Effects of Osmotic Pressure on Water Transport in W(1)/O/W(2) Emulsions

In a W(1)/O/W(2) double-emulsion globule, when the W(1) phase was made of pure water while salt (NaCl) was present only in the W(2) phase, water was transported from W(1) to W(2) at a constant transport rate, -dR/dt. In the case of hydrated-surfactant transport, rates rose linearly with increasing salt concentration in W(2) through acceleration of the dehydration process of the hydrated surfactants at the O/W(2) interface. When the water was transported through spontaneous emulsification and reverse micellization, the water transport rates were independent of the osmotic pressure over a significant range of salt concentration in W(2). When salt was present in both the W(1) and W(2) phases-though at a higher concentration in W(2)-water transport stopped when the salt concentrations in W(1) and W(2) equalized, indicating that only water may transport through the oil phase while salt stays trapped in the W compartments. In visual-contact experiments, where transport was controlled by the hydrated-surfactant mechanism, the water transport rates were initially constant to then decreased asymptotically to zero. This showed that, as salt concentration in W(1) increased with time, the controlling process shifted from surfactant dehydration at the O/W(2) interface to hydration at the W(1)/O interface. For the spontaneous emulsification and reverse-micellar mechanisms at visual noncontact, water transport rates remained constant during a given experiment and decreased with increasing initial salt concentration in W(1), indicating that the formation process of emulsified water droplets and reverse micelles at the W(1)/O interface was the rate-controlling step. Copyright 2001 Academic Press.     

GLR(K)文法及其分析算法

本文给出了一个分析算法,能分析正规的LR(K)文法,但所用的状态数目与LALR(K)相同。     

Steric repulsion between internal aqueous droplets and the external aqueous phase in double emulsions

A theoretical model for analyzing the steric repulsion energy between internal aqueous droplets and the external aqueous phase in double emulsions, which results from the steric interaction between the surfactant molecules adsorbed at the two interfaces, has been established. The steric interaction is dependent on the separation distance between the internal aqueous droplets and the external aqueous phase, the thicknesses of the two adsorbed surfactant layers, and the size of the internal aqueous droplets and the oil globules, all of which determine the extent of the compression of the adsorbed surfactant molecules. The thickness of each of the two surfactant layers have the same effect on the steric repulsion, and stronger steric interaction can be achieved with thicker adsorbed layers, which can effectively prevent coalescence between the internal aqueous droplets and the external aqueous phase. Increasing the internal aqueous droplet size can produce stronger steric repulsion; however, larger oil globules will weaken the steric repulsion, indicating that a more stable double-emulsion system can be achieved by preparing the system with smaller oil globules and larger internal aqueous droplets.     

Review on Layered Manganese-Based Metal Oxides Cathode Materials for Potassium-Ion Batteries: From Preparation to Modification

Potassium-ion battery is rich in resources and cheap in price, in the era of lithium-ion battery commercialization, potassium-ion battery is the most likely to replace it. Based on the classification and summary of electrode materials for potassium-ion batteries, this paper focuses on the introduction of manganese-based oxide K_xMnO₂. The layered K_xMnO₂ has a large layer spacing and can be embedded with large size potassium-ions. This paper focuses on the preparation and doping of manganese-based cathode materials for potassium-ion batteries, summarizes the main challenges of K_xMnO₂-based cathode materials in the current stage of research and further looks into its future development direction.     

大气气溶胶中锂的化学分离与同位素比的质谱检测

通过大量条件实验,确定离子交换法分离Li+、Na+的最佳淋洗条件柱填料为Dowex-50w×8阳离子树脂,柱高为12 cm,淋洗液为0.8 mol/mL HCl-50%CH3OH,淋洗速度约为0.48 mL/min.采用离子交换法分离大气气溶胶中Li与其它元素,采用Li3PO3为样品涂样形式的热电离质谱法测量了大气气溶胶中Li的同位素比值.化学分离过程中Li的回收率大于95%,大气气溶胶中稳定Li同位素6Li/7Li比值为0.08206.     

van der Waals interaction between internal aqueous droplets and the external aqueous phase in double emulsions

A mathematical model for analyzing the van der Waals interaction between the internal aqueous droplets (W(1)) and the external aqueous phase (W(2)) of double emulsions has been established. The effects of Hamaker constants of the materials forming the system, especially those of the two different adsorbed surfactant layers with uniform density (A(1) and A(2)), on the van der Waals interaction were investigated. The overall van der Waals interaction across the oil film is a combined result of four individual parts, that is, W(1)-W(2), A(1)-A(2), W(1)-A(1), and A(2)-W(2) van der Waals interaction, and it may be either attractive or repulsive depending on many factors. It was found that the overall van der Waals interaction is dominated by the W(1)-W(2) interaction at large separation distances between the W(1)/O and O/W(2) interfaces, while it is mostly determined by the A(1)-A(2) interaction when the two interfaces are extremely close. Specifically, in the cases when the value of the Hamaker constant of the oil phase is intermediate between those of W(1) and W(2) and there is a thick oil film separating the two interfaces, a weak repulsive overall van der Waals interaction will prevail. If the Hamaker constant of the oil phase is intermediate between those of A(1) and A(2) and the two interfaces are very close, the overall van der Waals interaction will be dominated by the strong repulsive A(1)-A(2) interaction. The repulsive van der Waals interaction at such cases helps stabilize the double emulsions.     

POROUS SILICA NANO-TUBE AS HOST FOR ENZYME IMMOBILIZATION

With their hollow morphology and large openings, the as-synthesized porous silica nano-tubes (NTPS), prepared through a sol-gel routine by using nano-sized needle-shaped CaCO3 particles as templates, were used as host for enzyme immobilization. Bioimmobilization study showed that enzyme molecules could not only be adsorbed on the external surface of NTPS but also entrapped in their inner hollow cores, leading to higher enzyme loading capacities of NTPS (more than 350 mg/g silica) in a shorter time, as compared to common porous silica (less than 50 mg/g) and most conventional mesoporous silica materials (less than 100 mg/g).     

用力学分析一起特大交通事故

交通事故中某些条件作合理设定，应用牛顿力学，推算肇事车辆的速度．