V11.04.18). This system was used to calibrate the luminance responsivity scale of standard photometer and luminance standard integrating sphere.When using the national standard system (V11.04.18) to calibrate the luminance standard integrating sphere (model: LN3; S/N:05B840), an uncertainty of U=0.73% for k=2, where k is the *, was found [1]. On the other hand, we calibrated the luminance responsivity scale of a standard photometer system (VMI-PR-006) based on the national standard system of luminance (V11.04.18) and compared it to the luminance responsivity scale calibrated at NMIA (National Measurement Institute Australia) with En=0.13<1, where En is *. This standard system is used for the calibration and verification of measurement devices within the luminance measurement requirements specified by the Vietnam technical documents.

12-18

Authors: Huong Thi Le, Tien Anh Nguyen, Thu Hoang Vo, Michał Michalak, Tam Hoang Luu, Ha Tran Nguyen*

Lanthanum orthoferrite (LaFeO3) photocatalysts were synthesized by a facile and cost-effective co-precipitation method via the hydrolysis of La (III) and Fe (III). The characteristics of LaFeO3 were investigated through thermogravimetric analysis (TGA), X-ray diffraction (XRD), UV-Vis diffuse reflectance spectroscopy (DRS), vibrating sample magnetometry (VSM), and transmission electron microscopy (TEM). During the investigation of the applicability of LaFeO3 as a photocatalyst for the atom transfer radical polymerization (ATRP) of methyl methacrylate monomer under UV irradiation, the obtained poly(methyl methacrylate) exhibited a high molecular weight and narrow polydispersity index. In addition, the LaFeO3 can be recovered via application of a magnetic field and reused for the atom transfer radical polymerization process.

24-29

Authors: Thi Bich Van Pham, Minh Hao Hoang*

A coagulation cascade forms through proteolytic reactions and involves different factors. There are two coagulation pathways, including intrinsic and extrinsic mechanisms, which converge by the formation of factor Xa. Factor Xa plays a crucial role in the formation of the complex with factor Va in the presence of calcium ions and phospholipids. This complex converts prothrombin to thrombin, which leads to the formation of a very strong fibrin clot. Much effort has been devoted to the efficient interference of this enzyme cascade by the inhibition of factor Xa due to its important effect. (R)-3-amidinophenylalanine inhibitors are known inhibitors of factor Xa reported so far. In the present work, a two-dimensional quantitative structure activity relationship (2D-QSAR) was performed on 50 (R)-3-amidinophenylalanine inhibitors (the training set) with respect to their pKi values toward factor Xa, where pKi=-logKi, and Ki is the inhibition constant, to develop a mathematical model that depends on the physicochemical properties of the inhibitors. Partial least squares regression (PLSR) was used to yield a QSAR model containing molecular descriptors that significantly contribute to pKi values. The statistically significant parameters of the model, such as squared correlation coefficient, R2=0.834, root mean square error, RMSE=0.210, cross-validated Q2cv=0.789, and cross-validated RMSEcv=0.237, were obtained for the training set. The developed 2D-QSAR model was applied to predict the pKi values of the 62 inhibitors. Furthermore, the reliability of the model was also confirmed via statistically significant parameters obtained from validation on an external set.

34-37

Authors: Thi Thoi Bui*, Dai Quang Ngo, Van Loc Tran

The paper describes the preparation of new sulfonylurea derivatives from sulfonyl carbamate 6 with amino derivatives. The process for synthesis of the key compound 6 included three steps starting from compound 6-chloronicotinic acid 1, which are readily available chemicals. The compound 1 in the presence of triethylamine in anhydrous acetone solvent and ethyl chloroformate to obtain 6-chloronicotinic (ethyl carbonic) anhydride compound 3. The compound 3 were subsequently reacted with compound 4 to obtain compounds 5. The sulfonamides 5 was refluxed with ethyl chloroformate in present anhydrous potassium carbonate in dry acetone to obtain the key compounds 6. The total yield of the key intermediate compound 6 is about 81.35%, related to the starting materials. Finally, threesulfonylurea derivatives 7a-c were synthesized by condensation of 6 with various of amines in toluene. Their structures have been determined by IR, MS and 1H and 13C NMR spectroscopic methods,and their α-glucosidase inhibitory activity have been evaluated.

41-47

Authors: Ha Lan Nguyen, Viet Ky Nguyen, Van Ngo Dau, Thi Phi Oanh Tran*

Water is extremely important to all life currently, the Cu Chi district has been provided with one hundred percent clean water. However, due to long-standing habits and easy extraction, citizens are still using groundwater daily for water consumption and cooking.Therefore, in this study, the use of groundwater from the middle-upper Pleistocene aquifer in the Cu Chi district of Ho Chi Minh city, for domestic and drinking purposes was investigated. In terms of pH and Fe, NH4+, NO3-, As and Mn content, data were collected from central water supply stations under the operation of the Centre for Rural Water Supply and Sanitation (CERWASS). Furthermore, samples collected from 94 households and water supply stations were also evaluated for groundwater quality via pH and Fe, As, Hg, Cd, Pb, Cr6+ and CN- concentration. On the other hand, a human health risk assessment for carcinogenic substances (As) and non-carcinogenic substances (Mn) was performed by a variety of assessments including the susceptibility to contamination according to the DRASTIC index, which weights water risks by applying a semi-quantitative model. Because pollution is inevitable with today’s modernization and industrialization, these research results contribute to management and control measures deeply needed to achieve and maintain a safe water supply, thereby ensuring the health and safety for the communities in the Cu Chi district

56-64

Authors: Duy Tue Nguyen, Tri Nhut Do*

Solar energy is a free and nearly endless source of energy. Vietnam has the advantage of harnessing solar energy for many essential purposes because of its geographic location in the tropics. This allows electricity usage to be minimized in solar chemistry and energy conversion from solar energy into electricity; or to completely replace electricity usage in applications such as heating, cooling, ventilation, water treatment, cooking processes, and heating processes. In this paper, three solar water heating systems with a heat pump are designed for resorts located at three famous tourist destinations in Vietnam: Phu Quoc island and the towns of Bao Loc, and Sa Pa. These places represent the Southern, Central, and Northern regions of Vietnam, respectively. Ecotect and Grasshopper software applications are employed with the latest weather, heat, and radiation data and was obtained from climate.onebuilding.org. Data analysis is based on Ecotect software and the computational design is done in Grasshopper software. These software applications show that Phu Quoc island is the most efficient place to exploit solar energy, followed by Bao Loc, which is lower due to the fog, and Sa Pa, where solar radiation is low. In order to increase the water heating efficiency in places with very low solar radiation, a heat pump is considered along with a conventional solar water heating system and optimum azimuth angle of 180o South for the solar collector. This method is an efficient solution that can be applied in Sa Pa as well as in other places in Vietnam where there is a lack of solar radiation. The solar energy factor (SEF) is significantly increased from 14.37 to 57.47 and the solar fraction (SF) per year is increased from 93.5 to 98.3% using this method.

71-76

Authors: Le Thi Quyen, Nguyen Thi Minh Thu, Le Thi Minh Phuong, Nguyen Thi Trang*

The objectives of this work were to accurately evaluate testing kits that analyse sperm DNA fragmentation in infertile men and to provide a comparison of an improved testing kit (SSSperm testing kit) to the existing Halosperm testing kit in an analysis of sperm DNA fragmentation. A cross-sectional study was conducted on 300 semen samples from infertile men with a sperm concentration ≥1 million/ml using the Bland-Altman, T-test, and Pearson test for statistical study. The SSSperm testing kit had a coefficient of variation of CV%=2.26%<5% and ttn=0.970.05). In conclusion, the SSSperm testing kit for the analysis of sperm DNA fragmentation is qualified as determined from quantitative tests, and the SSSperm testing kit is equivalent to the Halosperm testing kit.

83-88

Authors: Van-Tuan Tran*, Tao Xuan Vu

Penicillium digitatum exists in nature as a causative agent of green mould disease in citrus fruits at the postharvest stages. Inspections of the molecular mechanism of the host invasion by P. digitatum usually require suitable selection markers for genetic manipulation. In this study, we recruited the phleomycin resistance gene as a selection marker for the genetic transformation of P. digitatum using Agrobacterium tumefaciens. The results showed that the growth of the wild strain P. digitatum PdVN1 from fungal spores is quite sensitive to phleomycin and is inhibited at a concentration of 50 μg/ml, whereas growth from fungal mycelium is more tolerant and completely suppressed at a concentration of 200 μg/ml. Under optimised conditions, the A. tumefaciens-mediated transformation (ATMT) efficiency of P. digitatum with the phleomycin resistance marker could reach over 1000 transformants per 106 spores. All the tested transformants presented the integration of T-DNA in their genomes and were mitotically stable for the phleomycin resistance. Furthermore, the results also revealed the success for heterologous expression of the DsRed fluorescent gene in the fungus, in which the strong red fluorescent signal could be observed over the whole fungal mycelium and spores. Our work demonstrates for the first time that the phleomycin resistance gene can serve as a reliable selection marker for A. tumefaciens-mediated transformation of the postharvest pathogen P. digitatum. This selection marker can be exploited for T-DNA insertional mutagenesis and for functional investigations of target genes involved in citrus decay by P. digitatum.