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71.
Journal of the Operational Research Society - 相似文献
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The reduction of ReCl4(THF)2 in the presence of excess t-butylisocyanide by sodium amalgam produces pentakis(t-butylisocyanide)chlororhenium(I), which has been converted to the corresponding methyl and ethyl derivatives. The reaction of pentakis(trimethylphosphine)chlororhenium(I) with ButNC gives partially substituted complexes, ReCl(CNBut)2(PMe3)3 and ReCl(CNBut)3(PMe3)2. The structures of both compounds have been determined by X-ray methods. Octahedral ReCl(CNBut)2(PMe3)3 has trans isocyanide groups with one linear [C---N---C = 175(1)°] and one slightly bent [C---N---C = 159(1)°]. The Re---C bond lengths are equal within experimental error [2.004(7), 2.003(7)Å]. In the octahedral ReCl(CNBut)3(PMe3)2, for which the structure is not well defined, due to disorder, the unique isocyanide trans to chlorine is considerably bent at the nitrogen atom [C---
---C = 141(6)°] and appears to show the shortest Re---C bond length, 1.94(5) vs 2.02(5)Å for the other two isocyanides which are mutually trans. Protonation of these two isocyanide complexes with fluoroboric acid gives, respectively, the salts [ReCl(CNBut)CNHBut(PMe3)3]BF4 and [ReCl(CNBut)2CNHBut(PMe3)2]BF4, whose configurations have been determined by NMR spectroscopy. The reduction by sodium amalgam of Cr2(CO2Me)4 in tetrahydrofuran in presence of ButNC gives a high yield of Cr(CNBut)6 while similar reduction of the dimeric tungsten(II) complex of the anion (mhp) of 2-methyl-6- hydroxypyridine gives W(CNBut)6. Interaction of W2(mhp)4 in methanol-ether with ButNC gives a tungsten(I) complex W2(η-mhp)2(ButNC)4, which may be an intermediate in the reductive cleavage reaction. Interaction of cis-PtMe2(PMe3)2 with ButNC leads only to replacement of one PMe3 group to give the complex cis-PtMe2(PMe3)(CNBut). 相似文献
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Arkady I. Gusev William R. Wilkinson Andrew Proctor D. M. Hercules 《Fresenius' Journal of Analytical Chemistry》1996,354(4):455-463
The protocol and various matrices were examined for quantification of biomolecules in both the low ca. 1200 amu and mid mass 6000–12000 amu ranges using an internal standard. Comparative studies of different matrices of MALDI quantitative analysis showed that the best accuracy and standard curve linearity were obtained for two matrices: (a) 2,5-dihydroxybenzoic acid (DHB) combined with a comatrix of fucose and 5-methoxysalicylic acid (MSA) and (b) ferulic acid/fucose. In the low mass range, the quantitative limit was in the 30 fmol range and in the mid mass range the quantitative limit was in the 250 fmol range. Linear response was observed over 2–3 decades of analyte concentration. The relative error of the standard curve slope was 1.3–1.8% with correlation coefficients of 0.996–0.998.The main problem for quantitative measurement was suppression of the signal of the less concentrated component (analyte or internal standard) by the more concentrated component. The effect was identified with saturation of the matrix by the analyte. The threshold of matrix saturation was found to be in the range of 1/(3000–5000) analyte/matrix molar ratio. To avoid matrix saturation the (analyte+internal standard) to matrix molar ratio should be below this threshold. Thus the internal standard concentration should be as low as possible.DHB/MSA/fucose and ferulic acid/fucose matrices demonstrated good accuracy and linearity for standard curves even when the internal standard had chemical properties different from the analyte. However, use of an internal standard with different chemical properties requires highly stable instrumental parameters as well as constant (analyte+internal standard)/matrix molar ratio for all samples. 相似文献
76.
R.J. Grant C.G. Johnson D.H. Wilkinson 《International Journal of Heat and Fluid Flow》1983,4(4):239-245
A single stage model turbine has been provided with a set of three special inlet sections which include backward facing steps to produce casing separations of varying size upstream of the stator blades. In addition each inlet section is equipped so as tc be able to emit a swirling jet which simulates the tip leakage jet from a preceeding stage. It is demonstrated that there is a substantial efficiency penalty associated with the stepped casing and its attendant separation and that a small mitigation is brought about by the tip leakage jet, by re-energising the fluid in the separation zone 相似文献
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R.T. Wilkinson 《Journal of sound and vibration》1984,95(1):55-63
The literature on the effects of noise on sleep is searched for evidence on individual differences along the dimensions of age, sex, occupation, personality, neuroticism, and mental health. With the exception of age, little firm evidence is found. Thus there remains a need to establish at better than the anecdotal level whether or not real individual differences exist. 相似文献