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排序方式: 共有401条查询结果,搜索用时 62 毫秒
381.
M.L. Santos M.P.C. Rocha P.L.O. Braga 《Journal of Mathematical Analysis and Applications》2007,325(2):1077-1094
In this paper we prove the exponential decay in the case n>2, as time goes to infinity, of regular solutions for a nonlinear coupled system of wave equations with memory and weak damping
382.
Alberto EE Rossato LL Alves SH Alves D Braga AL 《Organic & biomolecular chemistry》2011,9(4):1001-1003
The synthesis and antimicrobial profile of imidazolium ionic liquids containing selenium are described herein. Minimum inhibitory concentration revealed that these compounds are especially active against algae, and their activity is modulated by substituents attached to the selenium moiety as well as by the counterion. 相似文献
383.
In recent years, there has been an increasing application of chiral selenium compounds as ligands in metal-catalyzed enantioselective transformations. One of the most important challenges in this field is the development of new chiral complexes (catalyst) generated from the reaction between a metal and appropriate chiral selenium-containing compounds (ligand). The vast majority of these ligands are easily synthesized in a few high-yielding synthetic steps, starting from readily available chiral amino alcohols. In this context, the advantages of using these compounds will be discussed, mainly with regard to their easy accessibility, modular nature and the formation of strong bonds with soft or, more rarely, hard metals. Important selective contributions within the field of chiral selenium complexes are examined, according to their applications. As final remarks, future developments and perspectives of the field are discussed. 相似文献
384.
Alessandrini L Braga D Jaafari A Miozzo L Mora S Silvestri L Tavazzi S Yassar A 《The journal of physical chemistry. A》2011,115(3):225-231
The polarized UV-visible absorption spectra of dibenzo[d,d']thieno[3,2-b;4,5-b']dithiophene single crystals are reported and interpreted to definitively attribute the observed bands and their polarizations. The results provide information on the intermolecular interactions and on the aggregation in the condensed phase, which can be of either herringbone- or H-type, depending on the electronic transition taken into considerations, with consequences on the order and polarization of the absorption bands. A relatively easy method is also discussed to obtain information on the structural/morphological properties of different types of samples, including thin films, which have been recently proposed for high-performance organic film-effect transistors for their high ionization potential and photostability. 相似文献
385.
Braga D d'Agostino S D'Amen E Grepioni F 《Chemical communications (Cambridge, England)》2011,47(18):5154-5156
A new silver(I) complex with 1-phenyl-3-(quinolin-5-yl)urea has been prepared, acting as a supramolecular supergelator in the presence of polar solvents. In open vials temperature dependent, reversible gel-to-xerogel transition is observed, while in sealed vials direct crystallization of four polymorphs of the same gelling compound is achieved, depending on the gelling solvent. 相似文献
386.
Thiago O. Carvalho Ana E. B. Matias Lilian R. Braga Sheila M. Evangelista Alexandre G. S. Prado 《Journal of Thermal Analysis and Calorimetry》2011,106(2):475-481
Chitosan microspheres were applied to remove the pollutants diclofenac and dipyrone from water. Adsorption studies were adjusted
to Langmuir equation. The maximum number of adsorbed moles gave 5.25 × 10−4 and 4.83 × 10−4 mol of diclofenac and dipyrone, respectively, per gram of chitosan microspheres. The interactions in solid/liquid interface
were calorimetrically followed and gave endothermic values: +22.1 ± 1.3 and +48.7 ± 1.5 kJ mol−1, respectively, for the same sequence. Both Gibbs energy values were negative. Adsorption processes were accompanied by an
increase in entropy. These interactions were studied by FTIR spectroscopy which showed a strengthening of the CN stretching
(dislocated shifts from 1,325 to 1,371 cm−1) related to a weakening of the NH stretch caused by the interaction with drugs. 相似文献
387.
F.L. Braga 《Applied Mathematics Letters》2011,24(5):653-656
The appearance of anisotropy in certain properties such as conductivity and diffusion coefficients could be induced by the application of external magnetic fields. Using the matricial representation of SO(3) group it was possible to demonstrate that this anisotropy is characterized by a rotation of plasma current. This work presented in a didatical way the relation between the external magnetic field and some plasma parameters with the rotation angle. 相似文献
388.
Susana S. Braga Isabel S. GonÇalves Paulo Ribeiro-Claro André D. Lopes Martyn Pillinger José J.C. Teixeira-Dias 《Supramolecular chemistry》2013,25(4):359-366
Inclusion compounds have been prepared comprising g -cyclodextrin (CD) molecules as the host and half-sandwich cyano complexes of iron as the guests. High yields of crystalline one-to-one adducts were obtained by treatment of CpFe(CO) 2 CN and K[CpFe(CO)(CN) 2 ] with g -CD. In the case of CpFe(dppe)CN [dppe=bis(diphenylphosphine)ethane], a non-stoichiometric product is obtained and it is evident that the organometallic guests are easily liberated from the host cavities. The products were characterized in the solid-state by elemental analysis, powder X-ray diffraction (XRD), thermogravimetric analysis (TGA), FTIR and CP MAS NMR ( 13 C, 31 P) spectroscopy. Additional information concerning the possible structure of the inclusion compounds was obtained from ab initio calculations using a two-layer approximation. The best organometallic- g -CD interaction is obtained with deep inclusion of the cyclopentadienyl ring, a geometry that is not possible in the case of the CpFe(dppe)CN system due to the size and orientation of the dppe ligand. 相似文献
389.
390.
Tiago P.Braga Regina C.R.Santos Barbara M.C.Sales Bruno R.da Silva Antnio N.Pinheiro Edson R.Leite Antoninho Valentini 《催化学报》2014,35(4):514-523
A factorial experimental design was combined with response surface methodology(RSM) to opti-mize the catalyzed CO2 consumption by coke deposition and syngas production during the dry re-forming of CH4. The CH4 /CO2 feed ratio and the reaction temperature were chosen as the variables, and the selected responses were CH4 and CO2 conversion, the H2 /CO ratio, and coke deposition. The optimal reaction conditions were found to be a CH4 /CO2 feed ratio of approximately 3 at 700 °C, producing a large quantity of coke and realizing high CO2 conversion. Furthermore, Raman results showed that the CH4 /CO2 ratio and reaction temperature affect the system's response, particularly the characteristics of the coke produced, which indicates the formation of carbon nanotubes and amorphous carbon. 相似文献