Extraction of iridium(IV) from hydrochloric acid media with crown ether in chloroform, and its determination by ICP–AES

A new method for the quantitative extraction and determination of trace amounts of iridium from hydrochloric acid media has been established based on the formation of an ion-association complex of iridium hexachloro anion IrCl₆ ^2– with dicyclohexyl-18-crown-6 (DC18C6) oxonium cation in chloroform, then determination by inductively coupled plasma atomic emission spectrometry (ICP–AES). The effect of various factors (solvent, acid concentration, crown ether, reagent concentration, shaking time, composition of the extracted species, foreign ions, etc.) on the extraction and back-extraction of iridium has been investigated. The procedure was used to determine traces of iridium in palladium chloride and rhodium chloride.     

Synthesis and physical properties of LiBC intermetallics

Polycrystalline samples of LiBC compounds, which were predicted as possible candidate for high-T_c superconductivity, have been synthesised by a flux method for a wide range of flux compositions Li_xBC (x=0.5-2.4). Scanning electron microscopy and X-ray diffraction patterns showed a plate-like morphology and a single-phase nature of LiBC samples for the starting flux composition of Li_1.25BC. The lattice constants a, c display a systematic variation with x and a maximum volume of the hexagonal unit cell at x=1.25. Electrical resistivity measurements revealed an extrinsic semiconducting behaviour of the single-phase LiBC with an activation energy of 18 meV and a maximum specific resistivity of 2.5 Ω cm at 300 K. In contrast to the theoretical prediction of high T_c, no superconducting features were detected down to 2 K both, by measurements of electrical resistivity and magnetic susceptibility. However, the results do not allow to refute the theoretical prediction because of the lack of accurate chemical analysis methods for the LiBC compounds synthesised.     

Development of long-lifetime metal-ligand probes for biophysics and cellular imaging

Metal-ligand complexes containing ruthenium, osmium, or rhenium display a high photostability, with polarized emission and decay times from 100 ns to 100 Μs. Such probes have considerable potential in biophysics, clinical chemistry, and fluorescence microscopy. In this review we sumrecent developments from this laboratory on the spectral properties of conjugatable metalligand complexes. We also suggest how improved probes can be developed based on the selection of organic ligands.     

Markovnikov versus anti‐Markovnikov addition and C–H activation: Pd–Cu synergistic catalysis

Copper‐ and palladium‐mediated transmetalation and coupling reactions are the backbone to several synthetic methodologies in organic chemistry for C–C bond formation. Computer‐aided simulations using density functional theory (DFT) (B3LYP‐D3 functional with 6‐31G** and effective core potential (ECP)‐LACVP** for heavy atoms for optimizations and cc‐pVTZ(?f) and ECP‐LACV3P** for single‐point calculations) was used to shed light on the probable mechanism of a novel synergistic Cu/Pd catalysts for the coupling of alkene, (Bpin)2 (where, pin = pinacolate), and vinyl‐ or aryl‐halogenated analogues. Every single conceivable pathway was carefully contemplated, and the base minimum energy pathway was found effectively. The copper‐catalyzed nucleophilic generation yields anti‐Markovnikov product using styrene as an alkene. This study affirms quantitatively and accurately how the reaction proceeds and at which steps of the synergistic catalysis the demand of the transmetalation and nucleophile formation for the C–C coupling using phosphine ligands arise. We conclude that the E and Z selectivity depends on the stereochemistry of the substrates used.     

Determination of aluminum in environmental and biological samples by reversed-phase high-performance liquid chromatography via pre-column complexation with morin

Morin was used as a pre-column reagent for the determination of aluminum by RP-HPLC with fluorescence detection. This method has been successfully applied to direct determination of trace Al in environmental and biological samples. The response was linear from 6 x 10(-9) to 6 x 10(-5) M with a detection limit of 2 x 10(-9) M. In addition, the different Al complexes with morin were separated by the proposed HPLC procedure and their coordination ratios were depicted by molar-ratio method. The results showed that 1:1 and 2:1 Al-morin complexes formed.     

新疆大学大学生营养知识态度行为的调查

目的了解新疆大学大学生营养知识、膳食态度、膳食结构和行为现况及存在的问题,为今后开展营养教育的设计及干预提供科学依据.方法采用自行设计的营养知识等方面的问卷,对新疆大学在校的2859名不同生源地,一～三年级不同专业男、女大学生中进行营养知识,膳食态度与膳食结构和行为的抽样调查.结果学生营养知识方面42.4%学生合格,其中男生39%、女生45.8%,膳食态度方面合格率达到72.2%,其中男生62.1%、女生82.3%,膳食结构和行为合格率57.9%,其中男生51.6%、女生64.6%.结论多数学生缺乏必要的营养知识,学生正确营养态度形成率均不高,如：不吃早餐、吃零食等行为较普遍,早餐及各类食物营养价值的有关知识欠缺,膳食结构及行为存在严重的不合理性,尤以农村生源学生及二,三年级学生为重,但有较好的健康饮食意识,他们接受营养知识的态度较好,愿意接受更多的营养知识并改正不良的饮食习惯,应采取多种措施加强对大学生营养知识的宣传教育和营养健康教育,纠正不良饮食行为,引导养成合理膳食行为,尤其是对来自农村学生及女生中针对性的进行膳食营养健康教育及干预十分必要.     

用不同散射角模拟研究石蜡厚度响应初探

为改进检测油垢厚度方法,本文用石蜡模拟油垢,用γ射线垂直照射距源为25cm处的石蜡样品.在与石蜡样品25 cm的距离处,以不同的散射角和同一探测立体角接收散射光子数.发现散射γ光子计数与被测石蜡厚度之间存在不同的线性关系.本实验测得最佳线性相关系数平方值为0.9859,平均测量精度为2.14 mm.     

On the deduction of chemical reaction pathways from measurements of time series of concentrations

We discuss the deduction of reaction pathways in complex chemical systems from measurements of time series of chemical concentrations of reacting species. First we review a technique called correlation metric construction (CMC) and show the construction of a reaction pathway from measurements on a part of glycolysis. Then we present two new improved methods for the analysis of time series of concentrations, entropy metric construction (EMC), and entropy reduction method (ERM), and illustrate (EMC) with calculations on a model reaction system. (c) 2001 American Institute of Physics.     

A novel chronometry technique for dating irradiated uranium fuels using Cm isotopic ratios

Journal of Radioanalytical and Nuclear Chemistry - A novel chronometry method is developed to date irradiated nuclear fuels. It is based on the measurement of two Cm isotopic ratios (244Cm/246Cm...