The crystal structure and molecular conformation of 2-cyano-4-bromo-4′-N,N-diethylaminoazobenzene (C17H17N4Br, mol. wt. = 357·2 a.m.u) has been determined from X-ray diffraction data; triclinic, P (No. 2), a = 10·132(11) Å, b = 12·216(16) Å, c = 6·966(11) Å, α = 104·21(9)°, β = 92·67(12)°, γ = 97·22(7)°, V = 826·5(9) Å3, Z = 2, Dc = 1·436 g cm?3, F(000) = 378, λ(MoKα) = 0·71069 Å, μ(MoKα) = 26·0 cm?1. The structure was solved by the multiple solution direct method and refined by full-matrix least-squares to R = 0·059 for 1538 independent observed reflections. The azobenzene skeleton is planar to within 0·06 Å. Most significant bonding data are: NN, 1·290(8) Å; BrC, 1·866(6) Å; mean CN (azo) 1·380(8) Å; NNC, 113·6(4) and 115·3(4)°; NCC (cis relative to NN) 125·9(4)° and 126·7(4)°; NCC (trans) 116·8°(5)° and 116·1(4)°. 相似文献
Three-block copolymers polyamide-block-polyX-block-polyamide (where X is styrene, ethylene-co-1-butene, and others) are able to improve substantially the toughness of poly(ϵ-caprolactam). Outer blocks of these copolymers are able to take part in folding lamellae of semi-crystalline polyamide, inner blocks are not. They operate as a spacer, meaning that the end blocks of copolymers capable of folding become parts of different lamellae, or that the unfoldable part of a block copolymer is pushed out of a folding lamella with a certain probability of the remaining outer block taking part in folding another lamella. This increases the number of tie-molecules. 相似文献
Summary The synthesis is reported of copolymers of styrene with methacrylic acid and of methyl methacrylate with methacrylic acid by radical copolymerization, of copolymers of methyl methacrylate with methacrylic acid by partial alkaline hydrolysis of poly(methyl methacrylate), and of block copolymers of styrene with methacrylic acid. Modified titration curves of all these copolymers were recorded in water and water-ethanol solutions. In a solution containing 50 mass.% ethanol, only small differences could be observed between the potentiometric behaviour of the individual copolymers and polymethacrylic acid. Also, there were no essential differences in any of the solvents used between the potentiometric behaviour of block copolymers of styrene with methacrylic acid, on the one hand, and polymethacrylic acid, on the other. On the contrary, maxima and minima were always observed on the modified titration curves of statistical copolymers with a higher content of the hydrophobic comonomer in solutions with a high water content. Thus, using the modified titration curves, it is possible to decide whether a given copolymer is of the block or statistical type. 相似文献
The investigation of microstructure, some electrical and optical parameters of transparent ThO2-15 mol % yo1.5 ceramics has shown: (a) a very low porosity, close to zero; (b) a higher electrical conductivity than is usual for ThO2 ceramics of the same composition, with the activation energy 1.12 eV; (c) a relative permittivity r 33 under the given conditions; (d) confirmation of a single-phase fluorite-type cubic structure by means of Raman and infrared spectra. 相似文献
Multimedia Tools and Applications - New mobile applications need to estimate user activities by using sensor data provided by smart wearable devices and deliver context-aware solutions to users... 相似文献
Information Systems Frontiers - What is happening in hacker’s minds when they are committing criminal activities? How black hat hackers manage nerves, which is about managing fear and... 相似文献
Pattern Analysis and Applications - Nearest neighbor search is a powerful abstraction for data access; however, data indexing is troublesome even for approximate indexes. For intrinsically... 相似文献
Numerous visual notations are present in technical and business domains. Notations have to be cognitively effective to ease the planning, documentation, and communication of the domains’ concepts. Semantic transparency (ST) is one of the elementary principles that influence notations’ cognitive effectiveness. However, the principle is criticized for not being well defined and challenges arise in the evaluations and applications of ST. Accordingly, this research’s objectives were to answer how the ST principle is defined, operationalized, and evaluated in present notations as well as applied in the design of new notations in ICT and related areas. To meet these objectives, a systematic literature review was conducted with 94 studies passing the selection process criteria. The results reject one of the three aspects, which define semantic transparency, namely “ST is achieved with the use of icons.” Besides, taxonomies of related concepts and research methods, evaluation metrics, and other findings from this study can help to conduct verifiable ST-related experiments and applications, consequently improving the visual vocabularies of notations and effectiveness of the resulting diagrams.
Intelligent Service Robotics - Walking robots are considered as a promising solution for locomotion across irregular or rough terrain. While wheeled or tracked robots require flat surface like... 相似文献
The extraction of raw materials is associated with energy input and CO2 emissions. What is obvious for extraction from mining, however, also applies to recycling. Mostly, recycling is preferred for reasons of climate protection or because of the geological scarcity of raw materials, which is controversially discussed. While in mining, the declining ore grade is a driver for the energy demand, in case of recycling it is the dissipation of materials into products or waste. As concentration decreases, the effort required also increases disproportionately. The “closing the loop” metaphor of Circular Economy is therefore inappropriate in its stricter meaning. It is rather about optimizing the overall system and finding the optimal recycling rate. However, first, it must be clarified what the political goals for Circular Economy are. 相似文献