Surface Potential of MIBC at Air/Water Interface: a Molecular Dynamics Study

The interfacial behavior of alcohols is significantly different from bulk due to amphiphilic structures. Such behavior can dramatically change the interfacial properties within the nano-scale of interfacial layer and have significant applications in industrial processes such as mineral flotation. In this study, the adsorption of MIBC (methyl isobutyl carbinol), a popular frother, was investigated by molecular dynamics. Surface potential was obtained at different surface concentration and compared to experimental data. The simulations results compared well with theoretical data using a single adjustable parameter. It has been found that the disordered water molecules contribute to surface potential more than MIBC molecules. The study demonstrates the application of MD in investigating the efficiency of frother systems

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

Triterpenes and triterpene-glycoside from the leaves of Lawsonia inermis.

From the leaves of  Lawsonia inermis (syn. L. alba), two triterpenes augustic acid (1) and 1b,2a,3a,19a-tetrahydroxy-12-ursen-28-oic acid (2), and a triterpene-glycoside suavissimoside R1 (3) were isolated by using various chromatoghraphies. Their structures were characterized on the basis of the spectroscopic data (1D-NMR, HSQC, HMBC, ESI-MS) in comparison with the literature. This is the first report of 1 - 3 from Lawsonia species. Keywords: Lawsonia inermis, Lythraceae, Triterpene

Five lignans from the mangrove Rhizophora stylosa Griff.

Five lignans (-)-(7R,8S)-dihydrodehydrodiconiferyl alcohol (1), (7S,8R)-3,3¢,5-trimethoxy-4¢,7-epoxy-8,5¢-neolignan-4,9,9¢-triol (2), (+)-isolariciresinol (3), polystachyol (4), (+)-pinoresinol (5) were isolated from the mangrove plant Rhizophora stylosa Griff.. The chemical structures of these compounds were elucidated by analysis of their NMR spectra and compared with those reported references. All these compounds were isolated from this plant for the first time

Highly oxygenated sterols from the starfish Archaster typicus

Three highly oxygenated sterols named ergost-22-ene-3β,4β,5α,6α,8β,14α,15α,25R,26-nonol, 27-norcholestane-3β,4β,5α,6α,7β,8β,14α,15α,24R-nonol, 27-norcholestane-3β,4β,5α,6α,8β,14α, 15α,24R-octol were isolated from the methanolic extract of the starfish Archaster typicus. Their structures were determined by the physicochemical and spectral data in comparison with the reported literature. This is the first report of these compounds from the Vietnamese starfish Archaster typicus

A SOCIAL SURVEY ON COMMUNITY RESPONSE TO ROAD TRAFFIC NOISE IN HANOI

Joint Research on Environmental Science and Technology for the Eart

Saponins isolated from the Vietnamese sea cucumber Stichopus chloronotus.

Using various chromatographic methods, three triterpene saponins neothyonidioside (1), stichoposide D (2), and holothurin B (3), were isolated from the methanol extract of the sea cucumber Stichopus chloronotus. Their structures were elucidated by 1D and 2D-NMR experiments and comparison of their NMR data with reported values. Compound 1 was isolated from S. chloronotus for the first time

Sedimentary petrology characteristics and their implications for provenance of Hoanh Bo Basin Neogene system in Quang Ninh province, north-eastern Vietnam

The Hoanh Bo Basin has developed over multiple periods since the Miocene period in association with the tectonic activity of the Chi Linh-Hon Gai and Trung Luong Faults. The basin is filled with Neogene continental sediments, comprising mainly polymictic conglomerates, sandstones, siltstones, claystones, and shales. Coarser-grained polymictic deposits predominate along the northern and western margins of the basin, whereas different types of siltstones, claystones, and sandstones occur in its centre, as well as along its southern and eastern parts, toward the Ha Long Bay. The conglomerates and sandstones are composed mainly of quartz and sedimentary rock fragments, and a small amount of mica. Cement is mainly built of iron-oxide, clay or carbonate mud. The source area for the Hoanh Bo Basin sediments was located in the close vicinity of the basin. It was built of strongly weathered rocks of the Hon Gai, Ha Coi, Cat Ba Formations

Lithofacies and depositional environments of the Paleogene/Neogene sediments in the Hoanh Bo Basin (Quang Ninh province - NE Vietnam)

The Hoanh Bo Basin is a multiple period formed basin which is associated with the tectonic mechanism due to the activities of the Chi Linh - Dong Trieu and Trung Luong faults. The basin is filled with continental sediments, comprising mainly polymictic conglomerates, sandstones, siltstones, claystones and shales. Coarser-grained polymictic deposits predominate along the northern and western margins of the basin, while different types of siltstones, claystones, even sandstones occur in its center, as well as along its southern and eastern parts toward the Ha Long Bay.            Based on the dominant grain-size class, texture, stratification, degree of clast rounding and sorting, 17 lithofacies were determined in the Hoanh Bo Basin infill, accumulating in alluvial fan, fluvial, deltaic and lacustrine environments.Alluvial fan and fluvial environments are characterized by an assemblage of lithofacies such as sand- and mud-supported disorganized breccias (Gb), clast- to sand-supported conglomerates (Gmm), clast-supported inverse-graded conglomerates (Gig), planar-cross-bedded conglomerates (Gp), trough cross-bedded conglomerates (Gt), horizontally stratified conglomerates (Gh), planar cross-bedded sandstones (Sp), trough cross-bedded sandstones (St), ripple cross-laminated sandstones (Sr), horizontally bedded sandstones (Sh), massive sandstones (Sm), massive mudstones, siltstones (Fm), laminated siltstones and mudstones (Fl), massive claystones (Fsm) and coaly lithofacies (C);  the deltaic assemblage is dominated by planar-cross-bedded conglomerates (Gp), horizontally stratified conglomerates (Gh), planar cross-bedded sandstones (Sp), horizontally bedded sandstones (Sh), low-angle cross-bedded sandstones (Sl); while the lacustrine assemblage consists of ripple cross-laminated sandstones (Sr), horizontally bedded sandstones (Sh), normally graded sandstones (Sng), massive mudstones, siltstones (Fm), laminated siltstones and mudstones (Fl), massive claystones (Fsm) and coaly lithofacies (C)

Hidden in the jungle of Vietnam: a new species of Quasipaa (Amphibia, Anura, Dicroglossidae) from Ngoc Linh Mountain

A new species of Quasipaa is described from Ngoc Linh Mountain of the Kon Tum Massif in central Vietnam. The new species is morphologically distinguishable from its congeners on the basis of a combination of the following diagnostic characters: SVL 79.6–84.3 mm in males and 64.6–69.9 mm in females; head broader than long; vomerine teeth present; external vocal sacs absent; tympanum slightly visible; dorsum with lines of thick ridges and small round tubercles; flanks covered by oval and round tubercles; supratympanic fold present; dorsolateral fold absent; ventrolateral sides, ventral surface of arms, and all fingers with spines in males; the absence of spines on chest and belly in males; toes fully webbed to distal portion of terminal phalanx; in life, dorsum dark brown, chest and belly immaculate white. Phylogenetic analyses found that the genetic divergence of the new species and its congeners ranged from 4.2–5.1% (compared with Quasipaa boulengeri) to 7.6–8.1% (compared with Q. shini) in the 16S gene