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71.
72.
Xuefeng Li Nicholas Tan Mike Pivnenko Juraj Sibik J. Axel Zeitler 《Liquid crystals》2016,43(7):955-962
Liquid crystals (LCs) have been studied extensively in the visible range for their dielectric tunability, and the characterisation in the terahertz (THz) range has gained increasing interest due to the need for active THz modulation and switching devices. In this paper, we use THz time-domain spectroscopy to measure the frequency-dependent birefringence and the absorption coefficient of a number of commercial and non-commercial nematic LCs, including E7, BL037, MDA-98-1602, LCMS-107, GT3-23001 and 1825, over a range of bias voltages at room temperature. Furthermore, several basic components of LC mixture are analysed to establish their contributions to birefringence and theoretical model is used to fit the absorption spectra. The large tunability and low loss measured for a range of samples show that the LCs are useful tunable dielectrics for compact, efficient and broadband THz devices. 相似文献
73.
Sebastian Aland Stephan Schwarz Jochen Fröhlich Axel Voigt 《The European physical journal. Special topics》2013,220(1):185-194
In simulations of liquid metals, various model approximations, each of which justified by experimental results lead to a simplified two-phase flow problem. This paper discusses numerical justifications for these approaches and provides quantitative results for a single rising bubble as a benchmark. Representing a bubble as a rigid object is shown to be valid for low Eötvös numbers in contaminated systems. Qualitative differences can be observed for larger Eötvös numbers. Further simulations are undertaken with different ratios of inner and outer viscosity. The benchmark problem considered may also be interesting for more general applications. 相似文献
74.
A series of new coordination polymers bearing the [B(O–C6H4–CN)4]– anion was synthesized. Two new, one dimensional coordination frameworks of the type M[B(O–C6H4–CN)4] (M = Ag, Cu) were obtained by salt metathesis. The reactivity towards organic Lewis‐bases was studied. The reaction with bidentate ligands yielded two dimensional networks with the general formula [M(L)][B(O–C6H4–CN)4] {L = 2,2′‐bipyridine, 4,4′‐bipyridine, 1,2‐bis(pyridyl)ethane, 1,4‐diazabicyclo[2.2.2]octane}. The synthesis, properties and single crystal structure are reported. 相似文献
75.
Pradip Ghosh Roland Schoch Matthias Bauer Axel Jacobi von Wangelin 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2022,134(1):e202110821
Metal-catalyzed C?H activations are environmentally and economically attractive synthetic strategies for the construction of functional molecules as they obviate the need for pre-functionalized substrates and minimize waste generation. Great challenges reside in the control of selectivities, the utilization of unbiased hydrocarbons, and the operation of atom-economical dehydrocoupling mechanisms. An especially mild borylation of benzylic CH bonds was developed with the ligand-free pre-catalyst Co[N(SiMe3)2]2 and the bench-stable and inexpensive borylation reagent B2pin2 that produces H2 as the only by-product. A full set of kinetic, spectroscopic, and preparative mechanistic studies are indicative of a tandem catalysis mechanism of CH-borylation and dehydrocoupling via molecular CoI catalysts. 相似文献
76.
77.
78.
Axel Ruhe 《BIT Numerical Mathematics》2012,52(2):271-272
79.
Axel D. Becke 《Molecular physics》2015,113(13-14):1884-1889
The energy surfaces of the ground and low-lying excited states of ethylene are challenging tests of multi-reference electronic structure methods. A variety of multi-reference wavefunction theories have been applied to this problem and the ensuing photochemistry has been well studied. Density-functional methods, however, have been less successful. In this work, the ‘B13’ strong-correlation density functional is used to generate multi-reference orbitals for the computation of the three lowest-lying singlet states. We explore the states and energies as a function of torsion angle, and as a function of the pyramidalisation angle with respect to the twisted orthogonal structure. The former features an avoided crossing at the orthogonal structure; the latter a Cs slice through a conical intersection. Both features are well reproduced by our B13 method. 相似文献
80.
Christopher Hubrich Axel Schulz Harald Brand Alexander Villinger 《Phosphorus, sulfur, and silicon and the related elements》2013,188(9):2179-2196
The silyl ethers (siloxanes) Me4? xSi(OC6H5CN)x (x = 1–4) (1–4), O(Si(OC6H4CN) (Me)2)2 (5), and Me3Si–O–C6F4CN (6) have been synthesized by the reaction of the respective p-hydroxybenzonitriles and chlorosilanes in the presence of N,N,N′,N′-tetramethylethylenediamine (TMEDA) as hydrogen chloride acceptor. All compounds have been fully characterized by CHN-analysis, melting point, IR, Raman, mass spectroscopy, and 1H, 13C, 29Si NMR spectroscopy. Furthermore, the crystal structures of these compounds—with the exception of Me2Si(OC6H5CN)2, which is a liquid—were determined by X-ray diffractometry. 相似文献