Highly efficient green organic light-emitting diodes containing luminescent three-coordinate copper(I) complexes

A series of highly emissive three-coordinate copper(I) complexes, (dtpb)Cu(I)X [X = Cl (1), Br (2), I (3); dtpb =1,2-bis(o-ditolylphosphino)benzene], were synthesized and investigated in prototype organic light-emitting diodes (OLEDs). 1-3 showed excellent photoluminescent performance in both degassed dichloromethane solutions [quantum yield (Φ) = 0.43-0.60; lifetime (τ) = 4.9-6.5 μs] and amorphous films (Φ = 0.57-0.71; τ = 3.2-6.1 μs). Conventional OLEDs containing 2 in the emitting layer exhibited bright green luminescence with a current efficiency of 65.3 cd/A and a maximum external quantum efficiency of 21.3%.     

Relationship between space charge and effective pore size of nanoporous electrode in electric double-layer capacitor

The space-charge distributions of electric double-layer capacitors (EDLCs), which are energy storage devices, were examined with the pulsed electroacoustic (PEA) method. It was found that the experimental results could be influenced by the reflection and penetration of sound waves when the space-charge distributions of EDLCs were measured with the PEA method. This is because EDLCs have a five-layer structure consisting of three materials (aluminum, cellulose, and activated carbon). We calculated the reflect...     

Analysis of fusion-fission process with neutron evaporation in superheavy mass region

The fusion-fission process for the synthesis of superheavy elements is discussed on the basis of the fluctuation-dissipation dynamics. We analyze the experimental data using a three-dimensional Langevin calculation. We take the neutron emission into account in the Langevin calculation and compare the results with experimental data. Also we discuss the evaporation residue cross section for superheavy elements.     

Error estimates of finite element methods for nonstationary thermal convection problems with temperature-dependent coefficients

Summary. General error estimates are proved for a class of finite element schemes for nonstationary thermal convection problems with temperature-dependent coefficients. These variable coefficients turn the diffusion and the buoyancy terms to be nonlinear, which increases the nonlinearity of the problems. An argument based on the energy method leads to optimal error estimates for the velocity and the temperature without any stability conditions. Error estimates are also provided for schemes modified by approximate coefficients, which are used conveniently in practical computations.Mathematics Subject Classification (2000): 65M12, 65M60, 76M10     

Asymmetric and highly stereoselective synthesis of the DEF-ring moiety of (-)-FR182877 and its derivative inducing mitotic arrest

The asymmetric and highly stereoselective synthesis of compound 1, which corresponds exactly to the DEF-ring moiety of (-)-FR182877, and the biological activities of its derivatives are described. All derivatives of 1 showed no activity in the tubulin polymerization assay, but one derivative was shown to have the ability to induce mitotic arrest by interfering with microtubule dynamics, and the cellular effects are similar to those of paclitaxel.     

Experimental and computational creep characterization of Al–Mg solid-solution alloy through instrumented indentation

Carefully designed indentation creep experiments and detailed finite-element computations were carried out in order to establish a robust and systematic method to extract creep properties accurately during indentation creep tests. Samples made from an Al–5.3?mol%?Mg solid-solution alloy were tested at temperatures ranging from 573 to 773?K. Finite-element simulations confirmed that, for a power-law creep material, the indentation creep strain field is indeed self-similar in a constant-load indentation creep test, except during short transient periods at the initial loading stage and when there is a deformation mechanism change. Self-similar indentation creep leads to a constitutive equation from which the power-law creep exponent n, the activation energy Q _c for creep, the back or internal stress and so on can be evaluated robustly. The creep stress exponent n was found to change distinctively from 4.8 to 3.2 below a critical stress level, while this critical stress decreases rapidly with increasing temperature. The activation energy for creep in the stress range of n = 3.2 was evaluated to be 123?kJ?mol^?1, close to the activation energy for mutual diffusion of this alloy, 130?kJ?mol^?1. Experimental results suggest that, within the n = 3.2 regime, the creep is rate controlled by viscous glide of dislocations which drag solute atmosphere and the back or internal stress is proportional to the average applied stress. These results are in good agreement with those obtained from conventional uniaxial creep tests in the dislocation creep regime. It is thus confirmed that indentation creep tests of Al–5.3?mol%?Mg solid-solution alloy at temperatures ranging from 573 to 773?K can be effectively used to extract material parameters equivalent to those obtained from conventional uniaxial creep tests in the dislocation creep regime.     

Asymmetric catalysis on the intramolecular cyclopropanation of alpha-diazo-beta-keto sulfones

This work describes the development of a highly enantioselective asymmetric catalysis on the intramolecular cyclopropanation of alpha-diazo-beta-keto sulfones. We have found that the catalytic asymmetric intramolecular reactions of alpha-diazo-beta-keto sulfones generally proceed with high enantioselectivity when the alpha-diazo-beta-keto mesityl sulfone is used with the newly prepared ligand 2e. The absolute configuration of products has been determined by X-ray crystallographic analysis, and the outcome of the enantioselectivities is explained well by our proposed models A and B. The products possess great potential for natural product synthesis because (1) many different chemistries of cyclopropane, ketone, and sulfone are available, and (2) the products are generally highly crystalline, facilitating the supplies of enantiomerically pure synthetic intermediates.     

Chemical constituents of Avicennia alba. Isolation and structural elucidation of new naphthoquinones and their analogues

Three new naphthoquinones and their analogues, named avicequinone-A (1), -B (2), -C (3), and avicenol-A (4), -B (5), -C (6), respectively, were isolated from the stem bark of Avicennia alba (Avicenniaceae) collected in Singapore, and their structures were elucidated by means of spectral methods. Gillan and co-workers have proposed that the structures of the new phytoalexins isolated from Avicennia marina are 1,2-naphthoquinones 8 and 9. Our synthetic and spectrometric studies showed that these structures should be revised respectively to 1,4-naphthoquinones 2 and 3, named avicequinone-B and -C by us.     

Research on Au(I)-catalyzed ene-yne cycloisomerization for construction of quassinoid scaffold

Compounds that undergo Au(I)-catalyzed cycloisomerizations affording tetracyclic products that can be converted into compounds with the skeleton of bruceantin are described. The Au(I)-catalyzed cycloisomerizations reported herein are hindered by a 1,3-diaxial interaction between the substituent and the methyl group in the transition state. The use of small substituents was found to increase the yield of the desired product, while the reaction of substrates with large substituents afford undesired constitutional isomers.