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31.
Yunhui Zhai Xijun Chang Yuemei Cui Ning Lian Shoujun Lai Hong Zhen Qun He 《Mikrochimica acta》2006,154(3-4):253-259
A rapid, selective method that utilize 4-(2-Pyridylazo)-resorcinol (PAR)-modified nanometer SiO2 (nanometer SiO2–PAR) as a new solid-phase extractant for preconcentration of trace mercury (II) has been developed. The adsorption property
of nanometer SiO2–PAR for metal ions was studied by selectively extracting different metal ions from aqueous solutions. The results revealed
an excellent affinity of the nanometer SiO2–PAR for mercury (II) in presence of interfering metal ions at pH 4. The main parameters of solid-phase extraction such as
shaking time, elution and sample dilution effect were studied. The extractant shows rapid kinetic sorption, and the adsorption
equilibrium of mercury (II) on nanometer SiO2–PAR was achieved in less than 2 min. The adsorbed mercury (II) was easily eluted by 4 mL of 6 mol L−1 HCl. The maximum preconcentration factor was 50. The maximum static adsorption capacity was 276 μmol g−1 at pH 4. The detection limit (3σ) was 0.43 μg L−1 for cold vapor atomic absorption spectrometry (CVAAS), and the relative standard deviation of the eight replicate determinations
was 2.4% for the determination of 2.0 μg of Hg(II) in 100 mL water sample. The method was applied to the determination of
trace mercury (II) in sample solutions with satisfactory results. 相似文献
32.
Chen L Jiang F Lin Z Zhou Y Yue C Hong M 《Journal of the American Chemical Society》2005,127(24):8588-8589
A blue luminescent tetradecavanadate compound, [Et4N]5[V14O36Cl], has been synthesized. It possesses an unprecedented half-open basket framework. Through the {ABAB}-type stacking, the {V14O36} clusters form infinite one-dimensional channels with considerable accessible volume in the crystalline state. 相似文献
33.
34.
Rusin O St Luce NN Agbaria RA Escobedo JO Jiang S Warner IM Dawan FB Lian K Strongin RM 《Journal of the American Chemical Society》2004,126(2):438-439
The determination of cysteine and homocysteine levels is of great current interest for the monitoring of desease states. A new colorimetric method for the simultaneous detection of l-cysteine and l-homocysteine has been developed. A fluorescein derivative reacts with the above amino acids, producing their respective thiazolidines resulting in color changes. Interference from other amino acids and proteins is minimal. 相似文献
35.
Fe-Co-Ni合金纳米线有序阵列的模板合成与磁性 总被引:10,自引:0,他引:10
以二次阳极氧化的氧化铝膜为模板,用电化学沉积的方法成功地合成了Fe-Co-Ni三组份有序纳米线阵列.扫描电子显微镜(SEM)和透射电子显微镜(TEM)观察表明纳米线表面光滑、有序、高长径比;磁性测量表明,其矫顽力较同组份的膜材料有较大的提高.将样品在惰性气体氛围中不同温度下退火,随着退火温度增加,其纵向矫顽力有一个极值,而对应的横向矫顽力没有类似的变化,关于这一现象的机理,本文进行了初步的讨论. 图5参15 相似文献
36.
固相微萃取参数选择及其对有机锡分析的影响 总被引:1,自引:0,他引:1
固相微萃取是一种新型的、不断发展和完善的样品前处理方法,它与其它技术联用可对多种样品基体中挥发、半挥发性有机化合物进行测定。目前,该技术在毒性金属有机化合物中的应用很少。本文分析参数选择对固相微萃取的影响的同时,还对其在有机锡化合物分析中的应用作了综述。 相似文献
37.
Bong H. Lian 《Communications in Mathematical Physics》1994,163(2):307-357
Inspired by a recent work of Frenkel-Zhu, we study a class of (pre-)vertex operator algebras (voa) associated to the self-dual Lie algebras. Based on a few elementary structural results we propose thatV, the category of Z+-graded prevoasV in whichV[0] is one-dimensional, is a proper setting in which to study and classify simple objects. The categoryV is organized into what we call the minimalk
th types. We introduce a functor —which we call the Frenkel-Lepowsky-Meurman functor—that attaches to each object inV a Lie algebra. This is a key idea which leads us to a (relative) classification of thesimple minimal first type. We then study the set of all Virasoro structures on a fixed minimal first typeV, and show that they are in turn classified by the orbits of the automorphism group Aut((V)) in cent((V)). Many new examples of voas are given. Finally, we introduce a generalized Kac-Casimir operator and give a simple proof of the irreducibility of the prolongation modules over the affine Lie algebras. 相似文献
38.
Y. Lian H. Gao S. X. Dou H. Wang P. Ye Q. Guan J. Wang 《Applied physics. B, Lasers and optics》1994,59(6):655-658
Mechanism transitions of Self-Pumped Phase Conjugation (SPPC) with wavelength and doping concentration are observed in KTN:Fe (KTa1 –x
Nb
x
O3:Fe with
x
= 0.48) crystals. The SPPC mechanism in KTN: Fe (0.4 wt. %) crystal transforms from Stimulated Photorefractive Backscattering and Four-Wave Mixing (SPB-FWM) to cat (or total internal reflection) as the wavelength increases from 514.5 nm to 620 nm. SPPC at 514.5 nm is formed with the cat mechanism in a 0.2 wt. % doped KTN:Fe crystal, while with the SPB-FWM mechanism in a 0.4 wt. % doped one. These mechanism transitions are discussed with respect to the dependence of the backscattering gain coefficient of the crystals on wavelength and doping concentration. 相似文献
39.
Hongmin Liu Xiaojiang Ye Zhiwei Lian Yuangao Wen Wenfeng Shangguan 《Research on Chemical Intermediates》2006,32(1):9-16
Formaldehyde is one of the most harmful pollutants that endanger occupants' health and the way of its effective removal has
become a focus in the field of air quality. This paper studies the static photocatalytic removal of formaldehyde experimentally
and finds out that carbon monoxide, which is more harmful to occupants' health than the formaldehyde itself, is one of the
by-products in the process of photocatalytic oxidation of formaldehyde. The increase of carbon monoxide concentration should
be taken into consideration in the photocatalytic application. The photocatalyst surface at room temperature can weakly adsorb
CO and CO2, which can deactivate the photocatalysts. 相似文献
40.
Lysophosphatidic acid (LPA, 1- or 2-acyl-sn-glycerol 3-phosphate) displays an intriguing cell biology that is mediated via interactions both with G-protein coupled seven transmembrane receptors and with the nuclear hormone receptor PPARgamma. Synthesis and biological activities of fluorinated analogues of LPA are still relatively unknown. In an effort to identify receptor-selective LPA analogues and to document in detail the structure-activity relationships of fluorinated LPA isosteres, we describe a series of monofluorinated LPA analogues in which either the sn-1 or the sn-2 hydroxy group was replaced by fluorine, or the bridging oxygen in the monophosphate was replaced by an alpha-monofluoromethylene (-CHF-) moiety. The sn-1 or sn-2 monofluorinated LPA analogues were enantiospecifically prepared from chiral protected glycerol synthons, and the alpha-monofluoromethylene-substituted LPA analogues were prepared from a racemic epoxide with use of a hydrolytic kinetic resolution. The sn-2 and sn-1 fluoro LPA analogues were unable to undergo acyl migration, effectively "freezing" them in the sn-1-O-acyl or sn-2-O-acyl forms, respectively. The alpha-monofluoromethylene LPA analogues were unique new nonhydrolyzable ligands with surprising enantiospecific and receptor-specific biological readouts, with one compound showing a 1000-fold higher activity than native LPA for one receptor subtype. 相似文献