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61.
The orientational order of a liquid crystalline side chain polysiloxane has been investigated by means of polarized light spectroscopy and dielectric relaxation measurements. The order parameters (P2) and (P4) have been determined as a function of the temperature for the smectic and nematic phases. The orienting properties of the polysiloxane investigated have been compared with those of a polysiloxane with the same mesogenic groups, but a shorter spacer. 相似文献
62.
Branowska D 《Molecules (Basel, Switzerland)》2005,10(1):274-278
Inverse electron demand Diels-Alder reaction of functionalized 5,5'-bi-1,2,4- triazines with bicyclo[2.2.1]hepta-2,5-diene in boiling p-cymene leads to a range of 6,6'- disubstituted-2,2'-bipyridines in good yield. 相似文献
63.
A nematogenic side-chain polysiloxane is investigated by means of absorption and fluo-rescence spectroscopy.4-Dimethylamino-4′-nitrostilbene (DANS) is dissolved in the poly-meric matrix as a guest probe. The orientational order and the molecular distribution function have been determined from measurements of polarized absorption and fluorescence spectra. It has been found that fluorescence spectroscopy affords a method for determination of the phase transition temperatures of liquid–crystalline polymers. © 1993 John Wiley & Sons, Inc. 相似文献
64.
Damian Wojcieszak Danuta Kaczmarek Jaroslaw Domaradzki Anna Lukowiak Wieslaw Strek 《Central European Journal of Physics》2013,11(2):239-244
In this work analysis of the structural and optical properties of TiO2 thin films doped with terbium has been described. Samples were prepared by a high energy reactive magnetron sputtering process under low pressure of oxygen plasma. X-ray diffraction results have shown that different TiO2 crystal forms have been produced, depending on the amount of Tb dopant. The undoped matrix had rutile structure with crystallites with a size of 8.7 nm, while incorporation of 0.4 at. % of Tb into the film during the sputtering process resulted in anatase structure with bigger crystallites (11.7 nm). Increasing the amount of terbium up to 2 at. % and 2.6 at. % gave rutile structure with crystallites with a size of 6.6 nm for both films. However, Raman spectroscopy has revealed that in the case of TiO2:(2 at. % Tb), except for the rutile form, the presence of fine-crystalline anatase was observed. Moreover, the lack of Raman peaks shift attests to the lack of stress in the titania lattice of all of the TiO2:Tb films. This fact indicates localization of Tb3+ ions on the surface of TiO2 nanocrystals. In the case of optical investigation, results have shown that doping with terbium has a significant influence on the properties of TiO2, but it does not decrease the high transparency of the matrix. The observed changes of the transmission characteristics were produced only due to modification of the TiO2:Tb structure. Photoluminescence measurements have shown that emission of light from TiO2:Tb films occurs when the amount of terbium is 2.6 at. %. Based on the obtained results a scheme of direct energy transfer from titanium dioxide matrix (with rutile structure) to Tb3+ ions has been proposed. 相似文献
65.
Karolina Sieradzka Danuta Kaczmarek Jerzy Morgiel Jaroslaw Domaradzki Eugeniusz Prociow Bogdan Adamiak 《Central European Journal of Physics》2013,11(2):251-257
Transparent oxide semiconducting thin films based on mixed Ti-V oxides were prepared using a modified reactive magnetron sputtering method. Based on structural investigations performed with the help of x-ray diffraction and transmission electron microscopy analysis, two distinct regions in the prepared thin film have been observed: a nanocrystalline TiO2-V2O3-V2O5 mixed composition, and a thin layer consisting of amorphous phase and nanocystalline TiO2 phase deposited directly at the substrate. Optical measurements show excellent transmission in the visible spectral range of 73%, on average. Resistivity of the thin film was found at the order of 105 Ω cm at room temperature. The preparation of mixed Ti-V oxides provides a combination of high transparency and semiconducting properties. 相似文献
66.
A mathematical formalism related to the approximate as well as the accurate interferometric data reduction schemes is briefly outlined and subsequently applied in the reconstruction of the assumed (Luneburg) axisymmetric refractive index distribution. The presented comparative analysis confirms the generally held opinion that the approximate methods (“straight-line” and Kokubun-Iga approaches) may provide quite reasonable results in the examination of refractively inhomogeneous disturbances characterized by weak gradient and moderate index variation. On the other hand, the accurate scheme for transverse interferometric data interpretation and reduction, based on the close-form correlation between the fringe shift and the deflection function, [1] remains the only method for reliable reconstruction of strongly refracting index profiles, independently of magnitude of refraction and ambiguity of the fringes. This fact is of considerable importance for transverse interferometry of fibers (preform rods) and/or GRIN-rod lenses characterized by high numerical apertures. 相似文献
67.
A paraxial ray equation is used to evaluate refractive index profiles for a family of radially symmetric planar waveguide lenses. Two cases are considered: the (theoretically) full-aperture solution, and the solution with smooth index variation (non-full-aperature case). In deriving the latter case a new method has been applied that consists of the proper choice of a continuous deflection function. Both types of index profiles are described by exceptionally simple formulas. 相似文献
68.
Danuta Wróbel Izabela Hanyż Renata Bartkowiak Rodica M. Ion 《Journal of fluorescence》1998,8(3):191-198
Porphyrin dyes fulfill an essential function in photosynthesis and are important in photodynamic therapy and in a range of electronic devices. Their spectroscopic characteristics may play a crucial role in these processes. The spectral properties of two porphyrin dyes: tetraphenylporphyrin and tetraphenysulfporphyrin in organic solvents (acetone, chloroform, methyl alcohol, and dimethyl-sulfoxide) and in polyvinyl alcohol and poly(methylmethacrylate) films have been investigated. Absorption, fluorescence, and microsecond time-resolved delayed luminescence spectra have been measured at room temperature. The existence of different aggregated dye forms in the ground and excited states has been demonstrated. The manifold of dye species depends on the solvent/polymer. In the case of the polymers, it also depends on the solvent used to coat the polymer film. Delayed luminescence spectra and decay times of the two porphyrins in the different solutions and in polymeric matrices suggest that different mechanisms of deexcitation of the singlet excited states may be responsible for their generation in these and other porphyrin dyes. 相似文献
69.
Quinoline-2-carboxylic acid (quinaldic acid), C10H7NO2, crystallizes in the monoclinic space group P21/c, a =9.724(1) Å, b = 5.937(1) Å, c = 27.545(2) Å, = 90.15(1)°, z = 4, and occurs in the crystal in two tautomeric forms: the neutral molecule and the zwitterion, with molecular ratio 1:1. The compound can be named quinoline-2-carboxylic acid quinolinium-2-carboxylate. The crystal structure is built up of tautomeric pairs consisting of C9H6NCOOH and C9H6NH+COO– moieties, held up together by hydrogen bonds. 相似文献
70.
Zofia Urbańczyk-Lipkowska Kinga Suwińska Danuta Mostowicz Marek Chmielewski 《Journal of chemical crystallography》1995,25(10):693-699
Geometry and molecular conformation of theN-toluenesulfonyl1 andN-acetyl-2 derivatives of peracetylated 2-C:1-N-carbonyl-2-deoxy--d-glucopyranosylamine were investigated with the use of X-ray diffraction methods. Compound1 (C20H23NSO10) crystallizes in the monoclinic P21 space group, withZ=2 anda=8.238(1),b=7.988(1),c=16.928(2)Å, =99.12(1)°. Compound2 (C15H19NO9) crystallizes in orthorhombic P212121 space group withZ=4 anda=8.385(1),b=8.550(1),c=24.000(2) Å. Analysis of differences in bond lengths and angles between compounds1 and2 and other compounds of this class showed that the electronwithdawing effect by the residue located at the nitrogen atom can be manifested by lengthening of the -lactam C-N bonds, with simultaneous shortening of the distance between two carbon atoms at the ring fusion. Semi-empirical calculations suggested that the title compounds displayed two positively charged centers, susceptible for attack of nucleophiles, one at the carbonyl group of -lactam and the second at the anomeric carbon atom. Atomic charges, however, calculated for compounds1 and2 did not explain their different reaction directions during alcoholysis.Part 3. For part 1 and 2, see Refs. 5 and 6. 相似文献