We characterize cardinalsκ such that 2λ = 2κ wheneverκ ≦λ < 2κ using ideals in small algebras of sets satisfying certain completeness and saturation conditions.
Research of this author was supported by an NSF Grant. 相似文献
The H2O2-FeCl3-bipy system in acetonitrile efficiently oxidises alkanes predominantly to alkyl hydroperoxides. Turnover numbers attain 400 after 1 h at 60 °C. It has been assumed that bipy facilitates proton abstraction from a H2O2 molecule coordinated to the iron ion (these reactions are stages in the catalytic cycle generating hydroxyl radicals from the hydrogen peroxide). Hydroxyl radicals then attack alkane molecules finally yielding the alkyl hydroperoxide. 相似文献
The synthesis, characterisation and polymerisation studies of a homologous series of α,ω-bis(pyrrolyl)alkanes are described. These α,ω-bis(pyrrolyl)alkanes were produced using Friedel-Crafts acylation followed by reduction of the carbonyl group using Red-Al®. Chemical polymerisation of the resultant dimers using FeCl3 produced poly(α,ω-bis(pyrrolyl)alkane) films, which were characterised by SEM, FTIR and tested for conductivity. 相似文献
In the presence of large amounts of [Me4N]Cl, the reaction of ortho-chloromercurated 2-[(eta6-phenyl)tricarbonylchromium]pyridine with mu-chloro cyclopalladated aromatic compounds yields a series of new heteroleptic heterodinuclear cis-(C--N)2Pd(II) complexes, which are valuable precursors of planar chiral cyclopalladated (eta6-arene)Cr(CO)3 complexes. 相似文献
Carbon disulfide reacts with the α-anions of carboxylate salts and esters to form intermediate salts, provides a new pathway to two classes of compounds: dithioesters and ketene mercaptals. The reaction produced the first carboxylated derivatives of dithioesters and ketene mercaptals. Examples of 2-carboxylated dithioesters and ketene mercaptals as well as their decarboxylated derivatives have been prepared and characterized. 相似文献
[structure: see text]. The synthesis and nonlinear optical characterization of two novel heteroaromatic-based chromophores is described. The new dyes present an A-pi-D-pi-A general framework, where A is a pi-deficient heteroaromatic ring (pyridine, quinoline, benzothiazole) and D a pi-excessive pyrrolyl moiety. Both systems exhibit large two-photon absorption (TPA) values in the femtoseconds regime (TPA cross section as high as 150 x 10(-50) cm(4) s photon(-1) molecule(-1) with 150 fs laser pulses). Their TPA-based optical limiting activity is also shown. 相似文献
A solid-phase extraction (SPE) method using unbonded silica (Si) and silica bonded with octadecyl (C18) or aminopropyl (NH2) groups was developed to separate into five fractions the highly complex mixture of low-molecular-mass degradation products formed from degradable polymers. Application of the method to polyethylene modified with starch and/or a pro-oxidant system, degraded for 30 weeks in water at 95°C, enabled the identification by GC-MS of over three times as many products as when the sample was prepared by liquid-liquid extraction. Over 60 degradation products were identified in each sample; mainly dicarboxylic acids, monocarboxylic acids and n-alkanes. In addition, several lactones, aldehydes and alcohols were detected. 相似文献
Cyclopeptide antibiotics from Aspergillus species. Structure of echinocandins C and D The echinocandins B, C and D are antifungal antibiotics produced by a strain of Aspergillus rugulosus. All three metabolites are closely related representing cyclic oligopeptides composed of six amino acids and a linolic acid residue in an amide linkage. The complete structure of echinocandin B ( 1 ) has recently been established by X-ray analysis. Structural assignments to the new minor metabolites C and D have now been made by hydrolytic and oxidative cleavage reactions, formation of N-acyl-α-aminoethers as well as by chemical correlations and extensive NMR. examinations. Echinocandin C ( 2 ), C52H81N7O15, contains 3-hydroxyhomotyrosine in the place of 3, 4-dihydroxyhomotyrosine present in 1 . Echinocandin D ( 3 ), C52H81N7O13, differs in two amino acids: 3, 4-dihyroxyhomotyrosine and 4, 5-dihydroxyornithine, unusual units of 1 being replaced by 3-hydroxyhomotyrosine and ornithine. 相似文献