An efficient cross-coupling reaction of aryl halides and nitromethane was developed with the use of parallel microscale experimentation. The arylnitromethane products are precursors for numerous useful synthetic products. An efficient method for their direct conversion to the corresponding oximes and aldehydes in a one-pot operation has been discovered. The process exploits inexpensive nitromethane as a carbonyl equivalent, providing a mild and convenient formylation method that is compatible with many functional groups. 相似文献
A microstructured composite material made of collagen hydrogel (matrix) and silk fibroin microfibers (randomly oriented reinforcing fibers) is investigated in order to conjugate the mechanical resistance of fibroin with the suitable biological performance of collagen to design new scaffolds for vascular tissue engineering. Results show that fibroin microfibers and collagen fibrils have suitable interfacial adhesion, and the scaffold exhibits improved mechanical properties if compared with a pure collagen hydrogel. Furthermore, the overall biological performance is improved.
[reaction: see text] A de novo structural class of chiral amino alcohol catalysts has been identified through a synergistic effort combining novel architectures from [4 + 3] cycloadditions and quantum mechanical interaction field predictions that closely match subsequent experimental measurements. 相似文献
Calcium carbonate is without doubt the most widely used mineral filler. There are good reasons for this popularity, namely the combination of numerous deposits of that material and its suitability for a wide range of applications. In this paper results of rheological analysis based on melt index values of polypropylene composites (PP composites), prepared with different grades of calcium carbonate are reported. The study showed that the experimental design can be used as an important tool to evaluate the effect of CaCO3 grade and its content in polypropylene (PP). It was observed that the addition of calcium carbonate of different particle sizes and contents provoked a significant change in the rheological behavior of the composites analysed. 相似文献
Let P be a class of finite families of finite sets that satisfy a property P. We call ΩP the class of intersection graphs of families in P and CliqueP the class of graphs whose family of cliques is in P. We prove that a graph G is in ΩP if and only if there is a family of complete sets of G which covers all edges of G and whose dual family is in P. This result generalizes that of Gavril for circular-arc graphs and conduces those of Fulkerson-Gross, Gavril and Monma-Wei
for interval graphs, chordal graphs, UV, DV and RDV graphs. Moreover, it leads to the characterization of Helly-graphs and dually chordal graphs as classes of intersection graphs.
We prove that if P is closed under reductions, then CliqueP=Ω(P*∩H) (P*= Class of dual families of families in P). We find sufficient conditions for the Clique Operator, K, to map ΩP into ΩP*. These results generalize several known results for particular classes of intersection graphs. Furthermore, they lead to
the Roberts-Spencer characterization for the image of K and the Bandelt-Prisner result on K-fixed classes.
Received: August 18, 1997 Final version received: March 30, 1999 相似文献
Coffee seeds are a source for obtaining oil which is used in the candy, soluble coffee, and cosmetics industries. The main purpose of this study was the investigation of the lipid profile and thermal behavior of the roasted and in nature coffee oil of Arabica and Robusta species, using thermogravimetry, differential thermal analysis, derivative thermogravimetry, differential scanning calorimetry (DSC), and modulated DSC. Details concerning the thermal decomposition as well as data of the kinetic parameters have been described here. The kinetic studies were evaluated from several heating rates with a sample mass of 10 mg in open crucible under nitrogen atmospheres. The obtained data were evaluated with the isoconversional kinetic method, where the values of activation energy (Ea/kJ mol?1) were evaluated in function of the conversion degree (α). In addition, this oil was evaluated by modulated DSC from 25 to ?60 °C, where the transition phase behavior was verified. 相似文献
The interaction between a 1,2,4-triazine N-oxide derivative, that holds potential antitumor activity under hypoxic conditions, and diverse polyamidoamine (PAMAM) dendrimers were investigated with the purpose of select the most appropriate macromolecule to act as potential molecular carrier of this active compound. The results shows that dendrimers with amine terminal groups (PAMAM-AT G = 3) and dendrimers with carboxylate terminal groups (PAMAM-CT G2.5 and G4.5) produces triazine derivative hydrolysis, even in buffered medium, and are not suitable as carriers. In contrast, dendrimers with neutral end groups (PAMAM-OHT) shows stable association with the active compound, making this dendrimer a possible medium for triazine carriage. 相似文献