Space-time self-organization phenomena in oxidation of various substrates by atmospheric oxygen in aqueous solutions

In the oxidation of a number of organic and inorganic substrates by atmospheric oxygen in solutions under various conditions, oscillations of potential and the formation of spatial structures have been observed. Chaotic oscillations of the potential of a point platinum electrode have been observed in a system in which the reaction mixture is stirred, in contrast to the situation without stirring, in which spatial structures are formed, almost always visually evident when a redox indicator is introduced into the system.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2474–2482, November, 1991.The author wishes to thank Academician K. B. Yatsimirskii (Academy of Sciences of the Ukrainian SSR) for fruitful discussions of the material in this article.     

二维材料用于渗透能转换的研究进展

在河水与海水的交界处实现渗透能提取与捕获是解决未来能源危机的重要方式之一. 渗透能因为储量大, 容易获取以及绿色可持续的优势受到广泛关注. 反向电渗析技术是一种能够有效捕获渗透能的方法之一, 目前已经得到了深入的研究与发展. 离子交换膜是反向电渗析技术转换渗透能的关键组件, 其性能的优异程度决定能量转换效率的高低. 常见的膜材料主要是高分子聚合物及其改性化合物, 最近一些二维材料如石墨烯、 氧化石墨烯、 二硫化钼、 各种框架材料及其改性复合物因优异的选择性离子传输、 纳米级通道、 丰富的表面功能基团以及可修饰性成为捕获渗透能的重要膜材料. 本文综合评述了二维材料作为离子传输通道的类型以及相应的传输机理; 例举了二维材料及其复合物的设计方案和在渗透能转换方面的具体应用; 最后提出了目前二维材料在渗透能转换领域中面临的挑战以及未来的发展方向.     

Optimizing Membranes for Osmotic Power Generation

The design of ion-selective membranes is the key towards efficient reverse electrodialysis-based osmotic power conversion. The tradeoff between ion selectivity (output voltage) and ion permeability (output current) in existing porous membranes, however, limits the upgradation of power generation efficiency for practical applications. Thus, we provide the simple guidelines based on fundamentals of ion transport in nanofluidics for promoting osmotic power conversion. In addition, we discuss strategies for optimizing membrane performance through analysis of various material parameters in membrane design, such as pore size, surface charge, pore density, membrane thickness, ion pathway, pore order, and ionic diode effect. Lastly, a perspective on the future directions of membrane design to further maximize the efficiency of osmotic power conversion is outlined.     

Study on liquid oxygen compatibility of bromine‐containing epoxy resins for the application in liquid oxygen tank

The liquid oxygen compatible epoxy resin was obtained by the polycondensation between tetrabromobisphenol A and neat epoxy resins. The results of liquid oxygen impact test indicated that the synthetic epoxy resins were compatible with liquid oxygen. The relationship between impact reaction sensitivity (IRS) and flame retardancy were studied by liquid oxygen impact test and limiting oxygen index test. The results showed that the flame‐retardant modification of epoxy resin was valuable to reduce the IRS. The thermal gravimetric analysis results indicated that the Br · radical was quickly released in relatively low temperature (approximately 370°C) for compatible epoxy resin. The Br · radical was a key factor to promote the epoxy resin compatible with the liquid oxygen. The X‐ray photoelectron spectroscopy was used to survey the distribution of functional groups on the surface of samples before and after impact. The results showed that the oxidation reaction and carbonization process may occur on the surface of samples after impact. The liquid oxygen compatibility mechanism is proposed in this paper. The bromine‐containing epoxy resin has the potential to be the material used in liquid oxygen tank. Copyright © 2015 John Wiley & Sons, Ltd.     

Heat treatment bimetallic PdAu nanocatalyst for oxygen reduction reaction

Pd-based nanocatalyst is a potential oxygen reduction oxidation(ORR)catalyst because of its high activity in alkaline medium and low cost.In this work,bimetallic Pd Au nanocatalysts are prepared by one-pot hydrothermal method using triblock pluronic copolymers,poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide)(PEO_(19)-PPO_(69)-PEO_(19))(P123)as reducer and stabilizer,and heat-treatment method is applied to regulate catalyst structure and improve catalyst activity.The results show that the heat treatment can agglomerate the catalyst to a certain extent,but effectively improve the crystallinity and alloying degree of the catalyst.The ORR performance of the Pd Au nanocatalysts obtained under different heat treatment conditions is systematically investigated.Compared with commercial Pd black and Pd Au catalyst before heat treatment,the ORR performance of Au Pd nanocatalyst obtained after heat treatment for one hour at 500°C has been enhanced.The Pd Au nanocatalysts after heat treatment also display enhanced anti-methanol toxicity ability in acidic medium.     

The application of schlieren optics for detection of protein bands and other phenomena in polyacrylamide gel electrophoresis

A modernized schlieren optics system was applied to follow protein bands visually during polyacrylamide gel electrophoresis. This approach is suitable for quantitative measurement of electrophoresis as well as for detection of protein bands because of the absence of distortion of the electrophoretic pattern during the staining process. The optics are also suitable for the detection of various background phenomena which usually escape observation.     

Dispersion phenomena in reactors for flow analysis

Both coiled open tubular reactors and packed-bed reactors can be used in flow analysis. Band broadening and pressure drop in these reactors are discussed. Theoretical analysis shows that packed-bed reactors are to be preferred. It is shown that for a given residence time and equal band-broadening values the pressure drop over a packed-bed reactor is lower than over a coiled open tubular reactor. Rules for optimal design are given for coiled tubular reactors and packed-bed reactors. The application of both reactors is shown for the spectrophotometric determination of phosphate with a vanadomolybdate reagent yielding a yellow colour.     

Osmotic flow in charged membranes

Summary The osmotic flow through a porous charged membrane separating electrolyte solutions of different concentrations but at a constant temperature is studied theoretically, using a capillary model for the membrane. The assumptions used are that theDebye-Hückel approximation is applicable for the ion distribution in the double layer formed near the fixed charges on the capillary wall, and that the thickness of the double layer is much smaller than the capillary radius. The steady state solutions of the differential equations derived are obtained subject to the external conditions that the concentrations of the outer solutions are maintained constant and no pressure head is applied across the membrane. It is shown that the volume rate of osmotic flow is the sum of two terms, one arising from the fact that the membrane is electrically charged and the other being independent of the membrane charge and thus observable commonly both in charged and uncharged membranes. The former corresponds to whatGrim andSollner have referred to as the true anomalous osmosis. The plot of this electric part of osmosis against the logarithm of the concentration of one outer solution gives a bell-shaped curve, when the concentration ratio of the outer solutions is fixed. This theoretical curve follows well theGrim-Sollner data of the true anomalous osmosis for various aqueous electrolyte solutions. The true anomalous osmosis is an electro-osmotic flow caused by the electric field which is set up inside the membrane so that no net transport of electric charge occurs from one solution compartment to the other. The dependence of the electroosmotic coefficient on salt concentration is responsible for the characteristic behavior of the osmotic flow rates through charged membranes.

---

Zusammenfassung Der osmotische Flu\ durch eine poröse geladene Membran, die die Elektrolytlösungen verschiedener Konzentrationen, doch von konstanter Temperatur trennt, wird theoretisch untersucht unter Anwendung eines Kapillarmodells für die Membran. Die verwendeten Annahmen sind die, da\Debye-Hückel-NÄherung für die Ionenverteilung in der Doppelschicht, die sich in der NÄhe der fixierten Ladungen an der Kapillarwand bildet, verwendet werden kann und da\ die Dicke dieser Doppelschicht viel kleiner als der Kapillarradius ist. Die stationÄren Lösungen der abgeleiteten Differentialgleichungen werden unter der Bedingung erhalten, da\ die Konzentrationen der Äu\eren Lösungen konstant sind und keine Druckdifferenz über die Membran existiert. Es wird gezeigt, da\ die Volumendurchtritts-geschwindigkeit des osmotischen Flusses aus zwei Anteilen besteht, der eine auf Grund der Tatsache, da\ die Membran elektrisch geladen ist, der andere unabhÄngig von der Membranladung, und da\ gewöhnlich beide in geladenen und ungeladenen Membranen beobachtet werden können. Erstere entspricht dem, wasGrim undSollner als wahre anomale Osmose bezeichnen. Die Auftragung dieses elektrischen Teils gegen den Logarithmus der Konzentration der einen Äu\eren Lösung gibt eine Glockenkurve, wenn das KonzentrationsverhÄltnis der Äu\eren Lösungen fixiert ist. Diese theoretische Kurve folgt gut den Ergebnissen vonGrim-Sollner für die wahre anomale Osmose für verschiedene wÄ\rige Elektrolytlösungen. Die wahre anomale Osmose ist ein elektro-osmotischer Strom auf Grund des elektrischen Feldes, das innerhalb der Membran aufgebaut wird, so da\ kein Nettotransport elektrischer Ladungen von einer Lösung zur anderen stattfindet. Die AbhÄngigkeit des elektro-osmotischen Koeffizienten von der Salzkonzentration ist für das charakteristische Verhalten osmotischer Flie\geschwindigkeiten durch die geladene Membran verantwortlich.

     

BOD5荧光测定法与标准方法在地表水监测中的对比性研究

BOD₅检测是一种基于微生物的污染负荷评估,有文献证明微生物代谢物类色氨酸的荧光强度与BOD₅测量之间存在相关性. 对长江流域常州段地表水水样的荧光强度与BOD₅值之间的关系进行了探究,并通过考察浊度、pH、离子干扰和区域差异来评估荧光法应用于水质BOD₅污染评价中的潜力. 研究发现,地表水的pH和离子干扰对荧光法检测BOD₅并不构成明显影响. 区域差异对比结果t最大值为1.227,不构成显著性差异. 荧光法水样检测结果与标准方法相比,相关性系数r为0.909 9,具有明显相关性. 结果表明,荧光法应用于地表水BOD₅检测影响因素少、检测速度快、自动化程度高、结果稳定可靠,可以作为BOD₅检测的替代方法,成为表征水中可生物降解污染物污染程度的主要手段.

     

Preparation of mesocellular carbon foam and its application for lithium/oxygen battery

A mesocellular carbon foam (MCF-C) was prepared by nanocasting technology using mesocellular foam (MCF) silica hard template. The obtained carbon sample exhibits bimodal mesopores with narrow pore size distribution, centered at 4.3 and 30.4 nm. The MCF-C was evaluated as positive electrode in lithium/oxygen battery. It showed a higher discharge capacity, about 40% increased capacity compared to several commercial carbon black. The enhanced performance is probably ascribed to their large pore volumes and ultra-large mesoporous structures, which allow more lithium oxide deposit during discharge process.     

Transport phenomena in membranes

The realization that many elementary biological processes occur at membrane-like structures has led to renewed interest in the theory of molecular transport through membranes. Coupling phenomena in membranes, some of which are very complex, can now be rationally described with the aid of the thermodynamics of irreversible processes. The investigation of theoretical membrane models has proved a valuable complement to the thermodynamic method.     

Electrolysis phenomena in electrophoresis

We present a new theoretical approach for calculating changes in the physico-chemical properties of BGEs for measurements by CZE due to the electrolysis in electrode vials (vessels). Electrolysis is an inevitable phenomenon in any measurement in CZE. Water electrolysis, which occurs in most measurements, can significantly alter the composition of the BGE in electrode vials and in the separation capillary and has a negative influence on the robustness and quality of separations. The ability to predict changes in the composition of the BGE is important for evaluation of the suitability of the BGEs for repeating electrophoretic runs. We compared theoretically calculated changes in the physico-chemical properties (pH, conductivity) with those measured using pH-microelectrode and contactless conductivity detection of the BGE after the electrophoretic run. We confirmed the validity of our theoretical approach with a common BGE composed of acid-base pair, where one constituent is fully dissociated while the second constituent is dissociated by only half, and with Good's buffer. As predicted by theoretical approach, the changes in the physico-chemical properties of the Good's buffer after the electrophoretic run were several times lower than in the case of a common BGE composed of a weak acid – strong base pair.     

Isomorphism in critical phenomena

A dielectric liquid in a low external field is considered from the point of view of the effect of hidden variables on critical thermodynamic functions. Isomorphism is satisfied within scaling theory.     

Advances in interfacial phenomena of particulate/solution/gas systems; application to flotation research

Ohne Zusammenfassung

---

Advances in interfacial phenomena of particulate/solution/gas systems; application to flotation research

     

Electrochemical deposition of cabbage-like lead microstructures on fluorine-doped tin oxide for oxygen sensor application

Journal of Solid State Electrochemistry - Metallic lead (Pb) has been electrodeposited on FTO substrate at room temperature from aqueous nitrate solution under constant applied potential in the...