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111.
112.
Journal of Applied Spectroscopy - The grafting of specific functional groups has been drawing attention later as a simple and effective way to modify materials surfaces to induce a particular... 相似文献
113.
E Bellido I Ojea-Jiménez A Ghirri C Alvino A Candini V Puntes M Affronte N Domingo D Ruiz-Molina 《Langmuir : the ACS journal of surfaces and colloids》2012,28(33):12400-12409
Atomic force microscopy is shown to be an excellent lithographic technique to directly deposit nanoparticles on graphene by capillary transport without any previous functionalization of neither the nanoparticles nor the graphene surface while preserving its integrity and conductivity properties. Moreover this technique allows for (sub)micrometric control on the positioning thanks to a new three-step protocol that has been designed with this aim. With this methodology the exact target coordinates are registered by scanning the tip over the predetermined area previous to its coating with the ink and deposition. As a proof-of-concept, this strategy has successfully allowed the controlled deposition of few nanoparticles on 1 μm(2) preselected sites of a graphene surface with high accuracy. 相似文献
114.
Míriam Ruiz J. Domingo Sánchez Pilar López-Alvarado J. Carlos Menéndez 《Tetrahedron》2012,68(2):705-710
Two mild and general protocols for the high-yielding deprotection of indoles and related fused heterocyclic systems are described, involving either hydride transfer from LDA or hydrolysis by the DBU–water system. Both methods were shown to tolerate a wide variety of substituents and functional groups, but the hydrolytic one proved to be particularly general, being compatible with 2-alkyl substituents, aldehydes, ketones, carboxylic acids, halogens, ethers, amides and esters. Yields were normally excellent in both cases, but were usually slightly higher for the reductive method. Taken together, these two protocols provide a general solution to the problem of pivaloyindole deprotection. 相似文献
115.
Jose J. López-Espín Antonio M. Vidal Domingo Giménez 《Journal of Computational and Applied Mathematics》2012
This paper analyzes the solution of simultaneous equations models. Efficient algorithms for the two-stage least squares method using QR-decomposition are developed and studied. The reduction of the execution time when the structure of the matrices in each equation is exploited is analyzed theoretically and experimentally. An efficient algorithm for the indirect least squares method is developed. Some techniques are used to accelerate the solution of the problem: parallel versions for multicore systems, and extensive use of the MKL library, thus obtaining efficient, portable versions of the algorithms. 相似文献
116.
C. Torres-Torres M.L. García-Cruz L. Castañeda R. Rangel Rojo L. Tamayo-Rivera A. Maldonado M. Avendaño-Alejo R. Torres-Martínez 《Journal of luminescence》2012,132(4):1083-1088
Chromium doped zinc oxide thin solid films were deposited on soda–lime glass substrates. The photoconductivity of the material and its influence on the optical behavior was evaluated. A non-alkoxide sol–gel synthesis approach was used for the preparation of the samples. An enhancement of the photoluminescence response exhibited by the resulting photoconductive films with embedded chromium nanoclusters is presented. The modification in the photoconduction induced by a 445 nm wavelength was measured and then associated with the participation of the optical absorptive response. In order to investigate the third order optical nonlinearities of the samples, a standard time-resolved Optical Kerr Gate configuration with 80 fs pulses at 830 nm was used and a quasi-instantaneous pure electronic nonlinearity without the contribution of nonlinear optical absorption was observed. We estimate that from the inclusion of Cr nanoclusters into the sample results a strong optical Kerr effect originated by quantum confinement. The large photoluminescence response and the important refractive nonlinearity of the photoconductive samples seem to promise potential applications for the development of multifunctional all-optical nanodevices. 相似文献
117.
Andrés J Berski S Domingo LR González-Navarrete P 《Journal of computational chemistry》2012,33(7):748-756
We analyze the behavior of the energy profile of the ring‐closure process for the transformation of (3Z,5Z)‐octa‐1,3,5,7‐tetraene 5 to (1Z,3Z,5Z)‐cycloocta‐1,3,5‐triene 6 through a combination of electron localization function (ELF) and catastrophe theory (CT). From this analysis, concepts such as bond breaking/forming processes, formation/annihilation of lone pairs, and other electron pair rearrangements arise naturally through the reaction progress simply in terms of the different ways of pairing up the electrons. A relationship between the topology and the nature of the bond breaking/forming processes along this rearrangement is reported. The different domains of structural stability of the ELF occurring along the intrinsic reaction path have been identified. The reaction mechanism consists of six steps separated by fold and cusp catastrophes. The transition structure is observed in the third step, d(C1? C8) = 2.342 Å, where all bonds have topological signature of single bonds (C? C). The “new” C1? C8 single bond is not formed in transition state and respective catastrophe of the ELF field (cusp) is localized in the last step, d(C1? C8) ≈ 1.97 Å, where the two monosynaptic nonbonding basins V(C1) and V(C8) are joined into single disynaptic bonding basin V(C1,C8). The V(C1,C8) basin corresponds to classical picture of the C1? C8 bond in the Lewis formula. In cycloocta‐1,3,5‐triene 6 the single C1? C8 bond is characterized by relatively small basin population 1.72e, which is much smaller than other single bonds with 2.03 and 2.26e. © 2011 Wiley Periodicals, Inc. J Comput Chem, 2011 相似文献
118.
Luis R. Domingo 《Theoretical chemistry accounts》2000,104(3-4):240-246
The chemoselectivity and regioselectivity of the domino intermolecular [4 + 2]/[3 + 2] cycloaddition reactions of nitroalkenes
with substituted alkenes, vinyl ethers as electron-rich alkenes and vinyl ketones as electron-poor alkenes, have been studied
using density functional theory (DFT) methods with the B3LYP functional and the 6-31G* basis set. These domino processes comprise two consecutive cycloaddition reactions: the first one is an intermolecular [4 + 2]
cycloaddition of the vinyl ether to the nitroalkene to give a nitronate intermediate, which then affords the final nitroso
acetal adduct through an intermolecular [3 + 2] cycloaddition reaction with the vinyl ketone. The two consecutive cycloadditions
present total chemoselectivity and ortho regioselectivity. While first [4 + 2] cycloaddition reaction takes place along the
attack of the electron-rich alkene to nitroalkene, the [3 + 2] one takes place along the attack of the electron-poor alkene
to the corresponding nitronate intermediate. This DFT study is in complete agreement with the experimental results.
Received: 16 September 1999 / Accepted: 3 February 2000 / Published online: 2 May 2000 相似文献
119.
We consider a steady-state heat conduction problem Pα withmixed boundary conditions for the Poisson equation in a bounded multidimensional domain Ω depending of a positive parameter α which represents the heat transfer coefficient on a portion Γ1 of the boundary of Ω. We consider, for each α > 0, a cost function Jα and we formulate boundary optimal control problems with restrictions over the heat flux q on a complementary portion Γ2 of the boundary of Ω. We obtain that the optimality conditions are given by a complementary free boundary problem in Γ2 in terms of the adjoint state. We prove that the optimal control q and its corresponding system state u and adjoint state p for each α are strongly convergent to qop, u and p in L2(Γ2), H1(Ω), and H1(Ω) respectively when α → ∞. We also prove that these limit functions are respectively the optimal control, the system state and the adjoint state corresponding to another boundary optimal control problem with restrictions for the same Poisson equation with a different boundary condition on the portion Γ1. We use the elliptic variational inequality theory in order to prove all the strong convergences. In this paper, we generalize the convergence result obtained in Ben Belgacem-El Fekih-Metoui, ESAIM:M2AN, 37 (2003), 833-850 by considering boundary optimal control problems with restrictions on the heat flux q defined on Γ2 and the parameter α (which goes to infinity) is defined on Γ1. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
120.
An easy and efficient method for the synthesis of isoindoloisoquinolines, and the assignment of a new structure for the alkaloid (±)-nuevamine are reported. 相似文献