150,973 research outputs found
Bi-Catalyzed Trifluoromethylation of C(sp<sup>2</sup>)–H Bonds under Light
No full textWe disclose a Bi-catalyzed
C–H trifluoromethylation of (hetero)arenes
using CF3SO2Cl under light irradiation. The
catalytic method permits the direct functionalization of various heterocycles
bearing distinct functional groups. The structural and computational
studies suggest that the process occurs through an open-shell redox
manifold at bismuth, comprising three unusual elementary steps for
a main group element. The catalytic cycle starts with rapid oxidative
addition of CF3SO2Cl to a low-valent Bi(I) catalyst,
followed by a light-induced homolysis of Bi(III)–O bond to
generate a trifluoromethyl radical upon extrusion of SO2, and is closed with a hydrogen-atom transfer to a Bi(II) radical
intermediate
Roles of bulk γ(L)-Bi₂MoO₆ and surface β-Bi₂Mo₂O₉ in the selective catalytic oxidation of C₃H₆
No full textγ(L)-Bi₂MoO₆ (L: low temperature phase) catalysts, whose surface compositions have a Mo/Bi ratio above = 0.5, exhibited high selectivity in the partial oxidation of C₃H₆, while catalysts with Mo/Bi surface ratios near or below = 0.5 exhibited low selectivity. γ(L)-phase catalysts which have Mo/Bi surface ratios greater than = 0.5, were demonstrated to form β-Bi₂Mo₂O₉ on their surface. An interaction between the β- and γ(L)-phases was observed in these catalysts’ UV–vis spectra at 430 nm. The new β-phase material seems to grow along b-axis of γ(L)-phase, i.e., perpendicular to MoO₂–Bi₂O₂ layers. Structure visualizations revealed that the α-Bi₂Mo₃O₁₂, β-, and γ(H)-phases, which are selective catalysts, contain twin Mo tetrahedral structures, and that their Mo and Bi ions lie on the same plane. The pure γ(L)-phase does not contain this structure. A model for the very rapid transfer of oxygen between the γ(L)- and β-phases is discussed in relation to the kinetics of C₃H₆ oxidation.ArticleJournal of molecular catalysis. A, Chemical. 318(1-2):94-100 (2010)journal articl
Mechanisms of H-2 generation for metal doped Al16M (M = Mg and Bi) clusters in water
No full textWe have systematically investigated the hydrolysis mechanism of metal doped Al16M (M = Al, Mg and Bi) clusters with H2O molecules and proposed a reasonable elucidation for the experimentally observed fast H-2 generation rate and high H-2 yield in the Al-Bi based composite. Mg and Bi showed negative effect on the dissociation process of the first H2O molecule, but accelerated further H-2 generation process. The investigation of persistent hydrolysis reactions demonstrated that the proton-transfer way makes the aluminum-water reaction a lasting process in the long-term H-2 generation in existence of Bi atom, which explains not only the previously observed fast H-2 generation rate but also high H-2 yields in the Bi added Al powder. Our experimental results of hydrogen generation form Al-Bi (Mg) mixture and water are in good agreement with the theory prediction. The facilitated hydrolysis reaction in Al16Bi cluster is attributed to the weakened hydroxide adsorption with the presence of Bi in the aluminum cluster, which is the key factor to accelerate the proton-transfer process. Copyright (c) 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved
A value for bi-cooperative games
No full textBi-cooperative games were introduced by Bilbao et al. as a generalization of TU cooperative games, in which each player can participate positively, negatively, or not at all. In this paper, we propose a definition of a share of the worth obtained by some players after they decided on their participation in the game. It turns out that the cost allocation rule does not look for a given player to her contribution at the opposite participation option to the one she chooses. The relevance of the value is discussed on several examples.Bi-cooperative games ;Value ;Efficiency
Concurrent bi-lateral negotiation in agent systems
No full textBi-lateral negotiations represent an important class of encounter in agent-based systems. To this end, this paper develops and evaluates a heuristic model that enables an agent to participate in multiple, concurrent bi-lateral encounters in competitive situations in which there is information uncertainty and deadlines
Evolutionary strategy based improved motion estimation technique for H.264 video coding
No full textIn this paper we propose an improved motion estimation algorithm based on evolutionary strategy (ES) for H.264 video codec applied to video. The proposed technique works in a parallel local search for macroblocks. For this purpose (mu+lambda) ES is used with an initial population of heuristically and randomly generated motion vectors. Experimental results show that the proposed scheme can reduce the computational complexity up to 50% of the motion estimation algorithm used in the H.264 reference codec at the same picture quality. Therefore, the proposed algorithm provides a significant improvement in motion estimation in the H.264 video codec
Tailoring cobalt‐free La <sub>0.5</sub> Sr <sub>0.5</sub> FeO <sub>3‐δ</sub> cathode with a nonmetal cation‐doping strategy for high‐performance proton‐conducting solid oxide fuel cells
No full textA nonmetal doping strategy was exploited for the conventional La0.5Sr0.5FeO3-δ (LSF) cathode, allowing high performance for proton-conducting solid oxide fuel cells (H-SOFCs). Unlike previous studies focusing on the utilization of metal oxides as dopants, phosphorus, which is a nonmetal element, was used as the cation dopant for LSF by partially replacing Fe ions to form the new La0.5Sr0.5Fe0.9P0.1O3-δ (LSFP) compound. The H-SOFC using the LSFP cathode showed a two-fold peak power density as compared to that using the LSF cathode. Both experimental studies and first-principle calculations were used to unveil the mechanisms for the high performance of the LSFP cells
On the bi-dimensionality of liquidity.
No full textVariations in overall liquidity can be measured by simultaneous changes in both immediacy costs and depth. Liquidity changes, however, are ambiguous whenever both liquidity dimensions do not reinforce each other. In this paper, ambiguity is characterized using an instantaneous time-varying elasticity concept. Several bi-dimensional liquidity measures that cope with the ambiguity problem are constructed. First, it is shown that bi-dimensional measures are superior since commonalities in overall liquidity cannot be fully explained by the common factors in one-dimensional proxies of liquidity. Second, it is shown that an infinitesimal variation in either market volatility or trading activity augments the probability of observing an unambiguous liquidity adjustment. Ambiguity strongly depends on the expected (deterministic) component of volatility.liquidity; measurement; immediacy; depth; elasticity; ambiguity; bi-dimensional;
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