Mineralogical study of some Antarctic monomict eucrites including Yamato-74356: A unique rock containing recrystallized clastic matrix

We studied the thermal and impact history of four Yamato Antarctic monomict eucrites, Yamato (Y)-74356,Y-791186,Y-792510,and Y-82037,by mineralogical techniques. Although the mineral chemistry of Y-74356 is typical of monomict eucrites, it contains a recrystallized clastic matrix similar to that of some lunar granulitic breccias. Y-74356 experienced shock brecciation during a major thermal event. In contrast, Y-791186 and Y-792510 have pyroxenes of the highest metamorphic degree but the clastic matrices are weakly recrystallized, i. e., these two rocks were not extensively metamorphosed after breccia assembly. This indicates that the process that caused brecciation is distinct from the major thermal event. Y-82037 is a coarse-grained, unbrecciated ordinary eucrite, indicating that it was not affected by the brecciation event, except for the presence of a granoblastic portion in part of the pyroxene crystals. We deduce that the thermal metamorphism that formed ordinary eucrites took place on a longer time scale and at a lower temperature than that which formed some lunar granulitic breccias. The precursors of these ordinary eucrites have suffered from smaller scale brecciation events than those of the lunar granulitic breccias (metamorphic polymict breccias). It is unlikely that there were comparably large cratering events on the small HED parent body to cause the strong thermal metamorphism. The thermal events may have taken place at a very early stage of the evolution of the primary crust of the HED parent body

Petrofabric analysis of acapulcoites and lodranites

第6回極域科学シンポジウム[OA] 南極隕石11月16日（月）　国立国語研究所 2階 講

Mineralogical study of some brecciated Antarctic eucrites

In order to obtain better understanding of the entire range of Antarctic brecciated eucrites and impact and thermal history of the HED-parent body, we studied brecciated Antarctic eucrites : Y-82202,Y-82210,Y-793548,and Y-793570 mineralogically and petrographically. Y-793548,Y-82210,and Y-793570 are nearly monomict breccias with clasts components of rapidly cooled materials and minor slowly cooled pyroxenes (e. g., Juvinastype). Y-82202 is a monomict breccia penetrated by glassy shock melt veins. We suggest that the polished thin sections of the five eucrites presently available belong to a single suite which contains mostly quickly cooled varieties of eucrites similar to those in Pasamonte or in the Y-74159-type polymict eucrites, but more slowly cooled varieties such as ordinary eucrites or cumulate eucrites are scarce in these sections. On the basis of geological setting of HED parent body, we envision that these eucrites may have been located in the shallow ejecta blanket of the HED-parent body, judging from the high mixing ratio of unequilibrated clasts and low degree of equilibration of pyroxene

A Study of Screen Constitution and proper Character Size on VDT Text Reading According to the Developmental Grade

本研究は、人間の視覚認知特性のための基礎的研究として、VDT作業において重要な意味を持つ人間が見やすい画面構成、適正な文字の大きさが学齢によって違うことを検証し、併せて学校などにおける情報教育のための基礎的な研究として、学齢発達段階ごとの見やすいと感じる画面条件の違いを比較する実験を行った。すなわち小学生・中学生・高校生・大学生を被験者として、画面構成条件の違いに応じた、VDTに適した文字サイズと画面構成条件を調べた。その結果を統計分析した結果、小学生から大学生まで多学年にわたる、学齢別の至適文字サイズの特性曲線を導出した。そして子供が見やすいと感じる文字と画面の条件を求める学年別比較を通して、学齢別のVDT視認特性について考察した。The primary objective of the study was to determine the optical screen configuration for the first-year junior high school students studying the fundamentals of information science and technology. A study of easy-to-write screen configurations to be used when reading Japanese text in VDT was one of the most important factors for the fundamentals of information science and technology class. I studied the reading performance of first-year junior high school students as they write textbooks while VDT conditions such as font size, screen brightness, text and background color were altered. I also compared the performance of first-year junior high school students with the results of university students. The results were as follows: 1) the opitical screen configuration for first-year junior high school students were somewhat different than that for university students'. 2) the optical letter size for first-year junior high school students was determined to be 18points which was larger than that what was required for the adults to be 14points, 3) ideally each students should be able to adjust his or her own screen configuration in order to meet their individual needs. However, if default screen conditions for writing were to be used in first-year junior high school classrooms, the optical background color was white, the text black, the brightness-contrast high, the letter style Minchotai, with continuous sentences in a 18 font

Comment on "The origin of eucrites, diogenites, and olivine diogenites: magma ocean crystallization and shallow magma processes on Vesta" by B.E. Mandler and L.T. Elkins-Tanton

International audienceMandler and Elkins-Tanton () recently proposed an upgraded magma ocean model for the differentiation history of the giant asteroid 4 Vesta. They show that a combination of both equilibrium crystallization and fractional crystallization processes can reproduce the major element compositions of eucritic melts and broadly the range of mineral compositions observed in diogenites. They assert that their model accounts for all the howardites, eucrites, and diogenites (HEDs), and use it to predict the crustal thickness and the proportions of the various lithologies. Here, we show that their model fails to explain the trace element diversity of the diogenites, contrary to their claim. The diversity of the heavy REE enrichment exhibited by the orthopyroxenes in diogenites is inconsistent with crystallization of these cumulates in either shallow magma chambers replenished by melts from a magma ocean or in a magma ocean. Thus, proportions of the various HED lithologies and the crustal thickness predicted from this model are not necessarily valid

Compressible bag model and the phase structure

The phase structure of hadrons and quark-gluon plasma is investigated by two types of equation of hadron state, namely ideal hadron gas model and the compressible bag model. It is pointed out that, while the ideal gas model produces unrealistic extra hadron phase, the compressible bag model gives an expected and reasonable phase diagram even if rich hadron spectrum is taken into account.Comment: 14 pages, 11 figures, LaTeX2

Micro-Raman spectroscopic analysis of darkened olivine in Martian meteorites

第6回極域科学シンポジウム[OA] 南極隕石11月17日（火）　国立国語研究所 2階 講

High Pressure Phases found in Yamato 790729.

第2回極域科学シンポジウム/第34回南極隕石シンポジウム 11月17日（木） 国立国語研究所 2階講