YP_5O_(14):Er~(3+),Tm~(3+)晶体的合成

研究了水热法合成晶体,浓度配比、生长温度对晶体生长习性的影响.合成了一系列化学计量比的Y_(1-x-0.3)Er_(0.3)Tm_xP_5O_(14)(x=0.01～0.1)晶体,观察和分析了晶体的缺陷及成因,测定和讨论了晶体结构.

Simultaneous enumeration of diatom, protozoa and meiobenthos from marine sediments using Ludox-QPS method

The Ludox-QPS method is a newly developed technique, which combines the Ludox HS 40 density centrifugation and quantitative protargol stain, to enumerate marine ciliates with good taxonomic resolution. We tested the method for simultaneous enumeration of diatoms, protozoa and meiobenthos and compared its extraction efficiency for meiobenthos with that of the routine Ludox-TM centrifugation and a modified protocol using Ludox HS 40. We conducted the evaluation with a sample size of 8.3 ml each from sandy, muddy-sand and muddy sediments collected from the intertidal area of the Yellow Sea in summer 2006 and spring 2007. The Ludox-QPS method not only produced high extraction efficiencies of 97 +/- 1.3% for diatoms and 97.6 +/- 0.8% for ciliates, indicating a reliable enumeration for eukaryotic microbenthos, but also produced excellent extraction efficiencies of on average 97.3% for total meiobenthos, 97.9% for nematodes and 97.8% for copepods from sands, muddy sands and mud. By contrast, the routine Ludox-TM centrifugation obtained only about 74% of total meiobenthos abundance with one extraction cycle, and the modified Ludox HS 40 centrifugation yielded on average 93% of total meiobenthos: 89.4 +/- 2.0% from sands, 93 +/- 4.1% from muddy sands and 97.1 +/- 3.0% from mud. Apart from the sediment type, sample volume was another important factor affecting the extraction efficiency for meiobenthos. The extraction rate was increased to about 96.4% when using the same modified Ludox centrifugation for a 4 ml sediment sample. Besides the excellent extraction efficiency, the Ludox-QPS method obtained higher abundances of meiobenthos, in particular nematodes, than the routine Ludox centrifugation, which frequently resulted in an uncertain loss of small meiobenthos during the sieving process. Statistical analyses demonstrated that there were no significant differences between the meiobenthos communities revealed by the Ludox-QPS method and the modified Ludox HS 40 centrifugation, showing the high efficiency of the Ludox-QPS method for simultaneous enumeration of diatom, protozoa and meiobenthos. Moreover, the comparatively high taxonomic resolution of the method, especially for diatoms and ciliates, makes it feasible to investigate microbial ecology at community level.

祁连山海北高寒湿地40～80cm土壤温度状况观测分析

海北高寒湿地土壤水分达超饱和状态,土体热容量大,因而地温在随时间进程中变化平稳,日、年较差较小. 年内季节冻土并不深厚,多维持于1 m 左右,小于高山草甸土分布区. 由于50 cm 层次年平均地温仅为1. 2 ℃,暖季的6～9 月平均为2. 8 ℃左右. 因此,按温度诊断特点来看,该类型高寒湿地土在中国土壤分类中属寒冷性土壤温度状况,仍为正常有机土.

长石及其伴生矿物的~(40)Ar/~(39)Ar法对比研究

~(40)Ar-~(39)Ar法是继K-Ar法后发展起来的一个新的年代学分支，自1962年Sigurgeirssion正式提出~(40)Ar-~(39)Ar计时理论以来，经C. M. Merrihue, G. Turner, G. B. Dalrymple, M. A. Lanphere, I. McDougall, J. G. Mitchell等人的不断改造和完善，现已发展成为一门较为成熟的学科。~(40)Ar-~(39)Ar法以其独特的优点而倍受地质学家的偏爱，其中阶段加热技术是~(40)Ar-~(39)Ar法得以广泛应用的关键，它不仅可以提供一般的年代学资料，同时，还提供诸如样品的受热历史、过剩Ar、封闭温度以及岩体的隆起速率等许多信息。近十年来，对这一领域的研究，无论是在理论方面，还是在实验技术方面，都取得了可喜的进展。