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A. R. Byrne C. Camara-Rica R. Cornells J. J. M. de Goeij G. V. Iyengar G. Kirkbright G. Knapp R. M. Parr M. Stoeppler 《Fresenius' Journal of Analytical Chemistry》1987,326(7):723-729
Summary In the original intercomparisons two of the IAEA's reference materials, milk powder A-11 and animal muscle H-4, gave unsatisfactory results, with a wide spread of values for many trace elements of interest, and subsequently the recommended values for Cu and Mn in A-11 have been questioned.In the present work, efforts to improve the status of these two materials through a co-ordinated research programme involving a small group of experienced laboratories is described. The elements chosen were As, Cd, Co, Cr, Cu, Hg, I, Mn, Mo, Ni and Pb, and the techniques used were neutron activation analysis (NAA), atomic absorption spectroscopy (AAS) in various modes, inductively coupled plasma emission spectroscopy (ICP), electrochemical methods, and also for iodine, a catalytic method.The results show a satisfactory measure of concordance for most of the elements (in marked contrast to the original results), and allow proposals to be made for revision of the recommended values. Only in the case of Ni and Pb (where NAA data are not available) is the position not fully resolved.Deceased on July 8th, 1984 相似文献
84.
Edward W. Stuebing John H. Weare Robert G. Parr 《International journal of quantum chemistry》1977,11(1):81-102
Following Kohn (reference 4), Schlosser and Marcus (reference 3), and Weare and Parr (reference 2), an energy functional is defined for a molecular problem which is stationary in the neighborhood of the exact solution and permits the use of trial functions that are discontinuous. The functional differs from the functional of the standard Rayleigh–Ritz method in the replacement of the usual kinetic energy operators T?(μ) with operators T?′(μ) = T?(μ) + Î(μ), where Î(μ) generates contributions from surfaces of nonsmooth behavior. If one uses the ?Ψ · ?Ψ way of writing the usual kinetic energy contributions, one must add surface integrals of the product of the average of ?Ψ and the change of ?Ψ across surfaces of discontinuity. 相似文献
85.
Effective kinetic resolutions of acyclic allylic acetates and benzoates have been obtained using a palladium/(S)-BINAP(S) catalyst system. Unusually large preferences for the formation of branched alkylation products from 3-but-2-enyl and crotyl substrates have been observed. [reaction: see text] 相似文献
86.
Particle suspension matrices have been successfully utilized for the analysis of tetracycline antibiotics by thin-layer chromatography-matrix-assisted laser desorption ionisation-time-of-flight mass spectrometry (TLC-MALDI-TOF-MS). Particles of different materials and sizes have been investigated (Co-UFP, TiN, TiO2, Graphite and Silicon) by applying particle suspensions to eluted TLC plates. Mass spectra and mass chromatograms have been recorded directly from the TLC plates. Strong cationization by sodium and potassium was obtained in the positive ion mode, with [M+Na-NH3]+ ions being the predominant signals. The TLC-MALDI mass spectra recorded from graphite suspensions showed the lowest background noise and the highest peak intensities from the range of suspension matrices studied. The mass accuracy from graphite films was improved by adding the peptide Phe-Phe to the graphite suspensions. This allowed internal recalibration of the TLC-MALDI mass spectra acquired during a run. One major potential advantage of TLC-MALDI-TOF-MS has been demonstrated in the analysis of chlortetracycline and tetracycline in a mixture of oxytetracycline, chlortetracycline, tetracycline and minocycline. Examination of the TLC plate prior to MALDI analysis showed only an unresolved spot for chlortetracycline and tetracycline. However by investigation of the MALDI mass spectra and plotting of single ion chromatograms separate peaks for chlortetracycline and tetracycline could be obtained. 相似文献
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Noncircular jets in combustion systems 总被引:1,自引:0,他引:1
E. Gutmark K. C. Schadow T. P. Parr D. M. Hanson-Parr K. J. Wilson 《Experiments in fluids》1989,7(4):248-258
Combustion dynamics of burners with corners were studied using Planar Laser Induced Fluorescence (PLIF) imaging. The effect of sharp corners on the air flow dynamics, shown earlier in cold flow tests, was also found in the reacting flow of a flame. The sharp corners interrupted the coherent structures generated in an axisymmetric shear flow. The combustion at the flat sections of the flame occurred in periodic, coherent large scale structures but was continuous and homogeneous in the vertices sections. The azimuthal structure of the noncircular flame changed in a pattern similar to that found in nonreacting flows. Combined regions of small- and large-scale mixing in the same flow, a unique feature of burners having sharp corners, is beneficial for combustion applications. 相似文献
89.
A. T. J. Parr S. J. Vinton A. Krier R. A. Collins 《Czechoslovak Journal of Physics》1993,43(9-10):969-976
Studies have been made of the application of certain phthalocyanine films in the detection of toxic gases such as chlorine. Consideration has been given to preparation parameters such as deposition conditions (evaporation rate, ambient pressure, post deposition annealing) together with varying central metal atoms within the phthalocyanine molecule. Particular studies have been made concerning the relationship between elevated substrate temperature deposition, the molecular structure and the corresponding sensitivity of the films to gases. The present results are considered within the context of the development of an economically viable selective thin film gas sensor. 相似文献
90.