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991.
Alkyl substituted chromium Fischer carbene complexes react with 1,1-diphenylallene in the presence of rhodium(I) catalysts (10 mol%) to yield highly substituted dienyl indenone derivatives. In this process a catalytic chromium(0)-rhodium(I) exchange occurs, four new C-C bonds are created, and four-components (two allenes, the carbene ligand and one CO ligand) are joined in a chemo- and regioselective manner. 相似文献
992.
Rodríguez Flores J Berzas Nevado JJ Durán Merás I Rodríguez Gómez MJ 《Journal of separation science》2005,28(7):658-664
A capillary zone electrophoresis (CZE) method using a fused-silica capillary (60.2 cm x 75 microm ID) was investigated for the determination of triamterene (TRI), methotrexate (MTX), and creatinine (CREA) in human urine. The separation was performed using a hydrodynamic injection time of 7 s (0.5 psi), a voltage of 25 kV, a capillary temperature of 30 degrees C, and 40 mM phosphoric acid adjusted to pH 2.25 by addition of triethanolamine as separation electrolyte. Under these conditions, analysis takes about 15 min. A linear response over the 0.5-15.0 mg L(-1) concentration range was found for TRI and MTX, and 0.5-80.0 mg L(-1) for CREA. Dilution of the sample (water:urine, 1:1 for TRI and MTX, and 1:25 for CREA determination) was the only step necessary prior to analysis by electrophoresis. The developed method is easy, rapid, and sensitive and has been applied to determine triamterene,methotrexate, and creatinine in urine samples with satisfactory results. 相似文献
993.
Gyula Simig Gábor Doleschall Gyula Hornyák József Fetter Károly Lempert József Nyitrai Péter Huszthy Tibor Gizur Mária Kajtár-Peredy 《Tetrahedron》1985,41(2):479-484
Acylation of the N-substituted diethyl aminomalonates 3a–3d with diketene furnished the ring tautomers 6a–6d of the expected acetoacetyl derivatives 5. By treatment with iodine and sodium ethoxide compounds 6a–6d are smoothly converted into the β-lactam derivatives 2a–2d. Deethoxycarbonylation of the ethylene ketals 7a–7d of the latter furnishes mixtures of the corresponding diastereomeric monoesters 8 and10. The ethoxycarbonyl groups of the trans esters 8 are more reactive than those of the cis isomers 10. This permits, under appropriate conditions, selective alkaline hydrolysis and NaBH4 reduction of the trans esters 8 in the presence of the cis esters 10. Reduction of the cis ester 10c under more forceful conditions furnishes the trans hydroxymethyl derivative 11c. 相似文献
994.
A. Negrón-Mendoza G. Albarrán S. Castillo-Rojas 《Journal of Radioanalytical and Nuclear Chemistry》1992,160(2):461-466
The purpose of this work is to study the radiolytic behavior of aqueous solutions of14C-pyruvic acid (oxygen-free). Several parameters were varied such as radiation dose, pH, etc. Gas chromatography, mass spectrometry and high performance liquid chromatography were used extensively for the analysis of radiolytic products. The more abundant product was dimethyltartaric acid. Other products identified were acetic, lactic, succinic, malonic and tricarballylic acids, acetaldehyde, carbon dioxide, and hydrogen. The yields of these products were influenced by the irradiation dose, concentration of the target compound and pH of the solution. 相似文献
995.
Diffuse-reflectance Fourier transform-infrared spectroscopic (DRIFT) microanalysis (10 g samples) of a selected series of flavonoids was studied, comparing to transmission FT-IR spectroscopic analysis of the same samples at the mg level. DRIFT was shown to be a useful, sample-saving and reliable IR technique for the structural analysis and compound identification of the mainSilybum genus 3-OH-flavonolignans (silybin, isosilybin, silydianin, silychristin and isosilychristin) and the dihydroflavonol taxifolin. 相似文献
996.
Tamás Kalmár-Nagy 《Acta Appl Math》1991,23(3):301-302
Book Reviews
The laplace transformR. E. Bellman and R. S. Roth: World Scientific, Singapore, 1984 相似文献997.
Summary The paper deals with the behaviour of the so-called algorithms with respect to interval filling sequences A connection is established between the uniquely representable points and the continuity points of the algorithms; also strong continuity properties on monotonic algorithms are proved. Finally the results are applied to additive functions. The theorems extend some former results by the authors, by I. Kátai and by A. Járai.Dedicated to the memory of Alexander M. Ostrowski on the occasion of the 100th anniversary of his birth 相似文献
998.
Given two graphsH andG, letH(G) denote the number of subgraphs ofG isomorphic toH. We prove that ifH is a bipartite graph with a one-factor, then for every triangle-free graphG withn verticesH(G) H(T
2(n)), whereT
2(n) denotes the complete bipartite graph ofn vertices whose colour classes are as equal as possible. We also prove that ifK is a completet-partite graph ofm vertices,r > t, n max(m, r – 1), then there exists a complete (r – 1)-partite graphG* withn vertices such thatK(G) K(G*) holds for everyK
r
-free graphG withn vertices. In particular, in the class of allK
r
-free graphs withn vertices the complete balanced (r – 1)-partite graphT
r–1(n) has the largest number of subgraphs isomorphic toK
t
(t < r),C
4,K
2,3. These generalize some theorems of Turán, Erdös and Sauer.Dedicated to Paul Turán on his 80th Birthday 相似文献
999.
Gianpiero Cattaneo Giuseppe Nisticó 《International Journal of Theoretical Physics》1991,30(10):1293-1336
Some of the most frequent misconceptions about axiomatic quantum physics are discussed with the aim of clarifying their true significance, taking Piron's approach as conceptual framework. In particular, we deal with the following topics: the wrong identification of Piron's questions and Mackey's questions, and some curious alleged empirical consequences; the role of propositions as suitable equivalence classes of questions, their partial order structure, and the paradoxical consequences of the erroneous assignment to questions of some lattice properties involving propositions; the logical and the empirical purport of some negative theorems; the standard Hilbert space model of the theory and the consequent metaphysical disasters related to some identifications, which are peculiar of this model. A controversy between Foulis-Piron-Randall and Hadjisavvas-Thieffine-Mugur-Schächter is analyzed on the basis of the proposed Hilbert space model (in which Piron's questions are realized by Hilbertian effects, i.e., linear bounded operatorsF such that which clarify the different point of views. As an example, we treat the unsharp localization operators inL
2(). 相似文献
1000.