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1.
Summary A separated filtered ring has a maximally complete immediate extension. This is an analogue of Krull Theorem from valuation
ring theory in the frame of filtered rings.
Riassunto Un anello separato filtrato ha una immediata estensione massimale completa. Questo risultato è un analogo del teorema di Krull della teoria degli anelli di valutazione nell’ambito degli anelli filtrati.相似文献
2.
Violetta Patroniak Wanda Radecka‐Paryzek Maciej Kubicki 《Acta Crystallographica. Section C, Structural Chemistry》2008,64(9):o511-o513
The structure of a trifluoromethanesulfonate salt of a nontypical triply protonated linear tetramine, C7H23N43+·3CF3SO3−, with a layered crystal structure is presented. One N atom remains unprotonated. The conformation of the cation is enforced by intra‐ and intermolecular hydrogen bonds. The crystal structure is built of ca 10 Å deep layers, within which cations and anions are hydrogen bonded. Each layer is only weakly bound to its neighbours. This study shows a rare example of an unsymmetrically protonated polyamine and the relation between the lack of protonation, intramolecular hydrogen bonding and the conformation of the cation. 相似文献
3.
Wanda Śliwa 《Transition Metal Chemistry》1996,21(6):583-592
Summary Endohedral and exohedral metallofullerenes, including metal-doped fullerenes, organometallic fullerenes and fullerene metal complexes, are described in the context of their syntheses and properties. 相似文献
4.
The paper is focused on the phenomena of various steady-state oscillations exhibited by the twin-well potential system. Regions of existence of different attractors in the system parameter domain are examined and a picture book of different steady states for fixed damping and forcing is presented: 20 different combinations of single or coexisting, small orbit or large orbit, periodic and chaotic attractors are displayed. Computer simulations are followed by an approximate analytical analysis: A study of various forms of instability of periodic solutions gives close form approximate criteria for occurrence of T-periodic small orbit and large orbit oscillations, and for cross-well chaos. 相似文献
5.
Wanda Sliwa 《Chemistry of Heterocyclic Compounds》1994,30(2):131-153
In the present review dealing with the reactivity of N-substituted azaaromatics their reduction as well as reactions proceeding on ring carbon atoms and on nitrogen atoms are described; also the reactivity of porphyrins and of complexes possessing these systems is reported. 相似文献
6.
In this communication we report a stereoselective total synthesis of N-Boc-dolaproine (Dap), an amino acid residue of the antineoplastic pentapeptide Dolastatin 10. Our strategy is based on a Baylis-Hillman reaction between N-Boc-prolinal and methyl acrylate, followed by a diastereoselective double bond hydrogenation and hydrolysis of the ester function. 相似文献
7.
Maria Bocheska Maria Hoffmann Urszula Lesiska Emilia Luks Wanda Radecka-Paryzek 《Tetrahedron》2005,61(52):12307-12313
New compounds: 5,11,17,23-tetra-tert-butyl-25,26,27,28-tetrakis(3-diisopropoxyphosphorylpropoxy)calix[4]arene (1) and 5,11,17,23-tetra-tert-butyl-25,26,27,28-tetrakis(3-methoxyethoxyphosphorylpropoxy)calix[4]arene (2) were synthesized and their ionophoric properties in ion-selective membrane electrodes were studied in comparison with already described by us 5,11,17,23-tetra-tert-butyl-25,26,27,28-tetrakis(3-diethoxyphophorylpropoxy)calix[4]arene (3). Complexes of 1 with calcium(II), lanthanum(III), europium(III) and gadolinium(III) nitrates were prepared in direct reaction of the ligand and appropriate metal salts. They were characterized by spectral data (IR, UV/Vis, luminescence, NMR, ESI-MS) and elemental analysis. The similarity in complexing behavior of the (dialkoxyphosphoryl)propoxy-calix[4]arenes toward calcium and some lanthanides was observed. 相似文献
8.
The selenenylation of racemic and optically active α-phosphoryl sulfoxides is a key step leading efficiently to α-phosphorylvinyl sulfoxides or α-phosphorylvinyl selenides depending on the reaction conditions. Oxidation of α-phosphorylvinyl selenides and subsequent thermolysis of selenoxides afford alkynylphosphonates. Studies of the stereochemical course of nucleophilic addition to α-phosphoryl sulfoxides show high facial stereoselectivity of the reaction, however, epimerisation at the α-carbon atom leads to mixtures of diastereomers. 相似文献
9.
Hidalgo ME Bascuñan L Quilhot W Fernández E Rubio C 《Photochemistry and photobiology》2005,81(6):1447-1449
Lichens synthesize and accumulate photoprotective compounds against possible damage induced by UV radiation in the photobiont. A biological model has been recently formulated that allows the use of lichens to evaluate changes at different UV radiation levels. The thermodynamics, photophysical and photochemical properties of lobaric acid were studied in acetonitrile, ethanol and Brij 35(3%) micelles at different pH values. Also the sun protector factor (SPF) was determined by in vitro methods. Lobaric acid was extracted from Stereoculon alpinum Laur. and characterized by means of standard procedures. Solutions were irradiated in oxygen and under nitrogen conditions with a UV medium pressure lamp. Lobaric acid absorbs at 287, 303 nm, and no fluorescence emission was observed. The maximum value of the molar extinction coefficient (5479.6 M(-1) cm(-1)) was obtained in Brij 35 at pH 12. Solubility is pH dependant and is highest in Brij 35 at pH 12 (4.45 x 10(-4) M). Photoconsumption quantum yields ranged between 10(-4) and 10(-5) in aerobic and anaerobic experimental conditions. Lobaric acid SPF was very low (0.5) compared with homosalate (4.0), (reference solar filter). Two pKa values, 5.05 (carboxylic acid group deprotonation) and 9.75 (phenolic OH deprotonation), were determined. 相似文献
10.