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71.
Alexander P. Haehnel Benjamin Wenn Katrin Kockler Tobias Bantle Andrea M. Misske Friederike Fleischhaker Thomas Junkers Christopher Barner‐Kowollik 《Macromolecular rapid communications》2014,35(23):2029-2037
The Arrhenius parameters of the propagation rate coefficient, kp, are determined employing high‐frequency pulsed laser polymerization–size exclusion chromatography (PLP–SEC) for the homologous series of five linear alkyl acrylates (i.e., methyl acrylate (MA), butyl acrylate (BA), dodecyl acrylate (DA), stearyl acrylate (SA), and behenyl acrylate (BeA)) in 1 m solution in butyl acetate (BuAc) as well as in toluene. The comparison of the obtained kp values with the literature known values for bulk demonstrates that no significant solvent influence neither in BuAc nor in toluene on the propagation reaction compared to bulk is detectable. Concomitantly, the kp values in toluene and in BuAc solution display a similar increase with increasing number of C‐atoms in the ester side chain as was previously reported for the bulk systems. These findings are in clear contrast to earlier studies, which report a decrease of kp with increasing ester side chain length in toluene. The additional investigation of the longest and shortest ester side chain acrylate (i.e., BeA and MA) over the entire experimentally available concentration range at one temperature (i.e., 50 °C) does not reveal any general concentration dependence and all observed differences in the kp are within the experimental error.
72.
S. Bernstein K.T. Fehr 《Progress in Crystal Growth and Characterization of Materials》2012,58(2-3):84-91
The influence of grain size of quartz on the formation of 1.13 nm tobermorite in aerated autoclaved concrete was investigated by applying in-situ neutron diffraction. Experiments were performed at 210 °C/Psat employing quartz of 8 μm and 16 μm, respectively. The results reveal changes in the reaction mechanism from solution control to diffusion control. The grain size of the quartz fraction clearly influences the occurrence of those changes. Based on those results an interpretation of former not clearly interpretable quenching experiments was performed. An interpretation using different reaction mechanisms for those experiments leads to a coherent picture of the reaction. 相似文献
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Dirk Müller Rupert Hochleitner Karl Thomas Fehr 《Journal of Raman spectroscopy : JRS》2016,47(5):602-606
A full‐range pattern (100–3700 cm−1) analysis of natural jennite was performed for the first time by Raman spectroscopy, applying a polarized laser at a wavelength of 532 nm. A prominent structural feature of jennite is the preferred orientation of Si‐tetrahedron and Ca‐octahedron chains parallel [010]. The latter ones are additionally coupled to H2O molecules and OH groups. This arrangement leads to a strong dependence on orientation for the intensity ratios of mainly three different regions in the Raman spectra: 180–210, 950–1050 and 3100–3650 cm−1. These sections can be assigned to Ca–O lattice vibrations, Q2 Si–tetrahedron stretching and O–H vibrations of H2O molecules and Ca–OH structures, respectively. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
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Jrg Doege Max Fehr Juri Hinz Hans-Jakob Lüthi Martina Wilhelm 《European Journal of Operational Research》2009,199(3):936-943
Since the 1990s power markets are being restructured worldwide and nowadays electrical power is traded as a commodity. The liberalization and with it the uncertainty in gas, fuel and electrical power prices requires an effective management of production facilities and financial contracts. Thereby derivatives build essential instruments to exchange volume as well as price risks. The challenge for participants in the newly competitive market environment is how to design, price and hedge derivative contracts in particular combination with the flexibility embedded in dispatch strategies of production assets. Accordingly, an adequate basis for management and investment decisions is needed which responds to the highly complex market situation. 相似文献
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Jentoft RE Hahn AH Jentoft FC Ressler T 《Physical chemistry chemical physics : PCCP》2005,7(14):2830-2838
Mn-promoted sulfated zirconia catalysts (2 wt% Mn) were investigated in situ, during the catalyst activation, isomerization of n-butane, and subsequent re-activation, using X-ray absorption spectroscopy of the Mn K-edge. The average valence of Mn in the catalysts, as determined from the edge position, was found to change from either 2.65 or 2.77 in the calcined samples to about 2.5 during activation in He (703 K for 30 min). During the isomerization of n-butane (1% in He, 80 ml min-1, 0.5 g catalyst at 333 K), the average Mn valence did not change further. When the catalyst was activated in 50% O2 the average valence only decreased from about 2.78 to 2.72. In this case, the average valence during the isomerization reaction decreased at a nearly constant rate both during the induction of activity and deactivation of the catalyst. The data do not support a stoichiometric redox reaction involving the promoter as initiator of the isomerization. However, a higher Mn valence after activation was indicative of a higher maximum conversion. It is concluded that the promoter cations function through modification of the structure of the zirconia. 相似文献
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