Density functional theory calculations on the reactivity of a Ni(II)-superoxo complex in C-H bond activation, aromatic hydroxylation and heteroatom oxidation reactions have been explored; the Ni(II)-superoxo complex is able to react with substrates with weak C-H bonds and PPh(3). 相似文献
In this paper, we study naturally reductive Randers metrics on homogeneous manifolds. We first prove that naturally reductive Randers metrics are of Berwald type. We then give an explicit formula for the flag curvature of naturally reductive Randers metrics. Finally a necessary and sufficient condition for invariant Randers metrics on homogeneous manifolds being naturally reductive is given. 相似文献
Ukrainian Mathematical Journal - Let (M,g) be a Riemannian manifold and let TM be its tangent bundle equipped with a Riemannian (or pseudo-Riemannian) lift metric derived from g. We give a... 相似文献
A series of hydrogen‐abstraction barriers of a nonheme iron(IV)–oxo oxidant mimicking the active species of taurine/α‐ketoglutarate dioxygenase (TauD) are rationalized by using a valence‐bond curve‐crossing diagram (see figure). It is shown that the barriers correlate with the strength of the C? H bond. Furthermore, electronic differences explain the differences between nonheme and heme iron(IV)–oxo hydrogen‐abstraction barriers.
In this study, we have constructed a new numerical approach for solving the time-dependent linear and nonlinear Fokker-Planck equations. In fact, we have discretized the time variable with Crank-Nicolson method and for the space variable, a numerical method based on Generalized Lagrange Jacobi Gauss-Lobatto(GLJGL) collocation method is applied. It leads to in solving the equation in a series of time steps and at each time step, the problem is reduced to a problem consisting of a system of algebraic equations that greatly simplifies the problem. One can observe that the proposed method is simple and accurate. Indeed, one of its merits is that it is derivative-free and by proposing a formula for derivative matrices, the difficulty aroused in calculation is overcome, along with that it does not need to calculate the General Lagrange basis and matrices; they have Kronecker property. Linear and nonlinear Fokker-Planck equations are given as examples and the results amply demonstrate that the presented method is very valid, effective,reliable and does not require any restrictive assumptions for nonlinear terms. 相似文献
Many enzymes in nature utilize molecular oxygen on an iron center for the catalysis of substrate hydroxylation. In recent years, great progress has been made in understanding the function and properties of iron(IV)-oxo complexes; however, little is known about the reactivity of iron(II)-superoxo intermediates in substrate activation. It has been proposed recently that iron(II)-superoxo intermediates take part as hydrogen abstraction species in the catalytic cycles of nonheme iron enzymes. To gain insight into oxygen atom transfer reactions by the nonheme iron(II)-superoxo species, we performed a density functional theory study on the aliphatic and aromatic hydroxylation reactions using a biomimetic model complex. The calculations show that nonheme iron(II)-superoxo complexes can be considered as effective oxidants in hydrogen atom abstraction reactions, for which we find a low barrier of 14.7 kcal mol(-1) on the sextet spin state surface. On the other hand, electrophilic reactions, such as aromatic hydroxylation, encounter much higher (>20 kcal mol(-1)) barrier heights and therefore are unlikely to proceed. A thermodynamic analysis puts our barrier heights into a larger context of previous studies using nonheme iron(IV)-oxo oxidants and predicts the activity of enzymatic iron(II)-superoxo intermediates. 相似文献
In this work, two all-fiber interferometric configurations based on suspended core fibers (SCF) are investigated. A Fabry–Pérot cavity (FPC) made of SCF spliced in-between segments of single-mode and hollow-core fiber is proposed. The interferometric signals are generated by the refractive-index mismatches between the two fibers in the splice region and at the end of the suspended-core fiber. An alternative sensing head configuration formed by the insertion of a length of SCF as a birefringence element in a Sagnac loop interferometer is also demonstrated. In this structure, the interferometric signals are generated by interfering two counter propagating beams with different polarization states which propagate through a length of SCF as a birefringence element. The sensitivity to pressure and temperature was determined for both configurations. The results show that the pressure sensitivities are ? 4.68 × 10? 5 nm/psi and 0.032 nm/psi for FPC and Sagnac loop interferometers, respectively. The temperature sensitivity of both structures has been obtained and the results have been discussed. 相似文献