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991.
Analytical methods have been developed for the quantitative determination of Bu4Sn, Bu3Sn+, Bu2Sn2+, BuSn3+, Me3BuSn, Me2Bu2Sn, MeBu3Sn, MeBuSn2+, Me2BuSn+ and MeBu2Sn+ in water. Organotin compounds are extracted from water with tropolone at 0.1 % in n-pentane, derivatized with n-pentylmagnesium bromide and determined by gas chromatography with flame photometric detection or flame ionization detection. Absolute detection limits are 0.05-0.12 ng and 1.2-13 ng as tin, respectively. The method was applied to the analysis of spiked tap-water containing 0.3-1000 ng cm?3 of each of the organotin compounds. 相似文献
992.
Emilio Gagliardo 《Milan Journal of Mathematics》1986,56(1):39-49
This article is a study of the problem posed by the use of a theory of harmony by Composers. Such a doctrine has the chance to become a mathematical theory in most temperaments discovered in the history of music, except the traditional. Basic non ambiguous concepts give rise to an algorithmic language which contains classic notions of harmony as well as rules for a new kind of «atonal intervals». Resulting new styles of music can be performed with standard instruments not because of the traditional dodecaphonic temperament but in spite of it. 相似文献
993.
994.
Luis Moreno Manuel Blázquez Manuel Dominguez Emilio Roldán 《Journal of Electroanalytical Chemistry》1985,185(1):119-130
A study has been carried out on the reduction mechanism of alloxan over a DME corresponding to the first two-electron transfer over the pH range 0–12.Polarographic and voltammetric results show the reduction process to be kinetically controlled. Rate and equilibrium constant data for the prior chemical reaction have been evaluated and several reaction mechanisms for different pH zones have been proposed. 相似文献
995.
Let At(i, j) be the transition matrix at time t of a process with n states. Such a process may be called self-adjusting if the occurrence of the transition from state h to state k at time t results in a change in the hth row such that At+1(h, k) ? At(h, k). If the self-adjustment (due to transition h → kx) is At + 1(h, j) = λAt(h, j) + (1 ? λ)δjk (0 < λ < 1), then with probability 1 the process is eventually periodic. If A0(i, j) < 1 for all i, j and if the self-adjustment satisfies At + 1(h, k) = ?(At(h, k)) with ?(x) twice differentiable and increasing, x < ?(x) < 1 for 0 ? x < 1,?(1) = ?′(1) = 1, then, with probability 1, lim At does not exist. 相似文献
996.
Dario Braga Fabrizia Grepioni Emilio Tedesco Paul J. Dyson Caroline M. Martin Brian F. G. Johnson 《Transition Metal Chemistry》1995,20(6):615-624
Summary The molecular and crystal structure of Ru3(CO)12 has been reinvestigated on single-crystal X-ray diffraction data collected at 100 and 150 K. Thermal motion analysis on high-order diffraction data have been used to characterize the motion about equilibrium positions of the molecule as a whole and of groups of atoms. It has been shown that, while the molecule undergoes an almost isotropic rigid-body librational and translational motion, the three Ru(CO)4 units undergo different librational motions about the axes passing between each Ru atom and bisecting the opposite 615-01 bond. Packing potential energy calculations and computer graphics have been used to show that the most favoured packing motif in the experimental crystal is based on interlocking between tetracarbonyl units formed by two pairs of CO ligands at right angles along a 615-02 edge. Starting from the structure of Ru3(CO)12, alternative crystal arrangements have been generated and compared with the experimental crystal structure in terms of packing efficiency and cohesive energy. 相似文献
997.
J. J. LaBrecque P. A. Rosales A. Quiero 《Journal of Radioanalytical and Nuclear Chemistry》1982,75(1-2):205-211
A new technique was applied for exciting X-rays for X-ray fluorescence analysis by “direct” beta excitation for the determination of noble metals in catalytic materials. 相似文献
998.
999.
Emilio Baiada 《Annali di Matematica Pura ed Applicata》1962,60(1):235-247
a Enrico Bompiani in occasione del suo Giubileo scientifico.
Lavoro eseguito nell' ambito del gruppo di rieerea N. 18 del C.N.R. 相似文献
1000.
Carrascal M Schneider K Peralta C Escolar G Gelpi E Abian J 《Biomedical chromatography : BMC》2004,18(6):388-395
A method for the quantitative analysis of endothelin peptides in human umbilical vein endothelial cell (HUVEC) culture supernatants is reported. The analysis is isoform-specific and employs solid-phase extraction and subsequent HPLC fractionation followed by HPLC-ESIMS analysis. The peptide vasoactive-intestinal-contractor (VIC) was used as internal standard for the HPLC-ESIMS analysis. Linearity of calibration curves was from 50 fmol to 25 pmol. The limit of detection of the HPLC-ESIMS step using a buffer matrix was estimated at 50 fmol (S/N > 3). The overall limit of detection for supernatants of HUVEC was 500 fmol/mL. In HUVEC culture supernatants only ions of endothelin-1 (ET1) were observed. Basal levels were determined to be 1.8 +/- 0.3 pmol/mL. Quantitative results obtained for ET1 were in agreement with those obtained by using a standard addition method and by an ELISA method. 相似文献