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排序方式: 共有313条查询结果,搜索用时 15 毫秒
51.
52.
Roksana Kordala-Markiewicz Hubert Rodak Bartosz Markiewicz Filip Walkiewicz Agata Sznajdrowska Katarzyna Materna Katarzyna Marcinkowska Tadeusz Praczyk Juliusz Pernak 《Tetrahedron》2014
Ammonium ionic liquids with the 4-chloro-2-methylphenoxyacetate anion were synthesized and characterized. Physicochemical properties, such as thermal stability, phase transition temperatures, viscosity, density, refractive index, as well as surface activity and herbicidal activity were determined. Improved physicochemical properties suggest a reduced environmental impact of newly formed group of herbicidal ionic liquids (HILs). HILs with a longer substituent can be characterized with better herbicidal activity in comparison with commercial products. 相似文献
53.
Helicenophyrins: Expanded Carbaporphyrins Incorporating Aza[5]helicene and Heptacyclic S‐Shaped Aza[5]helicene Motifs
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Dr. Bartosz Szyszko Monika Przewoźnik Dr. Michał J. Białek Dr. Agata Białońska Prof. Dr. Piotr J. Chmielewski Dr. Jakub Cichos Prof. Dr. Lechosław Latos‐Grażyński 《Angewandte Chemie (International ed. in English)》2018,57(15):4030-4034
Incorporation of phenanthrene into a hexaphyrin(1.1.1.1.1.0) frame resulted in intramolecular ring fusion, thus giving rise to chiral helicenophyrins. These molecules contain helicene and porphyrin features by incorporating either an aza[5]helicene or heptacyclic S‐shaped aza[5]helicene. 相似文献
54.
Photoexcited melanin from retinal pigment epithelium (RPE) has been shown to induce photo-oxidation of ascorbate with concomitant generation of hydrogen peroxide. The aim of this study was to test whether the age-related changes in melanin content and distribution in the RPE affect the susceptibility of RPE cells to ascorbate-mediated photo-oxidation. Our results demonstrate that there is an age-dependent shift in the pathways with which ascorbate interacts in human RPE. In young RPE, melanin-ascorbate interactions may lead to pro-oxidant effects, but in the aged there is no net increase in photo-oxidation in the presence of ascorbate in comparison with samples without ascorbate. However, as ascorbate undergoes light-induced depletion and photogenerates ascorbyl free radical in the old RPE cells with initial yields similar to that observed for young RPE, an influence of ascorbate on oxidation pathways is revealed in the old RPE as well. Interestingly, the pro-oxidant effects of photoexcited melanolipofuscin-ascorbate interactions are greater than for photoexcited melanosomes when normalized to the same melanin content. The pro-oxidant effects of photoexcited melanin-ascorbate interactions are strongly dependent on the irradiation wavelength, this being the greatest for the shortest wavelength studied (340 nm) and steeply decreasing with increasing wavelength but still detectable even at 600 nm. 相似文献
55.
Incorporation of a Phenanthrene Subunit into a Sapphyrin Framework: Synthesis of Expanded Aceneporphyrinoids
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Dr. Bartosz Szyszko Marcin Małecki Dr. Anna Berlicka Michał J. Białek Dr. Agata Białońska Kamil Kupietz Dr. Ewa Pacholska‐Dudziak Prof. Lechosław Latos‐Grażyński 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(22):7602-7608
32‐Hetero‐5,6‐dimethoxyphenanthrisapphyrins—macrocycles that link structural features of polycylic aromatic hydrocarbons and expanded porphyrins—were obtained in a straightforward [3+1] condensation reaction of dimethoxyphenanthritripyrrane and 2,5‐bis(arylhydroxymethyl)heterocyclopentadienes. The highly folded conformation of formally 4 n π‐electron macrocycles causes them to manifest only limited macrocyclic π conjugation as explored by means of NMR spectroscopic and X‐ray structural analyses, and supported by DFT calculations. Although protonation does not change their π‐conjugation characteristics, the cleavage of ether groups at the phenanthrenylene moiety yields nonaromatic 32‐hetero‐5,6‐dioxophenanthrisapphyrins. 相似文献
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The interaction between a semi-large aromatic hydrocarbon compound (perylene) and the TiO2(1 1 0)-(1 × 1) surface under ultra high vacuum conditions has been probed by X-ray photoemission spectroscopy (XPS), ultraviolet photoemission spectroscopy (UPS) and near-edge X-ray absorption fine structure (NEXAFS) methods. UPS measurements of the adsorbate system have been compared with an experimental UPS spectrum of perylene in the gas phase and a calculated spectrum obtained by means of density functional theory (DFT) methods. NEXAFS results of perylene molecules adsorbed on TiO2(1 1 0)-(1 × 1) were compared with data from an α-phase perylene single crystal. A novel analysis of the valence data has been employed to show that no strong chemical interaction takes place between perylene and the TiO2(1 1 0)-(1 × 1) surface. Furthermore, angle-dependent NEXAFS measurements and the growth curve results suggest that the perylene molecules are oriented flat down onto the TiO2 substrate due to weak van der Waals interactions. 相似文献
58.
Jacek Zaleski Mieczysaw Gabryszewski Bartosz Zarychta 《Acta Crystallographica. Section C, Structural Chemistry》2005,61(3):m151-m154
The copper(II) environments for tetrakis(1‐ethyl‐1,2,4‐triazole)dinitratocopper(II), [Cu(NO3)2(C4H7N3)4], and tetrakis(1‐propyl‐1,2,4‐triazole)dinitratocopper(II), [Cu(NO3)2(C5H9N3)4], are distorted square bipyramidal. Both structures are centrosymmetric, with the copper(II) ions located at inversion centers coordinated by four N atoms of four triazole molecules and by two O atoms of two nitrate ions in an elongated octahedral geometry. This elongation is a result of the Jahn–Teller effect. The largest distortion is that of the N—Cu—O angles, which differ from 90° by 5.68 (10)° in the ethyl and 5.59 (8)° in the propyl derivative. 相似文献
59.
The paper presents practical applying of structural topology optimization algorithm based on the formulation of optimal design with compliance minimization. Problem was presented and discussed for several 2D examples. Analysis of local buckling problem was made for various results obtained by the algorithm and approximated into the truss structures. Real bridge load was considered for girders. Topology based optimal girders were compared to typical truss structure. Relation between rods thicknesses was considered. Stress level including buckling in compressed members was examined. (© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
60.
Bartosz Tylkowski Malgorzata Pregowska Emilia Jamowska Ricard Garcia-Valls Marta Giamberini 《European Polymer Journal》2009,45(5):1420-1432
Microcapsules based on a new liquid crystalline lightly cross-linked polyamide, in which the state of order can be triggered by means of external stimuli, such as temperature and light, were prepared by interfacial polymerization. This polyamide exhibited a nematic phase up to 166 °C and it started to decompose at 340 °C; morphological variations of the film were observed by Scanning Electron Microscopy in correspondence to the clearing temperature; moreover, by continuous irradiation with UV light at room temperature, the polymer underwent E–Z photoisomerization. The prepared microcapsules contained either toluene, or concentrated solutions of naphthalene or β-carotene, as the core; in all cases, their outer surface appeared smooth and dense, while heterogeneities could be seen on the inner face. Capsule diameter lay in the range 30–120 μm, depending on the encapsulated material, with quite narrow size distributions. To the authors’ knowledge, this is the first example of microcapsules whose shell is completely constituted by a liquid crystalline lightly cross-linked polymer. Release experiments of β-carotene were performed in water and in tetrahydrofuran. β-Carotene release in water at 20 °C was strongly influenced by UV irradiation: in the absence of irradiation, it was practically negligible while, when microcapsules were submitted to continuous irradiation with UV light, β-carotene was quickly released and reached 100% release after 5 min. Preliminary experiments concerning the effect of temperature and of a swelling solvent, such as THF, on release, were also performed. 相似文献