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珊瑚礁の高生産性を支えるメカニズム : 独立栄養および混合栄養条件で飼育した刺胞動物（サンゴ・イソギンチャク）に含まれるアミノ酸の安定同位体比からの評価 [論文内容及び審査の要旨]
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ヘリウム同位体イメージングによる炭素質コンドライト中の太陽風由来ヘリウム微細分布の解明
No full textSolar wind (SW) is preserved in meteorites as abundant noble gases derived from SW implantation. Noble gases are generally present in extremely low abundances in solid matter, making it possible to identify noble gases that are secondarily introduced by SW implantation. Since the projected range of typical SW particles into solid matter is less than 100 nm, SW-implantation occurs only when the grains reside in the uppermost surface of airless bodies. The SW irradiation duration is a key indicator of the timescales of geological processes on an asteroid. Furthermore, the distribution of SW noble gases in meteorites provide new insights into the mixing and sedimentation processes of the surface regolith on their parent body. In this thesis, I investigated the SW-4He distribution in a solar-gas-rich carbonaceous chondrite. This thesis consists of mainly two chapters as follows. EVIDENCE OF SOLAR WIND IRRADIATION ON INDIVIDUAL MINERAL GRAINS: I performed in situ 4He isotope imaging of individual mineral grains in the CR2 chondrite Northwest Africa 801 (NWA 801) using time-of-flight secondary neutral mass spectrometry with strong-field post-ionization. 4He+ signals were detected along the surfaces of individual mineral grains of Fe-Ni metal ferrihydrite, olivine, pyroxene, and troilite. The high 4He concentrations along the surfaces indicate implantation of SW into the individual mineral grains. I determined the SW-4He fluence of eight individual mineral grains from the line profiles across the grain boundaries. SW-4He fluence ranged from 2.7 × 1016 to 5.8 × 1017 atoms cm−2. I calculated the SW irradiation durations from these fluences. Assuming an irradiation occurred at 4 astronomical units, the durations translated to be between 3.8 and 82 kyr. These durations correspond to the residence time of individual mineral grains on the parent body surface. The variation in residence time for the individual mineral grains suggests variable processes for local mixing and burial on the parent body and provides insights into the gardening rate driven by small-scale impact mixing processes on the parent body. VISUALIZATION OF SEDIMENTARY STRUCTURE OF AN ASTEROIDAL REGOLITH IN A CARBONACEOUS CHONDRITE: By modifying the analysis program within the LIMAS operating system, I achieved 4He imaging over an area of 100 × 150 μm, which is about 10 times larger than the previous analysis conditions. Improved in situ 4He imaging technique elucidated the relationship between the heterogeneity of SW-4He and petrological characteristics in the NWA 801 The SW-4He-bearing mineral grains are predominantly distributed within the coarse grain-rich matrix. In contrast, the fine grain-rich matrix, composed of 1–5 μm grains and fine-grained groundmass, occurs as accessory rims around chondrules and an isolated olivine grain and also appears as scattered lumps ranging from several tens to hundreds of micrometers in size. No detectable 4He was observed in the fine grain-rich matrix. Based on the similarities in occurrence, the fine grain-rich matrix observed in this study is thought to be the same material as fine-grained rims (FGRs). The partial preservation of FGRs along with the intact state of many chondrules, suggests that the daily impacts associated with gardening process primarily caused the disaggregation of loosely bound components, without sufficient energy to fracture chondrules. The heterogeneous distribution of SW-4He originated from low-energy impacts that caused the disaggregation of loosely bound components, which were the main processes of regolith gardening on the parent body of NWA 801. The proportions of SW-4He-bearing grains in opaque minerals and silicates are nearly identical (~20%), suggesting that SW irradiation occurred irrespective of mineral type, affecting both opaque minerals and silicates. If the regolith preserved in the meteorite reflects the global surface characteristics of the NWA 801 parent body, the proportion of 4He-bearing grains implies that approximately 20% of the unconsolidated surface layer was exposed to SW for a sufficiently long duration to accumulate detectable SW-4He, while the remaining 80% consisted of “immature regolith” that experienced minimal SW exposure (likely less than a few hundred years). The surface of the parent body of NWA 801 was likely composed largely of immature regolith, similar to present-day asteroids. High-resolution 4He isotope imaging revealed the distribution of SW-4He in the NWA 801 meteorite. The distribution of SW-4He in individual mineral grains is direct evidence of SW implantation on meteoritic grains. Quantification of SW-4He fluence of the individual mineral grains and the comprehensive investigation of the distribution of SW-4He in the interstitial matrix elucidate that gardening, which has sufficient energy to bury the SW-⁴He-enriched layer to a depth of several millimeters to centimeters, typically occurs on the parent body with a frequency of about ten thousand years
Singlet/triplet Josephson junction on a substrate
No full textWe discuss the Josephson effect in a spin-singlet superconductor/spin-triplet superconductor junction fabricated on a substrate. Due to inversion symmetry breaking on top of the substrate, Rashba spin-orbit interaction works on electrons in the superconductors. As a result, spin-triplet (spin-singlet) Cooper pairs are induced in a spin-singlet (spin-triplet) superconductor. The presence of such induced Cooper pairs enables the lowest-order Josephson coupling between the two superconductors. Based on the theoretical results and recent experimental findings [X. Xu et al., Phys. Rev. Lett. 132, 056001 (2024)], we analyze the pair potential of 3-Bi2Pd
Philosophy, System and Practices of Intercultural Education : A study on the educational system and school practices for a multicultural coexistence in Italy
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AIが非ヒト動物に与える有益・有害な影響の検討
No full text本稿では、現在および将来ありうる人工知能（AI）が、非ヒト動物に対して、どのように有益・有害な影響を与えるかを検討する。本稿ではまず、私達が非ヒト動物に与える影響について、Coghlan and Parker（2023）の提示する枠組みを紹介する。次にこの分類枠組みに従って議論しているCoghlan and Parker（2023）およびBossert （2023）を元に、かれらの研究以降の研究も踏まえ、AI が非ヒト動物に与える影響について議論する。まず分類枠組みについて、Coghlan and Parker（2023）はFraser and MacRae（2011）の研究をもとに、私達が非ヒト動物に与える影響を4つのタイプに分類している：（1）意図的かつ違法な影響、（2）意図的かつ合法な影響、（3）非意図的かつ直接的な影響、（4）非意図的かつ間接的影響。意図的な影響とは、人間が意図して非ヒト動物に影響を与えることを指す。非意図的な影響は、人間が非ヒト動物に影響を与えることを意図してないが、結果として影響が生じていることを指す。直接的影響は私達（やAI）が非ヒト動物に直接的に影響を加えている場合を指し、間接的影響は、何らかの別の影響を経由して非ヒト動物に影響を及ぼす場合を指す。Coghlan and Parker（2023）とBossert（2023）はこの分類枠組みに従い、AI が非ヒト動物に及ぼす影響について、有害性の観点と有益性の観点からそれぞれ議論している。本稿では、上記の枠組みにしたがい、考えられうる有害・有益な影響について検討する。またAI が非ヒト動物にとって有益になるために私達（AI 研究者、倫理学者、市民）が何をすべきかを検討する。This paper examines how artificial intelligence (AI), both now and in the future, can have beneficial and harmful impacts on nonhuman animals. First, we introduce the framework Coghlan and Parker (2023) presented regarding our impacts on nonhuman animals. Then, based on this framework and drawing from Coghlan and Parker (2023) and Bossert (2023), as well as subsequent research, we discuss the impacts of AI on nonhuman animals. Regarding the classification framework, Coghlan and Parker (2023), based on the work of Fraser and MacRae (2011), categorize the impacts we have on nonhuman animals into four types: (1) intentional and illegal impacts, (2) intentional and legal impacts, (3) unintentional and direct impacts, and (4) unintentional and indirect impacts. Intentional impacts refer to cases where humans intentionally affect nonhuman animals. Unintentional impacts occur when humans do not intend to affect nonhuman animals, but their actions result in an impact. Direct impacts refer to cases where we (or AI) directly affect nonhuman animals, while indirect impacts refer to those that occur via some other intermediary impact. Following this framework, Coghlan and Parker (2023) and Bossert (2023) discuss the impacts of AI on nonhuman animals from the perspectives of both harm and benefit. This paper will examine the abovementioned framework's potential harmful and beneficial impacts. Furthermore, we will consider what we (AI researchers, ethicists, and citizens) should do to ensure that AI benefits nonhuman animals
Maximal surfaces in the Lorentzian Heisenberg group
No full textThe 3-dimensional Heisenberg group can be equipped with three different types of left-invariant Lorentzian metric, according to whether the center of the Lie algebra is spacelike, timelike or null. Using the second of these types, we study spacelike surfaces of mean curvature zero. These surfaces with singularities are associated with harmonic maps into the 2-sphere. We show that the generic singularities are cuspidal edge, swallowtail and cuspidal cross-cap. We also give the loop group construction for these surfaces, and the criteria on the loop group potentials for the different generic singularities. Lastly, we solve the Cauchy problem for harmonic maps into the 2-sphere using loop groups, and use this to give a geometric characterisation of the singularities. We use these results to prove that a regular spacelike maximal disc with null boundary must have at least two cuspidal cross-cap singularities on the boundary
