36 results on '"Takeshi SAKAI"'
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2. Sound velocity of hexagonal close-packed iron to the Earth’s inner core pressure
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Daijo Ikuta, Eiji Ohtani, Hiroshi Fukui, Takeshi Sakai, Daisuke Ishikawa, and Alfred Q. R. Baron
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Science - Abstract
New constraints on the composition of Earth’s inner core are provided by experimental verification of Birch’s law for hexagonal close-packed iron to pressure above 300 gigapascals, about double the pressure achieved in previous investigations
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- 2022
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3. In situ X-ray and acoustic observations of deep seismic faulting upon phase transitions in olivine
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Tomohiro Ohuchi, Yuji Higo, Yoshinori Tange, Takeshi Sakai, Kohei Matsuda, and Tetsuo Irifune
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Science - Abstract
Abstract The activity of deep-focus earthquakes, which increases with depth from ~400 km to a peak at ~600 km, is enigmatic, because conventional brittle failure is unlikely to occur at elevated pressures. It becomes increasingly clear that pressure-induced phase transitions of olivine are responsible for the occurrence of the earthquakes, based on deformation experiments under pressure. However, many such experiments were made using analogue materials and those on mantle olivine are required to verify the hypotheses developed by these studies. Here we report the results of deformation experiments on (Mg,Fe)2SiO4 olivine at 11−17 GPa and 860−1350 K, equivalent to the conditions of the slabs subducted into the mantle transition zone. We find that throughgoing faulting occurs only at very limited temperatures of 1100−1160 K, accompanied by intense acoustic emissions at the onset of rupture. Fault sliding aided by shear heating occurs along a weak layer, which is formed via linking-up of lenticular packets filled with nanocrystalline olivine and wadsleyite. Our study suggests that transformational faulting occurs on the isothermal surface of the metastable olivine wedge in slabs, leading to deep-focus earthquakes in limited regions and depth range.
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- 2022
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4. Digging into the Interior of Hot Cores with ALMA (DIHCA). IV. Fragmentation in High-mass Star-forming Clumps
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Kousuke Ishihara, Patricio Sanhueza, Fumitaka Nakamura, Masao Saito, Huei-Ru Vivien Chen, Shanghuo Li, Fernando Olguin, Kotomi Taniguchi, Kaho Morii, Xing Lu, Qiu-yi Luo, Takeshi Sakai, and Qizhou Zhang
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Star formation ,Star forming regions ,Massive stars ,Dust continuum emission ,Astrophysics ,QB460-466 - Abstract
Fragmentation contributes to the formation and evolution of stars. Observationally, high-mass stars are known to form multiple-star systems, preferentially in cluster environments. Theoretically, Jeans instability has been suggested to determine characteristic fragmentation scales, and thermal or turbulent motion in the parental gas clump mainly contributes to the instability. To search for such a characteristic fragmentation scale, we have analyzed Atacama Large Millimeter/submillimeter Array (ALMA) 1.33 mm continuum observations toward 30 high-mass star-forming clumps taken by the Digging into the Interior of Hot Cores with ALMA survey. We have identified 573 cores using the dendrogram algorithm and measured the separation of cores by using the Minimum Spanning Tree technique. The core separation corrected by projection effects has a distribution peaked around 5800 au. In order to remove biases produced by different distances and sensitivities, we further smooth the images to a common physical scale and perform completeness tests. Our careful analysis finds a characteristic fragmentation scale of ∼7000 au, comparable to the thermal Jeans length of the clumps. We conclude that thermal Jeans fragmentation plays a dominant role in determining the clump fragmentation in high-mass star-forming regions, without the need to invoke turbulent Jeans fragmentation.
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- 2024
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5. The ALMA Survey of 70 μm Dark High-mass Clumps in Early Stages (ASHES). XI. Statistical Study of Early Fragmentation
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Kaho Morii, Patricio Sanhueza, Qizhou Zhang, Fumitaka Nakamura, Shanghuo Li, Giovanni Sabatini, Fernando A. Olguin, Henrik Beuther, Daniel Tafoya, Natsuko Izumi, Ken’ichi Tatematsu, and Takeshi Sakai
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Star formation ,Infrared dark clouds ,Astrophysics ,QB460-466 - Abstract
Fragmentation during the early stages of high-mass star formation is crucial for understanding the formation of high-mass clusters. We investigated fragmentation within 39 high-mass star-forming clumps as part of the Atacama Large Millimeter/submillimeter Array Survey of 70 μ m Dark High-mass Clumps in Early Stages (ASHES) survey. Considering projection effects, we have estimated core separations for 839 cores identified from the continuum emission and found mean values between 0.08 and 0.32 pc within each clump. We find compatibility of the observed core separations and masses with the thermal Jeans length and mass, respectively. We also present subclump structures revealed by the 7 m array continuum emission. Comparison of the Jeans parameters using clump and subclump densities with the separation and masses of gravitationally bound cores suggests that they can be explained by clump fragmentation, implying the simultaneous formation of subclumps and cores within rather than a step-by-step hierarchical fragmentation. The number of cores in each clump positively correlates with the clump surface density and the number expected from the thermal Jeans fragmentation. We also find that the higher the fraction of protostellar cores, the larger the dynamic range of the core mass, implying that the cores are growing in mass as the clump evolves. The ASHES sample exhibits various fragmentation patterns: aligned, scattered, clustered, and subclustered. Using the ${ \mathcal Q }$ -parameter, which can help distinguish between centrally condensed and subclustered spatial core distributions, we finally find that in the early evolutionary stages of high-mass star formation, cores tend to follow a subclustered distribution.
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- 2024
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6. The ALMA Survey of 70 μm Dark High-mass Clumps in Early Stages (ASHES). X. Hot Gas Reveals Deeply Embedded Star Formation
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Natsuko Izumi, Patricio Sanhueza, Patrick M. Koch, Xing Lu, Shanghuo Li, Giovanni Sabatini, Fernando A. Olguin, Qizhou Zhang, Fumitaka Nakamura, Ken’ichi Tatematsu, Kaho Morii, Takeshi Sakai, and Daniel Tafoya
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Infrared dark clouds ,Star formation ,Star forming regions ,Massive stars ,Protoclusters ,Protostars ,Astrophysics ,QB460-466 - Abstract
Massive infrared dark clouds (IRDCs) are considered to host the earliest stages of high-mass star formation. In particular, 70 μ m dark IRDCs are the colder and more quiescent clouds. At a scale of about 5000 au using formaldehyde (H _2 CO) emission, we investigate the kinetic temperature of dense cores in 12 IRDCs obtained from the pilot Atacama Large Millimeter/submillimeter Array Survey of 70 μ m dark High-mass clumps in Early Stages (ASHES). Compared to the 1.3 mm dust continuum and other molecular lines, such as C ^18 O and deuterated species, we find that H _2 CO is mainly sensitive to low-velocity outflow components rather than to quiescent gas expected in the early phases of star formation. The kinetic temperatures of these components range from 26 to 300 K. The Mach number reaches about 15 with an average value of about 4, suggesting that the velocity distribution of gas traced by H _2 CO is significantly influenced by a supersonic nonthermal component. In addition, we detect warm line emission from HC _3 N and OCS in 14 protostellar cores, which requires high excitation temperatures ( E _u / k ∼ 100 K). These results show that some of the embedded cores in the ASHES fields are in an advanced evolutionary stage, previously unexpected for 70 μ m dark IRDCs.
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- 2024
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7. Digging into the Interior of Hot Cores with ALMA: Spiral Accretion into the High-mass Protostellar Core G336.01–0.82
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Fernando A. Olguin, Patricio Sanhueza, Huei-Ru Vivien Chen, Xing Lu, Yoko Oya, Qizhou Zhang, Adam Ginsburg, Kotomi Taniguchi, Shanghuo Li, Kaho Morii, Takeshi Sakai, and Fumitaka Nakamura
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Star formation ,Star forming regions ,Massive stars ,Astrophysics ,QB460-466 - Abstract
We observed the high-mass star-forming core G336.01–0.82 at 1.3 mm and 0.″05 (∼150 au) angular resolution with the Atacama Large Millimeter/submillimeter Array (ALMA) as part of the Digging into the Interior of Hot Cores with ALMA survey. These high-resolution observations reveal two spiral streamers feeding a circumstellar disk at opposite sides in great detail. Molecular line emission from CH _3 OH shows velocity gradients along the streamers consistent with infall. Similarly, a flattened envelope model with rotation and infall implies a mass larger than 10 M _☉ for the central source and a centrifugal barrier of 300 au. The location of the centrifugal barrier is consistent with local peaks in the continuum emission. We argue that gas brought by the spiral streamers is accumulating at the centrifugal barrier, which can result in future accretion burst events. A total high infall rate of ∼4 × 10 ^−4 M _☉ yr ^−1 is derived by matching models to the observed velocity gradient along the streamers. Their contribution accounts for 20%–50% the global infall rate of the core, indicating streamers play an important role in the formation of high-mass stars.
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- 2023
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8. Laboratory Measurement of CH2DOH Line Intensities in the Millimeter-wave Region
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Takahiro Oyama, Yuki Ohno, Akemi Tamanai, Yoshimasa Watanabe, Satoshi Yamamoto, Takeshi Sakai, Shaoshan Zeng, Riouhei Nakatani, and Nami Sakai
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Molecular spectroscopy ,Line positions ,Line intensities ,Astrochemistry ,Astrophysics ,QB460-466 - Abstract
Deuterium fractionation in molecules is known as one of the most powerful tools to study chemical processes during star and planet formation. Among various interstellar molecules, methanol often shows very high deuterium fractionation. It is the most abundant saturated organic molecule and is known as a parent species to form more complex organic molecules. However, deriving the abundance of deuterated methanol suffers from the uncertainty in the intrinsic line intensities ( S μ ^2 ) of CH _3 OH isotopologues. Due to their floppy nature, theoretical evaluation of the S μ ^2 values is not straightforward, particularly for asymmetric-top asymmetric-frame isotopologues such as CH _2 DOH. In this study, we have measured the line frequencies and their intensities for CH _2 DOH in the millimeter-wave region from 216 to 264 GHz by using an emission-type millimeter and submillimeter-wave spectrometer. For the a -type J = 5 − 4 transition, the derived S μ ^2 values are 13%–27% larger than those theoretically calculated, except for the transitions of K _a = 2 for e _0 and K _a = 1 for e _1 affected by avoided level crossing. For b -type transitions, significant systematic differences are found between theoretical and experimental S μ ^2 values. The results of the present study enable us to accurately derive from observations the CH _2 DOH abundances, which are essential for understanding deuterium fractionation in various sources.
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- 2023
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9. The ALMA Survey of 70 μm Dark High-mass Clumps in Early Stages (ASHES). IX. Physical Properties and Spatial Distribution of Cores in IRDCs
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Kaho Morii, Patricio Sanhueza, Fumitaka Nakamura, Qizhou Zhang, Giovanni Sabatini, Henrik Beuther, Xing Lu, Shanghuo Li, Guido Garay, James M. Jackson, Fernando A. Olguin, Daniel Tafoya, Ken’ichi Tatematsu, Natsuko Izumi, Takeshi Sakai, and Andrea Silva
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Infrared dark clouds ,Star formation ,Star forming regions ,Protoclusters ,Protostars ,Astrophysics ,QB460-466 - Abstract
The initial conditions found in infrared dark clouds (IRDCs) provide insights on how high-mass stars and stellar clusters form. We have conducted high-angular resolution and high-sensitivity observations toward thirty-nine massive IRDC clumps, which have been mosaicked using the 12 and 7 m arrays from the Atacama Large Millimeter/submillimeter Array. The targets are 70 μ m dark massive (220–4900 M _⊙ ), dense (>10 ^4 cm ^−3 ), and cold (∼10–20 K) clumps located at distances between 2 and 6 kpc. We identify an unprecedented number of 839 cores, with masses between 0.05 and 81 M _⊙ using 1.3 mm dust continuum emission. About 55% of the cores are low-mass (
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- 2023
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10. Degradation of Lignin by Infrared Free Electron Laser
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Takayasu Kawasaki, Heishun Zen, Takeshi Sakai, Yoske Sumitomo, Kyoko Nogami, Ken Hayakawa, Toyonari Yaji, Toshiaki Ohta, Takashi Nagata, and Yasushi Hayakawa
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infrared laser ,lignin ,depolymerization ,vibrational excitation ,Organic chemistry ,QD241-441 - Abstract
Lignin monomers have attracted attention as functional materials for various industrial uses. However, it is challenging to obtain these monomers by degrading polymerized lignin due to the rigid ether linkage between the aromatic rings. Here, we propose a novel approach based on molecular vibrational excitation using infrared free electron laser (IR-FEL) for the degradation of lignin. The IR-FEL is an accelerator-based pico-second pulse laser, and commercially available powdered lignin was irradiated by the IR-FEL under atmospheric conditions. Synchrotron-radiation infrared microspectroscopy analysis showed that the absorption intensities at 1050 cm−1, 1140 cm−1, and 3400 cm−1 were largely decreased alongside decolorization. Electrospray ionization mass chromatography analysis showed that coumaryl alcohol was more abundant and a mass peak corresponding to hydrated coniferyl alcohol was detected after irradiation at 2.9 μm (νO-H) compared to the original lignin. Interestingly, a mass peak corresponding to vanillic acid appeared after irradiation at 7.1 μm (νC=C and νC-C), which was supported by our two-dimensional nuclear magnetic resonance spectroscopy analysis. Therefore, it seems that partial depolymerization of lignin can be induced by IR-FEL irradiation in a wavelength-dependent manner.
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- 2022
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11. Terahertz Imaging for Formalin Fixed Malignant Liver Tumors Using Two-Band Beamline at the Accelerator Facility of Nihon University
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Yusuke Kawashima, Suemitsu Masaaki, Kayo Kuyama, Takeshi Sakai, Yasushi Hayakawa, Takashi Kaneda, and Norihiro Sei
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terahertz imaging ,formalin fixed malignant liver tumor ,two-band beamline ,Accelerator Facility of Nihon University ,Technology ,Engineering (General). Civil engineering (General) ,TA1-2040 ,Biology (General) ,QH301-705.5 ,Physics ,QC1-999 ,Chemistry ,QD1-999 - Abstract
We investigated the transmission characteristics of formalin fixed human liver samples in which normal liver tissue and malignant liver tumor were mixed using terahertz (THz) coherent synchrotron radiation at an infrared free-electron laser (FEL) facility at Nihon University. Infrared-FEL imaging has indicated that the amount of water molecules in the tumor tissue is not different from that in the normal tissue. However, the transmission of the incipient tumor tissue was lower than that of the normal tissue in THz imaging because the tumor tissue contained more water molecular clusters than the normal tissue. The tumor tissue became more permeable owing to the development of fibrous tissue around it. THz imaging will be more useful for discriminating liver tissues by increasing the spatial resolution.
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- 2022
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12. Laboratory Measurement of Millimeter-wave Transitions of 13CH2DOH for Astronomical Use
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Yuki Ohno, Takahiro Oyama, Akemi Tamanai, Shaoshan Zeng, Yoshimasa Watanabe, Riouhei Nakatani, Takeshi Sakai, and Nami Sakai
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Molecular spectroscopy ,Line positions ,Line intensities ,Astrochemistry ,Astrophysics ,QB460-466 - Abstract
Methanol (CH _3 OH) is an abundant interstellar species and is known to be an important precursor of various interstellar complex organic molecules. Among the methanol isotopologues, CH _2 DOH is one of the most abundant isotopologues and it is often used to study the deuterium fractionation of CH _3 OH in interstellar medium. However, the emission lines of CH _2 DOH can sometimes be optically thick, making the derivation of its abundance unreliable. Therefore, observations of its presumably optically thin ^13 C substituted species, ^13 CH _2 DOH, are essential to overcome this issue. In this study, the rotational transitions of ^13 CH _2 DOH have been measured in the millimeter-wave region from 216 GHz to 264 GHz with an emission-type millimeter- and submillimeter-wave spectrometer by using a deuterium and ^13 C enriched sample. The frequency accuracy of measured ^13 CH _2 DOH is less than a few kHz, and the relative line intensity error is less than 10% in most of the frequency range by taking advantage of the wide simultaneous frequency-coverage of the emission-type spectrometer. These results offer a good opportunity to detect ^13 CH _2 DOH in space, which will allow us to study the deuterium fractionation of CH _3 OH in various sources through accurate determination of the CH _2 DOH abundance.
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- 2022
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13. Development of a Self-Reflection Scale for Observers of Mathematics Lesson during Lesson Study
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Takeshi Sakai, Hideyuki Akai, Hiroki Ishizaka, Kazuyuki Tamura, Ban Heng Choy, Yew-Jin Lee, and Hiroaki Ozawa
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Purpose: This study aims to develop a self-reflection scale useful for teachers to improve their skills and to clarify the Japanese teachers' characteristics during mathematics lesson observation (MLO). In MLO, it is important to understand the lesson plan in advance to clarify observation points, and we aim to develop a scale including these points. Design/methodology/approach: Based on the pre-questionnaire survey, nine perspectives and two situations for MLO were extracted. From these, a questionnaire for MLO was created. The results obtained from 161 teachers were examined, and exploratory factor analysis was conducted. ANOVA was conducted to analyze the effect of differences across the duration of teaching experience on the identified factors. Findings: We developed a self-reflection scale consisting of 14 items with three factors: [B1] focus on instructional techniques and evaluation, [B2] focus on proactive problem-solving lesson development and [B3] focus on the mathematical background of the learning content. While duration of teaching experience showed no effect, three factors of the self-reflection scale for MLO showed a significant effect. Further multiple comparisons revealed the degree of focus was [B2]>[B1]>[B3]. Originality/value: Teachers who use this developed scale may grasp the strengths and weaknesses of their own MLO, which leads to self-improvement. The perspectives emphasized in lesson observation are the same when creating lesson plans and implementing lessons, leading to lesson improvement. Furthermore, based on the characteristics of teachers revealed, new training programs regarding MLO can lead to higher-quality lesson studies.
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- 2024
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14. Comprehensive Analysis and Evaluation of Fukushima Daiichi Nuclear Power Station Unit 3
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Takuya Yamashita, Takeshi Honda, Masato Mizokami, Kenichiro Nozaki, Hiroyuki Suzuki, Marco Pellegrini, Takeshi Sakai, Ikken Sato, and Shinya Mizokami
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Nuclear and High Energy Physics ,Nuclear Energy and Engineering ,Condensed Matter Physics - Published
- 2023
15. Estimating trophic guilds based on isotopic niches of demersal fishes, squids and crustaceans in the East China Sea
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Yohei Kawauchi, Takeshi Sakai, Mari Yoda, Aigo Takeshige, Takahito Masubuchi, and Shintaro Gomi
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Ecology ,Aquatic Science ,Oceanography ,Ecology, Evolution, Behavior and Systematics - Abstract
Context Identifying trophic guilds, i.e. species groups having similar trophic niches, is a first step in effective stock and fisheries management with consideration of multiple species interactions or ecosystems. Aims We evaluated isotopic niches by using stable isotope values (δ13C and δ15N) for 53 species, including commercially important demersal fishes, squids and crustaceans, from the continental shelf to the slope of the East China Sea (ECS), to segregate these species into guilds. Methods We inferred the isotopic niche space of each species and community metrics for guilds using Bayesian statistics. Key results Values of δ13C and δ15N showed different isotopic niches among species, reflecting a range of trophic positions and baseline food sources. The 53 species were segregated into 12 guilds on the basis of isotopic niche overlaps. Niche size and evenness differed among guilds; half of the guilds had smaller and less diverse niches than did the others. Conclusions The guilds identified for ECS demersal biota reflected similarities of taxonomy, behaviour, habitat and feeding type; niche size and evenness within each guild might have been influenced by the degree of species interaction. Implications These results provide important ecological information for considering effective multi-species management.
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- 2023
16. A Study on a Model for Improving Mathematics Lessons in Bolivia
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Takeshi, SAKAI, Hiroki, ISHIZAKA, Hideyuki, AKAI, and Moe, HORIBA
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授業改善 ,算数教育 ,草の根プロジェクト ,ボリビア - Abstract
ボリビアの算数教育の改善に向け,2017 年~2019 年にかけて,国際協力機構(JICA)の草の根プロジェクトが,鳴門教育大学によって実施された.本研究では,同プロジェクト開始前・期間中・終了後におけるボリビアの算数教育の変化とプロジェクトにおける研修の関係を考察し,開発途上国における授業改善モデルを開発することを目的とした.図形に関する副教材(ドリル問題)を開発し,その内容に係る教科内容・教授法に係る研修会を行い,学校現場におけるドリル問題の活用をモニタリングし,授業コンクールを行い,グッドプラクティスを対象教師全体で共有した.その結果,ドリル問題を活用することにより数学的背景を授業に取り入れやすくなるとともに,授業の質が変わることにより児童の理解が変わり,それが教師の教材研究に対する意識をも変えることにつながったことが分かった.研修の事前・事後に実施した算数テストの結果からも,教師の教科内容に関する理解,児童の図形に関する知識・技能が向上したことが確認された.同プロジェクトによって「数学的背景に関する研修」を経由しつつ,「数学的概念を形成する授業」が実現できたことから,模範となる算数科授業の実践ができる拠点校を増やし,ボリビアのみならず開発途上国に適した指導者養成研修の枠組みや拠点校型授業研究会のシステムを構築する必要性があることが結論付けられた.
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- 2023
17. Research on Developing Lessons through Global Lesson Study in Science Education
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Kazuyuki, TAMURA, Hiroki, OZAWA, Hideyuki, AKAI, Takeshi, SAKAI, and Hiroki, ISHIZAKA
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シンガポール ,理科教育 ,グローバルレッスンスタディ - Abstract
グローバル人材としての教員の育成を目的に,国際的な授業研究プログラムであるGlobal Lesson Study(GLS)が設計された.算数科における様々な取り組みを通じ,その成果が確認されるとともに,プログラムの有する可能性についても報告されている.そこで本研究では,算数と同様に国際的な取り組みにおいて親和性が高いと考えられる理科について,GLS を通じた,日本とシンガポールの教員のやり取りを分析し,どのような「授業研究のための異文化間能力」が活用されてきたのかを明らかにすることを目的とする.分析を通じ,双方の教員から「授業研究のための異文化間能力」の多くの部分に該当する姿勢が観察されたものの,研究授業前の協議を通じ,新しい教育内容や方法の創造は十分ではなかったことが明らかとなった.また,e-mail による交流では,オンライン会議システムを活用した場合と比べ,重層的なコミュニケーションが実現されず,教育内容・方法に関する双方の違いを理解し合い,さらに新たなものを創造し深めていくことが難しいことが明らかになった.
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- 2023
18. Electroretinograms from Crayfish Compound Eyes Evokedby Mid-infrared Irradiation:Spectral Sensitivity Measurements of the Fast and Late Reactions
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Fumio Shishikura, Heishun Zen, Ken Hayakawa, Yoshimasa Komatsuzaki, Yasushi Hayakawa, Takeshi Sakai, Kyoko Nogami, Yumiko Takahashi, Toshinari Tanaka, Toshiteru Kii, and Hideaki Ohgaki
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General Medicine - Published
- 2023
19. Diffraction-enhanced Imaging of Human Tooth Using Highly Spatial Coherent Parametric X-ray Generated by a Small LINAC System
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Tetsuro Kono, Toshiro Sakae, Yumiko Takahashi, Takeshi Sakai, Kyoko Nogami, Ken Hayakawa, Arata Watanabe, Toshikazu Uchiyama, Yukie Takamura, Yuuya Togashi, Takahiro Ogawa, Toshinari Tanaka, Yasushi Hayakawa, and Hiroyuki Okada
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General Earth and Planetary Sciences ,General Environmental Science - Published
- 2022
20. Estimation of stock characteristics and stock assessment of blackthroat seaperch Doederleinia berycoides in the southwestern Japan Sea
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YASUYUKI KANAMOTO, YUTA YAGI, SORATA TANAKA, MIYUKI KANAIWA, HIRONORI MATSUMOTO, HISAYUKI OTA, MITSUHISA KAWANO, HIROYOSHI TERAKADO, ATSUSHI MICHINE, YOHEI KAWAUCHI, TAKESHI SAKAI, TOSHIKAZU YANO, and MINORU KANAIWA
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Aquatic Science - Published
- 2022
21. Genetic and morphological differentiation among local populations of Japanese top shell Turbo sazae
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TAKASHI YANAGIMOTO, SEINEN CHOW, TAKESHI SAKAI, SHUHEI SAWAYAMA, YORIKO HAYASHI, KAZUYUKI SAITO, TOSHIE WAKABAYASHI, and JUN YAMAMOTO
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Aquatic Science - Published
- 2022
22. Development of seven-beam optics using dielectric lenses for a new 72–116 GHz receiver in the Nobeyama 45 m telescope
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Yasumasa Yamasaki, Yutaka Hasegawa, Sho Yoneyama, Sana Kawashita, Tsubasa Chinen, Sho Masui, Chiaki Nosohara, Heyang Sun, Shuto Dakie, Akira Kameyama, Ikko Fujitomo, Yuma Nishikawa, Hideo Ogawa, Ken’ichi Tatematsu, Atsushi Nishimura, Chieko Miyazawa, Toshikazu Takahashi, Jun Maekawa, Alvaro Gonzalez, Takafumi Kojima, Hiroaki Imada, Keiko Kaneko, Ryo Sakai, Takeshi Sakai, and Toshikazu Onishi
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Space and Planetary Science ,Astronomy and Astrophysics - Abstract
We developed a new seven-beam heterodyne receiver “7BEE” in the 72–116 GHz band for the Nobeyama 45 m telescope to investigate the early stage of star formation by deriving the deuterium fraction of dense cores. The optics for the receiver employs wideband corrugated horns covering the 72–116 GHz band and dielectric lenses to couple the incoming radiation from the antenna on to the feeds. One of the important aspects in the lens design is the anti-reflection (AR) structure to mitigate the reflections on the lens surfaces. Triangular grooves, which gradually change the effective refractive index from air to dielectric, were adopted as a basic AR design since the return loss can be in the order of 20 dB or better. The main goal of this study is to compare the radio frequency (RF) characteristics of the lenses with different patterns and sizes of AR grooving structures. We confirmed that concentric grooves degraded beam symmetry, cross-polarization characteristics, and aperture efficiency due to the birefringence of the grooves, which gave rise to wavefront distortions. Straight grooves of two different gap widths, 1.2 mm and 1.7 mm, were compared and showed similar good performance in terms of beam patterns and noise contribution. However, the latter showed a few percent higher aperture efficiency. Therefore, the straight grooves with 1.7 mm gap width were adopted as the AR structure of our lens.
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- 2023
23. Transformation of Mathematics Classes through Global Lesson Studies
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Takeshi, SAKAI, Hideyuki, AKAI, Kazuyuki, TAMURA, Hiroki, ISHIZAKA, and Hiroaki, OZAWA
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Singapore ,Global Lesson Study ,Japan ,Mathematics - Abstract
In this study, based on the Global Lesson Study (GLS) program, a mathematics lesson study was conducted between teachers in Japan and Singapore, with Singapore as the host school. During the GLS process, the childrenʼs ideas̶diff ered greatly between the two countries̶were shared, and the lesson plans were improved to move toward integrated learning, which could not have been conceived during the in-school research discussions in Singapore, and then, the improvements were refl ected in the lessons. This suggests that GLS is eff ective in improving the teaching of Mathematics.
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- 2022
24. The Potential of the Global Lesson Study as PDCA+E : Verification through a Case Study in Mathematics
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Takeshi, SAKAI, Hideyuki, AKAI, Kazuyuki, TAMURA, Hiroki, ISHIZAKA, and Hiroaki, OZAWA
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PDCA Cycle ,Global Lesson Study ,Extension ,Mathematics - Abstract
In this study, based on the Global Lesson Study (GLS) program, an mathematics lesson study was conducted between teachers in Japan and Singapore, with Japan as the host school. In the process of the GLS, it was confi rmed that the GLS functions as a Plan-Do-Check-Act (PDCA) cycle and that it is eff ective to implement the GLS in a two-year cycle when it is implemented among in-service teachers. As an “Extension”, we proposed the following two points: (1) the possibility of action research by combining survey research and classroom practice, and (2) the possibility of a “GLS package” in the context of international educational cooperation.
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- 2022
25. Changes in qualities and abilities of Japanese teachers through participation in Global Lesson Study on mathematics
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Takeshi Sakai, Hideyuki Akai, Hiroki Ishizaka, Kazuyuki Tamura, Yew-Jin Lee, Ban Heng Choy, and Hiroaki Ozawa
- Subjects
Lesson study ,Teacher perception improvement ,Intercultural competence ,Mathematics education ,Education - Abstract
PurposeThe authors aim to determine the effects of Global Lesson Study (GLS) – a two-year, one-cycle program defined as “international cooperative lesson study through international exchange among teachers using ICT” – on intercultural competence for lesson study based on pre- and post-survey conducted for Japanese teachers.Design/methodology/approachIn accordance with the GLS program, mathematics lesson studies on mathematics between Japanese and Singaporean elementary school teachers were conducted over a two-year period. Questionnaire surveys on intercultural competence for lesson study was conducted using 7-point Likert scale and descriptive questions with Japanese teachers (N = 5). Analysis of Wilcoxon's signed rank test and correlation analysis were conducted.FindingsFollowings are identified as the effects of GLS for Japanese teachers: (1) Japanese participants felt improvement of their competence in areas of attitude, internal outcomes and outward impact. (2) Participating in a GLS led to the improvement of Japanese teachers' qualities and abilities for subject teaching related to mathematics education. (3) Improvement of intercultural competence for lesson study was related to each other, and GLS led to improvement of these competences. (4) It was meaningful to have a two-year period to assimilate and adjust to independent experience of the host and guest.Originality/valueThe GLS led to teacher empowerment among this sample, not only as cooperative research, but also at the individual level of teachers where participants continued to develop lessons based on the GLS learning after study completion. This has important implications for the implementation and dissemination of the GLS.
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- 2022
26. Design and fabrication of stripline type of a broadband quadrature hybrid couplers with transitions of coaxial-microstrip-stripline
- Author
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Satoshi Ono, Tsuyoshi Narita, Sho Masui, Takafumi Kojima, and Takeshi Sakai
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- 2022
27. The ALMA Survey of 70 $\mu \rm m$ Dark High-mass Clumps in Early Stages (ASHES). VII: Chemistry of Embedded Dense Cores
- Author
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Shanghuo Li, Patricio Sanhueza, Xing Lu, Chang Won Lee, Qizhou Zhang, Stefano Bovino, Giovanni Sabatini, Tie Liu, Kee-Tae Kim, Kaho Morii, Daniel Tafoya, Ken’ichi Tatematsu, Takeshi Sakai, Junzhi Wang, Fei Li, Andrea Silva, Natsuko Izumi, and David Allingham
- Subjects
Astrophysics - Solar and Stellar Astrophysics ,Space and Planetary Science ,Astrophysics of Galaxies (astro-ph.GA) ,FOS: Physical sciences ,Astronomy and Astrophysics ,Astrophysics - Astrophysics of Galaxies ,Solar and Stellar Astrophysics (astro-ph.SR) - Abstract
We present a study of chemistry toward 294 dense cores in 12 molecular clumps using the data obtained from the ALMA Survey of 70 $μ\rm m$ dark High-mass clumps in Early Stages (ASHES). We identified 97 protostellar cores and 197 prestellar core candidates based on the detection of outflows and molecular transitions of high upper energy levels ($E_{u}/k > 45$ K). The detection rate of the N$_{2}$D$^{+}$ emission toward the protostellar cores is 38%, which is higher than 9% for the prestellar cores, indicating that N$_{2}$D$^{+}$ does not exclusively trace prestellar cores. The detection rates of the DCO$^{+}$ emission are 35% for the prestellar cores and 49% for the protostellar cores, which are higher than those of N$_{2}$D$^{+}$, implying that DCO$^{+}$ appears more frequently than N$_{2}$D$^{+}$ in both prestellar and protostellar cores. Both N$_{2}$D$^{+}$ and DCO$^{+}$ abundances appear to decrease from the prestellar to protostellar stage. The DCN, C$_{2}$D and $^{13}$CS emission lines are rarely seen in the dense cores of early evolutionary phases. The detection rate of the H$_{2}$CO emission toward dense cores is 52%, three times higher than that of CH$_{3}$OH (17%). In addition, the H$_{2}$CO detection rate, abundance, line intensities, and line widths increase with the core evolutionary status, suggesting that the H$_{2}$CO line emission is sensitive to protostellar activity., Accepted for Publication in ApJ. 36 pages, 15 figures, 5 tables. Table 5 available at https://github.com/ShanghuoLi/70-um-dark-high-mass-clumps
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- 2022
28. The ALMA Survey of 70 {\mu}m Dark High-mass Clumps in Early Stages (ASHES). VI. The core-scale CO-depletion
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Giovanni Sabatini, Stefano Bovino, Patricio Sanhueza, Kaho Morii, Shanghuo Li, Elena Redaelli, Qizhou Zhang, Xing Lu, Siyi Feng, Daniel Tafoya, Natsuko Izumi, Takeshi Sakai, Ken’ichi Tatematsu, and David Allingham
- Subjects
Astrophysics - Solar and Stellar Astrophysics ,Space and Planetary Science ,Astrophysics of Galaxies (astro-ph.GA) ,FOS: Physical sciences ,Astronomy and Astrophysics ,Astrophysics - Astrophysics of Galaxies ,Solar and Stellar Astrophysics (astro-ph.SR) - Abstract
Studying the physical and chemical properties of cold and dense molecular clouds is crucial for the understanding of how stars form. Under the typical conditions of infrared dark clouds, CO is removed from the gas phase and trapped on to the surface of dust grains by the so-called depletion process. This suggests that the CO depletion factor ($f_{\rm D}$) can be a useful chemical indicator for identifying cold and dense regions (i.e., prestellar cores). We have used the 1.3 mm continuum and C$^{18}$O(2-1) data observed at the resolution of $\sim$5000 au in the ALMA Survey of 70 $\mu$m Dark High-mass Clumps in Early Stages (ASHES) to construct averaged maps of $f_{\rm D}$ in twelve clumps to characterise the earliest stages of the high-mass star formation process. The average $f_{\rm D}$ determined for 277 of the 294 ASHES cores follows an unexpected increase from the prestellar to the protostellar stage. If we exclude the temperature effect due to the slight variations in the NH$_3$ kinetic temperature among different cores, we explain this result as a dependence primarily on the average gas density, which increases in cores where protostellar conditions prevail. This shows that $f_{\rm D}$ determined in high-mass star-forming regions at the core scale is insufficient to distinguish among prestellar and protostellar conditions for the individual cores, and should be complemented by information provided by additional tracers. However, we confirm that the clump-averaged $f_{\rm D}$ values correlates with the luminosity-to-mass ratio of each source, which is known to trace the evolution of the star formation process., Comment: 20 pages, 10 figures, 2 tables. Accepted for publication in The Astrophysical Journal (ApJ)
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- 2022
29. LABORATORY MEASUREMENT OF MILLIMETER-WAVE TRANSITIONS OF 13CH2DOH FOR ASTRONOMICAL USE
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Takahiro Oyama, Nami Sakai, takeshi sakai, Riouhei Nakatani, Yoshimasa Watanabe, Shaoshan Zeng, Akemi Tamanai, and Yuki Ohno
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- 2022
30. Digging into the Interior of Hot Cores with ALMA (DIHCA). II. Exploring the Inner Binary (Multiple) System Embedded in G335 MM1 ALMA1
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Fernando A. Olguin, Patricio Sanhueza, Adam Ginsburg, Huei-Ru Vivien Chen, Qizhou Zhang, Shanghuo Li, Xing Lu, and Takeshi Sakai
- Subjects
Astrophysics - Solar and Stellar Astrophysics ,Space and Planetary Science ,Astrophysics of Galaxies (astro-ph.GA) ,FOS: Physical sciences ,Astrophysics::Solar and Stellar Astrophysics ,Astronomy and Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics - Astrophysics of Galaxies ,Solar and Stellar Astrophysics (astro-ph.SR) ,Astrophysics::Galaxy Astrophysics - Abstract
We observed the high-mass protostellar core G335.579-0.272 ALMA1 at ${\sim}200$ au (0.05") resolution with the Atacama Large Millimeter/submillimeter Array (ALMA) at 226 GHz (with a mass sensitivity of $5\sigma=0.2$ M$_\odot$ at 10 K). We discovered that at least a binary system is forming inside this region, with an additional nearby bow-like structure (${\lesssim}1000$ au) that could add an additional member to the stellar system. These three sources are located at the center of the gravitational potential well of the ALMA1 region and the larger MM1 cluster. The emission from CH$_3$OH (and many other tracers) is extended ($>1000$ au), revealing a common envelope toward the binary system. We use CH$_2$CHCN line emission to estimate an inclination angle of the rotation axis of $26^\circ$ with respect to the line of sight based on geometric assumptions and derive a kinematic mass of the primary source (protostar+disk) of 3.0 M$_\odot$ within a radius of 230 au. Using SiO emission, we find that the primary source drives the large scale outflow revealed by previous observations. Precession of the binary system likely produces a change in orientation between the outflow at small scales observed here and large scales observed in previous works. The bow structure may have originated by entrainment of matter into the envelope due to widening or precession of the outflow, or, alternatively, an accretion streamer dominated by the gravity of the central sources. An additional third source, forming due to instabilities in the streamer, cannot be ruled out as a temperature gradient is needed to produce the observed absorption spectra., Comment: 23 pages, 16 figures, 4 tables, 2 appendices. Accepted for publication in ApJ
- Published
- 2022
31. In situ X-ray and acoustic observations of deep seismic faulting upon phase transitions in mantle olivine
- Author
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Tomohiro Ohuchi, Yuji Higo, Yoshinori Tange, Takeshi Sakai, Kohei Matsuda, and Tetsuo Irifune
- Abstract
Activity of deep earthquakes, which increases with depth from ~400 km to a peak at ~600 km and abruptly decreases to zero at 680 km, is enigmatic, because brittle failure is unlikely to occur under the corresponding pressures of 13−24 GPa. It has been suggested that pressure-induced phase transitions of olivine in subducted slabs are responsible for occurrence of the deep earthquakes, based on deformation experiments under pressure. However, most experiments were made using analogue materials of mantle olivine and at pressures below ~5 GPa, which are not applicable directly to the actual slabs. Here we report the results of deformation experiments combined with in situ X-ray observations and acoustic emission measurements on (Mg,Fe)2SiO4 olivine at 11−17 GPa and 860−1250 K, equivalent to the conditions of colder regions of the slabs subducted into the mantle transition region. We find that faulting occurs only at very limited temperatures of 1100−1160 K, accompanied by intense acoustic emissions from both inside and outside of the sample, immediately before the rupture. The formation of lenticular packets filled with nanocrystalline olivine and wadsleyite is confirmed in the recovered sample without faulting, indicating that the faulting is caused by adiabatic shear heating along the weak layer of the connected lenticular packets, where nanocrystalline olivine plays important roles. Our study suggests that the transformational faulting occurs on the isothermal surface of the metastable olivine wedge in subducted slabs, leading to deep earthquakes in limited regions and depth range.
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- 2022
32. Chemical and Physical Characterization of the Isolated Protostellar Source CB68: FAUST IV
- Author
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Muneaki Imai, Yoko Oya, Brian Svoboda, Hauyu Baobab Liu, Bertrand Lefloch, Serena Viti, Yichen Zhang, Cecilia Ceccarelli, Claudio Codella, Claire J. Chandler, Nami Sakai, Yuri Aikawa, Felipe O. Alves, Nadia Balucani, Eleonora Bianchi, Mathilde Bouvier, Gemma Busquet, Paola Caselli, Emmanuel Caux, Steven Charnley, Spandan Choudhury, Nicolas Cuello, Marta De Simone, Francois Dulieu, Aurora Durán, Lucy Evans, Cécile Favre, Davide Fedele, Siyi Feng, Francesco Fontani, Logan Francis, Tetsuya Hama, Tomoyuki Hanawa, Eric Herbst, Shingo Hirano, Tomoya Hirota, Andrea Isella, Izaskun Jímenez-Serra, Doug Johnstone, Claudine Kahane, Romane Le Gal, Laurent Loinard, Ana López-Sepulcre, Luke T. Maud, María José Maureira, Francois Menard, Seyma Mercimek, Anna Miotello, George Moellenbrock, Shoji Mori, Nadia M. Murillo, Riouhei Nakatani, Hideko Nomura, Yasuhiro Oba, Ross O’Donoghue, Satoshi Ohashi, Yuki Okoda, Juan Ospina-Zamudio, Jaime Pineda, Linda Podio, Albert Rimola, Takeshi Sakai, Dominique Segura-Cox, Yancy Shirley, Vianney Taquet, Leonardo Testi, Charlotte Vastel, Naoki Watanabe, Yoshimasa Watanabe, Arezu Witzel, Ci Xue, Bo Zhao, Satoshi Yamamoto, Academia Sinica Institute of Astronomy and Astrophysics (ASIAA), Academia Sinica, Institut de Planétologie et d'Astrophysique de Grenoble (IPAG), Centre National d'Études Spatiales [Toulouse] (CNES)-Observatoire des Sciences de l'Univers de Grenoble (OSUG ), Institut national des sciences de l'Univers (INSU - CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Université Grenoble Alpes (UGA)-Météo-France -Institut national des sciences de l'Univers (INSU - CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Université Grenoble Alpes (UGA)-Météo-France, RIKEN - Institute of Physical and Chemical Research [Japon] (RIKEN), Department of Astronomy [Tokyo], The University of Tokyo (UTokyo), Max Planck Institute for Extraterrestrial Physics (MPE), Max-Planck-Gesellschaft, Università degli Studi di Perugia = University of Perugia (UNIPG), Max-Planck-Institut für Extraterrestrische Physik (MPE), Centre National d'Études Spatiales [Toulouse] (CNES), Institut de recherche en astrophysique et planétologie (IRAP), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Japan Science and Technology Agency, European Research Council, European Commission, Agencia Estatal de Investigación (España), National Science Foundation (US), Ministerio de Ciencia, Innovación y Universidades (España), and Ministry of Education, Culture, Sports, Science and Technology (Japan)
- Subjects
[SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR] ,FOS: Physical sciences ,Astronomy and Astrophysics ,Astrophysics - Astrophysics of Galaxies ,Astrophysics - Solar and Stellar Astrophysics ,Space and Planetary Science ,Astrophysics of Galaxies (astro-ph.GA) ,Star Formation ,Circumstellar Disks ,Interstellar Molecules ,Solar and Stellar Astrophysics (astro-ph.SR) - Abstract
Imai et al., The chemical diversity of low-mass protostellar sources has so far been recognized, and environmental effects are invoked as its origin. In this context, observations of isolated protostellar sources without the influence of nearby objects are of particular importance. Here, we report the chemical and physical structures of the low-mass Class 0 protostellar source IRAS 16544−1604 in the Bok globule CB 68, based on 1.3 mm Atacama Large Millimeter/submillimeter Array observations at a spatial resolution of ∼70 au that were conducted as part of the large program FAUST. Three interstellar saturated complex organic molecules (iCOMs), CH3OH, HCOOCH3, and CH3OCH3, are detected toward the protostar. The rotation temperature and the emitting region size for CH3OH are derived to be 131 ± 11 K and ∼10 au, respectively. The detection of iCOMs in close proximity to the protostar indicates that CB 68 harbors a hot corino. The kinematic structure of the C18O, CH3OH, and OCS lines is explained by an infalling–rotating envelope model, and the protostellar mass and the radius of the centrifugal barrier are estimated to be 0.08–0.30 M⊙ and, This paper makes use of the following ALMA data: ADS/JAO.ALMA#2016.1.01376.S. ALMA is a partnership of ESO (representing its member states), NSF (USA) and NINS (Japan), together with NRC (Canada), NSC and ASIAA (Taiwan), and KASI (Republic of Korea), in cooperation with the Republic of Chile. The Joint ALMA Observatory is operated by ESO, AUI/NRAO and NAOJ. The authors acknowledge financial support from JSPS and MAEE under the Japan–France Integrated Action Program (SAKURA: 25765VC). D.J. is supported by NRC Canada and by an NSERC Discovery Grant. E.B. and G.B. acknowledge funding from the European Research Council under the European Union's Horizon 2020 research and innovation program, for the project "The Dawn of Organic Chemistry," grant agreement No. 741002. G.B. acknowledges support from the PID2020-117710GB-I00 grant funded by MCIN/AEI/10.13039/501100011033 and from the Unit of Excellence María de Maeztu 2020–2023 award to the Institute of Cosmos Sciences (CEX2019-00918-M). I.J.-S. has received partial support from the Spanish State Research Agency (AEI) through project Nos. PID2019-105552RB-C41 and MDM-2017-0737 Unidad de Excelencia "Maria de Maeztu" - Centro de Astrobiologia (CSIC-INTA). This study is supported by grants-in-aid from the Ministry of Education, Culture, Sports, Science, and Technology of Japan (18H05222, 18J11010, 19H05069, 19K14753, and 21K13954).
- Published
- 2022
33. Erratum: 'The ALMA Survey of 70micron dark High-mass Clumps in Early Stages (ASHES). IV. Star formation signatures in G023.477' (2021, ApJ, 923, 147)
- Author
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Kaho Morii, Patricio Sanhueza, Fumitaka Nakamura, James M. Jackson, Shanghuo Li, Henrik Beuther, Qizhou Zhang, Siyi Feng, Daniel Tafoya, Andrés E. Guzmán, Natsuko Izumi, Takeshi Sakai, Xing Lu, Ken’ichi Tatematsu, Satoshi Ohashi, Andrea Silva, Fernando A. Olguin, and Yanett Contreras
- Subjects
Space and Planetary Science ,Astronomy and Astrophysics - Abstract
This is a correction for 2021 ApJ 923 147DOI 10.3847/1538-4357/ac2365
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- 2022
34. In situ X-ray and acoustic observations of deep seismic faulting upon phase transitions in olivine
- Author
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Tomohiro Ohuchi, Yuji Higo, Yoshinori Tange, Takeshi Sakai, Kohei Matsuda, and Tetsuo Irifune
- Subjects
Multidisciplinary ,General Physics and Astronomy ,General Chemistry ,General Biochemistry, Genetics and Molecular Biology - Abstract
The activity of deep-focus earthquakes, which increases with depth from ~400 km to a peak at ~600 km, is enigmatic, because conventional brittle failure is unlikely to occur at elevated pressures. It becomes increasingly clear that pressure-induced phase transitions of olivine are responsible for the occurrence of the earthquakes, based on deformation experiments under pressure. However, many such experiments were made using analogue materials and those on mantle olivine are required to verify the hypotheses developed by these studies. Here we report the results of deformation experiments on (Mg,Fe)2SiO4 olivine at 11−17 GPa and 860−1350 K, equivalent to the conditions of the slabs subducted into the mantle transition zone. We find that throughgoing faulting occurs only at very limited temperatures of 1100−1160 K, accompanied by intense acoustic emissions at the onset of rupture. Fault sliding aided by shear heating occurs along a weak layer, which is formed via linking-up of lenticular packets filled with nanocrystalline olivine and wadsleyite. Our study suggests that transformational faulting occurs on the isothermal surface of the metastable olivine wedge in slabs, leading to deep-focus earthquakes in limited regions and depth range.
- Published
- 2021
35. The ALMA Survey of 70 $\mu$m Dark High-mass Clumps in Early Stages (ASHES). V. Deuterated Molecules in the 70 $\mu$m dark IRDC G14.492-00.139
- Author
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Takeshi Sakai, Patricio Sanhueza, Kenji Furuya, Ken’ichi Tatematsu, Shanghuo Li, Yuri Aikawa, Xing Lu, Qizhou Zhang, Kaho Morii, Fumitaka Nakamura, Hideaki Takemura, Natsuko Izumi, Tomoya Hirota, Andrea Silva, Andres E. Guzman, Nami Sakai, and Satoshi Yamamoto
- Subjects
Astrophysics - Solar and Stellar Astrophysics ,Space and Planetary Science ,Astronomy and Astrophysics ,Astrophysics - Astrophysics of Galaxies - Abstract
We have observed the 70 $\mu$m dark infrared dark cloud (IRDC) G14.492-00.139 in the N$_2$D$^+$ $J$=3--2, DCO$^+$ $J$=3--2, DCN $J$=3--2, and C$^{18}$O $J$=2--1 lines, using the Atacama Large Millimeter/submillimeter Array (ALMA) as part of the ALMA Survey of 70 $\mu$m Dark High-mass Clumps in Early Stages (ASHES). We find that the spatial distribution is different among the observed emission from the deuterated molecular lines. The N$_2$D$^+$ emission traces relatively quiescent regions, while both the DCO$^+$ and DCN emission emanates mainly from regions with signs of active star-formation. In addition, the DCO$^+$/N$_2$D$^+$ ratio is found to be lower in several dense cores than in starless cores embedded in low-mass star-forming regions. By comparing the observational results with chemical model calculations, we discuss the origin of the low DCO$^+$/N$_2$D$^+$ ratio in this IRDC clump. The low DCO$^+$/N$_2$D$^+$ ratio can be explained if the temperature of the dense cores is in the range between the sublimation temperature of N$_2$ ($\sim$20 K) and CO ($\sim$25 K). The results suggest that the dense cores in G14.492-00.139 are warmer and denser than the dense cores in low-mass star-forming regions., Comment: accepted for publication in ApJ
- Published
- 2021
36. Growth, reproduction, and feeding habits of striped bonito, Sarda orientalis, in the East China Sea
- Author
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Seiji Ohshimo, Taketoshi Kodama, Tatsuya Sakamoto, Takeshi Sakai, and Mami Saito
- Subjects
Ecology ,Animal Science and Zoology ,Aquatic Science ,Ecology, Evolution, Behavior and Systematics - Published
- 2022
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