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

Structure elucidation off seven steroids from Sinularia conferta.

Seven steroids were isolated from the methanol extract of the soft corals Sinularia conferta. These steroids were elucidated as 7a-methoxyergosta-5,24(28)-diene-3b-ol (1), ergosta-5-ene-3β,7α-diol (2), 3β,7α-dihydroxyergosta-5,24(28)-diene (3), 3β-hydroxyergosta-5,24(28)-diene-7-one (4), ergosta-24(28)-ene-3β,5α,6β-triol-6-acetate (5), ergosta-24(28)-ene-3β,5α,6β-triol (6), and ergosta-3β,5α,6β-triol (7) by 1D and 2D-NMR experiments and comparison with reported data. Keywords. Sinularia conferta, Alcyoniidae, soft coral, steroid

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

All-dielectric Metamaterial for Electromagnetically-induced Transparency in Optical Region

Metamaterial (MM) is emerging as a promising approach to manipulate electromagnetic waves, spanning from radio frequency to the optical region. In this paper, we employ an effect called electromagnetically-induced transparency (EIT) in all-dielectric MM structures to create a narrow transparent window in opaque broadband of the optical region (580-670 nm). Using dielectric materials instead of metals can mitigate the large non-radiative ohmic loss on the metal surface. The unit-cell of MM consists of Silicon (Si) bars on Silicon dioxide (SiO$_{2}$) substrate, in which two bars are directed horizontally and one bar is directed vertically. By changing the relative position and dimension of the Si bars, the EIT effect could be achieved. The optical properties of the proposed MM are investigated numerically using the finite difference method with commercial software Computer Simulation Technology (CST). Then, characteristic parameters of MM exhibiting EIT effect (EIT-MM), including Q-factor, group delay, are calculated to evaluate the applicability of EIT-MM to sensing and light confinement

STRUCTURE ELUCIDATION OF FOUR STEROIDS FROM THE SOFT CORAL SINULARIA NANOLOBATA

Four steroids namely 3β-hydroxyergosta-5,24(28)-diene-7-one (1), dissesterol (2), 16α-hydroxysarcosterol (3), and sarcophytosterol (4) were isolated form the soft coral Sinularia nanolobata using various chromatographic methods. Their structures were elucidated by detailed analysis of the 1D and 2D NMR data and comparison with the reported values

The status of southern white-cheeked gibbon (Nomascus siki) in Truong Son key biodiversity area

The Southern white-cheeked crested gibbon, Nomascus siki, is an endemic primate to Vietnam and Laos, and has been identified as a nationally and globally endangered species (EN). However, little information is known on the status of the species in Vietnam generally and in the Truong Son key biodiversity area (Truong Son KBA) particularly. In order to explore the current status of the species in the Truong Son KBA, we conducted field surveys in 2018 and 2019. Analysis of the survey data shows 149 groups of gibbon in the 4 study areas. Combined with results of similar-techniqued survey in 2016 on the same species in Khe Nuoc Trong forest, we identified at least 252 gibbon groups and estimated 425 gibbon groups in the entire Truong Son KBA. These gibbon groups are mainly distributed in medium-rich evergreen closed forests in mountainous areas of the west Truong Son KBA, adjacent to the Vietnam-Laos border.