Entropy Bumps and another sufficient condition for the two-weight boundedness of sparse operators

In this short note, we give a very efficient proof of a recent result of Treil–Volberg and Lacey–Spencer giving sufficient conditions for the two-weight boundedness of a sparse operator. We also give a new sufficient condition for the two-weight boundedness of a sparse operator. We make critical use of a formula of Hytönen in [6].     

Novel 9,9′‐(1,3‐phenylene)bis‐9H‐carbazole‐containing copolymers as hole‐transporting and host materials for blue phosphorescent polymer light‐emitting diodes

Novel photo‐crosslinkable hole‐transport and host materials incorporated into multilayer blue phosphorescent polymer light‐emitting diodes (Ph‐PLEDs) were demonstrated in this study. The oxetane‐containing copolymers, which function as hole‐transport layers (HTL), could be cured by UV irradiation in the presence of a cationic photoinitiator. The composition of the two monomers was varied to yield three different hole‐transporting copolymers, [Poly(9,9′‐(5‐(((4‐(7‐(4‐(((3‐methyloxetan‐3‐yl)methoxy)methyl)phenyl)octan‐3‐yl)benzyl)oxy)methyl)?1,3‐phenylene)bis(9H‐carbazole)) ( P(mCP‐Ox)‐I , ‐II , and ‐III )]. In addition, monomer 1 was copolymerized with styrene to produce copolymer P(mCP‐Ph) as a host material for bis[2‐(4,6‐difluorophenyl)pyridinato‐C²,N](picolinato)iridium(III) (FIrpic), a blue‐emitting dopant. All mCP‐based copolymers displayed high glass transition temperatures (T_g) of up to 130–140 °C and triplet energies of up to 3.00 eV. The blue Ph‐PLEDs exhibited a maximum external quantum efficiency of 2.55%, in addition to a luminous efficiency of 8.75 cd A^?1 when using the device configuration of indium tin oxide/poly(3,4‐ethylenedioxythiophene):poly(styrene sulfonate)/ P(mCP‐OX)‐III / P(mCP‐Ph) :FIrpic(15 wt %)/3,3′‐[5′‐[3‐(3‐pyridinyl)phenyl][1,1′:3′,1′′‐terphenyl]‐3,3′′‐diyl]bispyridine/LiF/Al. The device bearing P(mCP‐Ox)‐III HTL, containing the highest composition of mCP unit, exhibited better performance than the other devices, which is attributed to induction of more balanced charge carriers and carrier recombination in the emissive layer. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 707–718     

Synthetic Studies on Erythrina Alkaloids: Formal Total Synthesis of (+)-3-Demethoxyerythratidinone

A formal asymmetric synthesis of (+)-3-demethoxyerythratidinone (1) is reported using the key intermediate 3 as the starting material, which is available from L-malic acid by a known method.

A photochemical investigation into operational degradation of arylamines in organic light-emitting diodes

In this study, we investigated the operational degradation of 4,4′-bis(N-carbazolyl)biphenyl (CBP), an arylamine commonly used as phosphorescent host or hole transport material in organic light-emitting diodes (OLEDs), which have been subject to a recent surge in demand for use in the optical display market. In view of the important roles of organic components in the stability and lifetime of OLEDs, we initiated an investigation of the operational degradation of CBP in OLEDs in an effort to elucidate the degradation mechanism. Our experimental approach to this task is by performing photochemistry on CBP in solution, thereby avoiding actual operation of CBP-based OLEDs. Prior to the experiments, we calculated the C–N homolytic bond dissociation energy in CBP, and synthesized two CBP derivatives based on molecular engineering considerations. Furthermore, we performed TiO₂ photocatalytic decomposition of arylamines as a feasibility test for another operational degradation pathway. Based on both the photochemical and photocatalytic experiments, multiple operational degradation pathways of arylamines emerge.     

Comparison of doping limits among sonochemically prepared metal-doped TiO2 nanopowders in view of physicochemical properties

According to binding energy calculations in a unit cell model of anatase TiO₂, the doping limits for Cr, V, W, Mo, Zr, and Nb are predicted to increase in this order. In our experimental test of doping limits, Cr and W are considered in this series of transition metals, since their low doping limits suggest greater difficulty of doping into anatase structure than the others, thereby providing a challenging test for the prediction. Besides, noble metals such as Ag and Pt are selected for doping into TiO₂ for comparison. Thus, our investigation includes twofold research activities. One is to prepare metal-doped TiO₂ nanopowders of four different kinds, and the other is to determine the doping limit of each resulting powder. For the former, a sonochemical process has been used to produce metal-doped TiO₂ nanoparticles. For the latter, we resorted to electron probe microanalysis. In addition, we performed analysis by X-ray diffraction, transmission electron microscopy, and diffuse reflectance spectroscopy, as well as photocatalytic reaction with methylene blue. Thus, the resulting physicochemical properties of our metal-doped nanoparticles are expected to provide a basis for comparison of doping limits among them.     

Analytical separation of amino acids on a cation-exchange resin cross-linked with m-divinylbenzene.

The elution bands of acidic and neutral amino acids of protein hydrolysates, emerging from the column of a cation-exchange resin cross-linked with pure m-divinylbenzene, are narrower than those from a resin prepared from styrene and technical divinylbenzene. As a result of these narrower bands, a more complete resolution of the critical pairs threonine-serine, glycine-alanine and tyrosine-phenylalanine is obtained. The most probable reason for the narrower elution peaks is the more rapid diffusion of the exchanged components through the bulk of the resin as a result of a more regular arrangement of cross-linkages in the cation-exchange resin prepared from m-divinylbenzene.