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91.
The angular overlap model has been applied for the first time in a conformational study of ground state properties of coordination compounds. The existence of several triplet ground states resulting from continuous rotations about the MoOMo axis has been demonstrated for oxygen-bridged oxomolybdenum(V) dimers. 相似文献
92.
Sylwia Studzińska Rafał Rola Bogusław Buszewski 《Analytical and bioanalytical chemistry》2016,408(6):1585-1595
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Bogusława łęska Błażej Gierczyk Krystian Eitner Volodimir I. Rybachenko Grzegorz Schroeder 《Supramolecular chemistry》2013,25(5):303-310
Three types of silicon podands, Me2Si(OR)2, EtSi(OR)3 and PhSi(OR)3, where R is a polyoxaethylene chain with different numbers of oxygen atoms (two, three or four), were obtained and studied by 1H, 13C and 29Si NMR methods. NMR spectra of 1H, 7Li, 13C, 23Na and 29Si nuclei were also used for the study of lithium, sodium and rubidium complexes with the silicon podands. Theoretical calculations were performed using the PM3 hamiltonian. The heats of reactions between the compounds obtained and SbCl5 were determined. 相似文献
97.
A needle‐trap device, with immobilized sorbent inside the syringe, coupled with GC–MS was applied for air sampling and determination of chlorinated volatile organic compounds such as dichloromethane, trichloromethane, and tetrachloromethane. The application of a needle trap packed with combination of three sorbents including Tenax TA, Carbopack X, and Carboxen 1000 resulted in detection limits of few pg for chlorinated volatile compounds and recoveries of 99.2–102.8%. The extraction and desorption parameters were optimized within the study. As a result, the precision determined as RSD was equal to 5.05 and 3.03 and 6.52% for dichloromethane, trichloromethane, and tetrachloromethane, respectively. The storage time for chlorinated compounds up to 48 h and reusability of the needle‐trap device were verified. The obtained results have proved the ability of needle traps to compete with other solventless sampling and sample preparation extraction techniques. 相似文献
98.
Šime Ukić Mirjana Novak Petar Žuvela Nebojša Avdalović Yan Liu Bogusław Buszewski Tomislav Bolanča 《Chromatographia》2014,77(15-16):985-996
New retention methodology that integrates the conventional quantitative structure-retention relationship (QSRR) approach and gradient retention modeling based on isocratic retention data is developed and presented in this paper. Such an integrated approach removes the general QSRR limitation of highly predefined application conditions (i.e., QSRR are generally applicable only under the conditions used during model development) and allows the prediction of retentions over a wide range of different elution conditions (practically for any isocratic or gradient elution profile). At the same time, it retains the ability to predict retention of components unknown to the model, i.e., the components that have not been used in modeling. Ion-exchange chromatography (IC) analysis of carbohydrates was selected as modeling environment. Three regression techniques were applied and compared during QSRR modeling, namely: stepwise multiple linear regression, partial least squares (PLS), and uninformative variable elimination–PLS regression. The obtained prediction results of the best QSRR model (root-mean-square error of prediction = 22.69 %) were similar to those found in the literature. The upgrade from QSRR to the integrated model did not diminish the predictive ability of the model, indicating an excellent potential of the developed methodology not only in IC but also in chromatography in general. 相似文献
99.
Comparison of four cholesterol‐based stationary phases for the separation of steroid hormones
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Jan Soukup Szymon Bocian Pavel Jandera Bogusław Buszewski 《Journal of separation science》2014,37(4):345-351
The chromatographic behavior of steroid hormones on four cholesterol‐bonded stationary phases with different structures in binary methanol/water mobile phases was studied. Of the stationary phases tested, the commercially available stationary phases Cogent UDC cholesterol? and COSMOSIL cholester? provided better separations of steroid hormones in comparison to homemade aminocholesterol and diaminocholesterol stationary phases. The results show that the temperature has a significant influence on the retention and selectivity for steroid hormones separation. The temperature increase may cause changes in the elution order. From the dependences of the retention (ln k) on temperature (1/T), the standard partial molar enthalpy and standard partial molar entropy were calculated and their enthalpic and entropic contributions to the retention were compared. The enthalpic effects principally control the retention mechanism. 相似文献
100.
Margherita Barile Fiorella Barone Wlodzimierz M. Tulczyjew 《Linear and Multilinear Algebra》2007,55(2):121-146
Within the framework of mappings between affine spaces, the notion of nth polarization of a function will lead to an intrinsic characterization of polynomial functions. We prove that the characteristic features of derivations, such as linearity, iterability, Leibniz and chain rules are shared - at the finite level - by the polarization operators. We give these results by means of explicit general formulae, which are valid at any order n, and are based on combinatorial identities. The infinitesimal limits of the nth polarizations of a function will yield its nth derivatives (without resorting to the usual recursive definition), and the afore-mentioned properties will be recovered directly in the limit. Polynomial functions will allow us to produce a coordinate free version of Taylor's formula. 相似文献