Short-term effect of increasing nitrogen deposition on CO2, CH4 and N2O fluxes in an alpine meadow on the Qinghai-Tibetan Plateau, China

National Key Research and Development Program [2010CB833500]; Natural Science Foundation of China [30590381]; Knowledge Innovation Project of Chinese Academy of Sciences [KZCX2-YW-432]

Effects of multiple environmental factors on CO2 emission and CH4 uptake from old-growth forest soils

National Key Research and Development Program [2010CB833502]; National Natural Science Foundation of China [30600071, 40601097, 30590381, 30721140307]; Knowledge Innovation Project of the Chinese Academy of Sciences [KZCX2-YW-432, O7V70080SZ, LENOM07LS-01

Temperature sensitivity of soil respiration is affected by prevailing climatic conditions and soil organic carbon content: A trans-China based case study

National Natural Science Foundation of China [30590381]; Knowledge Innovation Program of the Chinese Academy of Sciences [KZCX2YW-432]; International Partnership Project

Environmental controls over carbon exchange of three forest ecosystems in eastern China

National Natural Science Foundation of China [30590381, 30670384]; Knowledge Innovation Project of the Chinese Academy of Sciences [KZCX2-YW-432]; National Key Research and Development Program [2002CB412501]; 'Hundred Talents' Program of the Chinese Acade

Drivers of soil net nitrogen mineralization in the temperate grasslands in Inner Mongolia, China

Soil net nitrogen mineralization (NNM) of four grasslands across the elevation and precipitation gradients was studied in situ in the upper 0-10 cm soil layer using the resin-core technique in Xilin River basin, Inner Mongolia, China during the growing season of 2006. The primary objectives were to examine variations of NNM among grassland types and the main influencing factors. These grasslands included Stipa baicalensis (SB), Aneulolepidum Chinense (AC), Stipa grandis (SG), and Stipa krylovii (SK) grassland. The results showed that the seasonal variation patterns of NNM were similar among the four grasslands, the rates of NNM and nitrification were highest from June to August, and lowest in September and October during the growing season. The rates of NNM and nitrification were affected significantly by the incubation time, and they were positively correlated with soil organic carbon content, total soil nitrogen (TN) content, soil temperature, and soil water content, but the rates of NNM and nitrification were negatively correlated with available N, and weakly correlated with soil pH and C:N ratio. The sequences of the daily mean rates of NNM and nitrification in the four grasslands during the growing season were AC > SG > SB > SK, and TN content maybe the main affecting factors which can be attributed to the land use type.

N2O fluxes from the native and grazed semi-arid steppes and their driving factors in Inner Mongolia, China

This paper presents results of 2 years (from January 2005 to December 2006) of measurement of N2O fluxes from the native and grazed Leymus chinensis (LC) steppes in Inner Mongolia, China using the static opaque chamber method. The measurement was at a frequency of twice per month in the growing season and once per month in the non-growing season. In addition, the possible effect of water-heat factors on N2O fluxes was statistically analyzed. The results indicated that there were distinct seasonal patterns in N2O fluxes with large fluxes in spring, summer, and autumn but negative fluxes in winter. The annual net emission of N2O ranging from 0.24 to 0.30 kg N2O-N ha(-1) and from 0.06 to 0.26 kg N2O-N ha(-1) from the native and grazed LC steppe, respectively. Grazing activities suppressed N2O production. In the growing season, soil moisture was the primary driving factor of N2O fluxes. The high seasonal variation of N2O fluxes was regulated by the distribution of effective rainfall, rather than precipitation intensity. Air temperature or soil temperature at 0, 5, and 10 cm depth was the most restricting factor of N2O fluxes in the non-growing season.

双马来酰亚胺改性氰酸酯树脂及其复合材料

制备了一种新型的双马来酰亚胺改性氰酸酯树脂以提高这类树脂的耐热性,力学性能及成型工艺性。对合成的树脂作了流变分析,对其玻纤复合材料进行了力学性能测试和热失重分析,结果表明,当双马树脂达到改性氰酸酯树脂的质量分数的37.5%时,新型改性氰酸酯树脂的5%热失重温度为432℃。改性氰酸酯基复合材料在常温条件下的拉伸强度为492.4 MPa,弯曲强度为526.3 MPa

溶剂萃取法制备的纳米CeF_3紫外吸收性能研究

利用Cyanex 923萃取法制备了纳米级CeF3微粉,并研究了分散剂、CeF3量、CeF3预处理灼烧温度和微粉粒径分布等因素对CeF3紫外吸收行为的影响。结果表明,CeF3在255 nm附近有特征吸收峰;分散剂的极性强弱、分散物浓度的改变都会影响吸收峰的强弱;随着粒径的减小,紫外吸收峰发生明显的红移。此外还研究了TiO2包覆CeF3的紫外吸收性质,复合材料在250~400 nm区间内同时出现了TiO2和CeF3的特征吸收峰,复合材料的吸光域范围扩展。

Starburst substituted hexaazatriphenylene compounds: synthesis, photophysical and electrochemical properties

Starburst-substituted hexaazatriphenylene Compounds have been designed and synthesized by introducing various peripheral aryl substituents to the central heterocyclic core. The effects of various substituent groups on the photophysical and electrochemical properties of the substituted hexaazatriphenylene have been investigated. Significant red-shifts of the absorption peak (from 413 nm to 530 nm) and emission peak (from 432 nm to 700 nm) were observed when the electron-donating ability of the aryl substituents was increased, corresponding to a decrease in the band gap from 2.90 eV to 2.05 eV. Introducing bulky substituents with weak electron-donating ability enhances the fluorescence quantum yield from 23% to 87%. In contrast, incorporating aryl substituents with strong electron-donating ability decreases the fluorescence quantum yield.

Enhanced electrochemical properties of nanocomposite polymer electrolyte based on copolymer with exfoliated clays

In this present work, a polymer electrolyte based on polymer/clay nanocomposite has been developed. Montmorillonite (MMT) clay was used as the filler. due to its special size in length and thickness, and its sandwich type structure. The obtained gel polymer electrolytes have high ionic conductivity up to 2.5 mS cm(-1) with high cationic transference number (about 0.64) at room temperature. The influences of the filler on the membrane morphology. the solvent uptake, the ionic conductivity, and the cation transport number were investigated, and thus the significant contribution from the exfoliated organophilic MMT was identified.

Hydrothermal synthesis of spherical and hollow Gd2O3 : Eu3+ phosphors

Spherical and submicrometer-sized hollow Gd2O3:Eu3+ phosphors were prepared by homogeneous precipitation and hydrothermal method by varying the concentrations of reactants and changing the synthesis conditions. In the precipitation step, the spherical nucleus was formed and grew to large particles. In the hydrothermal step, the large particles crystallized to solid or hollow spheres. At last, Gd2O3:Eu3+ phosphors were obtained by annealing at the temperature more than 600 degrees C. The deduced mechanics of forming the solid and hollow spheres was proposed. And the obtained spherical Gd2O3:Eu3+ phosphors had better red luminescence properties. The relative luminescence intensity and the lifetime increased with increasing annealing temperatures.

Properties of complex of Tb(III) and poly(N-isopropylacrylamide)-g-poly(N-isopropylacrylamide-co-styrene) core-shell nanoparticles

We successfully prepared a new kind of thermoresponsive and fluorescent complex of Tb(III) and PNIPAM-g-P(NIPAM-co-St) (PNNS) core-shell nanoparticle. It was found that Tb(III) mainly bonded to 0 of the carbonyl groups of PNNS, forming the novel (PNIPAM-g-P(NIPAM-co-St))-Tb(III) (PNNS-Tb(III)) complex. The maximum emission intensity of the complex at 545 nm is enhanced about 223 times comparing to that of the pure Tb(III). The intramolecular energy transfer efficiency from PNNS to Tb(III) reaches 50%. When the weight ratio of Tb(III) and the PNNS-Tb(III) complex is 1.2 wt.%, the enhancement of the emission fluorescence intensity at 545 nm is highest.

White electroluminescence from a single-polymer system with simultaneous two-color emission: Polyfluorene as blue host and 2,1,3-benzothiadiazole derivatives as orange dopants on the side chain

Four single polymers with two kinds of attachment of orange chromophore to blue polymer host for white electroluminescence (EL) were designed. The effect of the side-chain attachment and main-chain attachment on the EL efficiencies of the resulting polymers was compared. The side-chain-type single polymers are found to exhibit more efficient white EL than that of the main-chain-type single polymers. Based on the side-chain-type white single polymer with 4-(4-alkyloxy-phenyl)-7-(4-diphenylamino-phenyl)-2,1,3-benzothiadiazoles as the orange-dopant unit and polyfluorene as the blue polymer host, white EL with simultaneous orange (lambda(max) = 545 nm) and blue emission (lambda(max) = 432 nm/460 nm) is realised. A single-layer device (indium tin oxide/poly(3,4-ethylenedioxythiophene)/polymer/Ca/Al) made of these polymers emits white light with the Commission Internationale de l'Eclairage coordinates of (0.30,0.40), possesses a turn-on voltage of 3.5 V, luminous efficiency of 10.66 cd A(-1), power efficiency of 6.68 lm W-1, and a maximum brightness of 21240 cd m(-2).