Type 3 chondrites are subdivided into 3.0–3.9. Subtype 3.0 chondrites nearly preserve all of their primitive features. Many criteria have been proposed to distinguish such primitive chondrites. Here, ...we compiled mineral data and reconsider the petrologic classification criteria for subtype 3.0. Chondrites are classified into subtypes by the minor element distribution of olivine and textural and chemical features of Fe‐Ni metal. The Si4O8 and MgO components of feldspar also distinguish subtype 3.0 from subtypes ≥3.1. Other features, such as the occurrence of near pure chromite, are also indicators of subtype 3.0. It is difficult to distinguish between subtypes 3.0 and ≤2.9 based on mineral chemistry. Therefore, we propose the following criteria to distinguish between subtypes 3.0 and ≤2.9. In type 3.0 chondrites, major silicate (olivine, pyroxene, and plagioclase), oxide, metal, and sulfide minerals do not show aqueous alteration features. Melilite, anorthite, and glass show no or mild aqueous alteration features. Subtype 3.0 has not been identified in all chondrite groups. The absence of subtype 3.0 from some groups mainly reflects differences in the degrees of secondary parent body processes among the chondrite groups.
Freestanding GaN crystals were fabricated by hydride vapor phase epitaxy using a random-islands facet-initiated epitaxial overgrowth technique. In this method, small micrometer sized GaN islands were ...firstly deposited on a TiC buffer layer on a sapphire substrate. Successive three-dimensional growth of GaN was controlled to a thickness of a few hundred micrometers on the buffer layer. Finally, a thick GaN layer was grown and high quality freestanding GaN crystals (dislocation density: <3×106cm−2, radius of curvature: >5m) were obtained by self-separation from the sapphire substrate. It was found that the dislocation density was drastically reduced in the initial growth stage of this method by the appearance of sidewall facets. Depth profiles of the residual strain in the freestanding GaN substrates have been successfully measured by a novel method employing cross-sectional micro-reflectance spectroscopy. It was found that the intrinsic strain, the driving force of wafer bending, can be greatly reduced by the introduction of three-dimensional growth in the initial growth stage.
All mesosiderites previously reported were subjected to thermal metamorphism and/or partial melting on the parent body. Therefore, their primordial features have been mostly lost. Here, we report ...detailed petrological and mineralogical features on a mesosiderite, Northwest Africa (NWA) 1878. This meteorite comprises silicate lithology and aggregates of small spheroidal Fe‐Ni metal grains. Silicate lithology typically shows igneous texture without recrystallization features, and mainly consists of low‐Ca pyroxene and plagioclase. Pyroxenes often show normal zoning. Exsolution lamella of augite is rarely noticed and very thin in width, compared with other mesosiderites. A few magnesian olivine grains are encountered without typical corona texture around them. They are not equilibrated with pyroxene on a large scale. Plagioclase shows a wide compositional range. These results show that NWA 1878 hardly experienced thermal metamorphism, distinguished from mesosiderites of subgroups 1–4. Therefore, we propose that this is classified as subgroup 0 mesosiderite. Nevertheless, NWA 1878 was locally subjected to secondary reactions, such as weak reduction of pyroxene and Fe‐Mg diffusion between olivine and pyroxene, on the parent body.
Abstract
Superconducting parametrons in the single-photon Kerr regime, also called KPOs, have been attracting increasing attention in terms of their applications to quantum annealing and universal ...quantum computation. It is of practical importance to obtain information of superconducting parametrons operating under an oscillating pump field. Spectroscopy can provide information of a superconducting parametron under examination, such as energy level structure, and also useful information for calibration of the pump field. We theoretically study the reflection spectroscopy of superconducting parametrons, and develop a method to obtain the reflection coefficient. We present formulae of the reflection coefficient, the nominal external and the internal decay rates, and examine the obtained spectra. It is shown that the difference of the populations of energy levels manifests itself as a dip or peak in the amplitude of the reflection coefficient, and one can directly extract the coupling strength between the energy levels by measuring the nominal decay rates when the pump field is sufficiently large.
In general, surface of additively manufactured (AMed) metal products has large roughness due to arrangement of bead shapes, and surface irregularities such as spatter and cavity. Furthermore, surface ...elemental composition of AMed products may be changed from that of metal powder. In this study, efficient surface smoothing and repairing of AMed metal products by large-area electron beam irradiation were experimentally investigated. Experimental results show that spatter and cavity can be completely removed and surface roughness significantly reduces. Elemental composition of AMed surface can be also changed to that of original metal powder due to the removal of oxidized surface.
Most carbonaceous (C) chondrites are classified into eight major groups: CI, CM, CO, CV, CK, CR, CH, and CB. However, some are ungrouped. We studied two such chondrites, Asuka (A)‐9003 and A 09535. ...The abundance of chondrules and matrix and chondrule sizes in these meteorites are similar to those in ordinary chondrites and unlike any known carbonaceous chondrite group. In contrast, they contain 4–6 vol% of refractory inclusions and have oxygen isotopic compositions within the range of CO and CV chondrites. Therefore, A‐9003 and A 09535 are classified as C chondrites. Petrologic subtypes of A‐9003 and A 09535 are 3.2. All these features closely resemble those of another ungrouped chondrite, Yamato (Y)‐82094, and differ from those of any C chondrites reported by now. A‐9003, A 09535, and Y‐82094 likely represent a new type of C chondrite. We provisionally call them CA chondrite after Asuka in Antarctica. Our study suggests a wider range of formation conditions for C chondrites than currently recorded by the major C chondrite groups.
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