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排序方式: 共有163条查询结果,搜索用时 15 毫秒
31.
An eco-friendly synthesis of highly functionalized epoxides and their incorporation into an organocatalytic multicomponent approach are reported. For this, a modified class of diarylprolinol silyl ethers was designed to enable high catalytic activity in an environmentally benign solvent system. The one-pot procedure showed great efficiency in promoting stereoselective multicomponent transformations in a tandem, 'green' fashion. Because of its non-residual, efficient and selective character, this synthetic design shows promise for large-scale applications in both diversity and target-oriented syntheses. 相似文献
32.
In this paper we will be concerned with questions of existence and multiplicity of radial nonnegative solutions of the quasilinear elliptic equation We will use variational methods in order to prove the existence of multiple solutions in case f is a sign-changing nonlinearity. 相似文献
33.
Highly Stereoselective Synthesis of Natural‐Product‐Like Hybrids by an Organocatalytic/Multicomponent Reaction Sequence 下载免费PDF全文
M. Sc. Radell Echemendía M. Sc. Alexander F. de La Torre M. Sc. Julia L. Monteiro M. Sc. Michel Pila Prof. Dr. Arlene G. Corrêa Prof. Dr. Bernhard Westermann Prof. Dr. Daniel G. Rivera Prof. Dr. Márcio W. Paixão 《Angewandte Chemie (International ed. in English)》2015,54(26):7621-7625
In an endeavor to provide an efficient route to natural product hybrids, described herein is an efficient, highly stereoselective, one‐pot process comprising an organocatalytic conjugate addition of 1,3‐dicarbonyls to α,β‐unsaturated aldehydes followed by an intramolecular isocyanide‐based multicomponent reaction. This approach enables the rapid assembly of complex natural product hybrids including up to four different molecular fragments, such as hydroquinolinone, chromene, piperidine, peptide, lipid, and glycoside moieties. The strategy combines the stereocontrol of organocatalysis with the diversity‐generating character of multicomponent reactions, thus leading to structurally unique peptidomimetics integrating heterocyclic, lipidic, and sugar moieties. 相似文献
34.
35.
G. M. Corrêa L. P. Bellé L. Bajerski S. H. M. Borgmann S. G. Cardoso 《Chromatographia》2007,65(9-10):591-594
A reversed-phase high-performance liquid chromatographic method has been developed and validated for quantitative determination of deflazacort in tablets and in compounded capsules. Isocratic chromatography was performed on a C18 column with acetonitrile–water 80:20 (v/v) as mobile phase at a flow rate of 1.0 mL min?1. UV detection was at 240 nm. The linearity of the method was good (r > 0.999), as also were intra-day and inter-day precision (RSD <2%) and accuracy (recovery >98%). The method was also validated for specificity and robustness. The results showed the proposed method is suitable for its intended use. 相似文献
36.
Interfacial properties and thermal stability of modified poly(m‐phenylene isophthalamide) thin films
Sandra Cruz dos Santos Lara Fernandes Loguercio Diogo Silva Corrêa Michael Ramos Nunes Marcos Antônio Villetti Irene Teresinha Santos Garcia 《Surface and interface analysis : SIA》2013,45(4):837-843
Poly(m‐phenylene isophthalamide) (PMIA) is a resistant to high temperatures and chemically stable engineering material. The application as coatings and membranes, however, is limited by its poor interaction with other materials. In this report, we describe the molecular modification of PMIA through reaction with dimsyl sodium and 2‐iodine‐1‐ethanol. The substitution of 58% of amide hydrogen by ethanol (etOH) groups produces a material (MPMIA) able to develop regularly structured films on silicon substrate. The morphology of the films is dependent on the ionic strength of the precursory solution. MPMIA starts a degradation process by losing the etOH group. MPMIA has a better affinity with poly(p‐cresolformaldehyde) than with a pristine one, increasing the range of composition in which thermal stability and miscibility are observed. Thin films of these blends have different morphologies that vary from nanometric porous to two‐phase microstructured grains, according to the composition. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
37.
L. Corrêa G.A. B. Lima M.A. C. Candezano M.P. S. Braun C.M. Oishi H.A. Navarro V.G. Ferreira 《国际流体数值方法杂志》2013,72(12):1263-1285
A bounded upwinding scheme for numerical solution of hyperbolic conservation laws and Navier–Stokes equations is presented. The scheme is based on convection boundedness criterion and total variation diminishing stability criteria and developed by employing continuously differentiable functions. The accuracy of the scheme is verified by assessing the error and observed convergence rate on 1‐D benchmark test cases. A comparative study between the new scheme and conventional total variation diminishing/convection boundedness criterion‐based upwind schemes to solve standard nonlinear hyperbolic conservation laws is also accomplished. The scheme is then examined in the simulation of Newtonian and non‐Newtonian fluid flows of increasing complexity; a satisfactory agreement has been observed in terms of the overall behavior. Finally, the scheme is used to study the hydrodynamics of a gas‐solid flow in a bubbling fluidized bed. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
38.
Luiz Carlos Machado Marcos Tadeu D’Orlando de Azeredo Hamilton Perez Soares Corrêa Jivaldo do Rosário Matos Ítalo Odone Mazali 《Journal of Thermal Analysis and Calorimetry》2012,107(1):305-311
This study investigates two lanthanide compounds (La3+ and Sm3+) obtained in water/ethyl alcohol solutions employing the anionic surfactant diphenyl-4-amine sulfonate (DAS) as ligand. Both
sulfonates were characterized through IR, TG/DTG (O2 and N2). The thermal treatment of both compounds at 1273 K under air leaves residues containing variable percentages of lanthanide
oxysulfide/oxysulfate phases shown by synchrotron high-resolution XRD pattern including the Rietveld analysis. The phase distributions
found in the residues evidence the differences in the relative stability of the precursors. 相似文献
39.
On a ‐Kirchhoff equation with critical exponent and an additional nonlocal term via truncation argument 下载免费PDF全文
Francisco Julio S. A. Corrêa Augusto César dos Reis Costa 《Mathematische Nachrichten》2015,288(11-12):1226-1240
We study existence and multiplicity of solutions of the following nonlocal ‐Kirchhoff equation with critical exponent, via truncation argument on the Sobolev space with variable exponent, where Ω is a bounded smooth domain of , , M, f are continuous functions, , and are real parameter. 相似文献
40.
Cátia Crispilho Corrêa Lucimara Aparecida Forato Luiz Alberto Colnago 《Analytical and bioanalytical chemistry》2009,393(4):1357-1360
High intake of saturated fat from meats has been associated with cardiovascular disease, cancer, diabetes, and others diseases.
In this paper, we are introducing a simple, high-throughput, and non-destructive low-resolution nuclear magnetic resonance
method that has the potential to analyze the intramuscular fat content (IMF) in more than 1,000 beef portions per hour. The
results can be used in nutritional fact labels, replacing the currently used average value. The method is based on longitudinal
(T
1) and transverse (T
2) relaxation time information obtained by a continuous wave-free precession (CWFP) sequence. CWFP yields a higher correlation
coefficient (r = 0.9) than the conventional Carr-Purcell-Meiboom-Gill (CPMG) method (r = −0.25) for IMF in beef and is just as fast and a simpler pulse sequence than CPMG. The method can also be applied to other
meat products. 相似文献