行星际等离子区对火星探测器距离观测量的影响          下载免费PDF全文

李杰  胡松杰 《海洋测绘》2010,30(2):32-34

根据Muhleman和Anderson在1981年给出的行星际空间等离子体密度模型,模拟计算了行星际等离子区对8GHz电波的距离延迟与太阳-地球-航天器夹角(SEP)和光路径长度(L)的关系。结果显示,在本文的模拟条件下,距离延迟随SEP和L从几毫米变化到几十米。最后,分别仿真了一条地火转移轨道和环火星轨道,计算了两种情况下行星际等离子区延迟对测站到航天器距离观测量的影响。  相似文献   

Effect of strong magnetic field on chemical potential and electron capture in magnetar     

高杰  罗志全  刘伟伟  李港 《海洋学报(英文版)》2010,29(9)

The chemical potential of electrons in a strong magnetic field is investigated. It is shown that the magnetic field has only a slight effect on electron chemical potential when B<10¹¹ T, but electron chemical potential will decrease greatly when B>10¹¹ T. The effects of a strong magnetic field on electron capture rates for ⁶⁰Fe are discussed, and the result shows that the electron capture sharply decreases because of the strong magnetic field.  相似文献   

线性偏振光激发的错位表面等离子体激元纳米结构聚焦     

宋文涛  林峰  方哲宇  朱星 《海洋学报》2010,32(10):6921-6926

利用扫描近场光学显微镜观测并分析了两种表面等离子体激元纳米结构对表面等离子体激元(SPP)的激发和聚焦现象. 用线偏振光照射有半个周期相位差的环状沟槽结构与有半个周期位相差的环状狭缝结构,得到了单点的SPP聚焦. 有限时域差分法的模拟结果验证了实验中观测的现象. 这两种相位错位的表面等离子体激元纳米结构,突破了由于干涉导致的线偏振光不能得到单个聚焦点的限制. 与采用径向偏振光激发而得到单个聚焦点的方法相比,线偏振光不需要聚焦,也不需要将光束中心对准纳米结构的几何中心即可得到单点聚焦.  相似文献   

Single electron loss in the collisions of C^{3 +} and atomic hydrogen     

刘会平  欧阳晓平  胡华四  苏光辉 《海洋学报(英文版)》2010,29(9)

This paper studies the projectile electron loss cross sections of C^{3 +} colliding with atomic hydrogen in the frame work of extended over-barrier model at intermediate velocities (25 keV/u--600 keV/u). The electron loss is calculated in terms of the interaction between the screened target nucleus and the active projectile electron and of the interaction between projectile electron and target electron. Compared with the convergent close-coupling calculations, screening and anti-screening calculations, this model satisfactorily reproduces the experimentally obtained energy dependence of the electron-impact ionisation cross sections and the single electron loss cross sections over the energy range investigated here.  相似文献   

Application of Atomic Force Microscopy to Observation of Marine Bacteria   总被引：3，自引：0，他引：3  

Tomohiko Nishino  Eiko Ikemoto  Kazuhiro Kogure 《Journal of Oceanography》2004,60(2):219-225

The atomic force microscopy (AFM) is a recently developed, bench-top instrument that can image the surface structures of biological specimens at high resolution with simultaneous measurement of their size. This paper describes the application of AFM to marine bacteria. Both natural and cultured bacteria were retained on a filter or placed on glass, washed, air-dried and observed by AFM. The instrumental condition, the choice of suitable filter, effect of fixation and filtration, comparison with epifluorescent microscopic (EFM) count, and the size and shape of bacterial cells were investigated. An Isopore filter was best for concentration and subsequent observation because of its surface flatness. Cross section images showed that both rod and coccoid cells were flattened, the former usually having a two-humped shape. Bacterial cells were differentiated from non-living particles based on their cross section shape and size. Bacterial counts by AFM and EFM showed good agreement. Although size measurement is easily done by the instrument, AFM tends to overestimate the size of microspheres. More work is thus needed on the size measurement of living organisms. Because AFM easily provides images of natural bacterial cells at high magnification, it can be used as a new tool to study the fine structures of marine bacteria. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Defining the Potential of Nanoscale Re‐Os Isotope Systematics Using Atom Probe Microscopy          下载免费PDF全文

Luke Daly  Phil A. Bland  Svetlana Tessalina  David W. Saxey  Steven M. Reddy  Denis Fougerouse  William D.A. Rickard  Lucy V. Forman  Alexandre La Fontaine  Julie M. Cairney  Simon P. Ringer  Bruce F. Schaefer  Daniel Schwander 《Geostandards and Geoanalytical Research》2018,42(3):279-299

Atom probe microscopy (APM) is a relatively new in situ tool for measuring isotope fractions from nanoscale volumes (< 0.01 μm³). We calculate the theoretical detectable difference of an isotope ratio measurement result from APM using counting statistics of a hypothetical data set to be ± 4δ or 0.4% (2s). However, challenges associated with APM measurements (e.g., peak ranging, hydride formation and isobaric interferences), result in larger uncertainties if not properly accounted for. We evaluate these factors for Re‐Os isotope ratio measurements by comparing APM and negative thermal ionisation mass spectrometry (N‐TIMS) measurement results of pure Os, pure Re, and two synthetic Re‐Os‐bearing alloys from Schwander et al. (2015, Meteoritics and Planetary Science, 50, 893) [the original metal alloy (HSE) and alloys produced by heating HSE within silicate liquid (SYN)]. From this, we propose a current best practice for APM Re‐Os isotope ratio measurements. Using this refined approach, mean APM and N‐TIMS ¹⁸⁷Os/¹⁸⁹Os measurement results agree within 0.05% and 2s (pure Os), 0.6–2% and 2s (SYN) and 5–10% (HSE). The good agreement of N‐TIMS and APM ¹⁸⁷Os/¹⁸⁹Os measurements confirms that APM can extract robust isotope ratios. Therefore, this approach permits nanoscale isotope measurements of Os‐bearing alloys using the Re‐Os geochronometer that could not be measured by conventional measurement principles.  相似文献   

Genesis and Metallogenic Process of the Lujing Uranium Deposit,Southwest Jiangxi Province,China: Constraints of Micropetrography and S–C–O Isotopes     

《Resource Geology》2018,68(3):303-325

The Lujing uranium deposit, located in the southeastern part of the Nanling metallogenic province, is one of the representative granite‐related hydrothermal uranium deposits in South China. Basic geology, geochemistry, and geochronology of the deposit have been extensively studied. However, there is still a chronic lack of systematic research on the genesis and metallogenic process of the deposit. Thus, we recently carried out an electron microprobe and stable isotopic analysis. The main research results and progresses are as follows: Uranium minerals in this deposit include coffinite, pitchblende, and uranothorite, and small amounts of uranium exist in accessory minerals in the form of isomorphism. Coffinite, which occurs predominantly as the pseudomorphs after pitchblende, also occurs as a primary mineral and is locally formed from the remobilization of uranium from adjacent uranium‐bearing minerals. The mineralizing fluid was originally composed of a magmatic fluid generated by late Yanshanian magmatism. The high As content of pyrite in ores may reflect the addition of meteoric water, or the formation water (or both), to the magmatic hydrothermal system. The δ³⁴S values vary from −14.4‰ to 13.9‰ (mean δ³⁴S = −3.9‰), showing a range that is similar to nearby Cambrian metamorphic strata and Indosinian granites, indicating that these host rocks represent the source of sulfur; however, the possibility of a mantle source cannot be completely ruled out. According to our new isotopic data and recent Pb isotopic data, we conclude that the uranium in ores was derived by leaching dominantly from the uranium‐rich host rocks, especially the Cambrian metamorphic strata. The δ¹³C_PDB values (−8.75‰ to 1.40‰; mean δ¹³C_PDB = −5.41‰) and δ¹⁸O_SMOW values (5.45–18.62‰; mean δ¹⁸O = 13.02‰) of reddish calcite from the ore‐forming stage suggest that the CO₂ in the mineralizing fluids was derived predominantly from the mantle, with a small component contributed by marine carbonates. Based on these new data and previous research results, this paper proposes that uranium metallogenesis in the Lujing deposit is closely associated with mafic magmatism resulting from crustal extension during the Cretaceous to Paleogene in South China.  相似文献   

Petrophysical characterisation of tight sandstone gas reservoirs using nuclear magnetic resonance: a case study of the upper Paleozoic strata in the Kangning area,eastern margin of the Ordos Basin,China     

Y. Y. Huyan  T. S. Liu  F. J. Jiang  X. Z. Chen  X. Q. Ma 《Australian Journal of Earth Sciences》2018,65(6):863-875

Residual and movable porosity are significant parameters for characterising petrophysical properties, especially in tight reservoirs. Eight tight sandstone samples from the upper Paleozoic gas-bearing strata in the Kangning area, from the eastern margin of the Ordos Basin, were analysed using nuclear magnetic resonance (NMR), scanning electron microscopy (SEM), petrography, and porosity and permeability tests. The lithology and pore types were identified and classified using petrography and SEM. The residual and movable porosity were obtained with NMR. In addition, NMR was used to visualise pore structure and pore size distribution. The results suggest that the upper Paleozoic sandstones in the study area mainly comprise feldspathic litharenite and litharenite. The sandstone porosity and permeability are low, with means of 5.9% and 0.549 mD, respectively. Four pore types exist in the tight sandstones: residual primary pores, grain dissolution pores, micropores (clay-dominated) and microfractures. The T₂ spectra under water-saturated conditions correlate with pore size and can be used to distinguish small and large pores based on the transverse relaxation time cutoff value of 10 ms, which corresponds to a pore diameter of 0.232 μm. Small pores account for 72% of the pores in the tight sandstones. The continuous bimodal T₂ spectra suggest good connectivity between small and large pores, despite the low porosity and permeability. In this study, the movable porosity of the major tight sandstone gas reservoirs is higher than the residual porosity, which confirms the effective evaluation of movable porosity to tight sandstone reservoirs, based on NMR experiments.  相似文献   

赣南西华山黑钨矿中熔融包裹体的发现和初步研究   总被引：4，自引：0，他引：4  

黄惠兰  李芳  谭靖  张春红 《华南地质与矿产》2012,28(2):181-183

文中概述了西华山黑钨矿中熔融包裹体的一些基本特征和初步测定结果,并提供了相关照片。文中还分析了存在这种包裹体的可能性以及它与普通水溶液包裹体或偶然捕获的流体＋晶体等异常包裹体的区别。  相似文献   

电子探针和LA-ICP-MS技术研究内蒙古浩尧尔忽洞金矿床毒砂矿物学特征     

员媛娇  范成龙  吕喜平  史哲锋  窦智慧  王义天  王梦琦  叶会寿 《岩矿测试》2022,(2):211-225

毒砂的主微量元素组成可以用于判断元素的赋存状态,探讨元素在不同阶段的活化迁移行为.内蒙古浩尧尔忽洞金矿床是产自白云鄂博群黑色岩系中的一个超大型金矿,发育重要载金矿物毒砂和斜方砷铁矿.前人利用传统粉末溶样法对矿石进行同位素分析,探讨了成矿物质来源,但金的迁移富集机制尚未获得解决.为探讨该矿床金迁移富集过程,本文在矿相学的...  相似文献