Vietnam Academy of Science and Technology: Journals Online
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Zooplankton biodiversity in the biosphere reserve of Cu Lao Cham - Hoi An, 2015–2016
Get PDFZooplankton samples in the biosphere reserve of Cu Lao Cham - Hoi An were collected at 20 stations belonging to 3 ecosystems: Mangrove palm - seagrass, transition area and coral reef in rainy season (11/2015) and dry season (6/2016) to determine biodiversity of the biosphere reserve of Cu Lao Cham - Hoi An. 161 species belonging to 16 zooplankton groups were recognized, copepoda was a dominant group with 92 species, followed by cladocera (15 species) and tunicata (13 species). Mangrove palm - sea grass had a different zooplankton structure compared with transition area and coral reef with a lower number of species and similarity index about 40%. The average density of zooplankton in study areas in dry season (24,559 ± 24,700 inds.m-3) were 4 times higher than in rainy season (6,124 ± 6.554 inds.m-3) and dominated by copepoda. The euryhaline cladocera (Bosmina longirostris), freshwater cladocera (Ceriodaphnia rigaudi) and freshwater copepoda (Microcyclops varicans) were dominant in mangrove palm - seagrass ecosystem. Meanwhile, in coral reef ecosystem, the small copepods (genus Oncaea, Oithona) and Tunicata were dominant. Biodiversity indices were low in mangrove - palm and increase from transition area to coral reef ecosystem
Bathymetry mapping using VNREDSAT-1 image: A case study in Ninh Hai coast, Ninh Thuan province of Vietnam
Get PDFBathymetry mapping of coastal zones is one of the minimum requirements to serve related activities as marine management, transportation, construction and scientific application. However, the traditional method of direct measurement in the fields meets problems of time consuming, manpower and money. Applying remote sensing techniques to establish bathymetry in shallow water is an effective method to overcome the traditional problems. The objective of this study is to use VNREDSAT-1 data to map the bathymetry in a coastal region of Vietnam and Ninh Hai coast was selected as a case study in this research. The image was acquired on September 4th, 2013 and preprocessed through atmospheric correction using 6S model and sun glint removal by Hedley method. A total of 3,642 collected data points were divided into two parts, the first part of 2,810 points used to build up the model and the rest of 832 points for validation. The model used is based on multiple regression methods with four independent variables as four bands and a dependent variable as water depth. The results show that the models got high accuracy at the water depth from 10 m to 19 m with root mean square error of 1.03 m to 1.99 m and correlation coefficients of 0.72 to 0.74. This study demonstrates the capacity of VNREDSAT-1 in bathymetry mapping, and it would be an efficient tool for precisely mapping crude bathymetry in Vietnam
PREPARATION OF NICKEL NANOWIRES AND EFFECTS OF SYNTHESIS CONDITIONS ON THEIR MORPHOLOGY
No full textNickel nanostructures prepared by various methods have received considerable attentions due to their numerous applications. In this study, one-dimensional nickel nanowires (NiNWs) were synthesized by the reduction of nickel (II) chloride in polyol medium. Poly (vinylpyrrolidone) (PVP) served as the surfactant and hydrazine hydrate was used as the reductant. The effects of different experimental parameters, i.e. concentration of Ni2+, volume of N2H4, concentration of PVP and reaction temperature on the formation and morphology of NiNWs were studied. The structure, composition and surface morphology of the materials were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The results showed that the morphology as well as the diameter of NiNWs could be effectively controlled by adjusting parameters of the synthesis process
First report on two ostracod genera Loxoconcha Sars, 1866 (Loxoconchidae) and Xestoleberis Sars, 1866 (Xestoleberididae) along the coast of Vietam
Get PDFOne survey was done with SCUBA diving in Ha Long Bay and Cat Ba Island, Northern Vietnam (December 2013) and another one at Nha Trang Bay Marine Protected Area, Nha Trang city, Central Vietnam and Phu Quoc Marine Protected Area, Kien Giang Province, Southern Vietnam (November 2014). Sixteen species of the genus Loxoconcha and fourteen species of the genus Xestoleberis were found and identified. Eight species of the genus Loxoconcha were identified in group A, three species in group B, two in group C and three unidentified. Meanwhile, twelve species of the genus Xestoleberis were classified in group A and two in group B according to phylogenetic groups. From geographical distribution of the pore groups of the species in two genera Loxoconcha and Xestoleberis showed that the fauna of these genera in Vietnam is close to those of southern part of Japanese Island Arc, i.e., from Amami Island to the Philippines and Australia rather than Japanese Island Arc faunas.
Sampling the Folding Transition State Ensemble in a Tube-like Model of Protein
Get PDFWe used the tube model with Go-like potential for native contacts to study the folding transition of a designed three-helix bundle and a designed protein G-like structure. It is shown that both proteins in this model are two-state folders with a cooperative folding transition coincided with the collapse transition. We defined the transition states as protein conformations in a small region around the saddle point on a free energy surface with the energy and the conformationalroot mean square deviation (rmsd) from the native state as the coordinates. The transition state region on the free energy surface then was sampled by using umbrella sampling technique. We show that the transition state ensemble is broad consisting of different conformations that have different folded and unfolded elements
Effect of viscosity on slip boundary conditions in rarefied gas flows
No full textThe viscosity of gases plays an important role in the kinetic theory of gases and in the continuum-fluid modeling of the rarefied gas flows. In this paper we investigate the effect of the gas viscosity on the surface properties as surface gas temperature and slip velocity in rarefied gas simulations. Three various viscosity models in the literature such as the Maxwell, Power Law and Sutherland models are evaluated. They are implemented into OpenFOAM to work with the solver “rhoCentralFoam” that solves the Navier-Stokes-Fourier equations. Four test cases such as the pressure driven backward facing step nanochannel, lid-driven micro-cavity, hypersonic gas flows past the sharp 25-55-deg. biconic and the circular cylinder in cross-flow cases are considered for evaluating three viscosity models. The simulation results show that, whichever the first-order or second-order slip and jump conditions are adopted, the simulation results of the surface temperature and slip velocity using the Maxwell viscosity model give good agreement with DSMC data for all cases studied
Cladoceran diversity in Vinh Long province and redescription of the rare species Grimaldina brazzai richard, 1892 (Macrotricidae, Anomopoda, Branchiopoda) for zooplankton fauna Vietnam
No full textIn a total of four surveys at eight sites in some major rivers in Vinh Long province during 2013 to 2014, 18 species of cladoceran, belonging to 14 genera, 7 families and 2 orders, were recorded. The cladocerans fauna in Vinh Long province is recognized as moderate diverse, and the species recorded were mostly common species. Among 18 species, Grimaldina brazzai Richard, 1892 is a rare species. A total of four females specimens of species G. brazzai were collected at the Co Chien river, but male specimens were absent. The specimens were morphologically identified as G. brazzai described first by Richard (1892), followed by Brook (1959), Idris (1983), Smirnov (1992) and Hollwedel (2003). Grimaldina brazzai is currently the only one species in the genus Grimaldina and has been recorded in several tropical countries, such as Brazil, Thailand, Laos, Philippines, Indonesia, Malaysia, Cambodia and Singapore. They occur in lakes and rice fields, but population of this species is very limited in nature. In Vietnam, this species was first recorded in South Vietnam by Shirota (1966), but has not been described since then until recently Sinev Korovchinsky (2013) recorded this species in the Cat Tien National Park, Dong Nai province, South Vietnam.
ĐÁNH GIÁ HIỆU QUẢ TẠI CÁC MÔ HÌNH DOANH NGHIỆP THAM GIA QUẢN LÝ RẠN SAN HÔ VÌ MỤC ĐÍCH DU LỊCH SINH THÁI Ở VỊNH NHA TRANG
Get PDFThe models of coral reef management for the development of ecological tourism were conducted under the coordination among the 3 businesses (Khanh Hoa Salanganes Nest Company, Vinpearl Nha Trang and Tri Nguyen Tourism), Institute of Oceanography and Khanh Hoa Department of Natural Resources Environment. The analysis of trends of coral cover, density of reef fishes and big size invertebrates at 3 sites allowed assessing effectiveness of 3 years’ management. The stability of hard coral cover, except the decline at southern Hon Tam due to impacts of the typhoon in Nov., 2017 indicated no increased damage to corals from human activities. However, the dominance of small size fish ( 10 cm in length), the decline of density of larger size fish and the poorness of large size invertebrate showed continuous overexploitation at these managed areas.Mô hình quản lý rạn san hô vì mục đích du lịch sinh thái được thực hiện với sự tham gia của Viện Hải dương học, Sở Tài nguyên và Môi trường Khánh Hòa và 3 doanh nghiệp bao gồm Công ty TNHH Nhà nước MTV Yến Sào, Công ty TNHH Vinpearl Nha Trang và Công ty Du lịch Trí Nguyên. Hiệu quả sau 3 năm quản lý được đánh giá thông quan phân tích xu thế biến động về độ phủ san hô, mật độ cá rạn và sinh vật đáy kích thước lớn. Sự ổn định độ phủ san hô ở khu vực Sau Sao - Vinpearl và Bãi Sạn - Hòn Miếu chứng tỏ san hô không bị suy thoái. Trong khi đó, độ phủ san hô ở Nam Hòn Tằm tăng rõ rệt trong giai đoạn 2015–2017 nhưng giảm đột ngột vào năm 2018 do bão số 12 diễn ra vào tháng 11/2017. Tổng mật độ cá rạn biến động không rõ rệt với ưu thế là nhóm cá có kích thước nhỏ hơn 10 cm, trong khi nhóm cá có kích thước lớn suy giảm đáng kể về mật độ. Mật độ động vật đáy kích thước lớn rất thấp và chủ yếu thuộc về các nhóm không có giá trị kinh tế. Phân tích này chứng tỏ rằng hoạt động quản lý đã ngăn chặn được tác động của con người gây suy thoái san hô nhưng chưa có hiệu quả với hoạt động khai thác nguồn lợi quá mức
ENVIRONMENTAL IMPACTS ASSESSMENT OF BIODIESEL PRODUCTION FROM JATROPHA AND WASTE COOKING OIL (WCO)
No full textBiodiesel that is produced from renewable resources has been rising as a promising candidate to replace conventional energy. Vietnam, with a large amount of land used in agriculture or forestry, has advantaged conditions to produce and develop renewable energy from biomass resources. However, developing biodiesel from agricultural product may affect food security significantly. Therefore, Jatropha that is inedible and waste cooking oil (WCO) could be suitable to biodiesel production. One of the most important aims of using biodiesel to replace fossil diesel is to reduce environmental impacts, particularly impact on Climate Change. It is necessary to analyze the environmental performance of biodiesel through the entire life cycle. In this paper, life cycle assessment of biodiesel production and use was applied to measure the environmental performance of biodiesel produced from jatropha oil and WCO under Vietnam conditions. Some main emissions, such as CO2, NOx, PM, CH4, VOC and land use, were computed through a cradle-to-grave analysis. The result shows that when using Jatropha biodiesel to replace diesel, global warming potential (GWP) and photochemical oxidant formation potential (POFP) could be improved, but some other impacts, such as acidification potential (AP) and eutrophication potential (EP), could tend to increase. The environmental impacts of WCO biodiesel are all reduced in comparison with fossil diesel
Diversity of bats (Mammalia: Chiroptera) from the sop cop special use forest, son la province, Vietnam
Get PDFSop Cop is one of the largest remaining forest areas in the northwestern region of Vietnam. It contains high biodiversity values with previous records of many precious animal and plant species. However, biodiversity of Sop Cop is threatened by illegal activities of local people. In fact, bats and many other animal taxa in this area were poorly studied and rarely documented in previous publications. Between June 2014 and October 2016, the author conducted a variety of field surveys on bats in the Sop Cop Special Use Forest for understanding of their diversity and conservation status. The results indicated that the study area is a home to at least 36 bat species belonging to 20 genera, 6 families. Among them, 19 species are new to the area, 3 species are listed in the 2007 Red Data Book of Vietnam which must be considered for conservation priority in the future.