Femtosecond pump-probe mass spectra on the dissociative photoionization of CF3I

The multi-photon dissociative photoionization dynamics of CF3I has been studied with femtosecond two-color pump-probe time-of-flight mass spectra at a pump pulse of 265 nm and a probe pulse of 398 nn. This enables the A band and 5ppi(3)7ssigma((2)Pi(1/2)) Rydberg state to be accessed with the pump beam. The observed fast and slow decay components of CF3+ and I+ reflect the fast repulsive A band and some higher lying ion-pair states may be responsible for the decay of the 5ppi(3)7ssigma((2)Pi(1/2)) Rydberg state. The results provide information on the different multi-photon pathways producing these ions and the de-excitation mechanism of the 5ppi(3)7ssigma((2)Pi(1/2)) Rydberg state. (C) 2003 Elsevier Science B.V. All rights reserved.

镧系元素对海水小球藻的毒性效应

用评价化学品对藻类毒性的标准实验方法,研究了12种镧系元素对小球藻生长的抑制情况。结果表明,12种镧系元素抑制小球藻生长的96h半效应浓度(96h EC50 )均为2 9 0 0±0 5 0 μmol·L-1。对各剂量反应方程进行X2 检验,结果表明,符合精度要求,计算出的96h EC50 真实可靠。镧系元素对海水小球藻的生物毒性是相同的,此结果对探明镧系元素对藻类的生态毒理效应具有重要意义。

辽西半干旱地区冬灌后覆盖的抗旱增产作用

辽西半干旱地区冬灌后覆盖的抗旱增产作用王仕新，庄季屏（中国科学院沈阳应用生态研究所，１１００１５）ＥｆｆｅｃｔｏｆＭｕｌｃｂｉｎｇＡｆｔｅｒＷｉｎｔｅｒＩｒｒｉｇａｔｉｏｎｏｎＤｒｏｕｇｂｔＲｅｓｉｓｔａｎｃｅａｎｄＹｉｅｌｄＩｎｃｒｅｍｅｎｔｉｎＳ...

黄土高原水土流失区粮食现状与增产潜力研究

以黄土高原10个试区的攻关资料为基础 ,从区域旱作产量潜势、试区攻关水平和试区所在县的产量现状三个层次 ,详细剖析了黄土高原水土流失区粮食现状和增产潜力。结果指出 ,该区粮食增产潜力很大 ,目前整体产量水平仅达到试区攻关水平的74.7 % ,达到旱作粮食产量潜势水平的54.2 %。在黄土台塬区和丘陵区中 ,丘陵区的粮食增产潜力较台塬区大 ,前者尚有117.6 %增产能力 ,后者仅56.6%。但考虑到人口增长和坡耕地的退垦等因素 ,未来30年内黄土高原水土流失区的粮食供需仍处于负平衡。

Grafting acrylic acid onto polypropylene by reactive extrusion with pre-irradiated PP as initiator

In this paper, the modification of polypropylene (PP) with acrylic acid (AA) by reactive extrusion using pre-irradiated PP (rPP) as initiator was investigated. It was found the relatively high graft degree (Gd) and slight degradation of modified PP was obtained when 20 wt% rPP was used. This result can be explained in terms of effective concentration of free radicals.

Kinetic study of formic acid oxidation on carbon supported Pd electrocatalyst

The oxidation of formic acid at the Pd/C catalyst electrode is a completely irreversible kinetic process with the reaction order of 1.0. The oxidation rate of formic acid is increased with increasing the concentration of formic acid and is decreased with increasing H+ concentration. The apparent negative reaction order with respect to H+ is about -0.18 or -0.04 in H2SO4 or HClO4 solution respectively, because bisulfate anions would inhibit formic acid oxidation at some extent. The kinetic parameters, charge transfer coefficient and the diffusion coefficient of formic acid were obtained under the quasi steady-state conditions.

Preparation of bioactive glass ceramic nanoparticles by combination of sol-gel and coprecipitation method

SiO2-CaO-P2O5 ternary bioactive glass ceramic nanoparticles were prepared via the combination of sol-gel and coprecipitation processes. Precursors of silicon and calcium were hydrolyzed in acidic solution and gelated in alkaline condition together with ammonium dibasic phosphate. Gel particles were separated by centrifugation, followed by freeze drying, and calcination procedure to obtain the bioactive glass ceramic nanoparticles. The investigation of the influence of synthesis temperature on the nanopartilce's properties showed that the reaction temperature played an important role in the crystallinity of nanoparticle. The glass ceramic particles synthesized at 55 degrees C included about 15% crystalline phase, while at 25 degrees C and 40 degrees C the entire amorphous nanopowder could be obtained.

Influence of metal particle size on the hydrogenation of maleic anhydride over Pd/C catalysts in scCO(2)

Hydrogenation of maleic anhydride (MAH) with Pd/C catalysts in supercritical carbon dioxide (scCO(2)) was investigated. The selectivity for gamma-butyrolactone (GBL) reached 97.3% in scCO(2) at 100% conversion of MAH, which was notably higher than that of 77.4% obtained in organic solvent of ethylene glycol dimethyl ether (EGDME). The particle size of Pd exhibited large influence on the reaction rate and selectivity of GBL. Higher selectivity of GBL was obtained with Pd/C catalyst of smaller Pd particle size, and the rate of GBL selectivity increase as a function of CO2 pressure was found to be significantly correlated with Pd particle size.

Rectangular Silver Nanorods: Controlled Preparation, Liquid-Liquid Interface Assembly, and Application in Surface-Enhanced Raman Scattering

In this paper, we for the first time report a polyol method for large-scale synthesis of rectangular silver nanorods in the presence of directing agent and seeds. This method has some clear advantages including simplicity, high quality, and ease of scaleup. Silver nanowires or silver nanorods with a submicrometer diameter could also be facilely prepared when the reaction parameters are slightly changed. Furthermore, a liquid-liquid assembly strategy has been employed to construct uniform rectangular silver nanorod arrays on a solid substrate which could be used as surface-enhanced Raman scattering (SERS) substrates with high SERS activity, stability, and reproducibility. It is found that the SERS spectra obtained from the probe molecules with the different concentrations show different SERS intensifies. As the concentration of 4-aminothiophenol (4-ATP) or rhodamine 6G (R6G) increases, the SERS intensities progressively increase. The enhancement factor for 4-ATP and R6G should be as large as 5.06 x 10(4) or much larger than the value of 5.06 x 10(8), respectively.

Characterization of procaine metabolism as probe for the butyrylcholinesterase enzyme investigation by simultaneous determination of procaine and its metabolite using capillary electrophoresis with electrochemiluminescence detection

Capillary electrophoresis with electrochemiluminescene detection was used to characterize procaine hydrolysis as a probe for butyrylcholinesterase by in vitro procaine metabolism in plasma with butyrylcholinesterase acting as bioscavenger. Procaine and its metabolite N,N-diethylethanolamine were separated at 16 kV and then detected at 1.25 V in the presence of 5.0 mM Ru(bpy)(3)(2+), with the detection limits of 2.4 x 10(-7) and 2.0 x 10(-8) mol/L (S/N=3), respectively. The Michaelis constant K-m value was 1.73 x 10(-4) mol/L and the maximum velocity V-max was 1.62 x 10(-6) mol/L/min. Acetylcholine bromide and choline chloride presented inhibition effects on the enzymatic cleavage of procaine, with the 50% inhibition concentration (IC50) of 6.24 x 10(-3) and 2.94 x 10(-4) mol/L.

Fabrication and luminescence properties of Y2SiWO8 : Dy3+ phosphors via sol-gel process

(YSiWO8)-Si-2:Dy3+ phosphors were prepared through a sol-gel process. XRD and photoluminespectra were used to characterize the resulting phosphors. The results indicated that the phosphors crystallized completely at 1000 degrees C. In Y2SiWO8:Dy3+ phosphors, the Dy3+ showed its characteristic yellow emission at 483nm (F-4(9/2)-H-6(5/2)) and 575nm (F-4(9/2)-H-6(13/2)) upon excitation into 275nm.