REE abundances in the matrix of the Allende (CV) meteorite: Implications for matrix origin

Abstract— The trace element distributions in the matrix of primitive chondrites were examined using four least‐contaminated matrix specimens from the polished sections of the Allende (CV) meteorite. Analysis of rare earth element (REE), Ba, Sr, Rb, and K abundances by isotope dilution mass spectrometry revealed that the elemental abundances of lithophile elements except for alkali metals (K, Rb) in the specimens of the Allende matrix studied here are nearly CI (carbonaceous Orgueil) chondritic (～1 × CI). Compared to refractory elements, all the matrix samples exhibited systematic depletion of the moderately volatile elements K and Rb (0.1–0.5 × CI). We suggest that the matrix precursor material did not carry significant amounts of alkali metals or that the alkalis were removed from the matrix precursor material during the parent body process and/or before matrix formation and accretion. The matrix specimens displayed slightly fractionated REE abundance patterns with positive Ce anomalies (CI‐normalized La/Yb ratio = 1.32–1.65; Ce/Ce* = 1.16–1.28; Eu/Eu* = 0.98–1.10). The REE features of the Allende matrix do not indicate a direct relationship with chondrules or calcium‐aluminum‐rich inclusions (CAIs), which in turn suggests that the matrix was not formed from materials produced by the breakage and disaggregation of the chondrules or CAIs. Therefore, we infer that the Allende matrix retains the REE features acquired during the condensation process in the nebula gas.     

Indigenous Knowledge on Soil Classification of Ethnic Groups in Luang Prabang Province of the Lao PDR

Introduction Traditional agriculture based on indigenous knowledge (IK) has been practiced in many areas for centuries. Such practices are often the basis of very sustainable technologies, which are potentially suitable for developmental programs. Polthanee (2001) reported that such farmer practices have been repeatedly found to be valid, rational and usually suited to the local environmental conditions. Moreover, with increased under- standing of agro-ecosystems, professionals in agricultura…     

The X-ray astronomy satellite “ASCA”

ASCA (ASTRO-D), the fourth X-ray astronomy satellite of ISAS, was successfully launched on February 20, 1993. It carries nested thin-foil X-ray mirrors providing a large effective area over a wide energy range up to 12 keV. A set of CCD cameras and imaging gas scintillation proportional counters are placed on the focal plane.ASCA is a high-throughput imaging and spectroscopic X-ray observatory with these instruments.     

Variations of the pulse profile and the X-ray intensity of GX301-2 (4U1223-62)

Two successive X-ray outbursts of the recurrent X-ray pulsar GX301-2 were observed in April and May, 1982 from Hakucho. Apart from general increase during flares lasting for several days, the X-ray intensity was highly variable on a time-scale of the order of an hour. The outstanding feature is that the amplitude of 700 s pulsation of GX301-2 changes rapidly in a very wide range. When the pulsation is distinct, the depth of modulation is as large as 60%; whereas, the pulse amplitude occasionally diminishes almost to an undetectable level so that the observed X-rays become unpulsed. Such drastic changes are found to occur at any intensity levels observed. In several cases of abrupt changes of pulse amplitude, the intensity at the pulse bottom remained essentially unchanged. These properties suggest a hypothesis that the X-ray emission from GX301-2 consists of a pulsating component with variable amplitude and a non-pulsating component of less variable intensity.     

Unsteady flows in Io’s atmosphere caused by condensation and sublimation during and after eclipse: Numerical study based on a model Boltzmann equation

The behavior of Io’s atmosphere during and after eclipse is investigated on the basis of kinetic theory. The atmosphere is mainly composed of sulfur dioxide (SO₂) gas, which condenses to or sublimates from the frost of SO₂ on the surface depending on the variation of surface temperature (～90–114 K). The atmosphere may also contain a noncondensable gas, such as sulfur monoxide (SO) or oxygen (O₂), as a minor component. In the present study, an accurate numerical analysis for a model Boltzmann equation by a finite-difference method is performed for a one-dimensional atmosphere, and the detailed structure of unsteady gas flows caused by the phase transition of SO₂ is clarified. For instance, the following scenario is obtained. The condensation of SO₂ on the surface, starting when eclipse begins, gives rise to a downward flow of the atmosphere. The falling atmosphere then bounces upward when colliding with the lower atmosphere but soon falls again. This process of falling and bounce back of the atmosphere repeats during the eclipse, resulting in a temporal oscillation of the macroscopic quantities, such as the velocity and temperature, at a fixed altitude. For a pure SO₂ atmosphere, the amplitude of the oscillation is large because of a fast downward flow, but the oscillation decays rapidly. In contrast, for a mixture, the downward flow is slow because the noncondensable gas adjacent to the surface hinders the condensation of SO₂. The oscillation in this case is weak but lasts much longer than in the case of pure SO₂. The present paper is complementary to the work by Moore et al. (Moore, C.H., Goldstein, D.B., Varghese, P.L., Trafton, L.M., Stewart, B. [2009]. Icarus 201, 585–597) using the direct simulation Monte Carlo (DSMC) method.     

Seasonal variation in the Ra/Ra ratio of coastal water within the Sea of Japan: Implications for the origin and circulation patterns of the Tsushima Coastal Branch Current

In the current study, low-background γ-spectrometry was employed to determine the ²²⁸Ra/²²⁶Ra activity ratio and ¹³⁷Cs activity of 84 coastal water samples collected at six sites along the main island of Japan (Honshu Island) within the Sea of Japan, including the Tsushima Strait, and two other representative sites on Honshu Island (a Pacific shore and the Tsugaru Strait) at 1-month intervals in 2006.The ²²⁸Ra/²²⁶Ra ratio of coastal waters in the Sea of Japan exhibited similar patterns of seasonal variation, with minimum values during early summer (²²⁸Ra/²²⁶Ra = 0.6–0.8), maximum values during autumn (²²⁸Ra/²²⁶Ra = 1.5–3), and a time lag in their temporal changes ( 2.5 months and over  1300 km distance). However, the 2 other sites represented no clear periodic variation.In contrast to the positive correlation between ¹³⁷Cs activity (0.6–1.7 mBq/L) and salinity (15–35), the ²²⁸Ra/²²⁶Ra ratio of coastal water samples from the Sea of Japan was not observed to correlate with salinity, and the increase in the ²²⁸Ra/²²⁶Ra ratio was not as marked (0.5–1; May–June 2004 and 2005) during the migration along Honshu Island. The input of land-derived water and/or the diffusion of radium from coastal sediments is unlikely to have affected the wide seasonal variation in the ²²⁸Ra/²²⁶Ra ratio observed in these water samples.The seasonal variation in the ²²⁸Ra/²²⁶Ra ratio recorded for the coastal waters of the Sea of Japan is considered to be mainly controlled by the remarkable changes in the mixing ratio of the ²²⁸Ra-poor Kuroshio and the ²²⁸Ra-rich continental shelf waters within the East China Sea (ECS). After passing through the Tsushima Strait, this water mass moves northeast along the coastline of the Sea of Japan as the Tsushima Coastal Branch Current (TCBC).