Presolar grains in the CM2 chondrite Sutter's Mill

The Sutter's Mill (SM) carbonaceous chondrite is a regolith breccia, composed predominantly of CM2 clasts with varying degrees of aqueous alteration and thermal metamorphism. An investigation of presolar grains in four Sutter's Mill sections, SM43, SM51, SM2‐4, and SM18, was carried out using NanoSIMS ion mapping technique. A total of 37 C‐anomalous grains and one O‐anomalous grain have been identified, indicating an abundance of 63 ppm for presolar C‐anomalous grains and 2 ppm for presolar oxides. Thirty‐one silicon carbide (SiC), five carbonaceous grains, and one Al‐oxide (Al₂O₃) were confirmed based on their elemental compositions determined by C‐N‐Si and O‐Si‐Mg‐Al isotopic measurements. The overall abundance of SiC grains in Sutter's Mill (55 ppm) is consistent with those in other CM chondrites. The absence of presolar silicates in Sutter's Mill suggests that they were destroyed by aqueous alteration on the parent asteroid. Furthermore, SM2‐4 shows heterogeneous distributions of presolar SiC grains (12–54 ppm) in different matrix areas, indicating that the fine‐grained matrix clasts come from different sources, with various thermal histories, in the solar nebula.     

Records of the Moon‐forming impact and the 470 Ma disruption of the L chondrite parent body in the asteroid belt from U‐Pb apatite ages of Novato (L6)

Novato, a newly observed fall in the San Francisco Bay area, is a shocked and brecciated L6 ordinary chondrite containing dark and light lithologies. We have investigated the U‐Pb isotope systematics of coarse Cl‐apatite grains of metamorphic origin in Novato with a large geometry ion microprobe. The U‐Pb systematics of Novato apatite reveals an upper intercept age of 4472 ± 31 Ma and lower intercept age of 473 ± 38 Ma. The upper intercept age is within error identical to the U‐Pb apatite age of 4452 ± 21 Ma measured in the Chelyabinsk LL5 chondrite. This age is interpreted to reflect a massive collisional resetting event due to a large impact associated with the peak arrival time at the primordial asteroid belt of ejecta debris from the Moon‐forming giant impact on Earth. The lower intercept age is consistent with the most precisely dated Ar‐Ar ages of 470 ± 6 Ma of shocked L chondrites, and the fossil meteorites and extraterrestrial chromite relicts found in Ordovician limestones with an age of 467.3 ± 1.6 Ma in Sweden and China. The lower intercept age reflects a major disturbance related to the catastrophic disruption of the L chondrite parent body most likely associated with the Gefion asteroid family, which produced an initially intense meteorite bombardment of the Earth in Ordovician period and reset and degassed at least approximately 35% of the L chondrite falls today. We predict that the 470 Ma impact event is likely to be found on the Moon and Mars, if not Mercury.     

Chromium isotopic systematics of the Sutter's Mill carbonaceous chondrite: Implications for isotopic heterogeneities of the early solar system

Recent studies have shown that major meteorite groups possess their own characteristic ⁵⁴Cr values, demonstrating the utility of Cr isotopes for identifying genetic relationships between the planetary materials in conjunction with other classical tools, such as oxygen isotopes. In this study, we performed Cr isotope analyses for whole rocks and chemically separated phases of the new CM2 chondrite, Sutter's Mill (SM 43 and 51). The two whole rocks of Sutter's Mill show essentially identical ε⁵⁴Cr excesses (SM 43 = +0.95 ± 0.09ε, SM 51 = +0.88 ± 0.07ε), relative to the Earth. These values are the same within error with that of the CM2‐type Murchison (+0.89 ± 0.08ε), suggesting that parent bodies of Sutter's Mill and Murchison were formed from the same precursor materials in the solar nebula. Large ε⁵⁴Cr excess of up to 29.40ε is observed in the silicate phase of Sutter's Mill, while that of Murchison shows 15.74ε. Importantly, the leachate fractions of both Sutter's Mill and Murchison form a steep linear anticorrelation between ε⁵⁴Cr and ε⁵³Cr, cross‐cutting the positive correlation previously observed in carbonaceous chondrites. The fact that L4 acid leachate fraction contains higher ⁵⁴Cr excesses than that of L5 step designed to dissolve refractory minerals suggests that spinel is not a major ⁵⁴Cr carrier. We also note that L5 contains ⁵³Cr anomalies lower than the solar initial value, suggesting it carries a component of nucleosynthetic anomaly unrelated to the ⁵³Mn decay. We have identified five endmember components of nucleosynthetic origin among the early solar system materials.     

A VERTICAL DISTRIBUTION MODEL OF NUTRIENTS AND DISSOLVED OXYGEN IN THE SOUTHERN TAIWAN STRAIT

Sinoe vertical transport of nutrients and dissolved oxygen are quite important in the water col-umn and have drawn serious attention these recent years, a one-dmension numerical model is tried to simulate the vertical distribution of nutrients and dissolved oxygen in June at two research sites in the southemTaiwan Strait. Physical transport parameters are calibrated by temperature simulation, and thenare used to simulate the profiles of NO_3, PO_4 and dissolved oxygen. The simulation was generally success-ful for both stations. The importance of various factors, such as upwelling tidal current andbiogeochemical activities, which influence the vertical distribution of nutrients and dissolved oxygen, is revealed by analysis of the modeling results. Some important rates, fluxes and ratios are also estimated anddiscussed on the basis of simulation.     

An investigation of sand–dust storm events and land surface characteristics in China using NOAA NDVI data

Observations from 560 weather stations in China show that sand–dust storms occur most frequently in April in north China. The region consists of Sub-dry Mid Temperate, Dry Mid Temperate, Sub-dry South Temperate and Dry South Temperate Zones and much of the land surface is desert or semi-desert: it is relatively dry with minimal rainfall and a high annual mean temperature. In most regions of China, the annual mean frequency of sand–dust events decreased sharply between 1980 and 1997 and then increased from 1997 to 2000. Statistical analyses demonstrate that the frequency of sand–dust storms correlates highly with wind speed, which in turn is strongly related to land surface features; on the other hand, a significant correlation between storm events and other atmospheric quantities such as precipitation and temperature was not observed. Accordingly, land surface cover characteristics (vegetation, snowfall and soil texture) may play a significant role in determining the occurrence of sand–dust storms in China. Analysis of Normalized Difference Vegetation Index derived from National Oceanic and Atmospheric Administration and Empirical Orthogonal Function show that since 1995 surface vegetation cover in large areas of Northern China has significantly deteriorated. Moreover, a high correlation is shown to exist among the annual occurrence of sand–dust storms, surface vegetation cover and snowfall. This suggests that the deterioration of surface vegetation cover may strongly influence the occurrence of sand–dust storms in China. Soils with coarse and medium textures are found to be more associated with sand–dust storms than other soils.     

A Catalog of Luminous Infrared Galaxies in the IRAS Survey and Second Data Release of SDSS

We selected a sample of luminous infrared galaxies by cross-identification of the Faint Source Catalogue (FSC) and Point Source Catalogue (PSC) of the IRAS Survey with the Second Data Release of the SDSS. The size of our sample is 1267 for FSC and 427 for PSC by using the 2σ significance level cross-section. The "likelihood ratio" method is used to estimate the individual's reliability and for defining two more reliable subsamples (908 for FSC and 356 for PSC). A catalog of infrared, optical and radio data is compiled and will be used in further work. Some statistical results show that luminous infrared galaxies are quite different from ultra-luminous infrared galaxies. The AGN fractions of galaxies at different infrared luminosities and the radio-infrared correlations are consistent with the previous studies.     

校园网络计费系统研究与实现

在分析校园网计费需求、常用网络计费方式的不足基础上提出一种通用的校园网计费系统解决方案，并且较为详细地描述了实现该系统的主要技术。     

东营市东营区努力开创国土资源信访工作新局面

近年来，东营区国土资源局不断加大信访宣传工作力度，强化信访工作责任，完善信访管理机制，全面提高基层信访工作水平，使信访工作重心和责任下移，努力从源头上减少信访问题的发生。连续3年荣获“全省国土资源信访工作先进单位”荣誉称号。     

THE VERTICAL DISTRIBUTION OF AGROTOPOCLIMATIC RESOURCES IN THE WARM SECTORS OF THE THREE GORGES AREA OF THE CHANGJIANG RIVER

罗洪，邓先瑞ＴＨＥＶＥＲＴＩＣＡＬＤＩＳＴＲＩＢＵＴＩＯＮＯＦＡＧＲＯＴＯＰＯＣＬＩＭＡＴＩＣＲＥＳＯＵＲＣＥＳＩＮＴＨＥＷＡＲＭＳＥＣＴＯＲＳＯＦＴＨＥＴＨＲＥＥＧＯＲＧＥＳＡＲＥＡＯＦＴＨＥＣＨＡＮＧＪＩＡＮＧＲＩＶＥＲ￥ＤｅｎｇＸｉａｎｒｕｉ；...     

储良广眼砧穗不亲和问题研究

储良广眼的砧穗不亲和现象在众多个体中呈现从亲和至不亲和的连续变化，随砧、穗周长差异的增大，不亲和症状表现突出。砧、穗周长比值与几个生长量指标存在显著相关。提出以砧／穗比作为衡量不亲和程度指标。靠接加砧结果表明对严重不亲和树出现的症状有较大的缓解。