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91.
Three Co(II) and Cu(II)-pyridine-2,5-dicarboxylate (pydc) proton transfer compounds with 1,4-butanediamine (ben) and 2,2-dimethylpropane-1,3-diamine (dmpen), trans-(H2ben)[Co(pydc)2(H2O)2]·4H2O (1), trans-(H2dmpen)[Co(pydc)2(H2O)2]·2H2O (2) and (H2ben)2[Cu2(μ-pydc)4(H2O)2] (3) have been synthesized and characterized by the methods of elemental, spectroscopic (IR and UV-Vis), thermal (TG/DTG, DTA) analysis, magnetic measurement and single crystal X-ray diffraction. The crystallographic analysis revealed that the complexes consist of [Co(pydc)2(H2O)2]2− anion, bis(protonated) diamine cation (H2ben for 1 and H2dmpen for 2) and four and two crystal water molecules, respectively. The Co(II) ions are coordinated by two pydc and two aqua ligands. The bis(deprotonated) pydc ligands coordinate to the Co(II) ions through the nitrogen atom of pyridine ring and the oxygen atom of carboxylate group, creating a chelate ring. The distorted octahedral geometries are completed by two trans aqua ligands at axial positions. The molecular structure of the complex 3 consists of dinuclear [Cu2(μ-pydc)4(H2O)2]4− units and bis(protonated) 1,4-butanediammonium cation. In the structure, each Cu(II) ion is coordinated by two nitrogen and two oxygen atoms from two pydc ligands and one oxygen atom from aqua ligand, forming a distorted square pyramidal geometry.  相似文献   
92.
Tarnkappen, die Menschen unsichtbar machen, galten jahrtausendelang als unerreichbarer Mythos. Unlängst konnten wir am Karlsruhe Institute of Technology gemeinsam mit Kollegen aus London jedoch erstmals eine dreidimensionale optische Tarnkappe herstellen und deren Funktion mit Hilfe eines optischen Mikroskops direkt experimentell nachweisen.  相似文献   
93.
94.
We show, using a simple example, that the First-In-First-Out (FIFO) policy can be unstable in a system with arbitrarily low load. Our proof is based on the observation that the special structure of the example we use allows us to establish stability using a much simpler queueing system.  相似文献   
95.
Herein we present a whole new approach that leads to the end results of the general theory of relativity via just the law of conservation of energy (broadened to embody the mass and energy equivalence of the special theory of relativity) and quantum mechanics. We start with the following postulate. Postulate: The rest mass of an object bound to a celestial body amounts less than its rest mass measured in empty space, and this, as much as its binding energy vis-á-vis the gravitational field of concern.  相似文献   
96.
A three dimensional analytical model for crawl stroke swimming is developed in which the swimmer is modeled as a body and two arms connected to the body at the shoulder joints. Each arm is assumed to consist of three segments. The numerical results obtained from the model are compared with the results of two sets of experiments performed. In the first series of experiments, the tether forces developed in crawl stroke swimming are measured and a linear correlation between the tether force and the stroke rate is obtained. In the second series of experiments, untethered crawl stroke swimming for different arm position angles is recorded. The results are presented in graphical forms and the effect of stroke rate on swimming velocity is discussed.  相似文献   
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98.
Die Transformationsoptik erlaubt Verformungen des optischen Raums, die denen der Raumzeit in der Allgemeinen Relativitätstheorie bei Anwesenheit von Materie ähneln. Von Fata Morganas ist der Effekt kontinuierlich veränderlicher Brechzahlprofile vertraut. Doch erst die Theorie der Transformationsoptik erlaubt die systematische Entwicklung völlig neuer optischer Funktionen. Computersimulationen des Karlsruhe Institute of Technology zeigen, wie eine Tarnkappe und eine kugelförmige Strahlumlenkung funktionieren könnten – zwei Beispiele für die ungeahnten prinzipiellen Möglichkeiten der Transformationsoptik. Die experimentelle Umsetzung im optischen Spektralbereich stellt allerdings noch eine große Herausforderung dar.  相似文献   
99.
As an application of the construction of open books on plumbed 3-manifolds, we construct elliptic open books on torus bundles over the circle. In certain cases these open books are compatible with Stein fillable contact structures and have minimal genus.   相似文献   
100.
Abstract  X-ray crystallographic analysis of the title organic ion–pair complex, C18H18NO2 + · ClO4 , reveals that 6,7-dimethoxy-2-methyl-4-phenylisoquinolinium cation is co-crystallized with perchlorate counter-anions in 1:1 ratio. The complex crystallizes in space group P 2 1 /n, with a = 8.0226(7) ?, b = 12.2552(7) ?, c = 17.9734(16) ?, β = 93.908(7) °, Z = 4, D x  = 1.431 g/cm3. Aromaticity of isoquinolinium fragment is considerably deformed by the existence of C–H···O type weak H-bonds, leading to chains of topology C 3 3(12)[R 12(4)] running along b-axis of the unit cell and pseudo-cyclic centrosymmetric R 44(24)[2R 12(4)] synthons. The weak H-bonds serve to stabilize both the extended structure and molecular geometry of the title complex, in particular the disordered perchlorate anion whose components adopt a distorted tetrahedron. Index Abstract  Molecular and the extended structure of 6,7-dimethoxy-2-methyl-4-phenylisoquinolinium perchlorate, C18H18NO2 + · ClO4 , were determined by single crystal X-ray diffraction study.  相似文献   
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