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41.
Marcos Caroli Rezende Ingrid PonceRubén Oñate Iriux AlmodovarCarolina Aliaga 《Tetrahedron letters》2014
The reaction between N-(2,4-dinitrophenyl)-4-(4-pyridyl)pyridinium chloride and 4-aminothiophenol led to an unexpected displacement of the 2,4-dinitrophenyl group, in contrast with the normal Zincke product formed with other nucleophilic 4-substituted anilines. Evidence for a SET process was obtained from EPR spectra of the reaction mixture. 相似文献
42.
Ernesto Rezende Souza Ercules E.S. Teotonio Hermi F. Brito 《Journal of luminescence》2010,130(2):283-6601
Red, blue and green emitting rare earth compounds (RE3+=Eu3+, Gd3+ and Tb3+) containing the benzenetricarboxylate ligands (BTC) [hemimellitic (EMA), trimellitic (TLA) and trimesic (TMA)] were synthesized and characterized by elemental analysis, complexometric titration, X-ray diffraction patterns, thermogravimetric analysis and infrared spectroscopy. The complexes presented the following formula: [RE(EMA)(H2O)2], [RE(TLA)(H2O)4] and [RE(TMA)(H2O)6], except for Tb-TMA compound, which was obtained only as anhydrous. Phosphorescence data of Gd3+-(BTC) complexes showed that the triplet states (T) of the BTC3− anions have energy higher than the main emitting states of the Eu3+ (5D0) and Tb3+ (5D4), indicating that BTC ligands can act as intramolecular energy donors for these metal ions. The high values of experimental intensity parameters (Ω2) of Eu3+-(BTC) complexes indicate that the europium ion is in a highly polarizable chemical environment. Based on the luminescence spectra, the energy transfer from the T state of BTC ligands to the excited 5D0 and 5D4 levels of the Eu3+ and Tb3+ ions is discussed. The emission quantum efficiencies (η) of the 5D0 emitting level of the Eu3+ ion have been also determined. In the case of the Tb3+ ion, the photoluminescence data show the high emission intensity of the characteristic transitions 5D4→7FJ (J=0-6), indicating that the BTC ligands are good sensitizers. The RE3+-(BTC) complexes act as efficient light conversion molecular devices (LCMDs) and can be used as tricolor luminescent materials. 相似文献
43.
Vieira EF Cestari AR de Santos EB Rezende CX 《Journal of colloid and interface science》2006,298(1):74-78
Isothermal calorimetry was used to determine enthalpy changes for interaction of divalent cobalt, nickel, copper, and zinc chlorides with silica gel functionalized with vanillin, Sil-Van. The thermal effect, Q(int), and the corresponding amount of cation that interacts, n(int), were obtained in the same experiment. Langmuir expressions for adsorption isotherms were applied to determine the maximum adsorption capacity to form a monolayer, N(mon), and the energy of interaction for a saturated monolayer per gram of Sil-Van, Q(mon). From knowledge of N(mon) and Q(mon), the molar enthalpy of interaction for formation of a monolayer of anchored cations per gram of Sil-Van, Delta(mon)H(m), was determined. Interactions between the Lewis-acidic cations and the donor atom attached to silica are reflected by Delta(mon)Hm values in the order Ni2+ > Cu2+ > Zn2+ congruent with Co2+. 相似文献
44.
粉粒体两相流的电容层析成象测量 总被引:4,自引:0,他引:4
粉粒体系统中的固相浓度分布的在线测量是十分困难的问题.电容层析成象技术是一种近年来发展起来的非侵入式快速浓度场测量技术.它不干扰流场,不受流动中颗粒浓度、加速度、不透明等因素的制约.本文讨论其测量原理、应用、近期进展、存在的主要问题及其解决的对策. 相似文献
45.
46.
De Lazari Ferreira Luiza Calado Hállen Daniel Rezende 《Journal of Solid State Electrochemistry》2018,22(5):1507-1515
Journal of Solid State Electrochemistry - Polythiophenes are conjugated polymers that are highly promising candidates for use as an active layer in flexible optoelectronic devices. The... 相似文献
47.
Iriux Almodovar Marcos Caroli Rezende Bruce K. Cassels Macarena García‐Arriagada 《Journal of Physical Organic Chemistry》2017,30(8)
The mechanism of the cyclization step of the Pictet‐Spengler reaction between acetaldehyde and dopamine to give salsolinol and isosalsolinol was studied computationally, using density functional theory. The preferential formation in acidic media of salsolinol, the product of para‐cyclization, and the requirement of a neutral pH for the formation of the ortho‐cyclized isosalsolinol are explained in terms of 2 different mechanistic routes with an iminium ion or a phenolate‐iminium zwitterion as starting reactants. 相似文献
48.
49.
Quantum Zeno and anti-Zeno paradoxes 总被引:1,自引:0,他引:1
Continuous observation of a time independent projection operator is known to prevent change of state (the quantum Zeno paradox).
We discuss the recent result that generic continuous measurement of time dependent projection operators will in fact ensure
change of state: an anti-Zeno paradox. 相似文献
50.
M. F. S. Rezende R. A. Mansur H. -D. Pfannes A. I. C. Persiano 《Hyperfine Interactions》1991,66(1-4):319-323
Two distinct phases of the Fe?Co?Nb and three of the Fe?Co?V systems have been studied by means of X-ray diffraction and Mössbauer spectroscopy. The dependence of the lattice parameter of the alpha phase on the nominal solute content in equiatomic FeCo together with the alterations of the Mössbauer spectra have shown a very limited solubility of niobium in alpha FeCo. There are indications that the solubility of vanadium in alpha FeCo increases with increasing nominal content of solute in the alloy. A mechanism involving the withdrawal of cobalt from the alpha matrix to form a phase rich in Co and V (gamma) is proposed to explain such a varying solubility. The vanadium content of the sigma phase in equiatomic FeCo alloys with 22 wt% V is proposed to be less than 50 at%. 相似文献