Online ISSN : 2423-8872
Print ISSN : 0029-0181
ISSN-L : 0029-0181
Volume 74, Issue 11
Displaying 1-19 of 19 articles from this issue
  • Masayuki Uesugi
    Article type: Interdisciplinary
    2019 Volume 74 Issue 11 Pages 752-758
    Published: November 05, 2019
    Released on J-STAGE: May 15, 2020

    The spacecraft Hayabusa has returned to the earth in 2010. The event was closed up and widely broadcast because the spacecraft succeeded in returning back tiny particles from the asteroid Itokawa. Preliminary examination team of Hayabusa returned samples investigated the small particles around a few tens μm, and found a lot of facts about the past evolution and future evolution of the small asteroid. Challenges on the analysis of the Hayabusa returned samples were to maximize the scientific gain from 40 tiny samples with a coordinated analytical flow with the sequences of various analytical methods. Mounting of the small precious samples on the holders is always problematic because the sample was damaged or even lost during such procedures. Moreover, accuracy of the analysis largely depends on such sample preparation procedure. In the analysis of the Hayabusa returned samples, the team applied the sequence which was used for the analysis of a previous sample return project, though they could not investigate the samples with atmosphere shielded environment, for all samples. The Hayabusa2 spacecraft, a next generation spacecraft for sample return missions, successfully touched down on the asteroid Ryugu, which will contain water and organic materials. Thus, it should be much difficult to analyze the samples than that of the Hayabusa returned samples because those water and organic materials are easily damaged and contaminated by terrestrial materials. In this paper, we report the processes of trial and error for the analysis of the Hayabusa returned samples, and preparation for the analysis of the Hayabusa2 returned samples based on the learning by the trial and error.

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Artificial Intelligence and Physics
  • Kenichiro Koga
    Article type: Reviews
    2019 Volume 74 Issue 11 Pages 765-773
    Published: November 05, 2019
    Released on J-STAGE: May 15, 2020

    Fundamental problems on the hydrophobic effect and the hydrophobic interaction are reviewed. It is remarked that the solvation thermodynamics characteristic of hydrophobic hydration is actually not so uncommon when the constant-volume solvation process is considered while it is indeed atypical in the constant-pressure process, and what makes water special as a solvent of hydrophobic species is the smallness of its thermal pressure coefficient. What we know so far about the hydrophobic interaction are also described. Recent theoretical studies demonstrate that the osmotic second virial coefficient of methane in water is positive at low temperatures, decreases monotonically with temperature, and is large and negative at high temperatures, thus urging caution in assuming the hydrophobic interaction to be always attractive. A mean-field approximation for the solvation free energy in liquid mixtures is reviewed, which gives simple physical pictures on microscopic mechanisms of the temperature, pressure, and salt concentration dependences of the solvation free energy and the hydrophobic interaction.

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