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21.
Steven E. Patterson Lubomir Janda Lucjan Strekowski 《Journal of heterocyclic chemistry》1992,29(4):703-706
A one-pot preparation of carboximidamides (amidines) 11–14 involves treatment of amides 2–5 with phosphorus pentachloride followed by the treatment of the resultant crude imidoyl chlorides 7–10 with ammonia. Amidines 11–14 are cyclized to quinazolines 20–26 in lithium alkylamide-or dialkylamide-mediated reactions. 相似文献
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Nonoscillation of Elliptic Integrals Related to Cubic Polynomials with Symmetry of Order Three 总被引:3,自引:0,他引:3
We study zeros of elliptic integrals I(h)=HhR(x,y)dxdy, whereH(x,y) is a real cubic polynomial with a symmetry of order three,and R(x,y) is a real polynomial of degree at most n. It turnsout that the vector space An formed by such integrals is a Chebishevsystem: the number of zeros of each elliptic integral I(h)Anis less than the dimension of the vector space An. 1991 MathematicsSubject Classification 34C10. 相似文献
24.
Peter Lubomir Polak Ana Paula Mousinho Luis da Silva Zambom 《Applied Surface Science》2007,254(1):173-176
In this work the surfaces of polymeric membranes based on Nafion (proton conducting material), used in proton exchange membranes fuel cells (PEMFC) had been modified by plasma deposition of perfluored polymers, in order to improve its functioning in systems of energy generation (fuel cells). The deposition increases the chemical resistance of the proton ionic polymers without losing the electrical properties. The processing of the membranes also reduces the permeability of the membranes to the alcohols (methanol and ethanol), thus preventing poisoning of the fuel cell. The processing of the membranes of Nafion was carried through in a system of plasma deposition using a mixture of CF4 and H2 gases. The plasma processing was made mainly to increase the chemical resistance and result in hydrophobic surfaces. The Fourier transformed infrared (FTIR) technique supplies a spectrum with information about the CFn bond formation. Through the Rutherford back scattering (RBS) technique it was possible to verify the deposition rate of the polymeric layer. The plasma process with composition of 60% of CF4 and 40% of H2 presented the best deposition rate. By the spectrum analysis for the optimized configuration, it was possible to verify that the film deposition occurred with a thickness of 90 nm, and fluorine concentration was nearly 30%. Voltammetry made possible to verify that the fluorination increases the membranes chemical resistance, improving the stability of Nafion, becoming an attractive process for construction of fuel cells. 相似文献
25.
Lubomir Janda Johnny Nguyen Steven E. Patterson Lucjan Strekowski 《Journal of heterocyclic chemistry》1992,29(7):1753-1756
A tert-butoxide base-mediated cyclization of fluoro- and trifluoromethyl-substituted Schiff bases 12-19 produces 4-tert-butoxyquinolines 23-30 which are hydrolyzed to quinolin-4-ols 31-38 . 相似文献
26.
Lubomir Marko 《PAMM》2006,6(1):645-646
We deal with the local and global existence of solutions and solutions multiplicity for nonlinear problem u – λLu + N (u) = 0 in a real Hilbert space H, with linear operator L and nonlinear operator N, defined on a Hilbert space H, in dependence on a parameter λ ∈ R . (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
27.
Melnychuk Khrystyna Marchuk Oleg Daszkiewicz Marek Gulay Lubomir 《Structural chemistry》2020,31(5):1945-1957
Structural Chemistry - The crystal structures of quaternary R3Fe0.5SnS7, R3Co0.5SnS7 and R3Ni0.5SnS7 (R = Y, La, Ce, Pr, Nd, Sm, Gd, Tb, Dy and Ho) compounds of La3Mn0.5SiS7 structure type (space... 相似文献
28.
Claudia Aparicio Jan Filip Karolina Machalova-Siskova Miroslav Mashlan Lubomir Spanhel 《Journal of Sol-Gel Science and Technology》2014,72(3):655-662
Hot ethanolic mixtures of hydrated Zn(II)- and Fe(II)-carboxylates (acetate and lactate) react to form yellow-orange colored Fe(III)xZnyOzOHw heteroclusters showing pronounced electronic resonances in the optical UV absorption spectra. On the addition of LiOH to these polymolecular sols, stable nanoparticulate Fe(III)–ZnO colloids are formed. During colloidal growth, 2–4 nm sized weakly crystallized Wurtzite nanoparticles are exclusively formed even in the presence of high Fe content up to 20 at.%. The presence of Fe(III) in the ZnO condensation process retards the nanoparticle growth and blocks the thermal crystallization and size enhancement up to 250 °C. The produced 0.5 M Fe(III)–ZnO sols are useful for film formation processes. From atomic force microscopy-AFM, scanning electron microscopy-SEM and X-ray diffraction-XRD studies, we note important differences in shape and morphology of the thermally annealed Fe(III)–ZnO layers depending on the iron carboxylate employed. Surprisingly, Fe(II)-lactate derived coatings are carrying vertically oriented cone-shaped aggregates composed of 60–120 nm long primary nanorods. Contrary, Fe(II)-acetate based synthesis gave sand-dune like film morphologies containing spherical 12 nm sized nanocrystallites. All film samples possess mesoporosity with pore size ranging between 5 and 20 nm. 相似文献
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Georgi Bekjarov Veselin Kmetov Lubomir Futekov 《Fresenius' Journal of Analytical Chemistry》1989,335(8):971-974
Summary Aqueous solutions of high salt concentration are subjected to direct flame atomic absorption analysis. Blockage of nebulizer and burner is eliminated by employing the dosage scheme washing solution — sample — washing solution effected by means of a specially designed device. The microtrace content of bismuth, zinc and copper in sodium chloride and of copper, lead and iron in ammonium fluoride is determined by the standard addition method. Matrix effects are reduced in the analysis of sodium chloride by the addition of ethanol and in the analysis of ammonium fluoride by pre-heating of sample and washing solution. In order to improve the signal-to-noise ratio, ensemble summation is applied.The following trace element concentrations are determined: 0.5 mg/kg of Cu; 5 mg/kg of Bi and 0.25 mg/kg of Zn in sodium chloride and 0.47 mg/kg of Cu; 0.1 mg/kg of Pb and 3.7 mg/kg of Fe in ammonium fluoride.
Bestimmung von Spurenelementen in hochkonzentrierten Salzlösungen (NaCl, NH4F) mittels Flammen-Atom-Absorptions-Analyse相似文献