Kinetics of indium atomization from different atomizer surfaces in electrothermal atomic absorption spectrometry (ETAAS)

The kinetic parameters of indium atomization in electrothermal atomic absorption spectrometry (ETAAS) have been determined by a newly proposed method. Effect of the atomizer surface and the palladium modifier on the kinetics of indium atomization has been investigated. The mechanisms of indium atomization seem to be identical for the pyrolytically coated graphite and the uncoated graphite tubes, i.e. the rate-limiting step for the atomization changes from a first order kinetics at lower temperatures into a nearly 1/3 order kinetics at higher temperatures, which may suggest that the analyte moves from a dispersed state to agglomates with increasing temperature. However, for the zirconium coated graphite tube, the atomization of indium is controlled by a single mechanism with the kinetic order of near 2/3 and the activation energy of 186 ± 13 kJ/mol. Relatively weak indium—zirconium carbide interactions and the release of indium from the sphere of molten indium metal on the zirconium coated surface are suggested. In the presence of palladium, a simple mechanism, i.e. the release of indium from the solid solution of the In and the Pd on the pyrolytically coated graphite surface, is proposed to account for the observed first order kinetics and the activation energy of 421 ± 27 kJ/mol.     

蓖麻油基AB交联聚合物的介电性质

在-180℃至140℃范围内,用几个频率测定了蓖麻油基AB交联聚合物的介电松弛谱。对这些聚合物的多重松弛和相行为的研究表明,试样中的两组份在介电松弛谱上显现出相容的或近似互容的特征。试样中的次级松弛归因于聚氨酯组份中链段的局部运动。提出了一个描述界面极化的方法,计算了界面极化松弛活化能,它们同试样中组份间的相容性,界面相互作用大小以及分子链的柔曲性有关。     

1,1′-双(苄硫基)二茂铁铂、铑配合物对烯烃硅氢加成反应的催化性能

二茂铁衍生物的金属配合物对于氢化、偶联及不对称合成的催化作用已有报道,但用于烯烃硅氢加成还只有关于手征性二茂铁膦钯配合物和聚合物负载二茂铁膦钯、膦铂配合物的研究。Macosko等曾用顺式二氯化双乙硫醚铂配合物催化聚异丁烯末端双键进行硅氢加成,我们也发现聚-4-氧杂-6,7-双甲硫基庚基硅氧烷铂配合物对于烯烃的硅氢加成反应具有良好的催化活性。因此,预期1,1′-双烷硫基二茂铁铂、铑配合物也应是烯烃硅氢加成的有效催化剂。     

镥单酞菁和镥双酞菁电子转移过程的研究

本文用循环伏安法研究镥单酞菁和镥双酞菁在非水溶剂中的电化学行为,获得了相应的氧化还原反应半波电位E1/2,测定了其中四个氧化还原反应的电子转移速度常数ks。指出非水溶剂对镥单酞菁和镥双酞菁的电化学行为具有程度不同的影响。     

Adjuvant antiproliferative and cytotoxic effect of aloin in irradiated HeLaS3 cells

Naturally occurring phytoanthracycline, aloin, was used to radiosensitize HeLaS3 human cervix carcinoma cells. The results indicated that the cytotoxic adjuvant effect of aloin was synergistic with gammaionizing radiation at all drug concentrations and comparable to the cytotoxicity of 5–10 Gy ionizing radiation alone. Radiosensitization of HeLaS3 cells was achieved by 60 μM aloin, which reduced the IC₅₀ dose of ionizing radiation from 3.4 to 2 Gy. Ionizing radiation and aloin alone or in combination are shown to cause perturbation of the HeLaS3 cell-cycle and increase the percentage of cells in the DNA synthesis (S) phase of the cell cycle. While either of the agents applied alone causes programmed cell death by apoptosis, the simultaneous cell damage by both agents through the altered redox balance compromised cell capacity to conduct this program and led to synergic cytotoxic cell death by necrosis. The text was submitted by the authors in English.     

高强聚乙烯纤维的冷等离子体改进

高强聚乙烯纤维的冷等离子体改进金士九，倪亦斌，张佐光（中国科学院化学研究所北京１０００８０）（北京航空航天大学北京）关键词　高强聚乙烯纤维，等离子体，表面改性，界面性能由高强聚乙烯纤维制成的复合材料抗高速撞击（抗弹）性能远远优于芳纶纤维，广泛用作各种...     

反丁烯二酸稀土配合物的合成及晶体结构

合成了反丁烯二酸C_4H_4O_4与六种稀土(Eu, Gd, Tb, Y, Er, Lu)的配合物M_2F_3·12H_2O(H_2F=C_4H_4O_4). 用X射线衍射法测定了它们的晶体学参数, 并测定了其中五种配合物的结构. 指出存在两类不同的结构, 其中铕配合物为三斜晶系, 空间群P(1), 铕离子配位数为10. 铽、钇、铒、镥配合物为单斜晶系, 空间群为P2_1/c, 配位数为8. 配合物均具有三维网状结构.     

Application of chemometric methods to the simultaneous kinetic spectrophotometric determination of iodate and periodate based on consecutive reactions

A kinetic spectrophotometric method for the simultaneous determination of iodate and periodate in mixtures was proposed. The method is established on the different kinetic behaviours of the analytes which react with starch–iodide in the presence of sodium chloride in sulfuric acid medium. The kinetic data were collected from 260 to 900 nm every 10 nm, within a time range of 0–180 s at 1 s interval, and the absorbance collected at 291, 354 and 585 nm, respectively, increased linearly with the concentration between 0.1–1.2 mg L^− 1 for both iodate and periodate. The mechanism investigation revealed that the iodate/periodate–iodide–starch system is a consecutive reaction. Subsequently, the mathematical model for the quantitative kinetic determination based on the consecutive reactions by utilizing chemometric methods was deduced, and the simultaneous determination of synthetic mixtures of iodate and periodate was then applied. Kinetic data collected at 291, 354 and 585 nm, were processed by chemometric methods, such as classical least square (CLS), principal component regression (PCR), partial least square (PLS), back-propagation artificial neural network (BP-ANN), radial basis function–artificial neural network (RBF-ANN) and principle component–radial basis function–artificial neural network (PC-RBF-ANN). The results showed that calibration model with the data collected at 354 nm had some advantages for the prediction of the analytes as compared with the ones of other two wavelengths, and the PLS and PC-RBF-ANN gave the lower prediction errors than other chemometric methods. The proposed method was applied to the simultaneous determination of iodate and periodate in several real samples; and the standard addition method yielded satisfactory recoveries in all instances.     

Photodissociation dynamics of C6HxF6-x (x = 1-4) at 193 nm

Photodissociation of fluorine-substituted benzenes, including 1,3-difluorobenzene, 1,2,4-trifluorobenzene, 1,2,4,5-tetrafluorobenzene, and pentafluorobenzene, at 193 nm under collision-free conditions has been studied in separate experiments using multimass ion imaging techniques. HF elimination was found to be the major dissociation channel for all of these molecules. Small amounts of photofragments of C(6)H(3)F(2) and C(6)H(2)F(3) from 1,3-difluorobenzene and 1,2,4-trifluorobenzene, respectively, were also observed. They correspond to the minor dissociation channel of hydrogen elimination. Dissociation rates and fragment translational energy distributions obtained from experimental measurements suggest that HF and hydrogen elimination reactions occur in the ground electronic state. The potential energy surface obtained from ab initio calculations indicates that the four-center reaction in the ground electronic state is the major dissociation mechanism for the HF eliminations. A comparison with the RRKM calculation has been made.     

稀土-蛋氨酸配合物的热力学

在25 ℃和μ=0.15 mol·L~(-1)[NaCl]条件下, 用pH电位法测定了L-蛋氨酸的质子化常数、15个稀土元素与该配体生成配合物的稳定常数。表明稀土与L-蛋氨酸可生成1:1配合物。讨论了“四分组效应”及钇的位置。用量热滴定法直接测定了稀土与L-蛋氨酸生成1:1配合物的△H_(101)值, 计算了△S_(101)和△G_(101)值。