Design of Photoactive Covalent Organic Frameworks as Heterogeneous Catalyst for Preparation of Thiophosphinates from Phosphine Oxides and Thiols

Two new covalent organic frameworks (COFs) were synthesized from 4,4′,4′′,4′′′-(pyrene-1,3,6,8-tetrayl)tetraaniline and 2,5-dimethoxyterephthalaldehyde (Py-DMTA-COF) or 2′,5′-dimethoxy-[1,1′:4′,1′′-terphenyl]-4,4′′-dicarbaldehyde (Py-DMTPDA-COF) under solvothermal conditions. These two COFs were further facilely developed as efficient photocatalytic platforms for the synthesis of thiophosphinates. Py-DMTA-COF exhibited better photocatalytic activity, broad substrate applicability, and excellent recycling capacity for the preparation of thiophosphinates from P(O)H compounds and thiols compared to Py-DMTPDA-COF. This methodology was further extended to the seamless gram-scale production of target phosphorothioate derivatives. The results demonstrate that COFs can provide a robust platform for developing metal-free, base-free, highly efficient, and reusable heterogeneous photocatalysts for organic transformations.     

Generalized moment-independent importance measures based on Minkowski distance

Importance measures have been widely studied and applied in reliability and safety engineering. This paper presents a general formulation of moment-independent importance measures and several commonly discussed importance measures are unified based on Minkowski distance (MD). Moment-independent importance measures can be categorized into three classes of MD importance measures, i.e. probability density function based MD importance measure, cumulative distribution function based MD importance measure and quantile based MD importance measure. Some properties of the proposed MD importance measures are investigated. Several new importance measures are also derived as special cases of the generalized MD importance measures and illustrated with some case studies.     

Analysis and pharmacokinetic study of polyphyllin H in beagle dog plasma after oral administration of Rhizoma Paridis extracts by LC‐MS/MS

A highly sensitive, rapid assay method has been developed and validated for the analysis of polyphyllin H in beagle dog plasma with liquid chromatography coupled to tandem mass spectrometry with electrospray ionization in the positive‐ion mode. The assay procedure involves extraction of polyphyllin H and ginsenoside Re (IS) from beagle dog plasma. Chromatographic separation was carried out on an Agilent Zorbax XDB‐C₁₈ (100 × 2.1 mm, 1.8μm) column by isocratic elution with acetonitrile and water (50:50, v/v) at a flow rate of 0.25 mL/min with a total run time of 2.5 min. The MS/MS ion transitions monitored were 870.46 → 869.6 for polyphyllin H and 947.12 → 969.60 for IS. Linear responses were obtained for polyphyllin H ranging from 1 to 50 ng/mL. The intra‐and inter‐day precisions (RSDs) were <1.77 and 3.39% and the extraction recovery ranged from 91.89 to 93.33% with RSD <2.68%. Stability studies showed that polyphyllin H was stable in the preparation and analytical process. The results indicated that the validated method was successfully used to determine the concentration–time profiles of polyphyllin H. Copyright © 2014 John Wiley & Sons, Ltd.     

Inversion of Trace Formulas for a Sturm-Liouville Operator

This paper revisits the classical problem “Can we hear the density of a string?”, which can be formulated as an inverse spectral problem for a Sturm-Liouville operator. Instead of inverting the map from density to spectral data directly, we propose a novel method to reconstruct the density based on inverting a sequence of trace formulas which bridge the density and its spectral data clearly in terms of a series of nonlinear integral equations. Numerical experiments are presented to verify the validity and effectiveness of the proposed numerical algorithm. The impact of different parameters involved in the algorithm is also discussed.     

Mixed Cu2Se Hexagonal Nanosheets@Co3Se4 Nanospheres for High-Performance Asymmetric Supercapacitors

Rational designing and constructing multiphase hybrid electrode materials is an effective method to compensate for the performance defects of the single component. Based on this strategy, Cu₂Se hexagonal nanosheets@Co₃Se₄ nanospheres mixed structures have been fabricated by a facile two-step hydrothermal method. Under the synergistic effect of the high ionic conductivity of Cu₂Se and the remarkable cycling stability of Co₃Se₄, Cu₂Se@Co₃Se₄ can exhibit outstanding electrochemical performance as a novel electrode material. The as-prepared Cu₂Se@Co₃Se₄ electrode displays high specific capacitance of 1005 F g⁻¹ at 1 A g⁻¹ with enhanced rate capability (56 % capacitance retention at 10 A g⁻¹), and ultralong lifespan (94.2 % after 10 000 cycles at 20 A g⁻¹). An asymmetric supercapacitor is assembled applying the Cu₂Se@Co₃Se₄ as anode and graphene as cathode, which delivers a wide work potential window of 1.6 V, high energy density (30.9 Wh kg⁻¹ at 0.74 kW kg⁻¹), high power density (21.0 Wh kg⁻¹ at 7.50 kW kg⁻¹), and excellent cycling stability (85.8 % after 10 000 cycles at 10 A g⁻¹).     

Biomass-based carbon beads with a tailored hierarchical structure and surface chemistry for efficient batch and column uptake of methylene blue

Research on Chemical Intermediates - There is interest in cultivating an economic and controllable method for preparing biomass-based adsorptive materials for efficient removal of dyes from water....     

Lift characteristics of two tandem airfoils in the globally unstable wake of a heated cylinder

Journal of Thermal Analysis and Calorimetry - In this numerical study, we use two-dimensional scale-adaptive simulations to investigate the lift characteristics of two tandem airfoils in the...     

Copper-Catalyzed Si-H Bond Insertion Polymerization for Synthesis of Optically Active Polyesters Containing Silicon

The synthesis and characterization of chiral polymers with diverse structure remain a long-term challenging research topic.Herein,a copper-catalyzed enantioselective insertion of carbene into Si-H bond was applied to polycondensation,giving a new type of optically active degradable polyesters containing Si-C bond in the main chain.The polymerization features mild condition,broad substrate scope,excellent yields and enantioselectivities.Chiral diols could be obtained via reduction of optically active polyesters.Thermogravimetric analysis indicated these chiral polyesters exhibit good thermal stability.