Trimetallic Mn‐Fe‐Ni Oxide Nanoparticles Supported on Multi‐Walled Carbon Nanotubes as High‐Performance Bifunctional ORR/OER Electrocatalyst in Alkaline Media

Discovering precious metal‐free electrocatalysts exhibiting high activity and stability toward both the oxygen reduction (ORR) and the oxygen evolution (OER) reactions remains one of the main challenges for the development of reversible oxygen electrodes in rechargeable metal–air batteries and reversible electrolyzer/fuel cell systems. Herein, a highly active OER catalyst, Fe_0.3Ni_0.7O_X supported on oxygen‐functionalized multi‐walled carbon nanotubes, is substantially activated into a bifunctional ORR/OER catalyst by means of additional incorporation of MnO_X. The carbon nanotube‐supported trimetallic (Mn‐Ni‐Fe) oxide catalyst achieves remarkably low ORR and OER overpotentials with a low reversible ORR/OER overvoltage of only 0.73 V, as well as selective reduction of O₂ predominantly to OH^?. It is shown by means of rotating disk electrode and rotating ring disk electrode voltammetry that the combination of earth‐abundant transition metal oxides leads to strong synergistic interactions modulating catalytic activity. The applicability of the prepared catalyst for reversible ORR/OER electrocatalysis is evaluated by means of a four‐electrode configuration cell assembly comprising an integrated two‐layer bifunctional ORR/OER electrode system with the individual layers dedicated for the ORR and the OER to prevent deactivation of the ORR activity as commonly observed in single‐layer bifunctional ORR/OER electrodes after OER polarization.     

The behaviour of styrenes p-substituted with a liquid crystalline side group under anionic polymerization conditions

Summary The synthesis of p-alkyloxymethylstyrenes and p-alkyloxystyrenes with 4,4-disubstituted-biphenyl or 2,5-disubstituted-1,3-dioxane groups as side chains are described. The phase behaviour of both the monomers and polymers obtained by free radical polymerizations is investigated.The monomers are not suitable for living anionic polymerizations because of the side reactions which occur as competitive reactions to the normal chain growth. The benzylic ether group of the alkyloxymethylstyrene was splited under the influence of the anionic centres. A metalation of the phenyl ring of the styryl group was observed for alkyloxystyrenes.     

Properties of PVC. II. Properties of PVC compounds with solvents

It was the aim of this paper to study the influence of the solvent residues in PVC compounds on physical and mechanical properties of samples prepared from them as well as the rheologic properties of their melts. Besides tetrahydrofuran other solvents are also partly retained in PVC even after processing at higher temperatures. The properties of samples prepared from PVC compounds containing solvents depend on the solubility parameter of the solvent used. Solvents with a solubility close to that of PVC have the same effect as plasticizers. Solvents with very high solubility parameters, e.g., water, influence the flow and dynamic properties in just the opposite way than plasticizers and behave rather like fillers. A mechanism for influencing the properties of PVC by the presence of solvent residues is suggested.     

The construction of new proteins

Recent progresses in the elucidation of the folding mechanism and topology of proteins revealed that the formation of folding units with specific topological features is not restricted to a unique primary sequence. This finding presents the basis for the design of polypeptides having the propensity to fold into a tertiary structure that can be achieved by the assembly of peptide blocks exhibiting stable secondary structures. Conformational studies on model peptides show that Aib containing peptides with chain-lengths of 12-15 residues are able to form stable amphiphilic helices in solution. On the other hand, oligopeptides with alternating hydrophilic and hydrophobic residues are capable for β-structure formation for chain-lengths of 6-8 residues. Those amphiphilic secondary structures have been used as building-blocks for the design and synthesis of artificial folding units, their amphiphilic nature acting as major driving force for intramolecular folding. Spectroscopic data obtained for two polypeptides designed as βαβ-models actually suggest a folded conformation of these molecules in aqueous solution. The implications of these findings for the design of biologically active folded polypeptides are discussed.     

Prioritization of pollution potential zones for conservation activities of a lake system

Many coastal lakes are under serious threats due to increased pressures associated with population growth, accelerated eutrophication, invasive species and toxic contamination. The extent of the pollution depends almost entirely on the characteristics and processes taking place in the lake basin. The objective of this study was to identify the pollution potential zones (very high, high, medium and low) in the Akkulam–Veli (A–V) Lake Basin (Thiruvananthapuram, Kerala) using GIS‐enabled, multithematic overlay analysis. The primary characteristics considered were geomorphology, lithology, land use, soil, slope and population density. The results of this study indicated the major portion of the lake basin exhibits very high or high pollution potential zones, with the drains passing through the very high pollution potential zone being mainly responsible for the contamination of the lake water. High population density, predominant commercial use and settlement with mixed tree crop, level and gentle slope (low slope) are the factors responsible for the very high pollution potential. The organic pollutants in the lake system increase with the increased extent of the very high pollution potential area. This analysis approach will help authorities to identify the underlying causes of lake water quality degradation and plan and implement effective measures for protecting the lake. This process can also be utilized by scientists elsewhere to facilitate lake protection.     

On the time lag of the effect of network position on service performance in software service networks

We examine whether a time lag exists before the network position of a software service affects its performance. Moreover, we analyze different time lags, using empirical data about software services and their usage for creating composite services. Our results show that software services in central positions (i.e., high betweenness centrality) attract users the most. The highest effect exhibits, if the time lag is 26–32 months. Our findings are relevant, as they can guide developers in marketing their software services and are expected to impact innovation studies regarding the importance of considering time lags and analyzing complementary knowledge.     

Can computer vision problems benefit from structured hierarchical classification?

Research in the field of supervised classification has mostly focused on the standard, so-called “flat” classification approach, where the problem classes live in a trivial, one-level semantic space. There is however an increasing interest in the hierarchical classification approach, where a performance gain is expected by incorporating prior taxonomic knowledge about the classes into the learning process. Intuitively, the hierarchical approach should be beneficial in general for the classification of visual content, as suggested by the fact that humans seem to organize objects into hierarchies based on visually perceived similarities. In this paper, we provide an analysis that aims to determine the conditions under which the hierarchical approach can consistently give better performances than the flat approach for the classification of visual content. In particular, we (1) show how hierarchical methods can fail to outperform flat methods when applied to real vision-based classification problems, and (2) investigate the underlying reasons for the lack of improvement, by applying the same methods to synthetic datasets in a simulation. Our conclusion is that the use of high-level hierarchical feature representations is crucial for obtaining a performance gain with the hierarchical approach, and that poorly chosen prior taxonomies hinder this gain even though proper high-level features are used.     

Variations in the contents of heavy metals in arable soils of a major urban wetland inlet drainage system of Lake Victoria,Uganda

Little is known about the effects of urbanization on the chemical quality of soils in suburban wetland inlet drainage systems to the Uganda side of Lake Victoria, on which food crops are extensively grown. It is feared that pollution in the soils might eventually enter food chains through such crops being consumed by urban populations unaware of their occurrence. Soil samples were collected from cultivated areas of a major wetland drainage system (Nakivubo Channel), at Kampala, Ubanda, near Lake Victoria and from a rural control wetland site (Senge). The soil from this site had similar properties as those from the urban test site (i.e., soil texture; porosity; humus content). Analysis of heavy metals with atomic absorption spectrophotometry (AAS) yielded the following soil concentration ranges: manganese (190–780), cadmium (<0.001–1.0), zinc (6.0–10.0) and lead (10–20 mg kg^?1) dry weight for the control site, and 450–900, 1.0–2.0, 131–185, 40–60 mg kg^?1 dry weight, respectively, for the urban wetland, indicative of relatively heavy metal pollution in the suburban drainage system. Heavy metal levels in cocoyam (Colocasia Esculenta) and sugarcane (Saccharum Officinarum) grown on both wetland soils also were evaluated via AAS with a modified wet‐acid‐digestion technique. The results highlighted high cadium and lead levels (P ≤ 0.0003) in the crops from urban wetland cultivation. Cadmium and lead concentrations in cocoyam from urban wetland soils exceeded those from the control site by 0.17 and 3.54 mg kg^?1, respectively. The corresponding results for sugarcane indicated a similar increase of 0.56 and 2.14 mg kg^?1 of juice extract. Cadmium and lead levels in both urban wetland crops were higher than the maximum permissible limits of the Codex Alimentarius Commission, indicating that these concentrations pose potential health risks to urban consumers, and call for early counter‐measures to combat urban pollution entering the lake.