Condition for the formation of the compound chondrules in the solar nebula

The conditions for compound chondrule formation described by J. L. GOODING and K. KEIL (Meteoritics, 16,17,1981) are reexamined using the criterion of gravitational instabilities (M. SEKIYA, Prog. Theor. Phys., 69,1116,1983). If a compound chondrule was formed by collisional sticking of a plastic particle with a solid or another plastic particle, the following conclusions are derived : (1) Chondrules were formed after the settling of dust particles had progressed and the number density of dust particles had increased by several orders of magnitude. (2) To reproduce the observed ratio of the compound chondrules to all the chondrules, collisional velocities of pre-chondrule particles must have been larger than about 1.6m s^, and the Weber number for the collision of molten pre-chondrule particles must have been larger than about 40,if we assume that the chondrule formation occurred in the asteroid region in the stage where dust particles were floating in the solar nebula. In this case, collisional sticking would be difficult. If sticking is impossible, then other formation mechanisms for the compound chondrules must be considered (e. g. J. T. WASSON et al., Geochim. Cosmochim. Acta, 59,1847,1995). (3) If chondrules were formed in the inner regions of the solar nebula, the lower limits for the relative velocities of the prechondrule particles would be reduced

Experimental Studies on the Elastic-Plastic Behavior of Braced Frames under Repeated Horizontal Loading. Part 1 Experiments of Braces with an H-shaped Cross Section in a Frame

An experimental study is conducted to obtain the hysteretic characteristics of the brace itself in a braced frame under repeated loading. Braces with an H-shaped cross section are tested in a single or a double bracing system. The effects of the slenderness ratio, the buckling plane and the local buckling are investigated. Furthermore, the fundamental properties of a brace for the formulation of the hysteretic characteristics under repeated loading are extracted

Universal low-temperature properties of quantum and classical ferromagnetic chains

We identify the critical theory controlling the universal, low temperature, macroscopic properties of both quantum and classical ferromagnetic chains. The theory is the quantum mechanics of a single rotor. The mapping leads to an efficient method for computing scaling functions to high accuracy.Comment: 4 pages, 2 tables and 3 Postscript figure

Clinical Significance of Autoantibodies in Primary Biliary Cirrhosis

Antimitochondrial, anti-gp210, anti-sp100, and anticentromere antibodies are specifically detected in primary biliary cirrhosis (PBC). In clinical practice, they are useful for the diagnosis of PBC or for evaluating disease severity, clinical phenotype, and long-term outcome. In the typical or classical form of PBC which shows slow progressive loss of small bile ducts with a parallel increase in liver fibrosis, anti-gp210 antibodies are a strong risk factor for progression to jaundice and hepatic failure, whereas the presence of anticentromere antibodies is a risk factor for progression to cirrhosis and portal hypertension. Of note, the autoimmune repertoire, which is established during the early stage of the disease process, can influence the clinical phenotype and the long-term prognosis of PBC. Because the natural course of PBC is being altered by treatment with ursodeoxycholic acid, the clinical significance of these PBC-specific autoantibodies awaits re-evaluation in various ethnicities

Cosmic-ray exposure age and heliocentric distance of the parent body of H chondrites Yamato-75029 and Tsukuba

Many small pieces of the H chondrites Yamato (Y-) 75029 and Tsukuba were investigated to characterize signatures of light noble gases. These meteorites contain large amounts of solar gases as well as cosmogenic ones. A simple regolith exposure model was developed in order to explain the correlations among solar ^Ne and ^Ar and cosmogenic ^Ne concentrations. Based on the regolith model, the parent body exposure ages, heliocentric distances, and space exposure ages of the two meteorites were calculated. The parent body exposure ages were more than 5.5Ma and 11.8Ma for Y-75029 and Tsukuba, respectively. The heliocentric distances were 2.2±^_ AU and 4.2±^_ AU for Y-75029 and Tsukuba, respectively. The space exposure age of Y-75029 was 5.2-5.8Ma, whereas that of Tsukuba was 8.1±0.6Ma. It has been suggested that the parent bodies of H chondrites are S-type asteroids with orbits that range from 2 to 3.5AU in the present solar system. On the other hand, the obtained heliocentric distances of Y-75029 and Tsukuba indicate locations of the parent bodies in the past when some parts of the meteorites were exposed to the sun. The heliocentric distances for Y-75029 is in a good agreement with current S-type asteroid distribution, while that for Tsukuba is at the upper tail of the distribution

Oxygen isotope study of Tsukuba chondrite, some HED meteorites and Allende chondrules

Laser fluorination technique coupled with stable isotope mass spectrometry using O_2 is successfully employed to determine the δ^O and δ^O values of different types of meteorites. The oxygen isotope data are reported for the recent fall Tsukuba meteorite confirming it to be an H-type ordinary chondrite. Three diogenites Tatahouine, Y-791199 and Y-791000 are analyzed for oxygen isotopic signatures. Y-791199 and Y-791000 are regarded as cumulate eucrites by many researchers on the basis of petrogenesis. The oxygen isotopes of Tatahouine and Y-791199 are consistent with the diogenite group data. Y-791000 is showing lighter oxygen isotopic composition which is unique among the other diogenites. It may indicate that the parental source for some of cumulate eucrites is different from the non-cumulate ones. The slope 1/2 trend of oxygen isotopes observed in various Allende chondrules (mostly small porphyritic type) signifies that aqueous alteration might be responsible for scattering of data along a nearly mass dependant trend. These chondrules are plotted on a δ^O-δ^O diagram with a slope of 0.52 having Δ^O=-4.24±0.27. The range of δ^O and δ^O data observed in these chondrules is from -7.26 to -0.19‰ and -7.98 to -4.04‰ respectively. The variability in the isotopic composition which caused the scatter on the terrestrial trend implies that on the parent body some low temperature hydrothermal alteration took place

Vertical intrusive magnetite-series granodiorite as a source of surface magnetic anomalies in the King George Island, Antarctica

第3回極域科学シンポジウム/第32回極域地学シンポジウム 11月29日（木） 国立極地研究所 ３階ラウン

Formation processes of magnetic spherules collected from deep-sea sediments -Observations and numerical simulations of the orbital evolution-

Spherules collected from deep-sea sediments were analyzed for major chemical compositions and examined for textural relationships. Two main types of internal texture are observed in Ni-bearing I-type spherules : spherules with Ni-free Fe-oxide mantle and Fe-Ni metallic cores and Fe-Ni oxide spherules without metallic cores. Cores are often observed off-centered. S-type spherules show porphyritic, barred, and fine-grained types of texture. Relict olivine grains are found in some porphyritic S-type spherules. A cooling rate of 55℃/s was calculated for one of these grains based on chemical zonal patterns. For I-type spherules, numerical simulations were performed to constrain the relationship between temperatures, radii of spherules, and the apparent gravitational acceleration with the spherule as a stationary frame of reference. Results indicate that a) spherules lose most of their original mass by evaporation over 1900℃, and, b) the apparent gravitational acceleration is at a maximum during the last stage of evaporation. Based on the observations and numerical simulations of I-type spherules, we propose the following model for their formation : during ablation, the metallic core is off-centered, a surface of the core is then exposed to the air due to the strong apparent gravitational acceleration and, finally, oxidation reactions can proceed on the exposed core surface