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51.
The synthesis and spectroscopic studies of a convex bis-porphyrin based molecular tweezer are reported. The complexation of small bidentate ligands by metallated derivatives of the bis-porphyrin host were monitored through UV–visible and 1H NMR spectroscopy and yielded large association constants. 相似文献
52.
In the nano-aerosol mass spectrometer, individual particles in the 10–30 nm size range are trapped and irradiated with a high pulse energy laser beam. The laser pulse generates a plasma that disintegrates the particle into atomic ions, from which the elemental composition is determined. Particle-to-particle variations among the mass spectra are shown to arise from plasma energetics: Low ionization energy species are enhanced in some spectra while high ionization energy species are enhanced in others. These variations also limit the accuracy and precision of elemental analysis, with higher deviations generally observed when low ionization energy species are dominant in the mass spectrum. For standard datasets generated from nominally identical particles, it is shown that that the error associated with composition measurement is random and that averaging the spectra from a few tens of particles is sufficient for measuring the mole fractions of common elements to within about 10 % of the expected value. Averaging a greater number of particles offers limited improvement of the measurement precision but has the deleterious effect of degrading the measurement time-resolution, which is given by the time needed to obtain the required number of particle spectra for averaging. An internally mixed ambient particle dataset was found to give a similar result to the standard datasets, that is, the measured elemental composition converged to the average value after a few tens of particles were averaged. 相似文献
53.
The monolayer behavior of long-chain fatty acids at the air/water interface on a poly(ethyleneimine) containing subphase was investigated. The interaction of the polymeric gegenions in the subphase leads to expanded states and permits the visualization of the aggregation behavior of different long-chain fatty acids via fluorescence microscopy. The monolayer morphologies and their variability were intensively studied by fluorescence microscopy. In addition, the transfer of the complexed fatty acid monolayers to solid substrates has been investigated. 相似文献
54.
Harry J. Whitlow Margaretha Andersson Mikael Hult Leif Persson Mohamed El Bouanani Mikael Östling Carina Zaring Nils Lundberg David D. Cohen Nick Dytlewski Peter N. Johnston Ian F. Bubb Scott R. Walker Erik Johanson Sture Hogmark P. Anders Ingemarsson 《Mikrochimica acta》1995,120(1-4):171-181
Recoil Spectrometry covers a group of techniques that are very similar to the well known Rutherford backscattering Spectrometry technique, but with the important difference that one measures the recoiling target atom rather than the projectile ion. This makes it possible to determine both the identity of the recoil and its depth of origin from its energy and velocity, using a suitable detector system. The incident ion is typically high-energy (30–100MeV)35C1,81Br or127I. Low concentrations of light elements such as C, O and N can be profiled in a heavy matrix such as Fe or GaAs. Here we present an overview of mass and energy dispersive recoil Spectrometry and illustrate its successful use in some typical applications. 相似文献
55.
Joanne E. Stanley Anthony C. Swain Kieran C. Molloy David W. H. Rankin Heather E. Robertson Blair F. Johnston 《应用有机金属化学》2005,19(5):644-657
Perfluoroalkytin compounds R(4−n)Sn(Rf)n (R = Me, Et, Bu, Rf = C4F9, n = 1; R = Bu, Rf = C4F9, n = 2, 3; R = Bu, Rf = C6F13, n = 1) have been synthesized, characterized by 1H, 13C, 19F and 119Sn NMR, and evaluated as precursors for the atmospheric pressure chemical vapour deposition of fluorine‐doped SnO2 thin films. All precursors were sufficiently volatile in the range 84–136 °C and glass substrate temperatures of ca 550 °C to yield high‐quality films with ca 0.79–2.02% fluorine incorporation, save for Bu3SnC6F13, which incorporated <0.05% fluorine. Films were characterized by X‐ray diffraction, scanning electron microscopy, thickness, haze, emissivity, and sheet resistance. The fastest growth rates and highest quality films were obtained from Et3SnC4F9. An electron diffraction study of Me3SnC4F9 revealed four conformations, of which only the two of lowest abundance showed close F Sn contacts that could plausibly be associated with halogen transfer to tin, and in each case it was fluorine attached to either the γ‐ or δ‐carbon atoms of the Rf chain. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
56.
57.
D. W. Holt Kirsty Denny Terry Lee Atholl Johnston 《Accreditation and quality assurance》2001,6(9-10):405-408
Most medical laboratories measure the immunosuppressive drug cyclosporin using one of a number of commercial immunoassays, or high-performance liquid chromatography (HPLC). The calibration of these assays is based on material supplied by the kit manufacturers or prepared in-house. We have examined inaccuracy for the measurement of cyclosporin in samples spiked to known concentrations and the impact of any inaccuracy on the results for cyclosporin measurement in pooled samples from patients prescribed the drug. The data were from the International Cyclosporin Proficiency Testing Scheme, based on aliquots of cyclosporin-free blood to which known amounts of the drug had been added or aliquots of pooled samples collected from patients receiving cyclosporin. Compared with the results using HPLC, the immunoassays had a median bias which ranged from –4.5% to 8.2% for the spiked samples. When pooled samples from patients were analysed the percentage difference from the measured HPLC value, allowing for assay inaccuracy, was as high as 29.9%. It is concluded that inaccuracy is a factor in between-assay performance for this measurement and that proficiency testing schemes should attempt to put more emphasis on this aspect of assay performance. 相似文献
58.
R Johnston S Brignall L Fitzgerald 《The Journal of the Operational Research Society》2002,53(3):256-262
Performance measurement systems along the lines of the EFQM and the balanced scorecard have developed rapidly in recent years, and now occupy much management time and effort. There is limited evidence that performance improvement has received proportionate attention. Six organisations selected for their success were studied using a grounded theory approach based on interviews with management accountants and operations managers in each of the organisations. It is clear that they are all making strenuous efforts to use their performance measurement systems but with a focus on the ‘good enough’ rather than the detail. This gave managers in these organisations the time and space to concentrate on the use of performance measures on forward looking relevance, understanding and action, rather than retrospective and detailed control. This approach was promoted by senior managers and was based on their ability to see the business in simple terms and their understanding of the key drivers of business performance. 相似文献
59.
[reaction] A self-complementary V-shaped bis-porphyrin cavity has been synthesized that is capable of dimerization to form a capsule structure. Self-assembly of the dimer occurs via metal ion coordination and produces an internal volume for guest encapsulation. 相似文献
60.
Constable EC Eich O Fenske D Housecroft CE Johnston LA 《Chemistry (Weinheim an der Bergstrasse, Germany)》2000,6(23):4364-4370
Metallostars are complexes in which a single branching site bears a number of metallated arms. Although they are related to metallodendrimers, they have the advantage of being capable of extending in an unlimited sense; in contrast to metallodendrimers, steric interactions decrease with increasing generation number. In this paper a series of polyalkyne stars with four and six arms, based upon a single tetrahedral carbon core and a benzene core, respectively, are reported and their reactions with [Co2(CO)8] to give metallostars that contain multiple [C2Co2(CO)6] motifs are described. 相似文献