The limit-periodic finite-difference operator onl 2(ℤ) associated with iterations of quadratic polynomials

The limit-periodic discrete operator of the Schrödinger type on the axis associated with iterations of quadratic polynomials is investigated. It is proved that this operator has a singularly continuous simple spectrum. Connections with the Sinai-Bowen-Ruelle measure and the conformai map onto a special comblike domain are established.     

Trägerfixierte Organometallkomplexe. IV. Strukturuntersuchungen an neutralen und kationischen (Ether-phosphan)palladium(II)-Komplexen

Supported Organometallic Complexes. IV. Structural Investigations on Neutral and Cationic (Ether-phosphane)palladium(II) Complexes . Reaction of the (ether-phosphane) ligands PhP(R)CH₂—D ( 2a?c ) [D=CH₂OCH₃: R=Ph ( a ), (CH₂)₃Si(OCH₃)₃ ( b ), (CH₂)₃SiO_3/2 ( b ′); D= R=(CH₂)₃Si(OCH₃)₃ ( c ), (CH₂)₃SiO_3/2 ( c ′)] with Cl₂Pd(COD) ( 1 ) results in the formation of Cl₂Pd(P — O)₂ ( 3a?c ). Cleavage of Cl^? from 3 with AgSbF₆ yields the cationic, monochelated complexes [ClPd(P — O)(P ∩ O)]⁺ ( 4 a—c ) (P — O: η¹-P-coordinated; P ∩ O: η²-O ∩ P-coordinated). 4 a crystallizes in the monoclinic space group P2₁/c with the lattice constants a=1 062,4(2), b=1 912,2(4) und c=1 635,5(3) pm, β=101,22(3)° and Z=4 (R=0,0341; R_w=0,033). With water 3 b, c and 4 b, c are subjected to polycondensation to give the supported complexes 3 b′, c′, 4 b′, c ′. The structure 3 b′, c′, 4 b′, c ′ is investigated by comparison of their ³¹P CP MAS data with the ³¹P{¹H} NMR spectra of their soluble precursors 3 b, c, 4 b, c . ¹³C CP MAS NMR spectra of 3 b′, c ′ and 4 b′, c ′ indicate η¹-P- and η²-O ∩ P-coordination of the ligands. The polysiloxane network of 4 b ′ was inspected by contact time variation of the ²⁹Si CP MAS NMR spectra and it appeared that 77% of the Si—O units are crosslinked, corresponding to a ratio T₄:T₃:T₁=67:100:10.     

Determination of arsenic,selenium and mercury in an estuarine sediment standard reference material using flow injection and atomic absorption spectrometry

A flow-injection analysis atomic absorption spectrometric (FIA-AAS) method was developed for the determination of trace amounts of arsenic, selenium and mercury in a proposed estuarine sediment standard reference material (SRM 1646a). The samples were prepared in two manners: a) A wet digestion procedure with HNO₃, H₂SO₄, and HClO₄ using a reflux column and b) A microwave-oven digestion procedure utilizing HNO₃, H₂SO₄, and HCl for As and Se, and HNO₃ for Hg. Microwave-oven digestion provides results comparable to those found by reflux column digestion and reduces the sample preparation time by a factor of 10. The proposed method employing the microwave-oven digestion procedure coupled with FIA-AAS for As and Se, and FIA-CVAAS for Hg, has detection limits of 0.15 ng As/ml, O.17 ng Se/ml and 0.15 ng Hg/ml.On leave from the Defense Metallurgical Research Laboratory, Hyderabad, India     

Application of an on-line preconcentration system in simultaneous ICP-AES

A PC-controlled on-line preconcentration system (TRACECON) developed by Knapp et al. [11], was connected to a JY-70 Plus simultaneous ICP spectrometer to preconcentrate on-line seven trace elements (Cu, Fe, Zn, Cr, Ni, Mn, V) in biological and environmental samples. EDTrA-cellulose was used as column material. The elemental concentrations were determined by simultaneous ICP-AES. The effect of pH of the sample solution on the enrichment was studied. It was found that the recoveries of chromium and iron depend strongly on the pH of the sample solution. All the elements mentioned were recovered quantitatively at pH 4.0±0.1. The flow rates of sample solution and element solution were optimized. The enrichment factors for seven elements at 5 ml loading volume range from 3.9 for Cu to 7.9 for Zn. The detection limits of all seven elements were improved. The accuracy of the method was tested by the analysis of a number of CRMs of NIST, BCR and NIES. Most results are in good agreement with the certified values.On leave from Shanghai Institute of Metallurgy, Academia Sinica, Shanghai 200050, People's Republic of China     

X-射线荧光光谱背景和基体效应综合校正公式

本文根据散射内标和公共背景法的有关理论,导出了两个X-射线荧光光谱分析校正方程,将背景、基体吸收和重叠干扰校正,以及校正曲线定量分析等多种运算合并进行,因而应用起来十分简便,两个方程在数学形式上与目前使用的X-射线光谱仪计算机程序中通用的数学模型相似,便于推广应用。     

镧与L-酪氨酸和甘氨酸三元固态配合物的热化学研究

由于稀土元素镧与氨基酸形成的配合物具有抗癌、抗肿瘤活性 ,人们对稀土氨基酸配合物的研究产生了浓厚兴趣。有关这类配合物的制备和表征的研究较多[1～ 4] ,而对其热化学性质的研究较少。我们按文献[5] 方法合成了配合物Ｌａ(Ｔｙｒ)(Ｇｌｙ) 3Ｃｌ3·3Ｈ2 Ｏ(ｓ) ,在自行研制的具有恒定温度环境反应热量计上 ,分别测定了Ｌａ2 Ｏ3(ｓ)、氨基酸 [Ｌ 酪氨酸 (Ｌｙｒ) +甘氨酸 (Ｇｌｙ) ]和配合物在2ｍｏｌ·Ｌ- 1 ＨＣｌ溶液中的溶解焓 ,通过设计的热化学循环得出配合反应焓 ,进而计算出Ｌａ(Ｔｙｒ)(Ｇｌｙ) 3Ｃｌ3·3Ｈ2 Ｏ(ｓ)的标准摩尔…     

Analysis of individual natural pyrethrins in indoor matrices by HRGC/ECD

An HRGC/ECD method is presented which permits the identification and quantitation of individual components of pyrethrins (cinerin I, jasmolin I, pyrethrin I, cinerin II, jasmolin II, pyrethrin II) in indoor matrices (airborne particles, house dust) after application of an agent containing pyrethrum. In order to prepare calibration standards for the individual components of the pyrethrum extract, the pyrethrins were isolated hy semi-preparative HPLC and their content and purity were determined by ¹H-NMR spectroscopy.     

紫外分光光度计标准溶液的制备及使用

介绍了紫外分光光度计标准溶液的特性及其用于检定紫外分光光度计准确度的优点和正确的使用方法。     

Micellization of dodecyldimethylethyl- ammonium bromide in aqueous solution

Specific conductivity of aqueous solutions of dodecyldimethylethylammonium bromide has been determined in the temperature range of 15-40°C. The critical micelle concentration (cmc) and ionization degree of the micelles, b, were determined from the data. Thermodynamic functions, such as standard Gibbs free energy, ΔG _m°, enthalpy, ΔG _m°, and entropy, ΔG _m°, of micellization, were estimated by assuming that the system conforms to the mass action model. The change in heat capacity upon micellization, ΔG _m°, was estimated from the temperature dependence of ΔG _m°. An enthalpy-entropy compensation phenomenom for the studied system has been found. This revised version was published online in July 2006 with corrections to the Cover Date.     

高效毛细管电泳测定混合氯化稀土中的稀土元素

研究了在以含有紫外吸收的咪唑为背影电解质和以α－羟基异丁酸为络合剂的缓冲液体系中，用毛细管电泳间接外法检测和然土离子的方法，讨论了各操作条件对稀土离子分离泊影响。