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41.
Hans-Jörg Reiffen 《Mathematische Annalen》1965,161(5):315-324
Ohne Zusammenfassung 相似文献
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Matrix isolation of Ni atoms in an N2 matrix leads to the formation of Ni(N2)4. This compound, being isoelectronic with the well known Ni(CO)4, represents an important bench-mark system. It has been characterised experimentally by UV/Vis, IR and Raman spectra. The vibrational spectra give evidence for both a1 modes, three of the four t2 modes, and one of the two e modes of the Td symmetric molecule. The experimental data obtained for Ni(14N2)4 and Ni(15N2)4 were used to determine the valence force constants f(Ni-N) and f(N-N), which are compared with those derived for Ni(N2) and for the corresponding carbonyl complexes Ni(CO) and Ni(CO)4. In addition, several overtones and combination modes of Ni(N2)4 were observed for the first time, providing further valuable information about the bond properties. The data allow for the first time a direct estimate of the Ni-N2 bond energy in Ni(N2)4 (120 kJ mol(-1)), that compares with a value of 148 kJ mol(-1) determined by the same method for Ni(CO)4. 相似文献
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8-alpha-Acetoxyverrol (4), the first open chain example of the trichothecenes with oxygenation at C-8, was isolated from cultures of Aphanocladium spectabile. The compound doses the biosynthetic gap to the macrocyclic verrucarins. 相似文献
48.
Peter Schiller Hans-Jörg Mögel Erich Miersemann 《Journal of Mathematical Fluid Mechanics》2010,12(2):293-305
For a class of disjoining pressure potentials the existence of stable liquid layers on solid surfaces is studied. In some
cases of solid configurations with simple geometries explicit results are obtained, in particular for a single cylindrical
or spherical cavity. No smallness for the thickness of the layer is assumed. 相似文献
49.
Konstantin Runovski Hans-Jürgen Schmeisser 《Journal of Fourier Analysis and Applications》2008,14(1):16-38
Means and families of operators generated by Bochner-Riesz kernels are studied. Some sharp results on their convergence are
achieved. The equivalence of the approximation errors of these methods to smoothness quantities related to the Laplacian is
proved.
相似文献
50.
Zhang L D'Acunzi M Kappl M Imhof A van Blaaderen A Butt HJ Graf R Vollmer D 《Physical chemistry chemical physics : PCCP》2010,12(47):15392-15398
Heat treatment is a standard method to increase the hardness of silica in various applications. Here, we tested the effect of high temperature annealing on the mechanical properties of silica microcapsules by force spectroscopy under point loads applied to the particle shell. The Young's modulus of the shells moderately increases after annealing at temperatures above 500 °C. Temperatures over 850 °C result in a much stronger increase and the Young's modulus is close to that of fused silica after annealing at 1100 °C. NMR analysis revealed that in untreated microcapsules synthesized by seeded growth using the St?ber method only 55% of the silicon atoms form siloxane bonds with four neighbors, whereas the remaining ones only form three or less siloxane bonds each and, thus, a large number of ethoxy and silanol groups still exist. During annealing at 500 °C, these are successively transformed into siloxane bonds through condensation reactions. This process correlates with only a moderate increase in Young's modulus. The strong increase at temperatures above 850 °C was associated with a densification which was associated by a decrease in capsule size and shell thickness while the shells remained homogenous and of spherical shape. The main strengthening of the shells is thus mainly due to compaction by sintering at length scales significantly larger than that of local siloxane bonds. 相似文献