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81.
82.
83.
Summary The effect of silica gel pretreatment and of different bonding techniques, on the chromatographic properties of octadecyl
bonded phases is described. The experiments show that a monomeric octadecyl bonded phase, prepared from silica gel that has
not been treated before bonding, has a poor selectivity towards polycyclic aromatic hydrocarbons (PAHs) and shows high adsorption
of basic components. Silica gel treatment before the bonding of the monofunctional silane does not give a substantial improvement.
Polymeric phases on the other hand show a much better PAH selectivity and a lower adsorptivity towards basic components. Further
improvement can be achieved with the polymeric modification if silica gel treatment is carried out before bonding. 相似文献
84.
H. Abramowicz F. Dydak J. G. H. de Groot J. Knobloch J. May P. Palazzi F. Ranjard W. D. Schlatter J. Steinberger H. Taureg W. von Rüden H. Wahl J. Wotschack P. Buchholz F. Eisele H. P. Klasen K. Kleinknecht B. Pszola B. Renk H. J. Willutzki T. Flottmann C. Geweniger J. Krolikowski K. Tittel C. Guyot J. P. Merlo A. Para B. Peyaud J. Rander J. Rothberg J. P. Schuller R. Turlay J. T. He T. Z. Ruan W. M. Wu 《Zeitschrift fur Physik C Particles and Fields》1982,12(3):225-227
Right handed weak quark currents coupled to the usual left handed weak lepton current would be seen in inclusive antineutrino scattering on nuclei as a contribution at largey with the quark (not antiquark) structure function. We do not see such a term, and can therefore put an upper limit on the relative strengths of such right handed currents: \(\varrho ^2 = \frac{{\sigma _R }}{{\sigma _L }}< 0.009\) , 90% confidence. This measurement puts limits on the mixing angle of left-right symmetric models. In distinction to similar limits derived from muon decay or β decay, our limits are also valid if the right handed neutrino is heavy. 相似文献
85.
van den Brand J Blajiev O Beentjes PC Terryn H de Wit JH 《Langmuir : the ACS journal of surfaces and colloids》2004,20(15):6318-6326
The bonding of two types of ester group-containing molecules with a set of different oxide layers on aluminum has been investigated using infrared reflection absorption spectroscopy. The different oxide layers were made by giving typical surface treatments to the aluminum substrate. The purpose of the investigation was to find out what type of ester-oxide bond is formed and whether this is influenced by changes in the composition and chemistry of the oxide. The extent by which these bonded ester molecules resisted disbondment in water or substitution by molecules capable of chemisorption was also investigated. The ester groups were found to show hydrogen bonding with hydroxyls on the oxide surfaces through their carbonyl oxygens. For all oxides, the ester groups showed the same nu(C = O) carbonyl stretching vibration after adsorption, indicating very similar bonding occurs. However, the oxides showed differences in the amount of molecules bonded to the oxide surface, and a clear relation was observed with the hydroxyl concentration present on the oxide surface, which was determined from XPS measurements. The two compounds showed differences in the free to bonded nu(C = O) infrared peak shift, indicating differences in bonding strength with the oxide surface between the two types of molecules. The bonding of the ester groups with the oxide surfaces was found to be not stable in the presence of water and also not in the presence of a compound capable of chemisorption with the aluminum oxide surface. 相似文献
86.
Pál Tapolcsányi Bert U.W Maes Katrien MonsieursGuy L.F Lemière Zsuzsanna RiedlGyörgy Hajós Bart Van den DriesscheRoger A Dommisse Péter Mátyus 《Tetrahedron》2003,59(31):5919-5926
Palladium-catalyzed intramolecular arylation of 2-benzyl-5-(2-bromophenyl)-4-phenylpyridazin-3(2H)-one yielded hitherto unknown 2-benzyldibenzo[f,h]phthalazin-1(2H)-one. The synthesis of this new tetracyclic pyridazinone from 2-benzyl-5-(2-aminophenyl)-4-phenylpyridazin-3(2H)-one via a Pschorr type reaction was also investigated. Similarly, the construction of 2-methyldibenzo[f,h]cinnolin-3(2H)-one from 2-methyl-5-(2-bromophenyl)-6-phenylpyridazin-3(2H)-one and 2-methyl-5-(2-aminophenyl)-6-phenylpyridazin-3(2H)-one is also reported. Removal of the N-benzyl protective group of 2-benzyl-dibenzo[f,h]phthalazin-1(2H)-one with AlCl3 yielded unsubstituted dibenzo[f,h]phthalazin-1(2H)-one. 相似文献
87.
D. Mondelaers G. Vanhoyland H. van den Rul J. D'Haen M.K. van Bael J. Mullens L.C. van Poucke 《Journal of Sol-Gel Science and Technology》2003,26(1-3):523-526
An aqueous chemical solution deposition method was used to prepare thin films of ZnO on SiO2/Si (1 1 1) substrates. Starting from an aqueous solution of Zn acetate, citric acid and ammonia, very thin films could be deposited by spin coating. Heating parameters, necessary for thin film annealing, were determined using FTIR experiments on dried gel precursors, heated up to different temperatures. The morphology and the thickness of the films were investigated by SEM. It is found that homogeneous thin films with grain sizes of about 20 nm are formed. XRD experiments show that there is an indication that the films, crystallized at 500°C, exhibit preferential grain growth along the c-axis. 相似文献
88.
Jan Bouwe van den Berg Jason D. Mireles James Christian Reinhardt 《Journal of Nonlinear Science》2016,26(4):1055-1095
We develop techniques for computing the (un)stable manifold at a hyperbolic equilibrium of an analytic vector field. Our approach is based on the so-called parametrization method for invariant manifolds. A feature of this approach is that it leads to a posteriori analysis of truncation errors which, when combined with careful management of round off errors, yields a mathematically rigorous enclosure of the manifold. The main novelty of the present work is that, by conjugating the dynamics on the manifold to a polynomial rather than a linear vector field, the computer-assisted analysis is successful even in the case when the eigenvalues fail to satisfy non-resonance conditions. This generically occurs in parametrized families of vector fields. As an example, we use the method as a crucial ingredient in a computational existence proof of a connecting orbit in an amplitude equation related to a pattern formation model that features eigenvalue resonances. 相似文献
89.
J. van Soolingen R. J. De Lang R. den Besten P. A. A. Klusener N. Veldman A. L. Spek 《合成通讯》2013,43(11):1741-1744
1,8-Bis(diphenylphosphino)naphthalene has been obtained in good yields from 1,8-dilithionaphthalene and chlorodiphenylphosphine. 相似文献
90.
Some cases of the LFED Conjecture, proposed by the second author [15], for certain integral domains are proved. In particular, the LFED Conjecture is completely established for the field of fractions of the polynomial algebra , the formal power series algebra and the Laurent formal power series algebra , where denotes n commutative free variables and k a field of characteristic zero. Furthermore, the relation between the LFED Conjecture and the Duistermaat–van der Kallen Theorem [3] is also discussed and emphasized. 相似文献