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      • KCI등재

        Comparison of thermal and elastic properties of glassy racemic and enantiomorphic ibuprofen studied by Brillouin light scattering and modulated differential scanning calorimetry

        김태현,Tomohiko Shibata,Seiji Kojima,신동명,황윤회,고재현 한국물리학회 2014 Current Applied Physics Vol.14 No.7

        The vitrification process of racemic RS- and enantiomorphic S-ibuprofen was studied by using Brillouin light scattering and modulated differential scanning calorimetry (DSC). The sound velocity and the attenuation coefficient of both compounds were determined for the first time in the glassy, supercooled liquid and liquid states. The sound velocity and the hypersonic damping were similar between the two ibuprofen pharmaceuticals over the whole investigated temperature range including glassy, supercooled liquid and liquid states. The thermal expansion coefficient of the RS-ibuprofen was smaller than that of the S-ibuprofen, which suggests that the intermolecular force of the former is slightly stronger than the latter. The thermal relaxation times derived from the modulated DSC were consistent with the dielectric relaxation times in both RS- and S-ibuprofens. The fragility index of S-ibuprofen just above the glass transition was determined to be 73, which was smaller compared to the value of RS-ibuprofen, 89. This difference in the fragility indicates that the decrease in the fragility of S-ibuprofen compared to the racemic one may improve its stability of the amorphous state below the glass transition temperature against crystallization.

      • Adaptive Compensation Method for the Temperature Dependence of RF Transformer Isolation

        Aoyama, Takanobu,Shibata, Yoshiki,Kanie, Tomohiko,Noro, Yuichi,Takeo, Takashi The Korean Institute of Electrical Engineers 2012 The Journal of International Council on Electrical Vol.2 No.4

        In this study, we propose an adaptive compensation method for the temperature dependence of RF transformer isolation and present results of preliminary experiments. First of all, we examine the isolation temperature dependence of an RF transformer designed as a splitter, by means of both an electromagnetic simulation technique and experiments, to show the significance of the present issue. Then, we discuss the nature of a transformer core so as to obtain the most desirable isolation characteristics against a temperature change. Finally, in order to adaptively compensate for the isolation variation due to temperature, we propose a bias current superimposed on the RF signal, where the current amplitude is adjusted according to temperature change, and demonstrate the results of preliminary experiments conducted at a fixed temperature, but with different bias currents, indicating the validity of the proposed method.

      • KCI등재

        Brillouin-scattering Study of Liquid-glass Transitions in Ternary Mixtures of Water, Trehalose, and an Ionic Liquid

        Haruki Takayama,Tomohiko Shibata,Takahiro Ishii,Seiji Kojima 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.62 No.7

        Ternary mixtures of water, sugar, and ionic liquid have been studied as new candidates for bioprotectants. To clarify the elastic properties and relaxation dynamics of the supercooled liquid and glassy states at low temperatures, the liquid-glass transitions were investigated by using a micro-Brillouin-scattering technique. The refractive index was measured accurately as a function of content and temperature to determine the sound velocity and the attenuation from Brillouin frequency shift and peak width. The relaxation times of structural relaxations related to liquidglass transitions were determined as functions of temperature. The Meyer-Neldel rule was found to hold for the activation energy and the prefactor of the Arrhenius law for the relaxation time.

      • KCI등재

        Relaxation dynamics and fragility during liquideglass transitions of poly(propylene glycol)s

        Shota Koda,Tomohiko Shibata,박인성,Seiji Kojima 한국물리학회 2015 Current Applied Physics Vol.15 No.7

        The acoustic and thermal properties of the liquideglass transitions of propylene glycol and its oligomers, poly (propylene glycol)s, were studied by temperature modulated DSC and Brillouin scattering. The fragility indices were determined from Angell plots using the observed modulation frequency dependence of the complex heat capacity. The variation in the glass transition temperatures is discussed on the basis of the free volume theory. The relaxation time of the structural relaxation obeys the VogeleFulcher law, and its high frequency end is in good agreement with the result of the dielectric measurement in the literature. The correlation between the observed thermal expansion coefficients and the glass transition temperature is discussed based on the free volume theory. The sound velocity and attenuation were accurately determined as a function of the temperature by Brillouin scattering by combination with the refractive index measurement. The relaxation dynamics were discussed by considering the relaxation from segmental motions. All of these physical properties were discussed based on the third-order anharmonicity and the Grüneisen parameter.

      • KCI등재

        Small Angle Neutron Scattering Study on the Structural Variation of Lysozyme in Bioprotectants

        Shota Koda,Haruki Takayama,Tomohiko Shibata,Tatsuya Mori,Seiji Kojima,In-Sung Park,Tae-Gyu Shin 한국물리학회 2015 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.66 No.9

        The thermal denaturation and subsequent structural variation of lysozyme in various bioprotectant candidate solutions such as trehalose and choline acetate have been investigated by using small angle neutron scattering and differential scanning calorimetry. The gyration radius shows little change with the addition of additives in a native state at room temperature. On heating the lysozyme solution, a remarkable increase in the gyration radius is observed at temperatures above the denaturation temperature without any bioprotectants. Such an increase is suppressed by the additives owing to the intermolecular interactions between the lysozyme molecules and the bioprotectants of trehalose and choline acetate. The fractal dimension of lysozyme varies slightly with the addition of the bioprotectant solutions, and shows a remarkable drop in the vicinity of the denaturation temperature for all the solutions.

      • SCOPUSKCI등재

        One-year clinical efficacy and safety of indigo naturalis for active ulcerative colitis: a real-world prospective study

        ( Yuichi Matsuno ),( Takehiro Torisu ),( Junji Umeno ),( Hiroki Shibata ),( Atsushi Hirano ),( Yuta Fuyuno ),( Yasuharu Okamoto ),( Shin Fujioka ),( Keisuke Kawasaki ),( Tomohiko Moriyama ),( Tomohiro 대한장연구학회 2022 Intestinal Research Vol.20 No.2

        Background/Aims: Recent studies suggested a favorable effect of indigo naturalis (IN) in inducing remission for refractory ulcerative colitis (UC), however, the maintenance effect of IN for patients with UC remains unknown. Therefore, we conducted a prospective uncontrolled open-label study to analyze the efficacy and safety of IN for patients with UC. Methods: Patients with moderate to severe active UC (clinical activity index [CAI] ≥8) took 2 g/day of IN for 52 weeks. CAI at weeks 0, 4, 8, and 52 and Mayo endoscopic subscore (MES) and Geboes score (GS) at weeks 0, 4, and 52 were assessed. Clinical remission (CAI ≤4), mucosal healing (MES ≤1), and histological healing (GS ≤1) rates at each assessment were evaluated. Overall adverse events (AEs) during study period were also evaluated. The impact of IN on mucosal microbial composition was assessed using 16S ribosomal RNA gene sequences. Results: Thirty-three patients were enrolled. The rates of clinical remission at weeks 4, 8, and 52 were 67%, 76%, and 73%, respectively. The rates of mucosal healing at weeks 4 and 52 were 48% and 70%, respectively. AEs occurred in 17 patients (51.5%) during follow-up. Four patients (12.1%) showed severe AEs, among whom 3 manifested acute colitis. No significant alteration in the mucosal microbial composition was observed with IN treatment. Conclusions: One-year treatment of moderate to severe UC with IN was effective. IN might be a promising therapeutic option for maintaining remission in UC, although the relatively high rate of AEs should be considered. (Intest Res 2022;20:260-268)

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