The oxidation state of tungsten in NaxWO3 bronzes as determined by X-ray photoelectron spectroscopy

The XPS spectrum of the 4f levels of W in Na_xWO₃ bronzes is explained by assuming the presence of three oxidation states (W⁶⁺, W⁵⁺ and W⁴⁺). Tetravalent tungsten is formed by dismutation of W⁵⁺. The partial reduction of W⁶⁺ and W⁵⁺. during the recording of XPS spectra is briefly considered.     

NMR experiments on acetals—XXXVII: NMR spectral study of cis-, and trans-6-methyl-4-r-1,3-oxaselenans

The NMR spectral parameters are reported for cis-, and trans-6-Me-4-alkyl-1,3-oxaselenans with the aid of the INDOR- technique. Low temperature studies show the conformational equilibrium in the trans series to be pronouncedly one-sided and a value for the inversion barrier has been obtained.     

A spectroscopic study of cobalt(III) furyldioximates

Summary The electronic properties of a series of cobalt(III)trans-furyldioximato-complexes of the type [CoB(FH)₂X] (B=NH₃, X=Cl, Br, I or NO₂; B=pyridine (py) or thiocarbamide (thio), X=Cl or Br; B=imidazole (imid), X=Br), [Co(FH₂)(FH)Cl₂] and [Co(thio)₂(FH)₂]NO₃ were studied by i.r., u.v. and¹H and¹³C n.m.r. spectra The results were compared with those from the corresponding dimethylglyoximato-complexes. It was concluded that -conjugation over the equatorial plane in the furyldioximates is greater than in the dimethylglyoximates. There is some evidence of thetrans-influence of the anionic ligands in the ammines which are in the order NO ₂ ^– >Br^–>Cl^–.     

The key elements of traceability in chemical measurement: agreed or still under debate?

Talking about "traceability" means talking about a "property of the result of a measurement", about "the value of a standard", about "stated references" and about an "unbroken chain of comparisons". It describes by which comparison, and to which other value, the result of a measurement has been obtained, i.e. is "traceable to". It is about the underlying structure of the measurement process of the result of a measurement and therefore about the authority of the result. Since values carried by (certified) reference materials have also been obtained by measurement, the definition of traceability equally applies. Traceability in the context of reference materials is also about the authority of the values carried by the (certified) reference materials and is, therefore, of key importance for the authority of the reference materials themselves. Hence, values of results of measurements constitute part of the traceability chain and their uncertainties are an intrinsic accompanying phenomenon. Uncertainties need a traceability chain against which they can be evaluated, and a traceability chain is an a priori requirement for evaluating the uncertainty budget of a measurement result. An attempt has been made to exemplify "traceability" chains in some types of chemical measurement and to identify the degree of international agreement on the key elements of "traceability". It is concluded that there is less than universal agreement on this issue. The debate should continue in order to arrive at the international understanding and agreement needed, as "traceability" is now being incorporated in the International Organization for Standardization (ISO), the International Laboratory Accreditation Co-operation (ILAC) and in other "guiding" or regulatory documents. It is also the reason why the Institute for Reference Materials and Measurements (IRMM) has taken up the study of the concept in its core programme on Metrology in Chemistry, and why it sponsored the Workshop in Bratislava.     

N,N-二甲基甲酰胺中电沉积制备镁镍储氢合金

采用恒电位沉积法, 选用适宜的添加剂和络合剂, 成功地从N,N-二甲基甲酰胺(DMF)中沉积出致密的黑色Mg-Ni储氢合金膜. 并初步探讨了其共沉积机理. XRD显示沉积层中含有非晶态Mg-Ni相和微晶态Mg相. SEM图及相应能谱图分析表明合金颗粒以团聚状态存在, 合金成分不是很均匀. AAS分析表明沉积合金中Mg的原子摩尔分数达27.3%. LAND电池测试系统测得所镀合金膜的放电比容量最高为172.4 mAh/g.     

一种新型的表面声波阻抗传感器及其在液相体系中的应用

一种新型的表面声波阻抗传感器及其在液相体系中的应用姚守拙，陈康，刘德忠，聂利华（湖南大学化学化工系，长沙，４１００８２）关键词表面声波，阻抗传感器，液相应用表面声波传感器（ＳＡＷＳ）具有较高的灵敏度和检测精度，已广泛应用于气体微量组分分析、色谱检测和...     

Natural radionuclide-free phosphoric acid production

High-uranium phosphate rock from Itataia, Brazil, was milled for wet-process phosphoric acid production using the dihydrate method. Uranium contained in the phosphoric acid was recovered by solvent extraction. The distribution of long-lived natural radionuclides of the ²³⁸U and ²³²Th decay series involved in these operations was evaluated. ²²⁶Ra, ²²⁸Ra and ²¹⁰Pb were found to predominate in the phosphogypsum, while ²²⁸Th, ²³⁰Th and ²³²Th in the uranium-free phosphoric acid. Thorium is removed from the phosphoric acid by solvent extraction to produce a NORM-free phosphoric acid.     

Elemental concentration in the cortex and hippocampus of Wistar rats by X-ray total reflection fluorescence with synchrotron radiation

Summary The study of trace element levels is of great importance due to their relevance in agingand several neurodegenerative diseases. This work compares the elemental concentrations in different postnatal ages and between the temporal cortex, entorhinal cortex and hippocampus from Wistar rats, using X-ray total reflection fluorescence with synchrotron radiation. Ten elements were determined in brain samples: Ti, Cr, Mn, Fe, Cu, Zn, (at trace level) and P, S, Cl and K (at major levels). The elements that increased with aging in cortical areas were: S, K, Fe, Cu and Zn. Ca and Zn levels decreased with advancing age in the hippocampus. In addition to this, Ti, Mn and Fe levels were more conspicuous in the entorhinal cortex.     

Bioaccumulation of vanadium in the epiphytic lichen Parmelia caperata from Liguria (north-west Italy)

The concentration of vanadium was measured in 35 samples of the epiphytic lichen Parmelia caperata collected along the coast of the Ligurian Sea (Italy), in order to detect the possible bioaccumulation of vanadium due to a huge crude oil burning occurred in that area in 1991. The cartographic elaboration of data shows a pattern of distribution of vanadium concentrations according to different degrees of deviation from background condition, showing that 8 years later memory of the accident is still detectable in foliose lichen thalli.     

Conformational Study of Naringenin in the Isolated and Solvated States by Semiempirical and Ab Initio Methods

Naringenin is a natural widespread flavanone occurring in different foodstuffs that presents several important biological activities. Although its properties are well documented, its mechanisms of action are still controversial. The present article reports a conformational analysis of naringenin, using the semiempirical AM1 and ab initio methods, at the Hartree–Fock level of theory. The 3-21G, 3-21G*, 6-31G, and 6-31G** basis sets were used. The electron correlation effects were included through the Møller–Plesset second-order perturbation theory. The solvation of naringenin has been investigated through the standard SCRF, the supermolecule (SM), and the combined SM/SCRF models. The results have shown that there are two degenerate forms of naringenin, differing mainly by the orientation of a hydroxyl group (C4—OH). The energy barrier for the interconversion between them is ca. 6 kcal.mol^–1, suggesting some conjugation between the -system of the aromatic B ring and the hydroxyl group (C4—OH).