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Volume 48 (2021)
- Issue 4 Pages 142-
- Issue 3 Pages 93-
- Issue 2 Pages 45-
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Volume 48, Issue 2
Displaying 1-8 of 8 articles from this issue
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JSCTA Research Encouragement Award 2020
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Hal Suzuki2021 Volume 48 Issue 2 Pages 45-51
Published: April 25, 2021
Released on J-STAGE: June 20, 2022
JOURNAL FREE ACCESSAccording to the third law of thermodynamics, the entropy of crystals tends to zero as T → 0. In many molecular crystals, the configurational entropy Sc is zero and the remaining vibrational entropy Sv decreases with decreasing temperature, which vanishes as T → 0. However, in some crystals, molecules can move around even in the crystalline states, where Sc remains non-zero. In this study, we focused on two types of such compounds, one with partially deuterated methyl groups and endohedral fullerenes, and have investigated how the Sc in those crystals approach to zero as T → 0. In the first system, the locations of H and D atoms in a partially deuterated methyl group are exchangeable even in the crystalline phase, which remains Sc = R ln 3. The Sc is released at around 10 K where Schottky type anomalies are observed in heat capacity. This is caused by the splitting of the triply degenerated ground states due to the symmetry breaking by the partial deuteration. In the second system, a Li+ ion circulates quantum mechanically in a C60 fullerene at 300 K, which localizes into two pockets below 100 K, and into one pocket below 24 K due to the Coulombic interactions with the neighboring ions. A H2O encapsulated in a C60, on the other hand, rotates quantum mechanically even at 1 K.View full abstractDownload PDF (575K) -
Satoshi Yamashita2021 Volume 48 Issue 2 Pages 52-58
Published: 2021
Released on J-STAGE: June 20, 2022
JOURNAL FREE ACCESSRecent molecular based compounds demonstrate various kinds of physical properties based on peculiar crystal, molecular and electronic structures. Sometimes these systems require specific measurements due to quite small sample amount, special treatment at extreme conditions or other difficulty. In our studies, we have developed novel heat capacity measurement systems and established novel technique to investigate dielectric and electrostrictive characters. In the thermodynamic studies on the spin liquid states of organic dimer-Mott insulating systems, we have found the close relation between the spin entropy represented by T-linear coefficient γ and the magnetic interaction in molecular based quantum spin liquid systems. In the study of novel type system of Non-Coulombic-Ionic Solid, we have found the remarkable value of the dielectric constant and high ion conductivity.View full abstractDownload PDF (814K)
Review
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Hiroyuki Yoshida2021 Volume 48 Issue 2 Pages 59-64
Published: April 25, 2021
Released on J-STAGE: June 20, 2022
JOURNAL FREE ACCESSIn this article, the magnetic and thermodynamic properties of strongly frustrated antiferromagnet are discussed. The macroscopic degeneracy caused by magnetic frustration plays a significant role on the formation of exotic ground state of frustrated antiferromagnet. Particularly, the emergence of a quantum spin liquid state has been expected on the ground state of quantum kagome antiferromagnet owing to the strong frustration and quantum fluctuation. Here, we present the unusual magnetic properties of Kapellasite type quantum kagome antiferromagnet CaCu3(OH)6Cl2·0.6H2O (Ca-Kapellasite). Magnetic properties of Kapellasite type kagome antiferromagnet depends on a balance of magnetic interactions among the nearest-neighbor J1, the next nearest-neighbor J2, and the further interaction Jd across the hexagon within the kagome network, and a formation of unusual magnetic state is expected including the spin liquid state. We observed the magnetic transition at 7.2 K and demonstrated that the low temperature heat capacity of Ca-Kapellasite was reproduced by assuming a two-dimensional spin-wave component and a T-linear term. The observed T-linear term of this insulating compound suggests the existence of an unusual quasi-particle excitation below the magnetic transition. This fact apparently reveal the unconventionality of the ground state of this S = 1/2 kagome antiferromagnet.View full abstractDownload PDF (1706K) -
Sadaki Samitsu2021 Volume 48 Issue 2 Pages 65-71
Published: April 25, 2021
Released on J-STAGE: June 20, 2022
JOURNAL FREE ACCESSNanoporous polymers have been industrially used in valuable products such as large-scale separator sheet of Liion batteries, hollow fiber membranes for medical usage, and high-performance membrane and adsorbent for gas and water purification. New development of fabrication methodology of nanoporous polymers is therefore a key challenge that will make it possible to launch new applications. Here we will describe our new fabrication methods of nanoporous polymers that rely on solid-liquid phase separation phenomena. One is flash-freezing nanocrystallization method that is driven by nanocrystallization of solvent molecules and the other is physical gel precursor methods utilizing crystallization of polymers. Deep understanding of phase separation and crystallization mechanism is a key on the fabrication methods. Using commercially-available polymers such as polystyrene and engineering plastics, these methods provide a membrane, a fiber, and a monolith of mesoporous polymers with nanopores (10–100 nm in diameter) and large specific surface areas (over 300 m2/g). The mesoporous polymers are useful as separation membranes and adsorbents for water purification and gas separation, thermal insulators, and optical materials.View full abstractDownload PDF (2299K) -
Eiji Ohmae2021 Volume 48 Issue 2 Pages 72-77
Published: April 25, 2021
Released on J-STAGE: June 20, 2022
JOURNAL FREE ACCESSUnfolding mechanism of proteins is an old and new problem. In this article, basic mechanism of protein unfolding are explained using the examples of pressure-induced unfolding, denaturant-induced unfolding, and thermal and cold unfolding. Although unfolding of small globular proteins follow two-states, native and unfolded states, it does not mean the existence of only two structures, since the states are determined by intermolecular interactions but the structures are determined by intramolecular ones. Pressure-induced unfolding clarifies important contribution of hydration to the unfolding mechanism of proteins, because pressure affects to total volume of the system. Denaturant-induced unfolding are explained by preferential interactions between protein and denaturant molecules, which mechanism can also explain effects of stabilizers such as salts or sugars although sign of the interactions are inverted. Negative entropy change due to cold unfolding indicates extensive restriction of hydrated water molecules exceed to the increase of protein’s conformational chain entropy due to unfolding. Contrary to instinctive images, thermodynamic parameters showed that the folding of several proteins at room temperature raise the randomness of protein solution in the case of cytochrome c, myoglobin, tryptophan synthase α subunit, and human serum albumin.View full abstractDownload PDF (734K) -
Haruyuki Atomi2021 Volume 48 Issue 2 Pages 78-84
Published: April 25, 2021
Released on J-STAGE: June 20, 2022
JOURNAL FREE ACCESSHyperthermophiles are organisms that display optimal growth temperatures of 80˚C or higher. They thrive in a variety of hydrothermal environments. Hyperthermophiles occupy the most early-branching lineages in the phylogenetic tree of life, and are a focus of attention in terms of the origin and evolution of life. Hyperthermophiles display diversity in their mechanisms to conserve energy. The biomolecules of hyperthermophiles must function at extremely high temperatures, and this is made possible by unique structural features and/or interactions. Nucleic acids are stabilized by enzymes such as reverse gyrase and interactions with thermostable DNA-binding proteins or compounds including branched-chain polyamines. Proteins display structural adaptations that enable them to maintain their functional conformation at high temperatures. Hyperthermophiles from the archaea display much higher growth temperatures compared to their bacterial counterparts, and utilize membrane lipids not found in bacteria or eukaryotes. Metabolic enzymes and pathways are also designed to avoid unnecessary thermal degradation of labile intermediates. This article will provide an overview of the fascinating world of hyperthermophiles and the strategies that allow them to thrive at temperatures that would be lethal to any other organism.View full abstractDownload PDF (686K)
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2021 Volume 48 Issue 2 Pages 85-88
Published: April 25, 2021
Released on J-STAGE: June 20, 2022
JOURNAL FREE ACCESSDownload PDF (411K)
Applied Research of Thermal Analysis
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Eita Shimoda, Yuichi Kasai, Nobuaki Okubo2021 Volume 48 Issue 2 Pages 89-90
Published: April 25, 2021
Released on J-STAGE: June 20, 2022
JOURNAL FREE ACCESSDownload PDF (429K)
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