Anomalous diffusion in the dynamics of complex processes

Anomalous diffusion, process in which the mean-squared displacement of system states is a non-linear function of time, is usually identified in real stochastic processes by comparing experimental and theoretical displacements at relatively small time intervals. This paper proposes an interpolation expression for the identification of anomalous diffusion in complex signals for the cases when the dynamics of the system under study reaches a steady state (large time intervals). This interpolation expression uses the chaotic difference moment (transient structural function) of the second order as an average characteristic of displacements. A general procedure for identifying anomalous diffusion and calculating its parameters in real stochastic signals, which includes the removal of the regular (low-frequency) components from the source signal and the fitting of the chaotic part of the experimental difference moment of the second order to the interpolation expression, is presented. The procedure was applied to the analysis of the dynamics of magnetoencephalograms, blinking fluorescence of quantum dots, and X-ray emission from accreting objects. For all three applications, the interpolation was able to adequately describe the chaotic part of the experimental difference moment, which implies that anomalous diffusion manifests itself in these natural signals. The results of this study make it possible to broaden the range of complex natural processes in which anomalous diffusion can be identified. The relation between the interpolation expression and a diffusion model, which is derived in the paper, allows one to simulate the chaotic processes in the open complex systems with anomalous diffusion.Comment: 47 pages, 15 figures; Submitted to Physical Review

An approach to access urban soils’ spatial variability at the local level

There is still lack of clear information on the urban soils mainly because of their extremely high spatial variability. In this study we analyzed the specific features of urban soils’ spatial variability at the local level (64 ha plot; 126 sampling points). Four contrast urban soil sub-types were distinguished in the study area: primitive urban soils on the technogenic parent material, grey-humus soils with urbopedogenensis features, urbanozems and urban soil on the layers of sewage accumulation. Comparison between the results of regional and local analysis did not show the trend of spatial variability decrease as a result of detailed elaboration. Thus it may be concluded that high spatial variability is an integral feature of urban soils, that assumes principally different approach for their spatial analysis

A procedure for determining dexketoprofen trometamol in human plasma and its validation

Предложена и валидирована методика определения декскетопрофена трометамола в плазме крови человека методом жидкостной хромато-масс-спектрометрии (ВЭЖХ–МС/МС) с применением ибупрофена в качестве внутреннего стандарта. Оценено матричное влияние на величину отклика аналита; изучена его кратковременная и долговременная стабильность в биологической матрице и в водно-ацетонитрильном растворе, а также стабильность при замораживании и оттаивании образцов. Показано, что разбавление проб в два раза существенно не влияет на точность и прецизионность анализа. Предел обнаружения и нижний предел количественного определения составили 0.01 мкг/мл, линейный диапазон – 0.01–8.50 мкг/мл (R2 = 0.9974), общая продолжительность анализа – 3.5 мин. Внутри- и межсерийная точность находились в диапазонах 96.66–100.00% и 94.97–97.92% соответственно. Пробоподготовка, включающая жидкостно-жидкостную экстракцию этилацетатом в кислой среде, отличается простотой выполнения и экспрессностью. Разработанная методика успешно апробирована на реальных образцах плазмы крови здоровых добровольцев в рамках сравнительного