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641.
Viktor Kettmann Jan Lokaj Jozef Koíek Josef Pikryl Vladimír Mach
ek 《Acta Crystallographica. Section C, Structural Chemistry》2004,60(2):o143-o145
The molecule of the title compound, C17H17N5O2S, consists of three π systems, viz. two aromatic rings and the triazene moiety, which are mutually deconjugated although coplanar. The n‐butyl chain is roughly perpendicular to the molecular plane, with the terminal methylene and methyl groups disordered between two equally populated positions. The molecules in the crystal associate in an antiparallel fashion, forming dimers across the centre of symmetry, the principal intradimer interaction being stacking of the π‐electron portions of the molecules. 相似文献
642.
643.
Vratislav Langer Miroslav Ko Dalma Gyepesov Juraj Kronek Jozef Lusto Mariana Sldkovi
ov 《Acta Crystallographica. Section C, Structural Chemistry》2005,61(10):o602-o606
Crystal structures are reported for three isomeric compounds, namely 2‐(2‐hydroxyphenyl)‐2‐oxazoline, (I), 2‐(3‐hydroxyphenyl)‐2‐oxazoline, (II), and 2‐(4‐hydroxyphenyl)‐2‐oxazoline, (III), all C9H9NO2 [systematic names: 2‐(4,5‐dihydro‐1,3‐oxazol‐2‐yl)phenol, (I), 3‐(4,5‐dihydro‐1,3‐oxazol‐2‐yl)phenol, (II), and 4‐(4,5‐dihydro‐1,3‐oxazol‐2‐yl)phenol, (III)]. In these compounds, the deviation from coplanarity of the oxazoline and benzene rings is dependent on the position of the hydroxy group on the benzene ring. The coplanar arrangement in (I) is stabilized by a strong intramolecular O—H⋯N hydrogen bond. Surprisingly, the 2‐oxazoline ring in molecule B of (II) adopts a 3T4 (C2TC3) conformation, while the 2‐oxazoline ring in molecule A, as well as that in (I) and (III), is nearly planar, as expected. Tetramers of molecules of (II) are formed and they are bound together via weak C—H⋯N hydrogen bonds. In (III), strong intermolecular O—H⋯N hydrogen bonds and weak intramolecular C—H⋯O hydrogen bonds lead to the formation of an infinite chain of molecules perpendicular to the b direction. This paper also reports a theoretical investigation of hydrogen bonds, based on density functional theory (DFT) employing periodic boundary conditions. 相似文献
644.
Nonlinear Dynamics - A recursive identification method for discrete-time nonlinear cascade systems with a linear dynamic system followed by a time-varying output hysteresis is presented. The... 相似文献
645.
Štefan Chromik Marianna Španková Jozef Liday Peter Lobotka 《Applied Surface Science》2008,254(12):3635-3637
Epitaxial MgO thin films have been grown on semiinsulating GaAs (0 0 1) substrates using electron beam (e-beam) evaporation. X-ray diffraction indicates c-axis oriented MgO with (0 0 2) reflection only and rocking curve widths ∼2.2-3°. Transmission electron microscopy (TEM) analyses confirm an epitaxial growth of the MgO films. We study the microstructure and the defects at the interface between the MgO film and the GaAs substrate. Auger electron Spectroscopy (AES) concentration depth profiles reveal no contamination of the MgO films by As and Ga at different temperatures of the deposition process. 相似文献
646.
B.Golob for the Belle Collaboration Jozef Stefan Institute Faculty of Mathematics Physics Univ.of Ljubljana Ljubljana Slovenia 《中国物理 C》2008,(6)
We present a preliminary measurement of the B(D_s→μν_μ)with the Belle experiment at the KEKB collider.We select D~s→μV_μdecays with a method that provides a high-purity of the selected sample and an absolute measurement of the branching fraction.The results are based on a data sample of 550 fb~(-1)and are compared to similar measurements by other experiments as well as to the predictions of LQCD.We conclude with short prospects for improvements in the accuracy of the measurement. 相似文献
647.
Qingrui Zhang Sreenath Bolisetty Yiping Cao Stephan Handschin Jozef Adamcik Qiuming Peng Raffaele Mezzenga 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(18):6073-6077
We report a new strategy for efficient removal of F? from contaminated water streams, and it relies on carbon hybrid membranes made of amyloid fibril/ZrO2 nanoparticles (<10 nm). These membranes exhibit superior selectivity for F? against various competitive ions, with a distribution coefficient (Kd) as high as 6820 mL g?1, exceeding commercial ion‐exchange resins (IRA‐900) by 180 times and outdoing the performance of most commercial carbon‐activated aluminum membranes. At both low and high (ca. 200 mg L?1) F? concentrations, the membrane efficiency exceeds 99.5 % removal. For real untreated municipal tap water (ca. 2.8 mg L?1) under continuous operating mode, data indicates that about 1750 kg water m?2 membrane can be treated while maintaining drinking water quality, and the saturated membranes can be regenerated and reused several times without decrease in performance. This technology is promising for mitigating the problem of fluoride water contamination worldwide. 相似文献
648.
Jozef Gonda Michael Široký Miroslava Martinková Samuel Homolya Mária Vilková Martina Bago Pilátová Sergej Šesták 《Tetrahedron》2019,75(3):398-408
A straightforward stereoselective route towards (3aR,5R,6S,7R,7aR)- and (3aR,5R,6S,7R,7aR)-octahydro-1H-indole-5,6,7-triol, analogues of castanospermine, starting from the corresponding shikimic acid derivatives is described. The key transformations of this approach are the Overman rearrangement and ring-closing metathesis to form the diastereoisomeric cis-fused (5R,6S,7R)-octahydro-1H-indole-5,6,7-triols in good overall yields. Evaluation for in vitro cytotoxicity revealed for some prepared compounds significant antiproliferative activity and weak glycosidase inhibition. 相似文献
649.
Nguyen TL Dils B Carl SA Vereecken L Peeters J 《The journal of physical chemistry. A》2005,109(43):9786-9794
In this work, the C(2)F(4)(X(1)A(g)) + O((3)P) reaction was investigated experimentally using molecular beam-threshold ionization mass spectrometry (MB-TIMS). The major primary products were observed to be CF(2)O (+ CF(2)) and CF(3) (+ CFO), with measured approximate yields of % versus %, respectively, neglecting minor products. Furthermore, the lowest-lying triplet and singlet potential energy surfaces for this reaction were constructed theoretically using B3LYP, G2M(UCC, MP2), CBS-QB3, and G3 methods in combination with various basis sets such as 6-31G(d), 6-311+G(3df), and cc-pVDZ. The primary product distribution for the multiwell multichannel reaction was then determined by RRKM statistical rate theory and weak-collision master equation analysis. It was found that the observed production of CF(3) (+ CFO) can only occur on the singlet surface, in parallel with formation of ca. 5 times more CF(2)O(X) + CF(2)(X(1)A(1)). This requires fast intersystem crossing (ISC) from the triplet to the singlet surface at a rate of ca. 4 x 10(12) s(-1). The theoretical calculations combined with the experimental results thus indicate that the yield of triplet CF(2)(?(3)B(1)) + CF(2)O formed on the triplet surface prior to ISC is < or =35%, whereas singlet CF(2)(X(1)A(1)) + CF(2)O is produced with yield > or =60%, after ISC. In addition, the thermal rate coefficients k(O + C(2)F(4)) in the T = 150-1500 K range were computed using multistate transition state theory and can be expressed as k(T) = 1.67 x 10(-16) x T(1.48) cm(3) molecule(-1) s(-1); they are in agreement with the available experimental results in the T = 298-500 K range. 相似文献
650.
[carbohydrate structure: see text] Hydrogen bond mediated NMR J couplings offer additional structural information. The interpretation of these usually small (h)J couplings are, however, not necessarily straightforward. In the present case of a carbohydrate system, a four-bond classical W coupling, (4)J(HO4,H5), is more reasonable on the basis of, in particular, density functional theory calculations of spin-spin coupling constants at the UB3LYP/6-311G** level of theory. 相似文献