Self‐Limiting Galvanic Growth of MnO2 Monolayers on a Liquid Metal—Applied to Photocatalysis

Liquid metals offer unprecedented chemistry. Here it is shown that they can facilitate self‐limiting oxidation processes on their surfaces, which enables the growth of metal oxides that are atomically thin. This claim is exemplified by creating atomically thin hydrated MnO₂ using a Galvanic replacement reaction between permanganate ions and a liquid gallium–indium alloy (EGaIn). The “liquid solution”–“liquid metal” process leads to the reduction of the permanganate ions, resulting in the formation of the oxide monolayer at the interface. It is presented that under mechanical agitation liquid metal droplets are established, and simultaneously, hydrated gallium oxides and manganese oxide sheets delaminate themselves from the interfacial boundaries. The produced nanosheets encapsulate a metallic core, which is found to consist of solid indium only, with the full migration of gallium out of the droplets. This process produces core/shell structures, where the shells are made of stacked atomically thin nanosheets. The obtained core/shell structures are found to be an efficient photocatalyst for the degradation of an organic dye under simulated solar irradiation. This study presents a new research direction toward the modification and functionalization of liquid metals through spontaneous interfacial redox reactions, which has implications for many applications beyond photocatalysis.     

A new reference for wind power forecasting

In recent years some research towards developing forecasting models for wind power or energy has been carried out. In order to evaluate the prediction ability of these models, the forecasts are usually compared with those of the persistence forecast model. As shown in this article, however, it is not reasonable to use the persistence model when the forecast length is more than a few hours. Instead, a new statistical reference for predicting wind power, which basically is a weighting between the persistence and the mean of the power, is proposed. This reference forecast model is adequate for all forecast lengths and, like the persistence model, requires only measured time series as input. Copyright © 1998 John Wiley & Sons, Ltd.     

Can the centre–periphery model explain patterns of international scientific collaboration among threshold and industrialised countries? The case of South Africa and Germany

As scientific collaboration is a phenomenon that is becoming increasingly important, studies on scientific collaboration are numerous. Despite the proliferation of studies on various dimensions of collaboration, there is still a dearth of analyses on the effects, motives and modes of collaboration in the context of developing countries. Adopting Wallerstein’s world-system theory, this paper makes use of bibliometric data in an attempt to understand the pattern of collaboration that emerges between South Africa and Germany. The key argument is that we can expect the collaborative relationship between South Africa and Germany to be one that is shaped by a centre–periphery pattern. The analyses show that a theory of scientific collaboration building on the notion of marginality and centre–periphery can explain many facets of South African–German collaboration, where South Africa is a semi-peripheral region, a centre for the periphery, and a periphery for the centre.     

An alternative characterization of weak order dependence

Control dependence forms the basis for many program analyses, such as program slicing. Recent work on control dependence analysis has led to new definitions of dependence that can allow for reactive programs with their necessarily non-terminating computations. One important such definition is the definition of Weak Order Dependence, which was introduced to generalize classical control dependence for a Control Flow Graph (CFG) without end nodes. In this paper we show that for a CFG where all nodes are reachable from each other, weak order dependence can be expressed in terms of traditional control dependence where one node has been converted into an end node.     

Hydrolysis of Pure and Sodium Substituted Calcium Aluminates and Cement Clinker Components Investigated by in Situ Synchrotron X-ray Powder Diffraction

The hydrolysis of pure and sodium-substituted calcium aluminates and cement clinker phases was investigated in situ in the temperature range 25°–170°C, using the angle dispersive powder synchrotron powder X-ray diffraction technique. The final hydrolysis product in all cases was Ca₃Al₂(OH)₁₂. The intermediate phase Ca₄Al₂O₇·19H₂O was formed from the pure calcium aluminates, and the intermediate phases Ca₄Al₂O₇· x H₂O, x = 11, 13, or 19, were formed from the cement clinker phases.     

Do investments in flexibility enhance sustainability? A simulative study considering the German electricity sector

Current research concerning industrial demand side management primarily focuses on monetary aspects. Herein, we extend this perspective by assessing whether economically driven measures increasing the flexibility also result in reduced contributions to the residual load. For this purpose, we conduct a simulative study using historic and projected time series for the German electricity sector. First, Fourier analysis are performed to show that the main oscillation in the electricity price time series has a period length of 12 hr, whereas the renewable generation is primarily characterized by an oscillation with a period length of 24 hr. Second, a generic process model with capabilities for load shiftings is used to evaluate how the fluctuation patterns can be exploited via scheduling optimizations. Most importantly, our results demonstrate that prevalent price fluctuations prevent adequate monetary incentives for providing storage capacities for bridging up to 24 hr, which are desired for reducing the residual load.     

Are firms withdrawing from basic research? An analysis of firm-level publication behaviour in Germany

Scientometrics - Previous research has expressed concerns about firms engaging less in basic research. We contribute to this debate by studying trends in the scientific publishing activities of...     

Chloride Ion Mediated Synthesis of Metal/Semiconductor Hybrid Nanocrystals

A synthetic route to prepare metal–semiconductor hybrid nanoparticles is presented, along with the possibility to tune the ratio of primary to secondary nucleation and the morphology of the semiconductor material grown on the metal nanoparticle seeds. Gold and cobalt‐platinum nanoparticles are employed as metal seeds, on which CdS or CdSe is grown. Using transmission electron microscopy, absorption spectroscopy (UV–vis), and powder X‐ray diffraction as characterization techniques, a significant influence of chloride ions on the type of nucleation (that is, secondary or primary nucleation) as well as on the shape of the resulting heterostructures is observed. Partially replacing the commonly used cadmium precursor CdO by varying amounts of CdCl₂ opens access to rod‐like, multiarmed, flower‐like, and bullet‐like structures. The results suggest that neither pure CdO nor pure CdCl₂ as precursors but only a mixture of both make these structures obtainable. In this article, the influence of the chloride ion concentration during semiconductor growth on metal seeds is investigated in depth. The morphology of the resulting heterostructures is characterized carefully, and a growth mechanism is suggested. Furthermore, it is shown that this synthetic approach can be transferred to seeds of various metals such as platinum, gold, and cobalt platinum.     

Mining Long, Sharable Patterns in Trajectories of Moving Objects

The efficient analysis of spatio-temporal data, generated by moving objects, is an essential requirement for intelligent location-based services. Spatio-temporal rules can be found by constructing spatio-temporal baskets, from which traditional association rule mining methods can discover spatio-temporal rules. When the items in the baskets are spatio-temporal identifiers and are derived from trajectories of moving objects, the discovered rules represent frequently travelled routes. For some applications, e.g., an intelligent ridesharing application, these frequent routes are only interesting if they are long and sharable, i.e., can potentially be shared by several users. This paper presents a database projection based method for efficiently extracting such long, sharable frequent routes. The method prunes the search space by making use of the minimum length and sharable requirements and avoids the generation of the exponential number of sub-routes of long routes. Considering alternative modelling options for trajectories, leads to the development of two effective variants of the method. SQL-based implementations are described, and extensive experiments on both real life- and large-scale synthetic data show the effectiveness of the method and its variants.