618 research outputs found

    Biomimetic Homogeneous Oxidation Catalyzed by Metalloporphyrins with Green Oxidants

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    Cytochrome P-450 mono-oxygenase enzymes play a key role in the oxidative transformation in living systems. As one kind of cytochrome P-450 models, metalloporphyrins have been widely used in selective oxygenation of hydrocarbons under mild conditions. The chapter focuses on reviewing the biomimetic homogeneous oxidation of organic compounds catalyzed by metalloporphyrins with green oxidants such as dioxygen or hydrogen peroxide, in which the oxidized substrates include alkanes, olefins, alcohols, aldehydes, sulfides etc. The mechanisms for the oxidation of different substrates were also described. We can assume that the coming decade is going to be dedicated to the development of metalloporphyrins biomimetic catalyst in petrochemical and fine chemical industries. Keywords: Biomimetic, Cytochrome, Metalloporphyrins, Oxidation, Homogegeou

    Admissibility of Estimated Regression Coefficients Under Generalized Balanced Loss

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    There are some discussions concerning the admissibility of estimated regression coefficients under the balanced loss function in the general linear model. We study this issue for the generalized linear regression model. First, we propose a generalized weighted balance loss function for the generalized linear model. For the proposed loss function, we study sufficient and necessary conditions for the admissibility of the estimated regression coefficients in two interesting linear estimation classes.Ведуться дєякі дискусії щодо допустимості оцінєних коєфіцієнтів регресії для збалансованої функції втрат у загальній лінійній моделі. В роботі вивчається ця проблема для узагальненої лінійної моделі регресії. Так, запропоновано узагальнену зважену функцію втрати балансу для узагальненої лінійної моделі. Для вказаної функції втрат ми вивчаємо необхідні та достатні умови допустимості оцінених коефіцієнтів регресії для двох цікавих лінійних випадків оцінювання

    Periodic Radio Variability in NRAO 530: Phase Dispersion Minimization Analysis

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    In this paper, a periodicity analysis of the radio light curves of the blazar NRAO 530 at 14.5, 8.0, and 4.8 GHz is presented employing an improved Phase Dispersion Minimization (PDM) technique. The result, which shows two persistent periodic components of 6 \sim 6 and 10 \sim 10 years at all three frequencies, is consistent with the results obtained with the Lomb-Scargle periodogram and weighted wavelet Z-transform algorithms. The reliability of the derived periodicities is confirmed by the Monte Carlo numerical simulations which show a high statistical confidence. (Quasi-)Periodic fluctuations of the radio luminosity of NRAO 530 might be associated with the oscillations of the accretion disk triggered by hydrodynamic instabilities of the accreted flow. \keywords{methods: statistical -- galaxies: active -- galaxies: quasar: individual: NRAO 530}Comment: 8 pages, 5 figures, accepted by RA

    Solvent-free selective oxidation of primary and secondary alcohols catalyzed by ruthenium-bis(benzimidazole)pyridinedicarboxylate complex using hydrogen peroxide as an oxidant

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    AbstractA convenient and selective oxidation of alcohols with aqueous hydrogen peroxide to give the corresponding carbonyl compounds under solvent-free conditions has been developed. By applying ruthenium-bis(benzimidazole)pyridinedicarboxylate complex [Ru(bbp)(pydic)] as catalyst, primary, and secondary alcohols were oxidized to aldehydes and ketones in good yield and excellent selectivity under mild conditions

    Poly[tetra­kis(2,2′-bipyridine)undeca-μ-oxido-hexa­oxidodicopper(II)hexa­vanadium(V)]

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    In the title organic–inorganic hybrid vanadate complex, [Cu2V6O17(C10H8N2)4]n, the CuII atom is six-coordinated by two chelating 2,2′-bipyridine (bipy) ligands and two vanadate O atoms in a distorted octa­hedral geometry. Two [Cu(bipy)2V3O8] units are linked by a bridging O atom, which lies on an inversion center, forming a dimeric unit. The dimeric units are further connected by bridging vanadate O atoms into a two-dimensional layer parallel to (100). The layers are connected by weak C—H⋯O hydrogen bonds

    Analytical Studies on a Modified Nagel-Schreckenberg Model with the Fukui-Ishibashi Acceleration Rule

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    We propose and study a one-dimensional traffic flow cellular automaton model of high-speed vehicles with the Fukui-Ishibashi-type (FI) acceleration rule for all cars, and the Nagel-Schreckenberg-type (NS) stochastic delay mechanism. By using the car-oriented mean field theory, we obtain analytically the fundamental diagrams of the average speed and vehicle flux depending on the vehicle density and stochastic delay probability. Our theoretical results, which may contribute to the exact analytical theory of the NS model, are in excellent agreement with numerical simulations.Comment: 3 pages previous; now 4 pages 2 eps figure

    Multi-object tracking with robust object regression and association

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    Tracking-by-regression is a new paradigm for online Multi-Object Tracking (MOT). It unifies detection and tracking into a single network by associating targets through regression, significantly reducing the complexity of data association. However, owing to noisy features from nearby occlusions and distractors, the regression is vulnerable and unaware of the inter-object occlusions and intra-class distractors. Thus the regressed bounding boxes can be wrongly suppressed or easily drift. Meanwhile, the commonly used bounding box-based post-processing is unable to remedy false negatives and false assignments caused by regression. To address these challenges, we present to leverage regression tubes as input for the regression-based tracker, which provides spatial–temporal information to enhance the tracking performance. Specially, we propose a novel tube re-localization strategy that obtains robust regressions and recovers missed targets. A tube-based NMS (T-NMS) strategy to manage the regressions at the tube level is also proposed, including a tube IoU (T-IoU) scheme for measuring positional relation and tube re-scoring (T-RS) to evaluate the quality of candidate tubes. Finally, a tube re-assignment strategy is further employed for robust cost measurement and to revise false assignments using motion cues. We evaluate our method on benchmarks, including MOT16, MOT17, and MOT20. The results show that our method can significantly improve the baseline, mitigate the challenges of the regression-based tracker, and achieve very competitive tracking performance.</p
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