Spontaneous Reductive Elimination at Iridium(III) Induced by the Strong π‐Acceptor Ligand Trifluorophosphane

The reaction of the cyclometalated five‐coordinate 16 VE iridium(III) compound [IrCl(H)(P(tBu)2C6H4‐κ2P,C)(P(tBu)2Ph)] (1) with the strong π‐acceptor ligand trifluorophosphane resulted quickly in the quantitative formation of the new iridium(I) complex trans‐[IrCl(PF3)(P(tBu)2Ph)2] (2). This unexpected spontaneous reductive elimination was already observed in reactions of 1 with the very strong π‐acceptor ligands CO and NO+. First indications during reactions of 1 with lesser strong π‐acceptor ligands like alkyl or arylphosphanes did not show this inversion behavior of the cyclometalation. The title species 2 was characterized by spectroscopic methods and its molecular structure in the crystal was confirmed by X‐ray crystallography

FabricCRDT: A Conflict-Free Replicated Datatypes Approach to Permissioned Blockchains

With the increased adaption of blockchain technologies, permissioned blockchains such as Hyperledger Fabric provide a robust ecosystem for developing production-grade decentralized applications. However, the additional latency between executing and committing transactions, due to Fabric's three-phase transaction lifecycle of Execute-Order-Validate (EOV), is a potential scalability bottleneck. The added latency increases the probability of concurrent updates on the same keys by different transactions, leading to transaction failures caused by Fabric's concurrency control mechanism. The transaction failures increase the application development complexity and decrease Fabric's throughput. Conflict-free Replicated Datatypes (CRDTs) provide a solution for merging and resolving conflicts in the presence of concurrent updates. In this work, we introduce FabricCRDT, an approach for integrating CRDTs to Fabric. Our evaluations show that in general, FabricCRDT offers higher throughput of successful transactions than Fabric, while successfully committing and merging all conflicting transactions without any failures.Comment: In Proceedings of the 20th International Middleware Conference (Middleware '19). ACM 201

Wie arbeiten Schüler in den naturwissenschaftlichen Fächern ? : Lernforschung in der Schule und im Schülerlabor Biologie als Grundlage zukünftiger Schulentwicklung

Wissenschaftsmethodische Kompetenzen und ein wissenschaftstheoretisches Verständnis der Naturwissenschaften sind Teil einer naturwissenschaftlichen Bildung. Ob Schülerinnen und Schüler diese Kompetenzen bis zum Ende ihrer Schullaufbahn überhaupt entwickeln ist aber weitgehend unbekannt. Am Institut für Biologiedidaktik arbeitet seit 2001 die Arbeitsgruppe „Wissenschaftliche Arbeitsweisen im Biologieunterricht“ an dem Ziel, aus der Sicht der Fachdidaktik Biologie grundlegende Variablen des naturwissenschaftlichen Arbeitsprozesses bei Schülern zu identifizieren, modellhaft abzubilden und theoretisch zu fassen. Ein wichtiges Instrument war dabei – neben der Feldforschung – die Einrichtung eines Schüler-Labors zur Erforschung von Schülergruppen unter standardisierten Bedingungen

OrderlessChain: Do Permissioned Blockchains Need Total Global Order of Transactions?

Existing permissioned blockchains often rely on coordination-based consensus protocols to ensure the safe execution of applications in a Byzantine environment. Furthermore, these protocols serialize the transactions by ordering them into a total global order. The serializability preserves the correctness of the application's state stored on the blockchain. However, using coordination-based protocols to attain the global order of transactions can limit the throughput and induce high latency. In contrast, application-level correctness requirements exist that are not dependent on the order of transactions, known as invariant-confluence (I-confluence). The I-confluent applications can execute in a coordination-free manner benefiting from the improved performance compared to the coordination-based approaches. The safety and liveness of I-confluent applications are studied in non-Byzantine environments, but the correct execution of such applications remains a challenge in Byzantine coordination-free environments. This work introduces OrderlessChain, a coordination-free permissioned blockchain for the safe and live execution of I-confluent applications in a Byzantine environment. We implemented a prototype of our system, and our evaluation results demonstrate that our coordination-free approach performs better than coordination-based blockchains

Reactivity of Cyanide and Thiocyanate Towards the Nitrosyl Carbonyl [Co(CO)3(NO)]

The reaction of equimolar amounts of [Co(CO)3(NO)] and [PPN]CN, PPN+ = (PPh3)2N+, in THF at room temperature resulted in ligand substitution of a carbonyl towards the cyanido ligand presumably affording the complex salt PPN[Co(CO)2(NO)(CN)] as a reactive intermediate species which could not be isolated. Applying the synthetic protocol using the nitrosyl carbonyl in excess, the title reaction afforded unexpectedly the novel complex salt PPN[Co2(μ‐CN)(CO)4(NO)2] (1) in high yield. Because of many disorder phenomena in crystals of 1 the corresponding NBu4+ salt of 1 has been prepared and the molecular structure of the dinuclear metal core in NnBu4[Co2(μ‐CN)(CO)4(NO)2] (2) was determined by X‐ray crystal diffraction in a more satisfactory manner. In contrast to the former result, the reaction of [PPN]SCN with [Co(CO)3(NO)] yielded the mononuclear complex salt PPN[Co(CO)2(NO)(SCN‐κN)] (3) in good yield whose molecular structure in the solid was even determined and its composition additionally confirmed by spectroscopic means

MANAGERS AND COLLABORATION TECHNOLOGY: A BUSINESS PERSPECTIVE FOR IMPROVING MANAGEMENT SUPPORT SYSTEMS

Over the last years managers have expanded their role in operations and nowadays they make decisions faster than in the past. Collaboration technology promises to support managers in doing so. Hence, the present situation is favorable for a redesign of management support systems (MSS) incorporating collaboration technology. To examine such technology, we consider analyst - and consumer -type managers´ perspectives and cover collaboration technology for different devices. Based on findings from a literature review and arguments validated in structured manager interviews, we propose four initial design guidelines facilitating collaboration for managers: (1) Coordination: MSS should indicate the availability of other users, send read confirmations, and provide document sharing. (2) Communication: MSS should enable on-topic annotations and sending them to other users at the push of a button. (3) Cooperation: MSS should provide a comprehensive managerial self-service search function. (4) Devices: For shared documents and textual annotations tablets have become managers most wanted smart device type

The Evolution of Distributed Systems for Graph Neural Networks and their Origin in Graph Processing and Deep Learning: A Survey

Graph Neural Networks (GNNs) are an emerging research field. This specialized Deep Neural Network (DNN) architecture is capable of processing graph structured data and bridges the gap between graph processing and Deep Learning (DL). As graphs are everywhere, GNNs can be applied to various domains including recommendation systems, computer vision, natural language processing, biology and chemistry. With the rapid growing size of real world graphs, the need for efficient and scalable GNN training solutions has come. Consequently, many works proposing GNN systems have emerged throughout the past few years. However, there is an acute lack of overview, categorization and comparison of such systems. We aim to fill this gap by summarizing and categorizing important methods and techniques for large-scale GNN solutions. In addition, we establish connections between GNN systems, graph processing systems and DL systems.Comment: Accepted at ACM Computing Survey