Yamato-793605: A new lherzolitic shergottite from the Japanese Antarctic meteorite collection

Y-793605 is a new martian meteorite from Antarctica that can be classified as a lherzolitic shergottite. Y-793605 mainly shows a poikilitic texture (large pyroxene oikocryst with enclosed olivine and chromite), but partly contains non-poikilitic areas (mainly maskelynite, olivine, and pigeonite). Olivine in the non-poikilitic area is more Fe-rich and shows a narrower compositional distribution than that in the poikilitic area. Low-Ca pyroxenes in the non-poikilitic area are also more Fe-rich (En_Fs_Wo_7∿En_Fs_Wo_) than those in the poikilitic area (En_Fs_Wo_3∿En_Fs_Wo_). Augites in the poikilitic area are usually present rimming the oikocrysts (En_Fs_Wo_ to En_Fs_Wo_). The crystallization sequence of minerals in Y-793605 is considered to have begun by initial crystallization of cumulus phases (olivine and chromite) from the parent magma. Then, low-Ca pyroxenes and later augite poikilitically enclosed cumulus phases, and became a large oikocryst. Due to accumulation of phases, small interstitial melts formed between the oikocryst boundaries, and plagioclase crystallized from the Ca-Fe-rich melt along with pigeonite. After minor augite crystallization in the non-poikilitic area, all phases experienced re-equilibration (e. g., homogenization of olivine). Y-793605 shows a close relationship to previously known lherzolitic shergottites ALH77005 and LEW88516. Especially, olivine composition of Y-793605 is nearly identical to that of LEW88516. Pyroxene and maskelynite compositions are almost the same among these three meteorites. Although it is hardly possible to consider that Y-793605 is paired with ALH77005 or LEW88516 in the sense that Y-793605 was in the same fall with them, it can be concluded that Y-793605 originated from the same igneous body or rock in Mars as ALH77005 and LEW88516

Lherzolitic Martian meteorites Allan Hills 77005, Lewis Cliff 88516 and Yamato-793605: Major and minor element zoning in pyroxene and plagioclase glass

Three lherzolitic Martian meteorites (ALH77005,LEW88516 and Y-793605) show very similar petrography and mineralogy. They consist of the poikilitic and non-poikilitic (interstitial) areas that are heterogeneous on a cm-scale. A detailed electron microprobe analysis of pyroxene and plagioclase glass from these meteorites gives characteristic distributions of major and minor elements. It is striking that pyroxene and plagioclase glass in all three meteorites have nearly identical zoning patterns of these elements, while olivine shows different chemistry. This is because olivine chemistry was largely controlled by a late-stage re-equilibration which did not significantly modify the major and minor element distributions in pyroxene and plagioclase glass. However, a close look at minor element zoning in plagioclase glass exhibits slightly different zoning patterns among these three meteorites, corresponding to different degrees of re-equilibration (degrees of re-equilibration : ALH77005>LEW88516>Y-793605). Nevertheless, it is evident that they experienced a very similar igneous crystallization history and they are likely to have originated from the same igneous unit on Mars

Diffuse reflectance spectra for heated samples of an H5 chondrite: Importance of oxygen fugacity at heating

We obtained (biconical) diffuse reflectance spectra of the Nuevo Mercurio (H5) ordinary chondrite in the 200-2500 nm wavelength region. The samples were heated in the temperature range of 800-1200℃ at constant oxygen fugacities at one log unit below the iron-wustite (IW) buffer (IW-1) and two log units above the IW buffer (IW+2). The spectra of the samples heated to temperatures lower than 1050℃ at IW+2 show low spectral contrast and shorter wavelength positions of UV drop-off compared with the unheated <100 μm sample. On the basis of our heating experiments, this work suggests that oxygen fugacity affects the spectra of the heated samples especially at IW+2,implying that oxygen-fugacity control is important for heating experiment and that oxygen fugacity may play a role in the surface processes on asteroids

Increasing the Receptor Tyrosine Kinase EphB2 Prevents Amyloid-β-induced Depletion of Cell Surface Glutamate Receptors by a Mechanism That Requires the PDZ-binding Motif of EphB2 and Neuronal Activity.

Diverse lines of evidence suggest that amyloid-β (Aβ) peptides causally contribute to the pathogenesis of Alzheimer disease (AD), the most frequent neurodegenerative disorder. However, the mechanisms by which Aβ impairs neuronal functions remain to be fully elucidated. Previous studies showed that soluble Aβ oligomers interfere with synaptic functions by depleting NMDA-type glutamate receptors (NMDARs) from the neuronal surface and that overexpression of the receptor tyrosine kinase EphB2 can counteract this process. Through pharmacological treatments and biochemical analyses of primary neuronal cultures expressing wild-type or mutant forms of EphB2, we demonstrate that this protective effect of EphB2 depends on its PDZ-binding motif and the presence of neuronal activity but not on its kinase activity. We further present evidence that the protective effect of EphB2 may be mediated by the AMPA-type glutamate receptor subunit GluA2, which can become associated with the PDZ-binding motif of EphB2 through PDZ domain-containing proteins and can promote the retention of NMDARs in the membrane. In addition, we show that the Aβ-induced depletion of surface NMDARs does not depend on several factors that have been implicated in the pathogenesis of Aβ-induced neuronal dysfunction, including aberrant neuronal activity, tau, prion protein (PrP(C)), and EphB2 itself. Thus, although EphB2 does not appear to be directly involved in the Aβ-induced depletion of NMDARs, increasing its expression may counteract this pathogenic process through a neuronal activity- and PDZ-dependent regulation of AMPA-type glutamate receptors

Comparison of Fe-Mg interdiffusion coefficients in olivine

We have compared Fe-Mg interdiffusion coefficients in olivine reported in several literatures by analyzing experimentally produced diffusion profiles. The chemical zoning profiles of olivine measured with an electron microprobe were compared with those calculated by numerically solving the diffusion equation by using different diffusion coefficients. For our experimental results, the Fe-Mg interdiffusion coefficient in olivine reported by D. J. Misener (Carnegie Inst. Washington Publ., 634,117,1974) with oxygen fugacity dependence gives the best fit to the observed profile. The Fe-concentration dependence of the Fe-Mg interdiffusion coefficient in olivine is important when the Fe content varies widely

Effects of thermal fluctuations on thermal inflation

The mechanism of thermal inflation, a relatively short period of accelerated expansion after primordial inflation, is a desirable ingredient for a certain class of particle physics models if they are not to be in contention with the cosmology of the early Universe. Though thermal inflation is most simply described in terms of a thermal effective potential, a thermal environment also gives rise to thermal fluctuations that must be taken into account. We numerically study the effects of these thermal fluctuations using lattice simulations. We conclude that though they do not ruin the thermal inflation scenario, the phase transition at the end of thermal inflation proceeds through phase mixing and is therefore not accompanied by the formations of bubbles nor appreciable amplitude of gravitational waves.Comment: 14 pages, 4 figure