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31.
前言卟啉在生物化学、分析化学、药物化学等领域有着广泛研究和重要应用[1~3]。近年来虽然对卟啉类化合物的研究报道很多[4~6],但对卟啉在酸性介质中的研究很少。较早期的研究工作认为卟啉类化合物在酸性介质中仅以其二酸形式存在[7]。本文实验结果显示me... 相似文献
32.
若干中性配体对Mo—Fe—S簇合物自兜的影响 总被引:3,自引:1,他引:3
通过电子吸收光谱的变化研究了一些含N和含P中性配体对MoS_4~(2-)-nFeCl_2-DMF体系形成立方烷型Mo-Fe-S簇合物的可能影响。 相似文献
33.
为了研究白血病骨髓移植病人全血微量元素铜的变化及其意义 ,用原子吸收光谱法检测了正常对照组与白血病骨髓移植患者预处理前及移植后骨髓空虚期全血微量元素铜的含量。结果表明 ,正常对照组全血铜浓度与白血病骨髓移植患者预处理前全血铜浓度差异无显著性 (P >0 0 5 ) ,而与骨髓空虚期全血铜浓度有显著性差异 (P <0 0 5 ) ,说明白血病缓解后血铜接近正常对照组水平 ,而白血病骨髓移植患者预处理后骨髓空虚期全血铜含量高于正常对照组 ,说明预处理影响微量元素铜的代谢 ,本文就其影响机理进行了研究 相似文献
34.
The properties of the triplet excited state of [60] fullerene-containing cyclic sulphoxide have been investigated by time-resolved absorption spectroscopy. Transient absorption bands of [60] fullerene-containing cyclic sulphoxide showed two decay-components, which wrer attributed to triplet excited states of different spin multiplicity. The properties of photoexcited states of [60] fullerene-containing cyclic sulphoxide are also reported. 相似文献
35.
A. Parrish R. L. de Zafra J. W. Barrett P. Solomon B. Connor 《International Journal of Infrared and Millimeter Waves》1987,8(5):431-440
Atmospheric opacity values in the zenith direction are given for a wavelength of 1.1 mm (278 GHz) at the summit of Mauna Kea in the Hawaiian Islands. A total of 75 days is covered during the period 1983–1986. Observations were made on a quasi-continuous basis, with opacity measured every 20 minutes around the clock for significant periods of time. A conversion from opacity at =1.1 mm to the equivalent preciptable water vapor column is given from the measurements of Zammit and Ade, from which opacities at other wavelengths may be derived. The data presented here supplement those in an earlier paper covering 34 days in the fall of 1982. 相似文献
36.
Zojer E Beljonne D Pacher P Brédas JL 《Chemistry (Weinheim an der Bergstrasse, Germany)》2004,10(11):2668-2680
Quadrupolar-type substitution of pi-conjugated chromophores with donor and acceptor groups has been shown to increase their two-photon absorption (TPA) response by up to two orders of magnitude. Here, we apply highly correlated quantum-chemical calculations to evaluate the impact of the nature of conjugated bridge and the charge-transfer distance on that enhancement. We compare chromophores with phenylenevinylene-, thienylenevinylene-, polyene-, and indenofluorene-type backbones substituted by dimethylamino and cyano groups. In all compounds, we find a strongly TPA-active A(g) state (either 2A(g) or 3A(g)) in the low-energy region, as well as a higher lying TPA-active state (mA(g)) at close to twice the energy of the lowest lying one-photon allowed state; the smaller energy detuning in the mA(g) states results in very large TPA cross sections delta. We also investigate the influence of the degree of ground-state polarization on TPA. Independent of the nature of the backbone and the donor-acceptor separation, delta displays the same qualitative evolution with a maximum before the cyanine-like limit; the highest TPA cross sections are calculated for distirylbenzene- and polyene-based systems. 相似文献
37.
Publications on the binding characteristics of metals with humic acid (HA) are sparse. Here we investigated the release of nickel from Ni(II)-HA complexes using model solutions of three different [Ni(II)]/[HA] mole ratios at three different pH values; we also compared the results with those of [Ni(II)]/[FA] complexes from previous work in this laboratory. Ligand exchange kinetics using the competing ligand exchange method (CLEM) were studied using two different techniques: graphite furnace atomic absorption spectrometry (GFAAS) with Chelex 100 resin as the competing ligand, and adsorptive cathodic stripping voltammetry (AdCSV) with dimethylglyoxime as the competing ligand to measure the rate of dissociation of Ni(II)-HA complexes. The results of the kinetic studies showed that as the [Ni(II)]/[HA] mole ratio was decreased, the rate of dissociation of Ni(II)-HA complexes decreased, and the proportion of free Ni2+ ions plus very labile nickel complexes decreased while the proportion of the less labile kinetically distinguishable components increased. Generally, the rate of dissociation of Ni(II)-HA complexes was slower than that of Ni(II)-FA complexes. Studies on the validity of the kinetic model showed that the concentrations of chemical species varied in a reasonable way with pH and the [Ni(II)]/[HA] mole ratios, indicating that the kinetically distinguishable components have chemical significance and the kinetic model is valid. 相似文献
38.
A comparative quantum-chemical analysis of the electronic structures and spectroscopic parameters of the cycloalkanes C3H6, C4H8, C5H10, and C6H12 and their silicon analogs Si3H6, Si4H8, Si5H10 and Si6H12 was performed in the framework of the SCF MO LCAO method in the INDO approximation. Qualitative interpretation of “abnormal”
ionization potentials and energies of electronic absorption spectra of cyclopolysilanes has been given.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1105–1108, June, 1997. 相似文献
39.
P. Niedzielski M. Siepak B. Dudzińska-Huczuk 《Central European Journal of Chemistry》2003,1(3):314-324
This paper reports the results of an optimisation study for a procedure to determine the total selenium and its inorganic
species, Se(IV) and Se(VI) using atomic absorption spectrometry combined with hydride generation and in-situ trapping of the
analyte on the inner walls of the graphite tube. With the use of the proposed modification, a detection limit (3σ) of 0.018
ng/ml is achieved. This paper presents exemplary results, according to the proposed procedure, for selenium determination
in samples of marine water. The concentrations of selenium in the samples ranged from <0.02 ng/ml to 0.16ng/ml of Se(IV) and
from <0.02 ng/ml to 0.10 ng/ml of Se(VI). 相似文献
40.
流动注射在线阴离子树脂预富集火焰原子吸收测定痕量铜 总被引:10,自引:0,他引:10
研究了以阴离子交换树脂作吸附剂的流动注射在线微柱预富集火焰原子吸收测定铜的新方法。在最佳条件下富集150s,富集23倍,检出限0.2μg/L,RSD为1.6%,分析速度20次/h。天然水样中可能存在的离子不干扰铜的测定。所建立的方法已用于水样中痕量铜的测定。 相似文献