Resonant Raman Scattering and Photoluminescence Emissions from Above Bandgap Levels in Dilute GaAsN Alloy

The transitions of E0 ,E0 ＋A0, and E＋ in dilute GaAs（1-x） Nx alloys with x = 0.10% ,0.22% ,0.36% ,and 0.62% are observed by micro-photoluminescence. Resonant Raman scattering results further confirm that they are from the intrinsic emissions in the studied dilute GaAsN alloys rather than some localized exciton emissions in the GaAsN alloys. The results show that the nitrogen-induced E E＋ and E0 ＋ A0 transitions in GaAsN alloys intersect at a nitrogen content of about 0.16%. It is demonstrated that a small amount of isoelectronic doping combined with micro-photoluminescence allows direct observation of above band gap transitions that are not usually accessible in photoluminescence.

地带性多年冻土区小流域水文状况对水热季节变化的响应

大兴安岭北部是我国唯一一片地带性连续多年冻土分布区，也是欧亚大陆地带性多年冻土分布区的南缘，因此对气候变化的响应十分敏感。全球变暖必然会影响到冻土土壤水分状态的变化，从而对冻土区的流域水文状况产生影响；小流域是区域研究的主要对象，冻土活动层变化的最直接后果就是引起流域内水文状况发生变化。本研究利用DEM数据划分小流域，在划分出的小流域的基础上，探讨了影响流域流量变化的几个因子，包括降水、蒸散(Evapotranspiration, ET)和土壤持水，初步简化了流域水量平衡方程，可为进一步研究提供基础。主要包括以下方面的内容： a)平均温度的升高必然会影响到冻土土壤水分状态的变化，从而导致区域小流域水文状况随之变化； b)融深与海拔高度存在一定的相关关系，融深随海拔的升高而增加；土壤水分随海拔变化的规律并不明显。年内降水主要集中在每年的5月份到10月份；11月份和12月份降水一般比春季的多，这两个月份气温很低，降水形式主要是雪。不同地点不同海拔下冻土活动层土壤水分含量变化很大，这和当地的环境条件有关，如地表覆被、土壤类型、坡度、坡向等。 c)参考植被蒸散呈明显的周期性波动规律。每年同期蒸散大致维持在同一水平上。从年初到年中，流域内蒸散呈不断增加的趋势。但是变化规律又稍有不同，每年大致从1月份到4月份，蒸散随时间变化很快，几乎呈线性增加。但是从4月中旬开始，到下半年的9月中旬，ET0呈震荡变化趋势。4月中旬开始，蒸散开始震荡增加，到7月份左右达到最大，然后开始震荡降低，大约到9月中旬或10月初开始转为近似线性减少趋势。 d)土壤水分含量的变化ΔW���以表示为下式：ΔW=R-(0.260Rn-0.036N) Kc+c���其中，ΔW���土壤水分含量的变化；R流域出口处流量；Rn为太阳净辐射；N为白昼长度；Kc���被系数；c���常数。 上述研究结果可以为进一步分析年内冻土湿地水分状况对温度变化的响应提供基础，也可为气候变化条件下冻土湿地水文过程的响应研究提供参考。

Characteristics of indoor/outdoor PM2.5 and elemental components in generic urban；roadside and industrial plant areas of Guangzhou City；China

IEECAS SKLLQG

Distribution and mode of occurrence of As；Hg and Se and sulfur in coal Seam 3 of the Shanxi Formation,Yanzhou Coalfield；China

IEECAS SKLLQG

Selective hydrogenation of citral catalyzed with palladium nanoparticles in CO2-in-water emulsion

CO2-in-Water (C/W) emulsion was formed by using a nonionic surfactant of poly (ethylene oxide)-poly (propylene oxide)-poly (ethylene oxide) (P123), and palladium nanoparticles were synthesized in situ in the present work. The catalytic performance of Pd nanoparticles in the C/W emulsion has been discussed for a selective hydrogenation of citral. Much higher activity with a turnover frequency (TOF) of 6313 h(-1) has been obtained in this unique C/W emulsion compared to that in the W/C microemulsion (TOF, 23 h(-1)), since the reaction was taking place not only in the surfactant shell but also on the inner surface of the CO2 core in the C/W emulsion. Moreover, citronellal was obtained with a higher selectivity for that it was extracted to a supercritical carbon dioxide (scCO(2)) phase as formed and thus its further hydrogenation was prohibited. The Pd nanoparticles could be recycled several times and still retain the same selectivity, but it showed a little aggregation leading to a slight decrease in conversion.

Microstructure analysis of nylon 66 by WAXD and SAXS

The analysis of the small angle X-ray scattering (SAXS) data was based upon particle characteristic function, one-dimensional electron-density correlation function and particle distribution function. The microstructure of nylon 66 with different degrees of crystallinity was studied by means of X-ray scattering method. The radius of gyration R-g, the Porod radius R-p, the thickness of crystalline region L-c the thickness of non-crystalline region L-n, the thickness of interphase region d(tr), the long period L, the semiaxises of particles (a, a, b), the distribution of the particle sizes and the scattering invariant were calculated. The results indicate that there was a significant interphase region between the crystalline region and the non-crystalline region. and its content (W-t,W-x) should not be neglected in comparison with that of crystalline region W-c,W-x. The morphology of nylon 66 prepared by isothermal crystallization at a high temperature was mainly a lamellar structure, while the spherical crystals dominated in the quenched sample. The size of the particles in the quenched sample was smaller than that of those in the isothermally crystallized sample. and the distribution of the particle sizes in the isothermally crystallized sample was wider.

Influence of annealing on structure of Nylon 11

Differential scanning calorimeter (DSC), wide-angle X-ray diffraction (WAXD), small-angle X-ray scattering (SAXS), and density techniques have been used to investigate the structural parameters of the solid state of Nylon 11 annealed at different temperatures. The equilibrium heat of fusion Delta H-m(0) and equilibrium melting temperature T-m(0) were estimated to be 189.05 J g(-1) and 202.85 degrees C respectively by using the Hoffman-Weeks approach. The degree of crystallinity (W-c,W-x) ranged approximately 24-42% was calculated by WAXD and compared with those by calorimetry (W-c,W-h) and density (W-c,W-d) measurements. The radius of gyration R-g, crystalline thickness L-c, noncrystalline thickness L-a, long period L, semiaxes of the particles (a, b), electron-density difference between the crystalline and noncrystalline regions eta(c) - eta(a), and the invariant Q increased with increasing annealing temperature. The analysis of the SAXS data was based upon the particle characteristic function and the one-dimensional electron-density correlation function. An interphase region existed between the crystalline and noncrystalline region with a clear dimension of about 2 nm for semicrystalline Nylon 11. Instead of the traditional two-phase model, a three-phase model has been proposed to explain these results by means of SAXS.

稀土配合物的光致和电致发光性能的研究

自从C.W.Tang报导了高效、高亮度的双层结构有机薄膜电致发光(OEL)器件以来,由于其驱动电压低、可做成大面积及制作工艺简单等优点,使其在平板显示和显像领域具有巨大应用潜力而成为研究热点。但以有机小分子和聚合物做发光层的有机电致发光器件的发射光谱谱带较宽,色纯度不好,不利于显示和显像。1991年,J.Kido等人以稀土配合物Tb(acac)_3(acac:乙酰丙

Influence of interface on radiation effects of crystalline polymer - radiation effects on polyamide-1010 containing BMI

Aimed at saving the radiation dose required to crosslinking the polyamid-1010, BMI/PA1010 systems containing different amounts of difunctional crosslinking agent N,N'-bis-maleimide-4,4'-biphenyl methane (BMI) were prepared and the structure changes at the crystallographic and supermolecular levels before and after irradiation were studied by using WAXD, SAXS, and DSC techniques. It was found that by incorporation of BMI the microcrystal size L-100 is lowered due to the formation of hydrogen bond between the carbonyl oxygen of BMI and the amide hydrogen of PA1010 in the hydrogen bonded plane, and the overall crystallinity W-c is also decreased. The presence of BMI causes the crystal lamella thickness d(c) to decrease and greatly thickens the transition zone d(tr) between the crystalline and amorphous regions. As for the irradiated specimen, the maximum increments in the L-100 and W-c against dose curves decrease with BMI content, and the interception point D-i, at which the L-100 and W-c curves intercept their respective horizontal line of L-100/L-100(0) and W-c/W-c(0)=1, shift to lower dose with an increase in BMI concentration. In addition. the mechanism of the radiation chemical reactions in the three different phases under the action of BMI are discussed with special focus on the interface region. (C) 1999 Published by Elsevier Science Ltd. All rights reserved.

Variation of crystallographic parameters in PEEKK with heat treatment temperature

Using the wide-angle X-ray diffraction method, the variation of crystallographic parameters of poly(aryl ether ether ketone ketone) (PEEKK) has been studied in different heat treatment temperatures. All the reflections and their intensities as well as their Miller indices are presented in detail according to an orthorhombic system. The investigation indicates that the unit cell parameters a, b, c and the unit cell volume V systematically decrease with increasing heat treatment temperature. This variation is interpreted by the change of conformation of polymer molecular chains during thermal treatment. The results calculated from the formula of degree of crystallinity (W-c,W-x) for PEEKK, which was derived based on X-ray scattering intensity theory and the graphic multipeak resolution method, are compatible with the density measurement (W-c,W-d) and calorimetry (W-c,W-h) values. (C) 1997 Elesevier Science Ltd.

Crystal structure and crystallinity of poly(aryl ether biphenyl ether ketone ketone)

The crystal structure of poly(aryl ether biphenyl ether ketone ketone) (PEDEKK) was determined to comprise a two-chain orthorhombic unit cell with dimensions a 0.778 nm, b = 0.606 nm and c = 2.375 nm by using wide-angle X-ray diffraction (WAXD). According to the orthorhombic system, the 12 reflections of this polymer were indexed. The crystallite size increases with increasing the crystallization temperature. The results of the degree of crystallinity (W-c,W-x) calculated from WAXD were compatible with those from density (W-c,W-d) and calorimetry (W-c,W-h) measurements.

Effect of heat treatment on the parameters of crystal structure and degree of crystallinity of poly(aryl-ether-ether-ketone)

The variations of unit cell parameters and crystallite size of nine PEEK samples treated at various temperatures have been studied by using Wide-Angle X-ray Diffraction (WAXD), The results indicate a decrease in unit cell parameter a,b and c but an increase in crystallite size L(hkl) With the increase beat treatment temperature. Based on X-ray scattering intensity theory and using the graphic multipeak resolution method, the formula of degree of crystallinity (W-c,W-X) for PEEK is derived. The results calculated are compatible with the density measurement and calorimetry.