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11.
R. Carlisle Chambers Elissa J. Bell Tauni M. Records Anna Cherian Karen Ragan Bonnie Swartout 《Liquid crystals》2013,40(10):1221-1226
The influence on the optical properties of cholesteric liquid crystal displays (LCDs) was examined for neutral molecule binding by mesogen/receptors in the mesomorphic phase. The motivation was to prepare neutral molecule sensors that use a colour change to signal analyte binding. A receptor that binds barbiturate analytes was modified with two or one cholesteryl groups to yield compounds 2 and 3, respectively. LCDs were prepared by incorporating one of the receptor/mesogen compounds into a cholesteric LC blend along with a potential H‐bonding guest. The optical properties of the LCDs were then determined by measuring the absorbance of the displays. For various LCDs, the colour of the display depended upon several factors: the amount of guest molecule used, the number of cholesteryl side chains on the receptor and the mole concentration of receptor/mesogen in the blend. In particular, complementary host/guest binding of H‐bonding analytes by the bis(cholesteryl) receptor 2 in a cholesteric LCD caused a change of up to +70 nm, which was observed by the naked eye as a blue‐to‐orange colour change. Control experiments confirm that the colour of an LCD is a consequence of molecular recognition in the mesomorphic phase. 相似文献
12.
Patel B Carlisle J Bottle SE Hanson GR Kariuki BM Male L McMurtrie JC Spencer N Grainger RS 《Organic & biomolecular chemistry》2011,9(7):2336-2344
Acyclic bissulfonylnitroxides have never been isolated, and degrade through fragmentation. In an approach to stabilising a bissulfonylnitroxide radical, the cyclic, peri-substituted N,N-bissulfonylhydroxylamine, 2-hydroxynaphtho[1,8-de][1,3,2]dithiazine 1,1,3,3-tetraoxide (1), has been prepared by formal nitrogen insertion into the sulfur-sulfur bond of a sulfinylsulfone, naphtho[1,8-cd][1,2]dithiole 1,1,2-trioxide. The heterocyclic ring of 1 is shown to adopt a sofa conformation by X-ray crystallography, with a pseudo-axial hydroxyl group. N,N-Bissulfonylhydroxylamine 1 displays high thermal, photochemical and hydrolytic stability compared to acyclic systems. EPR analysis reveals formation of the corresponding bissulfonylnitroxide 2 upon oxidation of 1 with the Ce(IV) salts CAN and CTAN. Although 2 does not undergo fragmentation, it cannot be isolated, since hydrogen atom abstraction to reform 1 occurs in situ. The stability and reactivity of 1 and 2 are compared with the known cyclic benzo-fused N,N-bissulfonylhydroxylamine, N-hydroxy-O-benzenedisulfonimide (6), for which the X-ray data, and EPR of the corresponding nitroxide 10, are also reported for the first time. 相似文献
13.
Media literacy perspectives 总被引:2,自引:0,他引:2
JA Brown 《The Journal of communication》1998,48(1):44-57
Media literacy education involves cognitive processes used in critical thinking. Media workshops and curricula emphasize moral values (the defensive, inoculation approach), discriminating responsiveness (the critical viewer), antimedia resistance, and consumer revolution. Inductive media literacy programs promote independent critical thinking. Media content is a limited predictor of potential effects of media exposure. Meaning is situated in what audiences bring to their media experience (selective perception), the context in which they use media (accommodation), and how and why they use the medium (use and gratifications). To succeed, a curricular program of media literacy requires collaboration among teachers, administrators, specialists, and parents. 相似文献
14.
The crystal and molecular structure of the thermodynamically more stable isomer of 24,25-dibromolanost-8-en-3-yl acetate, the A form, has been solved by the heavy-atom method and refined by full-matrix least-squares methods to a finalR-value of 0.153 for 2354 reflections. The crystals are orthorhombic:P212121,a = 40.889,b = 9.990,c = 7.839Å,Z = 4. Some difficulties were encountered owing to both radiation damage and the unusual positions of the bromine atoms. The analysis shows the configuration at C(24) to be 24S, and the rest of the structure does not reveal any unexpected features. 相似文献
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J. A. Carlisle L. J. Terminello A. V. Hamza E. A. Hudson E. L. Shirley F. J. Himpsel 《Molecular Crystals and Liquid Crystals》2013,570(1):819-824
Abstract The full spectrum of occupied and unoccupied σ and π orbitals is presented for solid C60, C70, and graphite, using Cls emission and absorption spectroscopy. There are significant diffcrences between C60 and C70, and even larger changes relative to their infinite analog graphite (C∝). A comparison is made with photocmission and inverse photoemission results, along with first principles quasiparticle calculations. 相似文献
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Z.M. Babar Wan Mohd Azizi Solachuddin JA Ichwan Qamar Uddin Ahmed Abul Kalam Azad Imranul Mawa 《Natural product research》2019,33(15):2266-2270
The current study provides a way of extraction for both active NSO and WSE from Nigella sativa seeds using 98% methanol. About 1?kg of ground seeds was macerated by 1:2.5 w/v (g/mL) for 72?hours. After rotary evaporation and 7 days of continuous drying and chilling at 50 and 4?°C, NSO and WSE were obtained at the same instant. Solubility tests of 24 solvents and 11 thin layer chromatographic analyses while 2, 2-diphenyl-1-picrylhydrazyl free radical scavenging assay of NSO (73.66) , WSE (33.32) and NSO?+?WSE (78.22) against ascorbic acid (IC50?=?4.28?mg/mL) was performed. WSE was found to be highly soluble in water and 5% NaOH exhibiting the same Rf value of 0.95 for EtOH:DMSO (9:1) against the honey. WSE has revealed more than twofold higher anti-oxidant activity than others. Formulation of WSE with Tualang honey may provide better targeted hydrophilic drug delivery systems. 相似文献
20.
J. A. Carlisle S. R. Blankenship R. N. Smith A. Chaiken R. P. Michel T. van Buuren L. J. Terminello J. J. Jia T. A. Callcott D. L. Ederer 《Journal of Cluster Science》1999,10(4):591-599
Soft x-ray fluorescence spectroscopy has been used to examine the electronic structure of deeply buried silicide thin films that arise in Fe/Si multilayers. These systems exhibit antiferromagnetic (AF) coupling of the Fe layers, despite their lack of a noble metal spacer layer found in most GMR materials. Also, the degree of coupling is very dependent on preparation conditions, especially spacer layer thickness and growth temperature. The valence band spectra are quite different for films with different spacerlayer thickness yet are very similar for films grown at different growth temperatures. The latter result is surprising since AF coupling is strongly dependent on growth temperature. Combining near-edge x-ray absorption with the fluorescence data demonstrates that the local bonding structure in the silicide spacer layer in epitaxial films which exhibit AF coupling are metallic. These results indicate the equal roles of crystalline coherence and electronic structure in determining the magnetic properties of these systems. 相似文献