A conductive polypyrrole based ammonium ion selective electrode

In view of the development of miniaturized sensor arrays, a solid-contact ammonium ion selective electrode has been investigated. A conductive polypyrrole film was electrochemicallydeposited on a glassy carbon surface and used as an internal solid contact layer between the sensing membrane and solid electrode surface. A systematic evaluation of the importantparameters affecting the electromotive force (emf) response ispresented. The performances of this solid-contact sensor were verified using a batch-mode measurement setup and a wall-jet flow cell system. The designed sensor exhibited excellent selectivity for the primary ion and a linear response over the pNH₄ ⁺ range 1–5 with a slope of 56.3 mV decade^-1. The sensor has a fast response and is relativelyrobustness, and was also used to determine ammonium concentrations in natural waters, with promising results.     

Community concerns about landfills: A case study of Hanoi,Vietnam

This paper examines the nature of community concerns about a landfill in Hanoi, Vietnam and compares these concerns to those found in studies of North American landfills. Based on a survey of 174 households living near Hanoi's landfill, it was found that concerns were uniformly high within the study area. Although the community initially believed the proponent's claims that the landfill would not pollute the environment, their faith in those claims disappeared once the landfill opened and began to produce numerous negative impacts on the community. Residents called for a variety of technical, management and economic measures to mitigate these impacts.     

Different patterns of phytoplankton distribution,cell size,species' composition and abundance

A survey of the phytoplankton in the eastern Atlantic Ocean south of the Gulf of Guinea was undertaken, covering the local cyclonic gyre in the neutral col between the South Subtropical gyre, the Equatorial Countercurrent and the coast of Africa. Phytoplankton distribution, cell size, and abundance displayed distinct patterns which are presumed to be related to differential environmental dependence.     

Extraction,chemical compositions,and cytotoxic activities of essential oils of Thevetia peruviana

Abstract

In this study, The essential oil of flowers, fruits, and leaves of Thevetia peruviana, which were collected in Vietnam, were being reported for the first time. The essential oil of flowers was extracted by different methods: n-hexane extraction, distillation water, and supercritical CO₂ extraction. The compositions of essential oil of different parts of Thevetia peruviana were analyzed by GC-FID and GC/MS systems. Major chemical compositions of essential oil were identified as monoterpenes, sesquiterpenes, terpenoids, and sterol. The activities of total essential oil extracts of the Thevetia peruviana exhibit inhibitory activities against five cancer cell lines.     

一种紫外-可见光谱检测水质COD预测模型优化方法

针对紫外-可见光谱法检测水质COD预测模型的精度低和收敛速度慢等问题,研究了一种基于粒子群算法联合最小二乘支持向量机(PSO_LSSVM)的水质检测COD预测模型优化方法,并引入主元分析(PCA)算法对模型输入光谱数据进行降维预处理,借以提高模型的收敛速度.结果表明,利用粒子群(PSO)算法收敛速度快和全局优化能力,优化了最小二乘支持向量机(LSSVM)模型的惩罚因子和核函数参数,避免了人为选择参数的盲目性,克服了传统LSSVM预测模型的精度较低、稳健性较差等缺点.通过以收敛时间、预测平均相对误差(MRE)和均方根误差(RMSE)为评价标准进行评估,输入样本经过PCA降维预处理的PSO_LSSVM模型的预测能力和输入样本未经过降维预处理的LSSVM模型与PSO_LSSVM模型进行了比较分析,输入样本经过PCA降维预处理的PSO_LSSVM模型预测效果最优,且此算法使用C语言实现,易于移植,这为紫外-可见光谱水质COD在线、实时性检测奠定了基础.     

Developments in forward osmosis and membrane distillation for desalination of waters

Membrane technology has become a common separation technology over the past decennia. Membranes are used more and more for the production of drinkable water from groundwater, surface water and wastewater. Membranes are now competitive versus conventional techniques. Desalination is predominantly used to eradicate the problem of water scarcity. The sustainability of all desalination processes depends mainly on the reduction of energy costs (production cost) and the increase in water recovery. Forward osmosis and membrane distillation are emerging technologies for sustainable desalination. Here we review membrane processes of forward osmosis and membrane distillation and the advancements in membrane material and modules. We also discuss the capability of membrane distillation in treating highly concentrated aqueous solutions derived from other desalination processes. Furthermore, the advancements in fabrication of high-performance membrane is reviewed and the performance of different membranes and optimization of membrane distillation process are summarized.     

Spatial Variations in Fish Abundance in the Mekong Delta

Russian Journal of Ecology - For the first time, the density of fish population has been quantitatively assessed in the Mekong River delta in the territory of the Socialist Republic of Vietnam. The...     

In vivo assessment of plant extracts for control of plant diseases: A sesquiterpene ketolactone isolated from Curcuma zedoaria suppresses wheat leaf rust

As an alternative to synthetic pesticides, natural materials such as plant extracts and microbes have been considered to control plant diseases. In this study, methanol extracts of 120 plants were explored for in vivo antifungal activity against Rhizoctonia solani, Botrytis cinerea, Phytophthora infestans, Puccinia triticina, and Blumeria graminis f. sp. hordei. Of the 120 plant extracts, eight plant extracts exhibited a disease control efficacy of more than 90% against at least one of five plant diseases. In particular, a methanol extract of Curcuma zedoaria rhizomes exhibited strong activity against wheat leaf rust caused by P. triticina. When the C. zedoaria methanol extracts were partitioned with various solvents, the layers of n-hexane, methylene chloride, and ethyl acetate showed disease control values of 100, 80, and 43%, respectively, against wheat leaf rust. From the C. zedoaria rhizome extracts, an antifungal substance was isolated and identified as a sesquiterpene ketolactone based on the mass and nuclear magnetic resonance spectral data. The active compound controlled the development of rice sheath blight, wheat leaf rust, and tomato late blight. Considering the in vivo antifungal activities of the sesquiterpene ketolactone and the C. zedoaria extracts, these results suggest that C. zedoaria can be used as a potent fungicide in organic agriculture.     

Persistence of white spot syndrome virus in shrimp ponds and surrounding areas after an outbreak

White Spot Syndrome Virus (WSSV) is the major and most serious pathogen in shrimp aquaculture industries. By using a sensitive PCR-based detection technique followed by sequencing multiple PCR products for confirmation, we address to the question of whether WSSV can persist in shrimp ponds and surrounding areas after an outbreak. The seawater samples were taken from two shrimp ponds and surrounding canals in a coastal area in northern Vietnam, Quang Ninh Province where the shrimps cultured in the two ponds had been killed due to a WSSV outbreak in April 2001 and the ponds were thereafter abandoned. A total of 480 seawater samples (30 samples each for July and December of 2001 and 2002) were subjected to WSSV genome detection. Although the detection rates of WSSV genome were generally gradually declined in seawater environments of both diseased shrimp ponds and surrounding canals, WSSV was still detected with rates of more than 10% in the diseased ponds and lower in surrounding canals in December 2002, 20 months after the WSSV outbreak.