Enzyme-catalyzed cationic epoxide rearrangements in quinolone alkaloid biosynthesis.

Epoxides are highly useful synthons and biosynthons for the construction of complex natural products during total synthesis and biosynthesis, respectively. Among enzyme-catalyzed epoxide transformations, a reaction that is notably missing, in regard to the synthetic toolbox, is cationic rearrangement that takes place under strong acid. This is a challenging transformation for enzyme catalysis, as stabilization of the carbocation intermediate upon epoxide cleavage is required. Here, we discovered two Brønsted acid enzymes that can catalyze two unprecedented epoxide transformations in biology. PenF from the penigequinolone pathway catalyzes a cationic epoxide rearrangement under physiological conditions to generate a quaternary carbon center, while AsqO from the aspoquinolone pathway catalyzes a 3-exo-tet cyclization to forge a cyclopropane-tetrahydrofuran ring system. The discovery of these new epoxide-modifying enzymes further highlights the versatility of epoxides in complexity generation during natural product biosynthesis

Management controls in automotive international joint ventures involving Chinese parent companies

Key findings: • Flexibility in international joint ventures (JVS) is important and a shared but split control style is recommended. • Chinese partners used to have learning as their main objective in an IJV but this has been replaced by profit, growth and market share. • The most significant shifts in control between partners involve human resource management and research and development. • When foreign partners insist on adherence to their own management philosophy, culture clashes occur. • Negotiation is a part of daily life in the IJVs, and it occurs at both executive and managerial levels, depending upon the significance of the item

HDIdx: High-Dimensional Indexing for Efficient Approximate Nearest Neighbor Search

Fast Nearest Neighbor (NN) search is a fundamental challenge in large-scale data processing and analytics, particularly for analyzing multimedia contents which are often of high dimensionality. Instead of using exact NN search, extensive research efforts have been focusing on approximate NN search algorithms. In this work, we present "HDIdx", an efficient high-dimensional indexing library for fast approximate NN search, which is open-source and written in Python. It offers a family of state-of-the-art algorithms that convert input high-dimensional vectors into compact binary codes, making them very efficient and scalable for NN search with very low space complexity

Flare magnetic reconnection and relativistic particles in the 2003 October 28 event

An X17.2 solar flare occurred on 2003 October 28, accompanied by multi-wavelength emissions and a high flux of relativistic particles observed at 1AU. We present the analytic results of the TRACE, SOHO, RHESSI, ACE, GOES, hard X-ray (INTEGRAL satellite), radio (Onderejov radio telescope), and neutron monitor data. It is found that the inferred magnetic reconnection electric field correlates well with the hard X-ray, gamma-ray, and neutron emission at the Sun. Thus the flare's magnetic reconnection probably makes a crucial contribution to the prompt relativistic particles, which could be detected at 1 AU. Since the neutrons were emitted a few minutes before the injection of protons and electrons, we propose a magnetic-field evolution configuration to explain this delay. We do not exclude the effect of CME-driven shock, which probably plays an important role in the delayed gradual phase of solar energetic particles.Comment: 5 pages, 7 figures, accepted by A&

Platinum‐ and CuOₓ-Decorated TiO₂ Photocatalyst for Oxidative Coupling of Methane to C₂ Hydrocarbons in a Flow Reactor

Oxidative coupling of methane (OCM) is considered one of the most promising catalytic technologies to upgrade methane. However, C_{2} products (C_{2}H_{6}/C_{2}H_{4}) from conventional methane conversion have not been produced commercially owing to competition from overoxidation and carbon accumulation at high temperatures. Herein, we report the codeposition of Pt nanoparticles and CuO_{x} clusters on TiO_{2} (PC‐50) and use of the resulting photocatalyst for OCM in a flow reactor operated at room temperature under atmospheric pressure for the first time. The optimized Cu_{0.1}Pt_{0.5}/PC‐50 sample showed a highest yield of C_{2} product of 6.8 μmol h^{−1} at a space velocity of 2400 h^{−1}, more than twice the sum of the activity of Pt/PC‐50 (1.07 μmol h^{−1}) and Cu/PC‐50 (1.9 μmol h^{−1}), it might also be the highest among photocatalytic methane conversions reported so far under atmospheric pressure. A high C_{2}. selectivity of 60 % is also comparable to that attainable by conventional high‐temperature (>943 K) thermal catalysis. It is proposed that Pt functions as an electron acceptor to facilitate charge separation, while holes could transfer to CuO_{x} to avoid deep dehydrogenation and the overoxidation of C_{2} products