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排序方式: 共有110条查询结果,搜索用时 15 毫秒
1.
V. Hamplov A. Bubnov M. Ka par V. Novotn D. Pociecha M. Glogarov 《Liquid crystals》2003,30(5):627-631
A new series of chiral liquid crystalline materials having the same rigid core containing a keto group, and various numbers of ( S )-lactate groups in the chiral segment, has been synthesized and studied. All the compounds contain a branched terminal alkyl chain derived from ( S )-2-methylbutanol. The influence of the number of lactate units on mesogenic behaviour has been studied. All the compounds show the paraelectric SmA phase and the ferroelectric SmC * phase over rather wide temperature ranges. The antiferroelectric SmC * A phase was observed for the compound possessing two lactate groups. 相似文献
2.
par Jean-michel Vierfohd Yvette Mettey Line Mascrier-Demagny Marcel Miocque 《Tetrahedron letters》1981,22(13):1219-1222
An original one-pot ayntheais of 4,7-diazaindoles is achieved by metalation of methylpyrazines or methylquinoxaline wich are then condensed with an aromatic nitrile: an intermediate imine-enamine is formed which leads, by intramolecular cyclization, to diazaindoles. 相似文献
3.
Oscillating Chemical Reactions. III. Effects of the Temperature and Chemical Composition on the ‘Induction Period’ of the BrO /Ce4+/Cyclohexanon and BrO /Ce4+/Cyclopentanon Systems A study of the influence of the temperature and composition of the BrO/Ce4+/cyclohexanon (S1) and BrO/Ce4+/cyclopentanon (S2) systems has shown a very particular behaviour for τind. for a given ratio α of concentrations: Moreover, for 0.27 ? α ? 0.32, log1/τind. is no longer a linear function of the inverse of the temperature: a break in the line log1/τind. = f(1/T) occurs. 相似文献
4.
Věra Hamplová Alexej Bubnov Corresponding author Miroslav Kašpar Vladimíra Novotná Yveta Lhotáková Milada Glogarová 《Liquid crystals》2013,40(12):1463-1469
New chiral liquid crystalline materials containing a keto group and two lactate units attached to the mesogenic core have been synthesized and studied. All the new compounds show the paraelectric SmA, ferroelectric SmC* and antiferroelectric SmC*A phases each over rather broad temperature ranges. The properties of the phases were characterized by DSC, electro-optical and dielectric studies. The spontaneous polarization, tilt angle, helical pitch, and switching times were determined for the polar phases. 相似文献
5.
Alexey Bobrovsky Valery Shibaev Věra Hamplová Miroslav Kašpar Vladimira Novotna Milada Glogarová 《Liquid crystals》2013,40(9):989-997
A photoinduced phase transition and helix untwisting in a new liquid crystal forming the SmC* phase were studied in detail. The compound consists of a cinnamoyl photosensitive fragment with C?=?C double bond capable of photoisomerisation and photocycloaddition. It was shown that ultraviolet (UV) irradiation (365 nm) induces an extreme decrease in phase transitions temperatures (SmC*–SmA*, SmA*–N*, N*–I). Vertically aligned samples in the SmC* phase cause selective light reflection in the visible spectral range. The light action results in a noticeable helix untwisting that causes a shift in the selective light reflection peak to the long-wavelength spectral region. The temperature dependence of spontaneous polarisation P s was measured and it was found that UV irradiation induces a decrease in the values of P s. Photo-optical phenomena taking place in the liquid crystal are attributed to the formation of photoproducts having low anisometry, which disrupts mesophases. 相似文献
6.
New series of liquid crystals with an alkyl-lactate chiral chain and four aromatic rings in the mesogenic core and chloro-substitution were synthesized. For all the compounds studied, SmA and SmC* phases, existing over very broad temperature ranges, were detected and characterized. Mesomorphic properties were analysed with respect to the lengths of the chiral and/or non-chiral chains. 相似文献
7.
The hitherto analyses of elastic collisions of charged nucleons involving common influence of Coulomb and hadronic scattering have been based practically on West and Yennie formula. However, this approach has been shown recently to be inadequate from experimental as well as theoretical points of view. The eikonal model enabling to determine physical characteristics in impact parameter space seems to be more pertinent. The contemporary phenomenological models admit, of course, different distributions of collision processes in the impact parameter space and cannot give any definite answer. Nevertheless, some predictions for the planned LHC energy that have been given on their basis may be useful, as well as the possibility of determining the luminosity from elastic scattering. 相似文献
8.
F. Soška F. Beneš S. Jura B. Gross Z. šimša F. Kosek J. Horák J. Kašpar K. čermák J. Lipták M. Ryba E. F. Holländer A. Havránek E. Havránková A. Kochanovská J. Sommer F. Vilím P. Lukáš C. Rumler S. Kadečková F. Vávra M. Matyáš J. Beneš J. Kučera L. DvoŘák Z. KudĚlásek J. Hájek A. Marek Z. Malec J. Janků B. Sojka L. Karmazin M. Ryšavá L. Janko K. Huml 《Czechoslovak Journal of Physics》1961,11(11):852-862
9.
Local Dispersive and Strichartz Estimates for the Schrödinger Operator on the Heisenberg Group 下载免费PDF全文
Hajer Bahouri & Isabelle Gallagher 《数学研究通讯:英文版》2023,39(1):1-35
It was proved by Bahouri et al. [9] that the Schrödinger equation on
the Heisenberg group $\mathbb{H}^d,$ involving the sublaplacian, is an example of a totally
non-dispersive evolution equation: for this reason global dispersive estimates
cannot hold. This paper aims at establishing local dispersive estimates on $\mathbb{H}^d$ for the linear Schrödinger equation, by a refined study of the Schrödinger kernel $S_t$ on $\mathbb{H}^d.$ The sharpness of these estimates is discussed through several
examples. Our approach, based on the explicit formula of the heat kernel on $\mathbb{H}^d$ derived by Gaveau [19], is achieved by combining complex analysis and
Fourier-Heisenberg tools. As a by-product of our results we establish local Strichartz estimates and prove that the kernel $S_t$ concentrates on quantized horizontal hyperplanes of $\mathbb{H}^d.$ 相似文献
10.
In this paper, we consider self-mappings defined on a metric space endowed with a finite number of graphs. Under certain conditions imposed on the graphs, we establish a new fixed point theorem for such mappings. The obtained result extends, generalizes and improves many existing contributions in the literature including standard fixed point theorems, fixed point theorems on a metric space endowed with a partial order and fixed point theorems for cyclic mappings. 相似文献