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911.
Very few studies deal with the biogeochemical behaviors of rare earth elements (REEs) in goldfields. This paper presents the
geochemical and biogeochemical characteristics of REEs within the soil–plant system in the Hetai goldfield, Guangdong, China.
The samples from the goldfield region show anomalies in distribution patterns and behavioral characteristics of REES as compared
with those from the background areas. The REEs in rocks, soils, and plants prove to be much higher than those in the surrounding
regions. The distribution patterns of REEs are characterized by LREE-enrichment and HREE-depletion, with the REE concentrations
in Layer A being the highest. Differentiations between LREEs and HREEs may lead to some extent of negative Eu anomaly in the
soils. Research results demonstrate that the REEs in a soil profile can be transferred and accumulated during the mineral
formation and supergenic geochemical processes, and the anomalies are obviously related to the geological settings for the
REE-bearing ore-forming processes and to the geochemical characteristics of the habitats for the REE-bearing plants. For Dicranopteris dichotoma, the total amount of REEs in the tissues shows an order of leaf > root > stem, while for Pinus massoniana the order becomes root > leaf > stem. The distribution patterns of REEs in Pinus massoniana leaves are similar to those in soils where the plants grow up in the mineralization area. However, in the background areas
the REE distribution patterns for Pinus massoniana stems are similar to those for soils where the plants grow up. Parameters such as biological absorption coefficients and
biological transfer coefficients show the differences in REE absorption features among plants and indicate that REEs can be
transferred among plant organs. The two coefficients can reveal the different survival mechanisms for the two plant species,
which are subject to long-term REE-affected stress conditions in the gold mineralization zone. 相似文献
912.
The internal transcribed spacer regions (ITS1 and ITS2) and 5.8S rRNA genes were sequenced in six populations of four Aspidisca species, namely A. leptaspis, A. orthopogon, A. magna and A. aculeata. Phylogenetic trees were constructed by means of Bayesian inference (BI), Maximum Parsimony (MP), Neighbor-Joining (NJ),
and Maximum Likelihood (ML) to assess the inter- and intra-species relationships within the genus Aspidisca. All trees show similar topologies with stable supports and indicate that: (1) four well known groups, i.e., Oligotrichia,
Stichotrichia, Choreotrichia and Hypotrichia, are distinctly outlined within the class Spirotrichea, and all are monophyletic
other than Hypotrichia; (2) members of Aspidisca can be distinguished well, based on the ITS1-5.8S-ITS2 region sequences, and A. leptaspis and A. magna shared a closer relationship than other species; (3) Aspidisca and Euplotes branch early in the subclass Hypotrichia. To compare the phylogenetic relationships based on different genes, SSU rRNA trees
were also constructed with nearly the same species inclusion, which revealed different topologies of inter-species, inter-genera
and inter-subclasses. 相似文献
913.
914.
Normal Reference Value of Red Blood Cell Count of Chinese Presenile Men and Geographical Factors 总被引:1,自引:0,他引:1
HE Jinwei GE Miao SU Huimin LIANG Wei CHEN Hongfei 《中国地理科学(英文版)》2007,17(1):92-98
This paper aims at providing a scientific basis for unifying the normal reference value standards of red blood cell count of Chinese presenile men. The paper, using microscopical counting method, studies the relationship between the normal reference values of 38,061 samples of red blood cell count of presenile men and eight geographical factors in 297 units in China. It is found that the correlation of geographical factors and the normal reference value of red blood cell count of presenile men is quite significant (F=303.00, P=0.000). By using the method of stepwise regression analysis, one regression equation is inferred. It is concluded that if geographical data are obtained in a certain area, the normal reference value of red blood cell count of presenile men in this area can be reckoned by using the regression analysis. Furthermore, according to the geographical factors, China can be divided into eight regions: Northeast China Region, North China Region, Shanxi-Shaanxi-Inner Mongolia Region, Middle and Lower Reaches of the Changjiang River Region, Southeast China Region, Northwest China Region, Southwest China Region and Qinghai-Tibet Plateau Region. 相似文献
915.
本文根据视横向速度是否红移依赖对相对论束模型进行分类并提出对相应模型进行统计检验的方法 .作为应用的例子 ,本文利用前人文献所给视超光速样本进行统计分析 ,并对有关结果进行了讨论 相似文献
916.
辽南50号金伯利岩管金刚石的包裹体类型一直被认为是以超镁铁岩组合为主。最近,在同一岩管中发现一颗金刚石中有两种组合类型矿物共生:橄榄石,为超镁铁岩型;石榴石,绿辉石,为榴辉岩型组合。化学成分分析还表明,同一矿物的不同颗粒化学成分没有明显变化。根据石榴石与绿辉石的共生组合关系,钙、镁和铁之间的交换,计算其平衡温度为1203℃,压力为5×10 ̄9Pa。超镁铁岩与榴辉岩包裹体共生,表明该金刚石成生环境的复杂性。很可能是地幔动力学过程或者是幔源岩浆多期多相导致金刚石成生环境的迅速变化。 相似文献
917.
918.
江苏省粮食单产空间差异的因素分解 总被引:1,自引:0,他引:1
区分粮食单产空间差异的来源,是粮食单产空间特征和成因机制研究的一个基础问题,可以为粮食促产政策的制定提供较为可靠的依据。基于粮食作物配置的视角,以江苏省为例,运用因素分解法,探讨粮食单产空间结构及单产变化空间差异的贡献因素。结果表明:1)当前江苏省粮食作物配置结构的空间差异可以说明近80%的粮食单产的空间差异,而江苏省粮食生产力的空间分布与粮食单产空间差异仅低度相关。2)1990s中期以来,江苏省粮食单产增幅有南弱北强的倾向,主要来源是生产力效应,结构效应对这种空间分化起到强化作用。因此,相对于笼统的粮食单产指标,排除结构因素的粮食生产力因素能更为准确地体现粮食现实生产力的变化。 相似文献
919.
920.