Mechanisms of Photoreactions of 2,6-Diphenyl-1,4-benzoquinone and Its Dimer in Different Solvents

Russian Journal of Physical Chemistry A - An investigation of 2,6-diphenyl-1,4-benzoquinone (a class of substituted benzoquinones) and its dimer is performed to study the effect the solvents have...     

Development of Chemical Polarization of Nuclei During Photolysis of Benzoquinones with Aromatic Amines

Formation of nuclei polarization via triplet mechanism has been observed and described, allowing reliable identification of ion-radicals stages of the reaction, estimation of the triplets and ion-radical pairs lifetime from the effects of chemical polarization of the nuclei. The data on relative values of isotropic and anisotropic interactions of unpaired electrons and nuclei have been obtained.     

Mechanisms of photochemical reactions of <Emphasis Type="Italic">para</Emphasis>-benzoquinones with thiols

The mechanisms of quinone reduction by thiols containing α-hydrogen atoms were established using chemically induced dynamic nuclear polarization effects. It was found that substituents in the quinone nucleus change the nature of the primary radical pair. In the photolysis of 2,6-dimethyl-1,4-benzoquinone (1), the radical pair consists of semiquinone and thioalkyl radicals, whereas in the case of 2,6-diphenyl-1,4-benzoquinone (2), the radical pair is composed of semiquinone and thiyl radicals. Quinone 2 is readily photolyzed with any thiol to give dibenzofuran derivative as the final products.     

Identifying Elementary Acts of the Photoreactions between Benzophenones and Aliphatic Amines from the Effects of CIDNP

Russian Journal of Physical Chemistry A - Mechanisms and elementary acts of the photoreduction of benzophenones with triethylamine, N,N-diethyl-p-toluidine, N,N-dimethylaniline, phenols, and...     

On-line control model for network construction projects

An activity-on-arc network project of the PERT type with random activity durations is considered. For each activity, its accomplishment is measured in percentages of the total project. When operated, each activity utilizes resources of a pregiven capacity and no resource reallocation is undertaken in the course of the project's realization. Each activity can be operated at several possible speeds that are subject to random disturbances and correspond to one and the same resource capacity; that is, these speeds depend only on the degree of intensity of the project's realization. For example, in construction projects partial accomplishments are usually measured in percentages of the total project, while different speeds correspond to different hours a day per worker. The number of possible speeds is common to all activities. For each activity, speeds are sorted in ascending order of their average values—namely speeds are indexed. It is assumed that at any moment t>0 activities, in operation at that moment, have to apply speeds of one and the same index that actually determines the project's speed. The progress of the project can be evaluated only via inspection at control points that have to be determined. The project's due date and the chance constraint to meet the deadline are pregiven. An on-line control model is suggested that, at each control point, faces a stochastic optimization problem. Two conflicting objectives are imbedded in the model:(1) to minimize the number of control points, and(2) to minimize the average index of the project's speeds which can be changed only at a control point.At each routine control point, decision-making centers on determining the next control point and the new index of the speeds (for all activities to be operated) up to that point. The model's performance is verified via simulation.The developed on-line control algorithm can be used for various PERT network projects which can be realized with different speeds, including construction projects and R&D projects.     

Characteristics of Triplet Exciplexes in the Photolysis of 2,6-Diphenyl-1,4-benzoquinone with Amines

Russian Journal of Physical Chemistry A - The spectral and kinetic characteristics of short-lived triplet exciplexes, formed by quenching the triplet state of acceptor 2,6-diphenyl-1,4-benzoquione...     

Determination of the supercooling dependence of the (211) facet of BGO crystal on growth rate from the temporal dependence of supercooling at a prescribed melt-cooling rate

The results of determination of the supercooling dependence at the interphase boundary on the rate of growth from melt of the monocrystal Bi₄Ge₃O₁₂ in the [211] direction are presented. Determination of supercooling was based on optical pyrometer measurements of the intensity of heat emission from the interphase boundary through the growing crystal. The crystal was grown by the AHF method (axial heat flux near the front of crystallization) by cooling the AHF heater at a specified rate. The growth rate corresponding to the measured supercooling value was determined by calculations. The study has shown that the supercooling is high and varies nonlinearly with the growth rate.     

Confinement of dynamical chaos expansion in rotifer populations inhabiting heterogeneous environments: an effect of attractor size invariance

We study the impact of inter-habitat interactions in rotifer populations with intrinsically different types of dynamics: chaotic and regular. For this purpose we use a modified version of the Consensus model. The Consensus model has been shown to be realistic enough to reproduce distinguishing features of the rotifer species dynamics. Being uncoupled, a habitat with chaotic dynamics and habitats with regular oscillations of the rotifer density do not affect each other. Migration of the rotifers between the habitats leads to the invasion of chaos into neighboring habitats, that is chaotic rotifer oscillations replace regular oscillations of the rotifer density in neighboring habitats. The invasion of chaos distorts spatial borders of the rotifer oscillations synchronization clusters. We show that the invasion of chaos is spatially confined. Invariance of the attractor size under transformation of regular oscillations into chaotic ones is demonstrated to be responsible for the chaos confinement.     

Stability and limit states of elastoplastic spherical shells under static and dynamic loading

The problem of elastoplastic deformation, buckling, and postcritical behavior of spherical shells is solved using a finite element method and a cross-type explicit scheme of time integration. Stability problems for hemispherical shells under external pressure and compression between rigid plates are considered. The influence of holes and boundary conditions on shell deformation is investigated. It is shown that the calculation results are in good agreement with experimental data.     

On-line Control Model for Cost-simulation Network Projects

This paper presents a newly developed hierarchical control model for several PERT type projects being realized simultaneously. The model has two objectives: to minimize the number of control points for an on-line control at the project level, and to maximize the probability that the slowest project can meet its due date on time (company level). On-line control is carried out separately for each project in order to minimize the number of control points subject to a chance constraint, which seeks to prevent deviation from the planned trajectory. If at the control point it is anticipated that the project will not be on target subject to the chance constraint, then an emergency is called. Under emergency conditions the company level is faced with the stochastic problem of budget reassigning among the projects enabling the faster projects to help the slower ones. A numerical example is presented.