谷 篤史 | ![]() |
タニ アツシ | |
大学院人間発達環境学研究科 人間環境学専攻 | |
准教授 | |
物理学関係 |
研究論文(学術雑誌)
Semi-clathrate hydrates are attractive heat storage materials because the equilibrium temperatures, located above 0 °C in most cases, can be changed by selecting guest cations and anions. The equilibrium temperatures are influenced by the size and hydrophilicity of guest ions, hydration number, crystal structure, and so on. This indicates that intermolecular and/or interionic interaction in the semi-clathrate hydrates may be related to the variation of the equilibrium temperatures. Therefore, intermolecular and/or interionic interaction in semi-clathrate hydrates with quaternary onium salts was directly observed using low-frequency Raman spectroscopy, a type of terahertz spectroscopy. The results show that Raman peak positions were mostly correlated with the equilibrium temperatures: in the semi-clathrate hydrates with higher equilibrium temperatures, Raman peaks around 65 cm-1 appeared at a higher wavenumber and the other Raman peaks at around 200 cm-1 appeared at a lower wavenumber. Low-frequency Raman observation is a valuable tool with which to study the equilibrium temperatures in semi-clathrate hydrates.
2022年07月25日, Molecules (Basel, Switzerland), 27 (15)研究論文(学術雑誌)
研究論文(学術雑誌)
Periodontal disease develops as a result of oral microbiota in dysbiosis, followed by the growth of periodontal pathogens such as
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研究論文(学術雑誌)
Semiclathrate hydrate (SCH) is one of the phase change materials suitable for cold energy storage. Thermodynamic properties of SCHs, such as an equilibrium temperature and the dissociation enthalpy, depend on the size and shape of the guest substances. In the present study, to reveal the effects of steric conformations of the guest anions on the thermodynamic properties of SCHs, tetra-n-butylphosphonium dicarboxylate (TBP-DC) SCHs, where the anion was oxalate (TBP-Oxa), malonate (TBP-Mal), succinate (TBP-Suc), glutarate (TBP-Glu), maleate (TBP-Male), or fumarate (TBP-Fum), were investigated. TBP-Oxa, -Mal, -Suc, and -Fum SCHs had similar equilibrium temperatures, whereas the equilibrium temperatures of TBP-Glu and -Male SCHs were higher. This suggests that the size and conformation of glutarate and maleate anions are appropriate for the cage structures of SCHs. Moreover, we compared the equilibrium temperatures of TBP-Suc, -Male, and -Fum SCHs because TBP-Suc, -Male, and -Fum have similar anion structures. The equilibrium temperature of TBP-Suc SCH was similar to that of TBP-Fum SCH, whereas TBP-Male SCH showed a higher equilibrium temperature. This result implies that the succinate anion is accommodated in the trans conformation, similar to the fumarate anion, in the hydrate cages.
American Chemical Society (ACS), 2022年01月13日, Journal of Chemical & Engineering Data, 67 (1), 67 - 73, 英語[査読有り]
研究論文(学術雑誌)
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研究論文(学術雑誌)
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研究論文(学術雑誌)
Tetrabutylammonium/phosphonium bromide (TBAB/TBPB) hydrates, ionic clathrate hydrates were investigated by low frequency Raman scattering including in Terahertz (THz) region. The peak position and full-width-half-maximum (FWHM) of each hydrate were compared in the region below 3 THz (100 cm-1) . The position of the peak considered to be the translational movement of the anion was about 65 cm-1 in TBAB, which was clearly higher than TBPB. This is considered to be due to difference of contribution to center cation in atomic charge distribution. In addition, FWHM is may be due to the crystal structure and reflects the interaction between the anion and the water molecule. Direct observation of intermolecular interactions using spectroscopy in the terahertz region can be used to assess the influence of guest molecule differences on material characteristics.
一般社団法人 日本エネルギー学会, 2019年07月31日, 日本エネルギー学会大会講演要旨集, 28, 58 - 59, 日本語[査読有り]
研究論文(学術雑誌)
2017 年度より神戸大学は、兵庫県立大学、関西学院大学、甲南大学と ROOT と名付けたグローバルサイエンスキャンパス事業に取り組んでいる。そのプログラムでは強い知的好奇心と探究心を備えた高校生に根源的な問を喚起するユニットをはじめとする「科学力養成プログラム」と科学英語を学ばせる「国際性導入プログラム」を基礎ステージで高校生に提供し、その中から選抜された高校生に実践ステージで大学教員が研究指導を行い、ワ
シントン大学でポスター発表させる。2017 年度 ROOT プログラムに参加した 45 名の高校生を対象にインタビュー、ルーブリック評価、レジリエンス尺度、質問紙調査を用いて到達度、満足度などを調べた。その結果、基礎ステージで大半の受講生が満足できる水準に到達していること、実践ステージで 3 つのカテゴリーで有意な上昇をしていることが確かめられた
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研究論文(大学,研究機関等紀要)
氷衛星・氷惑星から噴出するプルームには、H2やCO2、CH4等の微量ガスが含まれる事が明らかにされてきたことから、微生物による生命活動の可能性が注目されている。しかし、岩石での地質化学的な微量ガスの生成の寄与が不明瞭であることから、微量ガスを検知するだけでは、微生物による生命活動を断定しきれない。この現状を踏まえ、本研究は、氷衛星・氷惑星の環境を模した室内実験から、主にCH4の同位体分別の素過程を評価し、生物起源のガスの寄与の定量的な推定を行うことを目的とする。本研究では、氷地殻–内部海に存在し、プルーム放出までの過程に影響を及ぼすクラスレートハイドレートに着目する。実験では、エンケラドス、および、エウロパの条件における同位体分別を調べる。実験に際し、50 MPa まで圧力を保持できるバッジ式特殊環境ハイドレート生成装置の開発を行った。本発表では、装置、および、測定法の詳細についての議論を中心に行う。
一般社団法人日本地球化学会, 2019年, 日本地球化学会年会要旨集, 66, 163, 日本語Phase equilibrium (temperature-composition) relations of tetra-n-butylphosphonium formate (TBP-For), acetate (TBP-Ace), and lactate (TBP-Lac) semiclathrate hydrate systems have been measured. The highest equilibrium temperatures of TBP-For, TBP-Ace, and TBP-Lac semiclathrate hydrates were 280.9, 284.6, and 283.8 K at the atmospheric pressure, respectively, where the composition of tetra-n-butylphosphonium carboxylate was approximately 0.035 ± 0.001 (mole fraction) in every system. The dissociation enthalpies of tetra-n-butylphosphonium carboxylate semiclathrate hydrates were measured by differential scanning calorimetry. The dissociation enthalpies of TBP-For, TBP-Ace, and TBP-Lac semiclathrate hydrates were (187 ± 3), (193 ± 3), and (177 ± 3) J·g-1, respectively.
2018年08月, Journal of Chemical Engineering Data, 63 (9), 3615 - 3620, 英語[査読有り]
研究論文(学術雑誌)
Microbial life inhabiting subseafloor sediments plays an important role in Earth's carbon cycle. However, the impact of geodynamic processes on the distributions and carbon-cycling activities of subseafloor life remains poorly constrained. We explore a submarine mud volcano of the Nankai accretionary complex by drilling down to 200 m below the summit. Stable isotopic compositions of water and carbon compounds, including clumped methane isotopologues, suggest that ~90% of methane is microbially produced at 16° to 30°C and 300 to 900 m below seafloor, corresponding to the basin bottom, where fluids in the accretionary prism are supplied via megasplay faults. Radiotracer experiments showed that relatively small microbial populations in deep mud volcano sediments (102 to 103 cells cm-3) include highly active hydrogenotrophic methanogens and acetogens. Our findings indicate that subduction-associated fluid migration has stimulated microbial activity in the mud reservoir and that mud volcanoes may contribute more substantially to the methane budget than previously estimated.
2018年06月, Science advances, 4 (6), eaao4631, 英語, 国際誌[査読有り]
研究論文(学術雑誌)
研究論文(国際会議プロシーディングス)
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研究論文(学術雑誌)
Although it is known that ammonium ion is replaced with a part of water cages of clathrate hydrate, it isn't known how much amount of ammonium ions are included into clathrate hydrate with the formation. We investigated how much amount of ammonium ions were included into clathrate hydrate with its formation. Tetrahydrofuran (THF) hydrate, as an analogue for CH4 and CO2 hydrate, was formed in a solution of THF with ammonium chloride. The concentration of ammonium ion in THF hydrate (CS) was determined and compared with the initial concentration of ammonium ion (C0). The ratio of CS to C0 (K=CS/C0) was determined when the volume ratio of formed solid to liquid was less than 0.9. The K value was 0.28 approximately when C0 wasn't more than 10 mmol/L. This value was about three times more than that value when ice was formed in an ammonium ion solution.
一般社団法人 日本エネルギー学会, 2017年, 日本エネルギー学会大会講演要旨集, 26, 54 - 55, 日本語Plasma-treated water (PTW), i.e. distilled water (DW) exposed to low-temperature atmospheric pressure helium plasma, exhibited strong bactericidal activity against Escherichia coli in suspension even within a few minutes of preparation. This effect was enhanced under acidic conditions. The bactericidal activity of PTW was attenuated according to first-order kinetics and the half-life was highly temperature dependent. The electron spin resonance (ESR) signal of an adduct of the superoxide anion radical (O-2(-center dot)) was detected in an aqueous solution using a spin-trapping reagent mixed with PTW, and adding superoxide dismutase to the PTW resulted in a loss of the bactericidal activity and weakening of the ESR adduct signal of O-2(-center dot) in the spin-trapping. These results suggest that O-2(-center dot) plays an important role in imparting bactericidal activity to PTW. Moreover, molecular nitrogen was required both in the ambient gas and in the DW used to prepare the PTW. We, therefore, suggest that the reactive molecule in PTW with bactericidal effects is not a free reactive oxygen species but nitrogen atom(s)containing molecules that release O-2(-center dot), such as peroxynitrous acid (ONOOH) or peroxynitric acid (O2NOOH). Considering the activation energy for degradation of these species, we conclude that peroxynitric acid stored in PTW induces the bactericidal effect.
IOP PUBLISHING LTD, 2016年10月, JOURNAL OF PHYSICS D-APPLIED PHYSICS, 49 (42), 425401, 英語[査読有り]
研究論文(学術雑誌)
The biological flux and lifetime of methanol in anoxic marine sediments are largely unknown. We herein reported, for the first time, quantitative methanol removal rates in subsurface sediments. Anaerobic incubation experiments with radiotracers showed high rates of microbial methanol consumption. Notably, methanol oxidation to CO2 surpassed methanol assimilation and methanogenesis from CO2/H-2 and methanol. Nevertheless, a significant decrease in methanol was not observed after the incubation, and this was attributed to the microbial production of methanol in parallel with its consumption. These results suggest that microbial reactions play an important role in the sources and sinks of methanol in subseafloor sediments.
JAPANESE SOC MICROBIAL ECOLOGY, DEPT BIORESOURCE SCIENCE, 2016年06月, MICROBES AND ENVIRONMENTS, 31 (2), 190 - 193, 英語[査読有り]
研究論文(学術雑誌)
Ion-exchange chromatographic analysis of peroxynitric acid (O2NOOH) was performed by combining an acidic eluate with an UV-vis detector and immersing the separation column in an ice-water bath. The decomposition behavior of peroxynitric acid in the solution was also studied using this system. The fraction for the peroxynitric acid peak was collected. Ion-exchange chromatographic analysis of this fraction, after standing at room temperature for 24h, showed that the decomposition products were mainly nitrate ions with a very small amount of nitrous acid. The peroxynitric acid peak area correlated perfectly with the total amount of decomposition products. The ion-exchange chromatographic isolation allowed us to evaluate the molar extinction coefficient of peroxynitric acid precisely in a wider wavelength range than previous reports. The value decreases monotonically from 1729 +/- 26 M-1 cm(-1) at 200 nm to 12.0 +/- 0.5 M-1 cm(-1) at 290 nm. (C) 2015 Elsevier B.V. All rights reserved.
Elsevier {BV}, 2016年01月, Journal of Chromatography A, 1431, 89 - 93, 英語[査読有り]
研究論文(学術雑誌)
We investigated fatty acid oxidation by atmospheric-pressure nonthermal helium plasma using linoleic acid, an unsaturated fatty acid, together with evaluating active species induced in liquids. If the ambient gas contains oxygen, direct plasma such as plasma jets coming into contact with the liquid surface supplies various active species, such as singlet oxygen, ozone, and superoxide anion radicals, to the liquid. The direct plasma easily oxidizes linoleic acid, indicating that fatty acid oxidation will occur in the direct plasma. In contrast, afterglow flow, where the plasma is terminated in a glass tube and does not touch the surface of the liquid sample, supplies mainly superoxide anion radicals. The fact that there was no clear observation of linoleic acid oxidation using the afterglow reveals that it may not affect lipids, even in an atmosphere containing oxygen. The afterglow flow can potentially be used for the sterilization of aqueous solutions using the reduced pH method, in medical and dental applications, because it provides bactericidal activity in the aqueous solution despite containing a smaller amount of active species.
IOP PUBLISHING LTD, 2015年10月, JOURNAL OF PHYSICS D-APPLIED PHYSICS, 48 (42), 424010, 英語[査読有り]
研究論文(学術雑誌)
Equivalent dose (D-e) estimations in electron spin resonance (ESR) dating have mostly been done by the multiple aliquot additive dose (MAAD) method despite disadvantages. In this study, we used X-ray irradiations and applied the single aliquot regenerative dose (SAR) technique to ESR De measurements of a volcanic quartz with independent age control. As the SAR protocol involves multiple steps of irradiations and readouts during a short period of time using a single aliquot, the thermal stabilities of the Al and Ti centres from natural and X-ray irradiated aliquots were compared by a pulse annealing test. The thermal stability of natural and regenerated ESR signals is significantly different for both Al and Ti centres and preheats are therefore considered necessary after artificial irradiations. The X-ray dose rate for quartz was calibrated using the same sample which was heated and irradiated with a known gamma dose. The SAR D-e values using the natural sample were obtained by means of a preheat plateau test. To check and correct for possible sensitivity change induced by the annealing used to reset the natural ESR signals, the single aliquot regeneration and added dose (SARA) method was applied. The SARA D-e values for the Al and Ti centres were in agreement, however, this D-e value overestimated the expected D-e from the independent age control, possibly because our sample was too old for the SARA method. (C) 2015 Elsevier Ltd. All rights reserved.
PERGAMON-ELSEVIER SCIENCE LTD, 2015年10月, RADIATION MEASUREMENTS, 81, 9 - 15, 英語[査読有り]
研究論文(学術雑誌)
Polycyclic aromatic hydrocarbons (PAHs) and chlorinated PAHs (C1PAHs) are ubiquitous contaminants that bind to the aryl hydrocarbon receptor (AhR) and exhibit mutagenic potential. It is difficult to monitor human exposure levels to C1PAHs because the exposure routes are complicated, and environmental concentrations are not always correlated with the levels of PAHs. Urinary PAR metabolites are useful biomarkers for evaluating PAR exposure, and C1PAH metabolites may therefore contribute to the estimation of C1PAH exposure. One of the most abundant C1PAHs present in the environment is 1-chloropyrene (CIPyr), and urinary CIPyr metabolites have the potential to be good biomarkers to evaluate the level of exposure to C1PAHs. Since the metabolic pathways involving C1PAHs are still undetermined, we investigated the effect of human cytochrome P450 enzymes on CIPyr and identified three oxidative metabolites by liquid chromatography tandem mass spectrometry and nuclear magnetic resonance. We found that CIPyr was metabolized most efficiently by the P450 1A1 enzyme, followed by the 1B1 and 1A2 enzymes. Similar to CIPyr, these metabolites were shown to have agonist activity for the human AhR. We detected these metabolites when ClPyr reacted with a pooled human liver S9 fraction as well as in human urine samples. These results suggest that the metabolites may be used as biomarkers to evaluate the extent of exposure to C1PAHs.
AMER CHEMICAL SOC, 2015年09月, CHEMICAL RESEARCH IN TOXICOLOGY, 28 (9), 1728 - 1736, 英語[査読有り]
研究論文(学術雑誌)
To confirm the formation of the superoxide anion radical (O-2(-)center dot) in liquids by atmospheric-pressure plasma, we investigated plasma-induced radical species in water using the electron spin resonance (ESR) spin-trapping technique combined with two proteins: superoxide dismutase (SOD), which has enzymatic activity to quench the superoxide anion radical, and bovine serum albumin (BSA), which does not have this enzymatic activity. Different setups of contact and non-contact atmospheric-pressure helium plasma were tested with an additional supply of oxygen gas. For each setup of plasma, no superoxide anion adduct ESR signal was observed in the aqueous solution with SOD, whereas the ESR signal appears in the samples with BSA and without any additive proteins. This means that a superoxide anion radical in the solution is sufficiently quenched by SOD before the formation of the spin adduct. The superoxide anion radical is actually induced in an aqueous solution by atmospheric-pressure plasma when ambient gases contain oxygen. (C) 2015 The Japan Society of Applied Physics
IOP PUBLISHING LTD, 2015年01月, JAPANESE JOURNAL OF APPLIED PHYSICS, 54 (1), 01AF01, 英語[査読有り]
研究論文(学術雑誌)
Recent progress in observations of radiation-induced radicals in gas hydrates was reviewed. Two different types of intermolecular hydrogen transfer reactions were observed. One is hydrogen-picking reaction where alkyl radicals withdraw hydrogen of alkane guest molecules in the adjacent cages of alkane hydrates. The other is hydrogen-hopping reaction where carboxyl (HOCO) radicals transfer excess hydrogen to CO2 molecules in the adjacent cages of CO2 hydrate. In the CO2 + methane mixed gas hydrates, the yield of radiation-induced radicals increases by reducing the inverse reactions of radical formation. The variety of intermolecular reactions in gas hydrates will attract us not only in physical chemistry but also in application area using new reaction field.
Japan Society of High Pressure Science and Technology, 2014年12月25日, Review of High Pressure Science and Technology/Koatsuryoku No Kagaku To Gijutsu, 24 (4), 258 - 264, 日本語[査読有り]
研究論文(学術雑誌)
The formation mechanisms of gamma-ray-induced carboxyl (HOCO) and methyl radicals in CO2 + methane mixed gas hydrates, which are inclusion compounds of H2O, CO2, and methane, were investigated. The HOCO and methyl radicals were observed in CO2 + methane mixed gas hydrates by electron spin resonance (ESR) at 120 K after irradiation at 77 K. The amounts of the HOCO and methyl radicals induced in the mixed hydrates are much higher than those in pure CO2 and methane hydrates. Both radicals are synergistically formed in the mixed hydrates by efficient reactions between the guest molecules (CO2 and methane) and the active species (electron, proton, and hydroxyl radical) induced from H2O.
AMER CHEMICAL SOC, 2014年11月, JOURNAL OF PHYSICAL CHEMISTRY B, 118 (47), 13435 - 13439, 英語[査読有り]
研究論文(学術雑誌)
Clathrate hydrates preserve active species more stably than the other icy materials and investigation of the behavior of the active species elucidates the physicochemical properties of clathrate hydrates like guestguest interaction. Color of the tert-butylamine clathrate hydrate changes to blue after gamma irradiation and is bleachable with visible light. The electron spin resonance (ESR) spectrum at 120 K mainly consists of a triplet signal of the C-centered radical NH2C(CH3)(2)CH2 center dot together with a single signal at g = 2.0008. The latter signal disappears after light exposure. These results indicate that both the blue color and the single ESR signal are derived from trapped electrons in the hydrate. They thermally decay around 140160 K by the first-order reaction, and the activation energy is 27 kJ/mol. Since tert-butylamine molecules can capture protons due to the high proton affinity, electrons may remain in the hydrate without reacting with protons, making the hydrate blue after gamma irradiation. The long-lived trapped electrons in the tert-butylamine hydrate have an advantage to investigate those in icy materials because tert-butylamine hydrate is nonionic and has a tetra-coordinated host water network like crystalline ice without any substitution for water molecules.
AMER CHEMICAL SOC, 2014年11月, JOURNAL OF PHYSICAL CHEMISTRY B, 118 (47), 13409 - 13413, 英語[査読有り]
研究論文(学術雑誌)
The carboxyl (HOCO) radical, which is an important species in atmospheric chemistry and combustion, is an intermediate in the reaction: CO + OH -> CO2 + H and serves as a hydrogen donor to the reaction partners. The cis-HOCO radical, one of the ground-state HOCO radicals, is supposed to be decomposed into CO2 and the hydrogen atom by a tunneling effect. In order to prove the hypothesis, we performed electron spin resonance (ESR) measurements to investigate the decay mechanisms of the ground-state HOCO and DOCO radicals in gamma-ray-irradiated CO2 hydrates, which may hold the radicals stably. The ground-state HOCO and DOCO radicals decayed according to a second-order decay model and transformed into formic acid and CO2. The ratio of the decay rate constants of HOCO and DOCO radicals shows a good agreement with that in the kinetic isotope effect for the hydrogen and deuterium abstraction reactions. These results indicate that they react with another HOCO radical in the adjacent hydrate cage without the tunneling effect. This implies that the ground-state HOCO radicals are not decomposed by the tunneling effect but are decayed through reactions with some atoms, molecules, and/or radicals even in the gas phase. In addition, the hydrogen-atom hopping through the temporary hydrogen bonds between the HOCO radical and CO2 results in a seeming diffusion of the HOCO radicals in the CO2 hydrate; this would be an important concept for the studies of the radical diffusions and the supply of hydrogen atoms in gas, liquid, and solid phases.
ROYAL SOC CHEMISTRY, 2014年, Physical Chemistry Chemical Physics, 16 (8), 3792 - 3797, 英語[査読有り]
研究論文(学術雑誌)
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To investigate the molecular interaction between guest species inside of the small and large cages of methane + propane mixed gas hydrates, thermal stabilities of the methyl radical (possibly induced in small cages) and the normal propyl and isopropyl radicals (induced in large cages) were investigated by means of electron spin resonance measurements. The increase of the total amount of the normal propyl and isopropyl radicals reveals that the methyl radical in the small cage withdraws one hydrogen atom from the propane molecule enclathrated in the adjacent large cage of the structure-H hydrate. A guest species in a hydrate cage has the ability to interact closely with the other one in the adjacent cages. The clathrate hydrate may be utilized as a possible nanoscale reaction field.
AMER CHEMICAL SOC, 2012年, Journal of Physical Chemistry A, 116 (10), 2405 - 2408, 英語[査読有り]
研究論文(学術雑誌)
The molecular orientation and dynamics of the organic stable radicals such as 2,2,6,6-tetramethyl-1-piperidinyl-1-oxyl (TEMPO) or 4-hydroxy-TEMPO (TEMPOL) included in the one-dimensional (1-D) organic nanochannels of 2,4,6-tris-4-(chlorophenoxy)-1,3,5-triazine (CLPOT) were investigated by examining the inclusion compounds (ICs) diluted by the co-inclusion of non-radicals using ESR spectroscopy. Spectral simulation showed that the axial rotation of TEMPO or TEMPOL molecules is excited in the nanochannels with activation energies of 8 and 7?kJ?mol-1, respectively. The rotation axis was estimated to be tilted towards the principal x direction in the axis system of the g-tensor of the respective radicals. This is quite different from that for similar ICs in the nanochannels of tris(o-phenylenedioxy)cyclotriphosphazene (TPP), in which the radicals are axially rotating around the principal axis y of the g-tensor. The difference is attributed to the larger nanospace of the CLPOT nanochannels. Copyright (C) 2012 John Wiley & Sons, Ltd.
WILEY-BLACKWELL, 2012年, Magnetic Resonance in Chemistry, 50 (3), 221 - 228, 英語[査読有り]
研究論文(学術雑誌)
Electron spin resonance (ESR) spectra of butyl radicals induced with gamma-ray irradiation in the simple isobutane (2-methylpropane) hydrate (prepared with deuterated water) were investigated. Isothermal annealing results of the gamma-ray-irradiated isobutane hydrate reveal that the isobutyl radical in a large cage withdraws a hydrogen atom from the isobutane molecule through shared hexagonal-faces of adjacent large cages. During this "hydrogen picking" process, the isobutyl radical is apparently transformed into a tert-butyl radical, while the sum of isobutyl and tert-butyl radicals remains constant. The apparent transformation from isobutyl to tert-butyl radicals is an irreversible first-order reaction and the activation energy was estimated to be 35 +/- 3 kJ/mol, which was in agreement with the activation energy (39 +/- 5 kJ/mol) of hydrogen picking in the gamma-ray-irradiated propane hydrate with deuterated water.
MDPI AG, 2012年, Energies, 5 (6), 1705 - 1712, 英語[査読有り]
研究論文(学術雑誌)
To understand plasma-induced chemical processing in liquids, we investigated the formation of free radicals in aqueous solution exposed to different types of non-contact atmospheric-pressure helium plasma using the spin-trapping technique. Both hydroxyl radical (OH center dot) and superoxide anion radical (O-2(-)center dot) adducts were observed when neutral oxygen gas was additionally supplied to the plasma. In particular, O-2(-)center dot can be dominantly induced in the solution via oxygen flow into the afterglow gas of helium plasma. This type of plasma treatment can potentially be used in medical applications to control infectious diseases, because the O-2(-)center dot is crucial for sterilization of liquids via atmospheric-pressure plasma. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4729889]
AMER INST PHYSICS, 2012年, Applied Physics Letters, 100 (25), 254103, 英語[査読有り]
研究論文(学術雑誌)
Radiation-induced free radicals in hydrated magnesium sulfate, which are thought to be present on the surface of Europa, one of the Jovian moons, have been studied by electron spin resonance (ESR). ESR signals of both atomic hydrogen (H center dot) at g = 2.0023 and sulfite radical (SO3-center dot) at g = 2.0029 are observed in epsomite (MgSO4 center dot 7H(2)O) and in quenched samples of magnesium sulfate solutions, after gamma-ray irradiation at 77 K. Atomic hydrogen disappears at temperatures above 90 K. The sulfite radical starts to decay above 190 K in the quenched sample of 10% magnesium sulfate solution, whereas in epsomite, it is stable even at 260 K. The sulfite radical accumulates at low ambient temperatures, and is a promising candidate for estimating the age of hydrated magnesium sulfate, especially in extraterrestrial environments. (C) 2012 Elsevier Ltd. All rights reserved.
PERGAMON-ELSEVIER SCIENCE LTD, 2012年, Radiation Measurements, 47 (9), 890 - 893, 英語[査読有り]
研究論文(学術雑誌)
To confirm the hydrate-like structures in tetra-n-butyl ammonium bromide (hereafter, TBAB) aqueous solution with tetragonal TBAB hydrates, the TBAB hydrate crystal and its stoichiometric aqueous solution at equilibrium state and during dissociation process have been investigated by means of in-situ Raman micro-spectroscopic observation. At equilibrium state and during dissociation process, the conformations of TBAB changed drastically around the surface between hydrate and aqueous phase, and the hydrate-like conformations did not appear in aqueous phase near the crystal. On the other hand, a broad signal in aqueous phase gradually changed during hydrate dissociation and then it converged after about 45 minutes. This implies the existence of residual that exhibits relatively slow structural relaxation in aqueous phase.
Hokkaido University Press, 2011年04月, Physics and Chemistry of Ice 2010, 2010, 141 - 146, 英語[査読有り]
研究論文(学術雑誌)
Methyl radical in gamma-irradiated methane hydrate with heavy water (D2O) has been investigated by electron spin resonance (ESR) using the sample tube designed for in-situ high-pressure measurements. Methyl radical, hydrogen atom, and deuterium atom were observed at 77 K. Hydroxyl radical (OH) was not detected and it is concordant with the previous results on gamma-irradiated methane hydrate with H2O. Although small signals of both hydrogen and deuterium atoms were found at 120 K, only methyl radicals remained at 210 K. The decay of the methyl radical was relatively slow under the pressurization with methane. The decay mechanism of the methyl radical partially depends on thermodynamic stability of methane hydrate.
Hokkaido University Press, 2011年04月, Physics and Chemistry of Ice 2010, 2010, 273 - 276, 英語[査読有り]
研究論文(学術雑誌)
It has been established that East Asian summer monsoon intensity varies with Dansgaard-Oeschger cycles, suggesting a connection between the climates of East Asia and the North Atlantic on a millennial timescale. However, the dynamics of such a connection are still unsolved. Here we demonstrate that temporal changes in the provenance of aeolian dust in Japan Sea sediments, which we interpret to reflect changes in the westerly jet path over East Asia, exhibit variations in harmony with Dansgaard-Oeschger cycles. The dominance of dust with a Mongolian Gobi provenance during stadials suggests a westerly jet axis located to the south of the Himalaya-Tibetan Plateau throughout most of the year, whereas the co-dominance of dust from both the Taklimakan Desert and the Mongolian Gobi during interstadials suggests that the westerly jet axis jumped to the north of the Tibetan Plateau at latest in summer. As the shift of the westerly jet axis to the north of the Tibetan Plateau is closely related to the onset of the East Asian summer monsoon, changes of the westerly jet path apparently critically affect the teleconnection between the climates of Asia and North Atlantic on a millennial timescale. (C) 2010 Elsevier Ltd. All rights reserved,
PERGAMON-ELSEVIER SCIENCE LTD, 2011年, Journal of Asian Earth Sciences, 40 (6), 1214 - 1220, 英語[査読有り]
研究論文(学術雑誌)
We demonstrated the first range-resolved detection and identification of CO2 dissolved in water by Raman lidar. A frequency doubled Q-switched neodymium-doped yttrium aluminum garnet (Nd:YAG) laser (532 nm) is used as the lidar light source, and the Raman signals at similar to 1273 and similar to 1380 cm(-1) from CO2 dissolved in water were detected. In lidar application, CO2 dissolved in water was identified in glass bottles 20 m away by using the CO2 Raman band at similar to 1380 cm(-1). (C) 2011 The Japan Society of Applied Physics
JAPAN SOC APPLIED PHYSICS, 2011年, Applied Physics Express, 4 (11), 112401, 英語[査読有り]
研究論文(学術雑誌)
[査読有り]
研究論文(学術雑誌)
Here we present proof-of-principle investigations on a novel inlet system for proton-transfer-reaction mass spectrometry (PTR-MS) that allows for the analysis of trace compounds dissolved in water. The PTR-MS technique offers many advantages, such as real-time analysis, online quantification, no need for sample preparation, very low detection limits, etc.; however it requires gas phase samples and therefore liquid samples cannot be investigated directly. Attempts to measure trace compounds in water that have been made so far are mainly headspace analysis above the water surface and membrane inlet setups, which both are well suitable for certain applications, but also suffer from significant disadvantages. The direct aqueous injection(DAI) technique which we will discuss here turns out to be an ideal solution for the analysis of liquid samples with PTR-MS. We show that we can detect trace compounds in water over several orders of magnitude down to a concentration level of about 100 pptw, while only consuming about 100 mu l of the sample. The response time of the setup is about 20s and can therefore definitely be called "online". Moreover the method is applicable to the analysis of all substances and not limited by the permeability of a membrane. (C) 2009 Elsevier B.V. All rights reserved.
ELSEVIER SCIENCE BV, 2010年, International Journal of Mass Spectrometry, 289 (2-3), 173 - 176, 英語[査読有り]
研究論文(学術雑誌)
A new inclusion compound (IC) using di-t-buthyl nitroxide (DBNO) radical and tris(o-phenylenedioxy)cyclotriphosphazene (TPP) (1), which has an organic one-dimensional (1-D) nanochannel in the crystal, is reported. According to the characterization using thermogravimetric analysis (TG), ESR measurements, etc., the composition of the inclusion compound was assigned as TPP:DBNO = 1:0.62. The narrowing of the isotropic ESR adsorption line of 1 was observed with a temperature increase from 103 K to room temperature. The line shape indicated a type of 1-D spin diffusion as observed in our previous study of the IC using TPP and 2,2,6,6-tetramethyl-1-piperidinyloxyl (TEMPO).
MDPI AG, 2010年, Materials, 3 (6), 3625 - 3641, 英語[査読有り]
研究論文(学術雑誌)
Recrystallization in a tetragonal tetra-n-butyl ammonium bromide (hereafter, TBAB) semi-clathrate hydrate system has been investigated in TBAB aqueous solutions of two different concentrations (stoichiometric mole fraction for tetragonal TBAB hydrate formation and lower mole fraction than stoichiometric one) by use of optical microscopy. The recrystallization of TBAB hydrate has been observed under milder condition than that of the initial crystallization in both concentrations. In particular, solution of the lower concentration is easily recrystallized. This is the first observation of memory effect in a semi-clathrate hydrate system. In addition, the recrystallization occurs in the vicinity of the place where the last piece of initial crystal was dissociated. This implies that a small amount of residual structures remain in the dissociated water, but unfortunately they cannot be confirmed with Raman micro-spectroscopy. (C) 2010 Elsevier Ltd. All rights reserved.
PERGAMON-ELSEVIER SCIENCE LTD, 2010年, Chemical Engineering Science, 65 (20), 5442 - 5446, 英語[査読有り]
研究論文(学術雑誌)
[査読有り]
メタンハイドレート(MH)は、水分子が水素結合により籠を作り、内部に1分子のメタンを捕獲した構造をしており、深海底の堆積物中や永久凍土層などに存在している。MHの生成年代については、129Iを用いた方法などで行われている(Fehn et al., 2000)が、この方法はMHそのものを分析し、生成年代の決定を行っているわけではない。そこで、我々は海底のMHが堆積物中に存在し、堆積物に含まれる放射性同位体元素からの自然放射線を受ける環境にあることに着目し、化学反応によって生成するMH中の微量成分を分析することで生成年代決定を目指している。我々は放射線によってラジカル反応が起こり、メタノールが生成しているのではないかと考えた。本研究では生成年代決定を目指すための基礎実験として合成したMH用い、放射線照射によりメタノールがどのくらい生成するのかを検証した。
日本地球化学会, 2009年, 日本地球化学会年会要旨集, 56, 140 - 140, 日本語過去の気候変動を知るためにそれぞれの時代における大気循環システムの再現は重要な課題である。それを調べるため、過去の風送塵が研究されてきた。風送堆積物中の石英のE1'中心の信号強度によって示される酸素空孔量(Toyoda and Ikeya, 1991)の測定から、最終氷期と完新世とでその起源が異なることが報告された(成瀬他1997; Ono et al., 1998; Toyoda and Naruse 2002)。この後、石英中の酸素空孔量に加え、石英の結晶化度を指標として日本海堆積物の起源地の変動と気候変動との相関について議論された (Nagashima et al., 2007)。一方、石英中にはE1'中心のほかに不純物中心も観測される。今回、これまで用いられてきた指標に加えて不純物中心を用いる可能性について検討した。
一般社団法人日本地球化学会, 2009年, 日本地球化学会年会要旨集, 56 (0), 22 - 22, 日本語[査読有り]
Inclusion of 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxyl (TEMPOL) radical into an organic one-dimensional (1-D) nanochannels formed in guest-free tris(o-phenylenedioxy)cyclotriphosphazene (TPP) was attempted. The inclusion of TEMPOL molecules adsorbed into the TPP nanochannel and their molecular orientation and dynamics were confirmed by temperature-dependent election spin resonance (ESR) measurements. In the specimens prepared by co-precipitation, the existence of 1-D spin diffusion was suggested from the ESR line shape, but the diffusion was not as effective as in the case of the TPP and 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) inclusion compound reported in our previous article. These results imply a new methodology for the preparation of a new organic magnet using TPP as a template.
TAYLOR & FRANCIS LTD, 2009年, Molecular Crystals and Liquid Crystals, 506 (1), 150 - 167, 英語[査読有り]
研究論文(学術雑誌)
It is suggested that the uplift of Himalaya-Tibetan Plateau enhanced interior aridity in East Asia and resulted in development of middle latitude gobi and sandy deserts and accumulation of the eolian sediments in the Chinese Loess Plateau. Therefore, estimation of the provenance for eolian sediments in the Chinese Loess Plateau is critical to reconstruct the environmental changes in East Asia and their relation to the Himalaya-Tibetan Plateau uplift. We recently developed a new provenance tracing method by using a combination of Electron Spin Resonance (ESR) signal intensity and Crystallinity Index (CI) of quartz, and demonstrated that fine fraction of the surface sediments from nine major deserts in East Asia could be distinguished one another on the ESR signal intensity versus CI diagram. Here, we measured ESR signal intensity and CI of quartz in fine fractions of samples covering the last 7 Ma obtained from Lingtai section in the central Chinese Loess Plateau, and compared the results with those of the surface samples from nine major deserts in East Asia. The results suggest that the provenance of fine fraction of the eolian sediment in Lingtai section changed at 4.3, 2.1, 1.4, 1.1, 0.8 and 0.4 Ma. During 7 to 4.3 Ma, the dust might be have been supplied from Precambrian to Paleozoic metamorphic and granitic rocks and granite exposed in the present central to eastern part of the Tian Shan Mountains. The contribution from the Taklimakan desert appeared at 4.3 Ma, increased drastically at 1.1 Ma, and persisted till 0.8 Ma, whereas the main source of detrital material to the Taklimakan desert might have changed from eastern part of the Kunlun and the Altyn Mountains to western part of the Kunlun and the Tian Shan Mountains. During 0.8 to 0.4 Ma, contribution from the Badain Juran desert gradually increased. Finally, contribution from the Tengger desert appeared from 0.4 to 0 Ma. Together with tectonic evidences from literatures, the provenance changes from 4.3 to 0.8 Ma seem to reflect uplift of the Tian Shan and the Kunlun Mountains and consequent formation of the Taklimakan desert, whereas the change at 0.4 Ma may reflect uplift of the Qilian Mountains although formation of mountain glaciers could be an alternative possibility. These provenance changes will provide important constraints not only on the development of arid areas and evolution of monsoon but also on the uplift and erosion of mountains in East Asia.
2008年03月, Climate of the Past Discussions, 4, 335 - 374, 英語[査読有り]
[査読有り]
研究論文(学術雑誌)
Electron spin resonance measurement of gamma-ray-irradiated propane hydrates shows that the normal propyl radical withdraws hydrogen from the adjacent propane molecule through the hexagonal planes of the hydrate cage without water molecule bridging.
ROYAL SOC CHEMISTRY, 2008年, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 10 (1), 80 - 82, 英語[査読有り]
研究論文(学術雑誌)
A mixture of 2,2,6,6-tetramethyl-1-piperidinyloxyl (TEMPO) radical and 2,2,6,6-tetramethyl-1-piperidine (TEMP) was included into organic 1-D nanochannels of tris(o-phenylenedioxy) cyclotriphosphazene (TPP) crystal. Dilution of the paramagnetic TEMPO radical was achieved with excess TEMP, thereby isolating a TEMPO molecule in the nanochannel. For inclusion compounds of TPP with TEMPO and TEMP (TEMPO/all guest compounds = 0.017 (1), and 0.15 (2)), temperature-dependent electron spin resonance (ESR) spectra were observed to investigate their molecular dynamics and orientation. In the temperature range from 112 K to room temperature, the spectra depended remarkably on the temperature. Temperature dependence was well interpreted by uniaxial rotation, suggesting that TEMPO molecules undergo uniaxial rotation about a channel axis with a molecular orientation in which the N-O bond in the nitroxide group is perpendicular to the channel axis. The activation energy of uniaxial rotation was evaluated as 4.5 +/- 0.3 kJ mol(-1).
ROYAL SOC CHEMISTRY, 2008年, Physical Chemistry Chemical Physics, 10 (9), 1263 - 1269, 英語[査読有り]
研究論文(学術雑誌)
Electron spin resonance (ESR) study on gamma-irradiated synthetic ethylene hydrate was performed to investigate induced radicals and their thermal stability. ESR spectra of induced 3-butenyl radical (center dot CH2C2H3=CH2, g = 2.0039 +/- 0.0005, A(alpha) =2.2 +/- 0.1 mT and A(beta) =3.0 0.1 mT) and induced ethyl radical (center dot C2H5, g = 2.0044 +/- 0.0005, A(alpha) = 2.2 +/- 0.1 mT and A(beta) = 2.7 0.1 mT) were observed in irradiated ethylene hydrate. The decay of the 3-butenyl radicals was observed above 200 K with the activation energy of 51.9 +/- 4.4 kJ/mol. The obvious decay of ethyl radicals starts above 240 K that is close to the dissociation temperature of ethylene hydrate at atmospheric Pressure. The activation energy of the ethyl radical decay is estimated as 63.4 +/- 8.2 kJ/mol and nearly equal to the enthalpy change of ethylene hydrate into liquid water and gaseous ethylene. It is Suggested that the decay of ethyl radicals Would be caused by the hydrate dissociation and that ethylene hydrate dissociates into water (supercooled) and ethylene at 240-265 K. (c) 2007 Elsevier Ltd. All rights reserved.
PERGAMON-ELSEVIER SCIENCE LTD, 2007年09月, Radiation Measurements, 42 (8), 1301 - 1306, 英語[査読有り]
研究論文(学術雑誌)
Electron spin resonance (ESR) studies have been performed to investigate radicals induced in ethane hydrate irradiated by gamma-rays at 77 K. Two ESR spectra are observed and identified as the induced ethyl radical (g = 2.0031 +/- 10.0005, A(alpha perpendicular to) = 2.2 +/- 0.1 mT, A(alpha parallel to) = 2.5 +/- 0.1 mT, A(beta) = 2.7 +/- 0.1 mT) and induced atomic hydrogen (g = 2.0026 +/- 0.0005, A = 50.5 +/- 0.1 mT). From the results of ESR analysis and gas mass spectroscopy, it is concluded that the ethyl radical decays into butane by dimerization in the first-order reaction in the temperature region of 250-265 K. The activation energy of the decay reaction is 73.1 +/- 16.3 kJ/mol, which is near the dissociation enthalpy change of ethane hydrate to liquid water and gaseous ethane. This finding implies that ethane hydrate does not dissociate into ice but supercooled water in the present temperature region, similar to the dissociation of methane hydrate in our previous study.
INST PURE APPLIED PHYSICS, 2007年05月, Japanese Journal of Applied Physics, 46 (5A), 3066 - 3070, 英語[査読有り]
研究論文(学術雑誌)
Orbital- and millennial-scale variations in the Asian monsoon and its probable association with the Dansgaard-Oeschger (D-O) Cycles have been demonstrated by previous studies. However, the origin and nature of such variations are poorly understood. The Japan Sea is located down wind of the arid areas of the Eurasian continent, and thus receives significant amounts of aeolian dust. Consequently, the hemipelagic sediments of the Japan Sea are expected to record a continuous aeolian dust accumulation, which may provide information about the past variations in Asian monsoon. Grain size, flux, and provenance of aeolian dust in the sediments were examined using two sediment cores obtained from the northern and southern parts of the Japan Sea in order to understand the spatial variability of Asian monsoon. Since the silt fraction of the detrital materials in hemipelagic sediments of the Japan Sea is composed predominantly of aeolian dust, the grain size, flux, and provenance of the silt fraction were examined. The Taklimakan Desert-Loess Plateau and Siberia-Northeast China areas were identified as possible source areas of aeolian dust in the sediments of the Japan Sea based on the Electron Spin Resonance (ESR) signal intensity and crystallinity of quartz. Moreover, the relative contribution of aeolian dust from each source area was estimated based on the ESR signal intensity and crystallinity of quartz. Aeolian dust fluxes from the two source areas at the southern site were then estimated. Grain size and flux of eolian dust at the northern site, and fluxes of aeolian dust from two source areas at the southern site show orbital-scale variations in harmony with the insolation change at 30° N in June. These results indicate orbital-scale changes in the extent of the arid area and/or frequency of dust storms in the Taklimakan Desert-Loess Plateau and Siberia-Northeast China areas, and suggest that southward (northward) shifts of the westerly jet axis occurred together with either intensified (weakened) winter monsoon, decreased (increased) winter precipitation in the Siberia-Northeast China area, or southeastward (northwestward) shifts of summer monsoon limit during periods of smaller (larger) insolation at 30° N in June. In addition to these orbital-scale variations, millennial-scale variations possibly associated with the D-O Cycles are observed in the grain size record of aeolian dust at the two sites. Based on analogy with orbital-scale variations, these millennial-scale variations are considered to reflect millennial-scale changes in the position of the westerly jet axis together with the changes either in winter monsoon intensity, winter precipitation, or position of summer monsoon limit. Our results suggest N-S oscillations in the westerly jet and summer monsoon limit, and changes in the intensity of the winter monsoon on orbital and millennial timescales. © 2007 Elsevier B.V. All rights reserved.
2007年04月20日, Palaeogeography, Palaeoclimatology, Palaeoecology, 247 (1-2), 144 - 161, 英語[査読有り]
研究論文(学術雑誌)
[査読有り]
研究論文(国際会議プロシーディングス)
[査読有り]
研究論文(学術雑誌)
[査読有り]
研究論文(学術雑誌)
[査読有り]
研究論文(学術雑誌)
The stability of methyl radicals formed in synthetic methane hydrate by gamma-ray irradiation at 77 K was studied at 200-273 K and 10 MPa. The methyl radicals decayed under these conditions, despite the stability of methane hydrate, and changed into other molecules that could not be detected by electron spin resonance (ESR). Decay products were investigated by gas cell infrared (IR) spectroscopy by measuring the decomposed gas from the gamma-irradiated methane hydrate. Only ethane molecules were detected from the irradiated sample, while these were absent in an unirradiated sample. The molar ratio of ethane to methane (C2H6/CH4) was 12 +/- 1 ppm, which did not contradict with that of methyl radical to methane (CH3./CH4) in the literature. Hence, most of the methyl radicals generated by irradiation were supposed to be transformed to ethane in methane hydrate.
INST PURE APPLIED PHYSICS, 2007年01月, Japanese Journal of Applied Physics, 46 (1), 455 - 460, 英語[査読有り]
研究論文(学術雑誌)
Synthetic methane hydrate irradiated by gamma-rays at 77 K was measured by electron spin resonance (ESR) to investigate the thermal stability of the methyl radical under different pressures from 0.003 to I MPa. The decay of the radical was composed of at least two decay processes. The first decay process was observed within an annealing time of 150 min and the second one on a longer time scale. The decay constant for the second process was estimated using a second order decay model. An Arrhenius plot gave almost the same activation energy at lower temperature under each pressure, and it was estimated to be 20.0 +/- 2.7 kJ/mol. (c) 2006 Elsevier Ltd. All rights reserved.
PERGAMON-ELSEVIER SCIENCE LTD, 2006年08月, Radiation Measurements, 41 (7-8), 1040 - 1044, 英語[査読有り]
研究論文(学術雑誌)
The study investigated the luminescence behaviour of natural olivine to discuss the potential for Cenozoic (quaternary) dating. The UV-blue thermoluminescence (TL) glow curves of irradiated olivines have a resolved peak at 190 degrees C and other peaks at higher temperature at lower dose levels, and broad signals around 275-310 and 375-400 degrees C at higher dose levels. The UV-blue TL increases with additional laboratory dose to similar to 1.6 kGy within a plateau temperature region, suggesting the possibility of dosimetry and Cenozoic dating. Both infrared stimulated luminescence (IRSL) and blue light stimulated luminescence (BLSL) were detected from laboratory-irradiated olivines although the BLSL was weaker than the IRSL. Furthermore, post-BL IRSL was detected but post-IR BLSL was not observed. Therefore, IR stimulation is recommended for optically stimulated luminescence measurements with natural olivine. The growth of the IRSL signal component with doses less than several tens of Gy are too weak to measure. The dose-response curves suggest that further investigations on various types of olivine are needed for practical IRSL dating in the late Pleistocene or more recent. (c) 2006 Elsevier Ltd. All rights reserved.
PERGAMON-ELSEVIER SCIENCE LTD, 2006年08月, RADIATION MEASUREMENTS, 41 (7-8), 982 - 986, 英語[査読有り]
研究論文(学術雑誌)
The thermal stability of gamma-ray-induced methyl radicals in methane hydrate was studied using the ESR method at atmospheric pressure and 210-260 K. The methyl radical decay proceeded with the second-order reaction, and ethane molecules were generated from the dimerization process. The methyl radical decay proceeds by two different temperature-dependent processes, that is, the respective activation energies of these processes are 20.0 +/- 1.6 kJ/mol for the lower temperature region of 210-230 K and 54.8 +/- 5.7 kJ/mol for the higher temperature region of 235-260 K. The former agrees well with the enthalpy change of methane hydrate dissociation into ice and gaseous methane, while the latter agrees well with the enthalpy change into liquid water and gaseous methane. The present findings reveal that methane hydrates dissociate into liquid (supercooled) water and gaseous methane in the temperature range of 235-260 K.
AMER CHEMICAL SOC, 2005年11月, JOURNAL OF PHYSICAL CHEMISTRY B, 109 (44), 21086 - 21088, 英語[査読有り]
研究論文(学術雑誌)
Antarctic ice and rime ice after T-irradiation at 77 K were studied by electron spin resonance (ESR). The signal of nitrogen dioxide (NO2) was detected in both ices. The NO2 in the Antarctic ice, in particular, may be created from NO3- by reactions associated with intrinsic OH radicals. The detection limit of NO2 in solid samples was estimated to be similar to0.02 ppm with ESR. The analysis using ESR, in natural ice has a potential to trace environmental NO2. (C) 2004 Elsevier Ltd. All rights reserved.
PERGAMON-ELSEVIER SCIENCE LTD, 2005年02月, Applied Radiation and Isotopes, 62 (2), 255 - 259, 英語[査読有り]
研究論文(学術雑誌)
Natural methane hydrate under deep ocean floor in Ocean Drilling Program (ODP) Leg 164 was studied by electron spin resonance (ESR) after gamma-ray irradiation. The methyl radical (g = 2.0024 +/- 0.0005, A = 2.3 +/- 0.1 mT) as well as an unidentified signal was observed. Although the parameters and the thermal stability. were very similar to those in a synthetic sample, the signal. intensity was about one eightieth of that in synthetic one because methane hydrate had partially changed to ice. ESR signal intensity of the methyl radical after gamma-ray irradiation could be used to estimate the amount of methane hydrate in a sample mixed with ice. (C) 2004 Published by Elsevier Ltd.
PERGAMON-ELSEVIER SCIENCE LTD, 2005年02月, Applied Radiation and Isotopes, 62 (2), 371 - 374, 英語[査読有り]
研究論文(学術雑誌)
A scanning electron spin resonance (ESR) microscope using a localized microwave field was redesigned to measure ESR spectra from 0 to 400 mT using electromagnets: Divalent copper ion (Cu2+) in copper sulfate pentahydrate (CuSO4.5H(2)O) was imaged, after the powdered samples were cemented in silicone rubber under a magnetic field. The ratio of the two signal intensities at g = 2.27 and 2.08 clearly indicates the orientation of the particles. This method can be used for mapping the local magnetic field and its direction. (C) 2004 Published by Elsevier Ltd.
PERGAMON-ELSEVIER SCIENCE LTD, 2005年02月, Applied Radiation and Isotopes, 62 (2), 343 - 348, 英語[査読有り]
研究論文(学術雑誌)
[査読有り]
研究論文(学術雑誌)
Synthetic methane hydrate irradiated by gamma-rays at 77 K has been measured by electron spin resonance (ESR). The quartet signal at g = 2.0029 +/- 0.0005 with the intensity ratio of approximately 1 : 3 : 3 : I and hyperfine coupling constant A = 2.3 +/- 0.1 mT was identified as the methyl radical (CH3..). The dose response of its signal intensities showed that the radicals were formed linearly up to 10 kGy with the G-value [the formation efficiency of radical pairs per 100 eV (16 aJ)] of 0.05. According to annealing experiments, the radical became unstable over 200 K, at which thermal dissociation of the hydrate had already started, but a very weak signal was detectable up to 270 K. The methyl radical thermally decayed following second-order kinetics with an activation energy of 0.26 +/- 0.02 eV (42 zJ). The existence of the signal at 270 K would be related to the extremely slow dissociation referred to as the self-preservation effect of the gas hydrate.
INST PURE APPLIED PHYSICS, 2004年01月, Japanese Journal of Applied Physics, 43 (1), 353 - 357, 英語[査読有り]
研究論文(学術雑誌)
Nitrate radical NO32- in calcitic evaporate was discovered in Antarctica. The distribution and formation of nitrate radical NO32- in the calcite have been studied by pulse and continuous-wave electron spin resonance. In samples that had been annealed to destroy the NO32-, regeneration of the radical by gamma-rays or UV light indicated that the radical was formed by UV light (with wavelengths less than 340 nm) from solar rays, not by environmental radiation. The nonuniform spatial distribution of the nitrate radical, which was deduced from high ratios of local spin density to total spin density, suggests that the nitrate impurity was introduced into the calcium carbonate after carbonate grain formation. Formation of the carbonate-containing nitrate requires the presence of high amounts of nitrate and a dry climate. Formation of the nitrate radical requires sample exposure to UV light. These conditions are satisfied in the environment of Antarctica.
SPRINGER WIEN, 2004年, Applied Magnetic Resonance, 26 (4), 601 - 616, 英語[査読有り]
研究論文(学術雑誌)
Free radicals ascribed to ascorbic acid (AscHZ), vitamin C, in the solid matrix of synthetic calcium carbonate have been studied using electron spin resonance (ESR) after UV irradiation. A new ESR signal with g-factors of g(parallel to) = 2.0024 and g(perpendicular to) = 2.0053 was found together with a broad singlet signal around g = 2.005 and a doublet signal at g = 2.0053 separated by 0.18 mT due to the ascorbyl radical (Asc(.-)). The molecular orbitals of Asc(.-) and two other types of ascorbyl radical (AscH(.-)) were calculated using the semi-empirical PM3 unrestricted Hartree-Fock (UHF) method, which indicated that the hyperfine splitting due to hydrogen bonded to one of the carbons in the pentagonal ring was dominant. The axial signal was ascribed to AscH(.-), while the doublet signal was ascribed to Asc(.-) in CaCO3. Possible pharmaceutical and nutritional applications of embedding unstable active molecules into the crystalline lattice of CaCO3 and a new nondestructive method for determination of vitamin C contents are discussed because the vitamin C has higher thermal stability in the carbonate than that in aqueous solution.
INST PURE APPLIED PHYSICS, 2003年02月, JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS, 42 (2A), 428 - 433, 英語[査読有り]
研究論文(学術雑誌)
[査読有り]
研究論文(学術雑誌)
Optically stimulated luminescence (OSL) of synthetic stishovite was investigated for a future dating technique of meteor impact craters. Luminescence around 330 nm was measured on the γ-ray irradiated stishovite under two stimulating light sources of infrared laser (830 nm) and blue light emitting diode set (470 nm). Thermoluminescence (TL) studies before and after the OSL measurements showed the intensities around 100-200 °C and 220-350 °C to increase and those around 350-450 °C to decrease. This indicates that a part of deep-trapped charges excited during the OSL measurements were retrapped by shallower traps. The infrared stimulated luminescence (IRSL) after the TL measurement up to 450 °C could not be detected, while the blue light stimulated luminescence (BLSL) after TL had about one-tenth of the intensity before TL. This indicates that a part of the charges in shallower traps were detrapped thermally and returned to the deeper traps which were related to BLSL. The result implies that some of the BLSL-related traps are quite stable at room temperature and could be used for geological dating. In addition, two paramagnetic centers produced by sudden release of high pressure in synthesis process were found in the unirradiated stishovite by electron spin resonance (ESR). Their g-factors are g∥ = 2.00181 and g⊥ = 2.00062 for an axial signal and g = 2.00305 for the other isotropic signal. These signals could be used for an evidence of impacts if those signals could be stored in geological time.
Elsevier Science Ltd, 2000年12月15日, Radiation Measurements, 32 (5), 473 - 477, 英語[査読有り]
研究論文(学術雑誌)
A new unidentified electron center in gamma-ray-irradiated synthetic stishovite, a high-pressure polymorph of SiO2, was detected by X-band electron spin resonance. It has an anisotropic g-factor of orthorhombic symmetry, g(1) = 1.9764, g(2) = 1.9527 and g(3) = 1.9370. The signal intensity was saturated at a microwave power of 2 mW. Annealing experiments show that the center was annealed out around 280 K and unstable at room temperature. The center may be ascribed to a titanium electron center on the basis of a relatively large g-shift and a comparison with the paramagnetic centers in quartz.
SPRINGER WIEN, 2000年, APPLIED MAGNETIC RESONANCE, 18 (4), 559 - 564, 英語[査読有り]
研究論文(学術雑誌)
[査読有り]
研究論文(学術雑誌)
Electron spin resonance (ESR) spectroscopy is a sensitive tool for distinguishing between 'burned' and 'unburned' states of archaeological objects. Prehistoric heating conditions, such as the temperature, atmosphere, time of exposure to heat, and when the heating took place, can be studied by this method with some success. ESR 'reporters', such as (a) radiation defects, (b) pyrolytic defects, and (c) transition metal ions, can even reflect changes induced at relatively low temperatures (e.g., in the range of 200°C for objects containing organic compounds). Several ESR heating markers are so stable that samples dating back to the ages when fire first began to be used can be analyzed today. An overview is presented of the literature concerning objects, such as stone, soil, pottery, and plant and animal products.
Springer Verlag, 1998年, Naturwissenschaften, 85 (10), 474 - 481, 英語[査読有り]
研究論文(学術雑誌)
The electromagnetic (EM) behavior of a geological fault is postulated to follow the mathematical model of a fault in seismology that illustrates seismic EM anomalies (EMAs). Charge densities, +q and -q in C/m(2) are generated at a fault zone by the change in seismic stress, sigma as dq/dt = -alpha d sigma/dt - q/epsilon rho, where sigma,epsilon and rho are the charge generation constants measured in C/N, dielectric constant and resistivity of bedrocks, respectively. A fault of length, 2a, plane area, A and the displacement or rupture time, tau gives pulsed charge densities, +g(t) and -q(t), or a dipole moment of P(t) = 2aAq(t) = alpha M-0[epsilon rho/(tau-epsilon rho)][exp(-t/tau) - exp(-t/epsilon rho)] using the earthquake moment M-0. Maxwell's equations for this dipole in a conductive earth give power spectra of EM waves at different distances. Seismic electric signals (SES) including the DC VAN method can be explained as EM waves. Electrons with density n in the atmosphere are accelerated by the electric field and travel a distance l, resulting in the excitation and ionization of atmospheric molecules leading to earthquake lightning (EQL). They also polarize the ionosphere by disturbing the transmission of EM waves. Preliminary results of pulsed electric field measurements are presented for lightning, prior to an earthquake and artificial electronic noises. The same pulsed field surprised eels and hamsters, suggesting seismic anomalous animal behavior (SAAB) as electro-physiological responses to the stimuli of electric pulses.
WORLD SCIENTIFIC PUBL CO PTE LTD, 1997年06月, JOURNAL OF CIRCUITS SYSTEMS AND COMPUTERS, 7 (3), 153 - 164, 英語[査読有り]
研究論文(学術雑誌)
Models of uranium-uptake at the early stage and at a constant rate (linear-uptake) were reexamined for ESR dating of fossil bones and teeth. An analytical equation for the total dose of natural radiation (D-T) was obtained for uranium uptake in the form of a saturation function, C-U(t) = C-US(1 - e(-lambda t)), where C-US is the saturation level of the uranium and lambda is the uranium uptake rate, presumably associated with the decomposition rare of organic materials and the diffusion of uranium. The present uranium content C-U(T) = C-U* at the unknown age T gives C-US = C-U*/(1 - e(-lambda T)) and so lambda = -(1/T)ln(1 - C-U*/C-US). The D-T calculated by taking U-238-series secular disequilibrium into account is reduced to that of an early uptake for lambda T much greater than 1 and to that of a linear uptake for lambda T much less than 1. The activity ratios of U-234/U-238 and Th-230/U-238 for the saturation-uptake model are also given. The model of linear uptake is applicable for C-U* < C-US. The curves of D-T as a function of T were calculated for C-US as a parameter. (C) 1997 Elsevier Science Ltd.
PERGAMON-ELSEVIER SCIENCE LTD, 1997年04月, RADIATION MEASUREMENTS, 27 (2), 339 - 343, 英語[査読有り]
研究論文(学術雑誌)
Deconvolution of X-band spectra has shown that the signal that is used in dating studies is composed of at least three different peaks. Our measurements show that pulsed ESR can separate the axial signal from two wider peaks that are suspected of interfering with any reliable dose assessment. However, its significantly lower sensitivity prohibits the routine application of pulsed ESR in dating studies. The spin relaxation time, T-2, of the CO2- centre as determined from spin echo decay curves, is in the range of about 500 to 640 ns, depending on the spin concentration. (C) 1997 Elsevier Science Ltd.
PERGAMON-ELSEVIER SCIENCE LTD, 1997年04月, RADIATION MEASUREMENTS, 27 (2), 425 - 431, 英語[査読有り]
研究論文(学術雑誌)
We have used thin sections of an archaeological tooth sample to obtain spatially resolved ESR spectra using a pin-hole cavity. This study presents the first ESR images of naturally generated radiation sensitive signals. The 3-D plots of the natural and irradiated samples show strong variations of the ESR intensities within the enamel layers. Owing to the relatively large scattering of the data points it has not been possible to produce 3-D dose plots. (C) 1997 Elsevier Science Ltd.
PERGAMON-ELSEVIER SCIENCE LTD, 1997年04月, RADIATION MEASUREMENTS, 27 (2), 331 - 337, 英語[査読有り]
研究論文(学術雑誌)
Electron spin resonance (ESR) of Fe3+ ions and of radiation-induced centers in quartz (E', peroxy and Al centers) was studied to distinguish between burnt and unburnt stone tools and to determine their age. The yellow stone tool with a reddish edge discovered at the paleolithic site in Kamitakamori, northern Japan, was investigated. The ESR spectrum intensity of Fe3+ ions around g = 4.3 and the color of the material changed at 600 degrees C and 240 degrees C, respectively, which indicates that the red part was heated at 240-600 degrees C. The E' center in the red part was used for dating because isochronal annealing experiments showed low thermal stability of the Al center and overlap of broad signals at g = 2.0086 onto the peroxy center. Assuming the same efficiency of defect formation in the red part as of that in the laboratory-heated material at 450 degrees C, the obtained age of 520-770 ka is in concordance with the ages of the tephra layers at the site.
SPRINGER VERLAG, 1997年, APPLIED MAGNETIC RESONANCE, 13 (3-4), 561 - 569, 英語[査読有り]
研究論文(学術雑誌)
A new ESR isochrone dating for fracture age based on the effective annual dose for different grain sizes has been applied to quartz grains in fractured granite at the Nojima fault that moved during the earthquake in 1995 and in fault gouge at the Rokko fault in the vicinity. Incomplete resetting of ESR signals was observed for both samples collected at the ground surface. The fracture age of the quartz grains was obtained for the Rokko fault as (1.6 +/- 0.2) x 10(5) yr. At the Nojima fault there appears to be a considerable effect from previously-fractured surfaces in the newly-fractured material. The relation between the fracture age and the age of the fault movement is discussed. Copyright (C) 1996 Elsevier Science Ltd
PERGAMON-ELSEVIER SCIENCE LTD, 1996年11月, APPLIED RADIATION AND ISOTOPES, 47 (11-12), 1423 - 1426, 英語[査読有り]
研究論文(学術雑誌)
Electron spin resonance (ESR) of transition metal ions (Mn2+, Fe3+), radiation induced centres and pyrolytically formed radicals was studied to distinguish between burnt and unburnt soil. A testfire place and samples from an archaeological site were analyzed. The concentration of radiation induced centres decreases and pyrolytically formed radicals appear in a thermal annealing experiment. The spectral pattern of iron and manganese resonances changes during the heating process. These signals are useful to estimate temperature and atmosphere of the heating event. Chemithermoluminescence (CTL) of the soil was studied and could reveal its thermal history, too.
SPRINGER VERLAG, 1996年, APPLIED MAGNETIC RESONANCE, 11 (3-4), 577 - 586, 英語[査読有り]
研究論文(学術雑誌)
A new isochrone method of electron spin resonance (ESR) dating has been proposed utilizing the different average dose rates of external radiation for different grain sizes due to the range of external alpha- and beta-rays., The equivalent doses (EDs) obtained by the additive dose method were plotted as a function of the external dose rate (D-ex) corrected for the grain sixes. The slope gives an ESR isochrone age since the fracture (T-trn) or the surface formation; the coordinate abscissa gives the internal dose (DmTfor) where D-in is the internal dose rate and T-for is the age of the mineral formation. The method has been applied to quartz (SiO2) grains in geological fault gouge at outcrops of the Rokko Fault giving T-fra=102,000 years and T-for of nearly zero for grains less than 100 mu m.
JAPAN J APPLIED PHYSICS, 1995年03月, JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS, 34 (3A), L334 - L337, 英語[査読有り]
研究論文(学術雑誌)
Tetrabutylammonium bromide (TBAB) hydrate, a semi-clathrate hydrate was investigated by terahertz time-domain spectroscopy (THz-TDS) in the region from 0.1 to 1.5 THz. The high absorption was observed in the whole region in comparison with that in ice and propane hydrate. In addition, absorption band was clearly observed around 1.1 THz, though ice and propane hydrate does not have such a peak at this frequency. This peak in TBAB hydrate may be caused by intermolecular vibration of tetrabutylammonium ion because TBAB crystal also has infrared activity at 1.4 THz. In TBAB hydrate, tetrabutylammonium ion is isolated by hydrogen-bonded water molecules, which might cause the absorption peak shift to lower frequency. THz-TDS is worthwhile to observe the interaction of guest-guest and/or guest-host molecules.
2018年10月29日, 2018 43rd International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz), 2018-September, 英語[査読有り]
研究発表ペーパー・要旨(全国大会,その他学術会議)
記事・総説・解説・論説等(学術雑誌)
[査読有り][招待有り]
速報,短報,研究ノート等(大学,研究機関紀要)
The symposium "Development in Scientific Researches on Gas Hydrates" was held at the 53< sup> rd< /sup> High Pressure Conference of Japan on November 2012. After some presentations in the symposium, the possibilities of improving or transcending the van der Waals & Platteeuw model for the phase equilibrium estimation including clathrate hydrate phase were discussed. In this article, a part of the discussion was reported.
2013年, 高圧力の科学と技術, 23 (2), 141 - 147, 日本語[査読有り]
研究発表ペーパー・要旨(全国大会,その他学術会議)
[査読有り]
研究発表ペーパー・要旨(全国大会,その他学術会議)
[査読有り]
研究発表ペーパー・要旨(全国大会,その他学術会議)
河川や風によって陸上や海底へと運搬される砕屑物粒子は、その量や供給源の変化を調べることで、粒子の運搬に関わる諸現象(例えば河川流量や風の強さ、向きなど)の変動を解明することができる。そこで我々は、砕屑物粒子の供給源推定に向けた指標開発に取り組んできた。石英は地球上の様々な岩石に多く含まれ、また風化に強いという特性を持ち、運搬・堆積過程での変質を受けにくいため、供給源推定に用いるのに適している。特に我々が注目したのは、石英の結晶中の構造欠陥(不対電子や格子欠陥)や不純物元素を測定する、石英の電子スピン共鳴(Electron Spin Resonance:ESR)分析とカソードルミネッセンス(Cathodoluminescence : CL)分析である。本発表では、これらの指標が供給源推定にどれだけ有効であるのか、またSEM-CLを用いた分析で一石英粒子からの供給源推定が可能かどうかについて述べる予定である。
一般社団法人日本地球化学会, 2009年, 日本地球化学会年会講演要旨集, 56th (0), 22 - 23, 日本語研究発表ペーパー・要旨(全国大会,その他学術会議)
[査読有り]
研究発表ペーパー・要旨(全国大会,その他学術会議)
メタンハイドレートに生成するラジカル種の安定性とその後の反応過程について研究した.主に生成するメテルラジカルは,メタンハイドレートが安定であっても温度によっては二次反応に従い減少すること,消滅後はエタンとなることがわかった.地球に存在するメタンハイドレートでは時間が経つにつれエタンが増加していくが,より低い温度の水衛星などでメタンハイドレートが形成されていれば,ハイドレート内にラジカルが蓄積することがわかった.一方,氷Ihに生成する主なラジカルのヒドロキシルラジカルは77Kでは見られなかった.氷物質中における化学反応を考える上で,メタンハイドレートのような有機物を含む氷物質の影響を考慮すべきことが示唆された.
日本惑星科学会, 2007年03月25日, 日本惑星科学会誌「遊星人」, 16 (1), 47-52 - 52, 日本語[査読有り]
速報,短報,研究ノート等(学術雑誌)
研究発表ペーパー・要旨(全国大会,その他学術会議)
速報,短報,研究ノート等(大学,研究機関紀要)
研究発表ペーパー・要旨(全国大会,その他学術会議)
研究発表ペーパー・要旨(全国大会,その他学術会議)
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