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Origin of Ultrahigh Dielectric Constants for Barium Titanate Nanoparticles
Satoshi Wada,C Moriyoshi,H. Yasuno,K Kakemoto,K Takizawa,M Ohishi,T Hoshina,T Tsurumi,Y Kuroiwa 한국물리학회 2007 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.51 No.2I
Barium titanate (BaTiO3) nanoparticles with various particle sizes from 17 to 1,000 nm were prepared by using the 2-step thermal decomposition method of barium titanyl oxalate under various degree of vacuum. Various characterizations revealed that these particles were impurity-free, defectfree, dense BaTiO3 nanoparticles. When the degree of vacuum was high (pressure of 150 Pa at 650 C), the dielectric constant of BaTiO3 particles with a size of around 60 nm exhibited a maximum of around 15,000. On the other hand, when the degree of vacuum was low (pressure of 400 Pa at 650 C), no dielectric maximum was observed. To explain this size dependence, we precisely investigated a particle structure by using synchrotron radiation. As a result, the particles were always composed of two layers, i.e., a surface cubic layer and a bulk tetragonal layer, and the thickness of the surface cubic layer decreased with increasing degree of vacuum during the preparation of BaTiO3 nanoparticles. Thus, we confirmed that the surface structure was an important factor in determining the dielectric properties of BaTiO3 nanoparticles.
Satoshi Wada,H. Kakemoto,K Yokoh,T Tsurumi,T Muraishi 한국물리학회 2007 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.51 No.2I
The phase transition behaviors of [111]-oriented barium titanate (BaTiO3) crystals were investigated as functions of temperature, uniaxial stress, and electric field. For the phase transition caused by temperature, with decreasing temperature above Tc, the paraelectric phase changed to an intermediate phase with a superparaelectric state and finally changed to a ferroelectric phase with randomly oriented spontaneous polarizations. Moreover, the phase transition caused by the uniaxial stress field above Tc was found to be almost similar to the one caused by temperature. On the other hand, for the phase transition caused by an electric field above Tc, with increasing electric field, the paraelectric phase changed to an intermediate phase and finally to a ferroelectric phase with an oriented polar direction. These results suggest that above Tc, a combination of uniaxial stress with an electric field may be effective as a poling treatment for BaTiO3 crystals. Thus, in this study, a new poling method for the BaTiO3 crystals by using control of the temperature, the uniaxial stress, and the electric field is proposed.t
Kimura, Satoshi,Nakayama, Kei,Wada, Masahisa,Kim, Ung-Jin,Azumi, Kaoru,Ojima, Takao,Nozawa, Akino,Kitamura, Shin-Ichi,Hirose, Euichi Inter-Research 2015 Diseases of aquatic organisms Vol.116 No.2
<P>Soft tunic syndrome is a fatal disease in the edible ascidian Halocynthia roretzi, causing serious damage to ascidian aquaculture in Korea and Japan. In diseased individuals, the tunic, an integumentary extracellular matrix of ascidians, softens and eventually tears. This is an infectious disease caused by the kinetoplastid flagellate Azumiobodo hoyamushi. However, the mechanism of tunic softening remains unknown. Because cellulose fibrils are the main component of the tunic, we compared the contents and structures of cellulose in healthy and diseased tunics by means of biochemical quantification and X-ray diffractometry. Unexpectedly, the cellulose contents and structures of cellulose microfibrils were almost the same regardless of the presence or absence of the disease. Therefore, it is unlikely that thinning of the microfibrils occurred in the softened tunic, because digestion should have resulted in decreases in crystallinity index and crystallite size. Moreover, cellulase was not detected in pure cultures of A. hoyamushi in biochemical and expressed sequence tag analyses. These results indicate that cellulose degradation does not occur in the softened tunic.</P>
Yo Kubota,Satoshi Tanabe,Mizutomo Azuma,Kazue Horio,Yoshiki Fujiyama,Takafumi Soeno,Yasuaki Furue,Takuya Wada,Akinori Watanabe,Kenji Ishido,Chikatoshi Katada,Keishi Yamashita,Wasaburo Koizumi,Chika Ku 대한위암학회 2021 Journal of gastric cancer Vol.21 No.4
Purpose: Promoter DNA methylation of various genes has been associated with metachronous gastric cancer (MGC). The cancer-specific methylation gene, cysteine dioxygenase type 1 (CDO1), has been implicated in the occurrence of residual gastric cancer. We evaluated whether DNA methylation of CDO1 could be a predictive biomarker of MGC using specimens of MGC developing on scars after endoscopic submucosal dissection (ESD). Materials and Methods: CDO1 methylation values (TaqMeth values) were compared between 33 patients with early gastric cancer (EGC) with no confirmed metachronous lesions at >3 years after ESD (non-MGC: nMGC group) and 11 patients with MGC developing on scars after ESD (MGCSE groups: EGC at the first ESD [MGCSE-1 group], EGC at the second ESD for treating MGC developing on scars after ESD [MGCSE-2 group]). Each EGC specimen was measured at five locations (at tumor [T] and the 4-point tumor-adjacent noncancerous mucosa [TAM]). Results: In the nMGC group, the TaqMeth values for T were significantly higher than that for TAM (P=0.0006). In the MGCSE groups, TAM (MGCSE-1) exhibited significantly higher TaqMeth values than TAM (nMGC) (P<0.0001) and TAM (MGCSE-2) (P=0.0041), suggesting that TAM (MGCSE-1) exhibited CDO1 hypermethylation similar to T (P=0.3638). The area under the curve for discriminating the highest TaqMeth value of TAM (MGCSE-1) from that of TAM (nMGC) was 0.81, and using the cut-off value of 43.4, CDO1 hypermethylation effectively enriched the MGCSE groups (P<0.0001). Conclusions: CDO1 hypermethylation has been implicated in the occurrence of MGC, suggesting its potential as a promising MGC predictor.
Kim, Ung-Jin,Kimura, Satoshi,Wada, Masahisa Elsevier 2019 Carbohydrate Polymers Vol.214 No.-
<P><B>Abstract</B></P> <P>The adsorption of Congo red (CR) was evaluated using cellulose-chitosan foam crosslinked via dialdehyde cellulose (DAC). DAC-crosslinked cellulose-chitosan foam (CCLBD) was obtained by dissolution/regeneration using a LiBr aqueous solution, followed by crosslinking between chitosan and DAC. CCLBD possessed a three-dimensional structure with 40–200 nm wide pores composed of nanofibrils with a width of 10–20 nm, resulting in a high specific surface area of 230 m<SUP>2</SUP>/g. CCLBD was highly stable even acidic conditions in spite of a low crosslinking degree of 10.3%, which induced a slight reduction in the amino groups that interact with CR. CCLBD showed a CR adsorption capacity of 1548.2 mg/g and the adsorption process followed the Sips isotherm and pseudo-second-order models.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Crosslinked cellulose-chitosan foam (CCLBD) was prepared using a LiBr solution. </LI> <LI> CCLBD was stable in acidic regions in spite of a low degree of crosslinking. </LI> <LI> CCLBD exhibited an adsorption capacity (<I>qmax</I>) of 1548.2 mg/g for Congo red (CR). </LI> <LI> The <I>qmax</I> for CR was the highest value among the previously reported adsorbents. </LI> <LI> CCLBD is an effective adsorbent for the purification of dye-polluted water. </LI> </UL> </P>