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François P. Rotzinger PD Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2007,13(36):10298-10302
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Guiding of multiple signal beams in an induced all-optical cable is studied theoretically. A balance relation is derived for the interaction geometry and undistorted propagation of bright elliptical signal beams nested in a single ring dark soliton. The numerical analyses show a remarkable misalignment stability of the parallel guiding scheme. 相似文献
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A polarization method has been used to study stimulated processes in potassium with a common emission channel. The contribution of different emission mechanisms has been evaluated and the nature of the interference effects clarified. 相似文献
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Daunne Christa PD Dr. 《ZDM》2003,35(3):102-109
It is reported about a longitudinal study run at the Institute of Cognitive Mathematics of the University of Osnabrueck, in which pupils’ verbal and text productions from mathematics lessons at a grammar school are analysed by means of cognitive theoretical methods. First of all, a teaching scene from an instruction to probability calculus and further text productions from an introductory lesson about exponential functions are analysed, in which five pupils take part whose cognitive structures have been assessed and classified in individual examinations. The characteristics brought out according to these teaching scenes indicate different ideas and thinking processes of the pupils. The second part shows that the pupils’ behaviour described is not only to be regarded in isolation but it can also be found in longitudinal examinations and can therefore be considered as a stable, typical characteristic. These results lead to consequences for the planning and design of mathematics lessons based on a well-founded theory of cognition. 相似文献
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Reaction of nickel(II) thiocyanate and pyridazine (pdz) as organic spacer ligand leads to the formation of the ligand‐rich 1:2 (1:2 = metal to ligand ratio) trinuclear nickel(II) complex of composition [Ni3(NCS)6(pdz)6]. Depending on the reaction solvent, different polymorphic modifications are obtained: Reaction in acetonitrile leads to the formation of the new modification 1I and reaction in ethanol leads to the formation of modification 1II reported recently. In their crystal structures discrete [Ni3(NCS)6(pdz)6] units are found, in which each of the Ni2+ cations exhibits a NiN6 distorted octahedral arrangement. The central Ni2+ cation is coordinated by four bridging pdz ligands and two thiocyanato anions in trans positions. Both thiocyanato anions exhibit the end‐on bridging mode. The peripheral Ni2+ cations are bridged by one thiocyanato anion and by two pdz ligands with the central Ni2+ cation. Further they are coordinated by two terminal N‐bonded thiocyanato anions and one terminal N‐bonded pdz ligand. The structure of 1I was determined by X‐ray single crystal structure investigation and emphasized by infrared spectroscopy. Magnetic measurements revealed a quasi Curie behavior with net ferromagnetic interactions for 1I and net antiferromagnetic interactions for 1II . Solvent‐mediated conversion experiments clearly show that modification 1I represents the thermodynamic most stable form at room temperature and that modification 1II is metastable. On thermal decomposition, both modification transform quantitatively in a new ligand‐deficient intermediate. Elemental analysis revealed a 3:4 compound of composition [Ni3(NCS)6(pdz)4]. A structure model supported by IR spectroscopic investigations was assumed, in which three coordination modes of the thiocyanato anion exist, resulting in a 2D polymeric network. 相似文献
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The crystal structure of K[BF3(CN)] (Pbcn (Nr. 60) with a = 13.3486(15) b = 6.5239(7) c = 10.0085(11) Å, and eight formula units per unit cell) has been determined and the one of K[BF2(CN)2] was confirmed and improved. The different networks in the complete series of borates K[BFx(CN)4–x], x = 0–4 are compared and discussed. 相似文献