Netsu Sokutei
Online ISSN : 1884-1899
Print ISSN : 0386-2615
ISSN-L : 0386-2615
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Volume 39, Issue 4
Displaying 1-8 of 8 articles from this issue
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Review
  • Gelation Mechanism of Polysaccharide Gellan Gum in Aqueous Solutions
    Etsuyo Ogawa
    2012 Volume 39 Issue 4 Pages 121-129
    Published: October 25, 2012
    Released on J-STAGE: November 20, 2022
    DOIhttps://doi.org/10.11311/jscta.39.4_121
    JOURNAL FREE ACCESS
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    Polysaccharide gellan gum forms transparent, heat, and acid resistant gels. In the present paper, recent studies on gelation mechanism for gellan gum aqueous solution are reviewed. Using sodium, lithium, potassium, and tetramethyl-type gellan gums as samples, viscometry, osmometry, and differential scanning calorimetry, and light scattering and circular dichroism measurements were carried out in aqueous solutions with and without salts. On lowering temperature, gellan gums undergo a coil to double-helix conformational transition in aqueous solutions with and without salts and a sol to gel transition took place by aggregation of double-helical gellan gum molecules. Attention is especially paid to the effects of molar masses of gellan gum molecules on the coil to double-helix transition and the sol-gel transitions in aqueous solutions. Effects of cations on these transitions of gellan gums in aqueous solutions are also mentioned.
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  • Thermodynamic Properties of Silicate Melts
    Toru Sugawara
    2012 Volume 39 Issue 4 Pages 130-136
    Published: October 25, 2012
    Released on J-STAGE: November 20, 2022
    DOIhttps://doi.org/10.11311/jscta.39.4_130
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    Previously reported values and properties of enthalpy of fusion of silicate minerals, heat capacity, enthalpy of mixing and entropy of mixing of silicate melts are reviewed. The entropy of fusion of silicate minerals varies linearly with heat capacity of those melts, because both properties reflect configurational freedom of components in silicate melt. Based on the compilation of calorimetric enthalpy measured for melts of mixtures of mineral endmemer compositions, we found that enthalpy of mixing of multi-component silicate melt is controlled by interactions among network-forming oxides (SiO2, NaAlO2, KAlO2), network-modifying oxides (CaO, MgO) and intermediate oxide (CaAl2O4). Entropy of mixing of SiO2-Na2O melt is calculated by a combination of Na2O activity data and calorimetric enthalpy of mixing. The comparison with previous entropy models suggests that a quasi-chemical model and an Adam-Gibbs model overestimate the configurational entropy of mixing of SiO2-Na2O melt.
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  • Development of Reference Material for Specific Heat Capacity Measurements
    Haruka Abe
    2012 Volume 39 Issue 4 Pages 137-142
    Published: October 25, 2012
    Released on J-STAGE: November 20, 2022
    DOIhttps://doi.org/10.11311/jscta.39.4_137
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    In the National Metrology Institute of Japan (NMIJ), a certified reference material (CRM) for specific heat capacity measurements was produced in accordance with the NMIJ’s quality system which is in compliance with ISO GUIDE 34 and ISO/IEC 17025. A material for the CRM was a single-crystalline silicon. Certified values of specific heat capacity were determined based on the heat capacity obtained by a cryogenic adiabatic calorimeter using a pulse-tube refrigerator in the measurement temperature range from 50 K to 350 K. In this paper, the development of the specific heat capacity CRM is reported in detail.
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  • Evaluation of Biobased Content of Biobased Polymer by Measuring Carbon-14 Using Accelerator Mass Spectrometry
    Masahiro Funabashi, Masao Kunioka
    2012 Volume 39 Issue 4 Pages 143-150
    Published: October 25, 2012
    Released on J-STAGE: November 20, 2022
    DOIhttps://doi.org/10.11311/jscta.39.4_143
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    Evaluation of biobased content of biobased polymers and their composites by measuring carbon-14 using accelerator mass spectrometry (AMS) was described. Biobased carbon content can be evaluated by measuring carbon-14 content using AMS, since biomass includes carbon-14 atoms in atoms of its constitution and fossil include no carbon-14 atoms in it. Sample preparation and pretreatment for AMS were explained in detail. Results of biobased content of plants, polymers and polymer composites by AMS were shown. Reproducibility and accuracy of AMS measurement were investigated. Evaluation method for biobased polymer content of polymer products can be also obtained using results by AMS. Examples of these evaluation results were shown. The international standards concerning this method were also described.
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  • Thermal Characterization of Novel Polymers for Biomedical Applications
    Masaru Tanaka, Kazuhiro Sato
    2012 Volume 39 Issue 4 Pages 151-157
    Published: October 25, 2012
    Released on J-STAGE: November 20, 2022
    DOIhttps://doi.org/10.11311/jscta.39.4_151
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    A number of polymeric biomaterials have been proposed, such as hydrophilic, phase-separated, and zwitterionic polymers. Also, new generation polymer: poly(2-methoxyethyl acrylate) (PMEA) shows excellent biocompatibility, and has been approved for medical use. It has not been clearly elucidated which mechanisms are responsible for the biocompatibility on a molecular level, although many theoretical and experimental efforts have been devoted to understand this mechanism. Water interactions have been recognized as a fundamental part of the biological response to contact with biomaterials. We have proposed the “Intermediate water” concept; the water exhibited clearly defined peaks for cold crystallization in the DSC chart. We found that the localized hydration structure consisting of three hydrated water in poly(2-methoxyethyl acrylate) (PMEA). We hypothesized that Intermediate water, which prevents the proteins and blood cells from directly contacting the polymer surface or non-freezing water on the polymer surface, plays an important role in the excellent biocompatibility. Here, I will give an overview of the recent progress in the experimental description of mechanisms of biocompatibility driven by thermal analysis.
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  • Study of Structural Phase Transformations Using Convergent-Beam Electron Diffraction
    Kenji Tsuda
    2012 Volume 39 Issue 4 Pages 158-163
    Published: October 25, 2012
    Released on J-STAGE: November 20, 2022
    DOIhttps://doi.org/10.11311/jscta.39.4_158
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    The convergent-beam electron diffraction (CBED) technique and its applications to phase transformations are described. Point- and space-group determination, nanometer-scale crystal structure refinement and electrostatic potential analysis using CBED are presented along with examples of the low-temperature ferromagnetic insulator phase of La1-xSrxMnO3 (x = 0.12) and the orbital-ordered phase of FeCr2O4.
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Technical Note
  • Development of Measuring Apparatus for Reaction Rate of Contact Hydration of Cement
    Daiki Atarashi, Hiroshi Sato, Etsuo Sakai, Shingo Iida
    2012 Volume 39 Issue 4 Pages 164-166
    Published: 2012
    Released on J-STAGE: November 20, 2022
    DOIhttps://doi.org/10.11311/jscta.39.4_164
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      A new apparatus, an improved reaction calorimeter was designed and constructed to determine the reaction rate of contact hydration of cement in a short time. The calorimeter consists of twin cells with comb-like agitators in them: a sample cell, wherein hydration reaction takes place, filled with cement and water and a reference cell filled with a reference material. A thermocouple probe is attached at the center of each cell to detect the temperature difference between the cells. The differential output from the thermocouples acts as feedback signal to control the input to an electric heater in the reference cell to compensate the temperature difference between the cells.
      Input power to the heater in the reference cell agreed with the calibration heat supplied in the sample cell within 3%. The heat rate curve obtained for contact hydration of Portland cement coincided with that determined by the time differentiation of a reaction thermogram which was obtained using an isoperibol calorimeter and corrected by Newton’s law of cooling.
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