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991.
Based on measurements with hot-wire anemometers in a fully developed turbulent flow in the wake of a cylinder we investigate different aspects of longitudinal and transversal two-point correlations. In particular we use Taylor's hypothesis as well as simultaneous measurements with two X-hot-wire probes, and investigate how these correlations change with the relative orientation of their separation vector with respect to the mean flow direction. For the wake at a distance of eighty cylinder diameters at a Reynolds number Re = 28 000 (Taylor-based Reynolds number Reλ = 290), we find evidence of strong anisotropy. We analyze the data using increment statistics, in particular increment distributions and structure functions. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
992.
Leonid E. Gusel'nikov Vitaly G. Avakyan Stephan L. Guselnikov 《Heteroatom Chemistry》2007,18(7):704-720
Ab initio and DFT thermochemical study of diradical mechanism of 2 + 2 cycloreversion of parent heterocyclobutanes and 1,3‐diheterocyclobutanes, cyclo‐(CH2CH2CH2X), and cyclo‐(CH2XCH2X), where X = NH, O, SiH2, PH, S, was undertaken by calculating closed‐shell singlet molecules at three levels of theory: MP4/6‐311G(d)//MP2/6‐31G(d)+ZPE, MP4/6‐311G(d,p)//MP2/6‐31G (d,p)+ZPE, and B3LYP/6‐311+G(d,p)+ZPE. The enthalpies of 2 + 2 cycloreversion decrease on going from group 14 to group 16 elements, being substantially higher for the second row elements. Normally endothermic 2 + 2 cycloreversion is predicted to be exothermic for 1,3‐diazetidine and 1,3‐dioxtane. Strain energies of the four‐membered rings were calculated via the appropriate homodesmic reactions. The enthalpies of ring opening via the every possible one‐bond homolysis that results in the formation of the corresponding 1,4‐diradical were found by subtracting the strain energies from the central bond dissociation energies of the heterobutanes CH3CH2—CH2XH, CH3CH2—XCH3, and HXCH2—XCH3. The latter energies were determined via the enthalpies of the appropriate dehydrocondensation reactions, using C—H and X—H bond energies in CH3XH calculated at G2 level of theory. Except 1,3‐disiletane, in which ring‐opening enthalpy attains 69.7 kcal/mol, the enthalpies of the most economical ring openings do not exceed 60.7 kcal/mol. The 1,4‐diradical decomposition enthalpies found as differences between 2 + 2 cycloreversion and ring‐opening enthalpies were negative, the least exothermicity was calculated for ⋅ CH2SiH2CH2CH2. The only exception was 1,3‐disiletane, which being diradical, CH2SiH2CH2SiH2, decomposed endothermically. Since decomposition of the diradical containing two silicon atoms required extra energy, raising the enthalpy of the overall reaction to 78.9 kcal/mol, 1,3‐disiletane was predicted to be highly resisting to 2 + 2 cycloreversion. © 2007 Wiley Periodicals, Inc. Heteroatom Chem 18:704–720, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20377 相似文献
993.
Michael Bolte Alexander Degen Stephan Rühl 《Acta Crystallographica. Section C, Structural Chemistry》2001,57(4):446-451
We have determined the crystal structures of 2,2′‐(4‐fluorophenyl)methylenebis(3‐hydroxy‐5,5‐dimethyl‐2‐cyclohexen‐1‐one), C23H27FO4, (I), 2,2′‐(4‐chlorophenyl)methylenebis(3‐hydroxy‐5,5‐dimethyl‐2‐cyclohexen‐1‐one), C23H27ClO4, (II), 2,2′‐(4‐hydroxyphenyl)methylenebis(3‐hydroxy‐5,5‐dimethyl‐2‐cyclohexen‐1‐one), C23H28O5, (III), 2,2′‐(4‐methylphenyl)methylenebis(3‐hydroxy‐5,5‐dimethyl‐2‐cyclohexen‐1‐one), C24H30O4, (IV), 2,2′‐(4‐methoxyphenyl)methylenebis(3‐hydroxy‐5,5‐dimethyl‐2‐cyclohexen‐1‐one), C24H30O5, (V), and 2,2′‐(4‐N,N′‐dimethylaminophenyl)methylenebis(3‐hydroxy‐5,5‐dimethyl‐2‐cyclohexen‐1‐one), C25H33NO4, (VI). Structures (III) to (VI) of these bis‐dimedone derivatives show nearly the same packing pattern irrespective of the different substituent in the para position of the aromatic ring. However, (II) does not fit into this scheme, although the Cl atom is a substituent not too different from the others. The different packing of the fluoro compound, (I), can be explained by the fact that it crystallizes with two molecules in the asymmetric unit, which show a different conformation of the dimedone ring. On the other hand, (I) shows a similar packing pattern to bis(2‐hydroxy‐4,4‐dimethyl‐6‐oxo‐1‐cyclohexenyl)phenylmethane, a compound containing an aromatic ring without any substituent and with Z′ = 2. 相似文献
994.
We present a new type of high resolution sensor for turbulent flow measurements based on the optical detection of a deflected cantilever. The Laser-Cantilever-Anemometer (LCA) can be used in air as well as in water without any changes in setup. Experiments for testing the functionality of this sensor in turbulent air flows show that the measured data with the LCA match the data obtained with a hot-wire anemometer up to several kHz. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
995.
Quentin Coquerel Claire Legendre Jacinthe Frangieh Stephan De Waard Jrme Montnach Leos Cmarko Joseph Khoury Charifat Said Hassane Dimitri Brard Benjamin Siegler Ziad Fajloun Harold De Pomyers Kamel Mabrouk Norbert Weiss Daniel Henrion Pascal Richomme Csar Mattei Michel De Waard Anne-Marie Le Ray Christian Legros 《Molecules (Basel, Switzerland)》2022,27(13)
Voltage-gated Na+ (NaV) channels are significant therapeutic targets for the treatment of cardiac and neurological disorders, thus promoting the search for novel NaV channel ligands. With the objective of discovering new blockers of NaV channel ligands, we screened an In-House vegetal alkaloid library using fluorescence cell-based assays. We screened 62 isoquinoline alkaloids (IA) for their ability to decrease the FRET signal of voltage sensor probes (VSP), which were induced by the activation of NaV channels with batrachotoxin (BTX) in GH3b6 cells. This led to the selection of five IA: liriodenine, oxostephanine, thalmiculine, protopine, and bebeerine, inhibiting the BTX-induced VSP signal with micromolar IC50. These five alkaloids were then assayed using the Na+ fluorescent probe ANG-2 and the patch-clamp technique. Only oxostephanine and liriodenine were able to inhibit the BTX-induced ANG-2 signal in HEK293-hNaV1.3 cells. Indeed, liriodenine and oxostephanine decreased the effects of BTX on Na+ currents elicited by the hNaV1.3 channel, suggesting that conformation change induced by BTX binding could induce a bias in fluorescent assays. However, among the five IA selected in the VSP assay, only bebeerine exhibited strong inhibitory effects against Na+ currents elicited by the hNav1.2 and hNav1.6 channels, with IC50 values below 10 µM. So far, bebeerine is the first BBIQ to have been reported to block NaV channels, with promising therapeutical applications. 相似文献
996.
Low water vapor and air permeability is a persistent challenge in wearable and on-skin electronics, as it reduces wearing comfort, and leads to skin irritation and inflammation in the long term. To tackle this issue, Zheng and coworkers designed a stretchable conductor based on an elastomeric fiber mat coated by liquid metal. After simple activation via stretching, the flexible conductor was endowed with excellent permeability, good stretchability, exceptional electrical stability, and good biocompatibility, ascribed to the mesh-like structure and the vertically buckled structure of the liquid metal. Based on the intriguing properties of the material, it was employed in a multi-functional wearable device, able to detect the heartbeat and sweat while serving as a heating device. The corresponding research has been published in Nature Materials and can be accessed at https://doi.org/10.1038/s41563-020-00902-3. 相似文献
997.
998.
Johannes Wellmann Beate Hartmann Esther-Corinna Schwarze Silke Hillebrand Stephan I. Brueckner Jakob Ley Gerold Jerz Peter Winterhalter 《Molecules (Basel, Switzerland)》2022,27(11)
Previously, different Hydrangea macrophylla ssp. serrata cultivars were investigated by untargeted LC-MS analysis. From this, a list of tentatively identified and unknown compounds that differ significantly between these cultivars was obtained. Due to the lack of reference compounds, especially for dihydro-isocoumarins, we aimed to isolate and structurally characterise these compounds from the cultivar ‘Yae-no-amacha’ using NMR and LC-MS methods. For purification and isolation, counter-current chromatography was used in combination with reversed-phase preparative HPLC as an orthogonal and enhanced purification workflow. Thirteen dihydro-isocoumarins in combination with other metabolites could be isolated and structurally identified. Particularly interesting was the clarification of dihydrostilbenoid glycosides, which were described for the first time in H. macrophylla ssp. serrata. These results will help us in further studies on the biological interpretation of our data. 相似文献
999.
1000.