The molecular models of tubular aluminumsilicate, imogolite, and tubular gibbsite for the comparison with imogolite were investigated by means of molecular dynamics simulations. The stability of these two models was tested in terms of the tube radii. It was shown that the total energy of tubular gibbsite is decreasing monotonically with the increasing radius of the tube. On the contrary, the total energy of imogolite has the minimum around diameter 2.6−2.9 nm. The details of the imogolite stability were inspected in terms of atom potential energy and the structural details.

The purposes of this study are to determine the molt cycle of the American crayfish, Procambarus clarkii, and to quantify the amounts of the molt-inhibiting hormone (Prc-MIH) in the hemolymph and neurohemal sinus glands during the molt cycle of the American crayfish. The molt cycle was classified into six stages based on the changes in volumes of gastroliths in the stomach and ecdysteroid titers in the hemolymph. A sandwich-type enzyme immunoassay using specific antibodies raised against N-terminal and C-terminal segments of Prc-MIH was developed for the Prc-MIH assay. It is sensitive to as little as 0.5 fmol of Prc-MIH (3.3 x10(-12) M). In the hemolymph, no Prc-MIH could be detected at any of the molt stages tested. However, in the sinus gland, it was demonstrated that the amount of Prc-MIH changes in a molt-stage-specific manner during the molt cycle. It was particularly noteworthy that the initiation of a molting sequence (i.e., entering the early premolt stage) corresponded to the increase in Prc-MIH content in the sinus gland, because the finding is consistent with the hypothesis that crustaceans enter the premolt stage when the MIH secretion from the sinus gland is reduced or ceases.

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In order to study the dynamics of the polymerization in liquid sulphur we have measured the transient absorption spectra after illuminating with a pulsed laser below and above the polymerization temperature, Tp. We have found that photoinduced polymerization occurs below Tp and there exist two kinds of relaxation process, that is, the fast and slow ones. The slow one can be observed after illumination with a very weak pulsed laser and the relaxation time is of the order of ten minutes. The fast one is observed just after stopping the illumination of a rather stronger pulsed laser and the relaxation time is about 30 seconds. The fast one is always followed by the slow one. On the basis of these findings we conclude that the fast relaxation process corresponds to the relaxation from a polymeric chain to a charge transfer complex and the slow one the relaxation from the charge transfer complex to the most stable ring molecule. With further increase of the intensity of the pulsed laser we have found that giant molecules with colloidal form are generated and they lie on parallel lines. The relaxation time is about one minute.

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SynopsisA graphical method is proposed for the analysis of experimental data on the equilibrium sorption of ions by charged polymers. The method uses dimensionless groups of variables, which are based on a generalized Donnan theory. Graphical comparisons of theoretical curves with experimental data-point sets permit rapid estimation of theoretical parameters. The use of dimensionless groups clarifies the complex interactions between the individual sorption variables.This simple procedure consists of relative lateral and vertical displacements of the data point graphs and the theoretical graphs along their coordinate axes. The graphical comparisons help to reveal the nature of departures from the basic theoretical model. Examples of the method are given for oxycellulose/methylene blue and polyacrylonitrile polymer/cationic dye systems.

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