Asymmetric gold‐catalyzed hydrocarboxylations are reported that show broad substrate scope. The hydrophobic effect associated with in situ‐formed aqueous nanomicelles gives good to excellent ee’s of product lactones. In‐flask product isolation, along with the recycling of the catalyst and the reaction medium, are combined to arrive at an especially environmentally friendly process. 相似文献
The fourth-order nonlinear Boussinesq water wave equation, which explains the propagation of long waves in shallow water, is explored in this article. We used the Lie symmetry approach to analyze the Lie symmetries and vector fields. Then, by using similarity variables, we obtained the symmetry reductions and soliton wave solutions. In addition, the Kudryashov method and its modification are used to explore the bright and singular solitons while the Hirota bilinear method is effectively used to obtain a form of breather and lump wave solutions. The physical explanation of the extracted solutions was shown with the free choice of different parameters by depicting some 2-D, 3-D, and their corresponding contour plots.
A new approach was developed for modeling the effect of the third body on fretting. This was accomplished using the combined finite-discrete element method (FDEM) in which the third body is analyzed as discrete elements while the first bodies are modeled using finite elements. This approach provides a link between large scale models which treat the mass of wear debris as a single or small number of bodies and small scale models which only study a control volume. The FDEM was used to analyze the behavior of third body particles between flat sliding surfaces. When the third body mass is composed of unconnected particles, it behaves as a Newtonian fluid, but this behavior ceases when the particles are connected into platelets. The FDEM was also used to study the behavior of third body particles inside a Hertzian line contact. As the number of particles and platelet size increase the load carried by the worn slip zone grows larger in relationship to the unworn stick zone. 相似文献
A simple and convenient methodology for selective sulfonation of aromatic compounds using sulfuric acid under sonication is described. The present methodology shows a considerable enhancement in the reaction rate along with improved selectivity compared with the reactions performed under silent conditions. The effect of various parameters such as agitation speed, sulfuric acid concentration, and temperature on reaction system have been investigated and are explained on the basis of ultrasonically generated cavitational effects. 相似文献
Catalyst-free alcoholytic deprotection of borane-protected phosphorus compounds offers a smooth, efficient, and clean alternative to existing deprotection methods. In this paper we report our results on the general applicability of deprotecting phosphane- and phosphite-borane adducts by means of simple alcoholysis without the use of molecular sieves as a catalyst. Phosphane-boranes bearing at least one aromatic substituent are readily deprotected in high yields. Borane complexes of trialkylphosphanes or phosphites, however, cannot be deprotected in this way. The main merit of our method is its simplicity: apart from evaporation of the solvent, no further work-up or purification is needed. 相似文献
Based on the Linssi database and UniSampo/Shaman software, an automated analysis platform has been setup for the analysis
of large amounts of gamma-spectra from the primary coolant monitoring systems of a CANDU reactor. Thus, a database inventory
of gaseous and volatile fission products in the primary coolant of a CANDU reactor has been established. This database is
comprised of 15,000 spectra of radioisotope analysis records. Records from the database inventory were retrieved by a specifically
designed data-mining module and subjected to further analysis. Results from the analysis were subsequently used to identify
the reactor coolant half-life of 135Xe and 133Xe, as well as the correlations of 135Xe and 88Kr activities. 相似文献