银镀层中银离子的迁移现象(二)

文章的第2部分论述了银镀层发生离子迁移的实验方法和检测方法.实验方法有环境实验法和溶液实验法;检测方法包括光学观察,绝缘电阻值测量,感应电特性,SEM观察,组成分析,放射化分析,软X射线观察,AFM观察和激光显微镜观察等.     

Transition phenomena in an oscillating manometer

The decay of oscillation of a liquid column in a manometer has been studied. Measured values of the damping coefficients in laminar conditions agree well with previous data. The transition between turbulent and laminar damping has also been measured. For transition to fully developed turbulent flow, the critical Reynolds number is a function only of the Valensi number. In situations where turbulence exists at the ends of the liquid column but laminar conditions persist in the main section, the transition Reynolds number and damping exponent are functions of frequency and kinematic viscosity as well as Valensi number.     

Ferroelectric liquid crystal models of ion channels and gating phenomena in biological membranes

Ferroelectric liquid crystal models of voltage-dependent ion channels are discussed quantitatively. The consequences of the hypothesis that the gating mechanism of ion channels is a transition of a ferroelectric liquid crystal component of a biomembrane, in which the tilt angle of the S4 segments decreases to zero, are analyzed.     

Transport phenomena under unsteady conditions in an agitated vessel

An experimental study of transport phenomena at the wall of an agitated vessel with a propeller impeller under unsteady conditions is reported. The transient in heat transfer at the wall is caused by a step change in the speed of agitation from an initial static condition. The results are expressed in terms of a rise in modified “j-factor” above the initial free convection value and the number of revolutions taken by the impeller from the start of agitation. Also, an attempt has been made to find an analogy beween heat and momentum transfer. Results are given for the power in terms of Euler number plotted against the impeller Reynolds number. An empirical expression is also given for the transient heat transfer considering the system as a pure first order one with time delay. A “time-factor” constant which gives the number of impeller revolutions for 63.2% of the change from the initial to a final steady state is expressed as a function of impeller Reynolds number (10² to 10⁶) and fluid Prandtl number (6 to 10⁶).     

Investigation of transport phenomena in a hybrid ion exchange-electrodialysis system for the removal of copper ions

Hybrid ion exchange electrodialysis processes allow the removal of metal ions from dilute waste liquids and the recovery of more concentrated solutions. The work reported here was aimed at investigating the two steps in the treatment process, namely, adsorption of metal ions onto the packed bed of resin and electromigration (i.e., the transport of these ions in the complex system under the applied electrical field). The case of copper sulfate was investigated. Dowex resins with a cross-linking degree of 2 and 8% were used. The flux of copper through the resin bed and the current efficiency for ion transfer to the cathode compartment were determined as a function of potential gradient and copper ionic fraction in the bed. Apparent diffusion coefficients of Cu²⁺ in the overall system were deduced from the experimental data.     

Effects of adsorption on detergency phenomena: II

Knowledge of adsorption of active agents onto different interfaces is fundamental to their technical application in the washing and cleaning process. Particularly important is their influence on interactions in multicomponent systems. By the formation of mixed adsorption layers consisting of at least 2 surfactants, an enhancement of adsorption is attained as compared with the adsorption isotherms of individual components. Parallel to this, the washing effect also increases. Water-soluble complexing agents are adsorbed specifically onto polar surfaces, particularly onto such surfaces that contain calcium ions. Their affinity to such surfaces is significantly greater than those of surfactants which are mainly adsorbed onto hydrophobic interfaces. Due to the complex composition of soil, both components complement each other. In addition to their ion exchange capacity for bivalent ions, zeolites have a certain ability to adsorb molecularly dispersed soil components as well as colloidal particles. Hence, they have a special effect as antiredeposition agents. Polymeric antiredeposition agents act by formation of adsorption layers on pigments and fibers. Only such compounds that cannot be displaced completely from interfaces by competing adsorption with surfactants show positive antiredeposition effects.     

Effects of adsorption on detergency phenomena: I

Knowledge of the adsorption of surface-active substances onto different interfaces is of basic importance for its technical application in washing and cleaning processes. Important parameters are adsorption kinetics and adsorption equilibria. The criteria of adsorption kinetics and adsorption equilibrium change in opposite directions with increasing length of the hydrophobic group. Equilibrium adsorption increases exponentially, whereas the diffusion coefficient decreases linearly with increasing number of CH₂ groups in then-alkyl part of nonbranched surfactants. Branching of the hydrophobic group has the same effect as shortening the chain length. The wetting effect changes in the same direction as the diffusion coefficient, whereas the washing effect changes similarly to equilibrium adsorption. The generally positive temperature effect on soil removal may be reversed in the opposite direction for nonionic surfactants at temperatures above the cloud point. Separation of phases brings about a decrease of adsorption and washing performance. Presented at the AOCS meeting, May 1981, New Orleans.     

Supramolecular Assembly and Binding in Aqueous Solution: Useful Tips Regarding the Hofmeister and Hydrophobic Effects

The self-assembly of structurally discrete entities, and supramolecular chemistry in general, continues to expand into the aqueous realm. To do so, however, requires a firm understanding of the properties of aqueous solution, and how these “change the rules” for binding and assembly relative to organic solvents. In this mini-review we highlight the state-of-the-art understanding of the supramolecular properties of water, and how these influence the design of hosts and self-assembling systems.     

Partition Coefficients of Alkaloids in Biphasic Ionic-Liquid-Aqueous Systems and their Dependence on the Hofmeister Series

The aim of this work is to test the potential of hydrophobic phosphonium-based ionic liquids for the extraction of caffeine and nicotine from aqueous phases through the determination of the alkaloids' partition coefficients. It was found that the caffeine partitioning for the ionic-liquid-rich phase increases with the ionic liquid hydrogen-bonding accepting capability (or water content), while for nicotine a nearly opposite behavior was observed. In addition, both the influence of the ionic concentration of the aqueous solution (ranging from 0.0 mol · kg^?1 to 3.0 mol · kg^?1), and the salt nature (with K- and Na-based salts), in the partitioning of caffeine for the ionic-liquid-rich phase were investigated. The influence of the inorganic salt nature in the alkaloid partitioning for the ionic-liquid-rich phase closely follows the Hofmeister series.     

Non-isothermal phenomena in polymer engineering and science: A review. Part II: Non-isothermal phenomena in polymer deformation

Thermal phenomena in deformation of solids and flows are reviewed. Regularities common to all these phenomena as well as their characteristic features and consequences important for science and engineering are reported. The analogy between thermal phenomena in polymer mechanics and in chemical reaction is noted.     

Creatine supplementation with specific view to exercise/sports performance: an update

ABSTRACT: Creatine is one of the most popular and widely researched natural supplements. The majority of studies have focused on the effects of creatine monohydrate on performance and health; however, many other forms of creatine exist and are commercially available in the sports nutrition/supplement market. Regardless of the form, supplementation with creatine has regularly shown to increase strength, fat free mass, and muscle morphology with concurrent heavy resistance training more than resistance training alone. Creatine may be of benefit in other modes of exercise such as high-intensity sprints or endurance training. However, it appears that the effects of creatine diminish as the length of time spent exercising increases. Even though not all individuals respond similarly to creatine supplementation, it is generally accepted that its supplementation increases creatine storage and promotes a faster regeneration of adenosine triphosphate between high intensity exercises. These improved outcomes will increase performance and promote greater training adaptations. More recent research suggests that creatine supplementation in amounts of 0.1 g/kg of body weight combined with resistance training improves training adaptations at a cellular and sub-cellular level. Finally, although presently ingesting creatine as an oral supplement is considered safe and ethical, the perception of safety cannot be guaranteed, especially when administered for long period of time to different populations (athletes, sedentary, patient, active, young or elderly).     

Transport phenomena in porous media: A review

This paper, a review of the state of the art of the drying process in wet porous media, presents an overview of thermodynamic relations in heat treatment of synthetic fiber fabrics. Heat and mass transfer in wet porous media are coupled in a very complicated way. The structure of the solid matrix varies widely in shape. There is, in general, a distribution of void sizes, and the structures may be locally irregular. Energy transport in such a medium occurs by conduction in all of the phases. Mass transport occurs within voids of the medium. In an unsaturated state, these voids are partially filled with a liquid, whereas the rest of the voids contain some gas. It is a common misapprehension that nonhygroscopic fibers (i.e., those with intrinsically low moisture content) will automatically produce a hydrophobic fabric. The main significance of the fine geometry of a textile structure in contributing to resistance to water penetration can be stated in a different manner. Published in Russian in Teoreticheskie Osnovy Khimicheskoi Tekhnologii, 2006, Vol. 40, No. 1, pp. 17–30. This article was submitted by the author in English.     

Modeling of transfer phenomena on heterogeneous Ziegler catalysts: Differences between theory and experiment in olefin polymerization (an introduction)

This article begins by briefly reviewing the more important contributions to the area of modeling heat and mass transfer, and particle growth during the polymerization of olefins on Ziegler–Natta catalysts. It is shown that these models are capable of identifying the critical areas involved in heat and mass transfer, and of modeling polymerizations where the observed activity is less than approximately 5,000 g of polymer per gram of catalyst per hour (g/g/h). However, it is not possible to use these models “as-is” to model more modern catalysts whose activity levels can surpass the 50,000 g/g/h mark because they predict prohibitively large concentration gradients inside the growing particles during slurry polymerizations, and temperature gradients outside the particles during polymerization in the gas phase. An analysis of the mass and heat transfer Peclet numbers (Pe) reveals that certain simplifying assumptions may not always be valid. Pe values in the transition range suggest that convection inside the particles during polymerization in the liquid phase may help to explain why observed mass transfer rates are higher than the predicted rates. In an opposite vein, a Pe analysis shows that conductive heat transfer may play an important role at length scales characteristic of those in the early stages of polymerization. A new mechanism for heat transfer at reduced length scales is proposed. © 1995 John Wiley & Sons, Inc.     

Agronomic and environmental aspects of phosphate fertilizers varying in source and solubility: an update review

This review discusses and summarizes the latest reports regarding the agronomic utilization and potential environmental effects of different types of phosphate (P) fertilizers that vary in solubility. The agronomic effectiveness of P fertilizer can be influenced by the following factors: (1) water and citrate solubility; (2) chemical composition of solid water-soluble P (WSP) fertilizers; (3) fluid and solid forms of WSP fertilizers; and (4) chemical reactions of P fertilizers in soils. Non-conventional P fertilizers are compared with WSP fertilizers in terms of P use efficiency in crop production. Non-conventional P fertilizers include directly applied phosphate rock (PR), partially acidulated PR (PAPR), and compacted mixtures of PR and WSP. The potential impacts of the use of P fertilizers from both conventional (fully acidulated) and non-conventional sources are discussed in terms of (1) contamination of soils and plants with toxic heavy metals, such as cadmium (Cd), and (2) the contribution of P runoff to eutrophication. Best practices of integrated nutrient management should be implemented when applying P fertilizers to different cropping systems. The ideal management system will use appropriate sources, application rates, timing, and placement in consideration of soil properties. The goal of P fertilizer use should be to optimize crop production without causing environmental problems.     

A review: applications of ion transport in micro-nanofluidic systems based on ion concentration polarization

Lab-on-a-chip has been used widely in rapid, high-throughput and low-consumption analysis of samples in biochemistry. The ion concentration polarization (ICP) produced by ion-selective transport of nanochannels provides a novel solution for problems in ultra-low concentration sample detection, systems biology and desalination. This paper reviews the applications of ion transport based on the principle of ICP in micro-nanofluidic systems. First, the fundamental governing equations of ICP are described. Then, the applications of nano-electrokinetic ion enrichment and ion current rectification (ICR) are introduced. Nano-electrokinetic ion enrichment is used mainly in the fields of molecular enrichment, ultra-low concentration sample detection and seawater desalination. ICR is applied mainly to the sensitive detection of analytical substances such as proteins, nucleic acids and small molecules. The application of ion transport based on ICP principle is summarized and the possible directions worthy of further research are proposed. © 2019 Society of Chemical Industry