非化学计量氧化物CeO_(2-x)表面氧种的ESR研究

在氧化物表面上发生的催化氧化反应中,由分子氧活化形成的表面氧种起着十分重要的作用。目前,已确证的表面氧种有O~-,O_2~-,O_3~-,这主要归功于电子自旋共振(ESR)方法。

Ce_(0.9)Yb_(0.1)P_5O_(14)晶体的光电压光谱

前文在研究五磷酸铈晶体中Ln~(3+)对Ce~(3+)发光强度的影响时,发现当加入少量的Eu~(3+)和Yb~(3+)离子到CeP_5O_(14)晶体中能使Ce~(3+)的发射产生严重的猝灭现象,以致于用Ce~(3+)的302nm吸收带激发晶体时,观察不到Ce~(3+)的发射,或者十分微弱。令人费解的是Yb~(3+)离子在紫外和可见区无吸收带,Yb~(3+)离子的加入应该成为一个稀释离子,现却使Ce~(3+)的发射产生严

Feeding level-scaled retention efficiency, growth and energy partitioning of a marine detritivorous fish, redlip mullet (Liza haematocheila T. & S.)

The effects of feeding level on growth, retention efficiency, faeces production and energy partitioning of redlip mullet were studied. A practical diet was used and fed at six levels from starvation, 1%, 2%, 3%, 4% of body weight (BW) to satiation for 3 weeks. The temperature was kept at 24 +/- 1 degrees C. Reducing the feeding amount resulted in significantly lower weight gain, and retention efficiency was significantly affected by feeding levels and attained the maximum at maximum feeding intake. Feeding 2% BW was the minimum required for fish to maintain growth. Fish carcass composition under different feeding levels could be divided into three groups: (1) starvation and FL1; (2) FL2 and FL3 and (3) FL4 and satiation, with significant differences among the groups but no differences in the groups except that ash content remained at constant value. Body composition of fish of group 2 was close to initial fish. The thermal-unit coefficient was 0.0381 at satiation, and significantly increased with increasing feeding levels. In order to accurately estimate basal metabolism (HeE), another trial on the relationship between HeE (kJ) and BW (g) was carried out. An exponential curve as HeE=0.1255BW(0.8386) explained this relationship. Intake energy (IE) increased from 11.30 to 63.08 kJ per fish, matching with different feeding levels. Energy allocated to growth of IE decreased with reducing feeding amount. There was a linear relationship between metabolism energy and retention energy in percentage.

开垦对海北高寒草甸土壤有机碳的影响

在中国科学院海北高寒草甸生态系统定位站地区,选择高寒草甸开垦后形成的农田(种植春油菜)作为研究对象,开垦年限分别为0、10、20和30年,利用土壤有机碳密度分组法,对0～10 cm、10～20 cm、20～30 cm、30～40 cm土层土壤有机碳(SOC)及不同组分(轻组有机碳LFOC,重组有机碳HFOC)含量及随开垦年限变化关系进行了研究.结果表明,高寒草甸开垦后土壤有机碳及其组分的变化主要发生在0～10 cm土层,LFOC下降最快,其次为HFOC和SOC,至30年时分别下降了48.63%、43.97%、37.64%.而0～40 cm土体内,SOC、LFOC和HFOC亦呈下降趋势,开垦30年,它们的下降速率分别为785.77、16.79和460.29 kg C•hm-2•yr-1.开垦将大大降低高寒草甸作为碳汇的功能,土壤碳库的总贮量由143 516.94 kg C•hm-2•yr-1下降至114 298.34 kg C•hm-2•yr-1,使其逆转为碳源.

亚高山草甸土纤维素分解过程及与环境因子的对应关系

对海北高寒草甸生态系统的矮嵩草研究表明 ,在亚高山草甸土中纤维素的分解 ,作用均在月均温度最高时达最大,2月份最小,年内表现有明显的单峰式曲线变化过程;非退化矮嵩草草甸的纤维素分解显著高于退化的矮嵩草草甸 ;纤维素分解除自身的季节变化规律外 ,与气象等环境因子有关 ,特别是与水热协调配合具有极显著线性正相关关系(P <0.001)。

Effect of burrowing activity of root vole (Microtus oeconomus Pallas) on plant diversity in alpine meadow

Herbivory and burrowing activity of mammals may influence the species composition and diversity of plant communities. The effect of corridors and holes systems constructed by root vole (Microtus oeconomus Pallas) on the plant species diversity was studied in the habitat of high - mountain meadow (3250 in a.s.l in Qinghai-Tibet Plateau, China). By using grid method, these disturbances were studied on 16 plots (100 cm x 100 cm) distributed in 4 transects in studied area, in August 2000 and 2001. The disturbance intensity index, D, was calculated as the percent of the ground surface disturbed by voles in the study area. Plant species were identified and counted on the same plots. In total 46 plant species were identified - 39% of this number was considered as sensitive to the vole disturbances as their occurrence and/or abundance decreased along the disturbance intensity. Generally, a significantly negative correlation (r = - 0.911 P < 0.01) between vole aboveground disturbances and plant species diversity (H') was found. The results suggest that root vole ground disturbances, especially in the form of actively utilized holes and corridors have significantly negative influence on plant species diversity in high-mountain grassland habitat.

利用“p100/q100”律对胶东地区金矿资源潜力估计

利用幂函数分布在高端截尾 (uppertruncation)条件下具有分形性质 ,即尺度不变的特征 ,证明了统计量q具有分形性质 ,即它与尺度参数k无关。在总体的随机变量X服从幂函数分布条件下 ,从“p10 0 /q10 0”律的概率形式推出“p10 0 /q10 0”律的分形形式 ;“80 /2 0”律是“p10 0 /q10 0”律的一种特殊分形形式。当a =1.16,p =0 .2 0时 ,q =0 .80 ;将“p10 0 /q10 0”律应用于山东胶东地区金矿床储量数据 ,得到了该地区大中小型金矿床的“p10 0 /q10 0”律表达式和相应的百分数。比较理论计算的结果与样本观察值计算的结果大小 ,可预测该地区可能存在 1个或 2个大型金矿床.

Heat capacity and thermochemical study of trifluoroacetamide (C2H2F3NO)

The low-temperature heat capacities of trifluoroacetamide were precisely determined with a small sample precision automated adiabatic calorimeter over the temperature range from 78 to 404 K. A solid-to-solid phase transition, a fusion and a phase transition from a liquid crystalline phase to fully liquid phase have been observed at the temperatures of 336.911+/-0.102, 347.622+/-0.094 and 388.896+/-0.160 K, respectively. The molar enthalpies of these phase transitions as well as the chemical purity of the substance were determined to be 5.576+/-0.004, 11.496+/-0.007, 1.340+/-0.005 kJ mol(-1) and 99.30 mol%, respectively, on the basis of the heat capacity measurements. The molar entropies of the three phase transitions were calculated to be 16.550+/-0.012, 33.071+/-0.029 and 3.447+/-0.027 J mol(-1) K-1, respectively. Further researches of the thermochemical properties for this compound have been carried out by means of TG and DSC techniques. (C) 2000 Elsevier Science B.V. All rights reserved.