The melt rheology of highly-purified ring polystyrenes in a wide range of molecular weights (10K ≤ M w ≤ 240K g/mol) was investigated. All the rings revealed no obvious rubbery plateau and faster terminal relaxation compared to the linear counterparts. The rheological data obtained were compared with some theoretical models such as the Rouse ring model and the lattice-animal model. Moreover, two rheological parameters, zero-shear viscosities η0 and the steady-state recoverable compliances J e, were estimated, and their M w dependence was discussed. From these data analysis, it was found that relaxation mechanisms of ring chains can be divided into three categories depending on their M w as follows: (i) Smaller rings (M w ≤ 20K) exhibit faster terminal relaxation than the predicted Rouse rings. This behavior is related to the difference of the local chain conformation from linear chains. (ii) Rings with the moderate molecular weight (40K ≤ M w ≤ 90K) exhibit dynamic moduli similar to the Rouse ring prediction. (iii) A larger ring (M w > 90K) also shows deviant behavior from the Rouse chain because its relaxation time is much longer than the Rouse ring prediction and also the lattice-animal model, where some intermolecular interactions are considered to occur.

Rhodium-diene complexes with the Tp iPr ligand, Tp iPr Rh(diene) (Tp iPr ) hydridotris(3,5-diisopropylpyrazolyl)borate; diene ) 1,5-cyclooctadiene (cod) (1), norbornadiene (nbd) (2)), are prepared by treatment of [Rh(µ-Cl)(diene)] 2 with KTp iPr or TlTp iPr . The structure of 1, characterized by X-ray crystallography, contains the κ 2 -coordinated Tp iPr ligand, and its central Rh atom adopts a square-planar geometry, whereas the unit cell of 2 contains two independent molecules: a square-planar structure with a κ 2 -coordinated Tp iPr ligand similar to 1 and a trigonal-bipyramidal one with a κ 3 -coordinated Tp iPr ligand. Although 1 H and 13 C NMR spectroscopy does not provide any information concerning the coordination geometry due to the interconversion between the square-planar and trigonal-bipyramidal structures, which occurs at a rate much faster than the NMR time scale, IR analysis reveals that the bands observed around 2470 and 2540 cm -1 are assigned to the B-H stretching vibrations of the square-planar and trigonal-bipyramidal structures, respectively. Thus, the ν(B-H) value can be used as an indicator of the hapticity of a Tp iPr ligand (κ 2 (∼2470 cm -1 ) vs κ 3 (>2530 cm -1 )) as compared with related Tp iPr ML n -type complexes.

Intravenous administration of a novel recombinant rhesus mAb against the α4β7 gut-homing integrin (mAb) into rhesus macaques just prior to and during acute SIV infection resulted in significant decrease in plasma and gastrointestinal (GI) tissue viral load and a marked reduction in GI tissue proviral DNA load as compared with control SIV-infected rhesus macaques. This mAb administration was associated with increases in peripheral blood naive and central memory CD4+ T cells and maintenance of a high frequency of CCR5+CD4+ T cells. Additionally, such mAb administration inhibited the mobilization of NK cells and plasmacytoid dendritic cells characteristically seen in the control animals during acute infection accompanied by the inhibition of the synthesis of MIP-3α by the gut tissues. These data in concert suggest that blocking of GI trafficking CD4+ T cells and inhibiting the mobilization of cell lineages of the innate immune system may be a powerful new tool to protect GI tissues and modulate acute lentiviral infection.

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A series of platinum-based sensitizers of the general type Pt(NN)(SS), where NN is 4,4'-dicarboxy-2,2'-bipyridine (dcbpy) or 4,7-dicarboxy-1,10-phenanthroline (dcphen) and SS is ethyl-2-cyano-3,3-dimercaptoacrylate (ecda), quinoxaline-2,3-dithiolate (qdt), 1,2-benzenedithiolate (bdt), or 3,4-toluenedithiolate (tdt), that have various ground-state oxidation potentials has been synthesized and anchored to nanocrystalline titanium dioxide electrodes for light-to-electricity conversion in regenerative photoelectrochemical cells with an I(-)/I(-)(3) acetonitrile electrolyte. The intense mixed-Pt/dithiolate-to-diimine charge-transfer absorption bands in this series could be tuned from 440 to 580 nm by choosing appropriate dithiolate ligands, and the highest occupied molecular orbitals varied by more than 500 mV. Spectrophotometric titration of the Pt(dcphen)(bdt) complex exhibits a ground-state pK(a) value of 3.2 +/- 0.1, which can be assigned to the protonation of the carboxylate group of the dcphen ligand. Binding of Pt(dcbpy)(qdt) to porous nanostructured TiO(2) films was analyzed using the Langmuir adsorption isotherm model, yielding an adsorption equilibrium constant of 4 x 10(5) M(-1). The amount of dye adsorbed at the surface of TiO(2) films was 9.5 x 10(-8) mol/cm(2), which is ca. 50% lower than the full monolayer coverage. The resulting complexes efficiently sensitized TiO(2) over a notably broad spectral range and showed an open-circuit potential of ca. 600 mV with an impressive fill factor of > 0.70, making them attractive candidates for solar energy conversion applications. The visible spectra of the 3,4-toluenedithiol-based sensitizers showed an enhanced red response, but the lower photocurrent efficiency observed for these sensitizers stems in part from a sluggish halide oxidation rate and a fast recombination of injected electrons with the oxidized dye.