CAMELLIA HOABINHENSIS (THEACEAE: SECT. CHRYSANTHA), A NEW YELLOW-FLOWERED SPECIES FROM NORTHERN VIETNAM

A new species, Camellia hoabinhensis (section Chrysantha, Theaceae), is described and illustrated based on specimens collected from a lowland forest on limestone hills in Hoa Binh Province, northern Vietnam. The species is characterized by its small habit to 4.5 m tall, large flowers 9.0–9.5 cm in diameter with 18–19 light yellow petals, and hairy filaments, ovaries, and styles. A comparison of the new species with similar species, C. euphlebia, C. impressinervis, C. phanii, and C. velutina, is provided. The IUCN conservation status of the proposed species is Data Deficient (DD)

A numerical model for the tidal oscillation and current in the Gulf of Tonkin

in this paper results of a numerical model, based on the TIDEFLOW-2DSoftware, for the tidal oscillation and current in the Gulf of Tonkin (GT) are presented. The model was tested as follows: i) the observed values of the four main tidal constituents M2, S2, K1, 01 at the 44 coastal stations and islands were compared with computed ones; ii). the computed tidal levels were compared with the correlative ones in the Tide Tables at the six stations: Hon Gai, Cua Ong, Hon Dau, Cua Hoi, Cua Gianh and Cua Tung in many monthly periods; iii) the results of computed tidal levels and currents were compared with the observed data. The results of testing show a good agreement between the available data and computed values, therefore we can use this model for simulation t ide level and current of GT. The results of using this model in GT: distribution of the major harmonic constituents; the tidal elevation and current patterns; the extremal values of the tidal level and current,... will be published later

Calculation of the turbidity transport in Dinh An coastal zone

In the paper, the results of the calculation of turbidity transport in Dinh An coastal area by using the software named RDPOL based on random walk techniques developed by CMERCS are presented. In previous study, the carried out numerical model has been verified well by remote sensing images for classification of the turbidity distribution of Red, Thai Binh, Han, Thu Bon, Sai Gon - Dong Nai and Mekong estuaries. In this study, computed results, that the complexity of the bathymetry, the river flow of the Mekong River system and seasonal monsoon winds are taken into account, are compared with the observed data at 19 stations including 10 stations in March and 9 stations in October, 1997 in Dinh An coastal zone and show its reasonable agreement. Some maps of turbidity distribution in the area have been carried out and several remarks have been made

Chemical constituents from the leaves of Styrax argentifolius H.L. Li and their antioxidative activity

Searching for bioactive agents from medicinal plants, the phytochemical investigation on the EtOAc extract of the Vietnamese Styrax argentifolius leaves has resulted in the isolation and structural determination of five compounds, including one nor-neolignan egonoic acid (1), one lignan (+)-pinoresinol (2), one sterol (20R)-3β-hydroxysitgmasta-5,22-dien-7-one (3), and two triterpenoids lupeol (4), and 2α,3α,24-trihydroxy-urs-12-en-28-oic acid (5). The chemical structures of these secondary metabolites were elucidated by NMR and MS spectral data. All isolated compounds were first observed in S. argentifolius species. Sterol 3 and triterpenoid 5 were detected in genus Styrax for the first time. With the IC50 value of 19.10 µg/mL, compound 2 possessed the strong activity in DPPH radical scavenging assay

Preliminary results of the study on the reasons of the Hai Hau erosion phenomenon

Overall the evolution process of the Red River Delta based on the maps and historical data resulted in a fact that before the 20th century all the Nam Dinh coastline was attributed to accumulation. Then started the erosion process at Xuan Thuydistrict and from the period of 1935 - 1965 the most severe erosion was contributed in the stretch from Ha Lan to Hai Trieu, 1965 - 1990 in Hai Chinh - Hai Hoa, 1990 - 2005 in the middle part of Hai Chinh - Hai Thinh (Hai Hau district). The adjoining stretches were suffered from not severe erosion. At the same time, the Ba Lat mouth is advanced to the sea and to the North and South direction by the time with a very high rate.The first task of the mathematical modeling of coastal line evolution of Hai Hau is to evaluate this important historical marked periods e. g. to model the coastal line at the periods before 1900, 1935 - 1965; 1965 - 1990; 1990 - 2005. The tasks is very complicated and time and working labors consuming.In the paper, the primarily results of the above mentioned simulations (as waves, currents, sediments transports and bottom - coastal lines evolution) has been shown. Based on the obtained results, there is a strong correlation between the protrusion magnitude and the southward moving of the erosion areas

Geotrophic and drift current in the South China Sea, Area IV: Vietnamese waters

The water circulation in area IV was calculated by 2 methods. The circulation for the area where water depth exceeded 600m was calculated by the geostrophic balance method. In shallow water area effect of wind absolutely surpasses geostrophic balance, so wind induced drift current is greater than geostrophic current many times. So, for the whole area (shallow deep) the drift current was calculated by two-dimensional nonlinear shallow water equation based on typical monsoon fields. The results of 2 methods showed common picture of the circulation with divergence and convergence changing by season

Cytotoxic naphthoquinones from Diospyros fleuryana leaves

In the search for anti-cancer plants in Vietnam, the leaves of Diospyros fleuryana were selected for chemical investigation. Phytochemical analysis of the ethyl acetate (EtOAc) extract led to the isolation of two naphthoquinones isodiospyrin (1), and 8'-hydroxyisodiospyrin (2), and one isoflavone 7-O-methylbiochanin A (3). The chemical structures of isolated compounds were determined by 1D-NMR (1H, and 13C-NMR), 2D-NMR spectra (HSQC, and HMBC), and MS spectroscopy. Compound 3 was isolated from genus Diospyros for the first time. Regarding the strong IC50 values of 2.27, and 8.0 µM against KB, and Hep cell lines respectively, cytotoxic examination suggested that compound 2 is a promising agent in anti-cancer treatment.Â

MACRO-ZOOPLANKTON ABUNDANCE IN RELATION TO METAL ACCUMULATION AND WATER QUALITY IN TRUC BACH LAKE

Urban lake pollution is one of the serious issues due to suffering of waste discharged from householders. However, there is a gap of knowledge about the diversity of zooplankton species and how metals accumulate in zooplankton in urban ecosystems. We addressed this by determining the rule of blooming macro-zooplankton in Truc Bach lake and levels of two essential metals: copper (Cu), and zinc (Zn) and of three non-essential metals: arsenic (As), and lead (Pb) in water samples were determined. The results showed that Cladocerans and copepods are macro-zooplankton dominant species in Truc Bach Lake. Water temperature significantly affects the variety of copepod blooming. Arsenic concentration in water collected from the lake exceeded the safety level of current Vietnamese regulation. As concentration in macro-zooplankton positively correlated with metal concentrations in the water (p 0.05) while the concentration of Cu, Zn, and Pb in water has no significant correlation with the metal in zooplankton’s body. The relative abundance of adult copepods in Truc Bach lake had a negative correlation with As concentration in water (p = 0.01). The higher As concentration in water, the lower relative abundance of copepods was found in the sample