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111.
Lucas Pizzuti Luciana A. Piovesan Alex F.C. Flores Frank H. Quina Claudio M.P. Pereira 《Ultrasonics sonochemistry》2009,16(6):728-731
An efficient and green synthesis of thiocarbamoyl-3,5-diaryl-4,5-dihydro-1H-pyrazoles via the condensation of chalcones with thiosemicarbazide in ethanol and KOH under ultrasound irradiation is reported. The products were isolated in good yields after short reaction times. 相似文献
112.
113.
Visscher L 《Journal of computational chemistry》2002,23(8):759-766
A perspective on the use of the relativistic Dirac equation in quantum chemistry is given. It is demonstrated that many of the computational problems that plague the current implementations of the different electronic structure methods can be overcome by utilizing the locality of the small component wave function and density. Possible applications of such new and more efficient formulations are discussed. 相似文献
114.
The change of the FWHM of the mass distribution of the fission products as a function of angular momentum is interpreted as a signature for a mechanism which is intermediate between compound nucleus formation and deep inelastic reactions. An intermediate composite system is assumed to be formed during the reaction, which undergoes fission. This kind of mechanism can therefore be called fast fission phenomena. It is related to the existence of a long lifetime component in déep inelastic reactions. Within the framework of a simple statistical model a qualitative as well as a quantitative estimate is done for a particular system. The conditions under which such a mechanism can be observed are discussed. 相似文献
115.
116.
Guyon F Absalon Ch Eloy A Salagoity MH Esclapez M Medina B 《Rapid communications in mass spectrometry : RCM》2003,17(20):2317-2322
The triacylglycerol (TAG) composition study of cocoa butter (CB) and cocoa butter equivalents (CBEs) has been performed by gas chromatography (GC) and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS). These two techniques provided comparable results. The advantage of the MALDI technique was the detection of each compound comprising the triacylglycerol classes (Cn). Moreover, comparison of the data obtained by these two techniques indicated that TAG relative percentages could be obtained quantitatively with the MALDI technique. These techniques have been applied for the composition determination of CB + CBE mixtures. Encouraging results showed that it is possible to quantify an admixture containing as little as 4% of CBE. 相似文献
117.
Benjamin Richard Frédéric Ragueneau Lucas Adelaïde Christian Cremona 《European Journal of Mechanics - A/Solids》2011,30(6):950-961
Taking into account the specific behavior of the steel/concrete interface is of primary importance to predict properly the structural response of RC structures. Several constitutive models have been proposed in the literature within the framework of nonlinear finite element method (2D and 3D). Such approaches usually lead to high computational costs due to the large number of degrees of freedom. In the present paper, a multifiber-based model including the steel/concrete interface behavior is proposed. Despite the fact that the kinematics of the multi-fiber approach is based on the theory of beams, this simplified strategy accounts for local phenomena such as the relative sliding between concrete and steel. Furthermore, this steel/concrete interface constitutive model can be extended to model the loss of bond properties due to corrosion. The numerical implementation aspects are described and local responses at the Gauss point level are exposed in the cases of monotonic loadings with and without corrosion. The efficiency and the reliability of the proposed approach are tested on structural case studies which highlight a good agreement between numerical and experimental results. This multifiber-based model provides a pertinent tool for the engineers concerns with the structural assessment of degraded reinforced concrete structures. 相似文献
118.
Formation of inclusion complexes and controlled release of atrazine using free or silica-anchored β-cyclodextrin 总被引:1,自引:0,他引:1
Lucas Bragan?a de Carvalho Luciana de Matos Alves Pinto 《Journal of inclusion phenomena and macrocyclic chemistry》2012,74(1-4):375-381
Immobilization of cyclodextrin on the surface of silica was performed using citric acid as the bonding agent. Inclusion complexes of atrazine with free (CD) or anchored (CDSI) β-cyclodextrin were prepared and then characterized using infrared spectroscopy, X-ray diffraction and differential scanning calorimetry. The complexation reaction showed first order kinetics, with a rate constant (k) of 8.72?×?10?3 min?1. There was a rapid increase of absorbance in the first 40?min, followed by attainment of equilibrium after ~2?h. The stoichiometry of the reaction was 1:1, with both free and anchored β-cyclodextrin increasing the solubilization of atrazine in an aqueous medium (by around 1.5 and 3.4 times, respectively). The association constant (K a) of the complex was 28.93?L?mol?1 using CD and 130.68?L?mol?1 using CDSI. In release tests, 62% of the atrazine complexed with CDSI or β-CD was released after 40?h, while 83% of free atrazine was released during the same period. 相似文献
119.
S. Maurugeon B. Bureau C. Boussard-Pldel A.J. Faber X.H. Zhang W. Geliesen J. Lucas 《Journal of Non》2009,355(37-42):2074-2078
Te80−xGe20Sex glasses have been prepared along the GeSe4–GeTe4 axis using the classical method in silica tube under vacuum. A phase separation domain appears for composition around Te40Ge20Se40. Our attention was turned toward the Te-rich compositions corresponding to 1 < x < 5 at.%. These glasses are transparent from 4 to about 20 μm without any purification of the starting elements. Furthermore the difference ΔT between the crystallization temperature Tx and the vitreous transition temperature Tg lies at about 110 °C that is to say 30 °C higher than for the GeTe4 reference glass. Finally the introduction of a few percentages of Se makes the glasses much easier to prepare and more stable against crystallization, making them drawable as optical fibers for example. Taking into account their transparency window, encompassing the CO2 absorption band around 15 μm, the Te80−xGe20Sex with 1 < x < 5 at.% could become matchless composition for the CO2 infrared detection as planed by the Darwin mission of the European Space Agency. 相似文献
120.
van der Waals interactions between nanoclusters have been calculated with a self-consistent, coupled dipole method. The method accounts for all many-body (MB) effects. Comparison is made between the exact potential energy, V, and the values obtained with two alternative methods: the sum of two-body interactions and the sum of two-body and three-body interactions. For all cases considered, the three-body term alone does not accurately represent the MB contributions to V. MB contributions are especially large for shape-anisotropic clusters. 相似文献