Asymmetric reduction of aromatic ketimines in the presence of helical polymer as catalyst

Novel optically active ethynyl monomers were synthesized from L ‐valine and N‐methyl‐L ‐valine, and polymerized with a rhodium catalyst to provide the polymers with number‐average molecular weights over 200,000 in good yields. The CD and UV‐vis spectra of the polymers indicated that they took helical structures with predominantly one‐handed screw sense in solution. The polymers served as catalysts of asymmetric reduction of aromatic ketimines to afford optically active amines in moderate yields. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4971–4981, 2009     

Infrared Problem for the Nelson Model on Static Space-Times

We consider the Nelson model on some static space-times and investigate the problem of existence of a ground state. Nelson models with variable coefficients arise when one replaces in the usual Nelson model the flat Minkowski metric by a static metric, allowing also the boson mass to depend on position. We investigate the existence of a ground state of the Hamiltonian in the presence of the infrared problem, i.e. assuming that the boson mass m(x) tends to 0 at spatial infinity. We show that if m(x) ≥ C |x|⁻¹ at infinity for some C > 0 then the Nelson Hamiltonian has a ground state.     

Structure and Kinetics of Desolvation of 2-Hexanone Inclusion Compounds of the Hexapedal Hosts, Hexakis(3-hydroxy-3,3-diphenyl-2-propynyl)benzene and 1,2,3,5,6,7-Hexakis(3-hydroxy-3,3-diphenyl-2-propynyl)naphthalene

The 2-hexanone inclusion compounds of hexakis(3-hydroxy-3,3-diphenyl-2-propynyl)benzene and 1,2,3,5,6,7-hexakis(3-hydroxy-3,3-diphenyl-2-propynyl)naphthalene have been prepared and characterised by single crystal X-ray diffraction and thermal analysis. The kinetic parameters and mechanisms for the desolvation reaction have also been determined for both compounds.     

Synthesis of end‐functionalized poly(phenylacetylene)s with well‐characterized palladium catalysts

End‐functionalized poly(phenylacetylene)s were synthesized by the polymerization of phenylacetylene (PA) using the well‐defined palladium catalysts represented as [(dppf)PdBr(R)] {dppf = 1,1′‐bis(diphenylphosphino)ferrocene}. The Pd catalysts having a series of R groups such as o‐tolyl, mesityl, C(Ph)?CPh₂, C₆H₄‐o‐CH₂OH, C₆H₄‐p‐CN, and C₆H₄‐p‐NO₂ in conjunction with silver triflate polymerized PA to give end‐functionalized poly(PA)s bearing the corresponding R groups in high yields. The results of IR and NMR spectroscopies and MALDI‐TOF mass analyses proved the introduction of these R groups at one end of each polymer chain. The poly(PA) bearing a hydroxy end group was applied as a macroinitiator to the synthesis of a block copolymer composed of poly(PA) and poly(β‐propiolactone) moieties. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Ground state for point particles interacting through a massless scalar Bose field

We consider a massless scalar Bose field interacting with two particles, one of them infinitely heavy. Neither an infrared nor an ultraviolet cutoff is imposed. In case the charge of the particles is of the same sign and sufficiently small, we prove the existence of a ground state.     

Controlled ring-opening polymerization of cyclic carbonates and lactones by an activated monomer mechanism

This article reviews recent topics in the controlled synthesis of polycarbonates and polylactones with small polydispersity indices by activated monomer cationic ring-opening polymerizations, especially with new initiator systems, such as alcohol/protonic acid and boron alkoxide/protonic acid. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2190–2198, 2002     

Intergranular fracture surface analysis of molybdenum

Bend properties of plasma beam and/or electron beam melted molybdenum and several dilute alloys containing C, B, T, V and Re were investigated. Fracture surfaces and microstructure were examined in detail by SEM and AES. Considerable intergranular fracture occurred in almost all of the samples as the test temperature decreased. But proper alloy addition, such as B and Ti, and hot-rolling induced a change in the fracture mode to a transgranular mode. Segregation of nitrogen and/or oxygen to grain boundaries was often recognized in plasma beam or electron beam melted ingots and decreased the strength of grain boundaries. Small precipitates due to comparatively low alloy addition such as C, B, Ti and Re, were effective to enhance the grain boundary cohesion.     

Synthesis of plakevulin A and structure-activity relationships of its related compounds against DNA polymerases

Synthesis of plakevulin A and structure-activity relationships of its related compounds against DNA polymerases is described. We have achieved a total synthesis and revised the structure of plakevulin A. Several analogues including untenone A, manzamenone A, and optically active plakevulin A, were prepared and tested with an enzyme inhibition assay for mammalian DNA polymerases. The effect of the methyl ester moiety, and the substituents at the 1- and 4-positions of plakevulin A on DNA polymerase activities are discussed.     

Wave optical analysis of integral method for three-dimensional images

We analyze by wave optics an integral method that produces three-dimensional (3D) images. The point light source is given at the pickup stage, and the light wave passing through each elemental lens is obtained at the display stage. The amplitude distributions of the waves from each elemental image are the same around a specific point where a 3D image is formed. Since the light waves approaching the image plane from different elemental lenses are incoherent, the synthesized value is the sum of the squared amplitudes of the waves. Therefore the modulation transfer function of this integral method is given by that of a single elemental lens.     

Improving Data Quality in Traditional Low-Dose Scanning Transmission Electron Microscopy Imaging

It has become very important to study and find optimal conditions for imaging electron-beam (e-beam) sensitive materials in scanning transmission electron microscopy under low electron-dose with high signal-to-noise ratio (SNR). Convergence and collection angles and electron-probe current are essential parameters. However, these parameters have rarely been discussed in a systematic way. In this paper, the illumination and collection conditions are optimized according to the resolution requirement of different materials by adjusting the condenser and intermediate lenses in a commercial transmission electron microscope. To demonstrate the significance of optimizing these parameters, two examples, zeolite MFI and metal–organic framework (MOF) MIL-101, are taken among the sensitive materials, with the most important electron incidences along the [010] and <110> directions, respectively. High SNR atomic resolution images of MFI are obtained with e-beam current as low as 0.50 pA, reaching information transfer for reflection up to 18 0 2 corresponding to d-spacing of 0.11 nm, close to the resolution limit of 0.098 nm from resolvable diffraction limit. MOF MIL-101 is characterized under an even lower e-beam 0.2 pA to avoid severe beam damage. High-quality annular dark and bright field images are obtained, which proves the wide applicability of this method on more e-beam sensitive materials.