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1.
In this paper we extend a result of Semrl stating that every 2-local automorphism of the full operator algebra on a separable infinite dimensional Hilbert space is an automorphism. In fact, besides separable Hilbert spaces, we obtain the same conclusion for the much larger class of Banach spaces with Schauder bases. The proof rests on an analogous statement concerning the 2-local automorphisms of matrix algebras for which we present a short proof. The need to get such a proof was formulated in Semrl's paper.
2.
In this paper we describe the general forms of all (nonlinear) continuous functionals on the sets of positive definite, positive semi-definite and Hermitian matrices which are multiplicative on the commuting elements. As a consequence, we obtain some new characterizations of the determinant on those classes of matrices.
3.
For everyt>1 and positiven we construct explicit examples of graphsG with |V (G)|=n, |E(G)|c
t
·n
2–1/t
which do not contain a complete bipartite graghK
t,t
!+1 This establishes the exact order of magnitude of the Turán numbers ex (n, K
t,s
) for any fixedt and allst!+1, improving over the previous probabilistic lower bounds for such pairs (t, s). The construction relies on elementary facts from commutative algebra.Research supported in part by NSF Grants DMS-8707320 and DMS-9102866.Research supported in part by Hungarian National Foundation for Scientific Research Grant 相似文献
4.
Eles J Kalaus G Greiner I Kajtár-Peredy M Szabó P Keserû GM Szabó L Szántay C 《The Journal of organic chemistry》2002,67(21):7255-7260
The first syntheses of the alkaloids (-)-mehranine (3), (+)-voaphylline/conoflorine (4), (+)-N(a)-methylvoaphylline/hecubine (5), and (-)-lochnericine (2) were achieved by stereoselective epoxidation starting from (-)-tabersonine (1), through intermediates with the aspidospermane and quebrachamine skeleton. 相似文献
5.
6.
Aacute;gnes Buvári-Barcza Antal Csámpai Lajos Barcza 《Journal of inclusion phenomena and macrocyclic chemistry》2002,42(3-4):209-212
Two guests reacting with cyclodextrins (CDs) may form ternary complexes, in addition to the common competition of 1:1 complexes. One of the guests can really be included into the cavity of the CD, while the second guest molecule is either inserted close to the first one or attached to the outer surface of the supramolecule by H-bonding. There is a further possibility when the included guest bears a substituent outside the cavity and the second guest can interact with it. The properties of the ternary species formed are highly influenced by the solely (or primarily) included guest. The changes are attributed to the altered properties of the hydrophilic domain of the CD. The phenomena can be proved by NMR data obtained for some binary systems of -CD inclusion complexes and acetic acid and by the stability constants of the ternary complexes formed. Allosteric effects as well as coenzyme/apoenzyme/substrate interactions could be well modelled by these types of CD complexes. 相似文献
7.
New tetracyclic derivatives (3a,, 5, 8) similar to protoberberines, but containing a lactam structural element and other hetero atoms besides the bridge-head nitrogen in rings B and C, were prepared by cycloaddition of 6,7-dimethoxy-2H-1,3-benzothiazine (1a) with -substituted aromatic carboxylic acid derivatives (2a,, 4) and from 4- methyl-6,7-dimethoxy-2-1,3-benzothiazine (1b) with 3.5-dinitrobenzoyl chloride. 相似文献
8.
Gergő Tóth Réka Mohácsi Ákos Rácz Aura Rusu Péter Horváth Lajos Szente Szabolcs Béni Béla Noszál 《Journal of inclusion phenomena and macrocyclic chemistry》2013,77(1-4):291-300
The enantiomer-specific characterization of ofloxacin–cyclodextrin complexes was carried out by a set of complementary analytical techniques. The apparent stability constants of the ofloxacin enantiomers with 20 different cyclodextrins at two different pH values were determined to achieve good resolution capillary electrophoresis enantioseparation either to establish enantioselective drug analysis assay, or to interpret and design improved host–guest interactions at the molecular level. The cyclodextrins studied differed in the nature of substituents, degree of substitution (DS), charge and purity, allowing a systematic test of these properties on the complexation. The seven-membered beta-cyclodextrin and its derivatives were found to be the most suitable hosts. Highest stability and best enantioseparation were observed for the carboxymethylated-beta-cyclodextrin (DS ~ 3.5). The effect of substitution pattern (SP) was investigated by molecular modeling, verifying that SP greatly affects the complex stability. Induced circular dichroism was observed and found especially significant on carboxymethylated-beta-cyclodextrin. The complex stoichiometry and the geometry of the inclusion complexes were determined by 1H NMR spectroscopy, including 2D ROESY techniques. Irrespective of the kind of cyclodextrin, the complexation ratio was found to be 1:1. The alfa-cyclodextrin cavity can accommodate the oxazine ring only, whereas the whole tricyclic moiety can enter the beta- and gamma-cyclodextrin cavities. These equilibrium and structural information offer molecular basis for improved drug formulation. 相似文献
9.
Viktor Pajer Ferenc Rárosi Lajos Kolozsvári Béla Hopp Antal Nógrádi 《Photochemistry and photobiology》2020,96(4):826-833
The purpose of the present study was to determine the age dependence of the ultraviolet (UV) absorption of the different parts of the human crystalline lens. Cryostat sections of human cadaveric lenses (60 μm) were cut. The UV absorbance of nine samples, derived from different parts of the lens, was determined using a Shimadzu scanning spectrophotometer. The absorbance of the anterior and posterior lens capsules was measured separately. The absorption coefficients were calculated from the measured absorbance and values taken at 280 as well as at 360 nm were compared statistically. ANCOVA analysis of the values taken at 280 and at 360 nm wavelengths shows that correlation between the absorption coefficients and age can be found only in the case of the posterior layers. These results suggest a differential age-dependent increase of the UV absorption of the posterior layers compared to the anterior ones and can be related to the differential protein expression in the anterior and posterior parts. Posterior crystalline lens capsules have higher absorption coefficients than the anterior ones regardless of age. 相似文献
10.
Tibor Kelen Tibor Kelen Lajos Balogh Istvan Majoros Gyorgy Deak 《Macromolecular Symposia》1993,67(1):325-338
The possibilities of increasing the livingness in cationic isobutylene polymerizations has been investigated. It has been assumed that the living chain-end is polarized but non-dissociated and relatively stable, therefore, i) shifting of the dissociation equilibrium by adding salts with common or non-common anion in excess, and ii) increasing of the stability of the chain-end by complexing it with electrondonors, may increase the livingness of the system. Indeed, the addition of n-Bu4NCl or n-Bu4NI to systems with BCl3 or TiCl4 coinitiators, as well as the addition of dimethyl sulphoxide as electrondonor in a broad concentration range, improved the living character. The possibility of complexation of the chain-end by the monomer has also been supported 相似文献