The shear property at the residual state is a very important strength in engineering, as usually used for landslide stability analysis. We examined the microscopic structure of the shear surface and spectroscopic property of adsorbed water. As a result of AFM measurement of shear surface it became clear that shear surface was not a perfect flat, and also by CLSM observation, we found that the contact part of a glass board and a shear surface of clay was only partial contact. It indicates that the area actually touched was smaller than the apparent contact area. The "actual contact area" increased as the normal stress increased. While with FTIR measurement, adsorbed water on shear surface of cohesive soil decreased as the increase in normal stress. In conclusion, the coefficient of residual state shear resistance (tanφ_r) of clay can be thought to be the coefficient originated in the increase in the actual contact area caused by the increase in the normal stress.

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Photosynthetic microbes play an important role in the formation of calcium carbonate minerals in the various earth's surface environments. To evaluate the effects of photosynthetic microbes on the precipitation rates and polymorphism, precipitation experiments were performed in systems with and without unicellular green alga Chlorella vulgaris. The experiments were conducted by the batch method using 100ml solutions containing 5.0mM CaCl_2, 20.0mM NaHCO_3, and 0.0, 1.0, 2.0, 3.0, 4.0, or 5.0mM MgCl_2 at 25℃ for 10 days. Three types of reaction systems were prepared: (1) abiotic system containing no C. vulgaris, (2) biotic system containing 10^6 cells/ml of C. vulgaris under light condition, and (3) biotic system containing 10^6 cells/ml of C. vulgaris under dark condition. Throughout the reaction period, solution pH, concentrations of Ca^<2+>, Mg^<2+>, and HCO_3^- ions, and dissolved polysaccharides and proteins released from C. vulgaris cells were measured daily. The results indicated that C. vulgaris enhanced precipitation rates by approximately 2.7-2.9 times under light condition as compared with those of the abiotic system, which was due to increase in solution pH mainly through the algal photosynthetic activity. In contrast, C. vulgaris slightly inhibited the precipitation rates under dark condition by the interactions of extracellular polysaccharides with the surface of CaCO_3 precipitates. In addition, C. vulgaris inhibited the formation of aragonite and favored calcite formation as the dominant polymorph despite the presence of Mg^<2+> ions. This may be attributed to the greater adsorption affinity of the polysaccharides for the surface of aragonite than for the calcite surface.

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Hybrid films consisting of synthetic saponite (Smecton SA, SSA from Kunimine Ind. Co. Ltd., Japan) and a cationic fluorene; 1,1'-diethyl-4,4'-(9,9-diethyl-2,7-fluorenediyl-2,1-ethenediy1)- dipyridinium perchlorate (FL) were fabricated. The two-photon absorption (TPA) properties of the FL-SSA hybrid films were characterized by the open-aperture Z-scan technique. The maximum TPA cross-section (σ^<(2)>_<peak>) of the FL in methanol was 810GM (1GM=1×10^<50>cm^4 s photon^<-1> molecule^<-1>). On the other hand, σ^<(2)>_<peak> of the FL in a clay film fabricated at an FL loading of 10% versus cation exchange capacity was 1400GM. This enhancement of σ^<(2)>_<peak> resulted from improved molecular orientation of the FL resulting from periodic stacking of the clay layers in the film.

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Clay-porphyrin complex formation and spectral behaviour of metalloporphyrins containing di-, tri- and tetravalent central metals with synthetic clay were examined. The spectral shift of porphyrin Soret band to higher wavelengths was observed upon the complex formation, where the clay sheets were either exfoliated or stacked in aqueous colloidal suspension. Moreover, the degree of the spectral shift decreased as the valence of porphyrin central metal increased. Since tri- and tetravalent metals have one and two axial ligands, respectively, their steric effect on porphyrin ring plane affected the extent of the "flattening" (i.e. co-planarization of porphyrin ring and peripheral aromatic rings) on the clay surface, thus influencing the spectral shift in porphyrin absorption spectra. These observations support the proposed hypothesis that "flattening" of porphyrin molecules on the clay surface induces the spectral shift of porphyrin Soret band. With this "flattening effect" of the clay surface, the λ_<max> value of Mg(II)TMPyP porphyrin reached up to 500nm in the stacked clay complex. These results indicate that the utilizing a combination of porphyrin with clay turned out to be unique to control the photochemical properties of porphyrins.

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On the occasion of the 1st Asian Clay Symposium in the 54th Clay Science Society Conference at Nagoya (2010), the activities of the Clay Science Society of Japan (CSSJ) for over 50 years were summarized in this review. Although the number of the CSSJ members was several hundreds and surprisingly stable from the foundation, the ratio of members of six research fields, i.e. (1) earth science, (2) resource, (3) ceramics, (4) chemistry, (5) soil and (6) civil showed a clear tendency to increase in the categories (3) and (4) while decrease in the categories (1) and (5), which means replacing of the members. This suggests that majority of the CSSJ member's interests on clays and clay minerals are shifting from understanding and characterizing of clay minerals to exploiting and using of clays as advanced materials with unique chemical and physical properties. Since such a tendency for research interest change in the CSSJ is preceding to the other clay societies in the world, we have to play more important role in leading of clay's study, especially for Asia area.

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Minerals are the major and characteristic constituents of many soil horizons and soils. Twelve essential nutrient elements are provided from the minerals although nitrogen is provided from soil organic matter including organisms. Four following topics about minerals in volcanic ash soils and paddy field soils were introduced and the perspectives on future research were discussed. (1) During andosolization, Al, Fe, Ti, Sc, rare earth elements, etc., are concentrated as nearly immobile elements in accordance with the removal of Si, Ca, Na, etc. (2) Apatite in volcanic ash is sparingly soluble around neutral pH, and acid or chelating organic acid exudation is effective for plants to uptake P from apatite. (3) Biotite in volcanic ash can be easily weathered to vermiculite releasing K^+ that is one of the major essential elements for plants. (4) Vivianite was found on rice roots grown in lowland soils.

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The yellowish〜reddish brown residual soils are widely distributed in S. Korea. The residual soils have been widely used for the various applications. In the present study, the mineral and chemical compositions and other properties of some representative residual soils were investigated and compared according to parent rock type. Various applications of residual soils in Korea and the basic ideas of each application were introduced. The mineral and major element compositions of residual soils were different according to parent rock type, but the difference in the residual soils isn't significant compared with the difference in the parent rocks. Residual soils contain varying amounts of clay minerals such as kaolinite, illite and micas/vermiculite. The color and density as well as mineral and chemical compositions vary with particle size. The color and density become more reddish and higher, respectively, with decreasing particle size because of increasing amount of iron oxide. The amounts of clay minerals are increasing with decreasing particle size. These results are coincident with the variations in chemical compositions. The unique applications of residual soils are a characteristic feature in Korea unlike in other countries. The reddish residual soils have been widely used for various applications such as red tide reduction, construction materials, animal feeding, cosmetics, food, natural pigment and various healthy products. The main reasons of application are to use the properties of clay minerals contained in residual soil.

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In the present study, the weathering process of minerals in ferralitic soils under terrace paddy was identified by comparison of their clay mineralogy with that of ferralitic soils under natural forest. The result showed that clay minerals detected in the soils were vermiculite-chlorite intergrade, kaolinite, gibbsite and goethite. However, the content of these minerals varied with soils depending on the physiographic differences. In the soils under the natural forest and subjected to the terrace paddy field condition only for short-time, ferralitization process is still remaining with decomposition of vermiculite-chlorite intergrade, an easily weatherable mineral. As a result, vermiculite-chlorite intergrade in the clay fraction was in a decreased content with the correspondingly increased content of kaolinite. In contrast, vermiculite-chlorite intergrade was detected with a larger amount in the soils subjected to the terrace paddy field condition for long-time, and its content sometimes exceeded the kaolinite content. Gibbsite was also observed with a larger amount in these soils. This suggests that ferralitization process has been retarded and might be replaced by alitization process under the terrace paddy field conditions.

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