Reduction property and catalytic activity of Ce1-XNiXO2 mixed oxide catalysts for CH4 oxidation

Ce1-XNiXO2 oxides with X varying from 0.05 to 0.5 were prepared by different methods and characterized by XRD and TPR techniques. Ce(0.7)Mi(0.3)O(2) sample prepared by sol-gel method shows the highest reducibility and the highest catalytic activity for methane combustion. Three kinds of Ni phases co-exist in the Ce1-XNiXO2 catalysts prepared by sol-gel method: (i) aggregated NiO on the support CeO2, (ii) highly dispersed NiO with strong interaction with CeO2 and (iii) Ni atoms incorporated into CeO2 lattice. The distribution of different Ni species strongly depends on the preparation methods. The highly dispersed NiO shows the highest activity for methane combustion. The NiO aggregated on the support CeO2 shows lower catalytic activity for methane combustion, while the least catalytic activity is found for the Ni species incorporated into CeO2. Any oxygen vacancy formed in CeO2 lattice due to the incorporating of Ni atoms adsorbs and activates the molecular oxygen to form active oxygen species. So the highest catalytic activity for methane combustion on Ce0.7Ni0.3O2 catalyst is attributed not only to the highly dispersed Ni species but also to the more active oxygen species formed. (C) 2002 Elsevier Science B.V. All rights reserved.

黄土丘陵区坡面林-草边界土壤水分特征

研究了黄土高原丘陵区林-草边界上旱季和雨季土壤水分的空间分布变化特征.结果表明,旱季林地土壤水分的变异系数都小于草地,林地内各个层次土壤含水量差异不大,草地内各个层次土壤含水量差别较大;雨季林地土壤水分的变异系数都大于草地,林地内各个层次土壤含水量差别较大,而草地内各个层次土壤含水量差异不显著;林-草边界各个层次土壤水分的变异程度为弱变异或中等变异.林-草边界在旱季和雨季具有不同的影响域,旱季边界影响域为从林外0·4倍树高距离到林内0·4倍树高距离;雨季边界影响域为从林外0·4倍树高距离到林内0·8倍树高距离.因此,可将林-草景观划分为3个区草地区,即由距林缘0·4倍树高距离处向草地方向延伸;林缘区,即由林外0·4倍树高距离到林内0·4倍树高距离(旱季)或0·8倍树高距离(雨季);林地区,即由林内0·4倍树高距离(旱季)或0·8倍树高距离(雨季)处向林内方向延伸.林-草边界水平方向上3个分区的土壤水分垂直分布呈现出不同的变化规律,而且旱季的规律特征与雨季相反.

Validation and in situ application of an automated dissolved nickel monitor for estuarine studies

The validation of a fully automated dissolved Ni monitor for in situ estuarine studies is presented, based on adsorptive cathodic stripping voltammetry (AdCSV). Dissolved Ni concentrations were determined following on-line filtration and UV digestion, and addition of an AdCSV ligand (dimethyl glyoxime) and pH buffer (N-2-hydroxyethylpiperazine-N′-2-ethanesulphonic acid). The technique is capable of up to six fully quantified Ni measurements per hour. The automated in situ methodology was applied successfully during two surveys on the Tamar estuary (south west Britain). The strongly varying sample matrix encountered in the estuarine system did not present analytical interferences, and each sample was quantified using internal standard additions. Up to 37 Ni measurements were performed during each survey, which involved 13 h of continuous sampling and analysis. The high resolution data from the winter and summer tidal cycle studies allowed a thorough interpretation of the biogeochemical processes in the studied estuarine system.

平阴玫瑰花芽分化期叶片内源激素的变化

对平阴玫瑰花芽分化期叶片甲醇提取物进行IAA、ZR、GA3、ABA的分离、纯化和测定。结果发现,所测的几种激素均表现出明显的变化规律,其中IAA和GA3在花芽分化期含量逐渐下降,且在分化临界期出现一低峰,而ZR和ABA则完全相反。同时经比较分析得出ABA/GA3,ABA/IAA,ZR/GA3,ZR/IAA也表现明显的变化规律,即比值总体趋势是逐渐提高,且均在分化临界期含量出现一飞跃,显然ABA/GA3,ABA/IAA,ZR/GA3,ZR/IAA在平阴玫瑰的花芽分化过程中起着重要的调控作用,由此推测,增加植物体内的ABA、ZR的含量或降低IAA、GA3的含量,都可以促进玫瑰的花芽分化;反之则抑制其花芽分化。

外生菌根真菌促进油松人工幼林生长的应用研究

从不同林型下分离获得的外生菌根真菌纯培养菌株中 ,选择了其中劣味乳菇、赫丝膜菌、褐环乳牛肝菌、毛边滑绣伞4株优良菌种 ,对油松人工幼林(5年生)进行菌剂混合接种试验。结果表明 :采用外生菌根真菌对油松幼林接菌 ,能够使土壤微生物种群数量发生变化 ;接菌后的土壤中的细菌、真菌、放线菌总数比不接菌的有明显的增加 ,其中真菌增加732.35 %。对接菌油松进行菌根侵染调查发现 ,接菌后的油松菌根侵染率为75 % ,不接菌的为20 % ;对连续两年接种菌剂的油松幼林调查发现 ,与不接菌剂的相比施用菌剂的油松地径、株高显著增加。由此认为 ,外生菌根真菌作为一项生物接种技术对促进油松幼林的生长具有重要作用

油松水源保护林人工诱导更新与定向恢复机理

以油松水源保护林为对象,进行人工诱导更新与定向恢复机理研究。结果表明,在郁闭林分内油松更新苗密度平均为5 375株.hm-2,更新苗年龄为1~2年,而在人工Gap“效应岛”样地内,更新苗密度平均为17 062.5株.hm-2,其中1~2年、3~4年、5~6年生更新苗分别占73.44%,13.97%和12.59%;生长季光照强度在0、1.5和2.0 m三个不同高度梯度上,在Gap内部的平均值分别为289.0×100、542.0×100和589.0×100 lux,在对照林分内分别为139.0×100、146.0×100和246.0×100lux;从夏季观测到的空气温度平均值日变化分析,在白天Gap内的温度高于郁闭林分内部,温差可差2~3℃,在夜间Gap内的温度低于郁闭林分内,温差可差0.5~1℃;在白天6:00~11:00,人工Gap“效应岛”内空气湿度明显低于郁闭林分内,在其它时间段大致相当;对于同一层次土壤而言,Gap内的土壤温度明显高于郁闭林分内且变化幅度大,在0、10和20 cm三个梯度上Gap与郁闭林分相比土壤温度最大差值分别可达10、5和2℃;0~10、10~20和20~30 cm三个层次平均土壤含水量在Gap内分别为16.9%1、5.1%和12.3%,在郁闭林分内分别为14.6%、12.5%和9.9%。总体上比较二者的光照强度、空气温度、空气湿度、土壤温度、土壤水分等有显著差异,因此人工Gap“效应岛”的创建是诱导其内部微环境因子变化的基础,也是油松水源保护林定向恢复更新的机理之所在。

中国苔类新记录种:附基缺萼苔(Gymnomitrionlaceratum(Steph.)Horik.

报道产于西藏的中国苔类植物缺萼苔科缺萼苔 1个新记录种 :附基缺萼苔 (Gymnomitrionlaceratum(Steph .)Horik .)。该种主要特征为植物体具残存但可辨别的腹叶 ,有别于该科其它种类。

近2000年来内蒙后套平原黄河河道演变

通过遥感影像、地貌沉积、历史文献与地图等相关资料分析集成研究,将后套平原分为西部冲积扇平原,东部是泛滥冲积平原,并详细探讨了近2000年来本区黄河河道的演变。公元前2世纪时,后套西部平原南(上)冲积扇停止发育,北(下)冲积扇河道发育,黄河主河道的位置与现代不同,它偏于泛滥平原北部的阴山山前东流;公元6世纪后套平原西部北冲积扇上黄河河道向东移,在东部泛滥平原上黄河明显地分为南北两汊,而黄河主流仍位于河套平原北部山前;18世纪早期至末期,黄河主河道从河套平原的北部山前南移至平原南部;19世纪中叶‘北河’淤塞,

Perovskite-Like Mixed Oxides (LaSrMn1-x Ni (x) O4+delta, 0 a parts per thousand currency sign x a parts per thousand currency sign 1) as Catalyst for Catalytic NO Decomposition: TPD and TPR Studies

Catalytic NO decomposition on LaSrMn1-x Ni (x) O4+delta (0 a parts per thousand currency sign x a parts per thousand currency sign 1) is investigated. The activity of NO decomposition increases dramatically after the substitution of Ni for Mn, but decreases when Mn is completely replaced by Ni (x = 1.0). The optimum value is at x = 0.8. These indicate that the catalytic performance of the samples is contributed by the synergistic effect of Mn and Ni. O-2-TPD and H-2-TPR experiments are carried out to explain the change of activity. The former indicates that only when oxygen vacancy is created, could the catalyst show enhanced activity for NO decomposition; the latter suggests that the best activity is obtained from catalyst with the most matched redox potentials (in this work, the biggest Delta T and Delta E values).

Half metallic properties of Sr2CuOsO6

The half metallic properties of the recent synthesized Sr2CuOsO6 were predicted by using the density functional theory. The effects of electron correlation and spin-orbit coupling (SOC) were studied. The calculations show that without considering SOC effect, Sr2CuOsO6 is half metallic and ferrimagnetic. By including both electron correlation and spin-orbit coupling, the total spin magnetic moment is 0.89 mu(B), total orbital moment 0.43 mu(B) in opposite direction, making the net magnetic moment 0.46 mu(B). SOC ruins the half metallic character. Crown Copyright (C) 2009 Published by Elsevier B. V. All rights reserved.

Preparation and luminescence properties of Mn2+-doped ZnGa2O4 nanofibers via electrospinning process

One-dimensional Mn2+-doped ZnGa2O4 nanofibers were prepared by a simple and cost-effective electrospinning process. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric and differential thermal analysis (TG-DTA), scanning electron microscopy (SEM), energy-dispersive X-ray spectrum (EDS), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), photoluminescence (PL) and cathodoluminescence (CL) spectra as well as kinetic decays were used to characterize the samples. SEM results indicated that the as-formed precursor fibers and those annealed at 700 degrees C are uniform with length of several tens to hundred micrometers, and the diameters of the fibers decrease greatly after being heated at 700 degrees C. Under ultraviolet excitation (246 nm) and low-voltage electron beams (1-3 kV) excitation, the ZnGa2O4:Mn2+ nanofibers presents the blue emission band of the ZnGa2O4 host lattice and the strong green emission with a peak at 505 nm corresponding to the T-4(1)-(6)A(1) transition of Mn2+ ion.