Isolation and identification of phenolic compounds from the leaf extract of Cassia alata L.

Cassia alata is one of the most important species of the genus Cassia which is rich in anthraquinones and polyphenols. This plant is used as a medicinal material of which the leaves are known to have laxative and antibiotic properties. In our study, the methanol leaf extract of C. alata showed a significant antibacterial activity against human pathogenic bacteria strains Staphylococcus aureus and Bacillus cereus. The organic layers such as n-hexane, ethyl acetate, and aqueous layers, were prepared by partitioning the methanol extract with n-hexane and ethyl acetate successively.  We successfully isolated and identified the structures of five compounds from C. alata leaves. Their structures were elucidated by MS and NMR spectroscopic methods as well as comparison with literature data. These compounds were determined to be methyl 2,4,6-trihydroxybenzoate (1), kaempferol (2), (-)epiafzelechin (3), kaempferol-3-O-glucoside (4) and kaempferol-3-O-gentiobioside (5). Keywords. Cassia alata L., epiafzelechin, kaempferol, kaempferol-3-O-glucoside, kaempferol-3-O-gentiobioside

A NEW APPROACH OF SCALE INVARIANCE FOR COMPLEX SYSTEM AND APPLICATION IN POWER LINE COMMUNICATION MODELLING

In the context of the incessant development of sustainable energy and ICT (Information and Communications technology) in power systems, power system becomes more and more intelligent, efficient and economic. However, using electrical infrastructure carrying information communication causes complexities in modeling and simulating. To overcome the problem of modeling, a new approach based on scale invariance theory, scale invariance, is presented in many papers and in various fields. Scale invariance method shows a strong link between a network topology and its performances through a coefficient exponent. In this paper we propose to use this method for modeling power line communication by considering only the input impedance of system. This approach will be tested for not only a general case study but also for an opened circuit without attenuation and bruit. The result is compared with the classical method.

ĐÁNH GIÁ TỔNG HỢP VÀ ĐỊNH HƯỚNG PHÁT TRIỂN HỆ THỐNG 50 ĐẢO VEN BỜ BẮC BỘ VIỆT NAM ( CÓ DIỆN TÍCH TỪ 1KM2 TRỞ LÊN)

Vietnam has about 2,773 islands located in the coastal areas of different seas, including around 100 islands with an area of 1 km2 or more (these islands are large enough for socio-economic development). Northern coastal area has 50 islands with an area of 1 km2 or more, distributed in two provinces Quang Ninh (47 islands), Hai Phong (3 islands). According to a combined assessment of the potential and position of 50 Northern coastal islands for the purpose of economic development, defense and security, 9 islands have been recognized as having the capability of defense and economic development; 6 islands have the advantages of economic development and national defense; 16 islands have the primary function of economic development and 19 islands should focus on their advantages of tourism and agroforestry, which will also be considered as a reserved resource for future island economic development.Tóm tắt: Việt Nam có khoảng 2773 hòn đảo với diện tích 1721 km2, phân bố ở ven bờ các vùng biển khác nhau, trong đó có khoảng 100 đảo có diện tích từ 1km2 trở lên (là các đảo có diện tích đủ lớn để phát triển kinh tế xã hội). Ven bờ Bắc Bộ là nơi tập trung nhiều đảo nhất (2321 đảo), chiếm tới 83,7% tổng số đảo và 48,9% tổng diện tích đảo ven bờ của cả nước và có tới 50 đảo có diện tích từ 1km2 , phân bố ở 2 tỉnh Quảng Ninh (47 đảo), Hải Phòng (3 đảo). Trên cơ sở đánh giá tổng hợp tiềm năng và vị thế của 50 đảo ven bờ Bắc Bộ cho các mục đích phát triển kinh tế và quốc phòng an ninh, đã xác định được 9 đảo có chức năng quốc phòng và phát triển kinh tế; 6 đảo có ưu thế chức năng phát triển kinh tế kết hợp với quốc phòng; 16 đảo có chức năng chủ yếu phát triển kinh tế và 19 đảo có thể khai thác lợi thế để phát triển du lịch và nông lâm nghiệp, cũng như được coi là nguồn lực dự trữ cho phát triển kinh tế biển đảo sau này

Robust Adaptive Cerebellar Model Articulation Controller for 1-DOF Nonlaminated Active Magnetic Bearings

This paper presents a robust adaptive cerebellar model articulation controller (RACMAC) for 1-DOF nonlaminated active magnetic bearings (AMBs) to achieve desired positions for the rotor using a robust sliding mode control based. The dynamic model of 1-DOF nonlaminated AMB is introduced in fractional order equations. However, it is challenging to design a controller based on the model\u27s parameters due to undefined components and external disturbances such as eddy current losses in the actuator, external disturbance, variant parameters of the model while operating. In order to tackle the problem, RACMAC, which has a cerebellar model to estimate nonlinear disturbances, is investigated to resolve this problem. Based on this estimation, a robust adaptive controller that approximates the ideal and compensation controllers is calculated. The online parameters of the neural network are adjusted using Lyapunov\u27s stability theory to ensure the stability of system. Simulation results are presented to demonstrate the effectiveness of the proposed controller.The simulation results indicate that the CMAC multiple nonlinear multiple estimators are close to the actual nonlinear disturbance value, and the effectiveness of the proposed RACMAC method compared with the FOPID and SMC controllers has been studied previously

Gravity terrain correction for mainland territory of Vietnam

Terrain corrections for gravity data are a critical concern in rugged topography, because the magnitude of the corrections may be largely relative to the anomalies of interest. That is also important to determine the inner and outer radii beyond which the terrain effect can be neglected. Classical methods such as Lucaptrenco, Beriozkin and Prisivanco are indeed too slow with radius correction and are not extended while methods based on the Nagy’s and Kane’s are usually too approximate for the required accuracy. In order to achieve 0.1 mGal accuracy in terrain correction for mainland territory of Vietnam and reduce the computing time, the best inner and outer radii for terrain correction computation are 2 km and 70 km respectively. The results show that in nearly a half of the Vietnam territory, the terrain correction values ≥ 10 mGal, the corrections are smaller in the plain areas (less than 2 mGal) and higher in the mountainous region, in particular the correction reaches approximately 21 mGal in some locations of northern mountainous region. The complete Bouguer gravity map of mainland territory of Vietnam is reproduced based on the full terrain correction introduced in this paper

Study change of the performance of airfoil of small wind turbine under low wind speed by CFD simulation

Renewable energy has received strong attention and investment to replace fossil energy sources and reduce greenhouse gas emissions. Quite good and good wind speed areas have been invested in building large-capacity wind farms for many years. The low wind speed region occupies a very large on the world, which has been interested in the exploitation of wind energy in recent years. In this study, the original airfoil of S1010 operated at low wind speed was redesigned to increase the aerodynamic efficiency of the airfoil by using XFLR5 software. After, the new VAST-EPU-S1010 airfoil model was adjusted to the maximum thickness and the maximum thickness position. It was simulated in low wind speed conditions of 4-6 m/s by CFD simulation. The lift coefficient, drag coefficient and $C_{L}$/$C_{D}$ coefficient ratio were evaluated under the effect of the angle of attack and the maximum thickness by using the $k-\epsilon$ model. Simulation results show that the VAST-EPU-S1010 airfoil achieved the greatest aerodynamic efficiency at the angle of attack of 3\,^{\circ}, the maximum thickness of 8\% and the maximum thickness position of 20.32\%. The maximum value of $C_{L}$/$C_{D}$ of the new airfoil at 6 m/s is higher than at the 4 m/s by about 6.25\%.Comment: 19 pages, 21 figure

EVALUATION OF ACUTE AND SUB-ACUTE ORAL TOXICITY OF CLINACANTHUS NUTANS LEAVES EXTRACT IN MICE

Objective: This study aimed to evaluate acute and sub-acute oral toxicity of ethanol extract of Clinacanthus nutans leaves in Swiss mice. Methods: Acute oral toxicity study was performed as per OECD-423 guidelines. Sub-acute oral toxicity study was performed as per OECD-407 guidelines. The extract was dissolved in 10% dimethyl sulfoxide and administered orally, while the control group received only the vehicle. Results: The acute oral toxicity test on mice showed that this extract was well tolerated up to LD50 5000 mg/kg body weight/day oral dosage level and non-toxic to mice under the present experimental conditions. The sub-acute toxicity study was carried out on mice with the oral dosage of the extract from 100 mg/kg–500 mg/kg body weight/day and 5000 mg/kg body weight/day for 28 d. The results showed that this extract did not induce death or adverse effects in activity, feed consumption or body weight gain. There were not significant changes in heamotological and biochemical parameters between control and experiment groups. Conclusion: Thus, Clinacanthus nutans leaf has a very low toxicity value