Rotational diffusion of tungstic acid colloids in microgravity as studied by aircraft experiments

 Rotational relaxation times (τ) of anisotropic tungstic acid colloids (3.24 μm in major axis) in aqueous suspension are measured in microgravity (0G), normal gravity (1G) and at 2G. The measurements at 0G and 2G are achieved by parabolic and circular flights, respectively. The limiting slopes of the relaxation curves in the plots of the transmitted light intensity against time are close to zero at 0G irrespective of the flow directions in the flow cell, whereas those at 1G and especially at 2G depend on the flow direction by the convection of the suspension and particle sedimentation. Experimental errors at the τ values at 0G are small compared with those at 1G and 2G, which is ascribed to the lack of movement of impurities in the suspension such as quite small air bubbles, which cannot be recognized with the naked eye, and the convection of the suspension in microgravity. More reliable rotational relaxation times are obtained in microgravity; however, the relaxation times themselves are quite insensitive to gravity. Theτ values observed are larger than those calculated from the particle size, which indicates the important contribution of the electrical double layers formed around the colloidal particles. Received: 22 February 2001 Accepted: 13 June 2001     

Ionic photodissociation of some polymers quenched with electron donor or acceptor in solution

Ionic photodissociation processes of vinyl polymers with pendant carbazolyl groups in solution have been studied by nonsecond laser photolysis. The ionic dissociation yield decreases in the order of monomer, oligomers, and polymers.     

Dissociation study of tellurium cluster ions, Te(n)(+) (n = 25-85) using secondary ion mass spectrometry

Dissociation pathways of tellurium clusters, Te(n)(+) (n = 25-85), were investigated by secondary ion mass spectrometry. Positively charged ions were generated from a tellurium sheet by bombardment with 10 keV xenon ion beam. Mass analyses of cluster ions were performed using a grand-scale sector mass spectrometer. In the first field-free region, Te(n)(+) (n = 25-80) had a large dissociation probability with five- and six-atom emission and Te(n)(+) (n = 50-85) had a slightly large dissociation probability with 10- and 11-atom emission. Five- and six-atom dissociation in the second field-free region could be also observed. These results were most likely due to the cluster emission processes for Te(n)(+), although sequential atom emission and cluster emission could not be distinguished by this type of experiments.     

Addition of chlorodisilanes to 1,3-butadienes in the presence of tetrakis(triphenylphosphine)palladium(0). A facile route to (Z)-1,4-bis(chlorosilyl)but-2-enes

In the presence of a catalytic amount of tetrakis(triphenylphosphine)palladium(0), chlorodisilanes of type Me_nSi₂Cl_6-n (n  0, 2, 3 and 4) add to 1,3-butadienes to give (Z)-1,4-bis(chlorosilyl)but-2-enes.     

Synthesis and metal binding properties of novel sulfur-containing functional oligomer

The synthesis and metal ion binding properties of a new class of functional oligomers are described. Oligo[1-(N-phenylthiocarbamoyl)aziridine] (DP ca. 8) and its analogs are prepared by ring-opening oligomerization of the corresponding aziridine monomers in good yields. These oligomers contain sulfur groups capable of binding “soft” metal ions, and the selective binding properties of the novel oligomer for Cu(II) and Hg(II) ions are investigated by liquid-solid adsorption and liquid-liquid extraction experiments.     

Studies on antiinflammatory agents. I. Synthesis and pharmacological properties of 2'-phenoxymethanesulfonanilide derivatives.

Various 2'-phenoxymethanesulfonanilide derivatives were synthesized and evaluated for antiinflammatory and analgesic activities. Some compounds bearing an electron-attracting substituent at the 4'-position strongly inhibited adjuvant-induced arthritis in rats and acetic acid-induced writhing syndrome in mice without causing gastro-intestinal irritation. Among them, 4'-cyano-(FK867) and 4'-acetyl-(FK3311) 2'-(2,4-difluorophenoxy)methanesulfonanilides were selected as the candidates for further development.     

Structural Effects of Oligosaccharide-Branched Cyclodextrins on the Dual Recognition toward Lectin and Drug

Bi-galactose-branched cyclodextrins (Bi-Gal-CDs)(1–6) having different spacer arm lengths between two terminal galactoses were foundto have the optimum length for association with PNA lectin. Also, the inclusioninteraction of the drug depended on the length of the spacer arms. The dual association of thesecompounds was quantitatively evaluated by SPR and compared to the other oligosaccharide-branchedCDs (Scheme 1). The number and the length of the spacer arm are important for theassociation both with the lectin and drug for the purpose of targeting drug-delivery systems.The association constants K of bi-Gal-CD (2) with rat liver cells showed a 60 timeshigher association than with PNA. Direct evidence of the association between PNA andbi-Gal-CD (2) was characterized by AFM observations. The results obtained strongly suggested a method to find a new design for the targeting drug carrier. In order toincrease the association with the cell, a sufficient spacer arm length is necessary for the effectivedual recognition of the oligosaccharide-CDs. In order to increase the inclusion of thedrug, the CD structure of a multi-saccharide branch is necessary.