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991.
JPC – Journal of Planar Chromatography – Modern TLC - High performance thin-layer chromatography (HPTLC) combined with densitometry has been used for analysis of the triterpenoid... 相似文献
992.
13C CP MAS NMR and GIAO-CHF calculations of coumarins 总被引:1,自引:0,他引:1
13C cross-polarization magic-angle spinning NMR spectra were recorded for a series of solid coumarins. Ab initio calculations of shielding constants were performed with the use of GIAO-CHF method. The combined CPMAS NMR and theoretical approach was successful in characterizing solid-state conformations of coumarins; a relationship sigma (ppm) = -1.032 xdelta + 205.28 (R(2) = 0.9845) can be used to obtain structural information for coumarins, for which solid-state NMR or crystal structure data are not available. 相似文献
993.
Summary An equilibrium sandwich chamber for continuous thin-layer chromatography was used to study overloaded systems. Mixtures of two or three dyes were used as the model samples, and wide starting zones were formed (volume-overloaded systems). The movement of the zones was recorded during continuous elution. The effect of sample volume and the mode of development (isocratic or gradient) on the maximum separation yield was investigated. A computer program was developed for the calculation of the final RF values for the front and rear edges of the bands.Satisfactory agreement was found between the experimental RF values of zone boundaries and the values predicted by computer simulation.Presented at the 2nd International Symposium on Preparative and Up-Scale Liquid Chromatography, February 1–3, 1988, Baden-Baden (FRG). 相似文献
994.
Functional derivative δE/δρ in calculation of chemical potential for the Kohn–Sham electronic system
Katarzyna Tkacz-samiech W. S. Ptak A. Koleyski J. Mrugalski 《International journal of quantum chemistry》1994,51(6):569-575
A method for finding the chemical potential for an electronic system with density ρ = Σρi represented within the Kohn–Sham approximation is proposed. To find the chemical potential of the system under consideration, we propose to refer to the definition μ = δE/δρ and to apply the mathematical properties of functional derivatives. Particularly, in the case examined, the result μ = μ( r ) ≠ const has been obtained, which may be explained in the framework of the calculus of variation. Taking the limit limr→∞ μ( r ) as the best approximation to the proper equilibrium chemical potential of a free atom, one obtains μ = ?I, where I denotes first ionization energy. A possibility of further applications of the proposed method in relation to crystalline systems is also discussed. © 1994 John Wiley & Sons, Inc. 相似文献
995.
Katarzyna Ostrowska 《Monatshefte für Chemie / Chemical Monthly》2002,133(3):249-254
Summary. The application of derivatives of the easily decomposing weak bases formamide, semicarbazide, urea, or formamidine in the
synthesis of β-aminoenones is described. These compounds readily undergo transamination with strong bases, thus opening the
way to various heterocyclic compounds.
Received July 16, 2001. Accepted (revised) September 17, 2001 相似文献
996.
997.
Katarzyna Pietruska-Pałuba 《manuscripta mathematica》2004,115(3):389-399
Using the Dirichlet forms theory, we prove that when the locally compact measure metric space (X,,m) is the state space of a Markov process with transition density p(t,x,y) bounded from the above by where is a function satisfying certain integrability condition, then the following statement holds: when u L2(X) and then u is a constant function.This work is partially supported by a KBN grant no. 2-PO3A-028-22.Mathematics Subject Classification (2000): primary 60J35, secondary 46E35 相似文献
998.
The surface tension and the densities of the Cu-Ag-In alloys have been measured by means of the sessile drop method. The density of these alloys depends linearly on temperature in the case of all the investigated compositions. The surface tension shows a linear dependence on temperature except for the lowest temperatures. For most of the alloys, the surface tension at the lowest temperature is lower than that predicted by the straight line. The experimental values of the surface tension of the Cu-Ag-In alloys are compared with those computed from the model, and quite good agreement is observed. 相似文献
999.
Urszula A. Laudyn Katarzyna A. Rutkowska Robert T. Rutkowski Mirosław A. Karpierz Tomasz R. Woliński Jan Wójcik 《Central European Journal of Physics》2008,6(3):612-618
We have investigated the nonlinear propagation of light in photonic crystal fibers filled with nematic liquid crystals. We
analyzed a configuration with a periodic modulation of the refractive index corresponding to a matrix of waveguides. Matrices
of coupled waveguides allow observing a variety of new phenomena both for low power light beam propagation and with an existence
of nonlinear effects. The opportunity for the creation of solitary waves caused by the interplay between diffraction and nonlinear
effects in these kinds of fibers is investigated. At low power the propagating light beam spreads as it couples to more and
more waveguides. When the intensity is increased the light modifies the refractive index distribution, inducing a defect in
the periodic structure. The creation of such a defect can lead to a situation in which the light becomes self-localized and
its diffractive broadening is eliminated. Eventually, in the case of positive Kerr-type nonlinearity, a discrete soliton can
be created. In the case of negative nonlinearity the refractive index decreases with the optical power and can lead to bandgap
shifting. The incident beam, with a frequency initially within the bandgap, is then turned outside the bandgap resulting in
the changing of the propagation effect for the discrete diffraction effect. As a consequence the delocalization of the light
can be observed.
Presented at 9-th International Workshop on Nonlinear Optics Application, NOA 2007, May 17–20, 2007, Świnoujscie, Poland 相似文献
1000.
Michał Kowalski Katarzyna Kowalska Jarosław Wiszniowski Jolanta Turek-Szytow 《Chemical Papers》2018,72(11):2699-2706
The ability to measure and control the composition of activated sludge is an important issue, aiming at evaluating the effectiveness of changes occurring in the sludge, what determines its usefulness to treat wastewater. In this research, diffuse reflectance infrared Fourier transform (FTIR–DRIFT) technique was used, which relies on measuring the reflectance of the powdered substance’s surface layer and capturing spectra in range of infrared wave. First, spectra correlation table of the substances mostly occurring in wastewater was developed to assess the main components of the tested samples of activated sludge. The simplest compounds containing functional groups characteristic for particular chemical classes were chosen: peptides (peptone and albumin), fats (glycerin and fatty acids), carbohydrates (glucose and sucrose), nitrogen compounds (NaNO3 and NH4SO4), sulfur compounds (Na2SO4 and Na2S2O3), silicate, etc. The spectra of those substances were captured and characteristic absorption bands for respective bonds in the function groups were assigned. Second, samples of activated sludge from lab-scale membrane bioreactors (MBRs), which purifies petroleum wastewater, were taken. Samples were properly prepared (lyophilization and homogenization) and their spectra were captured. During spectra analysis, previously developed correlation table was used. In obtained spectra of activated sludge, absorption bonds characteristic for amides, peptides, carbohydrates, fats, and aliphatic was identified. The spectra profile of the sludge sample from MBR feed with petroleum wastewater was slightly different from the control MBR sample’s spectra. Intensity of bands in the area characteristic for aliphatic compounds and phenols was clearly higher. This study proves the usefulness of FT-IR technique to observe changes in the chemical composition of activated sludge. 相似文献