Evaluation of extraction/digestion techniques used to determine lead isotopic composition in forest soils

Lead isotopic studies in soils provide an efficient tool for tracing the sources of lead pollution. Five different extraction/digestion techniques (0.05 M EDTA, 0.5 M HNO₃, 2 M HNO₃, aqua regia, total digestion) were used for lead isotopic composition (²⁰⁶Pb/²⁰⁷Pb) determination in three forest soil profiles with different kinds of prevailing Pb contamination (unpolluted area, smelting area and vicinity of a motorway). The results obtained showed that all extraction/digestion methods used for the determination of ²⁰⁶Pb/²⁰⁷Pb ratios in surface horizons containing high organic matter contents gave statistically identical values (according to the Tukey test). In mineral soil horizons, differences between the individual extraction/digestion methods could be observed (the lowest ²⁰⁶Pb/²⁰⁷Pb ratios were obtained from EDTA extracts, corresponding to weakly bound anthropogenic lead, and the highest ²⁰⁶Pb/²⁰⁷Pb ratios were obtained from total digestion). The combination of total digestion and EDTA extraction (labile lead fraction) seems to be the optimal combination for ²⁰⁶Pb/²⁰⁷Pb ratio determination and optimal result interpretation.     

Synthesis and bio-evaluation of phenothiazine derivatives as new antituberculosis agents

Two series of phenothiazine derivatives were designed and synthesized. All compounds were tested for anti-tuberculosis activities against Mycobacterium tuberculosis H₃₇R_V. In comparison with mother compound of chlorpromazine, compound 6e shows promising anti-tuberculosis activity and much less mammalian cell cytotoxicity, compound 6e merits to be further explored as new anti-tuberculosis agents.     

Duality gap of the conic convex constrained optimization problems in normed spaces

In this paper, motivated by a result due to Champion [Math. Program.99, 2004], we introduce a property for a conic quasi-convex vector-valued function in a general normed space. We prove that this property characterizes the zero duality gap for a class of the conic convex constrained optimization problem in the sense that if this property is satisfied and the objective function f is continuous at some feasible point, then the duality gap is zero, and if this property is not satisfied, then there exists a linear continuous function f such that the duality gap is positive. We also present some sufficient conditions for the property The work of this author was partially supported by the National Natural Sciences Grant (No. 10671050) and the Excellent Young Teachers Program of MOE,  P.R.C.     

Diphenyllead(IV) thiosemicarbazonates and pyrazolonates: Synthesis and characterization

Cyclization of thiosemicarbazones derived from β-keto esters and β-keto amides (HTSC) in the presence of diphenyllead(IV) acetate was explored in methanol solution at room temperature and under reflux. All β-keto ester TSCs underwent cyclization to give the corresponding pyrazolone (HL), which, except in one case, deprotonated and coordinated the PbPh₂²⁺ moiety to form homoleptic [PbPh₂(L)₂] or heteroleptic [PbPh₂(OAc)(L)] derivatives. Cyclization did not occur with β-keto amide TSCs and only [PbPh₂(TSC)₂] or [PbPh₂(OAc)(TSC)] thiosemicarbazonates were isolated. The complexes were characterized by IR spectroscopy in the solid state and by ¹H, ¹³C and ²⁰⁷Pb NMR spectroscopy in DMSO–d₆ solution, in which they evolve and decompose with time. Additionally, crystals of p-acetoacetanisidide thiosemicarbazone (HTSC¹⁰), [PbPh₂(OAc)(L⁵)] · MeOH (HL⁵ = 2,5-dihydro-3,4-dimethyl-5-oxo-1H-pyrazolone-1-carbothioamide), [PbPh₂Cl(L²)] (HL² = 2,5-dihydro-5-oxo-3-phenyl-1H-pyrazolone-1-carbothioamide), [PbPh₂(OAc)(TSC⁸)] · 2MeOH (HTSC⁸ = acetoacetanilide thiosemicarbazone), [PbPh₂(OAc)(TSC¹⁰)] · H₂O and [PbPh₂(OAc)(TSC¹¹)] · 0.75MeOH (HTSC¹¹ = o-acetoacetotoluidide) were studied by X-ray crystallography. The complexes, monomers or dimers with almost linear C–Pb–C moieties, are compared with the corresponding derivatives of Pb(II).     

Induced transmittance in alexandrite laser eye-protectors—a survey of different types of laser filters

Different types of eye-protection filters are examined with the emphasis being laid on the irradiation-dependent spectral transmittance. Most of the dyes used for polycarbonate laser filters show the effect of induced transmittance. This may be critical with respect to eye safety because these absorber types are frequently used in filters for protection against alexandrite laser irradiation.     

A 207Pb NMR study of the adducts of triphenyllead chloride and diphenyllead dichloride

²⁰⁷Pb NMR spectra were used to determine the structure of adducts of triphenyllead chloride and diphenyllead dichloride in CH₂Cl₂ and CH₃CN. The bases included several phosphorus donors, such as tributylphosphine, oxygen donors, such as tributylphosphine oxide, and nitrogen donors, such as pyridine. A number of bidentate bases were also studied. The ²⁰⁷Pb spectra indicate that rapid exchange occurs in the adducts, even at temperatures of ?90 °C. The magnitude of the shift relative to the lead acid indicates that all of the bases, including the bidentate bases, form five‐coordinate adducts with triphenyllead chloride. Diphenyllead dichloride forms six‐coordinate adducts, except for the adduct with tributylphosphine, which is five‐coordinate. This is the first report of a five‐coordinate adduct of diphenyllead dichloride. Copyright © 2003 John Wiley & Sons, Ltd.     

Ionic mobility, ionic transport, and charge transfer mechanism in solid solutions (1 ? x )PbF2- x MF n by the NMR and impedance spectroscopy data

The internal mobility and ionic conduction of solid solutions in systems PbF₂-MF₂ and PbF₂-MF₃ are studied by the NMR (¹⁹F, ²⁷Al, ²⁰⁷Pb) and impedance spectroscopy methods. Factors that define the form of ionic movements and their energy characteristics in the temperature region 150 to 550 K are considered and analyzed. Temperature shifts of the frequency range that defines the ionic conduction of solid solutions are discovered on the basis of impedance spectroscopy data and explained. It is established that the high ionic conductance in lead difluoride doped with fluorides of metals of Groups II and III is caused by the diffusion of fluoride ions. The large values of specific conductance (10⁻⁴ to 10⁻³ S cm⁻¹) at a relatively low activation energy (less than 0.6 eV) allow one to consider the solid solutions studied in the role of a basis for the obtaining of new fluoride materials with high ionic conductance. Original Russian Text ? V.Ya. Kavun, A.B. Slobodyuk, S.L. Sinebryukhov, E.V. Tararako, V.K. Goncharuk, S.V. Gnedenkov, V.I. Sergienko, 2007, published in Elektrokhimiya, 2007, Vol. 43, No. 6, pp. 643–656. Based on the report delivered at the 8th International Meeting on Fundamental Problems of Solid-State Ionics, Chernogolovka (Russia), 2006.     

207Pb-NMR-Untersuchungen an Bleiorganylen

The high-resolution²⁰⁷Pb magnetic resonance spectra ofR _4–n PbX _n (R=Methyl, Ethyl;X=h₁-Cyclopentadienyl, Chloride;n=1, 2) have been studied at 16.72Mc. The²⁰⁷Pb- ·· -¹H spin-spin coupling constants for the molecules described have been obtained by analysis of the first order NMR-patterns as A_xB_yM and A_xB_yC_zM respectively. The experimental spectra have been verified by a computer simulation. The chemical shifts and coupling constants of the lead organyls investigated show similar dependences on moleculare structure as well as number and species of the substituents like analogous organotin compounds.

     

TP—801单板计算机控制凸轮加工

本文介绍了一种用TP—801单板计算机控制的凸轮磨床。分析了加工凸轮的数学原理、控制系统的硬件结构和软件结构。本文还提出了一种控制步进电机按指数规律升降速的方位。本装置已实际使用,有明显的经济效益。