Polymerization of liposomes composed of diene-containing lipids by radical initiators. II. Polymerization of monodiene-type lipids as liposomes

1-Palmitoyl-2(2,4-octadecadienoyl)-sn-glycero-3-phosphocholine (POPC), a polymerizable lipid that contains one diene group in only a 2-acyl chain, was polymerized as liposome in an aqueous medium. Polymerization was initiated by water-insoluble azobisisobutyronitrile (AIBN), or water-soluble azobis(2-amidinopropane) dihydrochloride (AAPD). AIBN was mixed with monomeric lipids, and the mixture was dispersed in an aqueous medium by sonication to prepare AIBN-containing monomeric lipid liposomes. On the other hand, AAPD was simply added to the liposome suspension. The POPC liposomes were easily polymerized by the addition of AAPD, a water-soluble radical initiator, but few were polymerized by AIBN. The results suggested that the diene group in the 2-acyl chain was in an aqueous phase and, therefore, easily polymerized by a water-soluble radical initiator. The polymerized POPC liposomes were revealed to be more stable than those of monomeric ones because the scattered-light intensity from the polymerized POPC liposome suspension changed a little by the addition of Triton X-100. For only the polymerized ones, the liposome structure was confirmed by TEM after addition of an excess amount of Triton X-100.     

Stereocontrolled synthesis of beta-difluoromethylated materials

Investigation of synthetic routes for regio- and stereocontrolled fluorinated materials with a difluoromethyl group, using ethyl bromodifluoroacetate as a starting material, is described. In particular, (E)-difluoromethylated trisubstituted olefins were prepared via the proton migration reaction catalyzed by using fluoride anion. Further, optically active beta-difluoromethyl esters were obtained by the enzymatic resolution.     

A fast synthesis for Zintl phase compounds of Na3SbTe3, NaSbTe2 and K3SbTe3 by microwave irradiation

The microwave irradiation technique was used to prepare three Zintl phase compounds Na₃SbTe₃, NaSbTe₂ and K₃SbTe₃. The as-prepared products were analyzed and characterized by XRD, EDX and SEM techniques. Higher microwave oven power and shorter irradiation time are required for the synthesis of Na₃SbTe₃, whereas lower oven power and longer irradiation time are needed for NaSbTe₂. Moderate microwave irradiation conditions facilitate the formation of pure K₃SbTe₃. Pure phase of Na₃SbTe₃ are directly obtained by this technique for the first time. Compared with the traditional high-temperature solid-state synthesis, the microwave reaction required a considerable shortened reaction time for the preparation of the three Zintl compounds. The initial driving force for these reactions originates from the interaction of microwave electric field with alkali metals (Na and K) and Sb powders.     

Electron correlation effects on magnetic properties of BH

The nuclear magnetic shielding and magnetizability tensors for the BH molecule are calculated by the coupled-Hartree–Fock method and many-body perturbation theory. As in the case of H₂, HF, and F₂, the second-order non-CHF diagrams make an inappreciable contribution.     

Imaging of an Absorbing Object Embedded in a Dense Scattering Medium by Diffusing Light Topography

A new and simple imaging method for an absorbing object embedded in a dense scattering medium is proposed. The distinct characteristic is the positive usage of the diffusing light in the dense scattering medium to image the absorbing object. The principle is based on the equivalence between a probability distribution function of the path-length and a backscattered intensity distribution integrated spatially in the boundary plane between the medium and the air. The usefulness of the proposed method is experimentally confirmed for a modified pyramidal object painted black and thin tubes filled with black and red inks. The conditions under which the better image can be reconstructed are confirmed from the results of experiments and simulations. It is finally shown that our proposed method is capable of imaging the map of blood vessels distributed under the skin layers.     

Effects of Contrast and Character Size upon Legibility of Japanese Text Stimuli Presented on Visual Display Terminal

We examined effects of contrast and character size upon legibility of Japanese text stimuli presented on visual display terminal (VDT). In the experiment, three different character sizes were employed and the text stimulus was presented under a variety of conditions where contrast between the text and the background changed. Reading speed and the rate of readable characters were measured. Subjective rating for legibility was also evaluated. Results showed that legibility increases with luminance contrast for all character sizes examined here. A strong correlation was found between the subjective rating index and reading speed.     

Fourier phase microscopy for investigation of biological structures and dynamics

By use of the Fourier decomposition of a low-coherence optical image field into two spatial components that can be controllably shifted in phase with respect to each other, a new high-transverse-resolution quantitative-phase microscope has been developed. The technique transforms a typical optical microscope into a quantitative-phase microscope, with high accuracy and a path-length sensitivity of lambda/5500, which is stable over several hours. The results obtained on epithelial and red blood cells demonstrate the potential of this instrument for quantitative investigation of the structure and dynamics associated with biological systems without sample preparation.     

Functional polymers. 6. Unusual catalysis of polymeric cinchona alkaloids in asymmetric reaction

Acrylonitrile-cinchona alkaloid copolymers catalyzed the asymmetric addition of benzyl mercaptan to 2-nitrostyrene to give always (+)-enantiomer in excess, indicating the participation of C(3)-chirality in the enantioface differentiating step.