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The Ni_n (n =19, 20) +D₂ (v, j) collision systems have been studied to investigate the dependence of cluster reactivity on the cluster temperature and the initial rovibrational states of the molecule using quasiclassical molecular dynamics simulations. The clusters are described by an embedded atom potential, whereas the interaction between the molecule and the cluster is modeled by a LEPS (London–Eyring–Polani–Sato) potential energy function. Reaction (dissociative adsorption) cross-sections are computed as functions of the collision energy for different initial rovibrational states of the molecule and for different temperatures of the clusters. Rovibrational, temperature and size-dependent rate constants are also presented, and the results are compared with earlier studies. Initial vibrational excitation of the molecule increases the reaction cross-section more efficiently than the initial rotational excitation. The reaction cross-sections strongly depend on the collision energies below 0.1 eV.

The reactions of V⁺ and VO⁺ with methanol have been investigated experimentally by FT-ICR mass spectrometer and theoretically by ab initio calculation. Both V⁺ and VO⁺ exhibit impressive reactivity with methanol. The products distribution of different reaction time indicate that in whole reaction processes methanol is adsorbed one by one, and no more than four methanol molecules can be solved in the first shell of central ion V⁺. The reaction mechanisms have been proposed, and the possible geometrical structures of products are also analyzed by DFT calculations.

The polycyclic aromatic hydrocarbons (PAHs) are chemical compounds of obvious technical and medical interest. In the present work, we analyze the optical and reactive properties of several small (6–50 Carbon atoms) and large (100–5000 Carbon atoms) irregular PAHs. These properties have been calculated by using the (Frozen) spin molecular orbital (SMO) Hartree-Fock (HF) approach, referred to as FHF, because of its high computational efficiency. There is a reasonable agreement of our results with those previously obtained by other authors. The FHF approach is (about 1000 times) faster than the conventional semi-empirical methods, and only requires the chemical formula of the PAH as input.

Bursting behaviors, driven by environmental variability, can substantially influence ecosystem services and functions and have the potential to cause abrupt population breakouts in host–parasitoid systems. We explore the impact of environment on the host–parasitoid interaction by investigating separately the effect of grazing-dependent habitat variation on the host density and the effect of environmental fluctuations on the average host population growth rate. We hence focus on the discrete host–parasitoid Beddington–Free–Lawton model and show that a more comprehensive mathematical study of the dynamics behind the onset of on–off intermittency in host–parasitoid systems may be achieved by considering a deterministic, chaotic system that represents the dynamics of the environment. To this aim, some of the key model parameters are allowed to vary in time according to an evolution law that can exhibit chaotic behavior. Fixed points and stability properties of the resulting 3D nonlinear discrete dynamical system are investigated and on–off intermittency is found to emerge strictly above the blowout bifurcation threshold. We show, however, that, in some cases, this phenomenon can also emerge in the sub-threshold. We hence introduce the novel concept of long-term reactivity and show that it can be considered as a necessary condition for the onset of on–off intermittency. Investigations in the time-dependent regimes and kurtosis maps are provided to support the above results. Our study also suggests how important it is to carefully monitor environmental variability caused by random fluctuations in natural factors or by anthropogenic disturbances in order to minimize its effects on throphic interactions and protect the potential function of parasitoids as biological control agents.

For intelligent systems to interact with external agents and changing domains, they must be able to perceive and to affect their environments while computing long term projection (planning) of future states. This paper describes and demonstrates the supervenience architecture, a multilevel architecture for integrating planning and reacting in complex, dynamic environments. We briefly review the underlying concept of supervenience, a form of abstraction with affinities both to abstraction in AI planning systems, and to knowledge-partitioning schemes in hierarchical control systems. We show how this concept can be distilled into a strong constraint on the design of dynamic-world planning systems. We then describe the supervenience architecture and an implementation of the architecture called APE (for Abstraction-Partitioned Evaluator). The application of APE to the HomeBot domain is used to demonstrate the capabilities of the architecture.

The evolution of compact surface of the 100 nm copper film deposited on the glass-ceramics doped with vanadium coating in the course of the oxidation by the CCl₄–L (L = dimethylformamide (DMF), tetrahydrofuran (THF), dimethylsulfoxide (DMSO), CCl₄ concentration ≈ 1 mol/L) was studied by atomic force microscopy (AFM) in contact mode. The dynamics of active centers formation and destruction was investigated in the course of the oxidation process. The metallic sample dissolution rate was estimated as a function of the coordinating solvent nature. The development of the metal surface oxidation was established to lead to a significant increase of surface roughness. This phenomenon can be explained by the fact that different parts of the surface react at different rates. Further course of the reaction leads to a significant decrease of the surface roughness of copper films. The amount of the metal reacted has an almost linear dependence on the reaction time. AFM scans indicate that there is the same mechanism of the reaction between copper and carbon tetrachloride for all solvents.

In this paper, a method for calculating all the Hückel molecular orbitals (MO) of large (16.000 atoms) carbon zigzag nanotubes is presented. These MO have been obtained by combining the singular value decomposition (SVD), the Sylvester–Hadamard transform, and the theory of Hamiltonian–Symplectic matrices. Numerical diagonalization of hermitian matrices is reviewed and improved. A new, more advantageous, (tri-diagonal) algorithm is proposed and analyzed. The reactivity of the atoms is described by calculating their free valence indices.

Density functional theory (DFT) calculation has been carried out to investigate the isomers of N-(1-phenyl-3-methyl-4-propenylidene-5-pyrazolone)-salicylidene. Chemical potential, chemical hardness and global electrophilicity, which are considered as global indices, have been calculated to assess the stability and reactivity of the tautomers. The condensed Fukui function is calculated for predicting the most probable sites for electrophilic attack. Molecular electrostatic potential is calculated to predict the regions for electrophilic attack.

Recent experimental studies of Liu and Groves (J. Am. Chem. Soc. 2010; 132: 12847) on dioxomanganese(V) porphyrin complexes implicated substrate halogenation in good yield. Currently, little is known of this unique mechanism, therefore to gain understanding on the halogenation mechanism and the chemical features of this oxidant we decided to do a computational (density functional theory) study. We show that the dioxomanganese(V) complex has considerably different molecular (valence) orbitals as compared to monooxomanganese(V) porphyrin due to mixing of the metal 3d orbitals with 2p orbitals on both oxygen atoms. This results in a set of three pairs of orbitals of which the bonding and nonbonding pairs are doubly occupied and the antibonding orbitals are vacant. As a consequence, the bonding character along the Mn–O bond is less in dioxomanganese(V) as compared to monooxomanganese(V) complexes and therefore this bond can formally be described as a double bond rather than a triple bond. The differences in orbital interactions and orbital energies also affect the intrinsic chemical properties of the oxidants, such as the electron affinity and pK_a values, which result in enhanced catalytic potential for dioxomanganese(V) porphyrin. Our calculations predict a halogenation mechanism in line with that proposed by experiment with an initial hydrogen atom abstraction followed by ligand exchange and halogen transfer.

In this paper, we describe some observations from the attempted reaction of Br-BsubPc with phenol in DMF and DMAc. During these efforts, we found that Br-BsubPc reacts with the respective solvents to produce axially substituted formate-BsubPc and acetate-BsubPc. When no phenol is present the reaction proceeds to completion in a relatively short period of time. However, when phenol was present in DMF the reaction produced a mixture of formate-BsubPc, phenoxy-BsubPc, and HO-BsubPc. Similar results were found for the less-reactive Cl-BsubPc and MsO-BsubPc. Aside from these observations, it was found that simple heating in wet acetone of Br-BsubPc quantitatively produced HO-BsubPc after a facile workup. This method of producing HO-BsubPc removes the high temperatures, long reaction times, and harmful chemicals required in other synthetic methods. These results are relevant to anyone considering the reaction of BsubPcs in polar aprotic solvents.

Synthesis of two trans-dihydroxy platinum(IV) porphyrins (TPP, tetraphenylporphyrin and F${}_{20}$TPP, tetrakispentafluorophenylporphyrin) by dimethyl dioxirane (DMD) oxidation of their Pt${}^{II}$ porphyrin precursors have been described. The oxidation state of Pt cation in such complexes was assessed by X-ray photoelectron spectroscopy and shown to be $+$4. More importantly, proton was found to promote the formation and stabilization of the trans-dihydroxy platinum(IV) porphyrins, as revealed by UV-vis spectroscopic results and single crystal structures. In addition, these trans-dihydroxy Pt${}^{IV}$ porphyrins were much easier to be reduced than their Pt(II) counterparts and capable to transfer oxygen atom to triphenylphosphine and thioanisol, which is important for further application of Pt(IV) complexes in catalytic reactions.

Conventionally, most researches of ecological models focus mainly on the asymptotic stability properties near equilibria. However, transient effects can be important. It dominates the dynamics seen in experimental or field studies. Transient behavior near an equilibrium is measured by resilience, reactivity, the maximum amplification of a perturbation and the time at which the maximum amplification occurs. In this paper, we demonstrate emphatically the calculation of the amplification envelope of a homogeneous system of linear equations, then apply it to three ecological models. We conclude that transient amplification of perturbations to a stable equilibrium should be a very common ecological phenomenon, and reactive systems have huge changes around their equilibria.

Catalysis, as the key to minimize the energy requirement and environmental impact of today's chemical industry, plays a vital role in many fields directly related to our daily life and economy, including energy generation, environment control, manufacture of chemicals, medicine synthesis, etc. Rational design and fabrication of highly efficient catalysts have become the ultimate goal of today's catalysis research. For the purpose of handling and product separation, heterogeneous catalysts are highly preferred for industrial applications and a large part of which are the composites of transition metal nanoparticles (TMNPs). With the fast development of nanoscience and nanotechnology and assisted with theoretical investigations, basic understanding on tailoring the electronic structure of these nanocomposites has been gained, mainly by precise control of the composition, morphology, interfacial structure and electronic states. With the rise of graphene, chemical routes to prepare graphene were developed and various graphene-based composites were fabricated. Transition metal nanoparticles-reduced graphene oxide (TMNPs–rGO) composites have attracted considerable attention, because of their intriguing catalytic performance which have been extensively explored for energy- and environment-related applications to date. This review summarizes our recent experimental and theoretical efforts on understanding the superior catalytic performance of subnanosized TMNPs–rGO composites.

For clusters Si_nC_m with (n+m ≤ 5), we have performed all-electron full-geometry optimizations, at the ab initio level HF/6-31G*//HF/3-21G*. For the ground states, we assess the size and composition dependence of the vibrational spectra, incremental binding energies and HOMO-LUMO gaps. Furthermore, we have performed PM3 calculations on silafullerenes with formula C_2n−mSi_m (2n = 28,60; m=1-3). We study the substitution of mC-atoms by Si ones in different positions and the effect on the electronic properties and stabilities. These results shed some light on the observed photofragmentation patterns. Thereafter, two-dimensional polymerization of C₆₀ is studied through the structural and electronic properties of clusters of up to 7 crosslinked C₆₀ molecules, calculated at the semiempirical AM1 and PM3 levels within the linear scaling divide and conquer method of Yang. As far as the reactivity of fullerenes is concerned, we analyze first the effect of the curvature in the shape and energy of frontier orbitals. Then, as one of the most important reactions for the functionalization of fullerenes, we study the Diels-Alder cycloaddition of 1,3-butadiene to C₆₀, C₇₀, and to a series of different buckybowls to discuss the effect of increasing size and curvature in the barriers and reaction energies. Successive addition to C₆₀ is also discussed.

The highly reactive coke have a great influence on the iron making process. So there is an important significance to research highly reactive coke. Two aspects of effect about highly reactive coke on the iron making process were described. The research situation of highly reactive coke is summarized, which mainly includes the influence on coke when adding alkali, alkaline earth metals, transition metals. Then some representative compounds are chose to analyze the effect on the coke and iron making process.