Femtosecond energy transfer between chromophores in allophycocyanin trimers

Ultrafast energy-transfer processes in allophycocyanin (APC) trimers from Mastigocladus laminosus have been examined by a femtosecond absorption technique. Isotropic absorption recovery kinetics with τ=440±30 fs were observed in APC trimers at 615 nm. In APC monomers such a fast process was not observed. The anisotropy in both samples was constant and close to 0.4 during the first few picoseconds. The results are consistent with a model of the APC trimer in which the two APC chromophores have different absorption spectra with maxima about 600 and 650 nm. The transfer of energy from the 600 nm chromophore to the 650 nm chromophore occurs in 440 fs and is dominated by the Förster dipole—dipole energy-transfer mechanism

A Quality and Cost Approach for Comparison of Small-World Networks

We propose an approach based on analysis of cost-quality tradeoffs for comparison of efficiency of various algorithms for small-world network construction. A number of both known in the literature and original algorithms for complex small-world networks construction are shortly reviewed and compared. The networks constructed on the basis of these algorithms have basic structure of 1D regular lattice with additional shortcuts providing the small-world properties. It is shown that networks proposed in this work have the best cost-quality ratio in the considered class.Comment: 27 pages, 16 figures, 1 tabl

A rationale for some directions of the development of resource territories: the complex ''meso-level'' problem

The article presents an approach to the analysis and evaluation of integrated investment projects, which consist of infrastructure facilities and industrial clusters allocated to poorly developed areas rich in natural resources. This study shows the feasibility of a public-private partnership during the construction of infrastructure facilities in order to minimize the risks and maximize the benefits. The conceptual framework of the resulting approach is associated with the ideas and principles of «impact investing» («creation of shared values») and inclusive economic development. These are increasingly used worldwide, especially to accelerate the socio-economic development of backward countries and territories. The article presents an international experience and explains the relevance of best practices in Russia. The authors identified methodological problems associated with the application of traditional methods to the evaluation of economic effects of project investing under the conditions of high uncertainty. The authors explain why it is necessary to use models and methods (real options analysis and fuzzy cognitive models) that allow researchers to directly take into account the uncertainty and project risks. The novelty of the article is the methodological tools for evaluating the socio-economic efficiency of complex projects combining the development of infrastructure and minerals. The proposed approach was used to provide a rationale for a road construction project in the Berezovsky district of the Khanty-Mansi Autonomous Okrug. The authors showed opportunities to generate a set of institutional, organizational, and financial conditions under which the implementation of the project will be attractive to both investors and government and will bring socio-economic benefits to this territory. The proposed approach and tools can be used for a socio-economic strategic decision-making process to justify infrastructure projects in resource-rich regions.The theoretical and methodological results presented in the article were obtained during the research funded by the Russian Science Foundation (Project No. 14–18–02345)

Femtosecond spectral and anisotropy study of excitation energy transfer between neighbouring α-80 and β-81 chromophores of allophycocyanin trimers

Polarization pump-probe femtosecond spectroscopy was used to investigate photoinduced optical density changes in allophycocyanin (APC) trimers at 635–690 nm after excitation with 230-fs pulses at 618 nm. The initial bleaching observed at λ < 645 nm is followed by subpicosecond absorption recovery corresponding to 430 ± 40 fs recovery kinetics measured at 615 nm with 70-fs pulses. Only the red part of the APC absorption band remains strongly bleached at 3 ps after excitation. The spectral and kinetic results can be described in terms of two different models of interaction between neighbouring α-80 and β-81 chromophores of APC trimers. According to the first one, the observed subpicosecond kinetics corresponds to relaxation between the levels of excitonically coupled, spectrally identical α-80 and β-81 chromophores. Excited state absorption to doubly excited excitonic state should in this case contribute to the measured difference spectra. According to the second one, the femtosecond excitation energy transfer in APC trimers takes place between a donor chromophore absorbing predominantly at 620 nm and an acceptor chromophore absorbing at 650 nm. The high anisotropy value observed at 615 nm during the first 1.2 ps is in good agreement with the donor-acceptor model. Anisotropy values calculated in the 635–675 nm spectral region at 3 ps after excitation are in the 0.1–0.25 range corresponding to an angle of 30°–45° between donor and acceptor transition dipole orientations. The high anisotropy obtained at 658 nm during the excitation is probably due to stimulated emission of the donor chromophore