Abstract--The hydrated form of tubular halloysite [halloysite (10/~)] was observed by a conventional electron microscope equipped with an environmental cell (E.C.), by which the "natural" form was revealed without dehydration of the interlayer water. This study mainly reports the selected area electron diffraction (SAED) analysis of the halloysite (10 .~) and its morphological changes by dehydration. The SAED pattern showed halloysite (10/~) has two-layer periodicity in a monoclinic structure with the unit cell parameters ofa = 5.14 A, b = 8.90 .~, c = 20.7 A,/3 = 99.7", in space group Cc, and almost the same structure as the dehydrated form of halloysite [halloysite (7/~)]. This means that the dehydration of the interlayer water did not greatly change or affect the structure of halloysite (1~) ]~). Accompanying the ltehydration of the interlayer water, there appeared along the halloysite tube axis clear stripes that were about 50-100 A in width. The diameters of the tubular particles also increased about 10%. From the results of various experiments, such as a focussing series, observation of the surface structure by the replica method, observation of end-views of the tubular particles, and others, these two phenomena were explained as follows: Halloysite crystals have "domains" along the c-axis direction, the thicknesses of the "domains" vary ca. 50-100 A. They are tightly connected with each other when the halloysite is hydrated, but are separated from each other by the dehydration of the interlayer water, whereupon the stripes come into existence along the tube axis. Taking these considerations into account, a model of dehydration is proposed. Moreover, a new method of calculating the/3-angle is proposed in the Appendix.

synopsisPolyimide precursors were synthesized from a diamine and a diacid chloride that was derived from the reactant with promellitic dianhydride and 0-nitrobenzyl alcohol. Their thermal properties were studied in nitrogen using dynamic thermogravimetry, and the photoreaction mechanism was investigated by ultraviolet and infrared spectrophotometry. The polyimide precursors were spin-coated onto silicon wafers, prebaked, and then exposed to W light from a high pressure Hg-Xe lamp. When the f i l m s were dipped into 2% aqueous KOH after irradiation, the expased area dissolved forming high resolution Patterns. Relative sensitivities of the polymers were determined.

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The isotope effects of gadolinium in Gd-EDTA ligand exchange system were studied by means of ion exchange chromatography. The separation coefficients of gadolinium isotopes, epsilon, and the local enrichment factors, beta, were calculated from the observed isotopic ratios at the front and rear boundaries of the gadolinium adsorption band. Clear mass independent anomalies were observed in the isotope effects of 155Gd and 157Gd. The relation between the isotope effects of gadolinium isotopes, studied by the three-isotope plot and the separation coefficient methods, and the mass of gadolinium isotopes was found to be related to the change in the mean square radius of the nuclear charge distribution parameter, (r2), of these isotopes, which suggests that the nucleus shape and size highly affect the gadolinium isotope effects in chemical exchange reactions.

Intensity distributions of Fresnel fringes are calculated from a consideration of various specimen edge cross sections, where the penetration power and the phase shift of the electron beam are continuously varied with distance from the specimen edge.The variation of the calculated distributions shows a good accordance with the experiments in the following features: (i) the intensity distributions of overfocused and underfocused Fresnel fringes show a remarkable difference from each other in the region of relatively small defocusing value; (ii) the distribution is varied with the defocusing value and the specimen tilting angle, and the variation can be explained by the effective change of specimen edge form.