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511.
Erd?s-Ko-Rado sets in finite classical polar spaces are sets of generators that intersect pairwise non-trivially. We improve the known upper bound for Erd?s-Ko-Rado sets in \(H(2d+1, q^2)\) for \(d>2\) and \(d\) even from approximately \(q^{d^2+d}\) to \(q^{d^2+1}.\) 相似文献
512.
The paradox of destabilization of a conservative or non-conservative system by small dissipation,or Ziegler’s paradox(1952),has stimulated a growing interest in the sensitivity of reversible and Hamiltonian systems with respect to dissipative perturbations.Since the last decade it has been widely accepted that dissipation-induced instabilities are closely related to singularities arising on the stability boundary,associated with Whitney’s umbrella.The first explanation of Ziegler’s paradox was given(much earlier)by Oene Bottema in 1956.The aspects of the mechanics and geometry of dissipation-induced instabilities with an application to rotor dynamics are discussed. 相似文献
513.
Puterová Z Valentová J Bojková Z Kožíšek J Devínsky F 《Dalton transactions (Cambridge, England : 2003)》2011,40(7):1484-1490
The synthesis and solid-state structure of mononuclear copper(II) complexes [Cu(SAIB)(H(2)O)(2)] (1), [Cu(SBAIB)(H(2)O)(2)]·H(2)O (2) and [Cu(SGABA)(H(2)O)(2)] (3) are described. Schiff base ligands H(2)SAIB, H(2)SBAIB and H(2)SGABA chelate the copper(II) ion in an O,N,O tridentate fashion. The square-pyramidal geometry of the final complexes is completed by two water ligands. The formation of an unusual seven-membered ring in the set of copper(II) N-salicylidene-aminoacidates is reported. Compounds 1-3 were evaluated by the antiradical activity assay. 相似文献
514.
Brook MA Whinton M Gonzaga F Li N 《Chemical communications (Cambridge, England)》2011,47(31):8874-8876
Robust, transparent elastomeric hydrogels encoded with a bicontinuous structure result from the sequential photopolymerization of the aqueous hydroxyethyl methacrylate phase and crosslinking of the silicone phase of a silicone microemulsion stabilized with an acrylate-functional silicone-poly(ethylene glycol) surfactant. 相似文献
515.
Acta Applicandae Mathematicae - This paper summarizes the present state of integrability of Hamiltonian normal forms and it aims at characterizing non-integrable behaviour in higher-dimensional... 相似文献
516.
Yaqin Xu Lizanne Pharand Quan Wen Ferdinand Gonzaga Yingfu Li M. Monsur Ali Carlos D. M. Filipe Robert Pelton 《Colloid and polymer science》2011,289(5-6):659-666
Compared are two approaches for the biotinylation of poly(N-isopropylacrylamide-co-vinylacetic acid) microgels, 300-nm diameter, water swollen particles with a corona of carboxyl groups. The biotinylated microgels are a platform for bioactive water-based ink. Streptavidin binding was measured as a function of biotin density, and the results were interpreted with a new model that predicts the minimum local density of biotins required to capture a streptavidin. An amino-polyethylene glycol derivative of biotin gave higher biotin contents than a biotin hydrazide. However, the streptavidin content versus biotin content results for both biotin derivatives fell on the same master curve with maximum biotin coverage of 0.11?mg of bound streptavidin per milligram of biotinylated microgel. Exclusion experiments showed that streptavidin was too big to penetrate the cross-linked microgel structure; thus, the conjugated streptavidin was restricted to the microgel surface. The colloidal stability of the microgels was preserved, and the biotinylated products showed good hydrolytic stability. 相似文献
517.
Ferdinand Männle Terje Rosquist Tofteberg Morten Skaugen Huaitian Bu Thijs Peters Pascal D. C. Dietzel Monika Pilz 《Journal of nanoparticle research》2011,13(10):4691-4701
A route to a large variety of functionalized POSS compounds by a two-step procedure has been developed. Up-scaling to high
volume industrial applications is feasible. In the first step, an amino-functionalized silane such as 3-aminopropyltriethoxy
silane is converted to amino-functionalized POSS (amine-POSS) by a sol–gel process. In the second step, the amine groups of
amine-POSS are converted by state-of-the-art amine chemistry. A large number of reactants including carboxylic acids, esters,
anhydrides, isocyanates, carbonates, epoxides, and acrylates as well as reactants suitable for nucleophilic substitution can
be applied. Conversion of an amine-POSS with hexanoic acid leads to an amide-POSS. Amine chemistry can usually be performed
under mild conditions, which suppresses degradation and/or cross-linking reactions of the amine-POSS during the conversion.
MALDI-TOF mass spectroscopy and dynamic light scattering (particle size: 3–6 nm) have been applied to prove the conversion
of an amine-POSS to an amide-POSS. 1H-NMR and TGA-MS prove the presence of amide-POSS and its thermal stability. Gas barrier properties of nanocomposite coatings
based on functionalized POSS are characterized. 相似文献
518.
Georg Uray KarlheinzS. Niederreiter Ferdinand Belaj WalterM.F. Fabian 《Helvetica chimica acta》1999,82(9):1408-1417
Synthesis, absorption and fluorescence spectra, as well as quantum yields of a series of donor-acceptor-substituted carbostyrils (=quinolin-2(1H)-ones), are reported. Unprecedented strong absorption maxima (ε=10000 – 20000) close to the visible spectrum, large Stokes shifts up to 130 nm, and quantum yields up to 0.7 are obtained with derivatives containing donor substituents at C(6) and C(7), and either one Ph substituent at C(3) or one CF3 residue at C(4). For analytical applications in biochemistry and medicine, N(1)-functionalization, or amidoacylation at C(3) in the case of the CF3 derivatives, is possible without a concomitant hypsochromic shift of their absorption and emission maxima. Semiempirical molecular-orbital calculations (AM1 for structures, ZINDO for electronic transition energies) prove to be a suitable tool for the prediction of absorption properties of these compounds. The crystal-structure analysis of 6,7-dimethoxy-1-methyl-3-nitro-4-(trifluoromethyl)quinolin-2-(1H)-one ( 7 ) (C13H11F3N2O5, monoclinic, P21/c, a=12.372(2), b=12.154(2), c=10.119(2)Å, β=112.95(2)°) shows that the NO2 group, squeezed between the CF3 and the C=O group, is oriented almost perpendicularly (87.8(4)°) to the ring plane. The intramolecular F⋅⋅⋅N distance between the CF3 and the NO2 group is only 2.513(4)Å. 相似文献
519.
The structure of (+)-β-turmerone ((+)- 1a ), a constituent of the rhizomes of Curcuma longa Linn. , and Curcuma xanthorriza, is established as (1′R,6S)-2-methyl-6-(4′-methylenecyclohex-2′-en-1′-yl)hept-2-en-4-one by synthesis of its enantiomer (−)- 1a , and of the corresponding (1′S,6S)-diastereoisomer (+)- 1b as well. In a stereospecific seventeen-step procedure, the monoterpene diols 2a and 2b of well-established configuration are converted into the target compounds (−)- 1a and (+)- 1b , respectively. Moreover, (−)-bisacurol (−)- 3a (II), the enantiomer of another bisabolane sesquiterpene derived from Curcuma xanthorriza, is obtained as a single stereoisomer and shown to be (1′S,6R)-2-methyl-6-(4′-methylenecyclohex-2′-en-1′-yl)hept-2-en-4-ol, the relative configuration at the remaining OH-substituted chiral center C(4) still being unknown. 相似文献
520.
Gernot Boche Ferdinand Bosold Michael Marsch Klaus Harms 《Angewandte Chemie (International ed. in English)》1998,37(12):1684-1686
Different types of bonding are present in cyanocuprates 1 and 2 , whose crystal structures could be determined (the drawings below show the important structural characteristics). Accordingly, 1 is a lower order cyanocuprate of the type RCu(CN)Li, whereas 2 , which is of the type R2Cu(CN)Li2, does not exist as a “higher order” cyanocuprate with Cu–CN bonds, but rather as a cyano-Gilman cuprate. 相似文献