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141.
Filip Bureš Oldřich Pytela Milan Kivala François Diederich 《Journal of Physical Organic Chemistry》2011,24(4):274-281
A representative data set has been gained by the measurement of the electronic absorption spectra of 12 systematically selected push–pull systems with an intramolecular charge‐transfer (CT) absorption and the general structure D–π–A (D = donor, A = acceptor) featuring electron‐withdrawing CN groups, electron‐donating N(CH3)2 groups, and various π‐conjugated backbones in 32 solvents with different polarities. The longest‐wavelength absorption maxima λmax and the corresponding wavenumbers $\tilde {v}_{{\rm max}} $ were evaluated from the UV/Vis spectra measured in 32 well‐selected solvents. The D–π–A push–pull systems were further characterized by quantum‐chemical quantities and simple structural parameters. Structure–solvatochromism relationships were evaluated by multidimensional statistic methods. Whereas solvent polarizability and solvent cavity size proved to be the most important factors affecting the position of λmax, the solvent polarity was less important. The most important characteristics of organic CT compounds are the energy of the LUMO, the permanent dipole moment, the COSMO (COnductor‐like Screening MOdel) area, the COSMO volume, the number, and ratio of N,N‐dimethylamino and cyano groups, and eventually the number of triple bonds (π‐linkers). A relation between the first‐order polarizability α, the longest‐wavelength absorption maxima λmax, and the structural features has also been found. The higher‐order polarizabilities β and γ are not related to the observed solvatochromism. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
142.
Dean P Lim YL Valavanis A Kliese R Nikolić M Khanna SP Lachab M Indjin D Ikonić Z Harrison P Rakić AD Linfield EH Davies AG 《Optics letters》2011,36(13):2587-2589
We demonstrate terahertz (THz) frequency imaging using a single quantum cascade laser (QCL) device for both generation and sensing of THz radiation. Detection is achieved by utilizing the effect of self-mixing in the THz QCL, and, specifically, by monitoring perturbations to the voltage across the QCL, induced by light reflected from an external object back into the laser cavity. Self-mixing imaging offers high sensitivity, a potentially fast response, and a simple, compact optical design, and we show that it can be used to obtain high-resolution reflection images of exemplar structures. 相似文献
143.
Milan Hladík 《Optimization Letters》2014,8(7):1985-1997
Interval linear programming addresses problems with uncertain coefficients and the only information that we have is that the true values lie somewhere in the prescribed intervals. For the inequality constraint problem, computing the worst case scenario and the corresponding optimal value is an easy task, but the best case optimal value calculation is known to be NP-hard. In this paper, we discuss lower and upper bound approximation for the best case optimal value, and propose suitable methods for both of them. We also propose a not apriori exponential algorithm for computing the best case optimal value. The presented techniques are tested by randomly generated data, and also applied in a simple data classification problem. 相似文献
144.
新疆广播电视大学的网络教学平台是新疆发展远程教育的骨干力量,提供双语教学,能够满足绝大部分教学需求,但是在教学内容与平台智能方面还未实现精细化教学的目标,难以实现因材施教.本文针对上述问题,引入了个性化学习理论,在现有网络教学平台上设计网上课程个性化学习系统架构,并对系统中的资源建设与管理、个性化设计以及安全性机制进行了探讨.网上课程个性化学习系统可以在确保教学平台安全可信的前提下提高教学质量,有利于学生的个人发展. 相似文献
145.
The methods of theoretical chemistry have been used to elucidate molecular properties of selected and novel antiangiogenic
agents (semaxanib, sunitinib, N-methylsunitinib, sorafenib, motesanib, ABT-869, vatalanib, vandetanib, AEE 788, CP-547632, A-1, A-2, A-3, and A-4). The geometries
and energies of these drugs have been computed using HF/6-31G(d), Becke3LYP/6-31G(d) and Becke3LYP/6-31++G(d,p) model chemistries.
Wherever possible the most stable conformations of inhibitors studied are stabilized by means of intramolecular hydrogen bonds.
Water has a remarkable effect on the geometry of the antiangiogenic agents studied. Computed partition coefficients (ALOGPS
method) varied between 2.3 and 5. Compounds studied are described as lipophilic inhibitors. Semaxanib is inhibitor with lowest
lipophilicity. The antiangiogenic agents studied are only slightly soluble in water; their computed solubility (log S) from interval between −3.4 and −5.4 is sufficient for fast absorption. Selection criteria for drug-like properties of VEGFR2
inhibitors investigated were designed. Based on these criteria, three compounds (A-2, A-3, and A-4) were selected for synthesis
and biological testing for antianiogenic activity on VEGFR2 receptor. 相似文献
146.
A new family of five-membered cyclic nitrones bearing functional groups at positions 2 and 5 were tested in 1,3-cycloadditions with various dipolarophiles. These reactions gave the corresponding cycloadducts as single diastereomers in high yields. The reaction scope was examined, 23 compounds were isolated and fully characterized. The comparison of the reactivity was carried out by a study of reaction conversions while different nitrones or dipolarophiles were used. In addition, the exceptional reactivity of nitrone bearing benzylamino group in position 2 was studied. The formation of the nitrone complex and evaluation of its reactivity in 1,3-DC is presented. 相似文献
147.
Zi Jun Wang Milan Maric 《Journal of polymer science. Part A, Polymer chemistry》2013,51(13):2970-2978
Candidate materials for low‐loss optical waveguides based on poly(glycidyl methacrylate‐ran‐pentafluostyrene) [P(GMA‐ran‐PFS)] copolymers were synthesized by nitroxide mediated polymerization (NMP) initiated with BlocBuilder® [N‐(2‐methylpropyl)‐N‐(1‐diethlphosphono‐2,2‐dimethylpropyl)‐O‐(2‐carboxylprop‐2‐yl) hydroxylamine] bearing a succinimidyl ester group (NHS‐BlocBuilder) at 90 °C in 1,4 dioxane. The copolymerizations yielded copolymers with low dispersity Mw/Mn between 1.2 and 1.4. The core structure of single‐mode channel waveguides was fabricated by direct UV lithographic patterning. The copolymers with low Mw/Mn resulted in line width roughness (LWR) of about 0.16 μm, whereas LWR of copolymers with Mw/Mn=3.5 but similar compositions was about 0.5 μm. The improvement in microstructural control allotted by NMP permitted finer pattern replication for copolymers desired for optical waveguides, as suggested for photoresist polymers. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2970–2978 相似文献
148.
The present paper deals with the evaluation of nimesulide, 2-phenoxy-4-nitroaniline, the main hydrolytic degradation product
of nimesulide, of methylparaben and propylparaben, and eventually of 4-hydroxybenzoic acid by HPLC with UV detection at 254
nm in syrup as a pharmaceutical formulation. HPLC analysis was employed on the reversed phase C18 with methanol and 0.01 M
dibasic ammonium phosphate (ρ
r = 60: 40, pH 4.0). Validation was performed using standards and a pharmaceutical preparation containing the compounds described
above. 相似文献
149.
Josef Mlek Jindich Ne
as Milan Pokorný Maria E. Schonbek 《Mathematische Nachrichten》1999,199(1):97-114
In this paper, we exclude the possibility of existence of a singular solution of the selfsimilar type proposed by Jean Leray More precisely, using a slightly stronger hypothesis we give a simpler proof to the analogous result established by J. Ne?as, M. Rú?i?ka and V. ?verák. We also discuss the possible existence of a singular solution of pseudo-selfsimilar type. 相似文献
150.
We consider the steady plane flow of certain classes of viscoelastic fluids in exterior domains with a non-zero velocity prescribed at infinity. We study existence as well as asymptotic behaviour of solutions near infinity and show that for sufficiently small data the solution decays near infinity as fast as the fundamental solution to the Oseen problem. 相似文献