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121.
Torsten Ström 《BIT Numerical Mathematics》1967,7(4):314-321
Two procedures are given for obtaining strict error bounds in Romberg quadrature. Sufficient conditions for their validity are derived. The simpler procedure only uses quantities already calculated in the Romberg scheme. The general procedure is based on a majorant concept. 相似文献
122.
Metabolites of bird's nest fungi. Part 18. new oxygenated cadinane derivatives from cyathus striatus
The bird's nest fungusCyathus striatus Willd. ex Pers. when grown in aerated liquid culture produces three sesquiterpenes which are identified as schizandronol 1, 7α - hydroxy - schizandronol3 and schizandronol - 8,13β - oxide 5. The identification is based on spectral investigation of the compounds and their derivatives. This is the first reported isolation of 1 from a fungal source. Compounds 3 and 5 have not been reported previously. 相似文献
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125.
Laursen JB Nielsen J Haack T Pusuluri S David S Balakrishna R Zeng Y Ma Z Doyle TB Mitscher LA 《Combinatorial chemistry & high throughput screening》2006,9(9):663-681
A synthetic reexamination of a series of ketodihydronicotinic acid class antibacterial agents was undertaken in an attempt to improve their therapeutic potential. A convenient new synthesis was developed involving hetero Diels-Alder chemistry producing 74 new analogs in a multiple parallel synthetic manner and these were examined in vitro for their antimicrobial potential. Several compounds demonstrated significant broad-spectrum activity against clinically derived bacterial strains but previously known 1-(2,4-difluorophenyl)-6-(4-dimethylaminophenyl)-4-pyridone-3-carboxylic acid (7) remained the most potent compound in this class. Cross-resistance with ciprofloxacin supported a commonality of mode of action. Permiabilization of Escherichia coli cells by polymyxin B significantly enhanced potency with these agents suggesting that poor cellular uptake was primarily responsible for the disappointing activity against bacteria that some of the analogs exhibited. 相似文献
126.
127.
A sol-gel based surface treatment for preparation of water repellent antistatic textiles 总被引:1,自引:0,他引:1
In this paper a surface treatment is described for preparation of hydrophobic sol-gel coatings that simultaneously offer antistatic properties for an appropriate finishing of textiles and refinement of polymer foils. Sol-gel based formulations are modified with both hydrophilic and hydrophobic components simultaneously. Hydrophobic components are, e.g., alkoxysilanes modified with alkyl chains while the hydrophilic ones are amino-functionalized alkoxysilanes. The basic idea is that due to an enrichment of hydrophobic groups at the solid/air interface the surface of the as prepared coatings will be hydrophobic while the deeper region will be more hydrophilic. Textiles finished with these coatings exhibit sufficient water repellence and simultaneously absorb sufficient amounts of humidity in the deeper areas of the coating guaranteeing antistatic properties. This concept offers interesting approaches for the preparation of multifunctional surface coatings not only focussing on combining water repellence with antistatic properties for textile materials. 相似文献
128.
The secondary ion mass spectrum of silicon sputtered by high energy C60+ ions in sputter equilibrium is found to be dominated by Si clusters and we report the relative yields of Sim+ (1 ≤ m ≤ 15) and various SimCn+ clusters (1 ≤ m ≤ 11 for n = 1; 1 ≤ m ≤ 6 for n = 2; 1 ≤ m ≤ 4 for n = 3). The yields of Sim+ clusters up to Si7+ are significant (between 0.1 and 0.6 of the Si+ yield) with even numbered clusters Si4+ and Si6+ having the highest probability of formation. The abundances of cluster ions between Si8+ and Si11+ are still significant (>1% relative to Si+) but drop by a factor of ∼100 between Si11+ and Si13+. The probability of formation of clusters Si13+-Si15+ is approximately constant at ∼5 × 10−4 relative to Si+ and rising a little for Si15+, but clusters beyond Si15 are not detected (Sim≥16+/Si+ < 1 × 10−4). The probability of formation of Sim+ and SimCn+ clusters depends only very weakly on the C60+ primary ion energy between 13.5 keV and 37.5 keV. The behaviour of Sim+ and SimCn+ cluster ions was also investigated for impacts onto a fresh Si surface to study the effects that saturation of the surface with C60+ in reaching sputter equilibrium may have had on the measured abundances. By comparison, there are very minor amounts of pure Sim+ clusters produced during C60+ sputtering of silica (SiO2) and various silicate minerals. The abundances for clusters heavier than Si2+ are very small compared to the case where Si is the target.The data reported here suggest that Sim+ and SimCn+ cluster abundances may be consistent in a qualitative way with theoretical modelling by others which predicts each carbon atom to bind with 3-4 Si atoms in the sample. This experimental data may now be used to improve theoretical modelling. 相似文献
129.
The boxicity of a graph is the smallest integer such that is the intersection of interval graphs, or equivalently, that is the intersection graph of axis-aligned boxes in . These intersection representations can be interpreted as covering representations of the complement of with co-interval graphs, that is, complements of interval graphs. We follow the recent framework of global, local and folded covering numbers (Knauer and Ueckerdt, 2016) to define two new parameters: the local boxicity and the union boxicity of . The union boxicity of is the smallest such that can be covered with
vertex–disjoint unions of co-interval graphs, while the local boxicity of is the smallest such that can be covered with co-interval graphs, at most at every vertex.We show that for every graph we have and that each of these inequalities can be arbitrarily far apart. Moreover, we show that local and union boxicity are also characterized by intersection representations of appropriate axis-aligned boxes in . We demonstrate with a few striking examples, that in a sense, the local boxicity is a better indication for the complexity of a graph, than the classical boxicity. 相似文献
130.