Shower Meteoroids: Constraints From Interplanetary Dust Particles And Leonid Meteors     

Rietmeijer  Frans J. M. 《Earth, Moon, and Planets》2000,88(1):35-58

The cometary Leonid meteoroids represent a size range in between largest carbon-richIDPs and the smallest CI meteorites. Their dustball structure and chemistry offer anopportunity to constrain hierarchical dust accretion inferred from petrologic studies ofaggregate and cluster IDPs. The Leonid shower meteoroids of known ``comet ejection'ages provide an opportunity to study space weathering of cometary dust over periodsof up to several hundred years. The meteors and aggregate and cluster IDPs displaycontinuous thermal modification of organics and volatile element (Na, K-bearing phases), that occur as discrete minerals and amorphous solids each different response during kinetically controlled ablation. Leonid meteoroids are not excessively Na-rich. The occurrences of Leonid meteors can now be accurate predicted and combined withknowledge better models for the settling rates, collections of surviving dust becomea comet nucleus-sampling mission. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

贺兰山地区春季沙尘气溶胶的化学组分和富集因子分析   总被引：29，自引：11，他引：18  

牛生杰  章澄昌 《中国沙漠》2000,20(3):264-268

春季在贺兰山两侧的内蒙古吉兰泰和宁夏银川机场采集不同沙尘天气条件下的沙尘气溶胶浓度样本,用中子活化分析测定35种元素浓度,揭示了沙尘气溶胶中的元素浓度特征,沙尘天气下沙尘气溶胶中地壳元素含量增加,且含量随沙尘暴强度增强而增大。讨论了作为参考物质的地壳元素的取值及地球化学分类。沙尘气溶胶相对地壳和黄土的富集因子,以亲硫元素和亲沉积层元素为最高。亲地壳元素中的主成分元素在有沙尘天气时,其富集因子也偏高。  相似文献   

几种纤维矿物粉尘的真空有机吸附及表面基团变化     

宋功保  石荣铭  董发勤  冯启明  李国武 《岩石矿物学杂志》2000,19(3):264-271

利用真空有机吸附和红外光谱分析法,研究了几种纤维矿物粉尘对不同偶极矩的正己烷（偶极矩为０）、乙醚（偶极矩为１．１６）和吡啶（偶极矩为２．１９）的吸附特征及这种有机试剂对表面基团的影响。研究发现：纤维矿物粉尘对有机试剂的吸附能力并不完全与有机试剂的偶极矩大小成正比;部分纤维矿物粉尘对正己烷的吸附为化学吸附,吸附解吸后出现了１２６２￣１２６７ｃｍ＾－１、１３１１ｃｍ＾－１的新的ＩＲ谱带,它们应是部分纤  相似文献   

矿物粉尘对人体血清物质的吸附行为研究   总被引：1，自引：0，他引：1  

张宝述  董发勤  邓建军  李国武 《岩石矿物学杂志》2000,19(3):272-279

通过测定吸附后人体血清的成分,并利用红外光谱研究了几种矿物粉尘对血清中物质的吸附作用,结果表明,矿物粉尘对血清中物质的吸附具有选择性,主要是吸附了血清中的蛋白质和脂类等生物大分子。不同矿物吸附生物大分子的选择性不同,这主要与矿物的结构和表面海性等因素有关。红外光谱研究表明,吸附机理主要是物理吸附,可能也存在化学吸附。另一方面,矿物粉尘在血清中发生了一定程度的阳离子交换和溶解作用。  相似文献   

纤维矿物粉尘在Gamble溶液中的溶解行为   总被引：6，自引：3，他引：3  

董发勤  李国武  霍冀川  迟燕华 《岩石矿物学杂志》2000,19(3):199-205

本文用人工配制的Ｇａｍｂｌｅ溶液和三个酸度系列,研究了６对粉尘在模拟人体环境下９６ｄ的溶液特征和生物持久性。结果表明：不同粉尘中铁元素的溶解速率多数出现两个峰值区,三八面体结构型粉尘中铁与镁元素溶解同步。高镁矿物粉尘溶解速率在第一阶段多出现峰值;沸石、硅灰石的钙溶解速率比较稳定,硅灰石在低ｐＨ值区表现出前高后低的特点;Ｓｉ在Ｇａｍｂｌｅ溶液中的溶解峰点在ｐＨ５体系中出现在４８ｄ以前,在ｐＨ７体系中  相似文献   

炼铜烟灰制取硫酸铜除铁新工艺研究   总被引：1，自引：0，他引：1  

刘俊峰 《矿产与地质》2000,14(5):349-352

研究和比较了各种炼铜烟灰制取硫酸铅除铁工艺,实验结果表明：用氧气或空气氧化配合过氧化法去除炼铜烟灰酸浸液中铁,除铁率90％,过氧化氮氧化深度除铁,除铁率99．8％,溶液中铁含量降至0．01g/L以下。  相似文献   

Circular polarization by scattering from spheroidal dust grains     

T. M. Gledhill  A. McCall 《Monthly notices of the Royal Astronomical Society》2000,314(1):123-137

Large degrees of circular polarization at near-infrared wavelengths have been reported in the OMC1 star-forming region. This discovery, in combination with compelling evidence for the existence of non-spherical aligned grains in star formation regions, has prompted us to investigate scattering from spheroidal particles as a possible mechanism for the production of large circular polarization in reflection nebulae. We use a dipole calculation to model the small particle limit and a T -matrix code to treat arbitrarily sized particles. We find that size distributions of perfectly aligned spheroids, with only modest 2:1 axis ratios, are capable of producing circular polarization of up to 50 per cent when scattering unpolarized incident light. This is the case even for dielectric materials, such as 'astronomical silicate', as long as sufficient large particles are included in the size distribution. We consider the effects of particle alignment and find that spinning oblate spheroids should be much more efficient circular polarizers than equivalent prolate spheroids.  相似文献   

Large-scale structure of galaxies in the Ophiuchus region     

Takashi Hasegawa  †  Ken-ichi Wakamatsu  ‡  Matthew Malkan  ‡  Kazuhiro Sekiguchi  John W. Menzies  Quentin A. Parker  Jun Jugaku  Hiroshi Karoji  Sadanori Okamura 《Monthly notices of the Royal Astronomical Society》2000,316(2):326-344

The large-scale structure around the Ophiuchus cluster of galaxies in the vicinity of the Galactic Centre ( l =05, b =95, cz =8500 km s⁻¹) is investigated on the basis of a galaxy survey and spectroscopic observations made for a 12°×17° area. The galaxy survey was performed using six ESO/SERC Sky Survey Atlas films, and 4021 galaxies were detected in total. Recession velocities were newly obtained for 179 galaxies to make the total number of galaxies in the survey area with known velocities 219.
In the distribution of bright galaxies, we identified seven new clumps of galaxies. Comparing the surface number density of bright galaxies with the Galactic extinction, which is estimated from the 100‐μm flux density in the IRAS Sky Survey Atlas, we demonstrate that the seven clumps are not spurious as a result of the inhomogeneity of the Galactic extinction. Among the seven clumps, two are found to be clusters and four to be groups on the basis of the histogram of recession velocities and the number of member galaxies. The Ophiuchus cluster, two newly identified clusters, and four groups are all concentrated at 9000 km s⁻¹. Field galaxies are also distributed centred at 8500 km s⁻¹. Hence field galaxies occupy a common three-dimensional region with galaxies in the clusters and groups, and altogether they form a large-scale structure of supercluster size. As opposed to the overdensity in the supercluster region, the mean number density of galaxies in the velocity range 0–5000 km s⁻¹ is only 25 per cent of the mean number density of the Universe, comparable with the density of the well-known Böotes void. Hence this nearby three-dimensional region in Ophiuchus is a void of galaxies also.  相似文献   

A discussion on the mass loss formulae for OH/IR stars     

Xiong Guan-zhu  Chen Pei-sheng 《Chinese Astronomy and Astrophysics》2000,24(4):501-510

It is found that the mass loss rate derived from S₂₅/S₁₂ is generally greater than that from the OH flux. This suggests an increasing loss rate with time. It is found that the gas-to-dust ratio decreases during the evolution Of OH/IR stars. An empirical relation between the gas-to-dust ratio and the dust mass loss rate is derived, leading to a formula for calculating the total mass loss rate directly from the IRAS 60 μm flux. OH/IR stars with silicate emission have a larger range of mass loss ratio, from 10⁻⁷ to 10⁻⁵ M/yr; those with silicate absorption, a smaller range between 10⁻⁵ and 10⁻⁴ M/yr. So a large increase in the mass loss rate takes place during the emission phase.  相似文献   

Evidence of an atmospheric forcing on bacterioplankton and phytoplankton dynamics in a high mountain lake     

Elvira Pulido-Villena  Isabel Reche  Rafael Morales-Baquero 《Aquatic Sciences - Research Across Boundaries》2008,70(1):1-9

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