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291.
Miguel A. Hernández Balboa Velia Vela Arévalo Victor H. Abrego Reyes Ana M. Velázquez A. Ganem-Quintanar David Quintanar Brígida Camacho Guadalupe Nava Arzaluz M. Rosales-Hoz Marco A. Leyva Enrique Angeles 《Chromatographia》2008,67(1-2):193-196
The results of CE studies of solid inclusion complexes of chlorambucil (CHL) and trimethyl-β-cyclodextrin (TM-β-CD) are presented.
Chlorambucil has low stability in aqueous solution, so the formation of complexes with β-CD is a good way to improve its stability
and dissolution. The experimental results confirm the existence of inclusion complexes. CE can differentiate free CHL from
CHL–TM-β-CD complexes due to their different electrophoretic mobilities. 相似文献
292.
Rivero O Sanchis C Huerta F Morallón E 《Physical chemistry chemical physics : PCCP》2012,14(29):10271-10278
Ascorbic acid molecules in either acid or conjugate base forms have been oxidized on self-doping carboxylated polyaniline thin films. The kinetic model proposed by Bartlett et al. has been successfully applied to the catalytic reactions. Active sites in the polymer have been identified as the rings having quinoid character. The existence of significant electrostatic repulsions between ionogenic groups at the self-doping polymer and negatively charged ascorbate molecules has been established thanks to the analysis of the pH dependence of the Michaelis constant. It has been found that in contrast to inorganic conductors the regeneration of active sites in polyaniline-based materials is slower at higher potentials. Such a behavior can be satisfactorily correlated with the potential dependence of the polymer electronic conductivity. 相似文献
293.
Sánchez-Muñoz BA Aguilar MI King-Díaz B Rivero JF Lotina-Hennsen B 《Molecules (Basel, Switzerland)》2012,17(2):1437-1447
The n-hexane extract of S. salignus plants inhibited ATP synthesis and two sesquiterpenes, the β-caryophyllene (1) and caryophyllene oxide (2) were isolated from this nonpolar fraction. Compound 1 inhibited by 42% the root elongation of Physalis ixocarpa seedlings at 50 μg/mL and by 53% at 150 μg/mL, whereas at 150 μg/mL this compound only inhibited root elongation of Echinochloa crus-galli by 30%. On the other hand, compound 2 had no effect on either germination or root and stem growth of E. cruss galli and P. ixocarpa. However, 1 and 2 inhibited the dry biomass of P. ixocarpa plants grown for 18 days previous to treatment and it was found that 1 was the most active biomass inhibitor. The Chl a fluorescence transient in vivo experiment indicates that 1 (100 μg/mL) has a major effect at 72 h after treatment on leaves of P. ixocarpa plants by inhibiting photosystem II (PS II) transforming active reaction centers to "heat sinks" or the formation of silent reaction centers unable to reduce Q(A). β-Caryophyllene also induces chlorosis on treated leaves. 相似文献
294.
We discuss the existence and characterization of quasi-stationary distributions and Yaglom limits of self-similar Markov processes that reach 0 in finite time. By Yaglom limit, we mean the existence of a deterministic function g and a non-trivial probability measure ν such that the process rescaled by g and conditioned on non-extinction converges in distribution towards ν. We will see that a Yaglom limit exists if and only if the extinction time at 0 of the process is in the domain of attraction of an extreme law and we will then treat separately three cases, according to whether the extinction time is in the domain of attraction of a Gumbel, Weibull or Fréchet law. In each of these cases, necessary and sufficient conditions on the parameters of the underlying Lévy process are given for the extinction time to be in the required domain of attraction. The limit of the process conditioned to be positive is then characterized by a multiplicative equation which is connected to a factorization of the exponential distribution in the Gumbel case, a factorization of a Beta distribution in the Weibull case and a factorization of a Pareto distribution in the Fréchet case. 相似文献
295.
Guadalupe López Laurrabaquio M. Begoña Torres Eva. M. Fernández L. Carlos Balbás 《Journal of mathematical chemistry》2010,48(1):109-117
We have shown recently that the ground state and low-lying energy isomers of the endohedral M@Si16 clusters (M = Sc−, Ti, V+) have a nearly spherical cage-like symmetry with a closed shell electronic structure which conforms them as exceptional stable
entities. This is manifested, among other properties, by a large Homo–Lumo gap about 2 eV which suggest the possibility of
using these clusters as basic units (superatoms) to construct optoelectronic materials. As a first step in that direction,
we have studied in this work, by means of first principles calculations, the trends in the formation of [Ti@Si16]
n
, [Sc@Si16K]
n
, and [V@Si16F]
n
aggregates as their size increases, going from linear to planar to three dimensional arrangements. The most favorable configurations
for n ≥ 2 are those formed from the fullerene-like D4d
isomer of M@Si16, instead of the ground state Frank–Kasper T
d
structure of the isolated M@Si16 unit, joined by Si–Si bonds between the Si atoms of the square faces. In all cases the Homo–Lumo gap for the most favorable
structure decrease with the size n. Trends for the binding energy, dipole moment, and other electronic properties are also discussed. Several crystal structures
constructed from these superatom, supermolecules, and aggregates have been tested and preliminary results are summarily commented. 相似文献
296.
A surface integral equation together with the multilevel fast multipole algorithm is successfully applied to fast and accurate resolution of plasmonic problems involving a large number of unknowns. The absorption, scattering, and extinction efficiencies of several plasmonic gold spheres of increasing size are efficiently obtained solving the electric and magnetic current combined-field integral equation. The numerical predictions are compared with reference analytic results to demonstrate the accuracy, suitability, and capabilities of this approach when dealing with large-scale plasmonic problems. 相似文献
297.
A. E. Choque Rivero Yu. I. Karlovich A. E. Merzon P. N. Zhevandrov 《Russian Journal of Mathematical Physics》2012,19(3):373-384
We make more precise the Limiting Amplitude Principle in the two-dimensional scattering of an incident plane harmonic wave by a wedge. We find the long-time asymptotic regime of convergence of the amplitude of the cylindrical wave diffracted by the vertex of a wedge to the limiting amplitude of the solution to the corresponding stationary problem. The asymptotics turns out to be uniform on compacta and depends on the magnitude of the wedge and the profile of the incident wave. The cases of Dirichlet-Dirichlet and Dirichlet-Neumann boundary conditions are considered. 相似文献
298.
Radiative-hydrodynamics and radiative transfer simulations of astrophysical plasmas require the determination of radiative properties. However, most of the plasma radiative properties are calculated assuming the plasma in coronal equilibrium or local thermodynamic equilibrium regimes that is often not the case for many scenarios. In this work, we present nonlocal thermodynamic equilibrium calculations of radiative opacities of Fe and S and of an astrophysical plasma mixture for temperatures larger than 100 eV. We also analyze the departure from local thermodynamic equilibrium simulations. 相似文献
299.
Cruz Guillermo J. Ordóñez-Regil Eduardo Almazán-Torres María Guadalupe 《Journal of Radioanalytical and Nuclear Chemistry》2019,321(2):421-426
Journal of Radioanalytical and Nuclear Chemistry - Alpha emitters in Mexican Pacific beach sands were studied to calculate the 234U/238U activity ratio (AR) and the 239+240Pu content. AR was... 相似文献